A variable gain particle detector

Abstract

The invention provides a variable gain particle detector, comprising a cathode preamplifier module, a signal processing module SPM and a high voltage control module HVCM which are electrically connected in sequence, wherein the cathode preamplifier module senses and amplifies a current signal; the signal processing module SPM processes the current signal to form a control signal through differentiation and peak detection broadening; the high voltage control module HVCM generates a high voltage adjustment pulse which is loaded to a gas electron avalanche gain structure. When a neutron is incident on the detector of the invention, emitted particles and ionized electrons are generated, and the electrons begin to drift at a uniform speed to sense a current signal at the cathode, and the cathode induced signal is integrated and amplified by the preamplifier. After the rising edge of the preamplifier signal is differentiated and peak detected and broadened by the signal processing module SPM, the signal processing module SPM outputs a control signal, and the control signal output by the signal processing module SPM is input into the high voltage control module HVCM after being delayed, so as to generate a high voltage adjustment pulse to reduce the working voltage amplitude of the gas electron avalanche gain structure, thereby realizing dynamic adjustment of the gain of a time projection chamber TPC.

Description

Technical Field

[0001] The present invention relates to the technical field of particle detectors, and in particular to a variable gain particle detector. Background Art

[0002] The Time Projection Chamber (TPC) is a particle detector widely used in particle and nuclear physics. By measuring particle track lengths, the TPC can simultaneously measure and identify neutron-proton elastic scattering (NP-ELS) and fission reactions. High-precision NP-ELS data is used as a reference cross section to improve the accuracy of fission cross section measurements.

[0003] NP-scattering is currently the most accurate neutron standard cross-section reaction. Measuring fission cross-sections using NP-scattering as a reference cross-section will significantly improve the accuracy of fission cross-section measurements. When the incident neutron energy is above 15 MeV, the forward-scattered proton energy will also exceed 10 MeV. Considering a 15 MeV proton, calculations show that its energy loss in argon at 1 atm pressure is 4 keV / mm. For fission fragments, such as the 75 MeV 144 Ba produced by the fission of 235 U, its energy loss per unit distance in 1 atm argon is 6.4 MeV / mm. The ratio of the energy loss of fission fragments to that of scattered protons is approximately 1600. Considering the inherent noise of the detector and electronics, as well as external noise interference, the dynamic range of the electronics must be approximately 5000 times greater to effectively measure both scattered protons and fission fragments simultaneously. Existing TPC electronics systems achieve a dynamic range of 2000 times, but this still struggles to achieve the ideal design specifications for detector systems.

[0004] To effectively measure protons above 10 MeV, the TPC's electron avalanche gain must reach 1E4, ensuring a sufficiently high signal-to-noise ratio. At this gain, the charge of electrons generated by heavy nuclei (such as argon nuclei in gas) and fission fragments ejected by neutrons, after avalanche gain, reaches 1E9 / mm. This can easily cause detector sparking, affecting stable operation and reducing data acquisition efficiency and reliability. Therefore, from the perspective of detector stability, using a constant-gain detector is not conducive to experimental measurements of fission cross sections.

[0005] In order to apply TPC to the experimental measurement of fission cross sections in subsequent studies, the problem of insufficient dynamic range needs to be solved. Conventional methods of expanding the dynamic range of electronics have great technical challenges and high development costs, and are not feasible at the current level of technology. The present invention takes another approach and proposes the use of variable gain technology. By dynamically adjusting the high voltage of the TPC, the TPC gain decreases as the energy of the emitted particles increases, so that the detector's response to the particle energy is converted from a linear response to a nonlinear response. This reduces the demand for the dynamic range of the readout electronics, while ensuring the stable and normal operation of the detector, and achieving effective simultaneous measurement of fission fragments and scattered protons.

[0006] Therefore, it is necessary to provide a variable gain particle detector to solve the above technical problems. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a variable gain particle detector for solving the problem of insufficient dynamic range in order to apply TPC to the experimental measurement of fission cross section in subsequent research. The conventional method of expanding the dynamic range of electronics has great technical challenges and high development costs, and is not highly feasible under the current technological level.

[0008] The present invention provides a variable gain particle detector, comprising a cathode preamplifier module, a signal processing module SPM and a high voltage control module HVCM electrically connected in sequence, wherein:

[0009] The cathode preamplifier module is used to integrate and amplify the current signal induced by the cathode when the electrons are forced to drift at a uniform speed after the neutron is incident. Specifically, when the neutron is incident, outgoing particles and ionized electrons are generated, and the electrons begin to drift at a uniform speed and induce a current signal at the cathode.

[0010] The signal processing module SPM is used to receive the current signal after integration and amplification by the cathode preamplifier module, and sequentially perform differential processing and peak detection and broadening processing in the signal processing module SPM to form a control signal containing particle energy information. Specifically, the cathode sensing signal is integrated and amplified by the preamplifier (PA), and the rising edge of the preamplifier (PA) signal is differentiated and peak detected and broadened by the signal processing module SPM, and the signal processing module SPM outputs the control signal.

[0011] The high-voltage control module HVCM is used to receive the control signal output by the signal processing module SPM. The control signal is processed by the high-voltage control module HVCM to generate a high-voltage adjustment pulse, and finally loaded into the gas electron avalanche gain structure using AC coupling to reduce the operating voltage amplitude of the gas electron avalanche gain structure. Specifically, the control signal output by the signal processing module SPM is input into the high-voltage control module HVCM after a delay to generate a high-voltage adjustment pulse, which is output to the gas electron avalanche gain structure to reduce the operating voltage amplitude of the gas electron avalanche gain structure and realize dynamic adjustment of the gain of the time projection chamber TPC.

[0012] Preferably, the cathode preamplifier module is a capacitor negative feedback charge integration amplifier circuit with a field effect transistor as input; specifically, the circuit is a capacitor negative feedback charge integration circuit with a field effect transistor as input, wherein the amplifier circuit part mainly adopts a differential amplifier structure and a common emitter amplifier circuit, and the output stage adopts a push-pull power output circuit.

[0013] Preferably, the amplifier circuit in the integrating amplifier circuit includes a differential amplifier structure and a common-emitter amplifier circuit, and the output stage adopts a push-pull power output circuit.

[0014] Preferably, the signal processing module SPM is composed of a differential circuit and a peak detection circuit, and the differential circuit is electrically connected to the signal input end of the peak detection circuit; specifically, the leading edge slope of the cathode preamplifier (PA) signal is proportional to the product of the number of ionized electrons and the drift velocity in the time projection chamber TPC, so by differentiating the rising edge slope of the cathode preamplifier (PA) signal, the number of ionized electrons of the incident particles and the energy of the incident particles can be indirectly obtained.

[0015] Preferably, a delay block is provided between the signal processing module SPM and the high voltage control module HVCM, and the delay time of the delay block is greater than the time from the cathode signal starting point to the peak point of the differential signal in the signal processing module SPM.

[0016] Preferably, the high-voltage control module HVCM is composed of a first-stage inverting amplifier circuit and a high-voltage amplifier circuit composed of two-stage metal oxide field-effect transistors. After the control signal passes through the first-stage inverting amplifier circuit, a high-voltage adjustment pulse is input to the gas electron avalanche gain structure through AC coupling to reduce the operating voltage amplitude of the gas electron avalanche gain structure.

[0017] Preferably, the gas electron avalanche gain structure is one of a microgrid gas electron multiplication structure, a gas electron multiplication membrane structure, a multi-wire proportional chamber structure or a microstrip gas counter structure.

[0018] Compared with related technologies, the variable gain particle detector provided by the present invention has the following beneficial effects:

[0019] When a neutron is incident on the detector of the present invention, it generates emitted particles and ionized electrons. The electrons begin to drift at a uniform speed and induce a current signal at the cathode. The cathode induced signal is integrated and amplified by a preamplifier. The rising edge of the preamplifier signal is differentiated and peak-detected and broadened by a signal processing module SPM. The signal processing module SPM outputs a control signal. The control signal output by the signal processing module SPM is input into a high-voltage control module HVCM after a delay to generate a high-voltage adjustment pulse, which is output to a gas electron avalanche gain structure. The high-voltage adjustment pulse of the positive signal is used to reduce the operating voltage amplitude of the gas electron avalanche gain structure, thereby realizing dynamic adjustment of the gain of the time projection chamber TPC and solving the problem of large dynamic range measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the gain adjustment principle of the present invention (the gas electron avalanche gain structure takes the microgrid gas electron multiplying structure Micromegas as an example);

[0021] Figure 2 This is a schematic diagram of the circuit structure of the signal processing module SPM and the high voltage control module HVCM of the present invention;

[0022] Figure 3 Schematic diagram of output waveforms of the preamplifier of the present invention using different integration times;

[0023] Figure 4 This is the dynamic high voltage regulation signal timing of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] A variable gain particle detector, the principle of dynamic gain adjustment is as follows Figure 1 As shown in the figure, when a high-energy particle is emitted, the cathode signal is first amplified by the preamplifier and then input into the signal processing module SPM. The signal processing module SPM processes the cathode preamplifier (PA) signal to obtain a control signal containing the particle energy information; the control signal is then input into the high-voltage control module HVCM, which amplifies the input control signal and completes the loading of the high-voltage adjustment pulse before the ionized electron drift of the incident particle reaches the gas electron avalanche gain structure, thereby reducing the operating voltage amplitude of the gas electron avalanche gain structure and realizing dynamic adjustment of the TPC gain.

[0026] Specifically, the basic structure of the cathode preamplifier circuit of TPC is a capacitor negative feedback charge integration circuit with a field effect transistor as input. The amplification circuit mainly adopts a differential amplification structure and a common emitter amplifier circuit, and the output stage adopts a push-pull power output circuit.

[0027] In this preamplifier circuit, the feedback capacitor is 1pF, which can obtain a large gain. The preamplifier design usually adopts a large integration time (for example, more than 100us) to obtain better energy resolution. In this case, since the electrons drift at a uniform speed in the TPC, the leading edge of the output signal of the preamplifier (PA) is approximately a straight rising waveform (such as Figure 2 As shown in Figure 2, after the waveform is processed by the differential circuit in the signal processing module SPM, the peak position is uncertain. To ensure accurate detection of the peak value of the output signal of the differential circuit in the signal processing module SPM, the integration time of the cathode preamplifier (PA) is designed to be 10us, which is slightly longer than the drift time of the electron in the TPC. In this way, the preamplifier (PA) signal has the maximum slope near the starting point of the leading edge, can quickly reach the peak after differentiation, and the peak position is relatively accurate (as shown in Figure 2). Figure 2 shown).

[0028] The circuit structure of the signal processing module SPM is as follows Figure 3 As shown in the figure, the module consists of a differential circuit and a peak detection circuit. The leading edge slope of the cathode preamplifier (PA) signal is proportional to the product of the number of ionized electrons in the TPC and the drift velocity. Therefore, by differentiating the rising edge slope of the cathode preamplifier (PA) signal, the number of ionized electrons and the energy of the incident particles can be indirectly obtained.

[0029] This method can obtain particle energy information faster than reading the highest point of the preamplifier signal, and can generate a control signal and complete the high-voltage adjustment before the ionized electron drifts to the gas electron avalanche gain structure. However, if the conventional method of reading the peak value of the preamplifier (PA) waveform is used to obtain the incident particle energy, when the preamplifier (PA) signal reaches the peak value, all ionized electrons have completed the drift process and reached the gas electron avalanche gain structure, and there will not be sufficient time margin for high-voltage adjustment.

[0030] After differential processing, the peak detection circuit is input, which holds and widens the detected peak to form a control signal. The width of the control signal is slightly larger than the drift time of the electron in the TPC, ensuring that the high voltage of the gas electron avalanche gain structure is maintained at the dynamically set high voltage before all electrons are collected.

[0031] The signal output of the signal processing module SPM enters the high-voltage control module HVCM after passing through a delay block. The delay time of the delay block is slightly longer than the time from the starting point of the cathode signal to the peak point of the differential signal in the SPM. This ensures that the electric field in the TPC field cage remains uniform before the peak detection circuit detects the peak of the differential signal. In this way, the electron drift process will not be affected by the high-voltage regulation before the peak detection, ensuring the accuracy of the peak detection.

[0032] After the control signal is input into the high-voltage control module HVCM, it first passes through a first-stage inverting amplifier circuit, then is AC-coupled and input into a high-voltage amplifier circuit consisting of a two-stage metal oxide field-effect transistor, and finally is loaded into the gas electron avalanche gain structure using AC coupling to achieve gain adjustment.

[0033] The signal timing of each module mentioned above is summarized as follows: Figure 4 As shown in the figure, when a neutron is incident, outgoing particles and ionized electrons are generated. The electrons begin to drift at a uniform speed, inducing a current signal at the cathode. The cathode-induced signal is integrated and amplified by the preamplifier (PA). The rising edge of the preamplifier (PA) signal is differentiated and peak-detected by the signal processing module (SPM). The signal processing module (SPM) then outputs a control signal. The SPM control signal is then delayed and input into the high-voltage control module (HVCM), generating a high-voltage modulation pulse that is output to the gas electron avalanche gain structure. Because the base operating voltage of the gas electron avalanche gain structure is a negative high voltage, the applied high-voltage modulation pulse is a positive signal to reduce its operating voltage amplitude.

[0034] In the present application, the gas electron avalanche gain structure can be a microgrid gas electron multiplying structure, a gas electron multiplying membrane structure, a multi-wire proportional chamber structure, or a microstrip gas counter structure, but is not limited thereto; the differential circuit structure or the peak detection circuit in the circuit of the signal processing module SPM adopts adjusted circuit structure and component parameters; the circuit of the high-voltage control module HVCM adopts adjusted amplification circuit structure and component parameters; the detector adopts other types of working media, such as liquid media, semiconductor media, etc.; the detector adopts other geometric shapes, such as square, cylindrical, polygonal, strip, etc.

[0035] The working principle of a variable gain particle detector provided by the present invention is as follows: when a neutron is incident on the detector of the present invention, it generates emitted particles and ionized electrons, and the electrons begin to drift at a uniform speed to induce a current signal at the cathode. The cathode induced signal is integrated and amplified by the preamplifier. The rising edge of the preamplifier signal is differentiated and peak detected and broadened by the signal processing module SPM. The signal processing module SPM outputs a control signal. The control signal output by the signal processing module SPM is input into the high-voltage control module HVCM after delay, generating a high-voltage adjustment pulse, which is output to the gas electron avalanche gain structure. The high-voltage adjustment pulse of the positive signal is used to reduce the operating voltage amplitude of the gas electron avalanche gain structure, thereby realizing dynamic adjustment of the time projection chamber TPC gain.

[0036] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0037] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A variable gain particle detector, characterized in that: It includes a cathode preamplifier module, a signal processing module SPM and a high voltage control module HVCM which are electrically connected in sequence, wherein: The cathode preamplifier module is a capacitor negative feedback charge integration amplifier circuit with a field effect tube as input, which is used to integrate and amplify the current signal induced by the cathode generated by the uniform drift of electrons after neutron incidence; The signal processing module SPM is composed of a differential circuit and a peak detection circuit, and the differential circuit is electrically connected to the signal input end of the peak detection circuit, and is used to receive the signal after the cathode preamplification module integrates and amplifies it, and sequentially undergoes differential processing and peak detection broadening processing in the signal processing module SPM to form a control signal containing particle energy information; The high-voltage control module HVCM is composed of a first-stage inverting amplifier circuit and a high-voltage amplifier circuit composed of two stages of metal oxide field effect transistors. After the control signal passes through the first-stage inverting amplifier circuit, a high-voltage adjustment pulse is input to the gas electron avalanche gain structure through AC coupling to reduce the working voltage amplitude of the gas electron avalanche gain structure. It is used to receive the control signal output by the signal processing module SPM. The control signal is processed by the high-voltage control module HVCM to generate a high-voltage adjustment pulse, and finally loaded to the gas electron avalanche gain structure by AC coupling to reduce the working voltage amplitude of the gas electron avalanche gain structure.

2. A variable gain particle detector according to claim 1, characterized in that: The amplifier circuit in the integral amplifier circuit includes a differential amplifier structure and a common-emitter amplifier circuit, and the output stage adopts a push-pull power output circuit.

3. A variable gain particle detector according to claim 1, characterized in that: A delay block is also provided between the signal processing module SPM and the high voltage control module HVCM, and the delay time of the delay block is greater than the time from the cathode signal starting point to the peak point of the differential signal in the signal processing module SPM.

4. A variable gain particle detector according to claim 1, characterized in that: The gas electron avalanche gain structure is one of a microgrid gas electron multiplication structure, a gas electron multiplication membrane structure, a multi-wire proportional chamber structure or a microstrip gas counter structure.

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