CN112269204B - Microchannel type fast neutron flight time detector - Google Patents
Microchannel type fast neutron flight time detector Download PDFInfo
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- CN112269204B CN112269204B CN202011143349.2A CN202011143349A CN112269204B CN 112269204 B CN112269204 B CN 112269204B CN 202011143349 A CN202011143349 A CN 202011143349A CN 112269204 B CN112269204 B CN 112269204B
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- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T3/00—Measuring neutron radiation
- G01T3/006—Measuring neutron radiation using self-powered detectors (for neutrons as well as for Y- or X-rays), e.g. using Compton-effect (Compton diodes) or photo-emission or a (n,B) nuclear reaction
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Abstract
The invention discloses a micro-channel type fast neutron flight time detector which comprises a neutron absorber and an electron collector arranged on one side of the neutron absorber, wherein a plurality of channels are distributed in the neutron absorber in an array manner, secondary electron emission layers are arranged on the inner walls of the channels, each channel penetrates through the thickness direction of the neutron absorber, electrodes are respectively arranged on the lateral surfaces of the neutron absorber at two ends of the corresponding channel, time-gated pulse high voltage is loaded between the two electrodes and used for forming an electric field in the channel, and the direction of the electric field faces towards the electron collector. The invention has the beneficial effects that: the signal of the neutron time-of-flight spectrum can be gated in the time domain, and the signal-to-noise ratio of the measurement is higher for weak signals under strong interference.
Description
Technical Field
The invention belongs to the technical field of neutron energy spectrum measurement, and particularly relates to a micro-channel type fast neutron flight time detector.
Background
The time-of-flight method is a common method for measuring neutron energy spectrum, and obtains the flight speed of neutrons by measuring the flight distance L and the flight time t of the neutrons, namely: v = L/t, then the formula "E =1/2mv 2 "calculate the energy E of the neutron.
In the prior art, a common device for measuring neutron energy by using a time-of-flight method is a scintillation detector, the scintillation detector consists of an organic scintillator and a photomultiplier, energy is deposited after neutrons enter the scintillator in the detection process so that the scintillator generates fluorescence, part of the fluorescence is collected by the photomultiplier to form an electrical signal, and then the flight distance L and the flight time t of the neutrons can be obtained, so that the energy E of the neutrons is obtained.
However, when the neutron source to be measured generates neutrons with two different energies and intensities, the scintillation detector measures two neutron signals, and if the neutron intensity arriving at the detector first is much higher than the neutron intensity arriving later, the tailing of the first signal will mask the later signal, so that the later signal cannot be measured. The signal tailing is mainly caused by fluorescence afterglow of a scintillator and can hardly be eliminated, so that the traditional scintillation detector can not play a role in the measurement scene.
Disclosure of Invention
In view of this, the present invention provides a micro-channel fast-neutron flight time detector to solve the technical problem in the prior art that when a neutron source to be measured generates neutrons with two different energies and intensities, the subsequent signals cannot be measured.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the utility model provides a microchannel type fast neutron time-of-flight detector which the key lies in: the neutron absorber comprises a neutron absorber and an electron collector arranged on one side of the neutron absorber, wherein channels are distributed in the neutron absorber in an array mode, secondary electron emission layers are arranged on the inner wall of each channel, each channel penetrates through the neutron absorber along the thickness direction, the neutron absorber is respectively provided with electrodes on the side faces of the two ends of the corresponding channel, a time gate control pulse high-voltage circuit is loaded between the two electrodes, an electric field is formed in the channel, and the direction of the electric field faces the electron collector.
By adopting the structure, after the neutron absorber detects neutrons, recoil protons can be generated in each channel and collide with the secondary electron emission layer to generate electrons, then the electrons move towards the high-potential direction in the channel under the action of an electric field, when the electrons collide with the channel wall, the secondary electron emission layer can emit a plurality of electrons to generate a multiplication effect, so that a large amount of electrons can be output from the channel, and the electrons are collected by the electron collecting electrode, so that a time-varying electric signal which can be recorded can be obtained. In the neutron detection mode, the process of scintillator luminescence is not carried out in the channel, the signal is generated from electrons generated in the neutron absorber, and because the voltage at two ends of the neutron absorber is the time gating pulse high voltage, the high voltage is closed when the first wave strong pulse neutrons arrive, no signal can be generated at the moment, the high voltage is opened when the second wave weak pulse neutrons which need to be measured arrive, and the flight time of the second wave neutrons can be measured independently.
Preferably, the method comprises the following steps: the neutron absorber is made of polyethylene. By adopting the structure, the content of hydrogen atoms in the polyethylene is high, and neutrons can be ensured to be fully elastically scattered with the hydrogen atoms in the polyethylene to generate recoil protons.
Preferably, the method comprises the following steps: a microchannel plate is arranged between the neutron absorber and the electron collector, the microchannel plate is made of lead glass, and a high-voltage electric field controlled by a time-gated pulse circuit is loaded between the upper side and the lower side of the microchannel plate. With the structure, the microchannel plate made of lead glass can multiply electrons so as to ensure that the electrons are multiplied and enough signal intensity can be obtained.
Preferably, the method comprises the following steps: the secondary electron emission layer is Al 2 O 3 And a film which is disposed on the inner wall of the channel in an electroplating manner. With the structure, when electrons impact Al 2 O 3 When thin films, more electrons are generated.
Preferably, the method comprises the following steps: and a conductive layer is plated between the neutron absorber and the secondary electron emission layer. With the above structure, electrons can be replenished to the secondary electron emission layer after the electrons thereof are consumed.
Preferably, the method comprises the following steps: the conductive layer is ZnO-Al 2 O 3 A film.
Preferably, the method comprises the following steps: the secondary electron emission layer has an average secondary electron emission coefficient of 1. By adopting the structure, the neutron sensitivity of the detector at different positions can be ensured to have better consistency.
Preferably, the method comprises the following steps: the neutron absorber has a thickness exceeding 1cm. By adopting the structure, the detection efficiency of fast neutrons can be improved.
Compared with the prior art, the invention has the beneficial effects that:
1. the micro-channel type neutron flight time detector can gate the signal of the neutron flight time spectrum in the time domain by using the time gating function, and has higher measurement signal-to-noise ratio for the weak signal under strong interference.
2. The neutron absorber adopts polyethylene material as the base, and possesses great sensitive thickness, has high detection efficiency to fast neutron.
Drawings
FIG. 1 is a schematic diagram of a microchannel fast neutron time-of-flight detector;
FIG. 2 is a schematic view of a reactive secondary electron emission layer and a conductive layer within a channel;
FIG. 3 is a partial schematic end view of a channel in a trench configuration;
fig. 4 is a partial schematic end view of a kidney-shaped channel.
Detailed Description
The present invention will be further described with reference to the following examples and the accompanying drawings.
As shown in fig. 1 and 2, a microchannel fast neutron time-of-flight detector relates to core components: neutron absorber 1, microchannel plate 4 and electron collector 2, microchannel plate 4 is located between neutron absorber 1 and electron collector 2, wherein, neutron absorber 1 is the microchannel structure also, it adopts polyethylene to make, array distribution has a plurality of to link up its thickness direction's passageway 1a in the neutron absorber 1, plated conducting layer 1c and secondary electron emission layer 1b on the inner wall of passageway 1a in proper order, neutron absorber 1 respectively is equipped with an electrode 3 on the side that corresponds passageway 1a both ends, load between two electrodes 3 and have voltage for form the electric field in the passageway 1a of neutron absorber 1, the direction of electric field is towards electron collector 2. The microchannel plate 4 is made of lead glass, and a voltage is also loaded between the two sides of the microchannel plate, and in the implementation, the voltages loaded on the neutron absorber 1 and the two sides of the microchannel plate 4 are both time-gated pulse high voltages.
The working principle of the micro-channel type fast neutron flight time detector is as follows:
the neutron and hydrogen atoms in a neutron absorber 1 made of polyethylene are elastically scattered to generate recoil protons, the recoil protons collide with a secondary electron emission layer 1b in a channel 1a to generate electrons, then the electrons move in the channel 1a in the direction of high potential under the acceleration action of an electric field, when the electrons collide with the wall of the channel 1a again, the secondary electron emission layer 1b can emit a plurality of electrons to generate a multiplication effect, so a large number of electrons can be output from the channel 1a, and then the electrons are collected by an electron collector 2 to obtain a time-varying electric signal which can be recorded, so that the measurement of the flight time of the neutron is completed. A common microchannel plate 4 is arranged on the outlet face of a channel 1a of the neutron absorber 1, and the time-gated pulses on two sides of the microchannel plate 4 are opened at high voltage, so that electrons can be further multiplied, and the electron collector 2 can be ensured to obtain enough signal intensity.
In the neutron detection mode, because the process of scintillator luminescence is not arranged in the channel 1a, the signal is generated from electrons generated in the neutron absorber 1, and the voltages at the two ends of the neutron absorber 1 and the microchannel plate 4 are time-gated pulse high voltages, the high voltage is closed when the first wave strong pulse neutrons arrive, no signal is generated at the time, the high voltage is opened when the second wave weak pulse neutrons which need to be measured arrive, and the flight time of the second wave neutrons can be measured independently. Namely: the voltage at two ends of the neutron absorber 1 and the microchannel plate 4 adopts time gating pulse high voltage, and a proper opening time window is set, so that the measurement signal of the detector can be gated in a time domain, and the signal beyond the window time can not interfere with an interested measurement object. That is to say, the microchannel neutron time-of-flight detector can gate the signal of the neutron time-of-flight spectrum in the time domain by using the time gating function, and has a higher measurement signal-to-noise ratio for a weak signal under strong interference.
Further, as shown in FIG. 2, a secondary electron emission layer 1b and a conductive layer 1c are provided in the channel 1a in an electroplating manner, wherein the conductive layer 1c is ZnO-Al 2 O 3 A thin film capable of replenishing electrons to the secondary electron emission layer 1b after the electrons thereof are consumed; the secondary electron emission layer 1b is Al 2 O 3 Film of Al struck by electrons 2 O 3 When thin films, more electrons are generated.
In order to improve the detection efficiency of fast neutrons, the thickness of the neutron absorber 1 is 1cm or more. In this implementation, the channel 1a of the neutron-absorber 1 does not require gain capability because: the initial electrons in the channel 1a may be generated at any position of the channel, the path of the electrons generated at the front end of the channel 1a is longer in the channel 1a than that of the electrons generated at the back end, and if the electrons have gain in the channel 1a, the amplitude of the signal generated by the neutrons at the front end position is much larger than that at the back end. Therefore, the average secondary electron emission coefficient of the secondary electron emission layer 1b is preferably set to 1 to ensure good uniformity of neutron sensitivity at different positions of the detector.
Further, the microchannel plate 4 made of lead glass is a large-area array electron multiplier device with high spatial resolution, belongs to the existing mature product, and the specific structure and the working principle of the microchannel plate are not repeated herein.
As shown in fig. 3, in order to have higher detection efficiency for neutrons, the channels 1a on the neutron absorber 1 are of a trench-type structure.
As shown in fig. 4, the channels 1a distributed in the neutron absorber 1 may be kidney-shaped holes penetrating the neutron absorber 1 in the thickness direction.
Finally, it should be noted that the above-mentioned description is only a preferred embodiment of the present invention, and that those skilled in the art can make various similar representations without departing from the spirit and scope of the present invention.
Claims (7)
1. A microchannel type fast neutron time-of-flight detector is characterized in that: the device comprises a neutron absorber (1) and an electron collector (2) arranged on one side of the neutron absorber (1), wherein channels (1 a) are distributed in the neutron absorber (1) in an array manner, a secondary electron emission layer (1 b) is arranged on the inner wall of each channel (1 a), each channel (1 a) penetrates through the neutron absorber (1) along the thickness direction, electrodes (3) are respectively arranged on the side faces of the neutron absorber (1) corresponding to the two ends of each channel (1 a), a time-gated pulse high-voltage circuit is loaded between the two electrodes (3) and used for forming an electric field in the channel (1 a), and the direction of the electric field faces towards the electron collector (2);
the secondary electron emission layer (1 b) has an average secondary electron emission coefficient of 1; the channel (1 a) is in a groove type structure which is arranged in a criss-cross mode.
2. The microchannel fast neutron time-of-flight detector of claim 1, wherein: the neutron absorber (1) is made of polyethylene.
3. The microchannel-type fast neutron time-of-flight detector of claim 2, wherein: a microchannel plate (4) is arranged between the neutron absorber (1) and the electron collector (2), the microchannel plate (4) is made of lead glass, and a high-voltage electric field controlled by a time gate control pulse circuit is loaded between the upper side and the lower side of the microchannel plate (4).
4. The microchannel fast neutron time-of-flight detector of claim 1 or 2, wherein: the secondary electron emission layer (1 b) is Al 2 O 3 A film which is provided on the inner wall of the passage (1 a) in an electroplating manner.
5. The microchannel fast neutron time-of-flight detector of claim 1 or 2, wherein: and a conductive layer (1 c) is plated between the neutron absorber (1) and the secondary electron emission layer (1 b).
6. The microchannel fast neutron time-of-flight detector of claim 5, wherein: the conductive layer (1 c) is ZnO-Al 2 O 3 A film.
7. The microchannel fast neutron time-of-flight detector of claim 1, wherein: the thickness of the neutron absorber (1) exceeds 1cm.
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