Resistive plate chamber detector sensitive to gamma photons

Abstract

A resistive plate chamber detector sensitive to gamma photons comprises an upper readout circuit board, a multilayer resistive glass, an upper carbon film, an upper insulating layer, a photocathode coating, a lower carbon film, a lower readout circuit board and a lower insulating layer; the multilayer resistive glass is arranged below the upper readout circuit board, an air gap is formed between two adjacent layers of resistive glass, and the uppermost resistive glass is lead glass; the upper carbon film is arranged on the upper surface of the lead glass; the upper insulating layer is arranged between the upper readout circuit board and the upper carbon film in the up-down direction; the photocathode coating is arranged on the lower surface of the lead glass; the lower carbon film is arranged on the lower surface of the lowermost resistive glass; the lower readout circuit board is arranged below the lower carbon film; and the lower insulating layer is arranged between the lower readout circuit board and the lower carbon film in the up-down direction. The resistive plate chamber detector sensitive to gamma photons of the present invention has the advantages of high gamma photon detection efficiency and high gamma photon flight time measurement accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of radiation detection, and in particular to a resistive plate chamber detector sensitive to gamma photons. Background Art

[0002] When a positron-electron pair annihilates, a pair of 0.511 MeV gamma photons with the same energy and opposite directions are generated. The location of the electron annihilation can be obtained by detecting the photon pair generated during the annihilation, which is the basic principle of positron emission tomography (PET). The scintillator detector + PMT mode is often used to detect gamma photons, but this method has the disadvantages of being expensive and having insufficient detector time resolution.

[0003] The RPC detector is a gas detector invented by CERN scientists in the early 1980s, and further developed into the MRPC in the 1990s. This type of detector has the advantages of high efficiency (higher than 98%), high time resolution (less than 20ps), excellent position resolution and high cost performance, and has quickly become the first choice for particle time flight devices in large-scale physical experiments.

[0004] Using RPC detectors to detect gamma photons is a promising research. Conventional RPC detectors are often used to detect charged particles such as π, k, p, and muon. However, under normal circumstances, since gamma photons themselves have no charge and are electrically neutral, the detection efficiency of RPC detectors for gamma photons is extremely low (about 0.16%). Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, an embodiment of the present invention provides a resistive plate chamber detector sensitive to gamma photons, comprising an upper readout circuit board, a multilayer resistive glass, an upper carbon film, an upper insulating layer, a photocathode coating, a lower carbon film, a lower readout circuit board and a lower insulating layer;

[0006] The multiple layers of resistive glass are arranged below the upper readout circuit board and are opposite to the upper readout circuit board in the up-down direction. The multiple layers of resistive glass are arranged at intervals in the up-down direction, and an air gap is formed between two adjacent layers of resistive glass. The uppermost layer of resistive glass is lead glass. The upper carbon film is arranged on the upper surface of the lead glass. The upper insulating layer is arranged between the upper readout circuit board and the upper carbon film in the up-down direction. The photocathode coating is arranged on the lower surface of the lead glass. The lower carbon film is arranged on the lower surface of the lowermost layer of resistive glass. The lower readout circuit board is arranged below the lower carbon film and is opposite to the lower carbon film in the up-down direction. The lower insulating layer is arranged between the lower readout circuit board and the lower carbon film in the up-down direction.

[0007] The resistive plate chamber detector sensitive to gamma photons according to the embodiment of the present invention has the advantages of high gamma photon detection efficiency and high gamma photon flight time measurement accuracy.

[0008] In some embodiments, the photocathode coating is a dual-alkali + CsI photocathode coating.

[0009] In some embodiments, the upper readout circuit board includes an upper circuit board and an upper readout strip arranged on the upper circuit board, and the lower readout circuit board includes a lower circuit board and a lower readout strip arranged on the lower circuit board, and the readout direction of the upper readout strip is perpendicular to the readout direction of the lower readout strip.

[0010] In some embodiments, the lead glass contains 25% to 35% lead by mass.

[0011] In some embodiments, the resistive glass is provided as two layers, and the lower layer of the resistive glass is float glass.

[0012] In some embodiments, the width of the air gap is 0.128 mm.

[0013] In some embodiments, the resistive plate chamber detector sensitive to gamma photons according to an embodiment of the present invention further includes a spacer fishing line, which is clamped between two adjacent resistive glasses so as to space the two adjacent resistive glasses apart.

[0014] In some embodiments, each of the upper insulating layer and the lower insulating layer is a Mylar film.

[0015] In some embodiments, the resistive plate chamber detector sensitive to gamma photons according to an embodiment of the present invention further includes an upper honeycomb panel and a lower honeycomb panel, wherein the upper honeycomb panel is arranged above the upper readout circuit board and is opposite to the upper readout circuit board in the up and down directions, and the lower readout circuit board is arranged on the upper surface of the lower honeycomb panel.

[0016] In some embodiments, the upper carbon film is connected to a negative high voltage power source, and the lower carbon film is connected to a positive high voltage power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the cross-sectional structure of a resistive plate chamber detector sensitive to gamma photons according to an embodiment of the present invention.

[0018] Figure numerals: 100, resistive plate chamber detector; 1, upper honeycomb panel; 2, upper circuit board; 3, upper readout strip; 4, upper insulating layer; 5, upper carbon film; 6, lead glass; 7, photocathode coating; 8, air gap; 9, spacer fishing line; 10, float glass; 11, lower honeycomb panel; 12, lower circuit board; 13, lower readout strip; 14, lower insulating layer; 15, lower carbon film. DETAILED DESCRIPTION

[0019] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0020] Reference below Figure 1 A resistive plate chamber detector 100 sensitive to gamma photons according to an embodiment of the present invention is described. The resistive plate chamber detector 100 sensitive to gamma photons according to an embodiment of the present invention comprises an upper readout circuit board, a multilayer resistive glass, an upper carbon film 5, an upper insulating layer 4, a photocathode coating 7, a lower carbon film 15, a lower readout circuit board and a lower insulating layer 14.

[0021] The multilayer resistive glass is arranged below the upper readout circuit board and is opposite to the upper readout circuit board in the up-down direction. The multilayer resistive glass is arranged at intervals in the up-down direction. An air gap 8 is formed between two adjacent layers of resistive glass. The uppermost resistive glass is lead glass 6. The upper carbon film 5 is arranged on the upper surface of the lead glass 6. The upper insulating layer 4 is arranged between the upper readout circuit board and the upper carbon film 5 in the up-down direction.

[0022] The photocathode coating 7 is disposed on the lower surface of the lead glass 6. The lower carbon film 15 is disposed on the lower surface of the lowermost resistive glass. The lower readout circuit board is disposed below the lower carbon film 15 and is vertically opposed to the lower carbon film 15. The lower insulating layer 14 is disposed vertically between the lower readout circuit board and the lower carbon film 15.

[0023] Conventional resistive plate chamber detectors (RPC) are commonly used to detect charged particles such as π, k, p, and muon. However, due to the neutrality of gamma photons, the detection efficiency of conventional RPC is extremely low (0.16%). The common practice in related technologies to improve detection efficiency is to increase the air gap to improve the avalanche amplification effect, or to change the conversion material to convert gamma photons into charged particles as much as possible, but both methods have limitations in improving the detection efficiency of gamma photons.

[0024] In view of this, when the gamma photons are detected by the resistive plate chamber detector 100 sensitive to gamma photons according to the embodiment of the present invention, the gamma photons generated after the annihilation of the positron and the electron sequentially pass through the upper readout circuit board, the upper insulating layer 4, and the upper carbon film 5 to enter the uppermost lead glass 6. Due to the photoelectric effect and the Compton effect, the gamma photons will generate electrons in the lead glass 6. Although only a small part of the electrons generated in the lead glass 6 can escape from the lead glass 6 to the air gap between the multiple layers of resistive glass, most of these electrons will generate Cherenkov light in the lead glass 6, and the Cherenkov light can easily escape from a fixed direction of the lead glass 6. The escaped Cherenkov light directly reaches the surface of the photocathode coating 7. Utilizing the characteristic that the photocathode coating 7 is sensitive to the blue-violet light band, the photocathode coating 7 can convert the Cherenkov light into electrons again. The gamma photons generated in the lead glass 6 and the electrons escaping to the air gap 5 and the electrons converted by the Cherenkov light through the photocathode coating 7 are avalanche-amplified in the high-field strength air gap of the resistive plate chamber detector 100, and then the information of the gamma photons to be detected is obtained from the upper readout circuit board and the lower readout circuit board.

[0025] After research and demonstration, the resistive plate chamber detector 100 sensitive to gamma photons according to the embodiment of the present invention has significantly improved the detection efficiency of gamma photons, and at the same time, the measurement accuracy of the flight time of gamma photons is also significantly improved.

[0026] In view of the low detection efficiency of the RPC detector for neutral particles, but the excellent detection efficiency, excellent time resolution, good position resolution and high cost performance for charged particles, the resistive plate chamber detector 100 sensitive to gamma photons according to the embodiment of the present invention uses lead glass 6 to convert the gamma photons to be measured into electrons through the photoelectric effect and Compton scattering, and then converts the Cherenkov light generated by the electrons in the lead glass 6 into electrons again through the photocathode coating 7 on the lower surface of the lead glass 6. Finally, by utilizing the advantages of RPC for detecting charged particles, the electrons escaping from the lead glass 6 and the electrons converted for the second time by the photocathode coating 7 are avalanche-amplified in the RPC air gap, thereby obtaining the information of the detected gamma photons. That is to say, the resistive plate chamber detector 100 according to the embodiment of the present invention mainly converts the gamma photons into electrons first by an indirect method, and then converts the Cherenkov light emitted by the first converted electrons into electrons for the second time through the photocathode coating 7, so as to improve the detection efficiency of gamma photons, which is different from the principle of improving the detection efficiency of conventional RPC detectors.

[0027] Therefore, the resistive plate chamber detector 100 sensitive to gamma photons according to the embodiment of the present invention has the advantages of high gamma photon detection efficiency and high gamma photon flight time measurement accuracy.

[0028] It should be noted that, through the resistive plate chamber detector 100 of the embodiment of the present invention, the advantages of conventional RPC for charged particle detection can be fully utilized, so that the resistive plate chamber detector 100 of the embodiment of the present invention has very high economic benefits and industrial application prospects. The resistive plate chamber detector 100 sensitive to gamma photons according to the embodiment of the present invention is mainly aimed at positron emission tomography (PET). At present, it uses scintillator + PMT to detect 0.511MeV gamma photon pairs generated by positron-electron annihilation. This detection mode has the disadvantages of high cost and low detection accuracy of photon flight time, which also hinders the further improvement of PET imaging accuracy. The resistive plate chamber detector 100 according to the embodiment of the present invention can significantly reduce the cost of photon detectors in conventional imaging systems, and can improve the positioning accuracy of photon position information.

[0029] Reference below Figure 1 A resistive plate chamber detector 100 sensitive to gamma photons according to an embodiment of the present invention is described in detail.

[0030] According to an embodiment of the present invention, the resistive plate chamber detector 100 sensitive to gamma photons includes an upper readout circuit board, a multilayer resistive glass, an upper carbon film 5, an upper insulating layer 4, a photocathode coating 7, a lower carbon film 15, a lower readout circuit board and a lower insulating layer 14.

[0031] The multilayer resistive glass is arranged below the upper readout circuit board and is opposite to the upper readout circuit board in the vertical direction. The multilayer resistive glass is arranged at intervals in the vertical direction. An air gap 8 is formed between two adjacent layers of resistive glass. The uppermost resistive glass is lead glass 6. The upper carbon film 5 is arranged on the upper surface of the lead glass 6. The upper insulating layer 4 is arranged between the upper readout circuit board and the upper carbon film 5 in the vertical direction. Figure 1 As shown by arrow A in FIG.

[0032] The photocathode coating 7 is disposed on the lower surface of the lead glass 6. The lower carbon film 15 is disposed on the lower surface of the lowermost resistive glass. The lower carbon film cooperates with the upper carbon film to provide the air gap high voltage. The lower readout circuit board is disposed below the lower carbon film 15 and is opposite to the lower carbon film 15 in the vertical direction. The lower insulating layer 14 is disposed between the lower readout circuit board and the lower carbon film 15 in the vertical direction.

[0033] It should be noted that the lead glass 6 is made by adding a certain mass fraction of lead to ordinary resistive glass. The lead glass 6 still has the performance of ordinary resistive glass. Optionally, the lead glass 6 is made by adding a certain mass fraction of lead to float glass.

[0034] Preferably, the photocathode coating 7 is a double alkali + CsI photocathode coating, so that the Cherenkov light converted by the lead glass 6 can be well converted into electrons. Optionally, the photocathode coating 7 is a double alkali + CsI photocathode coating disposed on the lower surface of the lead glass 6.

[0035] like Figure 1 As shown, the upper readout circuit board includes an upper circuit board 2 and an upper readout bar 3 disposed on the upper circuit board 2. The lower readout circuit board includes a lower circuit board 12 and a lower readout bar 13 disposed on the lower circuit board 12. The readout direction of the upper readout bar 3 is perpendicular to the readout direction of the lower readout bar 13. Thus, position readout in one direction of the two-dimensional XY position can be completed on the upper readout circuit board, and position readout in another direction of the two-dimensional XY position can be completed on the lower readout circuit board, so that two-dimensional XY position readout can be completed on a single resistive board chamber detector 100.

[0036] In some embodiments, the lead glass 6 contains lead of 25% to 35% by mass. This ensures that gamma photons are converted into electrons through the photoelectric effect and Compton scattering and that the electrons generate Cherenkov light in the lead glass 6, and also enables the lead glass 6 to have good light transmittance so that the Cherenkov light can pass through the lead glass 6 and reach the surface of the photocathode coating 7. This ensures that the photocathode coating 7 can convert more Cherenkov light into electrons, and further improves the detection efficiency of the gamma photon-sensitive resistive plate chamber detector 100 according to the embodiment of the present invention.

[0037] Preferably, the lead glass 6 contains 30% lead by mass, thereby reliably improving the detection efficiency of the gamma photons by the resistive plate chamber detector sensitive to gamma photons according to the embodiment of the present invention.

[0038] In some embodiments, the resistive glass is provided in two layers, and the lower layer of resistive glass is float glass 10. The float glass 10 has low resistance, good light transmittance and good processability, thereby being able to meet the performance requirements of resistive glass.

[0039] It can be understood that, since the resistive plate chamber detector 100 according to the embodiment of the present invention can greatly improve the detection efficiency of gamma photons, even if the resistive plate chamber detector 100 only includes two layers of resistive glass, electrons enter the air gap 8 between the two layers of resistive glass for avalanche amplification, which can well meet the detection requirements of gamma photons, thereby obtaining information of the gamma photons to be detected. In addition, the resistive glass is set to two layers, which can also reduce the production cost and thickness of the resistive plate chamber detector 100.

[0040] Preferably, the width of the air gap 8 is 0.128 mm. After research and demonstration, the resistive plate chamber detector 100 according to the embodiment of the present invention, which has an air gap of 0.128 mm between adjacent resistive glasses, can have a detection efficiency of nearly 15% for 0.511 MeV gamma photons generated by annihilation of positron-electron pairs. Of course, the resistive plate chamber detector 100 according to the embodiment of the present invention can also detect gamma photons of other energies according to detection requirements.

[0041] like Figure 1 As shown, the gamma photon sensitive resistive plate chamber detector 100 according to the embodiment of the present invention further comprises a spacer fish line 9. The spacer fish line 9 is clamped between two upper and lower adjacent resistive glasses so as to separate the two upper and lower adjacent resistive glasses. Thus, an air gap 8 can be conveniently formed between the two upper and lower adjacent resistive glasses.

[0042] Preferably, each of the upper insulating layer 4 and the lower insulating layer 14 is a Mylar film. The Mylar film has good mechanical flexibility and can reliably ensure the insulation between the upper carbon film and the upper readout circuit board and between the lower carbon film and the lower readout circuit board.

[0043] like Figure 1 As shown, the resistive panel chamber detector 100 sensitive to gamma photons according to an embodiment of the present invention further includes an upper honeycomb panel 1 and a lower honeycomb panel 11. The upper honeycomb panel 1 is arranged above the upper readout circuit board and is opposite to the upper readout circuit board in the up and down direction. The lower readout circuit board is arranged on the upper surface of the lower honeycomb panel 11. Thus, the upper honeycomb panel 1 and the lower honeycomb panel 11 can support other structures in the resistive panel chamber detector 100.

[0044] Preferably, the upper carbon film 5 is connected to a negative high voltage power supply, and the lower carbon film 15 is connected to a positive high voltage power supply. Specifically, the positive and negative high voltages can be positive and negative 704V. This can facilitate the formation of a strong electric field in the multilayer resistive glass between the upper carbon film 5 and the lower carbon film 15, so that the electrons converted by the photocathode coating 7 move from top to bottom in the strong electric field, so that the electrons converted by the photocathode coating 7 can be reliably avalanche-amplified in the air gap, thereby reliably improving the detection efficiency of gamma photons.

[0045] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0047] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0049] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0050] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A resistive plate chamber detector sensitive to gamma photons, characterized in that: include: Upper readout circuit board; A multilayer resistive glass, wherein the multilayer resistive glass is arranged below the upper readout circuit board and is opposite to the upper readout circuit board in the up-down direction, the multilayer resistive glass is arranged at intervals in the up-down direction, an air gap is formed between two adjacent layers of the resistive glass, and the uppermost layer of the resistive glass is lead glass; an upper carbon film, the upper carbon film being disposed on the upper surface of the lead glass; an upper insulating layer, the upper insulating layer being disposed between the upper readout circuit board and the upper carbon film in a vertical direction; a photocathode coating, the photocathode coating being disposed on the lower surface of the lead glass; A lower carbon film, the lower carbon film being arranged on the lower surface of the lowermost resistive glass; A lower readout circuit board, the lower readout circuit board is arranged below the lower carbon film and is opposite to the lower carbon film in the up-down direction; and a lower insulating layer, the lower insulating layer being arranged between the lower readout circuit board and the lower carbon film in a vertical direction; The lead glass converts the gamma photons to be measured into electrons through the photoelectric effect and Compton scattering, and then the photocathode coating on the lower surface of the lead glass converts the Cherenkov light generated in the lead glass into electrons again; The photocathode coating is a double alkali+CsI photocathode coating.

2. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: The upper readout circuit board includes an upper circuit board and an upper readout strip arranged on the upper circuit board, and the lower readout circuit board includes a lower circuit board and a lower readout strip arranged on the lower circuit board. The readout direction of the upper readout strip is perpendicular to the readout direction of the lower readout strip.

3. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: The lead glass contains 25% to 35% lead by mass.

4. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: The resistive glass is provided in two layers, and the lower layer of the resistive glass is float glass.

5. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: The width of the air gap is 0.128 mm.

6. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: It further comprises a spacer fish line, wherein the spacer fish line is clamped between two upper and lower adjacent pieces of the resistive glass so as to space the two upper and lower adjacent pieces of the resistive glass apart.

7. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: Each of the upper insulating layer and the lower insulating layer is a Mylar film.

8. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: It further comprises an upper honeycomb panel and a lower honeycomb panel, wherein the upper honeycomb panel is arranged above the upper readout circuit board and is opposite to the upper readout circuit board in the up and down directions, and the lower readout circuit board is arranged on the upper surface of the lower honeycomb panel.

9. The gamma photon sensitive resistive plate chamber detector according to claim 1, characterized in that: The upper carbon film is connected to a negative high-voltage power supply, and the lower carbon film is connected to a positive high-voltage power supply.

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