A flat ionization chamber for leakage radiation measurements

Abstract

The application discloses a flat ionization chamber for leakage radiation measurement and relates to the technical field of ionization chambers, comprising a high-voltage electrode, a collecting electrode, a protection electrode and a main body frame, a hollow cavity is arranged in the main body frame, two high-voltage electrodes are detachably connected to the two end faces of the main body frame, the hollow cavity and the high-voltage electrode form a sealed ionization cavity, the high-voltage electrode, the collecting electrode and the protection electrode can conduct electricity, the protection electrode is arranged in the ionization cavity, the collecting electrode is arranged in the protection electrode, the collecting electrode is not in contact with the protection electrode, the outer conductive layer of the cable is electrically connected with the high-voltage electrode, the shielding conductive layer is electrically connected with the protection electrode, and the conductive core is electrically connected with the collecting electrode. The ionization chamber adopts a double-layer flat plate type structure, the distance between the high-voltage electrode and the collecting electrode can be reduced, the ionization chamber has the ability of detecting ms-level pulse radiation fields, the high-voltage electrode and the collecting electrode are isolated by the protection electrode, a too thick insulating layer is not needed between the two stages, the generation of leakage current is greatly reduced, and the ionization chamber structure is more simple.

Description

Technical Field

[0001] This invention relates to the technical field of ionization chambers, and in particular to a flat plate ionization chamber for measuring leakage rays. Background Technology

[0002] With the continuous development of radiotherapy technology, radiotherapy has become an indispensable treatment method in modern medical examinations for tumor treatment. The radiation sources used in radiotherapy mainly fall into three categories: alpha, beta, and gamma rays produced by radioactive isotopes; X-rays of different energies produced by X-ray therapy machines and various accelerators; and electron beams, proton beams, neutron beams, negative pion beams, and other heavy ion beams produced by various accelerators.

[0003] Medical linear accelerators are particle accelerator devices that generate high-energy X-rays and electron beams for radiotherapy of tumors. Due to their wide range of applications and good therapeutic effects, they are widely used. To reduce the failure rate and radiation leakage of medical linear accelerators, regular inspection using dosimeters is essential. In the applications of X-ray machines, medical diagnostics, and gamma irradiation devices, the harm of leaked radiation to human health is receiving increasing attention. Accurate measurement, monitoring, and early warning of leaked radiation are fundamental guarantees for the safe operation of irradiation devices.

[0004] A flat-plate ionization chamber, also known as an X-ray detector, works by bombarding the air with X-rays, ionizing it, and then collecting the charged ions under a high-voltage electric field to generate a weak current. This current signal is used to detect the quality of medical linear accelerators. However, conventional protective instruments often lack both good energy response and accurate pulsed radiation field dose measurement, and their application costs are relatively high. Therefore, to ensure radiation safety for personnel and the working environment, it is necessary to develop a flat-plate ionization chamber for measuring leakage radiation. Summary of the Invention

[0005] The purpose of this invention is to provide a flat-plate ionization chamber for measuring leakage radiation, thereby solving the problems existing in the prior art, making the ionization chamber have good energy response and high accuracy in pulsed radiation field dose measurement.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a flat-plate ionization chamber for measuring leakage radiation, comprising a high-voltage electrode, a collecting electrode, a protective electrode, and a main frame. The main frame has a hollow cavity inside. Both the high-voltage electrode and the collecting electrode are plate-shaped. The main frame is made of insulating material. Both high-voltage electrodes are detachably connected to the two end faces of the main frame. The hollow cavity and the high-voltage electrodes form a sealed ionization chamber. The high-voltage electrode, the collecting electrode, and the protective electrode are all conductive. The protective electrode is disposed within the ionization chamber, and the collecting electrode is disposed within the protective electrode. The high-voltage electrode and the collecting electrode are arranged parallel to each other, and the collecting electrode and the protective electrode are not in contact. The outer conductive layer of the cable is electrically connected to the high-voltage electrode, the shielding conductive layer is electrically connected to the protective electrode, and the conductive core is electrically connected to the collecting electrode. The cable is used to connect to a dosimeter.

[0008] Preferably, the high-voltage electrode is connected to the main frame by bolts, and two through holes are provided on one side of the hollow cavity of the main frame. A connector is provided on the side wall of one of the through holes, and the connector is electrically connected to the cable.

[0009] Preferably, a vertical conductive groove is provided in the hollow cavity of the main frame, and the two high-voltage electrodes are electrically connected through the conductive layer in the conductive groove. A wire groove is provided between the through hole and the hollow cavity, and a pressure plate is connected to the wire groove by bolts.

[0010] Preferably, the protective electrode includes a pair of opposing rectangular frames, and a plurality of insertion half-grooves are arranged opposite each other on the mating surface of the rectangular frames. The insertion half-grooves can be spliced ​​to form an insertion slot. An insulating gasket is inserted into the insertion slot, and the collecting electrode is connected to the insulating gasket. The collecting electrode is arranged at equal intervals with the inner wall of the rectangular frame.

[0011] Preferably, a stepped hole is provided in the hollow cavity of the main frame, the protective electrode is snapped onto the step of the stepped hole, and a clamping frame is provided between the upper part of the protective electrode and the high voltage electrode. The clamping frame is made of insulating material and is used to clamp the protective electrode.

[0012] Preferably, the protective electrode is made of an air-equivalent material, and a conductive layer is provided on the inner wall of the protective electrode and the bonding surface. The conductive layer is connected to the shielding conductive layer by pressing.

[0013] Preferably, the high-voltage electrode is made of an air-equivalent material, the thickness of the high-voltage electrode constituting the ionization cavity is 0.5mm-2mm, and all surfaces of the high-voltage electrode are provided with a conductive layer.

[0014] Preferably, the collecting electrode is made of an air equivalent material with a thickness of 0.5mm-2mm. All surfaces of the air equivalent material are provided with a conductive layer, and aluminum foil is attached to the conductive layer. The conductive core of the cable is bonded to the conductive layer with conductive graphite adhesive.

[0015] Preferably, the outer surface of the box structure formed by the high-voltage electrode and the main frame is provided with a conductive layer, and the materials of the high-voltage electrode and the main frame are air equivalent material, metal or metal alloy. The conductive layer provided on the upper and lower surfaces of the main frame can be connected to the outer conductive layer of the cable.

[0016] Preferably, the air equivalent material is plexiglass.

[0017] Preferably, the conductive layer is sprayed graphite.

[0018] Preferably, a protective layer is provided outside the conductive layer, and the protective layer is sprayed paint.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] The ionization chamber of this invention adopts a double-layer flat plate structure, which can reduce the distance between the plates of the high-voltage electrode and the collecting electrode, resulting in a shorter collection time and the ability to detect pulse radiation fields at the millisecond level. The use of a protective electrode to isolate the high-voltage electrode and the collecting electrode eliminates the need for a thick insulation layer between the two electrodes, greatly reducing leakage current and making the ionization chamber structure simpler. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is an exploded structural diagram of the flat plate ionization chamber used for leakage radiation measurement in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the internal structure of the flat plate ionization chamber used for leakage radiation measurement in an embodiment of the present invention;

[0024] Figure 3 This is a schematic cross-sectional view of the flat plate ionization chamber used for leakage radiation measurement in an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram of the main frame structure in an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of a flat-plate ionization chamber used for leakage radiation measurement in an embodiment of the present invention;

[0027] Wherein: 1-High voltage electrode, 2-Collecting electrode, 3-Protective electrode, 4-Main frame, 5-Pressure frame, 6-Hollow cavity, 7-Through hole, 8-Connector, 9-Conductive groove, 10-Wire groove, 11-Fill plate, 12-Bolt, 13-Insulating gasket, 14-Ionization chamber, 100-Plate ionization chamber for leakage radiation measurement. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The purpose of this invention is to provide a flat-plate ionization chamber for measuring leakage radiation, so as to solve the problems existing in the prior art, so that the ionization chamber has good energy response and high accuracy in pulsed radiation field dose measurement.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figures 1 to 5 As shown: This embodiment provides a flat ionization chamber 100 for measuring leakage radiation, including a high-voltage electrode 1, a collecting electrode 2, a protective electrode 3, and a main frame 4. The main frame 4 has a hollow cavity 6 inside. The high-voltage electrode 1 and the collecting electrode 2 are both plate-shaped. The main frame 4 is made of insulating material. Both high-voltage electrodes 1 are detachably connected to the two end faces of the main frame 4. The hollow cavity 6 and the high-voltage electrode 1 form a sealed ionization chamber 14 (sensitive volume). The high-voltage electrode 1, the collecting electrode 2, and the protective electrode 3 are all conductive. The protective electrode 3 is disposed inside the ionization chamber 14, and the collecting electrode 2 is disposed inside the protective electrode 3. The high-voltage electrode 1 and the collecting electrode 2 are arranged in parallel. The collecting electrode 2 and the protective electrode 3 do not contact each other. The outer conductive layer of the cable is electrically connected to the high-voltage electrode 1, the shielding conductive layer is electrically connected to the protective electrode 3, and the conductive core is electrically connected to the collecting electrode 2. The cable is used to connect to a dosimeter. The main function of high voltage electrode 1 is to provide the working voltage of the ionization chamber and form an electric field with collecting electrode 2 to collect ionized charges. The main function of collecting electrode 2 is to collect ionized charges generated by radiation in the sensitive area formed by high voltage electrode 1 and collecting electrode 2 in the ionization chamber. The main function of protective electrode 3 is to isolate high voltage electrode 1 and collecting electrode 2, preventing leakage current from high voltage electrode 1 to collecting electrode 2 through the insulation layer. Protective electrode 3 and collecting electrode 2 have the same potential, and the thickness of the insulation layer of each electrode can be greatly reduced through shielding protection.

[0032] As an optional solution, in this embodiment, the high-voltage electrode 1 and the main frame 4 are connected by bolts 12. Two through holes 7 are also provided on one side of the hollow cavity 6 of the main frame 4. A connector 8 is provided on the side wall of one of the through holes 7. One end of the connector 8 is connected to an external power supply, and the other end is electrically connected to an internal cable. Both through holes 7 can be used for wiring, and their symmetrical arrangement reduces interference from scattered radiation from the physical object on the measurement. This embodiment adopts a double-layer flat plate structure, which allows for a smaller distance between the plates of the high-voltage electrode 1 and the collecting electrode 4, resulting in a shorter collection time and the ability to detect pulsed radiation fields at the millisecond level.

[0033] As an optional solution, in this embodiment, a vertical conductive groove 9 is provided in the hollow cavity 6 of the main frame 4. The two high-voltage electrodes 1 are electrically connected through the conductive layer (sprayed graphite layer) in the conductive groove 9. The clamping frame 5, the collecting electrode 2 and the protective electrode 3 are provided with clearance grooves opposite to the conductive groove 9 to avoid conduction with the high-voltage electrode 1 through the conductive layer. The connection structure is simple and convenient. A wire groove 10 is provided between the through hole 7 and the hollow cavity 6. A pressure plate 11 is connected to the wire groove 10 by bolts 12. There are no exposed wires, which can effectively ensure a large sensitive volume.

[0034] As an optional solution, in this embodiment, the protective electrode 3 includes a pair of relatively fitted rectangular frames. Several insertion half-grooves are arranged opposite each other on the mating surfaces of the rectangular frames. These insertion half-grooves can be spliced ​​together to form an insertion slot. An insulating gasket 13 is inserted into the insertion slot, and a collecting electrode 2 is connected to the insulating gasket 13. An insertion slot is provided on one side of the insulating gasket 13, and the collecting electrode 2 is inserted into the insertion slot for fixation, parallel to the two high-voltage electrodes 1. The collecting electrode 2 is evenly spaced from the inner wall of the rectangular frame. Alternatively, the protective electrode 3 can be a single unit with an internal stepped groove. The collecting electrode 2 is connected to the stepped groove via the insulating gasket 13. The collecting electrode 2 is supported and kept level by the insulating gasket 13, forming an isolation between it and the protective frame.

[0035] As an optional solution, in this embodiment, a stepped hole is provided in the hollow cavity of the main frame 4. The lower part of the protective electrode 3 is snapped onto the step of the stepped hole, and a clamping frame 5 is provided between the upper part of the protective electrode 3 and the high-voltage electrode 1. The clamping frame 5 is made of insulating material, and its height fills the gap between the protective electrode 3 and the high-voltage electrode 1, thereby clamping the protective electrode 3 and the insulating gasket 13 to ensure stable support for the collecting electrode 2. Since the most critical aspects of ionization chamber design are reducing leakage current and energy response consistency, the collection time of the ionization chamber also needs to be considered to meet the testing requirements of pulsed radiation fields. The shorter the collection time of the ionization chamber, the faster the response to the pulse signal, which can greatly reduce the interference of charged ion coincidence on the measurement signal and improve the measurement accuracy. Therefore, compared with cylindrical and spherical structures, the electrode spacing of a plate-shaped ionization chamber is generally closer, making it more suitable for detecting pulsed radiation fields. This embodiment adopts a double-layer plate-type structure, and the height of the insulating clamping frame 5 can be set according to the radiation measurement in the scenario to better adapt to the detection requirements of pulsed radiation fields.

[0036] As an optional solution, in this embodiment, the protective electrode 3 is made of air equivalent material. The inner wall and the bonding surface of the protective electrode 3 are provided with conductive layers. The conductive layers are connected to the shielding conductive layer by pressing, thereby achieving conductivity and forming isolation between the collecting electrode 2 and the high voltage electrode 1.

[0037] As an optional solution, in this embodiment, the high-voltage electrode 1 uses an air-equivalent material. The thickness of the high-voltage electrode 1 forming the ionization cavity is 0.5mm-2mm, preferably about 1mm. All surfaces of the high-voltage electrode 1 are provided with a conductive layer, which forms a shielding layer with the conductive layer on the main frame 4 and also serves to conduct electricity. The high-voltage electrode 1 has a groove located in the sensitive area to facilitate the penetration of the pulse radiation field, making the electrode plate flatter and ensuring the thickness of the fixed edge of the plexiglass so as not to be too thin and deformed.

[0038] As an optional solution, in this embodiment, the collecting electrode 2 uses an air equivalent material with a thickness of 0.5mm-2mm, preferably about 1.5mm, to ensure good radiation penetration and energy response. All surfaces of the air equivalent material are provided with a conductive layer, and aluminum foil is attached to the conductive layer. The aluminum foil, together with the graphite material, can improve the incomplete air equivalence of the ionization chamber electrode material. By absorbing and scattering, the energy response can be improved, and the purpose of energy response consistency can be achieved. The conductive core of the cable is bonded to the conductive layer with conductive graphite adhesive. Other connection methods can also be used, such as installing connector 8.

[0039] As an optional solution, in this embodiment, a conductive layer is provided on the outer surface of the box structure composed of the high-voltage electrode 1 and the main frame 4. A graphite conductive layer is uniformly sprayed onto the outer surface of the ionization chamber box, and this conductive layer is connected to the high-voltage electrode 1 as a shielding layer. This effectively reduces the interference of external electromagnetic fields on the measurement signal and improves measurement stability. The high-voltage electrode 1 and the main frame 4 are made of air-equivalent material, metal, or metal alloy. The conductive layers on the upper and lower surfaces of the main frame 4 can be connected to the outer conductive layer of the cable. The two high-voltage electrodes 1 are connected by internal wires and pressed tightly to the main frame 4 by screws. The conductive layers on the high-voltage electrode 1 and the main frame 4 achieve conductivity through contact. The graphite conductive layers on the upper and lower surfaces of the main frame 4 are connected to the outermost layer of the external connector 8, thus enabling both high-voltage electrodes 1 to be electrically connected to the dosimeter.

[0040] As an optional solution, in this embodiment, the air equivalent material is plexiglass; the conductive layer is sprayed graphite. Plexiglass and graphite, as air equivalent materials, are excellent materials for making ionization chambers. They have approximately the same absorption coefficient for primary radiation as air and approximately the same atomic blocking ability for secondary electrons, and their physical properties are robust, durable, and stable.

[0041] As an optional solution, a protective layer is provided outside the conductive layer in this embodiment. The protective layer is sprayed paint, which can effectively prevent scratches on the graphite layer.

[0042] The specific working principle of the flat-plate ionization chamber 100 for leakage radiation measurement in this embodiment is as follows: The ionization chamber is a gas detector that uses air as the medium and operates in the saturation region. When the particle being measured passes through the working medium of the detector's sensitive volume, Coulomb scattering causes electrons in the atoms of the working medium to ionize, directly forming charges. The electrons and positive ions generated by ionization move in opposite directions, either along or against the direction of the spatial electric field, and are finally collected by the collecting electrode 2. One electrode connected to the recording instrument is called the collecting electrode 2 (center electrode), which is grounded through a load resistor; the other electrode is supplied with a voltage of several hundred to several thousand volts and is called the high-voltage electrode 1 (anode); between the collecting electrode and the high-voltage electrode, there is a protective electrode 3 (protective ring), whose potential is the same as the collecting electrode. The protective ring is separated from the high-voltage electrode 1 and the collecting electrode 2 by an insulator. The function of the protective ring is to prevent the leakage current from the high-voltage electrode to ground from passing through the collecting electrode and to keep the electric field at the edge of the collecting electrode uniform without distortion, thus ensuring a defined sensitive volume for the ionization chamber. Without recombination and diffusion losses, all ion pairs formed within the sensitive volume will be collected by both the high-voltage electrode 1 and the collecting electrode 2. Under electron equilibrium conditions, almost all the energy deposited by the radiation in the cavity is used to excite the ionization of gas molecules within the cavity. The ionization charge output by the ionization chamber is the total charge generated by the ionization of gas molecules in the cavity. Therefore, the dose of the radiation field can be determined by detecting the current on the cable using a recording instrument and converting it into digital parameters. This embodiment achieves key technical indicators such as wide energy response with good consistency, low leakage current, and short response time.

[0043] This specification uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A flat-plate ionization chamber for measuring leakage rays, characterized in that: The device includes a high-voltage electrode, a collecting electrode, a protective electrode, and a main frame. The main frame has an internal cavity. Both the high-voltage electrode and the collecting electrode are plate-shaped. The main frame is made of insulating material. Both high-voltage electrodes are detachably connected to the two end faces of the main frame. The cavity and the high-voltage electrode form a sealed ionization cavity. The high-voltage electrode, collecting electrode, and protective electrode are all conductive. The protective electrode is located within the ionization cavity, and the collecting electrode is located within the protective electrode. The protective electrode and the collecting electrode are at the same potential. The high-voltage electrode and the collecting electrode are arranged parallel to each other. The collecting electrode and the protective electrode are not in contact. The outer conductive layer of the cable is electrically connected to the high-voltage electrode, the shielding conductive layer is electrically connected to the protective electrode, and the conductive core is electrically connected to the collecting electrode. The cable is used to connect to a dosimeter. The protective electrode includes a pair of rectangular frames that fit together. Several insertion half-grooves are arranged opposite each other on the mating surfaces of the rectangular frames. The insertion half-grooves can be spliced ​​together to form an insertion slot. An insulating gasket is inserted into the insertion slot. The collecting electrode is connected to the insulating gasket. The collecting electrode is arranged at equal intervals with the inner wall of the rectangular frame. The hollow cavity of the main frame is provided with a stepped hole. The protective electrode is snapped onto the step of the stepped hole. A clamping frame is provided between the upper part of the protective electrode and the high voltage electrode. The clamping frame is made of insulating material and is a rectangular frame. The height of the clamping frame fills the gap between the edge of the protective electrode and the high voltage electrode. The clamping frame is used to clamp the protective electrode. The height of the clamping frame can be set according to the radiation measurement in the scene. The protective electrode, the high voltage electrode, and the collecting electrode are all made of air-equivalent material. The inner wall of the protective electrode and the bonding surface are provided with a conductive layer, which is connected to the shielding conductive layer by pressing.

2. The flat-plate ionization chamber for leaky radiation measurement according to claim 1, characterized in that: The high-voltage electrode is connected to the main frame by bolts. The hollow cavity of the main frame is also provided with two through holes on one side. A connector is provided on the side wall of one of the through holes, and the connector is electrically connected to the cable.

3. The flat plate ionization chamber for leaky radiation measurement according to claim 2, characterized in that: A vertical conductive groove is provided inside the hollow cavity of the main frame. The two high-voltage electrodes are electrically connected through the conductive layer inside the conductive groove. A wire groove is provided between the through hole and the hollow cavity. A pressure plate is connected to the wire groove by bolts.

4. The flat plate ionization chamber for leaky radiation measurement according to claim 1, characterized in that: The thickness of the high-voltage electrode that makes up the ionization cavity is 0.5mm-2mm, and all surfaces of the high-voltage electrode are provided with a conductive layer.

5. The flat-plate ionization chamber for leaky radiation measurement according to claim 1, characterized in that: The thickness of the collecting electrode is 0.5mm-2mm, and all surfaces of the air equivalent material are provided with a conductive layer. Aluminum foil is attached to the conductive layer, and the conductive core of the cable is bonded to the conductive layer with conductive graphite adhesive.

6. The flat-plate ionization chamber for leaky radiation measurement according to claim 1, characterized in that: The outer surface of the box structure formed by the high voltage electrode and the main frame is provided with a conductive layer. The high voltage electrode and the main frame are made of air-equivalent material or metal. The conductive layer provided on the upper and lower surfaces of the main frame can be connected to the outer conductive layer of the cable.

7. The flat plate ionization chamber for leaky radiation measurement according to any one of claims 1-6, characterized in that: The air equivalent material is plexiglass, the conductive layer is sprayed graphite, and a protective layer is provided outside the conductive layer, which is sprayed paint.

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