Low pressure ionization chamber and accelerator

Abstract

The present invention discloses a low-pressure ionization chamber and an accelerator, comprising a sealed chamber, wherein a low-pressure environment lower than the standard atmospheric pressure is formed in the sealed chamber, and an electrode plate assembly is arranged in the sealed chamber to collect electron-ion pairs in the sealed chamber under the low-pressure environment; by setting a negative pressure sealed chamber, under low-pressure conditions, the air density is reduced, resulting in a reduction in the number of gas molecules per unit volume, thereby reducing the total number of charges generated by the radiation ionization gas medium, and then reducing the charge density and the probability of ion recombination, thereby affecting the saturation characteristics of the ionization chamber.

Description

Technical Field

[0001] The invention relates to the technical field of radiotherapy dose monitoring, and in particular to a low-pressure ionization chamber and an accelerator. Background Art

[0002] An ionization chamber is a detector that uses the ionization effect of ionizing radiation to measure ionizing radiation, also known as an ion chamber. An ionization chamber consists of electrodes at different potentials and a medium between them. Ionizing radiation produces ionized ion pairs in the medium. Under the action of the electric field, positive and negative ions drift toward the negative electrode and positive electrode respectively, forming an ionization current. Since the ionization current is proportional to the intensity of the radiation, the intensity of the ionizing radiation can be obtained by measuring this current.

[0003] Ultra-high dose rate and ultra-short pulse are the core radiation characteristics of FLASH (flash) radiotherapy, but they are obstacles for existing conventional dose detection methods (especially detectors). Under FLASH conditions, a large amount of dose is deposited instantaneously, generating ultra-high density of positive and negative charge carriers. These carriers are very easy to meet and recombine during the migration and collection process, resulting in an unpredictable and significant decrease in charge collection efficiency. At the same time, a large amount of charge will cause serious electric field distortion and aggravate the polarization effect. This ion migration and recombination process at the physical level is extremely complex and extremely sensitive to the internal structure and electric field of the ionization chamber. It is difficult to accurately predict and calculate, that is, we cannot eliminate this effect through theoretical correction. Therefore, the atmospheric pressure penetrating air ionization chamber is not suitable for dose monitoring of ultra-high dose rate radiotherapy equipment.

[0004] The inventors have found that the ion recombination effect can be effectively avoided in an environment below the standard atmospheric pressure. Therefore, based on the above considerations, the dose measurement of ultra-high dose rate radiation is performed under near-vacuum conditions.

[0005] The low-pressure environment places higher demands on the design, manufacture, assembly and formation of the low-pressure state of the ionization chamber sealing structure. At the same time, in order to ensure the treatment space, the installation space left for the treatment head in the ionization chamber is very small, which further increases the difficulty of the ionization chamber design. Summary of the invention

[0006] In view of the shortcomings of the prior art, a low-pressure ionization chamber and an accelerator are proposed, which solve the problem that the normal-pressure penetrating air ionization chamber in the above-mentioned background technology is not suitable for dose monitoring of ultra-high dose rate radiotherapy equipment.

[0007] To achieve the above objectives, the present invention proposes the following technologies to achieve the above objectives:

[0008] The low-pressure ionization chamber comprises a sealed chamber, in which a low-pressure environment lower than the standard atmospheric pressure is formed. An electrode plate assembly is arranged in the sealed chamber to collect electron-ion pairs in the sealed chamber under the low-pressure environment.

[0009] Furthermore, the sealed chamber is located between the cover plate and the main cavity, a first sealing member is embedded in the main cavity, and the cover plate presses the first sealing member to achieve sealing of the sealed chamber.

[0010] Furthermore, a first sink groove is provided on the main cavity to form a closed chamber to accommodate the electrode plate assembly, and one end of the first sink groove is connected to the gas channel to facilitate gas discharge to form a negative pressure environment.

[0011] Furthermore, the other end of the first trough is connected to a transition pipe arranged opposite to the gas channel, and the end of the transition pipe away from the closed chamber is sealed and connected to a plug installation through a second seal to facilitate the installation of the plug to power the electrode plate assembly in the closed chamber.

[0012] Furthermore, a second sink is provided at one end of the first sink to increase the volume of the closed chamber.

[0013] Furthermore, two sealed chambers are symmetrically arranged about the main cavity, and the sealed chambers on the upper and lower sides of the main cavity face opposite directions.

[0014] Furthermore, grooves are respectively provided on the upper and lower sides of the main cavity to form a transmission window, and a first gas flow port is provided at the edge of the groove, and the first gas flow port connects the groove and the closed chamber.

[0015] Furthermore, the electrode plate assembly includes a collecting electrode and a high-voltage electrode, the collecting chamber is located between the collecting electrode and the high-voltage electrode, and an insulating member for separating the collecting electrode and the high-voltage electrode is disposed on the periphery of the collecting chamber. Several insulating members are disposed along the circumferential direction, and a second gas flow port is formed between two adjacent insulating members to facilitate gas flow.

[0016] Furthermore, the substrate of the electrode plate assembly is a ceramic material.

[0017] Furthermore, the portion of the outer surface of the transition tube located outside the main cavity is welded at a position in contact with the main cavity, and the end of the transition tube located inside the main cavity is welded at a position in contact with the main cavity, and the gas channel passes through the side wall of the main cavity and is connected to the main cavity by welding.

[0018] Furthermore, the two plugs are located on the same side of the main cavity and are arranged horizontally in parallel, and the two gas channels are located on a side of the main cavity away from the plugs and are arranged horizontally in parallel.

[0019] On the other hand, an accelerator is also provided, comprising any of the low-pressure ionization chambers described above.

[0020] Compared with the prior art, the comprehensive effects brought by the present invention include:

[0021] By setting up a closed chamber with negative pressure, the air density is reduced under low pressure conditions, resulting in a decrease in the number of gas molecules per unit volume and a decrease in the total number of ionized electron-ion pairs, thereby weakening the recombination effect of ion pairs and improving the accuracy and reliability of the measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the overall explosion structure of an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the overall external structure of an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram of the cross-sectional structure of a transition pipe according to an embodiment of the present invention;

[0025] Figure 4 for Figure 3 Schematic diagram of the local structure at B in the middle;

[0026] Figure 5 It is a schematic diagram of a top view structure of an embodiment of the present invention;

[0027] Figure 6 This is a schematic diagram of the first sink structure according to an embodiment of the present invention;

[0028] Figure 7 This is a schematic diagram of the structure of the first gas flow port according to an embodiment of the present invention;

[0029] Figure 8 Schematic diagram of the protrusion structure of an embodiment of the present invention.

[0030] Legend: 1. Upper cover; 2. Main cavity; 3. First sealing member; 4. Gas channel; 5. Transition tube; 6. Second sealing member; 7. Plug; 8. Shielding member; 9. Transmission window; 10. Collecting electrode; 11. High-voltage electrode; 12. Insulating member; 13. Lower cover; 14. Plug mounting member; 15. Bracket; 16. First trough; 17. Second trough; 18. Wiring groove; 19. Groove; 20. First gas flow port; 21. Second gas flow port; 22. Protrusion. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention.

[0032] In this document, the terms "upper", "lower", "left", "right", "top" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention. Figures 1 to 8 As shown, the low-pressure ionization chamber includes a closed chamber, in which a low-pressure environment lower than the standard atmospheric pressure is formed. An electrode plate assembly is arranged in the closed chamber to collect electron-ion pairs generated after the medium in the closed chamber is ionized by X-rays under the low-pressure environment.

[0033] The principle of measuring radiation dose by ionization chamber is based on the ionization effect produced by radiation in the medium (usually air). By setting up a closed chamber with negative pressure, the air density is reduced under low pressure conditions, resulting in a decrease in the number of gas molecules per unit volume, thereby weakening the recombination effect of ion pairs and affecting the response of the ionization chamber.

[0034] In other embodiments, the ionization chamber can also be used for dose rate monitoring of radiotherapy equipment such as electrons, protons, and heavy ions.

[0035] In the low-pressure ionization chamber of this embodiment, the sealed chamber includes a sealed chamber located between the cover plate and the main chamber 2, a first sealing member 3 is embedded in the main chamber 2, and the cover plate presses the first sealing member 3 to achieve sealing of the sealed chamber.

[0036] Specifically, the cover plate includes an upper cover plate 1. The closed chamber is actually a chamber formed by the upper cover plate 1 and the main chamber 2. The closed chamber is in a low pressure state. In a low pressure environment, the total number of ions and ion density will decrease, thereby reducing the probability of ion recombination. Preferably, the pressure range is 0.01atm-0.5atm.

[0037] It should be noted that the upper cover plate 1 and the main cavity 2 are sealed by a first seal 3 , which can be made of indium wire. The first seal 3 is arranged along the edge of the closed chamber, and a sealing groove is opened on the main cavity 2 to facilitate the embedding of the first seal 3 .

[0038] Preferably, the upper cover plate 1 and the main cavity 2 are connected by connecting bolts, and a plurality of connecting bolts are arranged along the outer edge of the sealing groove. Through the above arrangement, when the upper cover plate 1 and the main cavity 2 are assembled, the first sealing member 3 will be subjected to a certain degree of extrusion, so that the first sealing member 3 and the sealing grooves on the upper cover plate 1 and the main cavity 2 fit more closely, thereby ensuring the airtightness of the closed chamber. The first sealing member 3 is arranged along the contour of the first sink groove 16 in the main cavity, and the first sealing member 3 is arranged around the contour of the first sink groove 16. In this embodiment, the first sealing member 3 is arranged along the peripheral side of the contour of the first sink groove 16 to form a closed figure, which can effectively ensure the airtightness between the main cavity 2 and the upper cover plate 1.

[0039] In the low-pressure ionization chamber of this embodiment, a first sink 16 is provided on the main cavity 2 to form a closed chamber to accommodate the electrode plate assembly, and one end of the first sink 16 is connected to the gas channel 4 to facilitate gas discharge to form a negative pressure environment.

[0040] Specifically, the gas channel 4 can be used to connect a negative pressure pump such as an ion pump to extract the gas in the sealed chamber so that the sealed chamber is in a low pressure state.

[0041] Specifically, the gas channel 4 passes through the side wall of the main cavity 2 and is connected to the main cavity 2 by brazing. The gas channel 4 is made of an oxygen-free copper tube. The oxygen-free copper tube has a low oxygen content, which can ensure the quality of the weld and the airtightness during brazing.

[0042] In the low-pressure ionization chamber of this embodiment, oppositely arranged transmission windows 9 are provided on the upper cover plate 1 and the main cavity 2, and the electrode plate assembly is located between the two transmission windows 9 to facilitate X-rays to pass through the transmission windows 9 and enter the collection cavity in the electrode plate assembly.

[0043] Specifically, in order to maintain good airtightness, the upper cover plate 1 and the transmission window 9 are integrally formed, and the transmission window 9 is formed by milling, grinding and other processes. The transmission window 9 on the main cavity 2 is also formed integrally with the transmission window 9 by milling, grinding and other processes. When assembling the upper cover plate 1 and the main cavity 2, bolts are driven into the thicker part of the outer side of the transmission window 9, and the assembly holes of the bolts are at a certain distance from the transmission window 9, thereby effectively avoiding the transmission window 9 from being deformed by force during assembly.

[0044] Preferably, the edge of the transmission window 9 is smoothly connected to the main cavity 2. From the cross-sectional view, there is a smooth arc transition between the left part / right part of the main cavity 2 and the transmission window 9. The above arrangement avoids stress concentration, thereby improving the deformation resistance of the transmission window 9.

[0045] Preferably, a second sinking groove 17 is further provided on the bottom surface of the first sinking groove 16 at one end of the closed chamber where the gas channel 4 is provided, and a height difference between the first sinking groove 16 and the second sinking groove 17 can expand the volume of the ionization chamber.

[0046] The gas channel 4 is arranged in the middle and lower part of the second trough 17. Through the above arrangement, the connecting port of the gas channel 4 in the second trough 17 forms a height difference with the electrode plate assembly on the first trough 16. When the negative pressure pump is evacuated, the gas will not directly disturb the electrode plate, which can prevent the electrode plate from deforming or moving. Similarly, when the gas flows, it will not disturb the thin transmission window 9, thereby preventing the transmission window 9 from deforming and playing a protective role. During use, if there is a problem with the airtightness of the ionization chamber, the ambient gas enters the ionization chamber. Because there is a large cavity structure, when the amount of gas entering is not very large, the air pressure change in the ionization chamber is much smaller than when there is no cavity structure, which can ensure that the test results will not fluctuate greatly. That is, compared with a small ionization chamber, the ionization chamber in this technology is larger in volume, so the air pressure fluctuation is smaller.

[0047] For a closed chamber with the same gas pressure, a large-volume gas chamber has a larger total number of gas molecules than a small-volume gas chamber. In fact, during the use of the ionization chamber, the gas molecules will be consumed. A large-volume gas chamber can provide more gas molecules for X-ray dose monitoring, and can maintain the stability of the gas composition in the chamber for a long time, thereby ensuring the accuracy of dose monitoring in the ionization chamber over a long period of time.

[0048] Preferably, the thickness of the transmission window 9 is 0.05 mm-0.1 mm. A thinner thickness can reduce the dose loss of X-rays.

[0049] In the low-pressure ionization chamber of this embodiment, the other end of the first sedimentation tank 16 is connected to a transition tube 5 arranged opposite to the gas channel 4, and the end of the transition tube 5 away from the closed chamber is sealed and connected to a plug 7 through a second seal 6 to facilitate power supply to the electrode plate assembly in the closed chamber.

[0050] Specifically, a transition tube 5 is provided for installing the plug 7 and facilitating the routing of wires connecting the plug 7 and the electrode plate assembly. The plug adopts an aviation plug to ensure high air tightness.

[0051] Specifically, a plug mounting member 14 is provided between the transition tube 5 and the plug 7. The outer end of the plug mounting member 14 matches the plug 7, and the other end is plugged into the transition tube 5. A circumferential groove is provided on the end surface of the transition tube 5 for installing the second sealing member 6. The second sealing member 6 is also made of indium wire. Using indium wire instead of a rubber gasket can resist radiation and aging, thereby increasing the service life.

[0052] Preferably, the portion of the transition pipe 5 inserted in the main cavity 2 is connected to the main cavity 2 by welding to ensure sealing, the end of the transition pipe 5 located in the main cavity 2 is welded to the contact position with the main cavity 2, the portion of the transition pipe 5 located outside the main cavity 2 is welded to the contact position with the main cavity 2 to strengthen the connection strength between the transition pipe 5 and the main cavity 2, the portion of the outer surface of the transition pipe 5 located outside the main cavity 2 is welded to the contact position with the main cavity 2, and the plug mounting part 14 fits against the end of the transition pipe 5 to squeeze the second sealing part 6 to enhance the sealing effect.

[0053] Preferably, a wiring groove 18 is provided at one end of the transition tube 5 in the closed chamber on the basis of the first sink 16 to facilitate the wiring of the wires of the plug 7. Based on the above structure, the closed chamber is composed of the plug mounting part 14 to the wiring groove 18, the space where the electrode plate assembly is located and the area between the second sink 17.

[0054] In the low-pressure ionization chamber of this embodiment, a shielding member 8 for preventing X-ray leakage is provided at one end of the main cavity 2 away from the gas channel 4, and the transition tube 5 passes through the shielding member 8 and the side wall of the main cavity 2 to connect to the closed chamber.

[0055] Specifically, a shielding member 8 is provided to prevent X-rays from interfering with other components in the radiotherapy device. In the entire radiotherapy device, a collimator is located above the ionization chamber, and the outer diameter of the transmission window 9 is not less than the output aperture of the collimator: the ionization chamber itself can be regarded as being located in a ring-shaped tungsten disk, and the shape and size of the transmission window 9 of the ionization chamber are adapted to the output aperture of the collimator. Preferably, the output aperture can be equal to or less than the diameter of the transmission window 9. After the ionization chamber is installed, the shielding member 8 is located at one end of the main cavity 2, and the position of the shielding member 8 is equivalent to the opening on the side surface of the tungsten disk for inserting the ionization chamber, which can prevent X-rays from leaking from the side surface of the tungsten disk.

[0056] Preferably, the shielding member 8 may be made of tungsten alloy material, and brackets 15 are respectively provided at both ends of the shielding member 8 to facilitate fixed installation of the ionization chamber.

[0057] In the low-pressure ionization chamber of this embodiment, the electrode plate assembly includes a collecting electrode 10 and a high-voltage electrode 11 fixedly connected to the main cavity 2. The collecting electrode 10 is located on the side of the high-voltage electrode 11 away from the main cavity 2, and the collecting cavity is located between the collecting electrode 10 and the high-voltage electrode 11.

[0058] Specifically, the electrode plate assembly uses an electrode plate of a composite structure, and the base of the electrode plate is a ceramic material. The ceramic is selected to ensure that the electrode plate has a certain rigidity and is not easily deformed, and to be resistant to radiation and prevent aging.

[0059] The upper surface of the main cavity 2 is connected to the electrode plate by bolts. The diameter of the electrode plate is larger than the diameter of the transmission window 9 on the main cavity 2, so that there is a sufficient distance between the bolt installation hole and the transmission window 9 to avoid deformation of the transmission window 9 caused by the installation bolts.

[0060] The high voltage electrode 11 in the electrode plate is connected to the plug 7 through a wire. After being powered on, it is ionized by X-ray irradiation. The electron-ion pairs of the gas in the collection chamber after X-ray ionization are collected by the collecting electrode 10 to facilitate the detection and measurement of the X-ray dose rate.

[0061] In the prior art, the electrode plates are completely attached to the upper and lower surfaces of the main cavity, and the interval between the electrode plates and the main cavity is very small, which is not conducive to gas circulation. In the present invention, a negative pressure pump is required to evacuate the interior of the ionization chamber to achieve an internal environment below the standard atmospheric pressure. The design in which the electrode plates are completely attached to the main cavity will hinder gas circulation, and if the existing design is adopted, due to the existence of pressure difference, the electrode plates will deform or move during the pumping process. Therefore, the main cavity design in the existing ionization chamber is also not suitable for the low-pressure ionization chamber in the present invention.

[0062] In the low-pressure ionization chamber of this embodiment, grooves 19 are respectively provided on the upper and lower sides of the main cavity 2 to form a transmission window 9, and a first gas flow port 20 is provided at the edge of the groove 19, which connects the groove 19 and the closed chamber.

[0063] Specifically, the transmission window 9 on the main cavity 2 is formed into a groove 19 during the milling process, and the bottom surfaces of the upper and lower grooves 19 are between the transmission window 9. Since the thickness of the transmission window 9 is relatively thin and the distance between the electrode plate and the main cavity 2 is relatively close, it is easy to cause the gas in the groove 19 to not circulate, so that when the negative pressure is pumped, it is easy to form a pressure difference between the groove 19 and the closed chamber, and then the transmission window 9 is deformed due to the pressure. Therefore, the first gas flow port 20 is provided to enhance the connection between the space in the groove 19 and the closed chamber, to ensure that the negative pressure is pumped smoothly, and to avoid deformation of the transmission window 9.

[0064] Preferably, Figure 7 and Figure 8 As shown, the first gas flow port 20 is a groove opened on the edge of the groove 19 on the main cavity 2, which connects the internal space of the groove 19 and the external closed chamber through the groove. In addition, the gas connection port can also be formed by supporting the electrode plate through the protrusion 22 on the main cavity 2 to form a gap between the electrode plate and the main cavity 2, ensuring that there is a gap when the electrode plate is assembled on the main cavity 2 to allow gas to flow.

[0065] In the prior art, the electrode plate includes a collecting plate, a high-voltage plate, and an insulating member disposed between the collecting plate and the high-voltage plate. The traditional insulating member is a closed circular ring, which can provide good support for the electrode plate. However, in the present invention, a negative pressure pump is required to evacuate the interior of the ionization chamber to achieve an internal environment below the standard atmospheric pressure. The existence of the closed circular ring will hinder the flow of gas, so the closed circular ring structure is not suitable for low-pressure ionization chambers. Furthermore, if the existing design is adopted, due to the existence of pressure difference and the obstruction of the air flow channel, the electrode plate will move or deform during the air extraction process, thereby affecting the spacing between the high-voltage electrode and the collecting electrode, affecting the total amount of medium between the high-voltage electrode and the collecting electrode, thereby affecting the generation efficiency of electron-ion pairs, and ultimately affecting the X-ray dose monitoring results.

[0066] In the low-pressure ionization chamber of this embodiment, an insulating member 12 for separating the collecting electrode 10 and the high-voltage electrode 11 is disposed on the periphery of the collecting chamber. A plurality of insulating members 12 are disposed along the circumferential direction, and a second gas flow port 21 is formed between two adjacent insulating members 12 to facilitate gas flow.

[0067] Specifically, the electrode plate includes three layers of plates, the upper plate is the collecting electrode 10, the middle plate is the insulating member 12, and the lower plate is the high-voltage electrode 11. In this embodiment, four insulating members 12 are arranged between the upper plate and the lower plate. The four insulating members 12 are arranged at intervals along the circumferential direction, so that the upper plate and the lower plate can be uniformly stressed. At the same time, the gas can flow in quickly from the second gas flow port 21 formed between the insulating members 12 to avoid deformation or movement of the electrode plate during the vacuum pumping process of the ionization chamber. The deformation of the electrode plate will affect the electric field strength, affect the distance between the high-voltage electrode 11 and the collecting electrode 10, and affect the total amount of medium between the high-voltage electrode plate and the collecting electrode plate, thereby affecting the generation efficiency of electron-ion pairs, and ultimately affecting the collection effect of electron-ion pairs.

[0068] Preferably, the insulating member 12 is made of ceramic sheets, which can play a good insulating role. Compared with insulating materials such as rubber, which will age when exposed to X-rays, ceramic sheets have better radiation resistance and anti-aging effects, thereby increasing the service life.

[0069] In the low-pressure ionization chamber of this embodiment, the cover plate also includes a lower cover plate 13, and also includes a closed chamber located between the lower cover plate 13 and the main cavity 2. The lower cover plate 13 and the upper cover plate 1 are arranged relative to the main cavity 2 and a transmission window 9 is arranged on the lower cover plate 13. The upper and lower sides of the main cavity 2 are respectively provided with a first sink 16 to form an upper closed chamber and a lower closed chamber to accommodate the electrode plate assembly.

[0070] Preferably, the entire ionization chamber adopts a centrally symmetrical design, and the upper and lower closed chambers are centrally symmetrical. The first groove 16 on the upper surface of the main cavity 2 is in a convex shape, and the first groove 16 on the lower surface is in a convex shape facing oppositely. The second groove 17 for connecting the gas channel 4 and the wiring groove 18 for wiring are respectively located at both ends of the convex.

[0071] The two plugs 7 are located on the same side of the main cavity 2 and are arranged horizontally in parallel. The two gas channels 4 are located on the side of the main cavity 2 away from the plugs 7 and are arranged horizontally in parallel. The wiring groove 18 and the second sink 17 in the upper closed chamber are staggered with the wiring groove 18 and the second sink 17 in the lower closed chamber, so as to make full use of the main cavity 2 and reduce the overall thickness of the main cavity 2. The upper and lower closed chambers can effectively improve the space utilization of the entire ionization chamber, increase the volume of the closed chamber, and make the volume of the treatment head smaller, thereby reserving more treatment space for patients in the radiotherapy room. In other embodiments, the shape of the first sink 16 includes but is not limited to circular, oval, square, and irregular shapes.

[0072] It should be noted that the screw holes for connecting the upper electrode plate and the main cavity 2 are staggered with the screw holes for connecting the lower electrode plate and the main cavity 2. The purpose of this arrangement is to ensure that the thickness of the main cavity 2 is relatively thin. If the upper and lower screw holes are located on the same vertical line, the upper and lower originally closed chambers will be connected. In order to avoid this situation, the upper and lower screw holes are staggered.

[0073] Preferably, the upper and lower cover plates are made of aluminum alloy and are connected to the main cavity 2 by countersunk screws respectively. The aluminum alloy material has good X-ray transmittance, thereby reducing dose loss. The main cavity 2 uses stainless steel, which is easy to weld with the transition pipe 5 and the gas channel 4. Correspondingly, the transition pipe 5 is also made of stainless steel.

[0074] On the other hand, the present application also proposes an accelerator, comprising the low-pressure ionization chamber described in any of the above embodiments. It can be expected that the accelerator in this embodiment includes the beneficial effects of the low-pressure ionization chamber described in any of the above embodiments, which will not be repeated here.

[0075] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "rotation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0076] Although the embodiments of the present invention have been shown and described in detail, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low pressure ionization chamber, characterized in that: The method comprises a sealed chamber, wherein a low pressure environment lower than the standard atmospheric pressure is formed in the sealed chamber, and an electrode plate assembly is arranged in the sealed chamber to collect electron-ion pairs in the sealed chamber under the low pressure environment; The sealed chamber is located between the cover plate and the main chamber, and two sealed chambers are arranged above and below; The main cavity is provided with a first sink groove to form a closed chamber to accommodate the electrode plate assembly, and one end of the first sink groove is connected to the gas channel to facilitate gas discharge to form a negative pressure environment; A second sink is provided at one end of the first sink to increase the volume of the closed chamber.

2. The low-pressure ionization chamber according to claim 1, characterized in that: A first sealing member is embedded in the main cavity, and the cover plate presses the first sealing member to achieve sealing of the closed cavity.

3. The low-pressure ionization chamber according to claim 1, characterized in that: The other end of the first trough is connected to a transition pipe arranged opposite to the gas channel, and the end of the transition pipe away from the closed chamber is sealed and connected to a plug installation through a second seal to facilitate the installation of the plug to power the electrode plate assembly in the closed chamber.

4. The low-pressure ionization chamber according to claim 1, characterized in that: The two sealed chambers are symmetrically arranged about the main cavity, and the sealed chambers on the upper and lower sides of the main cavity face opposite directions.

5. The low-pressure ionization chamber according to claim 4, characterized in that: Grooves are respectively provided on the upper and lower sides of the main cavity to form a transmission window, and a first gas flow port is provided at the edge of the groove, and the first gas flow port connects the groove and the closed chamber.

6. The low-pressure ionization chamber according to claim 1, characterized in that: The electrode plate assembly includes a collecting electrode and a high-voltage electrode, a collecting chamber is arranged between the collecting electrode and the high-voltage electrode, an insulating member for separating the collecting electrode and the high-voltage electrode is arranged at the periphery of the collecting chamber, a plurality of insulating members are arranged along the circumferential direction, and a second gas flow port is formed between two adjacent insulating members to facilitate gas flow.

7. The low-pressure ionization chamber according to claim 1, characterized in that: The substrate of the electrode plate assembly is a ceramic material.

8. The low-pressure ionization chamber according to claim 3, characterized in that: The portion of the outer surface of the transition tube located outside the main cavity is welded to the position in contact with the main cavity, and the end of the transition tube located inside the main cavity is welded to the position in contact with the main cavity. The gas channel passes through the side wall of the main cavity and is connected to the main cavity by welding.

9. The low-pressure ionization chamber according to claim 3, characterized in that: The two plugs are located on the same side of the main cavity and are arranged horizontally in parallel, and the two gas channels are located on a side of the main cavity away from the plugs and are arranged horizontally in parallel.

10. An accelerator, characterized in that: A low-pressure ionization chamber comprising any one of claims 1-9.

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