CN116013758A - Micro-grid type organization equivalent proportional counter - Google Patents

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

A micro-grid equivalent proportional counter

technical field

The invention relates to the technical field of radiation measurement, in particular to a micro-grid tissue equivalent proportional counter.

Background technique

Tissue Equivalent Proportional Counter (Tissue Equivalent Proportional Counter, TEPC) is a detector widely used in the research of microdosimetry, radiation therapy and radiation protection to evaluate the biological effects of radiation. The traditional TEPC is usually a chamber built around the anode wire located in the center, using the principle of the gas ionization process in the drift region of the chamber and the electron avalanche of the secondary electrons generated in the avalanche region to measure the measured Instruments for particle beam absorbed dose and dose equivalent have been widely used in the research and application of microdosimetry. However, due to the large size of the traditional TEPC chamber, it limits its research on radiation therapy and protection of small-sized human tissues; when irradiated by high-flux beams, the traditional TEPC also suffers from severe dead time and accumulation and cannot be used. In order to overcome the shortcomings of traditional TEPCs, micro-TEPCs with small sensitive volumes have become a hot research direction in the development of TEPCs because of their ability to simulate small-scale human tissues and good response to high-throughput beams.

There are currently two main ideas for the research on micro TEPC: shrinking the traditional structure TEPC with central anode wire structure and designing a new structure TEPC by using Micro-Pattern Gaseous Detector (MPGD). The advantage of the anode wire-type micro-TEPC is that the design idea is relatively clear, but the disadvantage is that it is difficult to manufacture the extremely thin anode wire and requires a very high level of technology; 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 , easily damaged.

For micro TEPC, starting from the application requirements of microbiometrics, 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 Figures 2 and 3, the existing mainstream technical scheme adopts the central anode wire type, and the micro TEPC is a cylindrical sensitive volume surrounded by a central anode wire and a device wall. The wall of the device is the cathode, and the chamber is divided into an avalanche area and a drift area according to the field strength: the avalanche area is concentrated around the anode wire, and the electric field strength is relatively high, and electrons avalanche in this area and are collected; the drift area is outside the avalanche area. In the lower part, the ionization process of gas molecules mainly occurs under the irradiation of the particle beam to be measured. The central anode wire is extremely thin (generally 10μm gold-plated tungsten wire), which is difficult to process, and because the electric field distribution is closer to the anode wire, the stronger the field strength, the stability of the high-strength electric field around the anode wire is very poor. The influence of the level is highly prone to distortion.

The GEM-TEPC structure designed based on the gas electron multiplier (Gas Electron Multiplier, GEM) (or THGEM) structure in MPGD is shown in FIG. 4 . THGEM is the abbreviation of Thick Gas Electron Multiplier, and the Chinese translation is thick gas electron multiplier. In the GEM structure, the cathode plate is at the top, the GEM plate is in the middle, and the drift region is between the two. The two sides of the GEM plate used are plated with metal electrodes and energized separately to form a high voltage in the holes of the GEM plate, so its avalanche area is located in the hole gap of the GEM plate. Then the collection area is used to collect avalanche electrons.

Since the avalanche region of GEM-TEPC is located between the GEM plates, and the signal generated by the collector is all from the avalanche electrons, the positive ions generated during 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 a certain thickness of insulating material, and its upper and lower sides are plated with electrodes. In contrast, the avalanche region of Micromegas is located between the mesh electrode and the collector, where the cations generated during the avalanche process will also generate induction signals during the movement to the mesh electrode, making Micromegas have higher unipolar gain and more compact Structure.

To sum up, the existing anode filament type TEPC has poor stability, is difficult to manufacture and has a high cost, and GEM-TEPC also has the disadvantages of complex structure and low gain.

Contents of the invention

The purpose of the present invention is to provide a micro-grid equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability at the same time.

To achieve the above object, the present invention provides the following scheme:

A micro-mesh type tissue equivalent proportional counter, including a cathode part, a micro-mesh electrode, a collector and an anode plate that are sequentially stacked from top to bottom; the cathode part includes a cathode and an insulating ring, and the cathode is sealed on the 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, and the inner cylinder of the insulating ring forms a sensitive space; the micro-grid electrode It is a circular mesh electrode, and the annular lower surface of the cathode is connected to the micro-grid electrode through an insulating material; there is a set interval between the micro-grid electrode and the collector, and the micro-grid The electrode and the collector are connected by an insulating material, and the cross-section of the insulating material between the micro-grid electrode and the collector is a ring coaxial with the lower surface of the cathode; Conductive electrodes on the anode plate; the sensitive space is used to fill with tissue equivalent gas.

Optionally, the tissue-equivalent gas includes propane-based gas, and the pressure range of the propane-based gas filled into the sensitive space is 0.01 bar-1 bar.

Optionally, the cathode adopts conductive equivalent material, and the conductive equivalent material includes A-150 equivalent plastic, and the insulating ring adopts insulating tissue equivalent material, and the insulating tissue equivalent material includes 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 3-30 microns, the optical transmittance is 30%-70%, and the gap between the micro-grid electrode and the anode plate is no more than 800 microns.

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

Optionally, the anode plate is made of insulating tissue-equivalent material, and the insulating tissue-equivalent material includes Rexolite1422 plastic.

Optionally, a base is also included, and the anode plate is fixed above the base by crimping or bonding.

According to the specific embodiments provided by the invention, the invention discloses the following technical effects:

The present invention adopts the micro-grid electrode. Compared with the high-strength electric field in the avalanche area where the traditional anode wire structure is easy to break down and distort, the avalanche electric field formed by the micro-grid electrode is more uniform, so that the micro-grid structure of the present invention is equivalent to a proportional counter structure It is more compact, has better performance and stability, and the manufacturing cost of the micro-grid electrode of the present invention is lower.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is a schematic diagram of the structure of a micro-grid equivalent proportional counter of the present invention;

Figure 2 is a schematic diagram of a micro-TEPC with a central anode wire structure;

Figure 3 is the second schematic diagram of the micro-TEPC with a central anode wire structure;

Figure 4 is a schematic diagram of the principle of GEM-TEPC;

Symbol Description:

Cathode—1, insulating ring—2, microgrid electrode—3, collector—4, anode plate—5, base—6, insulating material—7.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The purpose of the present invention is to provide a micro-grid equivalent proportional counter, which reduces the manufacturing cost and improves the structural stability at the same time.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a micro-grid tissue equivalent proportional counter disclosed by the present invention includes 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; Part 1 includes a 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 inner wall is attached, and the cylinder inside the insulating ring 2 forms a sensitive space (sensitive volume); the micro-grid electrode 3 is an electrode of a mesh structure, and the micro-grid electrode 3 is circular, and the ring-shaped bottom of the cathode 1 The surface is connected to the micro-grid electrode 3 by an insulating material 7; there is a set interval between the micro-grid electrode 3 and the collector 4, and between the micro-grid electrode 3 and the collector 4 Connected by an insulating material 7, the cross-section of the insulating material between the microgrid electrode 3 and the collector 4 is a coaxial ring with the lower surface (annular lower surface) of the cathode 1; the collector 4 is the conductive electrode on the anode plate 5; the sensitive space is used for filling tissue-equivalent gas.

Tissue according to the present invention means human tissue.

An air inlet and an air outlet are also provided between the micromesh electrode 3 and the collector 4. The air inlet and the air outlet are used to fill the cavity between the collector 4 and the cathode 1 with tissue equivalent gas. The air pressure range in the body is 0.01bar-1bar.

The present invention forms an avalanche gap between the micro-grid electrode 3 and the collector 4 plated on the anode plate 5, and this structure can make the positive ions generated during the avalanche process be generated on the collector 4 during the movement to the micro-grid electrode 3 sense signal, its unipolar gain can be increased. The cathode 1, insulating material, anode plate 5, base 6 and filled working gas of the present invention are all made of tissue-equivalent materials, which can meet the requirement of tissue-equivalent in use.

The tissue-equivalent gas is working gas, and propane-based gas is used.

The cathode 1 adopts conductive equivalent material, and the conductive equivalent material includes A-150 equivalent plastic, and the insulating ring 2 adopts insulating tissue equivalent material, and the insulating tissue equivalent material includes Rexolite1422 plastic .

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

The thickness of the micro-grid electrode 3 is 3 microns-30 microns, the optical transmittance is 30%-70%, and the gap between it and the anode is no more than 800 microns.

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 insulating tissue-equivalent material, and the insulating tissue-equivalent material includes Rexolite1422 plastic.

The micro-mesh tissue equivalent proportional counter of the present invention also includes a base 6, and the anode plate 5 is fixed above the base 6 by crimping or bonding to ensure the mechanical strength of the overall structure. The base 6 is made of conductive equivalent material, specifically A-150 equivalent plastic.

Both the cathode 1 and the microgrid electrode 3 are connected to a voltage divider circuit, and the voltage divider circuit is used to increase the voltage for the cathode 1 and the microgrid electrode 3, and the voltage of the microgrid electrode 3 is higher than that of the cathode 1.

The anode plate 5 is connected with the information collection system.

In the present invention, in order to ensure tissue equivalence and ensure electrical conductivity and insulation respectively, the cathode 1 directly adopts conductive equivalent plastic (commonly selected, such as A-150 equivalent plastic) or makes a conductive electrode on its lower surface, and microgrid The grid gas detector (including the insulating ring 2) directly adopts an insulating tissue equivalent material (commonly selected, such as Rexolite1422), and the middle part of the cathode 1 is hollowed out to form a TEPC sensitive volume. The sensitive volume is filled with tissue-equivalent gas (commonly selected, such as propane-based tissue-equivalent gas), with a pressure range of 0.01bar-1bar, and it is also used as the working gas of the Micro-MeshGaseousStructure, Micromegas.

The micro-grid electrode 3 is an electrode made of metal mesh, and is insulated and isolated from the upper cathode 1 by an equivalent material of insulating tissue (usually selected, such as Rexolite1422). Usually, the metal micro-mesh electrode 3 is made by weaving or etching with a thickness of 3-30 microns and an optical transmittance of 30%-70%. When TEPC is working, the microgrid electrode 3 and the cathode 1 form a drift electric field in the sensitive volume by applying an external voltage, which is used to collect the primary ionized charge, and form an avalanche electric field with the collector 4, which is used for the avalanche multiplication of the ionized electronic signal. The gap between the micro-grid electrode 3 and the anode is kept within 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 .

A micromesh tissue equivalent proportional counter of the present invention is designed based on the micro TEPC of the Micromegas detector structure. The TEPC of this structure overcomes the disadvantages of poor stability, high processing difficulty and high cost of the current anode wire micro TEPC. Moreover, compared with GEM-type TEPC, which also belongs to MPGD, it has higher monopole gain and more compact structure, and is more competitive in microdosimetry research, radiation protection and radiation medicine. More specifically, the present invention adopts a compact Micromegas structure, and the signal is mainly contributed by cations generated in the avalanche process, so a higher unipolar effective gain can be obtained, which is usually equivalent to a three-layer cascaded GEM or THGEM detector, thereby reducing TEPC The effective size and improve its working stability.

The beneficial effects of the present invention are explained as follows.

1. The overall structural stability of the mesh (micro-mesh) electrode is higher, and the production cost is lower; compared with the high-strength electric field in the avalanche area of the anode wire structure, which is easy to break down and easily deformed, the electric field in the avalanche area of Micromegas type TEPC is relatively uniform controllable.

2. The structure of the mesh electrode is more compact, and the unipolar gain is higher: Compared with the GEM type TEPC, the avalanche area of the GEM plate is located in the hole of the GEM plate, and the transmission between the anode and the anode usually requires a thickness of mm order The area is used for signal induction readout, while the Micromegas signal is generated between the microgrid and the anode for direct induction readout, and the structure is more compact. On the other hand, single-layer Micromegas can usually achieve the high gain of cascaded three-layer GEM or THGEM, and the gain and working stability can be further improved by using a resistive anode.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The descriptions of the above embodiments are only used to help understand the device of the present invention and its core idea; meanwhile, for those of ordinary skill in the art, according to the present invention Thoughts, there will be changes in specific implementation methods and application ranges. In summary, the contents of this specification should not be construed as limiting the present 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.

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