EP2329511A1 - Système de contrôle de dérive de gain de photomultiplicateur et procédé associé - Google Patents
Système de contrôle de dérive de gain de photomultiplicateur et procédé associéInfo
- Publication number
- EP2329511A1 EP2329511A1 EP09815675A EP09815675A EP2329511A1 EP 2329511 A1 EP2329511 A1 EP 2329511A1 EP 09815675 A EP09815675 A EP 09815675A EP 09815675 A EP09815675 A EP 09815675A EP 2329511 A1 EP2329511 A1 EP 2329511A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- photomultiplier
- input
- output
- signal
- integrator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000000034 method Methods 0.000 title claims description 11
- 238000012544 monitoring process Methods 0.000 title abstract 2
- 238000005259 measurement Methods 0.000 claims abstract description 25
- 230000003287 optical effect Effects 0.000 claims description 9
- 230000005374 Kerr effect Effects 0.000 claims description 8
- 239000003990 capacitor Substances 0.000 claims description 8
- 230000002123 temporal effect Effects 0.000 claims description 3
- 238000011144 upstream manufacturing Methods 0.000 claims 1
- 230000003019 stabilising effect Effects 0.000 abstract 2
- 239000000463 material Substances 0.000 description 9
- 230000006641 stabilisation Effects 0.000 description 7
- 238000011105 stabilization Methods 0.000 description 7
- 230000005855 radiation Effects 0.000 description 6
- 230000008901 benefit Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000002285 radioactive effect Effects 0.000 description 2
- 238000004611 spectroscopical analysis Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 206010073306 Exposure to radiation Diseases 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- 230000001960 triggered effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
- H01J43/30—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
Definitions
- the present invention provides a photomultiplier gain drift control system and a photomultiplier gain drift control method.
- the invention applies to stabilizing the gain of a photomultiplier used for spectrometry or photon counting measurements in the fields of nuclear measurement and medical measurement.
- the invention is also applicable to the stabilization of neutron measurement systems using photomultipliers as well as the stabilization of the gain of photomultipliers used in optical spectroscopy applications.
- a photomultiplier is a device for the detection of photons. It is in the form of an electron tube. Under the action of light, electrons are torn from a bialkalimetal by photoelectric effect to a photocathode, the low electric current thus generated is amplified by a series of dynodes using the secondary emission phenomenon to obtain a significant gain. Such a detector makes it possible to count the photons individually.
- Figure la shows a conventional photomultiplier. It consists of a glass vacuum tube 100 containing a photocathode 110, a focusing electrode 115, an "electron multiplier" consisting of a set of electrodes 120, called dynodes, and an anode 130.
- a photocathode is a material capable of converting radiation into an electron by secondary emission.
- the photomultiplier is coupled to a scintillator 140.
- a scintillator is a material that emits light photons as a result of the absorption of radiation.
- the photomultiplier operates as will be indicated hereinafter.
- the scintillator 140 is illuminated, that is to say subjected to radiation. Under the effect of this radiation, the atoms of the material constituting the scintillator are "excited", that is to say that the electrons pass to a higher energy level.
- Incident photons 150 strike the material constituting the photocathode, which forms a thin layer deposited on the input window of the device. Electrons 117 are then produced by photoelectric effect. The electrons 117 are directed towards the electron multiplier by the focusing electrode 115. The electrons 117 leave the photocathode with an energy corresponding to that of the incident photon, minus the energy of the operation of the photocathode 110. The electrons 117 are accelerated by the electric field and arrive on the first dynode with a much higher energy, for example a few hundred electronvolts. When the electrons touch the dynode, they cause a mechanism called secondary emission.
- Fig. 1b represents a histogram illustrating the relationship between the wanted signal and the noise in a photomultiplier.
- the axis x is the axis of the amplitudes of the pulses delivered by the photomultiplier and the axis y is the axis of the quantities of pulses which are associated with the amplitudes of the pulses.
- the curve C1 represents the noise of the photomultiplier and the curve C2 represents the signal consisting of the wanted signal and the noise signal.
- FIG. 1b it can be seen that there is a relevant difference between the derivative of the curve comprising only the noise and the curve including the noise and the useful signal. It is this difference that indicates the drift of the photomultiplier.
- Photomultipliers are widely used in measuring devices in the nuclear and medical fields. The general characteristics of a photomultiplier make it a very powerful tool in terms of light / electron conversion efficiency. However, intrinsically, photomultipliers exhibit drifts related to their own functioning (problems of temperature and aging). These drifts generally result in a change in the overall gain of the photomultiplier. Gain is the fundamental parameter describing the overall efficiency of the photomultiplier.
- a second drawback is, in low level measurement, that having a source present in the scintillator adds a contribution of background noise which is detrimental to the quality of the overall measurement.
- a second disadvantage is that the coupling between the LED and the photomultiplier and the scintillator can cause implementation problems by making the construction more complex by adding elements.
- a third drawback lies in the fact that the quantity of photons emitted by the LED does not match what is emitted by a scintillator.
- the LED as an active system is itself subject to drifts that must be corrected. There is therefore a gain drift correction system which itself must be corrected and stabilized in temperature, which hampers the simplicity of implementation and multiplies the sources of errors.
- the photomultiplier gain drift control system of the invention does not have the disadvantages mentioned above.
- the invention relates to a photomultiplier gain drift control system, the system comprising:
- the invention also relates to a photomultiplier gain drift control method comprising
- the method of the invention stabilizes the gain of a photomultiplier using properties intrinsic to the photomultiplier.
- the stabilization method according to the invention is advantageously based on the correlation that exists between the noise internal to the photomultiplier and the gain of the photomultiplier.
- Figure la already described, represents a photomultiplier according to the prior art
- Figure Ib already described, represents a diagram illustrating the relationship between the signal and the noise in a photomultiplier
- Figure 2a shows a photomultiplier gain drift control system according to a first embodiment of the invention
- Figure 2b shows different processed signals in a system according to the system shown in Figure 2a;
- FIG. 3 shows a photomultiplier gain drift control system according to a variant of the first embodiment of the invention
- FIG. 4 represents a photomultiplier gain drift control system according to a second embodiment of the invention
- Fig. 5 shows a photomultiplier gain drift control system according to a third embodiment of the invention.
- Fig. 6 shows various processed signals in a photomultiplier gain drift control system according to the system shown in Fig. 5;
- Figure 7 shows an integrator used in variants of the invention
- FIGS 8a and 8b show filters suitable for use in the photomultiplier gain drift control systems of the invention.
- Figure 2a shows a photomultiplier gain control system according to a first embodiment of the invention.
- a scintillator 1 has an output connected to the input of a photomultiplier 2 whose output is connected, on the one hand, to a first integrator 35 comprising an amplifier 5 connected in parallel with a capacitor 25 and a first switch 27, and, on the other hand, to a discriminator 6.
- a preamplifier 4 is placed at the output of the photomultiplier so that it is then the output of the preamplifier 4 which is connected to the first integrator 35 and the discriminator 6.
- the discriminator 6 drives the first switch 27 and a second switch 7 whose input is connected to the output of the first integrator 35 and whose output is connected to the input of a filter 8.
- the output of the filter 8 is connected to a first input of a second integrator 9.
- An example of an integrator which can be used in this embodiment is illustrated in FIG. 7 and will be described later.
- a reference voltage 10 is connected to a second input of the second integrator 9.
- the second integrator 9 has its output connected to the input of an adjustable high voltage device 3 which is known per se and whose output is connected to a photomultiplier voltage control input 2.
- the function of the device 3 is to supply the photomultiplier 2 with high voltage as a function of the signal delivered at the output of the second integrator 9, and thereby to adjust the total gain of the photomultiplier per action. on the high voltage and the different dynodes of the tube according to the result of the analysis of the signal by the system described above.
- FIG. 2b shows various ls-7s signals which are processed in a device according to the device of FIG. 2a.
- a first signal Is comprising the useful signal Su from the scintillator 1 and the noise signal Sb coming from the photomultiplier is simultaneously transmitted at the input of the first integrator 35 and at the input of the discriminator 6.
- the discriminator 6 measures, in a manner known per se, the amplitude and the duration of the pulses delivered by the photomultiplier.
- the discriminator 6 can be triggered either according to a clock signal predefined by the user (not shown in the figure) or according to the output signal of the photomultiplier.
- the discriminator 6 simultaneously sends a logic signal 3s to the first switch 27 belonging to the integrator 35 and a logic signal 4s to the second switch 7.
- the logic signal 3s has the function of closing the first switch 27 (tripping the first integrator 35) and the logic signal 4s has the function of closing the second electronic switch 7.
- the first integrator 35 integrates the noise pulses to obtain the surface of each pulse, that is to say to obtain the energy of each signal noise.
- the first integrator 35 sends an integrated output signal 2s to the second electronic switch 7.
- the amplitude of the signal 2s is then proportional to the energy of the noise signals.
- a fifth analog signal 5s from the first integrator is sent to the filter 8.
- the filter 8 determines the amplitudes of the signal 5s from the first integrator 5 and sends a sixth filtered signal 6s to the second integrator 9.
- the sixth signal 6s is a function of amplitude.
- the sixth signal 6s can be analog or digital.
- the second integrator 9 integrates the difference between the signal 6s and the reference voltage 10, the sixth signal 6s being a function of the intrinsic noise of the photomultiplier.
- the integrator 9 compares the amplitude of the sixth signal 6s with the reference voltage 10. According to the result of this comparison, the integrator 9 integrates the difference between its two inputs and generates a seventh signal 7s of constant value.
- the seventh signal 7s is supplied at the input of the device 3 and its function is to indicate to the device 3 the voltage to be applied to the control of the photomultiplier 2.
- the stabilization of the drift of the photomultiplier is effected by controlling the intrinsic noise Sb of the photomultiplier 2. In a first step, the noise Sb is separated from the useful signal Su. In a second step, the intrinsic noise of the photomultiplier is measured. Then, in a third step, this noise is stabilized at a constant value.
- Figure 3 shows a variant of the first embodiment of the invention.
- This variant differs from the embodiment of the invention shown in FIG. 2a by the presence of an optical time expander 11 located between the scintillator 1 and the photomultiplier 2.
- the output of the scintillator 1 is connected to the entry of the expander 11, whose output is connected to the input of the photomultiplier 2.
- the optical expander 11 comprises a material capable of temporally expanding the light pulses emitted by the scintillator.
- the presence of an optical expander is necessary in the case of very fast scintillating material whose temporal performance leads to useful signal shapes comparable to the noise signals.
- the optical expander then induces a change in the temporal distribution of the photons which facilitates the separation of the useful light pulse and the noise signals.
- FIG. 4 represents a photomultiplier gain drift control system according to a second embodiment of the invention.
- the output of the scintillator 1 is connected to the input of the photomultiplier 2 whose output is connected to the input of an amplitude spectrometer 31 which is connected, moreover, to a first input of an integrator 9, a second The input is connected to a reference voltage 10.
- a preamplifier 4 is placed between the output of the photomultiplier and the input of the spectrometer 31.
- the integrator 9 has its output connected to the input of an adjustable high voltage device 3 whose output is connected to a control input of the photomultiplier 2.
- a first signal Is is sent from the photomultiplier 2 to the amplitude spectrometer 31.
- the spectrum analysis by the Amplitude spectrometer 31 in the region of low amplitudes consists in performing, by a calculation of decrease of the spectrum observed, the distribution of the distribution of the amplitudes. Since the amplitude decrease of the spectrum in this region depends on the distribution of the amplitudes of the noise signals generated by the photomultiplier and the distribution of the amplitudes of the noise signals also depends on the gain of the photomultiplier 2, the stabilization of the decay in this region makes it possible to stabilize the gain of the photomultiplier.
- FIG. 5 represents a photomultiplier gain drift control system according to a third embodiment of the invention.
- the output of the scintillator 1 is connected to an input of a Kerr-effect-type optical switch 12, an output of which is connected to the input of the photomultiplier 2.
- the output of the photomultiplier 2 is connected to an input of a switch 14
- a preamplifier 4 is placed in series between the output of the photomultiplier and the input of the switch.
- the switch 14 has two outputs, among which a first output is connected to an input of a measurement chain 13 and a second output is connected to an input of a filter 8.
- An output of a clock 15 is connected, d on the one hand, to a high-voltage setting unit 16 of the Kerr cell and, on the other hand, to the control input of the switch 14.
- the clock signal transmitted from the clock 15 to the switch 14 has the function to control the periodicity of the link between, on the one hand, the photomultiplier and the measuring chain 13 and, on the other hand, the photomultiplier and the filter 8.
- the output of the unit 16 is connected to a control input of the Kerr effect cell 12.
- the unit 16 operates in a similar manner to the unit 3 and controls the Kerr effect cell 12 as a function of a clock signal from the clock 15.
- An output of the filter 8 is connected to a first input of an integrator 9, a second input of which is connected to a voltage of reference 10.
- the integrator 9 has an output connected to the high voltage control device 3, an output of which is connected to the control input of the photomultiplier 2.
- Figure 6 illustrates the signals Is, 15s, 9s, 10s and 6s which are shown in Figure 5 (third embodiment of the invention).
- the scintillator 1 sends a useful signal Su to the cell Kerr 12 which axs the incident signal it receives. Then, a first signal Is comprising said useful signal Su, which has been temporally chopped, and the signal noise Sb from the photomultiplier 2, is sent from the photomultiplier 2 to the switch 14.
- the clock 15 controls the setting of the switch 14 with a signal 15s consisting of a series of pulses. When a pulse arrives on the switch 14, a signal 10s consisting only of the noise pulses Sb which are delivered by the photomultiplier 2 is sent to the filter 8.
- the photomultiplier and the measurement chain 13 are electrically connected to each other and a 9s signal including the noise Sb and the useful signal Su is supplied to the measurement chain 13 for standard signal processing, known per se to those skilled in the art.
- the clock 15 also sends this signal 15s to the setting unit 16 of the high voltage of the cell Kerr.
- the system according to the invention is in a period of adjustment of the high voltage, that is to say the gain of the photomultiplier, and the control unit sets the Kerr cell 16 under high voltage.
- the clock 15 delivers no pulse, no adjustment is made, and the measurement chain 13 measures the signal 9s comprising the useful signal Su and the noise Sb from the photomultiplier.
- the circuit when a pulse is delivered, no signal is supplied to the measurement chain 13, and simultaneously, the signal 10s comprising only the noise Sb of the photomultiplier 2 is supplied to the filter 8.
- the measurement period can be, for example, example, equal to ten minutes, and the adjustment period can be, for example, example, equal to one second. Subsequently, beyond the filter 8, the circuit operates as described above with reference to Figure 2a.
- FIG 7 shows an integrator that can be used as integrator 35 or as integrator 9 in the previously described embodiments of the invention.
- the integrator comprises an amplifier A having an inverting input (-), a non-inverting input (+) and an output.
- a capacitor C is placed between the inverting input (-) and the output of the amplifier.
- a resistor R has a first terminal and a second terminal, the first terminal being connected to the inverting input (-).
- the signal 6s is applied to the second terminal of the resistor R and the reference voltage 10 is applied to the non-inverting input (+).
- FIG. 8a shows an example of a filter 8 known per se to those skilled in the art.
- the filter 8 is connected to the output of the second switch 7 according to the configuration illustrated in FIG. 3.
- the filter 8 comprises a resistor R having a first terminal and a second terminal.
- the first terminal of the resistor R is connected to the second switch 7.
- the second terminal of the resistor R is also connected to a first terminal of a capacitor C whose second terminal is connected to ground.
- the filter also includes an amplifier A having an input and an output.
- the input of the amplifier A is connected to the second terminal of the resistor R and to the first terminal of the capacitor C.
- the output of the amplifier is connected to the integrator 9.
- the filter receives the signal 5s and delivers the signal 6s.
- FIG 8b shows an example of filter 8 functioning as a rectifier.
- This filter comprises a diode D having an input and an output and a resistor R having a first terminal and a second terminal.
- the output of the diode D is connected to the first terminal of the resistor R whose second terminal is connected, moreover, to a first terminal of a capacitor C.
- the capacitor C has a second terminal which is connected to ground.
- the second terminal of the resistor R and the first terminal of the capacitor C are connected to the integrator 9.
- the filter receives the signal 5s and delivers the signal 6s.
Landscapes
- Measurement Of Radiation (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0856391A FR2936355B1 (fr) | 2008-09-23 | 2008-09-23 | Systeme de controle de derive de gain de photomultiplicateur et procede associe. |
PCT/EP2009/062242 WO2010034702A1 (fr) | 2008-09-23 | 2009-09-22 | Système de contrôle de dérive de gain de photomultiplicateur et procédé associé |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2329511A1 true EP2329511A1 (fr) | 2011-06-08 |
Family
ID=40672789
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP09815675A Withdrawn EP2329511A1 (fr) | 2008-09-23 | 2009-09-22 | Système de contrôle de dérive de gain de photomultiplicateur et procédé associé |
Country Status (5)
Country | Link |
---|---|
US (1) | US8624192B2 (fr) |
EP (1) | EP2329511A1 (fr) |
CA (1) | CA2736593C (fr) |
FR (1) | FR2936355B1 (fr) |
WO (1) | WO2010034702A1 (fr) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8912484B2 (en) | 2012-03-28 | 2014-12-16 | Schlumberger Technology Corporation | Photomultipler-based neutron detector |
DE112013002670B4 (de) * | 2012-06-15 | 2020-07-02 | Hitachi High-Technologies Corp. | Lichtsignal-Detektierschaltung, Lichtmengen-Detektiervorrichtung und mit einem Strahl geladener Teilchen arbeitende Vorrichtung |
EP3143432B1 (fr) * | 2014-05-11 | 2019-04-17 | Target Systemelektronik GmbH & Co. KG | Stabilisation de gain de photomultiplicateurs |
CN112513593B (zh) * | 2018-08-22 | 2023-10-10 | 株式会社日立高新技术 | 自动分析装置和光测量方法 |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3435233A (en) | 1966-03-24 | 1969-03-25 | Hughes Aircraft Co | Gain control system for photomultiplier systems |
US3644740A (en) | 1969-07-22 | 1972-02-22 | Hughes Aircraft Co | Control circuit for biasing a photodetector so as to maintain a selected false alarm rate |
DE2826484C2 (de) * | 1978-06-16 | 1982-08-26 | Laboratorium Prof. Dr. Rudolf Berthold, 7547 Wildbad | Regelverfahren zur automatischen Driftstabilisierung bei einer Strahlungsmessung und Verwendungen bei diesem Verfahren |
US4712010A (en) * | 1986-01-30 | 1987-12-08 | Hughes Aircraft Company | Radiator scanning with image enhancement and noise reduction |
US5179565A (en) * | 1990-06-07 | 1993-01-12 | Hamamatsu Photonics, K.K. | Low noise pulsed light source utilizing laser diode and voltage detector device utilizing same low noise pulsed light source |
US6490533B2 (en) * | 2001-04-26 | 2002-12-03 | Affymetrix, Inc. | System, method, and product for dynamic noise reduction in scanning of biological materials |
US7352840B1 (en) * | 2004-06-21 | 2008-04-01 | Radiation Monitoring Devices, Inc. | Micro CT scanners incorporating internal gain charge-coupled devices |
US20080203304A1 (en) * | 2007-02-22 | 2008-08-28 | The Regents Of The University Of Ca | Multichannel instrumentation for large detector arrays |
-
2008
- 2008-09-23 FR FR0856391A patent/FR2936355B1/fr active Active
-
2009
- 2009-09-22 WO PCT/EP2009/062242 patent/WO2010034702A1/fr active Application Filing
- 2009-09-22 EP EP09815675A patent/EP2329511A1/fr not_active Withdrawn
- 2009-09-22 CA CA2736593A patent/CA2736593C/fr not_active Expired - Fee Related
- 2009-09-22 US US13/119,709 patent/US8624192B2/en not_active Expired - Fee Related
Non-Patent Citations (2)
Title |
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None * |
See also references of WO2010034702A1 * |
Also Published As
Publication number | Publication date |
---|---|
CA2736593A1 (fr) | 2010-04-01 |
FR2936355A1 (fr) | 2010-03-26 |
US8624192B2 (en) | 2014-01-07 |
US20110186740A1 (en) | 2011-08-04 |
WO2010034702A1 (fr) | 2010-04-01 |
CA2736593C (fr) | 2017-02-07 |
FR2936355B1 (fr) | 2010-10-15 |
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