CN109011212A - Wide for medical accelerator can atmospheric air ionisation chamber - Google Patents

Abstract

The invention discloses a wide-energy normal-pressure air ionization chamber used for a medical accelerator, which relates to ionizing radiation detection technology, comprising: an outer shell made of metal material; an inner liner placed in the outer shell and forming air The layer is made of metal material; the collector is placed in the inner tank and the bottom is pierced through the inner tank; the insulating gasket is wrapped on the outside of the collector and placed between the inner tank and the collector. The base is built with an electronic system for signal transmission and electrically connected with the collector. The invention provides a wide-energy normal-pressure air ionization chamber for a medical accelerator with simplified structure and convenient installation, use and maintenance.

Description

Wide-energy Atmospheric Air Ionization Chamber for Medical Accelerator

technical field

The invention relates to ionizing radiation detection technology, in particular to a wide-energy normal-pressure air ionization chamber used for medical accelerators.

Background technique

Proton therapy is currently one of the most effective cancer treatment methods in the world, and my country has gradually begun to develop it. Our company is independently developing a superconducting cyclotron with an energy of 230MeV for proton therapy. During the beam supply and transportation process of the accelerator, neutron and photon radiation will inevitably be generated. Therefore, the beam loss monitoring system is of great significance for protecting the safety of personnel and equipment, and providing verification data for theoretical design. It is indispensable for large-scale accelerator facilities. Important subsystems that are missing. In addition, with the maturity of proton therapy technology, its commercialization and industrialization process will gradually accelerate, so the requirements for its important subsystems will gradually increase, and the whole set of equipment is bound to develop in a more convenient, efficient and easy-to-use direction.

The same type of facilities currently in operation or about to be built in the world all have beam damage and dose monitoring systems. The European Synchrotron Radiation Facility (ESRF) uses long coaxial cable air ionization chambers, scintillators and PIN diodes as beam damage detectors; Russia's U-70 synchrotron proton accelerator has installed air on all 120 deflection magnets in its accelerator hall. The ionization chamber acts as a beam loss detector to monitor the additional beam loss caused by the beam boost. The Spallation Neutron Source (SNS) in the United States is an example. Nearly 400 beam loss detectors are installed in its laboratory. Among them, the high-voltage ionization chamber is the main detection device, and it is installed in most of the beam loss positions of the SNS. such detectors.

Beam loss detectors basically adopt the scheme of air ionization chamber, PIN diode and scintillator. Considering the condition of high-power beam supply, the life of PIN diode and scintillator is greatly shortened due to radiation damage. Relatively The ionization chamber is the most reliable detector. From the analysis of the working medium type and structure, the high-pressure nitrogen ionization chamber of SNS has good electrical performance, but the manufacturing and maintenance process is troublesome, and the ionization chamber cannot continue to work in case of leakage; Due to its relatively large volume, the chamber has certain requirements for installation space, and proton therapy equipment is generally built in hospitals with limited space, so it is not suitable for proton therapy systems; the beam damage detection of U-70 uses a combination of multiple small ionization chambers The mode puts forward very high requirements on design and manufacture, which greatly increases the cost.

To sum up, the traditional ionization chamber is complex in design and requires high requirements in the manufacturing and installation process, which increases the production cost.

Contents of the invention

The purpose of the present invention is to provide a wide-capacity normal-pressure air ionization chamber for a medical accelerator, which has a simplified structure and is convenient for installation, use and maintenance.

The above-mentioned technical purpose of the present invention is achieved through the following technical solutions: a kind of wide-energy normal-pressure air ionization chamber for medical accelerators is characterized in that: comprising:

The shell is made of metal material;

The liner is placed in the shell and forms an air layer with the inner wall of the shell, and the liner has conductivity;

The collector is placed in the inner tank and the bottom is pierced through the inner tank;

The insulating gasket is wrapped on the outside of the collector and placed between the inner tank and the collector.

By adopting the above technical solution, the housing made of metal material is easier to process, install and maintain than the housing made of plexiglass, and is also more durable, which can prolong the service life to a certain extent; Set on the insulating gasket, use the insulating gasket to install the collector in the inner tank, and place the outer shell outside the inner tank, the structure is simple, and the production cost can be reduced. The shell has a good protective effect on the internal structure. During installation, an air layer is formed between the outer casing and the inner tank, and the air layer plays an insulating role and can prevent the outer casing from being electrified. When the γ-ray in the radiation environment enters the ionization chamber, it interacts with the air inside the liner to generate secondary electrons, ionizes the air, and generates positive and negative ion pairs. The inner wall of the gallbladder drifts, so that the generated current can be measured, and the measurement of the ionizing radiation dose rate can be completed.

The present invention is further configured as follows: the bottom of the liner is detachably connected with a base, and the insulating gasket is placed in the base.

By adopting the above technical scheme, the inner tank can be stably installed on the base with the insulating gasket, which can improve the stability of the entire ionization chamber during use and improve the accuracy of detection. The insulation effect between them improves the accuracy of measurement.

The present invention is further provided that: the base is built with an electronic system for signal transmission and electrically connected with the collector.

By adopting the above technical solution, the electronic system can output and measure the signal of the current generated after ionization, and the built-in electronic system can improve its installation stability and improve the accuracy of detection data.

The present invention is further provided that: the outer shell is sleeved on the outside of the base and is threadedly connected with the base.

By adopting the above technical solution, the shell protects both the base and the electronic system inside the base, so that the electronic system is located inside the shell, so that the shell can shield certain electromagnetic interference, thereby making the detected data more accurate.

The present invention is further configured as follows: the base includes a metal seat electrically connected to the inner container, the collector is set through the metal seat, the insulating gasket is placed between the metal seat and the collector, and the metal seat is used for It is used to connect the connection hole between the inner tank and the external electric field.

By adopting the above technical scheme, after the inner tank and the base are connected, the inner tank and the metal seat are directly connected electrically, and the external electric field is electrically connected to the inner tank through the connection hole, and at the same time, the insulating gasket is used to maintain the collector electrode and the metal base. The insulation between the seats is disconnected, thereby further improving the detection accuracy, and it is also convenient to complete the installation of the entire device.

The invention further provides that the electronics system includes an amplifier for amplifying the signal.

By adopting the above technical solution, the output current signal can be amplified by the amplifier, thereby realizing more accurate current measurement.

The present invention is further set as: the thickness of the air layer between the outer wall of the liner and the inner wall of the shell is 10mm-11mm.

By adopting the above technical solution, the thickness of the air layer in this range can effectively maintain the insulation between the inner tank and the outer shell, and at the same time keep the size of the outer shell within a reasonable range, thereby controlling the size and reducing the production cost.

The present invention is further provided that: the casing is made of stainless steel.

By adopting the above technical solution, the working environment conditions applicable to the shell can be broadened, the service life can be extended, and the durability of the shell can be improved.

The present invention is further provided that: the inner container is made of stainless steel or duralumin.

By adopting the above-mentioned technical solution, the service life can be extended to a certain extent, the production and manufacture can be facilitated, the durability can be improved, and a good ionization effect can be achieved in the ionization process.

The present invention is further provided that: the insulating gasket is a polytetrafluoroethylene gasket, and the collector is pierced through the polytetrafluoroethylene gasket.

By adopting the above technical scheme, a good insulation effect is achieved between the lower end of the collector and the inner tank, and the stability of the installation of the collector is improved, the stability between the collector and the inner tank is maintained, and the detection accuracy is improved.

In summary, the present invention has the following beneficial effects:

One: Combining the shell made of metal and the liner made of conductive material, and the base connected to the liner of the shell, the collecting pole pierced through the base, the overall structure is simple, the manufacture and installation are convenient, the working state is stable, the service life is long, and the Cost of production;

Second: the use of the shell can have a good protective effect on both the inner tank and the electronic system, and can shield the interfering signal, thereby improving the accuracy of detection.

Description of drawings

Fig. 1 is the sectional view of present embodiment;

Fig. 2 is a schematic diagram of the exploded structure of this embodiment.

Reference signs: 1, shell; 2, liner; 3, collector; 4, insulating gasket; 5, base; 51, metal seat; 52, insulating seat; 53, base; 6, air layer; 7, Mounting rod; 8. Connecting rod; 9. Electronics system; 10. Connecting hole; 11. Center hole; 12. Through hole.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

A wide-energy normal-pressure air ionization chamber for a medical accelerator, as shown in Figure 1 and Figure 2, includes a hollow inner tank 2 with a bottom opening and a cathode, and the bottom opening of the inner tank 2 is embedded with An insulating gasket 4, the center of the insulating gasket 4 is pierced with a collector 3 that is vertically arranged and used as an anode, the upper end of the collector 3 extends into the inner tank 2, and the lower end is pierced through the insulating gasket 4. An electronic system 9 is connected, and an air layer 6 is formed between the collector 3 and the inner wall of the liner 2. When gamma rays are incident on the inside of the liner 2, the air is ionized to generate positive and negative ion pairs, and at the same time, under the action of an external electric field, , the positive and negative ions drift to the anode and the cathode respectively, thus relying on the electronic system 9 to output the current signal to the outside. Since the ionization current is proportional to the intensity of the radiation, the intensity of the ionizing radiation can be obtained by measuring the current, so as to complete the ionizing radiation dose rate measurement.

With reference to shown in Figure 1, liner 2 is cylinder, but shape is not limited to cylinder, also can be cuboid or polygonal prism, liner 2 is made of duralumin with a thickness of 3mm, but material is not limited to duralumin, also Can be made of stainless steel material. The interior of the liner 2 is connected with the outside, so that there is air in the interior of the liner 2 . In order to improve the stability of the inner container 2 and facilitate the application of an electric field to the inner container 2, a base 5 is connected to the bottom of the inner container 2, and the base 5 includes a metal seat 51 screwed to the opening at the bottom of the inner container 2, so that Conductive connection is realized between the metal seat 51 and the inner container 2, as shown in Fig. 2, at the same time, a connection hole 10 for connecting an external electric field is provided on the metal seat 51; the cross section of the metal seat 51 is convex, and the center of the metal seat 51 A through hole 12 is opened, and the insulating gasket 4 is embedded in the through hole 12. At the same time, the collector 3 is penetrated and installed in the center of the insulating gasket 4, so that the insulating gasket 4 is opposite to the collector 3 and the metal seat. 51 play a role of separation and insulation. In order to strengthen the stable support effect of the inner container 2, the base 5 also includes an annular insulating seat 52 sleeved on the outer ring of the metal seat 51 and placed between the bottom of the inner container 2 and the metal seat 51, the outer ring of the insulating seat 52 The diameter is greater than the diameter of the liner 2. Both the insulating spacer 4 and the insulating seat 52 are made of polytetrafluoroethylene, and the insulating spacer 4 and the insulating seat 52 have a certain deformation ability, so they can play a good role of stable support after installation.

The collector 3 is vertically installed through the center of the insulating spacer 4 . The collector 3 is in the shape of a cylinder, but not limited to this shape, and is made of pure copper. The upper end of the collecting pole 3 extends close to the upper end surface of the inner container 2, and the distance between the upper end surface of the collecting electrode 3 and the upper end surface of the inner container 2 is about 10mm.

Since the current signal on the collector 3 is weak during the detection process, the signal amplifier in the electronics system 9 can enhance the output current signal, so as to detect the current value conveniently and accurately.

1 and 2, in order to stably install the electronic system 9, the base 5 also includes a plurality of vertical mounting rods 7 that are evenly arranged along the edge of the insulating seat 52 and are fixedly connected to the edge of the insulating seat 52. A disc-shaped base 53 is fixedly connected to the bottom of the rod 7, and two connecting rods 8 are fixedly connected to the bottom surface of the metal seat 51 in the space surrounded by the mounting rod 7, and the connecting rods 8 are used for installing the electronic system 9. At the same time, in order to output the signal of the electronic system 9 and apply an electric field to the liner 2 , a central hole 11 is opened in the center of the base 53 for the passage of power supply lines and output signal lines.

In order to improve the accuracy of detection in the whole process, a shell 1 is set outside the inner tank 2 to provide mechanical protection and fixed support, and at the same time, the shell 1 is used to provide good shielding for the electronic system 9 in the base 5 As a result, the shell 1 is made of metal material. In this embodiment, 304 stainless steel is preferably used, and it is a cylinder with a hollow interior and an open bottom. However, its shape is not limited to the cylinder defined in this embodiment, and it can also be a cuboid, multiple Prismatic, the thickness of the shell 1 is 2mm. The inner wall of the shell 1 is in contact with the outer wall of the insulating seat 52 , and the insulating seat 52 is used to support and stabilize the shell 1 . The bottom of the housing 1 extends to the base 53 at the bottom, and the housing 1 is screwed to the outer wall of the base 53 , so that the electronic system 9 is placed inside the housing 1 to achieve a better detection effect.

Through calculation and testing, the energy response range of the device is between 150KeV-10MeV, fully meeting the radiation dose monitoring application of medical accelerators.

The working principle of this embodiment is:

The insulating gasket 4 is embedded in the metal seat 51, and the collector 3 is inserted in the center of the insulating gasket 4, and the upper end of the metal seat 51 is screwed to the bottom of the inner container 2, and the insulating seat 52 is sleeved on the Outside the metal seat 51, the electronic system 9 is electrically connected to the bottom end of the collector 3, and at the same time, the input line electrically connected to the electronic system 9 is stretched out from the central hole 11 at the bottom of the base 53, synchronously, by using an electric wire Pass through the connection hole 10 to electrically connect to the inner tank 2, and pass the wire through the central hole 11. Finally, the outer shell 1 is set outside the inner tank 2 and screwed to the upper end of the base 53. Before starting the test, the wire A voltage of -500V is applied to it.

When the gamma rays in the radiation environment are incident on the ionization chamber, secondary electrons are generated under the interaction with the air in the liner 2, ionizing the air, and generating positive and negative ion pairs. At the same time, under the action of an external electric field, the positive and negative ion pairs are respectively The collector 3 and the inner wall of the liner 2 drift, and after the air is ionized to generate ion pairs, due to electrostatic induction, induced charges will be generated on the two electrodes, and a current will be generated at the same time. The magnitude of the current is proportional to the dose of incident particles. The electronic system 9 passes Measuring the current generated after ionization and amplifying and outputting the signal completes the measurement of the ionizing radiation dose rate.

This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contribution as required after reading this specification, but as long as they are within the rights of the present invention All claims are protected by patent law.

Claims (10)

1. A wide-energy normal-pressure air ionization chamber for medical accelerators is characterized in that: comprising: The shell (1) is made of metal material; The liner (2) is placed in the shell (1) and forms an air layer (6) with the inner wall of the shell (1), and the liner (2) has conductivity; The collector (3) is placed in the inner tank (2) and the bottom is pierced through the inner tank (2); The insulating gasket (4) is coated on the outside of the collector (3) and placed between the inner liner (2) and the collector (3). 2. A wide-energy normal-pressure air ionization chamber for medical accelerators according to claim 1, characterized in that: the bottom of the liner (2) is detachably connected with a base (5), and the insulating gasket (4) Place it in the base (5). 3. A wide-energy normal-pressure air ionization chamber for medical accelerators according to claim 2, characterized in that: the base (5) is built with electrons for signal transmission and electrically connected to the collector (3) Learning System (9). 4. A wide-energy normal-pressure air ionization chamber for medical accelerators according to claim 3, characterized in that: the shell (1) is sheathed outside the base (5) and is threaded with the base (5) connect. 5. A wide-energy normal-pressure air ionization chamber for medical accelerators according to claim 2, characterized in that: the base (5) includes a metal seat (51) electrically connected to the liner (2), The collector (3) is passed through the metal seat (51), the insulating gasket (5) is placed between the metal seat (51) and the collector (3), and the metal seat (51) is opened for The connection hole (10) for connecting the liner (2) and the external electric field. 6. A wide-energy atmospheric pressure air ionization chamber for a medical accelerator according to claim 3, characterized in that: the electronic system (9) includes an amplifier for amplifying signals. 7. A wide-energy normal-pressure air ionization chamber for medical accelerators according to any one of claims 1-6, characterized in that: the outer wall of the inner tank (2) and the inner wall of the outer shell (1) The thickness of the air layer (6) is 10mm-11mm. 8. A wide energy atmospheric pressure air ionization chamber for a medical accelerator according to any one of claims 1-6, characterized in that: the casing (1) is made of stainless steel. 9. A wide-energy atmospheric pressure air ionization chamber for a medical accelerator according to any one of claims 1-6, characterized in that: the inner tank (2) is made of stainless steel or duralumin. 10. A wide-energy atmospheric pressure air ionization chamber for medical accelerators according to any one of claims 1-6, characterized in that: the insulating gasket (4) is a polytetrafluoroethylene gasket, so The collector (3) is installed on the polytetrafluoroethylene gasket.