A microgrid type tissue equivalent proportional counter

Abstract

The application discloses a micro-network type tissue equivalent proportional counter, and relates to the field of radiation measurement. The counter comprises a cathode part, a micro-network electrode, a collector and an anode plate which are sequentially stacked from top to bottom. The cathode part comprises a cathode and an insulating ring. The cathode is a cylinder with a sealed upper surface. The inner side of the cathode is coaxially provided with the insulating ring. The outer wall of the insulating ring is attached to the inner wall of the cathode. The column on the inner side of the insulating ring forms a sensitive space. The micro-network electrode is a circular mesh electrode. The annular lower surface of the cathode is connected to the micro-network electrode through insulating material. The micro-network electrode and the collector have a set interval. The micro-network electrode and the collector are connected through insulating material. The cross section of the insulating material between the micro-network electrode and the collector is annular and coaxial with the lower surface of the cathode. The collector is a conductive electrode on the anode plate. The sensitive space is used to fill tissue equivalent gas. The application reduces the manufacturing cost, improves the performance of the counter and the structural stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radiation measurement, in particular to a micro-network type tissue equivalent proportional counter. BACKGROUND

[0002] Tissue Equivalent Proportional Counter (TEPC) is a kind of detector for evaluating the biological effects of radiation, which is widely used in microdosimetry, radiation therapy and radiation protection research. The traditional TEPC is usually a chamber established around the central anode wire, which measures the absorbed dose and dose equivalent of the measured particle beam by using the gas ionization process in the chamber drift region and the electron avalanche in the avalanche region. It has been widely used in microdosimetry research and application. However, the traditional TEPC has a large chamber size, which limits its research in small size human tissue radiation therapy and protection. When exposed to high flux beams, the traditional TEPC cannot be used due to serious dead time and pile-up effect. To overcome the shortcomings of the traditional TEPC, micro-TEPC with small size sensitive volume has become a popular research direction in the development of TEPC because it can simulate small scale human tissue and has good response to high flux beams.

[0003] There are currently two main ideas for the research of micro-TEPC: reducing the traditional structure of the central anode wire structure and designing a new structure of TEPC with micro-structure gas detector (MPGD). The advantages of anode wire type micro-TEPC are clear design ideas, but the extremely thin anode wire is difficult to manufacture and requires very high process level. At the same time, due to the extremely strong electric field around the anode wire, the stability of the anode wire type micro-TEPC is poor and it is easy to be damaged.

[0004] For micro-TEPC, from the application requirements of microdosimetry, the detector is required to have a compact structure, good energy measurement linearity, high counting rate capability and long-term working stability.

[0005] For example, Figure 2 and Figure 3As shown, the existing mainstream technical solution adopts a central anode wire type, and the micro-TEPC is a cylindrical sensitive volume surrounded by a wall outside a central anode wire. The wall is a cathode, and the chamber is divided into an avalanche region and a drift region according to the field strength: the avalanche region is concentrated around the anode wire, the electric field strength is relatively high, and the avalanche occurs in the region and is collected; the drift region is in a place with relatively low electric field strength outside the avalanche region, and mainly occurs the ionization process of gas molecules under the irradiation of the particle beam to be measured. The central anode wire is extremely thin (generally 10 μm gold-plated tungsten wire), and the processing difficulty is high, and due to the characteristics that the electric field strength is higher near the anode wire, the stability of the high-strength electric field around the anode wire is very poor, and is easily distorted by the processing level of the anode wire.

[0006] The GEM-TEPC structure designed based on the GEM (or THGEM) structure in the MPGD is as shown in Figure 4 The THGEM is a short name of Thick Gas Electron Multiplier, and the Chinese translation is thick gas electron multiplier. In the structure of the GEM, the uppermost is a cathode plate, the middle is a GEM plate, and the drift region is between the two. The GEM plate used is plated with metal electrodes on both sides and is powered to form a high voltage in the holes of the GEM plate, so that the avalanche region is located in the hole gap of the GEM plate. The subsequent collection region is used to collect avalanche electrons.

[0007] Since the avalanche region of the GEM-TEPC is located between the GEM plates, and the signal generated by the collection electrode is all from the avalanche electrons, the positive ions generated in the avalanche process almost do not contribute to the signal. In order to form a strong avalanche electric field in the hole, the GEM plate is made of a certain thickness of insulating material, and the upper and lower surfaces are plated with electrodes. In comparison, the avalanche region of the Micromegas is located between the mesh electrode and the collection electrode, and the positive ions generated in the avalanche process will also generate an induced signal in the process of moving to the mesh electrode, so that the Micromegas has higher single-pole gain and more compact structure.

[0008] In summary, the existing anode wire type TEPC has poor stability, high manufacturing difficulty and high cost, and the GEM-TEPC also has the disadvantages of complex structure and low gain. SUMMARY

[0009] The purpose of the present application is to provide a micro-mesh type tissue equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability.

[0010] To achieve the above purpose, the present application provides the following scheme:

[0011] The micro-network type tissue equivalent proportional counter comprises a cathode part, a micro-network electrode, a collector and an anode plate which are sequentially stacked from top to bottom; the cathode part comprises a cathode and an insulating ring, the cathode is a cylinder with a sealed upper surface, the insulating ring is coaxially arranged on the inner side of the cathode, the outer wall of the insulating ring is attached to the inner wall of the cathode, and the column on the inner side of the insulating ring forms a sensitive space; the micro-network electrode is a circular mesh electrode, the annular lower surface of the cathode is connected with the micro-network electrode through an insulating material; the micro-network electrode and the collector have a set interval, and the micro-network electrode and the collector are connected through an insulating material, the cross section of the insulating material between the micro-network electrode and the collector is an annulus coaxial with the lower surface of the cathode; the collector is a conductive electrode on the anode plate; and the sensitive space is used to fill a tissue equivalent gas.

[0012] Optionally, the tissue equivalent gas comprises a propane-based gas, and the propane-based gas filled into the sensitive space has a gas pressure ranging from 0.01 bar to 1 bar.

[0013] Optionally, the cathode is made of a conductive equivalent material, the conductive equivalent material comprises A-150 equivalent plastic, and the insulating ring is made of an insulating tissue equivalent material, the insulating tissue equivalent material comprises Rexolite 1422 plastic.

[0014] Optionally, the height of the sensitive space ranges from 0.5 mm to 10 mm, and the diameter of the sensitive space ranges from 0.5 mm to 10 mm.

[0015] Optionally, the thickness of the micro-network electrode ranges from 3 microns to 30 microns, the optical transmittance ranges from 30% to 70%, and the gap between the micro-network electrode and the anode plate is not more than 800 microns.

[0016] Optionally, the collector is a conductive film, the collector comprises a germanium-coated film, an aluminum-coated film or a graphite film, and the thickness of the collector is not more than 1 micron.

[0017] Optionally, the anode plate is made of an insulating tissue equivalent material, the insulating tissue equivalent material comprises Rexolite 1422 plastic.

[0018] Optionally, a base is further included, and the anode plate is fixed above the base by crimping or bonding.

[0019] According to the specific embodiments of the present application, the following technical effects are provided:

[0020] The micro-mesh electrode is adopted in the application, compared with the high-intensity electric field of the avalanche area of the traditional anode wire type structure which is easy to break down and distort, the avalanche electric field formed by the micro-mesh electrode is more uniform, so that the micro-mesh type tissue equivalent proportional counter structure of the application is more compact, and the performance and stability are better, and the micro-mesh electrode of the application has lower manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 A micro-mesh type tissue equivalent proportional counter structure of the application is shown in the figure.

[0023] Figure 2 A micro-TEPC with a central anode wire structure is shown in the figure. Figure 1

[0024] Figure 3 A micro-TEPC with a central anode wire structure is shown in the figure. Figure 2

[0025] Figure 4 A GEM-TEPC principle diagram is shown in the figure.

[0026] Symbol explanation:

[0027] Cathode-1, insulating ring-2, micro-mesh electrode-3, collector-4, anode plate-5, base-6, insulating material-7. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] The purpose of the present application is to provide a micro-mesh type tissue equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability.

[0030] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0031] As Figure 1 ​​As shown, the micro-network type tissue equivalent proportional counter disclosed by the application comprises a cathode 1 part, a micro-network electrode 3, a collector 4 and an anode plate 5 which are sequentially stacked from top to bottom; the cathode 1 part comprises the cathode 1 and an insulating ring 2, the cathode 1 is a cylinder with a sealed upper surface, the inner side of the cathode 1 is coaxially provided with the insulating ring 2, the outer wall of the insulating ring 2 is attached to the inner wall of the cathode 1, and the column on the inner side of the insulating ring 2 forms a sensitive space (sensitive volume); the micro-network electrode 3 is a mesh structure electrode, the micro-network electrode 3 is circular, and the annular lower surface of the cathode 1 is connected with the micro-network electrode 3 through an insulating material 7; the micro-network electrode 3 and the collector 4 have a set interval, and the micro-network electrode 3 and the collector 4 are connected through the insulating material 7, and the cross section of the insulating material between the micro-network electrode 3 and the collector 4 is annular and coaxial with the lower surface (annular lower surface) of the cathode 1; the collector 4 is a conductive electrode on the anode plate 5; and the sensitive space is used to fill the tissue equivalent gas.

[0032] The tissue of the application represents human tissue.

[0033] The micro-network electrode 3 and the collector 4 are further provided with an air inlet hole and an air outlet hole, the air inlet hole and the air outlet hole are used to fill the tissue equivalent gas into the cavity between the collector 4 and the cathode 1 part, and the air pressure in the cavity ranges from 0.01 bar to 1 bar.

[0034] The application forms an avalanche gap between the micro-network electrode 3 and the collector 4 plated on the anode plate 5, and this structure can make the cations generated in the avalanche process generate an induced signal on the collector 4 in the process of moving to the micro-network electrode 3, so as to improve the single pole gain. The cathode 1, the insulating material, the anode plate 5, the base 6 and the filled working gas of the application are all made of tissue equivalent materials, which can meet the needs of tissue equivalence in use.

[0035] The tissue equivalent gas is a working gas, and a propane-based gas is adopted.

[0036] The cathode 1 adopts a conductive equivalent material, the conductive equivalent material comprises A-150 equivalent plastic, the insulating ring 2 adopts an insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite1422 plastic.

[0037] The height of the sensitive space is 0.5 mm-10 mm, and the diameter of the sensitive space is 0.5 mm-10 mm.

[0038] The thickness of the micro-network electrode 3 is 3 microns-30 microns, the optical transmittance is 30%-70%, and the gap between the micro-network electrode 3 and the anode plate does not exceed 800 microns.

[0039] The collector 4 is a germanium-coated film, an aluminum-coated film or a graphite film, and the thickness of the collector 4 is not more than 1 micron. The anode plate 5 is made of an insulating tissue equivalent material, and the insulating tissue equivalent material includes Rexolite 1422 plastic.

[0040] The micro-mesh tissue equivalent proportional counter further includes a base 6, and the anode plate 5 is fixed on the base 6 by crimping or bonding to ensure the mechanical strength of the overall structure. The base 6 is made of a conductive equivalent material, and the conductive equivalent material is A-150 equivalent plastic.

[0041] The cathode 1 and the micro-mesh electrode 3 are connected to a voltage dividing circuit, and the voltage dividing circuit is used to increase the voltage of the cathode 1 and the micro-mesh electrode 3. The voltage of the micro-mesh electrode 3 is higher than the voltage of the cathode 1.

[0042] The anode plate 5 is connected to an information acquisition system.

[0043] In order to ensure tissue equivalence and ensure conductivity and insulation respectively, the cathode 1 is directly made of a conductive equivalent plastic (commonly selected, such as A-150 equivalent plastic) or a conductive electrode is made on the lower surface of the cathode 1, and the micro-mesh gaseous detector (including the insulating ring 2) is directly made of an insulating tissue equivalent material (commonly selected, such as Rexolite 1422). The cathode 1 is partially hollowed in the middle part to form a TEPC sensitive volume. The sensitive volume is filled with a tissue equivalent gas (commonly selected, such as a propane-based tissue equivalent gas), and the gas pressure ranges from 0.01 bar to 1 bar, and simultaneously serves as the working gas of the micro-mesh gaseous detector (Micro-Mesh Gaseous Structure, Micromegas).

[0044] The micro-mesh electrode 3 is made of a metal mesh electrode, and is insulated and separated from the cathode 1 above by an insulating tissue equivalent material (commonly selected, such as Rexolite 1422). The metal micro-mesh electrode 3 is usually made of a woven or etched metal mesh with a thickness of 3-30 microns and an optical transmittance of 30%-70%. During the operation of the TEPC, a drift electric field is formed in the sensitive volume between the micro-mesh electrode 3 and the cathode 1 by an external voltage, and is used for the collection of primary ionized charges. An avalanche electric field is formed between the micro-mesh electrode 3 and the collector 4, and is used for the avalanche multiplication of ionized electron signals. The gap between the micro-mesh electrode 3 and the anode is kept in the range of 50-800 microns.

[0045] The size of the collector 4 is not less than the projection area of the sensitive volume on the anode plate 5.

[0046] The micro-network type tissue equivalent proportional counter is a micro-TEPC designed based on a Micromegas detector structure, and the TEPC with the structure overcomes the defects of poor stability, high processing difficulty and high cost of the current anode wire type micro-TEPC. Compared with a GEM type TEPC also belonging to MPGD, the Micromegas type TEPC has higher single-stage gain and a more compact structure, and is more competitive in microdosimetry research, radiation protection and radiation medicine, and the like. More specifically, the Micromegas structure is adopted in the Micromegas type TEPC, and the signal is mainly contributed by cations generated in the avalanche process, so that higher single-stage effective gain can be obtained, which is usually equivalent to that of a three-layer cascaded GEM or THGEM detector, so as to reduce the effective size of the TEPC and improve the working stability of the TEPC.

[0047] The beneficial effects of the present application are as follows.

[0048] 1. The overall structure of the mesh electrode is more stable, and the manufacturing cost is lower; compared with the high-strength electric field of the avalanche region in the anode wire type structure which is easy to break down and distort, the avalanche region electric field of the Micromegas type TEPC is more uniform and controllable.

[0049] 2. The structure of the mesh electrode is more compact, and the single-stage gain is higher: compared with the GEM type TEPC, the GEM plate usually needs a transmission region with a thickness of mm order of magnitude between the GEM plate and the anode for signal sensing and reading out due to the feature that the avalanche region of the GEM plate is located in the hole of the GEM plate, while the Micromegas signal is generated between the mesh and the anode, and is directly sensed and read out, so that the structure is more compact. On the other hand, the single-layer Micromegas can usually achieve high gain of three-layer GEM or THGEM cascade, and the gain and working stability can be further improved by adopting a resistive anode.

[0050] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0051] The principles and implementation modes of the present application are described by applying specific examples in the present application, and the above description of the embodiments is only used to help understand the device of the present application and its core idea; meanwhile, according to the idea of the present application, the specific implementation modes and application ranges will be changed by those skilled in the art. In conclusion, the content of the specification should not be understood as a limitation of the present application.

Claims

1. A micro-lattice type tissue-equivalent proportional counter, characterized by, The micro-mesh tissue equivalent proportional counter comprises a cathode part, a micro-mesh electrode, a collector and an anode plate which are stacked from top to bottom; the cathode part comprises a cathode and an insulating ring, the cathode is a cylinder with a sealed upper surface, the insulating ring is coaxially arranged on the inner side of the cathode, the outer wall of the insulating ring is attached to the inner wall of the cathode, and the column on the inner side of the insulating ring forms a sensitive space; the micro-mesh electrode is a circular mesh electrode, the annular lower surface of the cathode is connected with the micro-mesh electrode through an insulating material; the micro-mesh electrode and the collector have a set interval, and the micro-mesh electrode and the collector are connected through an insulating material, the insulating material between the micro-mesh electrode and the collector is annular and coaxial with the annular lower surface of the cathode; the collector is a conductive electrode on the anode plate; The sensitive space is filled with a tissue equivalent gas; An avalanche gap is formed between the micro-mesh electrode and the collector plated on the anode plate, so that the cations generated in the avalanche process generate an induced signal on the collector during the movement towards the micro-mesh electrode; The cathode and the micro-mesh electrode are connected with a voltage dividing circuit, the voltage dividing circuit is used to increase the voltage of the cathode and the micro-mesh electrode, and the voltage of the micro-mesh electrode is higher than that of the cathode; The micro-mesh tissue equivalent proportional counter further comprises a base, and the anode plate is fixed on the upper side of the base by pressure bonding or adhesion.

2. The micro-lattice tissue-equivalent proportional counter according to claim 1, wherein, The tissue equivalent gas comprises propane-based gas, and the gas pressure of the propane-based gas filled in the sensitive space ranges from 0.05 bar to 1 bar.

3. The micro-lattice tissue-equivalent proportional counter of claim 1, wherein, The cathode adopts conductive equivalent material, the conductive equivalent material comprises A-150 equivalent plastic, the insulating ring adopts insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite 1422 plastic.

4. The micro-lattice tissue-equivalent proportional counter of claim 1, wherein, The height of the sensitive space ranges from 0.5 mm to 10 mm, and the diameter of the sensitive space ranges from 0.5 mm to 10 mm.

5. The micro-lattice tissue-equivalent proportional counter of claim 1, wherein, The thickness of the micro-mesh electrode ranges from 3 μm to 30 μm, the optical transmittance ranges from 30% to 70%, and the gap between the micro-mesh electrode and the anode plate is not more than 800 μm.

6. The micro-lattice tissue-equivalent proportional counter of claim 1, wherein, The collector is a conductive film, the collector comprises a germanium-coated film, an aluminum-coated film or a graphite film, and the thickness of the collector is not more than 1 μm.

7. The micro-lattice tissue-equivalent proportional counter of claim 1, wherein, The anode plate adopts insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite 1422 plastic.

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