CN116013758A - Micro-grid type organization equivalent proportional counter - Google Patents
Micro-grid type organization equivalent proportional counter Download PDFInfo
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- CN116013758A CN116013758A CN202211702508.7A CN202211702508A CN116013758A CN 116013758 A CN116013758 A CN 116013758A CN 202211702508 A CN202211702508 A CN 202211702508A CN 116013758 A CN116013758 A CN 116013758A
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Abstract
The invention discloses a micro-grid type tissue equivalent proportional counter, which relates to the field of radiation measurement, and comprises a cathode part, a micro-grid 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 at the inner side of the cathode, the outer wall of the insulating ring is attached to the inner wall of the cathode, and a sensitive space is formed by a cylinder at the inner side of the insulating ring; the micro-grid electrode is a circular net electrode, and the annular lower surface of the cathode is connected with the micro-grid electrode through an insulating material; the micro-grid electrode and the collector are connected through an insulating material, and the cross section of the insulating material between the micro-grid electrode and the collector is annular coaxial with the lower surface of the cathode; the collector electrode is a conductive electrode on the anode plate; the sensitive space is used for filling the tissue equivalent gas. The invention reduces the manufacturing cost and improves the performance and the structural stability of the counter.
Description
Technical Field
The invention relates to the technical field of radiation measurement, in particular to a micro-grid type tissue equivalent proportional counter.
Background
The tissue equivalent proportional counter (TissueEquivalentProportionalCounter, TEPC) is a detector for evaluating radiation biological effects, which is widely applied to researches in aspects of micro-dosimetry, radiation treatment, radiation protection and the like. Conventional TEPC is generally an instrument for measuring the absorption dose and dose equivalent of a particle beam to be measured, which is currently widely used in micro-dosimetry research and application, by using the principle of gas ionization processes occurring in the drift region of the chamber and electron avalanches occurring in the avalanche region by the generated secondary electrons, around a chamber established by a centrally located anode wire. However, conventional TEPC has limited its research in radiation treatment and protection of small-sized human tissues due to the large size of the chamber; conventional TEPCs are also unusable when exposed to high flux beams due to severe dead time and pile-up effects. To overcome the shortcomings of conventional TEPCs, miniature TEPCs with small-sized sensitive volumes have become a popular research direction for the development of TEPCs today because they have both simulated small-sized human tissue and good response to high-flux beams.
There are currently two main ideas for the study of miniature TEPC: the conventional structure TEPC of the central anode wire structure was scaled down and a new structure TEPC was designed using a Micro-structured gas detector (Micro-PatternGaseous Detector, MPGD). The anode wire type micro-TEPC has the advantages of clear design thought, difficult manufacture of the ultra-fine anode wire and high requirements on the technological level; meanwhile, the anode wire type micro-TEPC has poor stability and is easy to damage due to an extremely strong electric field around the anode wire.
For miniature TEPC, from the application demands of microbiology, the detector is required to have a compact structure, good energy measurement linearity, high count rate capability, and long-term working stability.
As shown in fig. 2 and 3, 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 the central anode wire. The wall is a cathode, and the chamber is divided into an avalanche region and a drift region according to field intensity: the avalanche region is concentrated around the anode wire, the electric field intensity is high, and electrons generate avalanche in the region and are collected; the drift region is located at a place with lower electric field intensity in the avalanche region, and mainly generates ionization process of gas molecules under the irradiation of the particle beam to be detected. The central anode wire is extremely fine (generally 10 mu m gold-plated tungsten wire), the processing difficulty is high, and the high-strength electric field around the anode wire has extremely poor stability due to the characteristic that the field strength is stronger when the electric field distribution is closer to the anode wire, and meanwhile, the high-strength electric field around the anode wire is extremely easy to distort under the influence of the processing level of the anode wire.
The GEM-TEPC structure designed based on the gas electron multiplier (GasElectronMultiplier, GEM) (or THGEM) structure in MPGD is shown in fig. 4. THGEM is Thick GasElectronMultiplier for short, and chinese translation is a thick gas electron multiplier. The top of the GEM structure is a cathode plate, the middle of the GEM structure is a GEM plate, and a drift region is arranged between the GEM plate and the GEM plate. The two sides of the GEM plate are plated with metal electrodes and are electrified to form high voltage in the holes of the GEM plate, so that the avalanche region of the GEM plate is positioned in the hole gaps of the GEM plate. The latter collection region serves to collect avalanche electrons.
Since the avalanche region of the GEM-TEPC is located between the GEM plates and the signal generated by the collector is all derived from avalanche electrons, the cations generated by the avalanche process hardly contribute to the signal. In order to form a strong avalanche electric field in the cavity, the GEM plate is made of insulating material with a certain thickness, and electrodes are plated on the GEM plate. In contrast, the avalanche region of Micromegas is located between the mesh electrode and the collector, wherein positive ions generated in the avalanche process can generate induction signals in the process of moving to the mesh electrode, so that Micromegas has higher monopole gain and a more compact structure.
In summary, the existing anode wire type TEPC has poor stability and high manufacturing difficulty and cost, and GEM-TEPC has the defects of complex structure and low gain.
Disclosure of Invention
The invention aims to provide a micro-grid type tissue equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability.
In order to achieve the above object, the present invention provides the following solutions:
a micro-grid type tissue equivalent proportional counter comprises a cathode part, a micro-grid 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 a sensitive space is formed by a cylinder on the inner side of the insulating ring; the micro-grid electrode is a circular net electrode, and the annular lower surface of the cathode is connected with the micro-grid electrode through an insulating material; the micro-grid electrode and the collector are provided with a set interval, and are connected through an insulating material, and the cross section of the insulating material between the micro-grid electrode and the collector is in a ring shape coaxial with the lower surface of the cathode; the collector is a conductive electrode on the anode plate; the sensitive space is used for filling tissue equivalent gas.
Optionally, the tissue equivalent gas comprises a propane-based gas, and the propane-based gas pressure filling the sensitive space is in the range of 0.01bar to 1bar.
Optionally, the cathode is made of an electrically conductive equivalent material, the electrically conductive equivalent material comprises an A-150 equivalent plastic, the insulating ring is made of an insulating tissue equivalent material, and the insulating tissue equivalent material comprises a Rexolite1422 plastic.
Optionally, 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.
Optionally, the thickness of the micro-grid electrode is 3 micrometers-30 micrometers, the optical light transmittance is 30% -70%, and the gap between the micro-grid electrode and the anode plate is not more than 800 micrometers.
Optionally, the collector is a conductive film, the collector comprises a germanium-plated film, an aluminum-plated film, or a graphite film, and the thickness of the collector is no more than 1 micron.
Optionally, the anode plate is made of an insulating tissue equivalent material, wherein the insulating tissue equivalent material comprises Rexolite1422 plastic.
Optionally, the anode plate further comprises a base, and the anode plate is fixed above the base in a crimping or bonding mode.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
compared with the traditional anode wire-type high-strength electric field in the avalanche region, which is easy to break down and distort, the micro-grid electrode is adopted, and the avalanche electric field formed by the micro-grid electrode is more uniform, so that the micro-grid type tissue equivalent proportional counter is more compact in structure, better in performance and stability, and lower in manufacturing cost.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a micro-grid type structure equivalent proportional counter according to the present invention;
FIG. 2 is a schematic diagram of a micro-TEPC with a central anode wire structure;
FIG. 3 is a schematic diagram of a micro-TEPC with a central anode wire structure;
FIG. 4 is a schematic illustration of the GEM-TEPC principle;
symbol description:
cathode-1, insulating ring-2, micro-grid electrode-3, collector-4, anode plate-5, base-6 and insulating material-7.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a micro-grid type tissue equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in FIG. 1, the micro-grid type tissue equivalent proportional counter disclosed by the invention comprises a cathode 1 part, a micro-grid electrode 3, a collector 4 and an anode plate 5 which are sequentially stacked from top to bottom; the cathode 1 part comprises a cathode 1 and an insulating ring 2, wherein the cathode 1 is a cylinder with a sealed upper surface, the insulating ring 2 is coaxially arranged on the inner side of the cathode 1, the outer wall of the insulating ring 2 is attached to the inner wall of the cathode 1, and a sensitive space (sensitive volume) is formed by a cylinder on the inner side of the insulating ring 2; the micro-grid electrode 3 is an electrode with a net structure, the micro-grid electrode 3 is round, and the annular lower surface of the cathode 1 is connected with the micro-grid electrode 3 through an insulating material 7; a set interval is arranged between the micro-grid electrode 3 and the collector 4, the micro-grid electrode 3 and the collector 4 are connected through an insulating material 7, and the cross section of the insulating material between the micro-grid electrode 3 and the collector 4 is in a ring shape coaxial with the lower surface (annular lower surface) of the cathode 1; the collector 4 is a conductive electrode on the anode plate 5; the sensitive space is used for filling tissue equivalent gas.
The tissue of the present invention represents human tissue.
An air inlet hole and an air outlet hole are also arranged between the micro-grid electrode 3 and the collector 4, the air inlet hole and the air outlet hole are used for filling tissue equivalent gas into a cavity between the collector 4 and the cathode 1, and the air pressure in the cavity ranges from 0.01bar to 1bar.
The invention forms an avalanche gap between the micro-grid electrode 3 and the collector 4 plated on the anode plate 5, and the structure can lead positive ions generated in the avalanche process to generate induction signals on the collector 4 in the process of moving to the micro-grid electrode 3, thereby improving the monopole gain. The cathode 1, the insulating material, the anode plate 5, the base 6 and the filled working gas are all made of tissue equivalent materials, so that the requirement of tissue equivalent in use can be met.
The tissue equivalent gas is working gas, and propane-based gas is adopted.
The cathode 1 is made of an electrically conductive equivalent material, the electrically conductive equivalent material comprises A-150 equivalent plastic, the insulating ring 2 is made of an insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite1422 plastic.
The height of the sensitive space is 0.5-10 mm, and the diameter of the sensitive space is 0.5-10 mm.
The thickness of the micro-grid electrode 3 is 3-30 microns, the optical transmittance is 30-70%, and the gap between the micro-grid electrode and the anode is not more than 800 microns.
The collector 4 is a germanium-plated film, an aluminum-plated film or a graphite film, and the thickness of the collector 4 is not more than 1 micrometer. The anode plate 5 is made of an insulating tissue equivalent material, wherein the insulating tissue equivalent material comprises Rexolite1422 plastic.
The micro-grid type tissue equivalent proportional counter also comprises a base 6, wherein the anode plate 5 is fixed above the base 6 in a pressure welding or bonding mode so as to ensure the mechanical strength of the whole structure. The base 6 is made of conductive equivalent materials, in particular to A-150 equivalent plastics.
The cathode 1 and the micro-grid electrode 3 are connected with a voltage dividing circuit, and the voltage dividing circuit is used for increasing the voltage of the cathode 1 and the micro-grid electrode 3, and the voltage of the micro-grid electrode 3 is higher than the voltage of the cathode 1.
The anode plate 5 is connected with an information acquisition system.
In order to ensure tissue equivalence and conductivity and insulativity respectively, the cathode 1 is directly made of conductive equivalent plastic (commonly selected as A-150 equivalent plastic) or a conductive electrode is manufactured on the lower surface of the cathode, the micro-grid gas detector (comprising an insulating ring 2) is directly made of insulating tissue equivalent material (commonly selected as Rexolite 1422), and the middle part of the cathode 1 is hollowed out to form a TEPC sensitive volume. The sensitive volume is filled with a tissue equivalent gas (usually chosen as propane-based tissue equivalent gas) at a pressure in the range of 0.01bar-1bar and as working gas for a Micro grid gas detector (Micro-Mesh GaseousStructure, micromegas).
The micro-grid electrode 3 is an electrode made of a metal grid, and is insulated and isolated from the cathode 1 above by an insulating tissue equivalent material (commonly selected as Rexolite 1422). The metal micro-grid electrode 3 is usually manufactured by braiding or etching with the thickness of 3-30 microns and the optical transmittance of 30% -70%. When the TEPC works, through an applied voltage, the micro-grid electrode 3 and the cathode 1 form a drift electric field in a sensitive volume, so as to collect primary ionized charges, and form an avalanche electric field with the collector 4, so as to multiply the avalanche of ionized electronic signals. The gap between the micro-grid electrode 3 and the anode is maintained in the range of 50-800 microns.
The size of the collector 4 is not smaller than the projected area of the sensitive volume on the anode plate 5.
The micro-grid type tissue equivalent proportional counter is designed based on micro-TEPC of a micro-megas detector structure, and the TEPC of the structure overcomes the defects of poor stability, high processing difficulty and high cost of the existing anode wire type micro-TEPC. Compared with GEM type TEPC which belongs to MPGD, the device has higher monopole gain and more compact structure, and has more competitive power in aspects of micro-dosimetry research, radiation protection, radiation medical treatment and the like. More specifically, the invention adopts a compact Micromegas structure, and the signal is mainly contributed by cations generated in the avalanche process, so that higher monopole effective gain can be obtained, which is generally equivalent to a three-layer cascade GEM or THGEM detector, thereby reducing the effective size of the TEPC and improving the working stability of the TEPC.
The beneficial effects of the invention are described below.
1. The overall structure stability of the mesh (micro-grid) electrode is higher, and the manufacturing cost is lower; compared with the high-strength electric field of the avalanche region which is easy to break down and distort in the anode wire type structure, the electric field of the avalanche region of the Micromegas-type TEPC is more uniform and controllable.
2. The structure of the mesh electrode is more compact, and the monopole gain is higher: compared with GEM-type TEPC, the GEM plate generally needs a transmission area with the thickness of the order of mm between the GEM plate and the anode due to the characteristic that the avalanche area is positioned in the hole of the GEM plate, so that the GEM plate is used for signal sensing and reading, and Micromegas signals are generated between a micro-grid and the anode, and the GEM plate is used for direct sensing and reading, so that the structure is more compact. On the other hand, single-layer Micromegas can generally achieve high gain of three-layer GEM or THGEM cascade, and gain and working stability can be further improved by adopting a resistive anode method.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the above examples being provided only to assist in understanding the device and its core ideas of the present invention; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (8)
1. The micro-grid type tissue equivalent proportional counter is characterized by comprising a cathode part, a micro-grid 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 a sensitive space is formed by a cylinder on the inner side of the insulating ring; the micro-grid electrode is a circular net electrode, and the annular lower surface of the cathode is connected with the micro-grid electrode through an insulating material; the micro-grid electrode and the collector are provided with a set interval, and are connected through an insulating material, and the cross section of the insulating material between the micro-grid electrode and the collector is in a ring shape coaxial with the lower surface of the cathode; the collector is a conductive electrode on the anode plate; the sensitive space is used for filling tissue equivalent gas.
2. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein the tissue equivalent gas comprises a propane-based gas, and the pressure of the propane-based gas filled into the sensitive space is in the range of 0.01bar to 1bar.
3. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein the cathode is made of a conductive equivalent material, the conductive equivalent material comprises a-150 equivalent plastic, the insulating ring is made of an insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite1422 plastic.
4. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein 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.
5. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein the thickness of the micro-grid electrode is 3 micrometers-30 micrometers, the optical transmittance is 30% -70%, and the gap between the micro-grid electrode and the anode plate is not more than 800 micrometers.
6. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein the collector is a conductive film, the collector comprises a germanium-plated film, an aluminum-plated film or a graphite film, and the thickness of the collector is not more than 1 micron.
7. The micro-grid type tissue equivalent proportional counter according to claim 1, wherein the anode plate is made of an insulating tissue equivalent material, and the insulating tissue equivalent material comprises Rexolite1422 plastic.
8. The micro-grid type tissue equivalent proportional counter according to claim 1, further comprising a base, wherein the anode plate is fixed above the base by crimping or bonding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211702508.7A CN116013758A (en) | 2022-12-29 | 2022-12-29 | Micro-grid type organization equivalent proportional counter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211702508.7A CN116013758A (en) | 2022-12-29 | 2022-12-29 | Micro-grid type organization equivalent proportional counter |
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| CN116013758A true CN116013758A (en) | 2023-04-25 |
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| CN202211702508.7A Pending CN116013758A (en) | 2022-12-29 | 2022-12-29 | Micro-grid type organization equivalent proportional counter |
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- 2022-12-29 CN CN202211702508.7A patent/CN116013758A/en active Pending
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