JP7466631B2 - Gas electron multipliers, gas photomultipliers and gas X-ray image intensifiers - Google Patents

Description

The present disclosure relates to the field of microstructured gas detectors, and in particular to gas electron multipliers, gas photomultipliers, and gas x-ray image intensifiers.

Microstructured gas detectors (MPGDs), such as microgrid gas detectors (Micromegas), have attracted very wide attention and research due to their unique advantages, such as easy to fabricate in a large sensitive area, good position and time resolution, stable operation in a stronger magnetic field environment, low manufacturing cost, etc. Here, a very valuable application is a new type of photoelectric detector based on MPGDs, which requires the photomultiplier detector to have a high gain of > ¹⁰⁵ and an extremely low positive ion feedback rate (IBFR).

The solutions currently commonly studied at home and abroad are to adopt the mixed structure of many gas detectors, use a gas electron multiplier (GEM or THGEM) with fine holes for pre-amplification, and use Micromegas for two-stage amplification, thereby obtaining a sufficiently high gain for the photon detector readout. However, the mixing of multiple detectors is limited by the structures and characteristic parameters of different detectors, and the relative structure is complicated, and still cannot obtain a satisfactory low IBFR effect. There are two most common mixed structures of gas detectors in the prior art: one is a four-layer GEM cascade connection, in which the middle two layers adopt a sparse hole method to further reduce the IBFR, which can achieve an ion feedback rate of about 0.1%, but the structure is relatively complicated and cannot simultaneously achieve a high gain of about 10 ⁶ of single electron amplification. The other is a single-layer GEM and Micromegas mixed structure, which according to previous reports can only achieve an IBFR of 0.2%.

One aspect of the present disclosure provides a gas electron multiplier, comprising a readout anode plate 1 and a microgrid electrode structure 2 formed by cascading n layers of microgrid electrodes 21 with a support structure 3, the support structure 3 being fixed to the readout anode plate 1, the micropores of the microgrid electrode 21 of the preceding layer being misaligned with the micropores of the microgrid electrode 21 of the layer below, a gas avalanche amplification region being formed between the microgrid electrodes 21, and n being an integer of 3 or more.

Optionally, the thickness of the microgrid electrode 21 is 10-40 microns.

Optionally, the optical transmittance of the microgrid electrode 21 is 30%-70%.

Optionally, the optical transmittance of the microgrid electrode 21 furthest from the readout anode plate 1 is greater than the optical transmittance of the other microgrid electrodes 21.

Optionally, the spacing between the microgrid electrodes 21 is 50-500 microns.

Optionally, the spacing between the microgrid electrodes 21 away from the readout anode plate 1 is greater than the spacing between the microgrid electrodes 21 closer to the readout anode plate 1.

Another aspect of the present disclosure provides a gas photomultiplier based on the above gas electron multiplier, comprising a gas electron multiplier and a photocathode 4, connected to a readout anode plate 1 by a crystalline material, a housing 6 to form a sealed structure, the photocathode 4 being formed in the gas electron multiplier or formed on the inner surface of the crystalline material above the gas electron multiplier, the crystalline material above the gas electron multiplier being an optical window, where a working gas for electron drift and avalanche multiplication is filled inside the sealed structure.

Optionally, the material of the photocathode 4 is cesium iodide, a base or a novel semiconductor material such as gallium arsenide, the crystal material is quartz glass or magnesium fluoride, and the working gas is a mixture of an inert gas and a negative gas.

Another aspect of the present disclosure further provides a gas X-ray image intensifier based on the above gas electron multiplier, comprising a gas electron multiplier and a drift cathode 5, connected to a readout anode plate 1 by an X-ray transparent thin film material and a housing 6 to form a sealed structure, and the X-ray transparent thin film material above the gas electron multiplier is an X-ray transparent window and the above drift cathode 5, where the inside of the sealed structure is filled with a working gas for electron drift and avalanche multiplication.

1 is a schematic diagram of a gas electron multiplier according to an embodiment of the present disclosure; 1 is a schematic diagram of a three-layer micro-grid electrode gas electron multiplier according to an embodiment of the present disclosure; 1 is a schematic diagram showing the structure of a transmission-type gas photomultiplier according to an embodiment of the present disclosure; 1 is a schematic diagram of a structure of a reflection-type gas photomultiplier according to an embodiment of the present disclosure; 1 is a schematic diagram of a gas x-ray image intensifier according to an embodiment of the present disclosure; FIG.

Below, examples of the present disclosure will be described with reference to the drawings. However, it should be understood that these descriptions are merely illustrative and do not limit the scope of the present disclosure. In addition, in the following description, descriptions of known structures and technologies will be omitted to avoid unnecessary confusion of the concepts of the present disclosure.

The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, the terms "a," "one," "an," "the," and the like used herein should include the meaning of "plurality," "multiple kinds," and the like. Additionally, the terms "comprise," "include," and the like used herein indicate the presence of the stated features, steps, operations, and/or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the meanings commonly understood by those of ordinary skill in the art unless otherwise defined. It should be noted that terms used herein should be interpreted to have a meaning consistent with the context of this specification and should not be interpreted in an ideal or stereotypical manner.

Figure 1 is a schematic structural diagram of a gas electron multiplier provided by an embodiment of the present disclosure, which includes a readout anode plate 1 as shown in Figure 1. The microgrid electrode structure 2 is formed by cascading n layers of microgrid electrodes 21 with a support structure 3, and the support structure 3 is fixed to the readout anode plate 1. Here, the micropores of the upper microgrid electrode 21 and the micropores of the lower microgrid electrode 21 are misaligned, forming a gas avalanche amplification region between the microgrid electrodes 21, where n is an integer of 3 or more.

Here, the thickness of the microgrid electrode 21 may be, for example, 10-40 microns, and the optical transmittance may be, for example, 30%-70%. In one embodiment of the present disclosure, the optical transmittance of the microgrid electrode 21 farthest from the readout anode plate 1 is greater than that of the other microgrid electrodes 21, thereby making it possible to lower the ion feedback rate. However, the optical transmittance of the microgrid electrode 21 farthest from the readout anode plate 1 is not greater than that of the other microgrid electrodes 21, and for example, in actual demand, when the requirement for the ion feedback rate is not very high, the optical transmittance of the microgrid electrode 21 farthest from the readout anode plate 1 may be less than or equal to that of the other microgrid electrodes 21, and the specific optical transmittance setting is determined according to actual demand. The interval between the microgrid electrodes 21 may be, for example, 50-500 microns, and the interval between the microgrid electrodes 21 farther from the readout anode plate 1 is greater than the interval between the microgrid electrodes 21 close to the readout anode plate 1. The surface of the microgrid electrode 21 is tensioned to a tension greater than 20 N/cm. The specific parameters of the microgrid electrode 21 are not limited to this disclosure.

Figure 2 is a schematic structural diagram of a gas electron multiplier with a three-layer microgrid electrode provided by an embodiment of the present disclosure. As shown in Figure 2, it includes a readout anode plate 1, and a microgrid electrode structure 2 is formed by cascading three layers of microgrid electrodes 21 (labeled a, b, and c from top to bottom) with a support structure 3, which is fixed to the readout anode plate 1. Here, the microgrid electrode 21 may be, for example, a conductive metal mesh such as stainless steel or copper, and is not specifically limited in the present disclosure.

The thickness of the microgrid electrode 21 is, for example, 10-40 microns, and the optical transmittance (or window opening rate) is, for example, 30%-70%. In general, electrode a uses a thin mesh with a high window opening rate, which allows electrons to easily pass through the mesh and enter the first layer, the gas avalanche pre-amplification region (gap P), improving the electron collection efficiency. Electrodes b and c use a dense mesh type microgrid electrode 21, i.e., a thin mesh with a low window opening rate, which reduces the IBFR.

The micro holes of the three-layer microgrid electrode 21 are offset from each other. Positive ions have a large mass and a slow drift speed, so their motion trajectories do not basically deviate from the electric field lines. Therefore, by adopting the mesh offset method (as shown in FIG. 2), the electric field lines in the avalanche amplification region can be maximized to terminate at the metal mesh, thereby suppressing the positive ions from the third-stage amplification gap M to the second-stage amplification gap S, and from the second-stage amplification gap S to the preliminary amplification gap P. In actual operation, the purpose of mesh offset can be achieved by adopting mesh types with different numbers of pieces and a method of rotating the electrode b relatively at a certain angle.

Unlike the conventional method in which the mesh electrode is the only charge gate (large gap between electrodes, weak electric field, no avalanche amplification), the distance between the microgrid electrodes 21 in this embodiment is very small, for example 50-500 microns. Because of the strong electric field, a sufficiently high tension needs to be applied to the mesh electrodes, typically greater than 20 N/cm. At high tension, the screen is fixed using a high-strength adhesive film of a certain thickness to ensure the flatness of the microgrid electrodes 21.

In this embodiment, three gaps are formed between the three-layer microgrid electrode 21 and the readout anode plate 1, and a high voltage is applied to the electrodes to form a strong electric field in the gaps for use in electron avalanche. The electrons generated by the avalanche can be transferred from the P (S) gap to the S (M) gap, thereby realizing gas cascade multiplication. Therefore, the selection of the gaps and the allocation of the electrode voltages (gap electric field) have a direct impact on IBFR suppression and electron multiplication.

At standard atmospheric pressure, the optimized gap thickness of the single-layer microstructure gas detector is 50-200 microns, and this embodiment adopts a multi-stage cascade structure, and the gap thickness has a wider selection range. To achieve high gain and low IBFR, the pre-amplification region (P) and the second-stage amplification region (S) can adopt a wide gap, which can increase the lateral distribution of electrons and reduce the electron distribution density, and the third-stage amplification region (M) can adopt a narrow gap, which improves the effective gain, thereby ensuring ultra-high total gain and good stability. For other application scenarios, different gap combination methods can be adopted.

Similarly, field allocations are also selected according to different demands, e.g. lowering the IBFR, thereby increasing the M field strength by reducing the P and S field strengths.

This embodiment employs a three-stage cascade-connected microgrid electrode structure 2, and by using a misaligned arrangement method of the microgrid electrodes 21, it is possible to suppress positive ions from the three-stage amplification gap M to the two-stage amplification gap S, and from the gap S to the gap P. By combining the parameters of the microgrid electrode structure 2 (thickness of the microgrid electrodes 21, gap between the microgrid electrodes 21, and light transmittance), it is possible to significantly reduce the IBFR (0.01% or less) and achieve high gain.

Figure 3 is a schematic diagram showing the structure of a transmission-type gas photomultiplier tube according to an embodiment of the present disclosure. As shown in Figure 3, the gas photomultiplier tube (GPMT) includes the gas electron multiplier and photocathode 4 mentioned in the above embodiment.

The gas electron multiplier and photocathode 4 are connected to the readout anode plate 1 by a crystal material and a housing 6 to form a sealed structure, and the photocathode 4 is formed on the inner surface of the crystal material above the gas electron multiplier, and the crystal material above the gas electron multiplier serves as an optical window F, and the inside of the sealed structure is filled with a working gas for electron drift and avalanche multiplication.

The photocathode 4 may be, for example, cesium iodide CsI (ultraviolet), a base or a novel semiconductor material such as gallium arsenide (visible light). The working gas G may be, for example, a mixture of an inert gas (argon, neon, xenon, etc.) and a negative gas (e.g., carbon tetrafluoride, methane, etc.). The crystal material may be, for example, a crystal such as quartz glass or magnesium fluoride. The readout anode plate 1 may be, for example, a ceramic readout plate. The present disclosure is not limited to the specifics.

Figure 4 shows a schematic diagram of a reflection-type gas photomultiplier tube according to an embodiment of the present disclosure. As shown in Figure 4, the gas photomultiplier tube (GPMT) includes the gas electron multiplier and photocathode 4 mentioned in the above embodiment.

The gas electron multiplier and photocathode 4 are connected to the readout anode plate 1 by a crystalline material and a housing 6 to form a sealed structure, the photocathode 4 is formed into a gas electron multiplier, the crystalline material above the gas electron multiplier is the optical window F, and the inside of the sealed structure is filled with a working gas G for electron drift and avalanche multiplication.

The photocathode 4 may be, for example, cesium iodide CsI (ultraviolet), a base or a new semiconductor material such as gallium arsenide (visible light), the working gas G may be, for example, a mixed gas of an inert gas (argon, neon, xenon, etc.) and a negative gas (for example, carbon tetrafluoride, methane, etc.), the crystalline material may be, for example, quartz glass or a crystal such as magnesium fluoride, and the readout anode plate 1 may be, for example, a ceramic readout plate, and the present disclosure is not limited to these.

The GPMT provided by the embodiment of the present disclosure employs the gas electron multiplier provided by the above embodiment, which solves the problem that the photocathode material, which is sensitive to visible light, is easily damaged by ions feedback, and improves gain stability.

Figure 5 is a schematic diagram of a gas X-ray image intensifier according to an embodiment of the present disclosure. As shown in Figure 5, the gas X-ray image intensifier (GXRII) includes the gas electron multiplier and drift electrode 5 mentioned in the above embodiment.

The gas electron multiplier and drift cathode 5 are connected to the readout anode plate 1 by an X-ray transparent thin film material and a housing 6 to form a sealed structure, and the X-ray transparent thin film material above the gas electron multiplier is the X-ray transparent window F' and drift cathode 5. Here, the inside of the sealed structure is filled with a working gas G for electron drift and avalanche multiplication.

The thin film material may be, for example, a metal aluminum film, the working gas G may be, for example, a mixed gas of an inert gas (argon, neon, xenon, etc.) and a negative gas (e.g., carbon tetrafluoride, methane, etc.), and the readout anode plate is a light-transmitting glass with a conductive coating film, which is not specifically limited by the present disclosure. During image collection, a CCD camera or an optical camera is focused on the conductive film plane of the light-transmitting glass to take an image.

The GXRII provided in the embodiment of the present disclosure employs the gas electron multiplier provided in the above embodiment, resulting in a small manufacturing phase difference, a large sensitivity area, a high brightness gain, and improved gain stability.

The specific embodiments described above further explain and understand the objectives, technical solutions and beneficial effects of the present disclosure in detail. The above descriptions are merely specific embodiments of the present disclosure and do not limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure should be included within the scope of protection of the present disclosure.

1--readout anode plate 11--readout anode 2--microgrid electrode structure 21--microgrid electrode 3--support structure 4--photocathode 5--drift electrode 6--housing E--electron drift region F--optical window F'--X-ray transmission window G--working gas

Claims (6)

A readout anode plate (1);
a micro-grid electrode structure (2) formed by cascading n-layer micro-grid electrodes (21) with a support structure (3), the support structure (3) being fixed to the readout anode plate (1);
the micro-holes of the micro-grid electrode (21) of the preceding layer are misaligned with the micro-grid electrode (21) of the underlying layer, and a gas avalanche amplification region is formed between the micro-grid electrodes (21); n is an integer of 3 or more;
The spacing between the microgrid electrodes (21) is 50-500 microns;
A tension of greater than 20 N/cm is applied to the surface of the microgrid electrode (21) ;
The thickness of the microgrid electrode (21) is 10-40 microns;
The optical transmittance of the microgrid electrode (21) is 30%-70%.
Gas electron multiplier. The gas electron multiplier of claim 1, wherein the optical transmittance of the microgrid electrode (21) farthest from the readout anode plate (1) is greater than the optical transmittance of the other microgrid electrodes (21). The gas electron multiplier of claim 1, wherein the spacing between the microgrid electrodes (21) away from the readout anode plate (1) is greater than the spacing between the microgrid electrodes (21) close to the readout anode plate (1). A gas photomultiplier based on the gas electron multiplier according to any one of claims 1 to 3 ,
The gas electron multiplier includes a gas electron multiplier and a photocathode (4), and is connected to the readout anode plate (1) by a crystal material and a housing (6) to form a sealed structure, the photocathode (4) is formed on the gas electron multiplier or on the inner surface of the crystal material above the gas electron multiplier, and the crystal material above the gas electron multiplier serves as an optical window;
Here, the inside of the sealed structure is filled with a working gas for electron drift and avalanche multiplication. the material of the photocathode (4) is cesium iodide, a base or a semiconductor material;
the crystalline material is quartz glass or magnesium fluoride;
5. The gas photomultiplier tube according to claim 4 , wherein said working gas is a mixture of an inert gas and a negative gas. A gas X-ray image intensifier based on the gas electron multiplier according to any one of claims 1 to 3 ,
The gas electron multiplier includes a gas electron multiplier and a drift cathode (5), and is connected to the readout anode plate (1) by an X-ray transparent thin film material and a housing (6) to form a sealed structure, and the X-ray transparent thin film material above the gas electron multiplier is an X-ray transparent window and the drift cathode (5);
Here, the inside of the sealed structure is filled with a working gas for electron drift and avalanche multiplication.

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