Micro Penning Ion Source

Abstract

The present invention discloses a micro Penning ion source, which belongs to the field of superconducting cyclotron accelerator. The key points of the technical solution are that it comprises an anode tube, cathodes arranged at both ends of the anode tube, and a shell covering the cathode and the anode tube; a plurality of cluster-shaped protrusions are arranged on the end faces of the cathodes arranged opposite to each other; a hydrogen channel for connecting the anode tube with the outside is opened on the shell at at least one end of the cathode, and a lead-out slit is opened at the middle position of the anode tube. The present invention achieves the effect of increasing the amount of primary electron emission.

Description

Technical Field

[0001] The present invention relates to the field of superconducting cyclotron accelerators, and more particularly to a micro Penning ion source. Background Art

[0002] At present, cyclotron accelerators are devices that use magnetic and electric fields to make charged particles perform cyclotron motion, and are repeatedly accelerated by high-frequency electric fields during motion. They are important instruments in high-energy physics, among which the superconducting isochronous cyclotron accelerator (a branch of superconducting cyclotron accelerators) is the core equipment of medical proton therapy accelerators. Medical proton therapy accelerators can use protons and heavy ion rays in the microscopic world to treat tumors. It is the most advanced radiotherapy technology in the world today. Only a few developed countries have mastered and applied this technology.

[0003] The existing plasma is generally generated by a Penning ion source. Hydrogen enters the anode tube through a hydrogen channel on one side of the anode tube. A voltage of thousands of volts is applied between the anode tube and the cathode. A large amount of plasma is formed through the collision of electrons and neutral gas molecules.

[0004] Therefore, the number of electrons emitted at one time is closely related to the structure of the cathode. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a micro Penning ion source, which greatly increases the number of primary electron emissions by increasing the surface area of ​​the cathode end.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a micro Penning ion source, comprising an anode tube, cathodes arranged at both ends of the anode tube, and a shell covering the cathode and the anode tube; a plurality of clustered protrusions are arranged on the end faces of the cathodes arranged opposite to each other; a hydrogen channel connecting the anode tube with the outside is opened on the shell at at least one end of the cathode, and a lead-out slit is opened in the middle position of the anode tube.

[0007] By adopting the above technical solution, hydrogen enters the two ends of the anode tube through the hydrogen channel and is ionized. The electrons move in a spiral line in the anode tube. During the movement of the electrons, the electrons collide with the neutral gas molecules in the anode tube, thereby forming a large amount of plasma. The plasma is drawn out from the lead-out slit to form a particle beam. Due to the cluster-type protrusion structure formed on the cathode surface, the cathode surface area is increased by more than 10 times, the cathode emission coefficient is changed, the electron emission amount is increased, and thus the electron emission density is increased.

[0008] Preferably: an outer cover made of insulating material is provided on the cathode, and a space for accommodating hydrogen is reserved between the end of the cathode and the inner wall of the outer cover.

[0009] By adopting the above technical solution, the outer cover made of insulating material can insulate the cathode from the shell and the cathode from the anode tube, so that plasma can be generated normally.

[0010] Preferably: the outer cover comprises a horizontal barrel-shaped quartz glass outer cover, two cathodes are arranged at both ends of the outer cover and the cathodes and the outer cover are arranged coaxially, and the cluster-shaped protrusions are arranged toward the opening of the outer cover.

[0011] By adopting the above technical solution, the outer cover made of quartz glass is resistant to high temperatures and can still maintain good insulation performance after being sputtered by tantalum vapor after the ion source is working.

[0012] Preferably: the surface of the cluster-shaped protrusions is smooth and evenly transitioned, and the cluster-shaped protrusions are evenly distributed on the end surface of the cathode.

[0013] By adopting the above technical solution, the smooth surface and uniform transition can avoid the formation of tips of cluster-type protrusions, thereby reducing the possibility of field-controlled emission instability caused by the increase of the cumulative time of the Penning discharge point.

[0014] Preferably: the surface of the cluster-shaped protrusions is in a smooth hemispherical shape, and two adjacent cluster-shaped protrusions are in contact with each other.

[0015] By adopting the above technical solution, the cluster-shaped protrusions are in a smooth hemispherical shape, and two adjacent cluster-shaped protrusions abut against each other, which can avoid the cluster-shaped protrusions from forming sharp points and reduce the possibility of field-controlled emission instability caused by the increase in the cumulative time of the Penning discharge point.

[0016] Preferably: a primary electron collimator is provided at the opening of the outer cover, and the primary electron collimator is arranged coaxially with the cathode.

[0017] By adopting the above technical solution, primary electron collimation is beneficial to the formation of plasma and stabilizes the plasma, and can stabilize the plasma after the ion beam is extracted.

[0018] Preferably: the anode cylinder includes a cylinder whose two ends are respectively in direct contact with two primary electrons and an anode cavity opened inside the cylinder, the anode cavity is connected to the outer cover, the anode cavity is in a uniform cylindrical cavity shape, and the inner side walls of the cylinder are arranged in a uniform reduced diameter shape toward the two ends of the anode cavity.

[0019] By adopting the above technical solution, hydrogen enters from the end chamber, and the plasma is gathered in the middle chamber driven by the electromagnetic field, and then leaves from the middle chamber, thereby improving the extraction efficiency.

[0020] Preferably: the cathode is made of 100% tantalum and the anode tube is made of tungsten-copper alloy with 70% tungsten.

[0021] By adopting the above technical solution, the tungsten-copper alloy has the characteristics of high temperature resistance, and the tantalum itself is relatively stable, so that the cathode is not easy to undergo chemical reactions during ionization, thereby improving working stability and service life.

[0022] Preferably: the wall thickness of the side of the cylinder facing away from the lead-out slit is greater than the wall thickness of the side of the cylinder with the lead-out slit.

[0023] By adopting the above technical solution, the length of the lead-out slit is shorter, thereby shortening the movement time of the plasma in the lead-out slit, and the inner wall thickness on the other side is larger, thereby making the hydrogen channel longer and increasing the amount of hydrogen entering.

[0024] Preferably: the housing comprises a C-shaped shell and fin plates arranged on both sides of the shell, and the fin plates are provided with locking components for driving the two sides of the shell to move relative to each other.

[0025] By adopting the above technical solution, the locking assembly can form a tight fit structure between the anode and the outer sleeve, prevent hydrogen from overflowing, increase gas pressure stability, improve discharge stability, and increase cathode life, thereby increasing the life of the ion source.

[0026] In summary, the present invention has the following beneficial effects compared with the prior art:

[0027] 1. Due to the cluster-type protrusion structure formed on the cathode surface, the cathode surface area is increased by more than 10 times, the cathode emission coefficient is changed, the electron emission amount is increased, and thus the electron emission density is increased;

[0028] 2. The cluster-shaped protrusions are in a smooth hemispherical shape, and two adjacent cluster-shaped protrusions are in contact with each other, which can avoid the formation of sharp tips of the cluster-shaped protrusions and reduce the possibility of field-system emission instability caused by the increase of the cumulative time of the Penning discharge point. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is an axonometric view of an embodiment;

[0030] Figure 2 Schematic diagram showing the cathode structure in the embodiment.

[0031] Figure numerals: 1. outer shell; 11. shell; 12. fin plate; 13. locking assembly; 2. anode cylinder; 21. cylinder body; 22. anode cavity; 3. cathode; 31. clustered protrusion; 4. lead-out groove; 5. primary electron alignment; 6. outer cover; 7. threaded connection assembly; 8. water cooling assembly; 9. hydrogen channel. DETAILED DESCRIPTION

[0032] Example: A micro Penning ion source, see Figure 1 and Figure 2, comprising a cylindrical shell 1, the shell 1 comprising a plate-shaped shell 11 bent into a tubular shape and fins 12 respectively fixed on both sides of the shell 11, the fins 12 are provided with a locking assembly 13 for locking and abutting the two fins 12 together, the locking assembly 13 in this embodiment is a bolt connected to the two fins 12, a nut is threadedly connected to the bolt, the two fins 12 are abutted together by the cooperation of the bolt and the nut, and the two ends of the two fins 12 are respectively aligned. The inside of the shell 1 is fixedly connected with an outer cover 6 made of quartz glass, the outer cover 6 is a horizontally arranged tube with two ends connected, the openings of the two outer covers 6 are arranged oppositely, and a cathode 3 in the shape of a stepped shaft is inserted on the outer cover 6, each cathode 3 is inserted at the end of one outer cover 6 facing away from the other outer cover 6, and a space for accommodating hydrogen is left between the end of the cathode 3 and the inner wall of the outer cover 6. The other end of the outer cover 6 is fixedly provided with a primary electron collimator 5, and the end face opposite to the stepped cathode 3 is the end face with the largest area, and the cathode 3, the outer cover 6 and the primary electron collimator 5 are all arranged coaxially with the outer shell 1. The opposite end faces of the two cathodes 3 are fixedly provided with hemispherical clustered protrusions 31, and the surface roughness of the clustered protrusions 31 is Ra0.1. The bottom sides of the two adjacent clustered protrusions 31 abut against each other, and the clustered protrusions 31 are evenly distributed on the end faces of the cathode 3. The cathode 3 in this embodiment is made of 100% tantalum. An anode cylinder 2 is fixedly provided inside the outer shell 1 between the two cathodes 3, and the anode cylinder 2 is made of tungsten-copper alloy, in which the tungsten content is 70%. The anode cylinder 2 includes a cylinder 21 and an anode cavity 22 opened inside the cylinder 21. The anode cavity 22 is in a uniform cylindrical cavity shape. The two ends of the inner wall of the cylinder 21 are arranged in a uniformly reduced diameter shape toward the two ends of the anode cavity 22. The anode cavity 22 is connected to the internal space of the two outer covers 6 at the same time. The two primary electron collimators 5 are respectively abutted at the two ends of the cylinder 21. The anode cavity 22 is arranged coaxially with the cathode 3. A hydrogen channel 9 is opened on the outer cover 6 at one cathode 3 to connect the anode cavity 22 with the outside world. The hydrogen channel 9 is located between one primary electron collimator 5 and one cathode 3. The housing 1 and the cylinder 21 are jointly provided with an outlet groove 4 that is recessed toward the anode cavity 22. The cylinder 21 in the outlet groove 4 is provided with an outlet slit (not shown in the figure) that connects the anode cavity 22 with the outside world. The outlet groove 4 makes the wall thickness of the cylinder 21 on the side facing away from the outlet slit greater than the wall thickness of the cylinder 21 on the side with the outlet slit. In addition, a threaded connection component 7 and a water cooling component 8 are respectively fixed at both ends of the shell 1. The end of the cathode 3 with a smaller end surface area extends out of the outer cover 6 and the outside of the shell 1 and is threadedly connected to the threaded connection component 7. The threaded connection component 7 is fixedly connected to the water cooling component 8, and the water cooling component 8 is used to cool the cathode 3.

[0033] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A micro Penning ion source, characterized in that: The invention comprises an anode cylinder (2), cathodes (3) arranged at both ends of the anode cylinder (2), and a shell (1) covering the cathode (3) and the anode cylinder (2); a plurality of cluster-shaped protrusions (31) are arranged on the end faces of the cathodes (3) arranged opposite to each other; a hydrogen channel (9) for connecting the anode cylinder (2) with the outside is provided on the shell (1) at at least one end of the cathode (3); and a lead-out slit is provided at the middle position of the anode cylinder (2); The surface of the cluster-shaped protrusions (31) is smooth and evenly transitioned, and the cluster-shaped protrusions (31) are evenly distributed on the end surface of the cathode (3); The surface of the cluster-shaped protrusions (31) is in a smooth hemispherical shape, and two adjacent cluster-shaped protrusions (31) are in contact with each other.

2. The micro Penning ion source according to claim 1, characterized in that: An outer cover (6) made of insulating material is sleeved on the cathode (3), and a space for accommodating hydrogen is reserved between the end of the cathode (3) and the inner wall of the outer cover (6).

3. The micro Penning ion source according to claim 2, characterized in that: The outer cover (6) comprises a quartz glass outer cover (6) in a horizontal barrel shape, two cathodes (3) are arranged at two ends of the outer cover (6), the cathodes (3) and the outer cover (6) are arranged coaxially, and the cluster-shaped protrusions (31) are arranged toward the opening of the outer cover (6).

4. The micro Penning ion source according to claim 2, characterized in that: A primary electron collimator (5) is provided at the opening of the outer cover (6), and the primary electron collimator (5) is coaxially arranged with the cathode (3).

5. The micro Penning ion source according to claim 1, characterized in that: The anode cylinder (2) comprises a cylinder (21) whose two ends are respectively in contact with two primary electron collimators (5) and an anode cavity (22) provided inside the cylinder (21). The anode cavity (22) is connected to the outer cover (6). The anode cavity (22) is in a uniform cylindrical cavity shape. The two ends of the inner side wall of the cylinder (21) are arranged in a uniform reduced diameter shape toward the two ends of the anode cavity (22).

6. The micro Penning ion source according to claim 5, characterized in that: The anode cylinder (2) is made of tungsten-copper alloy, wherein the tungsten content is 70%.

7. The micro Penning ion source according to claim 1, characterized in that: The wall thickness of the side of the cylinder (21) facing away from the lead-out slit is greater than the wall thickness of the side of the cylinder (21) provided with the lead-out slit.

8. The micro Penning ion source according to claim 2, characterized in that: The housing (1) comprises a C-shaped shell (11) and fin plates (12) arranged on both sides of the shell (11), and the fin plates (12) are provided with locking components (13) for driving the two sides of the shell (11) to move relative to each other.

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