JPH0636035B2 - Method and apparatus for measuring the surface distribution of radionuclides emitting charged particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention broadly relates to radionuclides that emit charged particles,
The present invention relates to a system for measuring a spatial distribution on a sample surface, and more particularly, to a measurement method for precisely measuring the emission of charged particles emitted from a surface, and a surface area having a relatively large area. A device capable of providing a high-resolution digital image of the distribution of charged particle emissions over a very short exposure time.

There are several processing procedures that require a detailed measurement of the distribution of charged particle emitting radionuclides on the surface of the sample. Some such treatment procedures require the distribution to be measured over a relatively large surface area,
It can be as large as a quarter square meter, especially for large areas. An example of a treatment procedure in which the surface to be measured is thus particularly wide is, for example, the measurement of the concentration distribution of the labeling compound labeled with phosphorus-32 in the polyacrylamide gel thin film. A number of different types of methods have been employed to date to perform this type of distribution measurement, and these methods are described below.

With the method called autoradiography, high-resolution recording over a large area can be obtained at one time. However, the photographic film used in this system has a relatively low sensitivity to high energy beta emission, has limitations on the exposure area, requires additional processing steps of development and reading, and further Background is recorded due to chemical fog and natural sources of radiation. Although it has been attempted to increase the sensitivity of a photographic film by using an intensifying screen, if this is done, the spatial resolution will decrease.

Another method is to use a scanning detector. There are various types of scanning detectors, for example, gas ionization detectors, various solid-state detectors including scintillators, and the like. Some of these scanning type detectors can detect only one point at a time, and some of them can record one line or a two-dimensional area having a small area at one time. However, even when a scanning type detector capable of recording a two-dimensional area at a time is used, a relatively long time is required when a measurement target area much larger than the area of the sensitive area of the detector is detected. I cannot help but take it.

It has also been done so far to configure a segment detector by combining multiple scanning detectors.
Various types of scanning detectors have been used to construct segment detectors. However, scanning and segmentation may cause boundary effects, mechanical distortion, and image defects in the distribution of measurement results.

Yet another method is to use a detector having a large area of sensitivity. However,
High resolution solid state devices such as multi-channel plates have been found difficult to fabricate as large devices. Further, the current method using the gas ionization detector cannot obtain a high spatial resolution, and the spatial resolution is remarkably low particularly when detecting high energy β emission.

Accordingly, one of the main objects of the present invention is an apparatus and method for the direct digital measurement of the surface distribution of a radionuclide that emits charged particles, which is capable of achieving a high spatial accuracy, namely: An object of the present invention is to provide a device and a method capable of distinguishing two high-concentration points of a radionuclide that are separated from each other by only a minute distance as separate points.

Yet another object of the present invention is to enable the measurement of radionuclide distribution over a large surface area with high efficiency in detecting radiation emission and thus short exposure times. .

Yet another object of the present invention is to enable high resolution measurements of large areas of radionuclides that emit high-energy β rays, such as phosphorus-32.

Still another object of the present invention is a quantitative measurement of radioactivity of a radionuclide, which has a wide dynamic range, and therefore a low concentration point is mixed between high concentration points of radioactivity of the radionuclide. However, it is to enable quantitative measurement that can be measured.

Several types of radioactivity detectors have already been developed that make use of proportional amplification of ionization in gas. Most of the radioactivity detectors of this type are configured so that an electron generated by a primary ionization generated by an incident phenomenon is moved toward a metal wire or a conductive fiber by an electric field formed accordingly.
The primary electron approaching the metal wire or the conductive fiber violently collides with the gas atom due to the strong electric field in the vicinity of the metal wire or the conductive fiber, and knocks out more electrons from the colliding atom. Causes a controlled avalanche amplification. The electronic circuit records the charge signal obtained by this avalanche amplification. By appropriately adjusting the operating conditions, the magnitude of the amplitude of the signal is made proportional to the amount of primary ionization.

Ionization chamber type detectors for position measurement using proportional amplification in gas use various types of detection elements. One of them is a detection element in the form of a multi-line proportional grid. is there. The multi-wire proportional grid is an electrode composed of a large number of thin metal wires or conductive fibers arranged at uniform intervals. To create a position measuring chamber (ie, a position measuring ionization chamber), the grid is placed in a container filled with a suitable gas mixture and placed in a strong electric field. If an event of ionization occurs in the chamber (that is, the ionization chamber) thus created, first, a local cluster of primary electrons is generated, and subsequently, each of the primary electrons constituting this cluster is generated. However, it is drawn to the thin metal wires of the multi-wire proportional grid. If the primary electron reaches near the surface of the metal wire, the primary electron causes local avalanche amplification, resulting in a charge signal of measurable magnitude. Then, by identifying which metal thin wire the charge signal is generated from among a large number of metal thin wires forming the grid, or when a charge signal is generated in a plurality of metal thin wires,
The center position of the cluster of primary electrons generated by ionization can be measured as a one-dimensional position on the plane of the grid by calculating the barycentric position between the plurality of metal thin wires. If another grid is provided in parallel with and adjacent to the multi-wire proportional grid, the charge signal is induced on the grid by capacitive coupling with the multi-wire proportional grid. The charge signal can be obtained from Therefore, if two separate electrodes are provided adjacent to both sides of the multi-wire proportional grid, two-dimensional position measurement values can be obtained from the respective charge signals induced in those electrodes.

If a preferable example of the ionization chamber type detector for position measurement using proportional amplification in gas is given, one or a plurality of position measurement chamber parts are arranged in one gas enclosure and There are detectors configured such that the position measuring chamber section includes one multi-line proportional grid. Suitable configurations, materials of construction, mixed gas types, reading methods, and operating conditions for detectors of this configuration are already known in the art. They are US Pat. No. 377.
No. 2521, No. 3786270, and the following papers.

(1) G. Charpak, R. Bouclier, T. Bressani, J. Favie
r, and C. Zupancic, "The use of multiwire proporti
onal counters to select and localize charged parti
cles, "Nuclear Instruments and Methods 62: 262-268
(1968). (2) G. Charpak, R. Bouclier, T. Bressani, J. Favie
r, and C. Zupancic, "Some readout systems for pro
portional multiwire chambers, "Nuclear Instruments
and Methods 65: 217-220 (1968). (3) G. Charpak, D. Rahm, and H. Steiner, "Some dev
elopments in the operation of multiwire proportion
al chambers, "Nuclear Instruments and Methods 80: 1
3-34 (1970). Ionization chamber type detector for position detection using proportional amplification in gas shows high sensitivity to β emission generated by radionuclide. That is, in this type of detector, essentially all β emissions incident on the sensitive region of the detector can be counted, provided that the appropriate reading circuitry is combined. However, this type of detector does not provide high spatial resolution except in the case of detecting very low energy β emission. It is a high energy β
This is because the emission has a long range in the gas and thus draws a long ionization track along the emission route. Ionization chamber detectors (ie, multi-wire proportional chambers) that use a planar multi-wire proportional grid have It will contain a very large parallax error.

A multi-stage avalanche amplification chamber was developed as one attempt to address this problem. The multi-stage avalanche amplification chamber is a modification of the original multi-line proportional chamber with an additional gas region with a very strong electric field applied to it, compared to the original multi-line proportional grid. It is defined by additional electrodes arranged in parallel. Since a strong electric field acts on the entire area of this additional gas region, if ionization occurs everywhere in this additional gas area, avalanche amplification of the ionization is performed, and amplification is performed. The ionized substances that have passed through the electrodes, which are configured as a grid or a mesh, travel to the multi-line proportional grid and are detected in the multi-line proportional grid. By providing such an additional gas region, the chamber (ie, ionization chamber type detector) is provided with its high power provided near the side opposite to the side where the multi-wire proportional grid is located. It becomes predominantly responsive to the ionization occurring in the additional gas region under the action of a strong electric field. Therefore, if the sample is placed in the gas of the detector and the surface of the sample is placed in contact with the outer electrode of the gas region where a strong electric field is acting, the sample is placed. , Can be primarily responsive to ionization occurring in a thin layered gas region adjacent to the surface of the sample. This can reduce the parallax error.

Suitable configurations, materials of construction, mixed gas types, reading methods, and operating conditions for a multi-stage avalanche amplification chamber are described in the following articles.

(4) G. Petersen, G. Charpak, G. Melchart, and F. S
auli, "A multistep avalanche chamber as a detector
in radiochromatography imaging, "Nuclear Instrume
nts and Methods 176: 239-244 (1980). Since the multi-stage avalanche amplification chamber was developed as described above, it has a great limitation in recording β emission distribution. That is, as the energy of β emission to be detected increases, the resolution drops considerably. The reason is that as the energy of β emission increases, the position of ionization generated and detected in the thin layered high-sensitivity gas region is far from the actual point of β emission that generated ionization. This is because the probability of being far away increases. Furthermore, a multi-stage avalanche amplification chamber must be operated while maintaining a precise electric field strength control to maintain an accurate value. In other words, the multi-stage avalanche amplification chamber is susceptible to the effect of the electric field distortion caused by the electric field coming into contact with or approaching the sample surface. In addition, the signal generated by the multi-stage avalanche amplification chamber has a very wide amplitude range. The cause is that the multi-stage avalanche amplification chamber reacts to a very small number of primary electrons, and therefore the primary electrons to be reacted with The statistical fluctuation of the group is large. Furthermore, in the multi-stage avalanche amplification chamber,
The detector gas must be kept at a high purity level for stable operation, but the sample gas must be placed in the detector gas, so the detector gas may be contaminated by the sample. There is also.

A major problem in measuring the emission point position of high energy charged particle emission is that the emission path is long.
The measurement method according to the present invention uses (1) a detector capable of detecting ionization on the emission path of the charged particle emission, and (2) emission from almost the entire sample surface. (3) A separate detection element is provided to measure the coordinates of the barycentric position of the ionization at at least two points on the emission path, and (4) the emission is carried out with a straight line passing through those measured points. The calculated release direction of the route, and (5) based on the calculated release direction of the release route, (a) the measured value of the coordinate position obtained as a result of the position measurement performed at a position very close to the release generation point. To modify the coordinate position measurement so that it is closer to the exit point position on the sample surface, or (b) record only the discharges where the angle of the discharge path is within an acceptable angular range. Or (c) Zodiac As to perform modifications and acceptance criteria applied and together. As the measurement value of the emission direction, the emission angle with respect to the normal line of the sample surface is obtained. The above measurement of direction, correction of coordinate position,
The application of the acceptance criterion may be performed in only one of the two coordinate directions of the sample surface, or in both.

The apparatus according to the present invention is a radiographic imaging apparatus configured to measure the distribution of a radionuclide that emits charged particles on the surface of a sample or in the vicinity of the surface. This device is a multi-chamber type gas ionization detector. This detector operates in a counting method, records a plurality of ionization signals, obtains the barycentric position of ionization at at least two points on the emission path based on the ionized signals, and further, the measured values of the barycentric positions are measured. Based on this, the coordinate position of the emission generation point of the emission is calculated. This detector can be most easily configured when the shape of the sample surface to be detected is a flat surface.However, even if the shape of the sample surface is not a flat surface, a simple curved surface shape is used. If so, it can be configured to suit it. Also, the device according to the invention is particularly suitable for detecting high energy β emissions, but the gas pressure of the device is low and the use of low density materials in the fabrication of the device. Then, the device can be applied to detection of particle emission other than β emission and detection of low energy β emission.

The data acquisition subsystem used in the device according to the present invention is
It is a subsystem that obtains the distribution of radionuclides on the surface of the sample or in the vicinity of the surface based on the coordinates of the emission generation points of the emission of many charged particles. This data collection subsystem does the following to determine the distribution of radionuclides.
First, for each of a large number of area elements obtained by finely dividing the measurement area corresponding to the sample surface, if the emission point coordinates calculated for a certain emission are located within the boundary of a certain area element, the emission is associated with that area element. It counts as a release. A memory array, a multi-channel digital counter or the like may be used to perform this counting, and the memory array or the multi-channel digital counter may be controlled by a digital processing system. You can When they are used, each of the storage locations of the memory array or each of the channels of the digital counter is assigned to one of the area elements on the sample surface. Then, each time an emission is detected, the calculated emission point coordinates of that emission correspond to the memory location or digital location in the memory array corresponding to the area element located therein.
Increment the count value of the counter channel. However, at that time, on the condition that the emission angle of the emission is within an allowable angle range and the emission energy of the emission is within an allowable energy range,
Make the increment. After recording multiple emissions, the count values corresponding to each of the multiple area elements on the sample surface represent the respective concentration values of the radionuclide in those area elements.

In the apparatus according to the present invention, the plurality of position measuring chambers of the detector are housed in the airtight enclosure. The enclosure is also designed to perform the function of electrical insulation and shielding. This enclosure has on one side a window, which is a particularly thin outer wall. The sample is set on the outside of the sealed container, in which case the sample is set very close to the window or is set in direct contact with the window. The function of this window is to isolate the detector from the external environment while still allowing the emission from the sample to
It is to be able to enter the detector with little absorption or scattering. The window is configured to include a conductive layer, and the window should be made of a low density material with a low atomic number.

Each of the plurality of position measuring chamber parts in the detector includes two or more regions each having a relatively small thickness, and these regions are filled with the mixed gas. The boundaries of these regions are defined by electrodes arranged parallel to the surface of the sample that emits the charged particles. If the surface of the sample has a planar shape, the electrodes also have a planar shape. Among these electrodes, the electrodes (inter-region electrodes) located between the regions adjacent to each other form a parallel grid, a cross grid, or a mesh by using a large number of thin metal wires or conductive fibers. It should be configured as follows. The inter-region electrode forms an equipotential surface for forming an electric field, and at the same time, it enables electrons affected by the electric field to pass through the electrode and move from one region to another region. It was done. At this time, the electrons move in a direction perpendicular to the electrode surface.
Outermost electrode of position measuring chamber (outer electrode)
May have the same structure as the inter-region electrode, or may be made of a film, a metal foil, a multilayer sheet, or a rigid material. The outer electrode also forms an equipotential surface for forming an electric field, although the outer electrode does not have to be capable of passing electrons. To form electrode elements on the surface of such outer electrodes, print,
Means such as vapor deposition, plating, etching, or cutting may be used.

The position measuring chamber section in the detector is configured to include at least one detection region. A conventional multi-wire proportional chamber having the following structure can be used as the position measuring chamber section. The configuration is a configuration in which two detection regions are provided, the detection regions are partitioned by a multi-line proportional grid, and the outer boundaries of the detection regions are defined by respective outer electrodes. The function of these detection areas is to measure the centroid position of small ionizing clusters that occur in a part of the emission path. The measurement of the position of the center of gravity is carried out by electronically processing the charge signal obtained from the conductive element (ie the electrode element) of the respective electrodes which define the outer boundaries of the detection areas. The center of gravity between the signals generated in the plurality of electrode elements can be determined for each outer electrode directly by this electronic processing or by further performing intermediate processing thereto. The two calculated values thus obtained are 2 at the center of the charge of the ionization cluster, which is parallel to the electrode surface.
The value is proportional to each coordinate position in one coordinate direction. Further, the position of the center plane of the region in which the ionized substance is collected is the position in the third dimension corresponding to the calculated values.

Of the plurality of electrodes provided in this device, one electrode that partitions between two detection regions is a multi-line proportional grid. Further, the other plurality of electrodes constituting the position measuring chamber section have their potentials set so that the potentials thereof gradually decrease as the position moves away from the multi-line proportional grid, so that the ionizing electrons are , Move to be attracted to the multi-line proportional grid. When the multi-wire proportional grid is reached near the multi-wire proportional grid, the amplifying action of the ionized electrons occurs due to the strong electric field in the vicinity of the thin metal wires or the conductive fibers forming the multi-wire proportional grid. This causes a charge signal to be generated on the multiple elements of the multi-wire proportional grid (ie, the thin metal wires or conductive fibers that make up the multi-wire grid). Further, at least one other electrode adjacent to the multi-wire proportional grid is defined as a parallel grid, and the extending direction of the conductive elements of the parallel grid is set with respect to the extending direction of the elements of the multi-wire proportional grid. Angled (ie, not parallel), or angled with respect to the direction of extension of the element of another electrode adjacent to this multiline proportional grid. I am trying to do it. A charge signal is induced in the elements of the grid electrode adjacent to the multi-wire proportional grid by capacitive coupling. Each signal induced on the plurality of elements of the two grid-like or grid-like electrodes defining the outer boundary of the two detection areas is processed by a reading circuit. Thus, the two-dimensional center-of-gravity position of the primary ionization cluster can be measured.

In order to improve the spatial resolution as much as possible, in this device, the measurement position of the first point is set to a position as close to the emission generation point on the emission path as possible. The position-measuring chamber portion for measuring the position at the first point is designed to have a plurality of regions, and for example, five regions may be provided in the following order. .
That is, it is possible to provide a collecting region first, an amplification region behind it, a delivery region behind it, and two detection regions behind it.

A strong electric field is applied to the amplification region of the position measurement chamber part, and the strength of the electric field is such that the electrons moved in the amplification region by the electric field violently collide with the gas atoms, The strength is sufficient to generate the phenomenon of knocking out more electrons from the molecule. The amplification effect obtained by this phenomenon is of the same type as the amplification effect generated in the vicinity of the multi-line proportional grid. However, this amplification action in the amplification region is not limited to the vicinity of the electrode surface, but differs in that it occurs everywhere in the gas region which is the amplification region. The maximum amplification factor that can be obtained when the primary ionized electrons completely cross the amplification region from one side to the other side, and the stable amplification effect can be obtained also depends on the type of mixed gas. Also, although it depends on the specific structure of the position measuring chamber part, an amplification factor up to about "10000" is possible. When a certain primary electron does not completely cross the amplification region but only partially, the value of the amplification factor obtained by the primary electron depends on the thickness of the amplification region crossed by the primary electron. It changes exponentially.

The main function of the amplification region is to distinguish only the ionization occurring on one side of the amplification region from the ionization occurring in the other parts of the position measuring chamber. That is, the primary electrons that have entered the amplification region beyond the low potential side boundary of the amplification region are amplified at the maximum amplification factor of the amplification region (that is, the amplification factor obtained when the amplification region is completely crossed). However, on the other hand, the primary ionized electrons generated at a position that enters the amplification region even slightly below the boundary on the low potential side of the amplification region are amplified with a much smaller amplification factor. Then, the detection region arranged on the high potential side of the amplification region reacts with almost all of the ionized electrons generated by the amplification action. A collection region may be further added to the low potential side of the amplification region, so that the position measurement chamber portion having the amplification region can reduce the thickness of the gas in which the primary ionization electrons react. Can be defined.

The main function of the collection area is a thin layer of gas of controlled thickness, where primary ionization electron collection is performed in the gas layer to determine the position of a point on the emission path. The purpose is to provide a gas layer. However, the thickness of the region of this gas layer is made sufficiently thick so that, on average, about several primary ionizing electrons are present on the portion of the emission path that crosses this region. If the collection area is provided, the amount of ionized electrons detected will be a controlled and accurate amount, and the deformation of the detector window will not affect the electric field in the amplification area. The amplitude of the signal to be stabilized becomes stable and the spatial resolution becomes stable. The practical minimum thickness of the collection area is determined by the statistical ionization propensity of the gas used in the detector. For example, when the energy of β emission to be detected is 0.3 MeV and a general gas is used and the pressure of the gas is atmospheric pressure, the minimum thickness is about 1 mm. It is not desirable to make the collection area too thick, since it reduces the spatial resolution. A medium-strength electric field is applied to the collecting region, which causes the ionizing electrons to be pushed from this collecting region through electrodes configured as a grid or mesh into the amplification region. I am trying.

The delivery area is, so to speak, a gap between the amplification area and the detection area of the two detection areas, which is closer to the amplification area, and can have various thicknesses. This is an area that can be set arbitrarily. An electric field of medium strength, which is about the same as the electric field strength of the collecting area, is applied to the transfer area, and ionization electrons are pushed by the electric field into the detection area through the transfer area. I am trying. The delivery region electrostatically isolates the amplification region where the avalanche amplification action occurs from the detection region, and also functions to prevent the unintended secondary amplification action from occurring. Of the ionized electrons generated in the amplification region, only a part thereof flows into the delivery region, and the amount of outflow is controlled by the value of the ratio of the electric field intensity of the delivery region to the electric field intensity of the amplification region. The amount of cation flow moving from the detection region toward the amplification region is also controlled by the value of the ratio of the electric field intensity of the delivery region to the electric field intensity of the detection region.

For the second position measuring chamber section in the detector, use should be made of a conventional multi-line proportional chamber having two detection regions and dividing the detection regions by a multi-line proportional grid. You can The second position measuring chamber part may also be provided with other electrodes and regions similarly to the first position measuring chamber part. The function of the second position measuring chamber section in the detector is to measure the coordinate position of the second point on the emission path. The device of the present invention uses the information that this second point is the coordinate position to determine the emission angle of the emission path with respect to the normal of the detection surface in one or both of two coordinate directions parallel to the detection surface. It can be calculated as a corner. Furthermore,
The coordinate position obtained from the first position measurement chamber section is corrected according to a simple calculation formula,
It is a calculation formula for calculating the coordinate position of the release generation point by extending the estimated release path represented by a straight line to the sample surface. This calculation process can be easily executed at a speed practically sufficient by using an analog or digital electronic circuit. It should be noted that it is also possible to incorporate more position measuring chambers in the detector so as to obtain the coordinate positions of more points on the emission path. However, in many cases, this does not result in a significant increase in spatial resolution, despite the increased complexity.

In detectors of the type outlined above, the scattering of the emission that occurs within the detector has a large effect on the spatial resolution of the detector. This scattering means that when a charged particle passes through the gas in the chamber for position measurement or the material of the electrode, the traveling path of the charged particle is statistically stochastically bent according to a well-known physical law. Say. Due to this scattering, a large error may occur in the calculated value of the coordinate position of emission and the calculated value of the emission angle. Due to these properties, the electrode should be made as thin as possible using a material having a low density and a small atomic number.

The magnitude of the effect of scattering on spatial resolution increases sharply as the emission angle of the emission with respect to the normal to the sample surface increases, or as the emission energy of the emission decreases. The emission energy of charged particle emission from radionuclides, as is well known, is widely distributed over the energy range between zero and the maximum energy value.
Due to this distribution of energy magnitudes, some of the total emission of any type of radionuclide is low energy.
Due to the existence of the above factors, emission with a large emission angle,
A small energy release is advantageously rejected (i.e. not counted).

Since the method and apparatus of the present invention provide information about the emission angle, this information can be used to reject emissions with large emission angles. The narrower the allowable angle range, the higher the spatial resolution, but at the cost of reduced sensitivity. Since it is possible to predict what kind of response characteristics of the detector will be obtained by the angle acceptance criterion based on a physical law, the angle acceptance criterion can be optimized according to a specific application.

Even if the emission energy is different from each other,
In most cases, the amounts of the primary ionized substances generated along the emission route due to their emission do not differ so much from each other as long as their emission energy falls within a practically important emission energy range. Therefore, no useful information about the magnitude of the emitted energy can be obtained from the amplitude of the signal obtained from the detector. However, by incorporating a plate of absorbent material (absorber plate) in the detector, the detector can be adapted to the emission energy distribution of a particular type of radionuclide. As the absorptive material, a material having a small atomic number should be used in order to prevent fluorescence from being generated by high energy X-rays. Further, this absorber plate may be configured as a multilayer body in which several kinds of materials are combined, which makes it possible to further suppress the generation of fluorescence. By properly determining the threshold value of the emitted energy for passing through the absorber plate, charged particle emissions with emission energy below that threshold value cannot pass through the absorber plate, and thus In the chamber part arranged behind the absorber plate, such charged particle emission is not detected.

With the use of absorber plates, the emission through the absorber plate will be highly scattered inside the absorber plate. Therefore, the second point on the discharge path should be measured in front of the absorber plate, or
Alternatively, if it is done behind the absorber plate, it should be done as close as possible to the absorber plate. Therefore, it is preferable to adopt either of the following two methods. (1) The coordinate position of the second point should be measured in front of the absorber plate, and behind the absorber plate, a third chamber part for recording only the presence or absence of emission penetrating the absorber plate is provided. . (2) The second position measuring chamber has the same configuration as the first position measuring chamber described above, and the collecting region of the second position measuring chamber is positioned adjacent to the back of the absorber plate. To do so.

As still another method for distinguishing the emission according to the magnitude of the emitted energy, a plate made of scintillator material (scintillator plate) is provided behind the second position measuring chamber portion in the detector. There is a method in which the plate has a material composition and a thickness that absorbs all emission of energy of any magnitude as long as it is the emission generated by the radionuclide of the sample. Then, by observing the scintillator plate with a phototransducer so that the phototransducer generates an electric signal whose amplitude is proportional to the amount of light received from the scintillator plate, the amplitude of the electric signal is increased. The magnitude of the energy released can be determined from Also by this, it is possible to reject the emission whose emission energy is equal to or less than the threshold value.

When the concentration of the radionuclide is low, a large amount of background may be included in the measurement result of the distribution of the radionuclide due to a natural radiation source such as cosmic rays. Also, some background events, such as cosmic ray muons, cause detector responses that are indistinguishable from detector responses to high energy beta emissions. Therefore, it may be desired to suppress the background.

The following methods are available to prevent background counting. It consists of an optional multi-line proportional counter or scintillation counter behind the absorber plate, which is any component of sufficient thickness so that no radiation from the sample penetrates it. Combination with a counter
One set or a plurality of sets are arranged. Regarding the arrangement position, (1) The sample is sandwiched between the detector and the main constituent elements of the detector, and (2) the detector. It may be arranged on the same side as the main constituent elements of (3), and (3) it may be arranged on both of these positions. The reject counter of this configuration (ie the absorber plate and counter combination) does not need to measure position,
It only needs to generate a signal when the emission of radiation penetrates the reject counter. And if the signal is generated, only for a short time immediately after it is generated,
Prevent recording of data from the position measuring chamber section.

The detector configured as described above is connected to the simultaneity control circuit so that the measurement value of the detector is processed only when the series of events listed below occur. I need to put it. The series of events includes (1) a signal of an appropriate magnitude is generated on the detection electrode of the chamber for first position measurement of the detector, and is also appropriate on the detection electrode of the chamber for second position measurement. Large signals are generated, and the time interval between the times when the signals are generated is within a predetermined short time (typically 1 microsecond or less).
(2) When using the above-mentioned counter for distinguishing the emission by the amount of emitted energy, a sufficiently large signal is generated from the counter during the same time interval as above. And (3) when the above reject counter is provided, no signal is generated from the reject count during the same time interval as above, and these are the three events. . Concurrency control circuits of this kind are well known in the art. In addition, in this simultaneity control circuit, a plurality of chamber units and a plurality of counters provided in the detector are configured in the form of
When the mechanical structures or operating conditions are different from each other, it is necessary to allow for the allowable amount of response time of the individual chambers and counters.

The detector configured as described above further includes a reading circuit for converting a charge signal obtained from the electrode of the detector into a coordinate signal which is a signal proportional to the coordinate position, and a coordinate obtained from the reading circuit. It is necessary to connect to a signal processing circuit for converting the signal into the calculated coordinate position of the emission generation point. An example of such a reading circuit is a circuit for obtaining a coordinate signal as follows. That is, first,
A plurality of signals from a plurality of conductive elements of an electrode that defines the detection area are aligned with a coordinate direction in a plane of the electrode and orthogonal to the extending direction of the electrode element. In addition, a weight value proportional to the position of those elements is multiplied. Then, the weighted total value, which is the total value of these signals after this weighting, and the simple total value, which is the total value of those signals that have not been weighted, are calculated, and the weighted total value is calculated as the simple total value. Find the quotient divided by. The quotient thus obtained is in the direction of extension of the element of the ionization cluster detected on a plane parallel to the plane of the electrode, which lies in the detection region where the electrode defines the boundary. It represents the coordinate position of the center of gravity in the coordinate direction orthogonal to the direction. If the shape of the sample surface is not a flat shape but a curved shape, it is necessary to multiply the quotient by a correction coefficient. Further, one of the above-mentioned signal processing circuits is required for each of the coordinate directions for which the direction measurement value is to be obtained, out of the two coordinate directions on the sample surface. Then, the signal processing circuit corresponding to each coordinate direction generates the calculated discharge generation point in the coordinate direction by combining the two position measurement values on the discharge path obtained with respect to the coordinate direction.

FIG. 1 is a view showing, in a cross section of the detector, an arrangement mode of electrodes and a typical arrangement position of a part of a sample in the flat panel detector according to the present invention. The chamber includes a position measuring chamber section consisting of five regions, a conventional multi-line proportional chamber section arranged behind it, and an absorber plate, which is an optional component, arranged behind it. And another multi-line proportional chamber section. This figure is only a schematic diagram, the enclosure, the electrode support structure,
The detailed structure of the device is omitted in the drawings.

FIG. 2 is a cross-sectional view of a detector showing another arrangement mode of electrodes and a typical arrangement position of a part of a sample in the flat panel detector according to the present invention. The type detector is
A position measuring chamber part consisting of five regions, an absorber plate arranged behind it, and a second part consisting of five regions.
And a position measuring chamber section. This figure is only a schematic diagram, and the encapsulation container, the electrode support structure, and the detailed structure of the device are all omitted in the drawing.

FIG. 3 shows still another arrangement mode of electrodes in the flat panel detector according to the present invention and a disposition position of a part of a typical sample,
It is the figure which showed with the cross section of the detector, the flat type detector of this figure has the chamber section for the position measurement which consists of 5 territory, the multi line proportional chamber section of the former general constitution which is arranged behind it. , And a scintillator plate with a phototransducer placed behind it. This drawing is only a schematic diagram, and the supporting structure for the enclosure, the electrode, and the detailed structure of the device are not shown.

FIG. 4 is a schematic view showing an example of a typical emission path in a cross section of the detector, and shows the measurement performed by the detector according to the present invention and the coordinate position of the emission generation point performed according to the principle of the present invention. It is a figure for demonstrating the calculation method and the error which arises as a result of scattering of an emission path.

FIG. 5A is a block diagram of a signal processing circuit that executes a calculation process necessary for calculating the emission generation point coordinate position according to the present invention.

Figures 5B and 5C are block diagrams of suitable read circuits for use in combination with the circuit of Figure 5A.

FIG. 6 shows a structure in which the detector shown in FIG. 2 is housed in an enclosure and a reject counter, which is an optional component, is provided both inside and outside the enclosure. FIG. 3 is a diagram showing, in a cross section of the apparatus, an arrangement mode of constituent elements and an arrangement mode of a typical sample plane in the apparatus according to the present invention. In this figure, the detailed structure of the device is omitted.

FIG. 7 is a block diagram showing the main components of a data acquisition system incorporating a detector and signal processing circuit constructed in accordance with the present invention.

FIGS. 1, 2, and 3 show a plurality of planar shapes of an apparatus configured to measure the distribution of radionuclides that emit charged particles on the surface of a planar sample or in the vicinity of the surface. It is the figure which showed 3 types of arrangement | positioning modes of a detection electrode by sectional drawing. In any of the arrangements shown in the drawings, there is provided a first position measuring chamber portion having five regions for measuring one point as close as possible to the emission generation point on the emission path of the charged particle emission, and the second point. And a second position measuring chamber section for measuring The detector shown is particularly suitable for the detection of high-energy beta emissions, for example beta-emission from strontium-90 with a maximum emission energy of 0.54 MeV and phosphorus-32 with a maximum energy of 1.72 MeV. It is suitable for the detection of β-emission and the like. The electrode surface of the flat electrode of this detector is designed to extend parallel to the sample surface, and its size should be approximately the same as or slightly larger than the sample surface. I am doing it. However, the practical size may be up to about 30 × 50 cm.

In FIG. 1, a radionuclide that emits charged particles is distributed in a planar sample 1.
It is arranged adjacent to the outer surface of the window 2 of the gas enclosure. The window 2 also functions as an outer electrode of the collecting region 3. The window 2 should be a member made of a thin and strong material that is stretched under strong tension, that is impermeable to various gases and water vapors, is conductive, and has a small atomic number. . The window 2 can be made of a coated material, for example a thickness of 50
A sheet material or the like having a 5 micron aluminum layer deposited on the outer surface of a micron polyester film and a colloidal graphite layer coated on the inner surface can be used. In this detector, the mixed gas is filled in the whole area from the collection area 3 to the detection area 16. The mixed gas has a small electron adhering property, and an amplification effect is generated by the parallel electrode plates. The composition is such that, for example, a mixture of 3 to 5% of acetone or propane in argon can be used. For stable operation,
It is important to keep the purity of this mixed gas high.
Oxygen, water vapor, or a solvent having a high electronegativity such as chlorine-substituted hydrocarbon must have a low concentration, and normally the concentration of such a gas needs to be 1 ppm or less. Note that the specific design values illustrated above are for the case where the detector is operated with the pressure of the mixed gas at atmospheric pressure. By operating at higher pressures to detect very high energy charged particles, and conversely at lower pressures to detect very low energy charged particles, It is possible to improve the spatial resolution, but inevitably this makes the structure of the gas enclosure more complicated.

Inside the detector, the window portion 2 of the gas filled container and the five planar electrodes 21, 22, 25, 26, 27 define a chamber portion having five regions, This chamber portion is for measuring the coordinate position of one point as close as possible to the surface of the sample 1 on the discharge path of the charged particles. Of the five planar electrodes, the potential of the multi-line proportional grid electrode 26 is set to be the highest, and the other electrodes are set so that their potentials become lower as they move away from the multi-line proportional grid electrode 26. The potential is set. The thickness of the collecting region 3 is sufficient to generate a few primary ionization clusters in a part of the average one emission path that crosses the collecting region 3, and specifically, Is about 1
It has a thickness of mm. The electric field strength of the collecting region 3 is set to a medium strength, specifically, about 50 to 100 V / mm / atm.
And

The electrode 21 and the electrode 22 are electrodes that define respective boundaries on both sides of the amplification region 4. A strong electric field is applied to the amplification region 4, and specifically about 500 to 8
Since the electric field strength is 00 V / mm / atm, the electrodes 21 and 22 tend to attract each other and bend. In order to make this deflection of the electrodes 21, 22 as small as possible, they have to be stretched with a very strong tension. The thickness of the amplification region 4 can be, for example, about 3 to 8 mm. The thinner the thickness, the higher the accuracy of measurement of the spatial position, but instead, it becomes necessary to maintain the thickness uniformity of the amplification region 4 more strictly. Electrodes 21, 2
The metal wires or conductive fibers constituting the two should be closely spaced, that is, the pitch thereof should be finer than about 1/10 of the thickness of the amplification region 4. This is to minimize variations in electric field strength depending on locations, and also to suppress the response of the detector from being spatially quantized as much as possible. The metal wires or conductive fibers that compose the electrode must have a diameter large enough so that they do not become a source of corona discharge, and for the same reason, The surface should be as smooth as possible. Specifically, as a constituent material of the electrodes 21 and 22, a stainless steel wire or a beryllium copper wire having a diameter of 50 to 100 microns can be used. However, from the standpoint of avoiding the scattering of charged particle emission as much as possible,
It is advantageous to use a material having a low density and a small atomic number. For example, it is preferable to use a polyaramid fiber coated with a conductive material.

As described above, the electrode 26 is a multi-line proportional grid electrode and is an anode. Then, the grid electrode 26 that is this anode
25 and 27 function as cathodes for
Is. The grid of the anode 26 is made of tungsten wire or stainless steel wire having a diameter of 20 to 30 μm,
They are arranged side by side at a pitch of ~ 2.5 mm.
On the other hand, the electrodes 25 and 27, which are cathodes, are formed by arranging fine metal wires having a diameter of 50 to 150 microns at a pitch of 1 to 3 mm. The distance between the anode 26 and the cathode 25 or the cathode 27 can be about 4-8 mm. The smaller this spacing, the better the overall spatial resolution, but at the cost of more rigorous uniformity of this spacing.
Further, if the pitch of the thin metal wires forming the anode 26 is made fine, the amplitude of the obtained signal will be significantly reduced. In order to avoid scattering of charged particle emission as much as possible, it is advantageous to use a material having a low density and a small atomic number as the material of the cathodes 25 and 27. The electric field strength required for the detection regions 7 and 8 between the anode 26 and the cathodes 25 and 27 is about 300 to 500 V / mm / atm, though it depends on the diameter and pitch of the thin metal wires constituting the anode 26. I am trying.

A delivery area 5 is provided between the amplification area 4 and the detection area 7. The thickness of the transfer area 5 and the electric field strength differ depending on the design purpose of the detector. If the thickness of the delivery area 5 is increased, the isolation degree between the amplification area 4 and the detection area 7 can be increased, so that the operation stability can be improved.
Furthermore, since the lateral diffusion amount of electrons generated in the delivery region 5 is also increased, the degree to which the response of the detector is spatially quantized can be suppressed to a low level. On the other hand, a disadvantage is that the measurement error due to scattering increases as the thickness of the delivery area 5 increases. Regarding the electric field strength, the weaker the electric field strength in the transfer area 5, the lower the ratio of the electrons transferred through the electrode 22 and the higher the degree of isolation between the amplification area 4 and the detection area 7. This reduces the signal amplitude, so
The original accuracy of position measurement may be deteriorated. The thickness of the delivery area 5 can be, for example, 3 to 15 mm,
The electric field strength can be set to, for example, 20 to 200 V / mm / atm.

In the configuration of the detector shown in FIG. 1, the second position measuring chamber section is composed of a detection area 11 and a detection area 12, and these detection areas 11 and 12 are electrodes 31 and 31 which are cathodes. 33 and the multi-line proportional grid electrode 32 which is an anode. These detection areas 11
And 12 have the same structure and operating characteristics as the detection area 7
And 8 and have the same structure or operating characteristics.
The absorber plate 9 and the detection areas 15 and 16 may or may not be provided in the detector, ie they are optional components. If they are provided, the detection areas 15 and 16 and the electrodes 35, 36 and 37 that define them are the same as the detection areas 11 and 1.
2 and the electrodes 31, 32, 33 defining them
The structure and operating characteristics are almost the same as those described above. It should be noted that the electrode 27 and the electrode 31 can also be used as a single electrode, and in such a case, the positional information is output to the electrodes 25, 26,
It will be necessary to get from 32 and 33.

The detector shown in FIG. 1 is provided with at least two sets of components of the position measuring multi-wire proportional chamber section, that is, the electrodes 25, 26 and 27 and the electrode 3.
1, 32, and 33. If the electrons generated due to the event causing ionization reach the vicinity of any one of the plurality of thin metal wires or conductive fibers of the multi-line proportional grid electrodes 26 to 32 as the anode,
Since the operating conditions described above are adjusted, a local amplification action occurs at a position close to the surface of the thin metal wire. As a result, a negative charge signal is generated on the metal wires of the anodes 26 to 32 in the active state, and an electrode of the cathode which is induced by the negative charge and is close to the generation position of the negative charge signal. A positive charge signal is generated in the element (that is, the thin metal wire or the like forming the cathode). The form of the cathode is a split-type electrode so that the position can be measured. That is, when linear coordinates are used as coordinates for position measurement, the individual electrode elements are
A single thin metal wire, or a thin metal wire group in which several thin metal wires are combined, or a single conductive strip, and a plurality of electrode elements each configured as such, It is possible to have an electrode configuration in which an array is formed by arranging parallel to each other at a uniform interval so as to form a planar shape. When curved coordinates or non-linear coordinates are used as coordinates for position measurement, an electrode configuration different from this may be adopted. The magnitude of the positive charge signal induced on the individual electrode elements of the cathode decreases sharply as the position of that electrode element moves away from the position on the anode 26 where the amplification effect occurs.

In order to obtain the position of the center of gravity of the charges by processing the signals obtained from a plurality of electrode elements each of which is composed of a thin metal wire (or having another structure), and thereby the position of the center of the primary ionization cluster, an electronic circuit is used. Is used for the reading circuit. There are several types of read circuits that can be used for this purpose. In this regard, the detector shown in FIG. 1 can adopt a method that can obtain a simple and accurate result by using a tapped lumped constant electromagnetic delay line. This is a method of directly connecting each of the plurality of taps to each metal thin wire of the grid electrode or to a group of several metal thin wires. The time difference between the signal peaks at both ends of this electromagnetic delay line is
It is proportional to the position of the center of gravity of the charge. In addition, as another method, there is a method of using an analog or digital center of gravity calculating circuit. In this method, the position of each electrode element is responded to with respect to each signal emitted from a plurality of electrode elements. The centroid calculation circuit performs an operation of dividing the summed value after weighting by the simple summed value of the signals that have not been weighted. It is to be noted that a plurality of electrode elements corresponding to the coordinate direction and one reading circuit are required for each of the coordinate directions of the adopted coordinates.

The detector shown in FIG. 1 is provided with an absorber 9 and a multi-line proportional chamber section composed of electrodes 35, 36 and 37 as optional components. Providing the detector with these components provides for counting and non-counting emissions.
In order to distinguish by the magnitude of its emitted energy,
This is a case in which the detector has a threshold value set to the magnitude of the emitted energy. The material and thickness of the absorber 9 are selected so that substantially all of the charged particles whose energy is equal to or less than a specific size can be stopped. It is preferable to prevent the generation of X-ray fluorescence due to high-energy X-rays by using a material having a small atomic number, such as carbon, as the material of the absorber 9, because the X-ray fluorescence can be prevented. If it occurs, the X-ray fluorescence may be detected by any part of this detector. The optional components, electrodes 35, 36, and 37, need not be provided with a read circuit for position measurement. If a signal is generated on the multi-wire proportional grid 36, it can be interpreted as evidence that the emission of charged particles has penetrated the absorber 9.

The structure of the detector shown in FIG. 2 is a modification of the structure of the detector shown in FIG. 1 in the entire structure including arbitrary constituent elements therein. The configuration of the detector shown in FIG. 2 is similar to that of the configuration shown in FIG. 1, and the window electrode 2 and the other electrodes 21, 22, 25, 2
It includes a first position measuring chamber portion having a region 3, a region 4, a region 5, a region 7, and a region 8 defined by 6, 27. These regions and electrodes have the same structure and the same characteristics as the corresponding regions and electrodes designated by the same reference numerals in the configuration of FIG. The absorber 50 performs the same function as the absorber 9 of FIG. 1, except that, unlike the absorber 9, the absorber 50 itself is made of a conductive material or is made of a conductive material. By laminating them together, they also function as one of the electrodes defining the collecting region 41.

The detector configuration of FIG. 2 is defined by the absorber electrode 50 and the other electrodes 51, 52, 55, 56, 57,
A second area including five areas, a collection area 41, an amplification area 42, a delivery area 43, a detection area 45, and a detection area 46.
It includes a position measuring chamber section. This second position measuring chamber part is provided with regions 3, 4, 5, 7, 8 and a window electrode 2 and other electrodes 21, 22, 25, 26 and 27 for first position measuring chamber. Compared with the first part, the second position measuring chamber part has the same structure and the same structure as the first position measuring chamber part except that the absorber electrode 50 is used instead of the window part electrode 2. It has operating characteristics. The second position-measuring chamber section in the detector arrangement of FIG. 2 responds only to the emission penetrating the absorber 50. That is, with respect to the emission through the absorber 50, this second
The position measuring chamber section measures the position of ionization generated at a point as close as possible to the point where the emission has penetrated through the absorber 50 and jumped out, and the measured position is the first position on the emission path regarding the emission. It is provided as a two-point position. Second
The detector configuration shown in the figure further includes additional optional components for suppressing background radiation, which are scintillator plates 62-64.
And the transducers 62a to 64 attached to it
The combination of a and a is provided in only one of them or in both of them. Furthermore, the scintillator plates 62 to 64,
The detectors of FIG. 2 may be separated from other components by thick absorbers 61 to 63 which are also optional components. In the above, the scintillator
When a signal is detected from either or both of the plates 62 and 64, the other components of the detector of FIG. 2 (ie, the first position measuring chamber section or the second position measuring chamber section).
Do not record the signal emitted from the position measuring chamber).

The structure of the detector shown in FIG. 3 should be considered as another modified structure from the structure of the detector shown in FIG. 1 in the entire structure including arbitrary constituent elements therein. . The structure of the detector of FIG. 3 is similar to that of FIG. 1, and the window electrode 2 and the other electrodes 21, 22, 2
It includes a first position measuring chamber section consisting of a region 3, a region 4, a region 5, a region 7 and a region 8 defined by 5, 26 and 27. These regions and electrodes have the same structure and the same characteristics as the corresponding regions and electrodes designated by the same reference numerals in the configuration of FIG. The detector arrangement of FIG. 3 includes a second position measuring chamber section consisting of detection areas 45 and 46 defined by electrodes 31, 32 and 33. These regions and electrodes have the same structure and the same characteristics as the corresponding regions and electrodes designated by the same reference numerals in the configuration of FIG. The scintillator plate 77 is thick enough to absorb any emission from any type of radionuclide, and the signal emitted by the phototransducer 78 of this scintillator plate 77 is , Represents the magnitude of the energy of the radiation absorbed by the scintillator plate 77.
Therefore, by using this signal, it is possible to prevent counting for the emission of which the amount of the emitted energy is out of the allowable range.

In the configuration of the detector of FIGS. 1 and 3, 2 on the emission path
The respective measurement planes in the detector for measuring the positions of the respective ones are one substantially in the middle of the collecting region 3 and the other one is the electrode plane of the multi-wire proportional grid electrode 32. Further, in the configuration of the detector shown in FIG.
The respective measurement planes in the detector for measuring the positions of the two points are one substantially the central plane of the collecting area 3 and the other the substantially central plane of the collecting area 41. However, when determining the position of the plane approximately in the center of the collection area, the thickness of the area that actually functions as the collection area (effective thickness of the collection area) is adjacent to the collection area. It is necessary to keep in mind that it extends into the amplification region. This entry distance is approximately equal to the quotient of the thickness of the amplification region divided by the natural logarithm of the amplification gain coefficient of the amplification region for primary electrons that traverse the amplification region completely.

FIG. 4 is an explanatory view for explaining the measuring method executed in the flat panel detector constructed according to the present invention. This figure shows a cross section of the detector, and the sample surface is a flat surface 10.
The measurement of the positions of the two points located above and on the discharge path is carried out on the plane 13 and the plane 14, respectively. Here, it is assumed that the emission occurs from the point 1 in the figure, and the coordinate position of this generation point 1 is u. It is assumed that the emission generated at the point 1 travels in the detector while being bent due to scattering and follows the emission path 20. Position measurement is performed on the discharge path 20 at a point 17 on the measurement plane 13 and at a point 6 on the measurement plane 14, respectively.
It is assumed that the coordinate position measured at the point 17 is a and the coordinate position measured at the point 6 is b (these coordinate positions a and b are measured from the same reference edge as the coordinate position u). . From these two coordinate positions a and b, the straight line discharge path 23 is obtained as the calculated discharge path, and the coordinate position of the point where this straight line discharge path 23 intersects the sample surface 10 is represented by v. The distance from the sample surface 10 to the measurement plane 13 measured along its normal line and the distance to the measurement plane 14 are C and D, respectively. In the above, by correcting the amount of deviation from the coordinate position a to the coordinate position v measured at the point 17,
The formula for calculating the value of the coordinate position v is as follows.

v = a− (b−a) C / (D−C) When recording each release, for the value of v coordinate calculated according to this equation, in addition to the two coordinate directions of the coordinates of the sample surface, The effectiveness may be evaluated in one or both directions. The validity evaluation of the calculated value may be performed by a dedicated signal processing circuit or may be performed by a circuit in the digital data processing device. As is apparent from FIG. 4, the emission illustrated in the figure is accompanied by an error of (v−u) due to scattering occurring in the detector, and the error due to this scattering is caused by the position. It will be superimposed on the error inherent in the measurement. If the specific constituent material of a specific specific detector and its specific shape specifications are known, the distribution of the calculation error due to scattering can be predicted based on well-known physical laws. it can. The magnitude of the error due to scattering increases sharply because the direction of emission is at a large angle to the normal to the sample surface, and also
The energy of emission increases sharply as it becomes smaller.

Therefore, by rejecting (that is, not counting) either or both of the emission having a large emission angle with respect to the normal to the sample surface and the emission having a small emission energy, the sensitivity is improved. The spatial resolution can be improved at the cost of some. Regarding the magnitude of the emitted energy, the absorber 9 shown in FIG.
It is sufficient to include the absorbers 50 shown in the figure so that these absorbers can screen the emission according to the magnitude of the emitted energy, and can count only the emission having the emitted energy larger than a predetermined threshold value. To The phototransducer 78 of FIG. 3 can also be used for this purpose, that is, the amplitude of the signal transmitted from the phototransducer 78 can be used to set a threshold for the magnitude of the emitted energy as well. You can Regarding the emission angle, the difference value (ba) between the two coordinate values obtained by measurement is the emission angle of the emission from the sample surface with respect to the normal to the sample surface, as shown in FIG. It takes advantage of being proportional to the tangent of.
When the surface of the sample has a curved shape, the amount (b-a) may be multiplied by an appropriate correction coefficient according to the specific shape of the surface.
Then, by comparing the amount (b−a) or the amount obtained by multiplying it by an appropriate correction coefficient with a predetermined limit value, it is possible to reject the emission that makes a large angle with respect to the normal line. it can.

FIG. 5A is a block diagram of an electronic circuit that performs the process of calculating a coordinate position and the process of setting a threshold for the angle of the emission path in accordance with the method of the present invention. The circuit shown in FIG. 5A is a circuit that executes these processes in one of two coordinate directions. The digital position measurements required as inputs to this circuit can also be generated by the read circuit shown in FIG. 5B, and
It can also be generated by the read circuit shown in FIG. 5C.

The reading circuit shown in FIG. 5B is a circuit for reading the coordinate position in one coordinate direction from one position measuring chamber section. This circuit is of a system using a tapped lumped constant delay line. It is a thing. The individual conductor elements of one planar electrode are each connected as an input 301 to this delay line 302 in a straight line. Further, both ends of this delay line are connected to the timing circuit 305. The output 306 of this timing circuit 305 is the position measurement signal.

The reading circuit shown in FIG. 5C is a circuit for reading the coordinate position in one coordinate direction from one position measuring chamber section, and is of a method of obtaining the center of gravity by calculation processing. An amplifier group 311 is provided with the individual conductor elements of one planar electrode as input 310 respectively.
Connected to. A series of output signals sent from this amplifier group 310 is directly supplied to one adder 312 and the weighting network 3 to another adder 314.
It is supplied via 13. The adder 312, to which the series of output signals is directly supplied, produces as output a simple sum value which is the sum of the signals unweighted. On the other hand, the adder 314, to which a series of output signals is supplied via the weighting network 313, weights each of these output signals in proportion to the position of the conductor element which sent the output signal. A weighted sum value, which is the sum value after being applied, is generated as an output. The divider 315 produces the quotient of the weighted sum divided by the simple sum. The output 317 from the divider 315 is a signal proportional to the position of the center of gravity. It is necessary to input the position measurement values a and b to the input units 94 and 95, and these position measurement values a and b correspond to the measurement values a and b shown in FIG. Also, the input unit 9
Reference numeral 6 denotes an input unit for inputting a constant value proportional to C / (D-C), and the distance of C and the distance of D are as shown in FIG. The value of this constant is held in the register 108 if input.

In FIG. 5A, the subtractor 110 receives the measured value a and the measured value b as its inputs, and generates the difference value (b−a) between them as the output. Multiplier 11
1 is the difference value (b−a) as its input and C /
It receives a constant proportional to (D-C) and produces a product value of them as an output. The subtractor 112 is
It receives as input its value of this product and the measured value a and produces as output 115 the value of the difference between them. This output 115 is the signal shown in FIG. 4 which is proportional to the calculated coordinate position v of the emission occurrence point.

In FIG. 5A, the difference value (ba) generated by the subtractor 110 is also used as one input of the comparator 117. The other input of the comparator 117 is supplied from the register 109, and the register 109 holds the value received from the input unit 97. The value received from the input unit 97 means that when the value of (b−a) of a certain release is larger than the value, the angle of the release route of the release is too large with respect to the normal to the sample surface. It is a limit value corresponding to the value of (ba) that is not acceptable. The comparator 117 produces a signal at its output 118 when the difference value (b−a) is smaller than its limit value. This is a signal indicating that the emission angle of the emission is within the allowable range.

The circuit of FIG. 5A can be implemented using a digital integrated circuit that performs static operation, clock operation, or program operation. If such a digital integrated circuit is used, the measured value a, the measured value b, the constant C / (D-C), and the limiting value for limiting the emission angle are digitized and coded. It must be provided to the circuit in display form. It is also possible to implement the circuit of FIG. 5A using an analog circuit equivalent to that type of digital circuit. In the case of using an analog circuit, it is necessary to supply each of the above input values to the circuit in the form of an analog voltage signal or an analog current signal.

FIG. 6 is a diagram showing the overall configuration of a detector including a gas filled container, a reading circuit, and a reject counter which is an optional component. Sample 1 is the main enclosure 13
It is arranged in contact with the window portion 0 of 0. Main enclosure 130
2 accommodates two position measuring chamber parts having the configuration shown in FIG. 2, that is, a first position measuring chamber part 10 composed of five regions, and an absorber plate 15 behind it. A second position measuring chamber portion 19 which is also composed of five regions is arranged behind it. The signal cables 121 and 122 read the signals from the respective position measuring electrodes of the two position measuring chambers through the rear wall of the detector and are stored in the rear enclosure 123 as an electronic reading. Passed to circuits 125 and 126.

In FIG. 6, in the main enclosure 130, a thick absorber 71, which is an arbitrary component, and a multi-line proportional chamber are provided at positions behind the two position measuring chambers 10 and 19. The multi-line proportional chamber section 62 has the same structure as the multi-line proportional chamber section composed of the electrodes 35, 36 and 37 shown in FIG. The absorber 71, which is an optional component, is made thick enough to stop all the emission from the sample 1, so that the multi-wire proportional chamber section 62 includes cosmic rays and the like. It is made to respond only to background radiation. On the side opposite to the detector with the sample 1 interposed therebetween, a separate enclosure container 70, a thick absorber 71, and a multi-line proportional chamber section 72, which are all optional components, are provided.
The multi-line proportional chamber section 72 has the same configuration as the multi-line proportional chamber section 62. The multi-wire proportional chamber section 72 also responds only to background radiation. These two multi-line proportional chamber parts 62 and 72
Both function as reject counters, and the function of these optional reject counters is to emit reject signals when background radiation such as cosmic rays enters. is there. The position measuring chambers 10, 1 of this detector
Among the signals emitted from 9, the signals emitted within a very short time after the reject signal is emitted are ignored. With a reject count like this,
Almost all background due to radiation present in nature need not be recorded, so that even the distribution of very weak emissions from the sample can be recorded.

FIG. 7 is a diagram showing the main components of a data extraction system incorporating the device and method of the present invention. Detector 8
1 is configured according to FIG. 1, FIG. 2, or FIG. 3 and according to FIG. The detector 81 is connected to the high-voltage power supply 84 and the gas supply source 85, and the operating conditions of the detector 81 are established by these. The reading circuit 87 processes the charge signal supplied from the electrode element of the position measuring chamber section, and generates a signal proportional to the coordinate measurement value of the position where ionization occurs. The value of this signal, that is, the position measurement value, is input to the signal processing circuit 88 shown in FIG. 5A in order to obtain the coordinate position of the emission occurrence point on the sample surface in each coordinate direction. The coordinate output value generated by the signal processing circuit 88, signals from other detection elements (detection elements for detecting the magnitude of the emitted energy), and the angle comparison output value of the signal processing circuit 88 are Is input to the concurrency control circuit 89,
The concurrency control circuit 89 triggers the data acquisition processor 90 to read the calculated coordinates of the emission point from the signal processing circuit 88 when the two emission path angles associated with the emission are both within acceptable limits. Let

The data acquisition processor 90 may also be configured to control the operation of the position measuring chamber section by reading the signal emitted from the position measuring chamber section and controlling the voltage on the electrodes. The data acquisition processor 90 is further used by the signal processing circuit 88 to determine the magnitude of the predetermined signal level, the predetermined length of time, and the limiting angle magnitude for emission at a large angle to the normal to the sample surface. And a predetermined range of emitted energy.

The data collection processor 90 calculates the allowed count as
It is accumulated in the data collection memory 91. The data acquisition memory 91 may be in the form of a multi-channel digital counter 91A, or may be any general type of memory device. The data collection processor 90 further records and analyzes the calculated coordinate position of the emission occurrence point of the emission jumping from the surface of the sample, and displays the result of the analysis on the display 92. Displayed on the display 92 is, for example, a distribution map of the coordinate positions created by the data collection processor 90, that is, an image or the like.

[Brief description of drawings]

1, 2, and 3 are cross-sectional views showing the arrangement of electrodes and the arrangement position of a sample in the detector according to the present invention, and FIG. 4 is the emission performed according to the principle of the present invention. FIG. 5A is an explanatory diagram showing a method of calculating the origin point coordinate position and an error generated as a result of scattering of the emission path, and FIG. 5A is a block diagram of a signal processing circuit for calculating the emission origin point coordinate position according to the present invention. 5B and 5C are block diagrams of a suitable read circuit for use in combination with the circuit of FIG. 5A, and FIG. 6 shows the detector shown in FIG. 2 housed in an enclosure. A cross-sectional view showing the arrangement of the components and the arrangement of a typical sample plane in the device according to the present invention configured to include a reject counter both inside and outside the enclosure, and , FIG. 7 shows detection constructed in accordance with the present invention. And is a block diagram showing the main components of incorporating data acquisition system signal processing circuit. 1 ... Sample, 2 ... Window part 3 ... Collection area, 4 ... Amplification area 5 ... Delivery area 7, 8, 11, 12, 15, 16 ... Detection area 21, 22, 25-27, 31 ~ 33, 35-37 ...
Electrode 9 ... Absorber

Claims (40)

[Claims] 1. An apparatus for measuring a two-dimensional distribution of a radionuclide that emits charged particles on a surface of a planar sample or a portion in the vicinity of the surface, comprising: (a) a gas-filled container having a window, A material in which a window is arranged adjacent to the sample, and the window can penetrate the window with almost no absorption or scattering of emission of charged particles incident on the window. A gas filled container having a composition and a thickness, and (b) (i) a chamber for first position measurement arranged in the gas filled container so that the first position measurement can be performed. ,
The first position measurement is a position measurement for measuring, in two coordinate directions, a position in the first plane of an ionization signal generated by a charged particle emission passing through a first plane parallel to the sample, Further, a first position measuring chamber part having a form in which the first plane is positioned close to the surface of the sample, and (ii) a second position measuring chamber part in the gas sealing container, which is separated from the window part. A second position measuring chamber arranged for position measurement, wherein the second position measurement is performed by measuring the ionization signal generated by the charged particle emission passing through a second plane parallel to the sample. A detector including a second position measuring chamber part, which is a position measurement for measuring a position in the second plane in two coordinate directions; (c) the first position measuring chamber part and the second position measuring Specified in the chamber for use The measurement positions of the ionization signals generated within the time interval are compared and contrasted, the coordinates of the intersection point where the straight line passing through these two measurement positions intersects the surface of the sample are calculated, and the calculated position of the coordinates is taken as the calculated emission generation point Further, it is determined whether or not the value of the difference between the two measurement positions exceeds a limit value that is a value corresponding to the calculated discharge path with the maximum exit angle with respect to the first plane and the second plane. And a circuit means. 2. The size of the first position measuring chamber part and the size of the second position measuring chamber part are set to have a size substantially the same as the size of the surface of the sample. An apparatus according to claim 1, characterized in that: 3. The first position measuring chamber section and the second position measuring chamber section are each a multi-line gas proportional chamber section, and the multi-line gas proportional chamber section includes two detection regions. Each of the two detection regions is a gas region, and the two detection regions are defined by a planar electrode on the outer boundary of each of the two detection regions, and a further plane is provided between the detection regions. Are separated by a planar electrode, and each of the planar electrodes is arranged in parallel to the surface of the sample, and the planar electrode partitions between the two detection regions. The planar electrode is configured as a metal wire or a grid of conductive fibers, and in the two detection regions, the primary ionizing electrons are the metal wires due to the strong electric field formed by the planar electrode. Or the conductive fibers are moved toward the grid to cause secondary amplification of electrons in the vicinity of the thin metal wires or the conductive fibers, and further, the two detection regions of the planar electrode. The one or two planar electrodes that define the outer boundary of each of the electrodes generate a plurality of charge signals having different values depending on the position, and the read circuit is based on the charge signals. 2. The apparatus according to claim 1, wherein the barycentric position of ionization is calculated in one or two coordinate directions of the plane of the grid of metal wires or conductive fibers. 4. The first position measuring chamber section uses proportional amplification of ionization in gas, and includes a plurality of gas regions, and the plurality of gas regions are The outer boundary is defined by a planar electrode, and the gas regions are separated from each other by further respective planar electrodes, each of which is directed to the surface of the sample. Are arranged in parallel,
Of the planar electrodes, by configuring the planar electrode partitioning between the two gas regions of the plurality of gas regions as a mesh or grid, electrons can be separated from one gas region to another. The plurality of gas regions are arranged in order from the side closer to the sample, and (a) the gas region closest to the sample, the sample of the emission track of the charged particle emission. A collecting region for collecting primary ionizing electrons from a short track portion close to the surface of the inside of the collecting region, due to an electric field formed by a planar electrode defining the boundary of the collecting region. A collection region in which the primary ionization electrons are moved in a direction away from the sample; and (b) a gas region following the collection region, the primary ionization ions collected in the collection region. An electron from the sample due to the strong electric field formed by the planar electrodes defining the boundaries of the amplification region, which is the amplification region for the amplification of the child. The secondary amplification of electrons is induced everywhere in the gas region which is the amplification region while moving in the direction away from each other, and the secondary amplification of the electron is a unit in which the electrons cross the amplification region. An amplification region having an amplification rate per thickness that is substantially constant, and (c) a gas region subsequent to the amplification region, the amplification region and a gas region subsequent to the gas region. A delivery area for isolating the space, and in the delivery area,
A transfer region in which electrons are moved in a direction away from the sample due to an electric field formed by a planar electrode defining the boundary of the transfer region; and (d) next to the transfer region. Which is a gas region following the above, is a detection electrode for detecting ionization and measuring the position of the ionization, and a flat electrode partitioning the two detection regions is connected to a metal wire or a conductive wire. Configured as a grid of natural fibers, and within these two detection areas,
Due to the strong electric field formed by the plane electrodes that define the outer boundaries of the detection areas and the plane electrodes that divide the detection areas from each other, the electrons are made of metal wires or conductive fibers. It moves toward the grid so that further secondary electron amplification occurs in the vicinity of the metal wire or the conductive fiber, and further defines the outer boundary of the two detection regions of the planar electrode. The two planar electrodes that are formed are arranged to generate a plurality of charge signals having different values depending on the position, and the reading circuit is based on these charge signals and the reading circuit The apparatus according to claim 1, further comprising: two detection regions configured to calculate the position of the center of gravity of ionization in two coordinate directions of the plane of the grid. 5. The second position measuring chamber section includes two detection regions, each of the two detection regions having an outer boundary defined by a planar electrode, and the detection regions. The two electrodes are partitioned from each other by another planar electrode, and each of the planar electrodes is arranged in parallel to the surface of the sample. The planar electrodes partitioning between each other are configured as a grid of metal wires or conductive fibers, and within the two detection areas, due to the strong electric field formed by the planar electrodes. The primary ionized electrons move toward the metal thin wire or the grid of conductive fibers to cause secondary amplification of electrons in the vicinity of the metal thin wire or conductive fiber. One or two planar electrodes of the planar electrodes in the detection area generate a plurality of charge signals having different values depending on the position, and a reading circuit based on the charge signals. Is one or two of the planes of said grid of metal wires or conductive fibers
The apparatus according to claim 1, wherein the barycentric position of ionization in one coordinate direction is calculated. 6. The detector has the second position measuring chamber part and an absorber plate behind the second position measuring chamber part, and a third chamber part that reacts to ionization, and the absorber plate has a predetermined size. Has a material composition and thickness selected to absorb charged particle emissions having emission energies less than the threshold value and to transmit most of the charged particle emission having emission energies greater than the threshold value. The third chamber portion that reacts with the two detection regions includes two detection regions, each of the two detection regions having an outer boundary defined by a planar electrode, and the detection regions between the detection regions. It is divided by another planar electrode, and each of the planar electrodes is arranged in parallel to the surface of the sample, and the two of the planar electrodes are detected. The planar electrode partitioning the regions is configured as a metal thin wire or a grid of conductive fibers. Due to the strong electric field formed by the planar electrode in the two detection areas. In, the primary ionization electrons are moved toward the grid of the metal wire or the conductive fiber, secondary amplification of electrons occurs in the vicinity of the metal wire or the conductive fiber, further,
One of the planar electrodes in the two detection regions is adapted to generate a charge signal, and the read circuit emits the charged particles through the absorber plate based on the charge signal. 6. The apparatus according to claim 5, wherein it is determined whether or not is present. 7. The detector has a plate made of a solid scintillator material behind the second position measuring chamber section and a plate behind the second position measuring chamber, and the plate made of the solid scintillator material comprises:
The solid scintillator material is composed of a material composition and a thickness that absorbs any charged particle emission having any size of emission energy as long as the charged particle emission is generated by the radionuclide in the sample. The plate produces an optical signal when activated by the ionizing radiation, the phototransducer converting the optical signal into an electrical signal, the read circuit based on the amplitude of the electrical signal. The solid scintillator material plate is adapted to determine the energy of the charged particle emission absorbed, thereby allowing only emission having an energy within a predetermined energy range. The device according to claim 1 or 5. 8. The detector has an absorber plate immediately in front of the second position measuring chamber part, and the absorber plate has charged particles having an emission energy smaller than a predetermined threshold value. The material composition and thickness are selected to absorb the emission and to transmit most of the charged particle emission having an emission energy greater than the threshold value, and further wherein the second position measuring chamber section comprises a gas Adapted to utilize proportional amplification of ionization therein and including a plurality of gas regions, the plurality of gas regions having their outer boundaries defined by planar electrodes and The gas regions are separated from each other by further respective planar electrodes, each of which is arranged parallel to the surface of the sample,
Of the planar electrodes, by configuring the planar electrode partitioning between the two gas regions of the plurality of gas regions as a mesh or grid, electrons can be separated from one gas region to another. The plurality of gas regions are arranged in order from the side closer to the sample, and (a) the gas region closest to the sample, the sample of the emission track of the charged particle emission. A collecting region for collecting primary ionizing electrons from a short track portion close to the surface of the inside of the collecting region, due to an electric field formed by a planar electrode defining the boundary of the collecting region. The primary ionizing electrons are moved in a direction away from the sample, and the absorber plate is used as a planar electrode on the side of the collection region close to the surface of the sample. A collecting region, and (b) a gas region following the collecting region, which is an amplifying region for amplifying the primary ionizing electrons collected in the collecting region, and in the amplifying region, the amplifying region Electrons move away from the sample due to the strong electric field created by the planar electrodes that define the boundaries of the region, and at the same time the electrons are scattered throughout the gas region, which is the amplification region. The secondary amplification of the electrons is induced, and the secondary amplification of the electrons is performed as an amplification in which the amplification factor per unit thickness of the electrons traversing the amplification region is substantially constant, and (c ) A delivery region for isolating the amplification region and a gas region subsequent to this gas region, which is a gas region subsequent to the amplification region, in the delivery region,
A transfer region in which electrons are moved in a direction away from the sample due to an electric field formed by a planar electrode defining the boundary of the transfer region; and (d) next to the transfer region. Which is a gas region following the above, is a detection electrode for detecting ionization and measuring the position of the ionization, and a flat electrode partitioning the two detection regions is connected to a metal wire or a conductive wire. Configured as a grid of natural fibers, and within these two detection areas,
Due to the strong electric field formed by the plane electrodes that define the outer boundaries of the detection areas and the plane electrodes that divide the detection areas from each other, the electrons are made of metal wires or conductive fibers. It moves toward the grid so that further secondary electron amplification occurs in the vicinity of the metal wire or the conductive fiber, and further defines the outer boundary of the two detection regions of the planar electrode. The one or two planar electrodes that are configured to generate a plurality of charge signals having different values depending on the position, and the reading circuit is configured so that the reading circuit can use the metal thin wire or the conductive wire based on the charge signals. A two detection area for calculating the position of the center of gravity of the ionization in one or two coordinate directions of the plane of the grid of the natural fibers, and The apparatus according to item 1, item 3, or item 4. 9. The circuit means comprises the position measuring chamber portion of any one of the position measuring chamber portions.
A read circuit for determining a one-dimensional position of the charge center of gravity is used in one or both of the two dimension directions, and the read circuit includes a plurality of taps that define a boundary of the detection area. A tapped lumped constant electromagnetic delay line directly connected to the plurality of conductive elements of the electrode and electronic timing circuit means for measuring the time difference between respective signal peaks at both ends of the delay line. The time difference is in a plane located in the detection region parallel to the electrodes defining the boundary of the detection region, and the coordinate direction is the extending direction of the plurality of conductive elements. 5. The coordinate position of the center of gravity of the cluster of the detected ionizations in the coordinate orthogonal to the coordinate position is represented.
Or the apparatus according to item 5. 10. The circuit means for determining a one-dimensional position of the center of gravity of charge in one or both of the two dimensional directions of any one of the position measuring chambers of the position measuring chambers. A read circuit means is used, which is derived from a plurality of conductive elements of a single electrode defining the boundary of the detection area to determine its one-dimensional charge centroid location. Each signal is multiplied by a weight value proportional to the position of the conductive elements in the coordinates in the plane of the electrode and whose coordinate direction is orthogonal to the extending direction of the plurality of conductive elements. Then, the values of the signals thus weighted are summed to obtain a weighted sum, while on the other hand the values of the signals unweighted are summed to give a simple sum. And further dividing the weighted sum by the simple sum, the resulting output being parallel to the electrodes defining the boundaries of the detection area. The coordinate position of the center of gravity of the cluster of detected ionizations in a plane lying in the plane and whose coordinate direction is perpendicular to the extending direction of the plurality of conductive elements. An apparatus according to any one of claims 1, 3, 4, or 5, characterized in that 11. The circuit means, with respect to one or both of two dimensional directions of the second position measuring chamber section,
A read circuit is used for determining the one-dimensional position of the charge center of gravity, the read circuit directly connecting a plurality of taps to a plurality of conductive elements of a single electrode defining the boundary of the detection area. A connected lumped constant electromagnetic delay line and an electronic timing circuit for measuring the time difference between the respective signal peaks at both ends of the delay line, the time difference being the detection region Detected in a plane lying in the detection area parallel to the electrodes defining the boundary, the coordinate direction of which is at right angles to the extending direction of the plurality of conductive elements. 9. The apparatus according to claim 8, wherein the coordinate position of the center of gravity of the ionized cluster is represented. 12. The circuit means, with respect to one or both of two dimensional directions of the second position measuring chamber section,
A read circuit means is provided for determining a one-dimensional position of the charge center of gravity, and the read circuit means defines a boundary of the detection area for determining the one-dimensional position of the charge center of gravity. The respective signals obtained from the plurality of conductive elements of the electrodes are given a signal of the conductive elements in the plane of the electrodes, the coordinate direction of which is at right angles to the direction of extension of the plurality of conductive elements. Multiply by a weight value proportional to the position, and add the values of these signals after weighting in this way to obtain a weighted sum value, while, on the other hand, add the values of those signals without weighting and simply A total value is calculated, and further, the weighted total value is divided by the simple total value, and an output obtained as a result of this division is applied to the electrodes defining the boundary of the detection region. In perpendicular coordinates relative to addition the coordinate direction be in a plane located in parallel detection region extending directions of the plurality of conductive elements,
The present invention is characterized in that the coordinate position of the center of gravity of the detected ionization cluster is represented.
The device according to the item. 13. The detector comprises one or more multi-line counters utilizing proportional amplification of ionization in a gas, the multi-line counter being adjacent to the sample.
And a position on the opposite side of the second position measuring chamber part and a position on the opposite side of the sample, which is adjacent to the second position measuring chamber part. A multi-line counter has a countable region parallel to or substantially coextensive with the surface of the sample, or larger,
A signal emitted by the multi-line counter indicates the occurrence of an event of background radiation and prevents the signals from the first and second position measuring chambers from being recorded when the event occurs. A device according to claim 1, characterized in that 14. The multi-line counter includes an absorber plate of material composition and thickness capable of stopping all of the charged particle emission from the sample, the absorber plate comprising the multi-line counter. 14. The apparatus according to claim 13, wherein the apparatus is arranged on the sample side of. 15. The detector comprises one or more scintillation counters, the scintillation counters being adjacent to the sample and opposite the first and second position measuring chamber sections. Position and the second
A solid state which is arranged at least at one of the position adjacent to the position measuring chamber and opposite to the sample, the scintillation counter generating an optical signal when activated by radiation. A scintillator material plate is included such that a phototransducer converts the optical signal into an electrical signal, the scintillation counter having a countable region parallel to the surface of the sample. A signal emitted by the scintillation counter that is substantially coextensive with or larger than the surface of the sample indicates the occurrence of the event of background emission, and when the event is occurring. The first and second
The device according to claim 1, characterized in that it is adapted to prevent the recording of signals from the position measuring chamber section. 16. The scintillation counter includes an absorber plate of material composition and thickness capable of stopping all of the charged particle emission from the sample,
16. Apparatus according to claim 15, characterized in that the absorber plate is arranged on the sample side of the scintillation counter. 17. The circuit means comprises a control device for controlling whether or not to record information obtained from the first and second position measuring chamber parts, and The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the signal level from the second position measuring chamber section rises above a predetermined level is within a predetermined time interval, In addition, when the value obtained from the measurement position does not exceed the limit value corresponding to the calculated discharge path of the maximum discharge angle, the control device displays information obtained from the first and second position measurement chambers. A device according to claim 1, characterized in that it is adapted to record. 18. The circuit means comprises a control device for controlling whether or not to record information obtained from the first and second position measuring chamber parts, and The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the signal level from the second position measuring chamber section rises above a predetermined level is within a predetermined time interval, In addition, the value obtained from the measurement position does not exceed the limit value corresponding to the calculated discharge path of the maximum discharge angle, and the signal from the third chamber portion that reacts to ionization is within the predetermined energy range. The control device is adapted to record the information obtained from the first and second position measuring chambers when it is indicated that a discharge having a certain energy has occurred. Device range sixth claim of seeking. 19. The circuit means comprises a control device for controlling whether or not to record information obtained from the first and second position measuring chamber parts, and The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the signal level from the second position measuring chamber section rises above the predetermined level is within a predetermined time interval, In addition, the value obtained from the measurement position does not exceed the limit value corresponding to the calculated emission path of the maximum emission angle, and the signal from the phototransducer has an energy within a predetermined energy range. If it means that something happened,
8. Apparatus according to claim 7, characterized in that the control device is adapted to record the information obtained from the first and second position measuring chambers. 20. The circuit means comprises data sampling processor means connected to the first and second position measuring chamber sections and the controller, and the data sampling processor means comprises the first and second data sampling processor means. By reading a signal from the two-position measuring chamber section and controlling the operation of the first and second position-measuring chamber sections by controlling the electrode voltage of the position-measuring chamber section, A distribution that is controlled by setting a level, the predetermined time interval, and the limit value corresponding to the calculated emission path of the maximum emission angle, and that represents the emission coordinates of the emission of radiation from the sample surface. 18. Device according to claim 17, characterized in that a diagram or image is generated, recorded or analyzed or displayed on a display. 21. The circuit means comprises data sampling processor means connected to the first and second position measuring chamber sections and the controller, the data sampling processor means comprising the first and second data sampling processor means. By reading a signal from the two-position measuring chamber section and controlling the operation of the first and second position-measuring chamber sections by controlling the electrode voltage of the position-measuring chamber section, It is controlled by setting a level, the predetermined time interval, the limit value corresponding to the calculated discharge path of the maximum discharge angle, and the predetermined energy range of the discharge energy, and A distribution map or image representing the emission coordinates of the emission of radiation is generated, recorded or analyzed or displayed on a display. Patent system ranges paragraph 18, wherein claims to. 22. The circuit means comprises a data sampling processor means connected to the first and second position measuring chamber sections and the control device, and the data sampling processor means comprises the first and second data sampling processor means. By reading a signal from the two-position measuring chamber section and controlling the operation of the first and second position-measuring chamber sections by controlling the electrode voltage of the position-measuring chamber section, It is controlled by setting a level, the predetermined time interval, the limit value corresponding to the calculated discharge path of the maximum discharge angle, and the predetermined energy range of the discharge energy, and A distribution map or image representing the emission coordinates of the emission of radiation is generated, recorded or analyzed or displayed on a display. Device range paragraph 19, wherein claims to. 23. A flat object, which is a measuring object for measuring a distribution of radionuclides emitting charged particles, using a detector provided with a first ionization detecting element and one or more further ionization detecting elements. Or a method for determining the position of a radionuclide that emits charged particles in a curved sample surface or in the vicinity of the sample surface, (a) a distribution measurement target of the sample surface substantially parallel to the sample surface Measuring the position of the center of gravity of ionization corresponding to a short path portion of the emission path close to the emission generation point using the first ionization detection element having a sensitivity area substantially coextensive with the area. And (b) the one or more further ionization detections having a sensitivity region substantially parallel to the sample surface and having substantially the same extent as a distribution measurement target region of the sample surface. Measuring the position of the center of gravity of ionization corresponding to a short path portion of the discharge path away from the emission generation point using the output element, (c) each coordinate position obtained from the plurality of ionization detection elements Using coordinate position associating means to associate
And a step of calculating the emission generation point and the emission direction of the charged particle emission. 24. The coordinate position associating means, with respect to one or both of the two dimensional directions of the sample surface, the position measurement value in the dimensional direction obtained from the first ionization detecting element and the further ionization detection. The value of the difference between the position measurement value in the dimensional direction obtained from the element, calculates the value of the coordinate position difference, further, the value of the coordinate position difference,
Between the value of the distance between the sample surface that is the object of distribution measurement and the measurement surface of the first ionization detection element, and between the sample surface that is the object of distribution measurement and the measurement surface of the further ionization detection element At least one of (a) the calculated coordinate value of the emission point and (b) the tangent value of the calculated emission angle of the emission point should be calculated based on the distance value of (A) The calculated value of the coordinate position of the emission occurrence point is calculated by using a straight line passing through each position obtained from each of the position measurement values, and this calculated value is a distribution measurement target. The quotient of the distance between the sample surface and the measurement surface of the first ionization detection element divided by the value of the distance between the measurement surface of the first ionization detection element and the measurement surface of the further ionization detection element. The product of a certain distance ratio multiplied by the value of the coordinate position difference If the sample surface has a shape other than a plane shape, a value obtained by multiplying the value of this product by a correction coefficient corresponding to the shape is the value of the coordinate position obtained from the first ionization detection element. (B) The tangent value of the calculated value of the ejection angle of discharge is calculated by using a straight line passing through each position obtained from each of the position measurement values, and the calculated value is A value of a ratio of the value of the coordinate position difference to a value of the distance between the measurement surface of the first ionization detection element and the measurement surface of the further ionization detection element, or a value proportional to the ratio value, or If the surface of the sample is a shape other than the planar shape, this value is further multiplied by a correction coefficient corresponding to the shape to obtain a value, whereby only the emission having the emission angle within the allowable emission angle range is obtained. But As it will be und were to apply a limit to the count of the discharge, the measurement method of Claims paragraph 23, wherein a. 25. The material for preventing the passage of the charged particle emission when the emission energy of the charged particle emission emitted from the surface of the sample whose distribution is to be measured is equal to or less than a predetermined limit value. The absorber has a composition and a thickness, and the absorber has an absorption region substantially parallel to the sample surface and having substantially the same extent as a distribution measurement target region of the sample surface. The absorber is arranged at a position distant from the sample surface whose distribution is to be measured, and the absorber is between two ionization detection elements of the ionization detection elements. By using the absorber, ionization is detected by the ionization detection element located on the opposite side of the sample surface whose distribution is to be measured by using the absorber. Only released emissions Method of measuring such, the claims paragraph 23, wherein it has to apply a limit to the count of the release is. 26. The detector is capable of completely absorbing charged particles emitted from the surface of the sample regardless of their energy levels, and measuring the energy levels thereof. A thickness energy measuring ionization detecting element, the energy measuring ionization detecting element being substantially parallel to the sample surface and substantially coextensive with a distribution measurement target region of the sample surface. And the energy-measuring ionization detection element is located farther from the sample surface than any of the ionization detection elements, thereby allowing an acceptable emission energy range. 24. Claim 23, characterized in that a limit is placed on the count of emissions so that only those with the emission energy within are counted. Method of measurement. 27. The coordinate position associating means includes a multi-channel digital counter or memory array, and the calculating step uses the multi-channel digital counter or memory array. Including an image generating step of generating a digital image of the distribution of the radionuclide on the sample surface, wherein the image generating step associates a count value with each of the area elements of the sample surface, and When recording the emission of an ionization detection element, if the calculated coordinate position of the emission generation point of the emission is located inside the boundary of a certain area element, if the emission angle is limited, The emission energy is conditioned on the condition that the emission angle of emission is determined to be within the allowable emission angle range. A count value corresponding to the area element is incremented on condition that the emission energy of the emission is determined to be within an allowable emission energy range when measured. The range 23rd, 24th, 25th,
Alternatively, the measuring method described in Item 26. 28. The detector has a multi-line gas proportional chamber section as any one of the ionization detection elements, the multi-line gas proportional chamber section including two detection regions. And the two detection areas are each gas areas, and the two detection areas are
The outer boundary of each of the electrodes is defined by electrodes, and the detection areas are separated from each other by another electrode so that the electrodes extend along one curved or planar surface. Each of the electrodes is arranged in parallel to the surface of the sample, and the electrode partitioning the two detection regions from each other is a metal wire or a conductive wire. Configured as a grid of conductive fibers, in the two detection areas primary ionizing electrons move towards the metal wire or the grid of conductive fibers due to the strong electric field created by the electrodes. The secondary amplification of electrons is generated in the vicinity of the metal thin wire or the conductive fiber, and one of the electrodes in the detection area is different depending on the position. A plurality of charge signals having different values are generated, and based on these charge signals, the reading circuit calculates the position of the center of gravity of ionization in one coordinate direction of the plane of the grid of metal wires or conductive fibers. The measuring method according to claim 23, characterized in that 29. The first ionization detection element and the first ionization detection element.
At least one of a plurality of further ionization detection elements includes an amplification region, and the multi-line gas proportional chamber portion is used with the amplification region to provide a primary entry into the amplification region from a side closer to the sample. Amplification of electrons is performed, the amplification region is a gas region bounded by a plurality of electrodes, and the electrodes extend along a curved surface or a plane surface. , The electrodes are each arranged parallel to the surface of the sample, and in the amplification region, due to the strong electric field formed by the electrodes, electrons are directed away from the sample. As the electron moves, the secondary amplification of electrons is induced everywhere in the gas region which is the amplification region, and the secondary amplification of the electrons is such that the electrons cross the amplification region. The amplification factor per unit thickness is performed as a substantially constant amplification, and among the electrodes that define the boundary of the amplification region, it is far from the sample in the amplification region and close to the multi-line gas proportional chamber section. Of the electrodes defining the boundary of the multi-line gas proportional chamber section and the electrode defining the boundary of the multi-line gas proportional chamber section on the side closer to the amplification area of the multi-line gas proportional chamber section. The electrodes formed are configured as a mesh or grid to allow the transfer of electrons from the amplification region into the multi-line gas proportional chamber section. Measuring method according to item 28. 30. The first ionization detection element and the first ionization detection element.
At least one of said one or more further ionization detection elements comprises a transfer area, said multi-line gas proportional chamber section and said amplification area being separated in order to isolate said multi-line gas proportional chamber section from said amplification area. For use with a transfer area, the transfer area defines a boundary between the multi-line gas proportional chamber section and an electrode on the transfer area side among the electrodes that define the boundary of the amplification area. A gas region whose boundary is defined by the electrode on the delivery region side of the electrodes, and in the delivery region, formed by an electrode that defines the border of the delivery region, 3. An electric field much weaker than the electric field of the amplification region so that the electrons move away from the amplification region toward the multi-line gas proportional chamber section. Measurement method claim wherein. 31. The first ionization detection element and the first ionization detection element.
At least one of the one or more further ionization detection elements comprises a collecting region, the amplification for collecting primary ionizing electrons from a short track portion of the emission track of the charged particle emission close to the surface of the sample. An area is used with the collection area, the collection area being adjacent to the amplification area and on the sample side of the amplification area, the collection area being bounded by a plurality of electrodes. Of the electrodes, the electrode that defines the boundary of the collecting region on the amplification region side is the electrode that defines the boundary of the amplification region on the collection region side. On the other hand, the electrode defining the boundary of the collection area on the sample side is yet another electrode, and within the collection area is formed by the electrodes defining the boundary of the collection area. The amplification area The electric field is much weaker than the electric field of the electron, and the electrons are moved in the direction away from the sample toward the amplification region, and further, the boundary of the amplification region on the side of the collection region is defined. The electrodes are configured as a mesh or grid, whereby
30. The measuring method according to claim 29, wherein electrons are allowed to move from the collecting region into the amplifying region. 32. The detector comprises one or more multi-line counters utilizing proportional amplification of ionization in a gas, the multi-line counter being adjacent to the sample. And a position on the opposite side, adjacent to the ionization detecting element located at the backmost of the ionization detecting elements, and a position on the opposite side to the sample, which are arranged in at least one position, The multi-line counter is
The countable region is parallel to the surface of the sample and is substantially coextensive with or larger than the surface of the sample, and the signal emitted by the multiline counter is the background radiation. 24. The occurrence of the event is displayed, and the signal from the ionization detection element is prevented from being recorded when the event is occurring.
Method described in section. 33. The multi-line counter includes an absorber plate of material composition and thickness capable of stopping all of the charged particle emission from the sample, the absorber plate comprising the multi-line counter. 33. The method according to claim 32, characterized in that it is arranged on the sample side of. 34. The detector comprises one or more scintillation counters, the scintillation counters being positioned adjacent to the sample opposite the ionization detection element and the ionization counter. The scintillation counter is activated by radiation, the scintillation counter being located at at least one of a position opposite to the sample and adjacent to a rearmost ionization detection element. Contains a plate made of fixed scintillator material that produces an optical signal when
A phototransducer converts the optical signal into an electric signal, and the scintillation counter has a countable area parallel to the surface of the sample and substantially the same as the surface of the sample. With or without spread, the signal emitted by the scintillation counter is indicative of the occurrence of an event of background radiation, and the signal from the ionization detection element is recorded when the event occurs. 24. A method according to claim 23, characterized in that it is adapted to prevent 35. The scintillation counter includes an absorber plate of material composition and thickness capable of stopping all of the charged particle emission from the sample,
35. Method according to claim 34, characterized in that the absorber plate is arranged on the sample side of the scintillation counter. 36. The coordinate position associating means has a control device for controlling whether or not information obtained from the ionization detecting element is recorded, and one of the ionization detecting elements is selected from the ionization detecting elements. The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the level of the signal from another one of the ionization detection elements rises above a predetermined level is The control device is obtained from the ionization detection element when the emission direction of the charged particle emission does not exceed the limiting angle value corresponding to the calculated emission path of the maximum emission angle. 24. A method according to claim 23, characterized in that the information is recorded. 37. The coordinate position associating means has a control device for controlling whether or not to record information obtained from the ionization detecting element, and one of the ionization detecting elements is selected from the ionization detecting elements. The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the level of the signal from another one of the ionization detection elements rises above a predetermined level is predetermined. Within the time interval, the emission direction of the charged particle emission does not exceed the limiting angle value corresponding to the calculated emission path of the maximum emission angle, and the farthest from the sample of the ionization detection element. A signal from an ionization detection element located at a position indicating that an emission having an energy within a predetermined energy range has occurred. Control device, Claims 25 11. The method according to claim, characterized in that it is constituted such that it is record information obtained from the ionization detector element. 38. The coordinate position associating means has a control device for controlling whether or not to record information obtained from the ionization detecting element, and one of the ionization detecting elements is selected from the ionization detecting elements. The time interval between the time when the signal level of the signal rises above a predetermined level and the time when the level of the signal from another one of the ionization detection elements rises above a predetermined level is predetermined. Within the time interval, and the emission direction of the charged particle emission does not exceed the limit angle value corresponding to the calculated emission path of the maximum emission angle, and the signal from the energy measurement ionization detection element, The control device is obtained from the ionization detection element when it indicates that an emission having an energy within a predetermined energy range has occurred. Claims 26 11. The method according to claim, characterized in that it is constituted such that it is recorded broadcast. 39. The coordinate position associating means has a data collection processor connected to the ionization detection element and the control device, and the data collection processor comprises:
Reading a signal from the ionization detection element, and
The operation of the ionization detecting element is controlled by controlling the electrode voltage of the ionization detecting element, and the predetermined signal level, the predetermined time interval, and the maximum emission angle are calculated. And the data acquisition processor generates, or records, a distribution map or image representing the calculated emission points of the charged particle emission from the sample surface. 37. The method according to claim 36, characterized by being analyzed or displayed on a display. 40. The coordinate position associating means has a data collection processor connected to the ionization detection element and the control device, and the data collection processor comprises:
Reading a signal from the ionization detection element, and
The operation of the ionization detection element is controlled by controlling the electrode voltage of the ionization detection element, and the predetermined signal level, the predetermined time interval, and the maximum emission angle calculated by the limiting angle corresponding to the emission path. Control by setting a value and the predetermined energy range of the emitted energy, and wherein the data acquisition processor further comprises a distribution diagram representing the calculated emission point of the charged particle emission from the sample surface. 39. The method according to claim 37 or 38, characterized in that the image is generated, recorded, analyzed or displayed on a display.