JPH0334185B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a photomultiplier tube that photoelectrically converts weak incident light on a photocathode, multiplies the generated photoelectrons with a dynode, and collects them on an anode. The present invention relates to a photoelectron multiplier capable of detecting the incident position of light incident on a single photocathode and extracting incident position information.

(Background of the invention) A photomultiplier tube is combined with a scintillator, etc., and weak radiation is converted by the scintillator and is incident on the photocathode of the photomultiplier tube, and photoelectrons are generated on the photocathode.
Devices that detect weak radiation are known.

Photomultiplier tubes have excellent characteristics that cannot be obtained with solid-state photoelectric conversion devices.

However, since it is difficult to make the device itself compact, there is a problem in that the incident position of radiation is determined by the photocathode unit of the photomultiplier tube.

Therefore, in such a device, there is a demand to know at which position on the photocathode the pulsed light incident on a single photocathode of the photomultiplier tube is incident.

Assuming that there is a correlation between the position of a photoelectron generated by a photon incident on the photocathode and the position at which the multiplied electrons caused by the photoelectron reach the anode, if the position at which the anode arrives is known, the photon It should be possible to know the incident position to some extent.

Therefore, a photomultiplier tube with a divided anode as shown in FIG. 1 can be considered.

Net-shaped anodes 4a to 4d divided into FIG.
The top view of the figure is shown. 4e to 4h are frames that support the nets of each anode.

A transmissive photocathode 3 is formed on the inner surface of a window 2 of a vacuum-tight container 1.

A stacked dynode is provided in the space 8 between the photocathode 3 and the divided anodes 4a to 4d.

FIG. 9 shows a typical structure of a stacked dynode partially enlarged.

Figure A shows a Venetian blind type, Figure B shows a Venetian blind type triangular dynode, and Figure C shows a mesh dynode.

Photoelectrons generated from the photocathode 3 are multiplied in the dynode space 8 and accelerated in the direction of the four-divided mesh anodes 4a to 4d.

The accelerated electrons once pass through the net-like portions of the anodes 4a to 4d, collide with the final stage dynode 5, and emit secondary electrons.

The emitted secondary electrons are collected by the divided anodes 4a to 4d.

With the above-described configuration, if the outputs of the anodes 4a to 4d are individually extracted and evaluated, it should be possible to estimate which position on the photocathode 3 the light is incident on.

However, according to the inventors' study,
I haven't gotten very good results.

If the sensitivity of the photocathode 3 is uniform and the multiplication factor of the dynode is constant without changing depending on the location,
When the photocathode 3 is uniformly irradiated, the output appearing at each anode must be equal.

However, in reality, the same output is not obtained at the anodes 4a to 4d.

This means that there is sufficient non-uniformity in the sensitivity of the photocathode 3 and the multiplication factor μ of the dynode 5 etc. depending on the location.

(Object of the Invention) An object of the present invention is to provide a photoelectron multiplier capable of detecting the incident position of light incident on a single photocathode with higher accuracy and extracting incident position information.

(Structure of the Invention) In order to achieve the above object, according to the present invention, a photoelectron multiplier capable of extracting incident position information includes a vacuum-tight container, a photocathode formed on the inner side of a face plate of the container, and a photoelectron multiplier capable of extracting incident position information. The electrodes are arranged in layers along one or more planes parallel to the photocathode, and at least one layered electrode is divided into a plurality of regions,
A dynode group that multiplies photoelectrons emitted by the photocathode, an anode that captures the electrons multiplied by the dynode group, and an operating voltage that is supplied between the photocathode, the dynode group, and the anode to control the amplification of the dynode. an operating power supply device that adjusts the voltage for each divided region, and an operation power supply device that individually extracts the outputs of each of the electrodes divided into a plurality of regions of the dynode group and calculates the correlation between each output, thereby controlling the incidence of light incident on the photocathode. It consists of a calculation device that calculates the distribution of positions.

(Example) The present invention will be described in more detail below with reference to the drawings.

FIG. 3 is a front sectional view of an embodiment of a photomultiplier tube used in a photomultiplier device capable of extracting incident position information according to the present invention.

Figures 4 and 5 are B-B and C- in Figure 3.
FIG. 3 is a cross-sectional view taken along the line indicated by C.

The vacuum-tight container 20 has a cylindrical shape, and a photocathode 15 is formed on the inner surface of the upper surface (face plate 2) in FIG.

Space 21 between photocathode 15 and mesh anode 16
A transmission-type dynode with a planar, uniform, and minute distribution of transmission areas is arranged.

This embodiment uses a mesh dynode shown in FIG. 9C.

The net-like anode 16, the divided plate-like dynodes 11, 12, 13, 14, and the flat plate 17 that insulates and supports these dynodes are connected to the photocathode 1.
They are arranged in parallel in this order from the 5th side.

FIG. 4 is a diagram showing the photomultiplier tube cut along the line BB in FIG. 3.

Dynodes 11, 12, 13, 14 are photocathode 1
A circle having approximately the same area as 5 is divided into four parts in a fan shape, and 11a to 14a are holes for insulating and supporting each electrode.

FIG. 5 is a diagram showing the photomultiplier tube cut along the line CC in FIG. 3.

Holes 17a to 17d of the flat plate 17 in FIG. 5 correspond to the holes 11a to 14a, and 17e
-17h are holes for fixing spacers that insulate and support the divided dynodes.

FIG. 6 shows a signal processing circuit of an incident position detection device using a photomultiplier tube having a split type dynode as described above. In FIG. 6, a photomultiplier tube is shown as an equivalent circuit.

The operating voltage is supplied from an operating power supply device consisting of a high voltage source E ₁ , resistors R...R (50 KΩ each), and a resistance network of variable resistors VR ₁ to VR ₄ (200 KΩ).

The voltage of the photocathode 15 is the lowest, and the voltage of the dynodes in the layered dynode space 21 increases sequentially, and the potentials of the divided dynodes 11, 12, 13, and 14 can be adjusted independently by the variable resistors VR ₁ to VR ₄ , respectively. It's like this.

The anode 16 has a positive potential with respect to the photocathode 15 and each of the divided dynodes 11 to 14. Ammeters A ₁ to A ₅ are connected to each of the divided dynodes 11 to 14 and the anode 16 to measure their output currents.

With the operating voltage supplied to each part as described above, the photocathode 15 is irradiated with uniform light, and the variable resistors VR ₁ to VR ₄ are adjusted so that the currents obtained from each divided dynode 11 to 14 are equal. adjust.

When light is incident on any position on the photocathode in the device adjusted in this way, each dynode 11 to 14 receives a current of ₁ , ₂ , ₃ , _4, respectively.
Suppose that flows.

Current-voltage converted outputs V _{1 ,} V ₂ , V ₃ , and V ₄ are obtained from the ammeters A 1 to A ₄ corresponding to ₁ , ₂ , ₃ , and ₄ .

These outputs V ₁ , V ₂ , V ₃ , V ₄ are sent to amplifiers 40a to 4.
The signal is amplified at 0d, converted into a digital signal by analog-to-digital converters 41a to 41d, and temporarily stored in the memory 42.

The microcomputer 44 calculates the incident position based on this information and displays the incident position on the X/Y display 4.
Displayed on 5.

Next, an incident position calculation method using the center of gravity calculation processing method will be explained.

Due to the spatial spread of the photoelectrons emitted from the photocathode 15 and the multiplied electrons, each dynode provides an output corresponding to the position of the incident light.

The center of gravity calculation processing method is a method of determining the incident position by calculating where the center of gravity of these outputs is.

As shown in the model diagram of Fig. 7, the arrangement of each dynode is 11 (1, 1), 12 (2, 1), 13 (2,
2), 14 (1, 2).

When photoelectrons are multiplied and reach the final stage dynode, the multiplied electrons have a spatial spread f. The coordinate axes are the center lines of the space into which the dynodes are divided, as shown in FIG.

The output of the (i, j)th dynode is now Vi,
j, the center of gravity M(x, y) is given by the following equation (1).

M (x, y) = ( 〓 ⁱ 〓 ^j Vi, j・Wi, j) / ( 〓 ⁱ 〓 ^j Vi, j) ...(1) Wi, j: Weight Now, suppose that each Corresponding the dynode arrangement and the weight Wi,j, W ₁₁ = (-1, 1), W ₂₁ = (1, 1) W ₁₂ = (-1, -1), W ₂₂ = (1, -1) It can be expressed as

In this way, it is possible to know in which region the incident has occurred for each incident.

Note that the intensity of the pulsed light can be determined from the current flowing through the anode 16.

(Modifications) Various modifications can be made to the above-described embodiment device within the scope of the present invention.

When sufficient sensitivity can be obtained with a reflective divided dynode, the transmission type dynode is unnecessary.

Further, the same effect can be obtained by incorporating a microchannel plate at the position of the transmission type dynode described above to divide the final stage dynode.

It is also possible to use a Venetian blind type dynode or a Venetian blind modified triangle dynode.

(Effects of the Invention) As explained above, the incident position detection device using the photomultiplier tube according to the present invention divides the final stage dynode into a plurality of parts and adjusts the multiplication factor of each, thereby detecting the photocathode and the dynode. Sensitivity by position,
By correcting the non-uniformity of the multiplication factor and using a photomultiplier tube with an anode divided into multiple parts, it has become possible to detect the incident position with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a photomultiplier tube with its anode divided. Figure 2 is A-A in Figure 1.
FIG. FIG. 3 is a plan view showing an embodiment of a photomultiplier tube used in a photomultiplier device capable of extracting incident position information according to the present invention. FIG. 4 is a sectional view of the photomultiplier tube taken along the line BB in FIG. 3. FIG. 5 is a cross-sectional view of the photomultiplier tube taken along the line CC in FIG. 3. FIG. 6 is a block diagram showing an embodiment of a photomultiplier device capable of extracting incident position information according to the present invention, in which the photomultiplier tube is shown as an equivalent circuit. FIG. 7 is a perspective view showing a model for explaining the operation of the split type dynode. FIG. 8 is a diagram showing the weight Wi,j and the arrangement of each dynode. FIG. 9 is a partially enlarged view of a dynode showing examples of various laminated dynodes. 1... Vacuum-tight container, 2... Vacuum-tight container window, 3
...Photocathode, 4a, 4b, 4c, 4d... Divided anode, 4e to 4h... Frame of divided anode, 5... Final stage dynode, 6... Lead wire, 8... Layered dynode space, 11, 12, 13, 14 ... Split dynode, 15... Photocathode, 16... Reticular anode, 17
...Support plate supporting divided dynode, 18...Lead wire, 20...Vacuum-tight container, 21...Layered dynode space, 40...Amplifier, 41...Analog-digital converter, 42...Memory, 43...Interface, 44...Microcomputer , 45...
X/Y display.

Claims (1)

[Scope of Claims] 1. A vacuum-tight container, a photocathode formed on the inner side of a face plate of the container, electrodes arranged in layers along one or more planes parallel to the photocathode, and at least one layered electrode. The electrode is divided into a plurality of regions, including a dynode group that multiplies photoelectrons emitted from the photocathode, an anode that captures the electrons multiplied by the dynode group, and a region between the photocathode, the dynode group, and the anode. an operating power supply device that supplies an operating voltage to the dynode and adjusts the amplification degree of the dynode for each divided region; and an operating power supply device that individually extracts the outputs of the electrodes divided into a plurality of regions of the dynode group and calculates the correlation between each output. A photoelectron multiplier capable of extracting incident position information, which is comprised of an arithmetic unit that calculates the incident position of light incident on the photocathode. 2. The vacuum container is a cylindrical airtight container, the photocathode is circular, and the electrodes of the dynode group divided into multiple regions are formed by dividing a circle corresponding to the photocathode into fan shapes. A photoelectron multiplier capable of extracting incident position information according to claim 1. 3. A photoelectron multiplier device capable of extracting incident position information according to claim 2, wherein the electrodes of the dynode group divided into a plurality of regions are divided into four equal areas. 4. A photoelectron multiplier capable of extracting incident position information according to claim 1, wherein the arithmetic unit performs incident position calculation using a barycentric calculation processing method. 5. A photomultiplier device capable of extracting incident position information according to claim 1, wherein the magnitude of an event is obtained from the output of the anode. 6. The anode is a mesh-shaped anode, and the dynode group is composed of a transmission-type dynode having a planar and uniform transmission area distribution and a divided reflection-type dynode, and includes a photocathode, a transmission-type dynode, and a mesh-shaped dynode. A photomultiplier device capable of extracting incident position information according to claim 1, wherein an anode and a reflective dynode are arranged in this order. 7. The photoelectron multiplier device capable of extracting incident position information according to claim 6, wherein the transmission type dynode is a Venetian blind type, a Venetian blind modified triangle dynode, or a mesh dynode.