Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
  • G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/16—Measuring radiation intensity
  • G01T1/17—Circuit arrangements not adapted to a particular type of detector
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N2015/0038—Investigating nanoparticles
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/16—Measuring radiation intensity
  • G01T1/26—Measuring radiation intensity with resistance detectors

Definitions

• the present invention relates to a method of detecting elementary particles such as protons, ions, electrons, neutrons, photons or the like. in a detector, wherein an electric field is applied to the detector and wherein upon the passage of a particle through the detector, a charge pulse is generated in the detector and each charge pulse is subsequently converted into an electrical signal.
• the present invention further relates to an apparatus for detecting elementary particles, such as protons, ions, electrons, neutrons, photons or the like, with a detector for generating a charge pulse in the detector as a particle passes therethrough, to which Detector an electric field is applied.
• detection usually takes place in that at high frequencies or signal rates, an integration of a plurality of signals takes place, wherein after amplification In the case of such an integration, essentially a current signal is displayed or recorded as a function of the number or multiplicity of detected particles. Furthermore, detection of individual particles can usually only be carried out at comparatively low frequencies or signal rates, taking into account the possibilities of resolving individual pulses or signals in such detectors.
• diamond detectors For example, for such methods or apparatus for detecting elementary particles, the use of diamond detectors is known, wherein during normal operation of such a diamond detector, an electrical potential is applied to electrodes of the detector, whereby an electric field is created inside the detector.
• Elementary particles to be detected which strike the detector or pass through it. occur, ionize the detector material, wherein in the electric field, a force acts on such ionized charge carriers in the interior of the detector material. These ionized 'charge carriers move in this electric field to one of the electrodes.
• Diamond is a semiconductor, so that both positively charged holes and negatively charged electrons are ionized, with the electrons and holes moving at different but comparable velocities.
• the charge carriers move to the positive or negative electrode, charge pulses thus generated subsequently being converted into an electrical signal and usually correspondingly amplified and correspondingly processed in an evaluation electronics for detecting the signal rates or count rates.
• polarization charges also arise over time due to the irradiation or impingement of the detector material, it being understood that these are, for example, free charge carriers under the electrodes, polarization charges in the material of the detector, free charge carriers at grain boundaries, impurities, etc. acts.
• Such polarization charges cause an additional electric field inside the detector or detector material, which is usually called a polarization field.
• Such a polarization field counteracts the externally applied electric field, which leads to a reduction of the electric field in the detector or diamond material in an at least microscopic and optionally macroscopic range and thus to a detrimental effect on the function and in particular the determination of the actual signal rates or count rates ,
• the detector signal is reduced, so that this not only leads to a reduction in the efficiency of the detector but also to increased difficulties in the evaluation of the count or signal rate, with such a disadvantageous effect both at high count rates
• Usually integration of a plurality of signals takes place, as occurs in a determination of individual pulses or a detection of individual particles, as stated above.
• the present invention therefore aims to provide a method and an apparatus for detecting elementary particle according to the above-mentioned type is available, whereby the above-mentioned disadvantages in the use of known diamond detectors eliminated by a "occurrence of polarization charges or polarization effects, or at least substantially be minimized.
• the provision of a method and a device is aimed at, wherein even with prolonged use of such a detector no negative influence is given by the occurrence of polarization charges in the interior of the detector or detector material.
• a method of the type initially mentioned is essentially characterized in that a compensation voltage is applied in each case for a limited time to one electrode of the detector in order to remove polarization charges arising in the detector during operation.
• a compensation voltage is applied to an electrode of the detector for a limited time, is caused that during operation over a longer period of time inside the detector or detector material resulting polarization charges removed by the application of the compensation voltage and the polarization charge carriers are reversed, whereby the original state of the detector or detector material is again produced without the presence of such polarization charges in the interior.
• the detector is optionally not for a very short period of time for a detection of signals or pulses or count rates available, after the application of the compensation voltage and thus a removal of the polarization charges turn the full capacity or Power of the detector can be provided with a correspondingly high signal strength.
• Such a high and, in particular, substantially constant signal strength is of particular importance in the case of detection of elementary particles due to the usually extremely low signal strength, since a decrease in the signal strength due to the presence of polarization charges in the detector material makes evaluation of signals or pulses of low intensity increasingly difficult is because a reliable distinction of the signal from any existing noise or background according to different signal levels or strengths required.
• the compensation voltage be applied cyclically to the detector so as to provide reliable operation or operation of the detector for detecting elementary particles.
• the compensation voltage is applied when a threshold value is reached, in particular when the count rate or signal strength of the detector is undershot. In this way, it is ensured that in the event of possibly different stresses or exposures to the detector, a drop in signal or count rates will prevent a negative influence or falsification of results, in particular in a subsequent evaluation.
• a voltage of the same polarity as the detector voltage is selected as the compensation voltage and is applied to an electrode of the detector, which is different from the electrode which is supplied with the detector voltage, in particular high voltage, during operation of the detector. wherein the compensation voltage is selected by at least 20%, in particular at least 50% higher than the detector voltage.
• the compensation voltage is substantially twice as high as the detector voltage is selected, as corresponds to a further preferred embodiment of the method according to the invention.
• a compensation voltage to the electrode which is not supplied with the detector voltage during normal operation of the detector is proposed according to a further modified and alternative and preferred embodiment of the method according to the invention that as a compensation voltage, a detector voltage with the opposite polarity to the during operation of the detector with the detector voltage, in particular high voltage supplied electrode is applied.
• a compensation voltage By such a supply of the electrode of the Detek- gate to which the detector voltage, in particular high voltage is applied during operation, with a compensation voltage of opposite polarity is also a reversal of the electric field strength or the electric field causes in the detector, so that in turn, as already mentioned above, the free charge carriers removed and Polarization charge carriers are reversed polarity, in turn, to produce the original state of the detector or detector material.
• Such a supply with a detector voltage of opposite polarity can also take place, for example, by providing an AC voltage or a voltage in the form of a square wave, so that in each case during the operation of the detector according to the frequency of the applied AC voltage restoration of the original field state by removal of free Charge carriers or a polarity reversal polarization charge carriers is made.
• the detector is formed in a manner known per se by a diamond detector.
• a device of the abovementioned type is essentially characterized in that in order to remove polarization charges arising in the detector during operation, in each case in time limited to an electrode of the detector, a compensation voltage can be applied.
• a compensation voltage can be applied in each case in time limited to an electrode of the detector.
• the compensation voltage can be applied cyclically to the detector.
• a voltage of the same polarity as the detector voltage is selected as the compensation voltage and is applied to an electrode of the detector which is connected to the electrode is different, which is supplied in the operation of the detector with the detector voltage, in particular high voltage, wherein the compensation voltage is selected by at least 20%, in particular at least 50% higher than the detector voltage.
• a detector voltage with reversed polarity can be applied to the electrode supplied with the detector voltage, in particular high voltage, during the operation of the detector as the compensation voltage.
• a second high-voltage source When, for example, an AC voltage or a voltage in the manner of a square wave pulse is provided.
• the detector is formed in a manner known per se by a diamond detector, wherein a detector element consisting of diamond is arranged between plate-shaped elements, and a contacting of electrodes of the detector element is at least partially formed by spring elements.
• a diamond detector which is known per se
• the inventively provided at least partial contacting by spring elements reliably supplies the electrodes of the detector material essentially also formed of a plate-shaped element even taking into account the small dimensions of the detector as well as the high voltages to be applied For example, at least 500 volts ensured.
• the spring not only an electrical, but also a mechanical contact for fixing the detector element is provided, so that can be dispensed with expensive adhesive connections.
• the spring element is formed by a particular gold-plated beryllium spring.
• FIG. 1 shows a schematic diagram of a device according to the invention for carrying out the method according to the invention for detecting elementary particles
• Fig. 2 is a schematic diagram showing the decrease of the efficiency of the detector as time passes through polarization effects inside the detector material; 3 shows a schematic diagram of a first embodiment of the method according to the invention, in which a detector voltage with reversed polarity is applied as compensating voltage;
• FIG. 4 shows a schematic representation of an embodiment of the method according to the invention which is shown in FIG. 4 a, a constant voltage applied to an electrode of the detector, in particular high voltage, is shown in FIG. 4 b a compensation voltage which is applied to the second electrode and greater than the detector voltage, and Figure 4c shows the detector voltage resulting from a combination of the voltages shown in Figures 4a and 4b;
• FIG. 5 shows, in a representation similar to FIG. 2, the effect of the method according to the invention of applying a compensation voltage to eliminate polarization charges and to restore the original state of the detector material;
• FIG. 6 shows a schematic section through an embodiment of a diamond detector for use in the device according to the invention
• FIG. 7 shows, on an enlarged scale, a detailed illustration of the detector element coated or formed with electrode material
• Fig. 8 is a schematic partial plan view corresponding to the arrow VIII of Fig. 6 on the detector with removal of a cover plate.
• Fig. 1, 1 is schematically denoted by a detector formed by a diamond detector, as will be discussed in detail below with reference to Figs. 6-8.
• One electrode of the detector 1 is supplied via a first high voltage source HV1 with a detector voltage, in particular high voltage of for example 500 volts, wherein in addition a charging resistor Ri is indicated.
• a charging capacitor C s is indicated in FIG.
• such detectors 1 can be operated with a field strength of about 1-2 V / ⁇ , so that, for example, a thickness of 500 V results for thicknesses of about 500 ⁇ . At thicknesses of about 100 ⁇ voltages between 100 V and 200 V, for example, are used.
• a second high-voltage source HV2 is shown in the circuit diagram shown schematically in FIG. 1, which also has a voltage, in particular high voltage ⁇ p 2, via a charging resistor R 2 to the second electrode of the generally designated 1 detector provides.
• a detector voltage 9 1 -9 2 is thus applied to the detector or detector material or to its electrodes.
• coupling capacitor C k and an amplifier Amp are additionally indicated in FIG. 1, wherein additionally a load resistor R L is provided.
• a detector signal emanating from the amplifier Amp which is designated schematically by 2 is correspondingly processed or further processed in an evaluation electronics, indicated schematically by 3, as is generally known.
• Fig. 2 is schematically indicated how a plotted on the Y-axis efficiency of the detector decreases due to a generation of polarization charges inside the detector material in the course of time, since the externally applied in such a way inside the detector Mate ⁇ rials arising polarization field counteracts elec trical field ⁇ and thus decreases the efficiency of the Detek ⁇ tors.
• arbitrary units au are assumed, and to illustrate the effect of the polarization charges, the decrease in efficiency is exaggerated.
• ⁇ identified process procedure that is performed in time sequence for example, similar to a rectangular wave pulse, a polarity reversal of the polarity of the detection voltage, which from the high-voltage source HV1, as shown in FIG. 1, to an electrode of the detector 1, this being indicated in FIG. 3 by ci or - ⁇ ⁇ .
• a corresponding polarity reversal of the readout or evaluation electronics 3, which is indicated in FIG. 1, can be used to ensure that a corresponding determination of pulses or polarity is achieved even if the detector voltage is reversed Count rates can be made in the detector 1, so that, taking into account the respective reversed polarity of De ⁇ detector 1 can be operated substantially without interruption by using a bipolar evaluation.
• the detection voltage cp lf shows which of the high voltage source HV1 as shown in FIG. 1 is applied to an electrode of the detector 1, is provided.
• the provided by the high voltage source HV2 voltage cp 2 exceeds the detector voltage ⁇ ⁇ , wherein to achieve the desired effect of removal of polarization charges within a comparatively short period of time, the compensation voltage provided by the high voltage source HV2 exceeds the detector voltage, for example by at least 50%, and is preferably approximately twice the detector voltage. To achieve a total negative potential, the compensation voltage must be higher than the detector voltage. Even a provision of a double compensation voltage is within normal operating ranges of such detectors 1 of a maximum of 2 ⁇ / ⁇ .
• a generally designated 1 in Fig. 1 detector is shown partially in an exploded view of FIG. 6 and in greater detail of FIG. 7.
• the detector 1 has a detector element 11 formed by a diamond, wherein at the substantially plate-shaped detector element 11, as can be seen in particular clearly from Fig. 7, are provided on both sides substantially flat electrodes 12 and 13.
• the detector element 11 is surrounded by an intermediate plate 14 and supported on a base plate 15, wherein on the base plate 15, a ground contact 16 is indicated, which comes into contact with the electrode 12 in the assembled state.
• a contacting of the second electrode 13 via a spring-like element 17 is formed, which is formed by a beryllium spring, which is gold-plated for a mechanical and electrical contact beyond.
• this beryllium spring 17 comes into contact with a signal line 18, which serves via a schematically indicated plug element 19 both for a signal derivation and for a supply with the detector voltage corresponding to the first high voltage source HV1.
• a characteristic impedance of 50 ⁇ is provided for the signal line.
• an additional cover plate with 20 is also indicated.
• the signal line is again denoted by 18, via which via the plug or connector 19 not only a decrease of the signal but also a supply of the detector voltage from the first high voltage supply or .
• Source HVl done.
• ground contact 16 is connected either via a further plug 21 to ground or in the embodiment of FIG. 3 via this plug 21 a Supply is provided with the voltage provided by the second high-voltage source HV2.
• a supply of the detector element 11 takes place via the contact 16 in the assembled state, as can be seen from FIG. 6, wherein additionally a recess or a hole 22 for a calibration for a proper positioning of the detector element 11 can be seen in FIG.
• a removal of free charge carriers or a polarity reversal of polarization charge carriers in the interior of the detector material 11 is thus possible by providing a compensation voltage for a limited period of time in order to periodically or cyclically provide the original field state of the detector material 11 , as can be seen from the illustration of FIG. 5.
• Such a provision of the compensation voltage can either take place cyclically or be provided, for example, when falling below a threshold value with regard to a count rate or signal strength.
• a connection of the compensation voltage by an external intervention for example, be made manually at specially selected times.
• the compensation voltage can be cyclically applied to the detector 1, for example, when used in conjunction with a particle accelerator, such a removal of polarization charges can be made after each turn.
• a removal of polarization charges or such a "refresh cycle" can be performed manually or after elapse of a predetermined period of time.
• such a removal of polarization charges can be carried out or initiated, in particular, when a threshold value is undershot, as can be seen, for example, from the schematic representation of FIG. 5.
• this can be used in particular in the field of beam loss monitors, in which, for example, during operation of particle accelerators proper operation is monitored.
• use in conjunction with spectrometers or calorimeters is expedient or favorable, wherein, for example, an energy measurement or a spectroscopic measurement is carried out in particular of low-energy particles.
• neutrons can impinge on such a detector unit, with charged particles of the detector material being charged, whose number and / or amplitude represents a measure of the energy of the particles to be monitored.

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• 2012
  • 2012-05-07 AT ATA535/2012A patent/AT512869B1/de active
• 2013
  • 2013-04-30 WO PCT/AT2013/000082 patent/WO2013166532A2/fr not_active Ceased

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