KR0137305B1 - High current ion accelerator tube - Google Patents

Abstract

The present invention provides a new acceleration tube structure for acceleration of a large current beam of an acceleration tube used in a DC-type accelerator that accelerates by applying a constant voltage to a charged particle, and a large current for improving ion optical characteristics, which are charged particle beam focusing characteristics, and prefabricated acceleration for ion acceleration. As regards the tube, by accelerating the position of the acceleration electrodes with the insulator, it has a structure of an acceleration tube having a strong focusing characteristic according to the formation of a strong electric field between the electrodes, the shielding effect of the X-rays generated in the electrode accordingly Secondary electron reflection electrode at the rear end of the accelerator tube is configured to minimize the X-ray generation due to the reverse acceleration of the secondary electron, O-ring and flange tightening assembly of the insulator and the conductor electrode and vacuum sealing It is characterized by an acceleration tube adopting a prefabricated type that is easy to disassemble by adopting the method.

Description

Prefabricated Accelerator Tube for High Current Ion Acceleration

1 is a conventional DC accelerator tube (a) is a cylindrical DC accelerator tube

(b) is a deflected dc accelerator tube.

Figure 2 is a configuration of the high speed assembly prefabricated acceleration tube of the present invention.

3 is a diagram illustrating focusing characteristics according to ion currents in the strong focusing accelerator tube of the present invention.

Explanation of symbols on the main parts of the drawings

(1): high voltage side flange (2): first acceleration electrode

(3): second acceleration electrode (5): insulator

(6): Equipotential electrode (7): O-ring

(8): Ground side flange (9): X-ray shield tube

(11): Insulator rod (11): Nut

(12): Electrode Reflective Electrode 13: Terminal and High Voltage Wire

(14): Beam next step (15): Cooling water channel

The present invention provides a novel accelerator tube structure for acceleration of large current beams in an accelerator tube used in a DC-type accelerator that accelerates by applying a constant voltage to the charged particles, and an ion optics characteristic which is a charged particle beam focusing characteristic. The present invention relates to a prefabricated accelerator tube for large current ion acceleration.

In general, DC accelerators such as Cockcroft-Walton and Van de Graaff have charged particles such as ions or electrons emitted from an ion source or an electron gun. In order to accelerate to have a high energy, a voltage of tens of thousands to millions of volts is applied between the ion source and the target (the target is usually at the pick-up potential for ease of use), and is a passage maintained in a high vacuum between them. By placing a tube, charged particles such as ions are accelerated along this place.

In order to obtain a high electric field in a vacuum, a conventional accelerator tube is configured as a multi-stage or more multi-stage type in which an insulator and a conductor isoelectric plate are alternately stacked as shown in FIG. 1, and the insulator and the conductor and Vacuum seal is made of adhesive or ceramic-metal brazing. Once manufactured, it is difficult to access the inside of the tube, so it is impossible to remove the contaminants on the surface of electrodes and insulators generated during long-term use. In case of problems such as electrode damage or insulator damage due to high voltage discharge, it was not possible to repair it and replaced it with a new one. Beam focusing characteristics also caused electric field to dominate the strength of focusing force at the inlet of the acceleration tube because the insulator and electrode are multi-stage. The electric field gradient is weak so that it can To stand for more than several tens of mA high current ion beam is difficult beam is emitted by the space charge of the ion beam itself, the collision acceleration, and the acceleration tube wall has been difficult due to the acceleration is stable discharge problems caused by this. In addition, in case of multi-stage ion accelerator tube, it is difficult to shield radiation due to the structural shielding of electrodes and insulators against X-rays generated in the reversed electrons accelerated during ion acceleration. Shielding the entire area of the shield, the size of the shield is large, the device is not only large and weight, but also the manufacturing cost of the shield accordingly. Here, the electrode and the insulator are uniformly dispersed, and most of the X-rays generated by the electrodes collide with the insulator wall without shielding, and the electrons are separated from the atoms by photoelectric effects from the wall-constituting atoms. The discharge path of the insulator is created, so that discharge occurs frequently through the insulator, and the electric field due to the space charge from which the charged charges are distorted the original accelerating electric field changes the path of the charged particles, which accelerates, thereby making the particle beam loss as well as the device unstable. There was a disadvantage.

Therefore, the conventional multi-stage accelerator tube has many problems when the beam current is a large current of 10 mA or more.

An object of the present invention is to improve the above problems of the prior art to provide a large current ion accelerator of the tens-hundreds of mA class current that is industrially emerging.

In order to achieve the above object, in the accelerator tube of the high current accelerator, by accelerating the position of the acceleration electrodes with the insulator, the strong focusing characteristics according to the formation of a strong electric field between the electrodes, the X-ray shielding effect generated in the electrode, It has a structure of an acceleration tube having a discharge preventing function according to the structure, and is arranged to minimize the X-ray generation due to the reverse acceleration of the secondary electrons by placing the secondary electron reflection electrode at the rear end of the acceleration tube, and the coupling between the insulator and the conductor electrode And vacuum sealing to complete the O-ring and flange tightening assembly configuration.

The present invention of the above characteristics has the same high-focusing characteristics, to prevent the generation of X-rays, to effectively X-ray shielding, disassembly and assembly in order to accelerate the large current charged particle beam stably and efficiently The structure of this easy acceleration tube was devised. It is realized by adopting three-electrode system as the structure of the accelerator tube to obtain the strong electric field gradient in the acceleration cavity, which is effective to suppress and compensate the divergence of the beam itself when accelerating the large current charged particle beam. X-ray generation prevention is realized by placing an Electron Reflection Electrode behind the Accelerator Tube to prevent electrons present on the ground from accelerating in the opposite direction by moving to the accelerating gap and colliding with the electrode. By effectively arranging the generated X-ray acceleration tube electrode structure, the shielding effect is maximized to prevent the generated X-rays from reaching the insulator, thereby minimizing the discharge during vacuum to ensure stable acceleration. In addition, it is possible to remove contaminants by electrically cleaning the inside of the accelerator tube, and to use vacuum pre-closing method of electrodes and insulators using O-rings and flanges to reduce the vacuum load caused by the release gas emitted from the adhesive when the adhesive is used. Produced.

Hereinafter, the present invention will be described in detail with reference to FIGS. 2 and 3 of the accompanying drawings.

FIG. 2 shows a specific embodiment of the present invention, wherein the accelerator tube includes three metal cylinder accelerator electrodes 2, 3 and 4, an insulator 5, an O-ring 7, and an equipotential electrode 6. , The X-ray shield tube (9) is laminated in order between the high voltage side flange (1) and the ground side flange (8), and then the electrode is connected using a high-strength insulator rod (10) and a centering aid. It consists of fastening with the nut 11 while aligning, and is always possible to disassemble and assemble.

Unlike the conventional multistage type accelerator tube, the basic structure of the accelerator tube is separated from the position of the accelerator electrode and the position of the insulator, and is very strong between the first and second acceleration electrodes 1 and 2 without the influence of the insulator. The electric field can be obtained to obtain the strongly focused ion optical properties. Therefore, since the accelerator tube has a highly focused ion optical characteristic, as shown in FIG.

In addition, X-rays generated at each electrode position are attenuated by passing through multiple layers of conductors (2, 3, and 4) and hardly reach the insulators. Can be prevented. In addition, since the influence of the space charge existing on the wall of the insulator 5 is also shielded by each conductor electrode, it does not affect the charged particle movement at all. In the case of ion acceleration, the secondary electrons generated by the accelerated ion beam colliding with the neutral gas on the ground side or the beam dump 14 installed at the outlet of the accelerator tube are ground acceleration electrodes. (4) Next, the electron reflection electrode 12 is placed next to prevent negative acceleration of the secondary electrons by applying negative voltages of −2 and −3 kV through the insulated wire 13 from the outside. The beam difference step 14 serves to block ions that escape out of the accelerated ion beam, and the heat generated by the beam collision is cooled by the coolant flowing through the coolant passage 15 inside the flange 8 on the ground side. The material of the insulator (50) is made of fluorine resin (e.g. Teflon, etc.) or workable ceramic which has high electrical insulation strength, low gas emission in vacuum, and easy to machine, thereby increasing the surface electrical insulation of the inner and outer surfaces. In order to maintain the vacuum tightness, the insulator rod 10 uses high-strength insulating resin to maintain sufficient mechanical strength during the assembly of the accelerator tube. In order to increase the electrical strength of the surface, it is processed to have unevenness and is installed on the outside of the flanges (1, 8) and fastened by using the nut 11. The X-ray shield tube (9) is made of a thick metal cylinder It plays a role of radiation shielding to prevent X-rays generated from the accelerating electrode from being emitted to the outside.

The DC type accelerator tube according to the present invention has a strong electric field between metal electrodes in vacuum without the influence of an insulator by dividing the structure into an electrode part and an insulator part, thereby obtaining a strong focusing property, and suitable for acceleration of a large current ion beam of several tens of mA or more. By properly arranging the electrodes, effective X-ray shielding can prevent X-ray induced discharge and stably accelerate the ion beam. In addition, by installing an electron reflecting electrode at the rear end of the accelerator tube and applying a negative voltage to it, it is possible to effectively reduce the X-ray appearance due to the reverse acceleration of the secondary electrons, and by disassembling and cleaning the accelerator tube easily, especially by accelerating the large current. In the case of a pipe, sputtering caused by ion collision prevents a drop in electrical insulation strength caused by contamination of an insulator, and thus the life of the accelerator tube can be used semi-permanently.

The accelerator tube of the present invention constructed and acted as described above solves the main problems caused by the accelerator tube of the large current type industrial accelerator, and has been developed for industrial use. As an apparatus suitable for a large current accelerator such as an injector, the effect is expected.

Claims (1)

In an accelerator tube of a high current accelerator, three metal cylinders of acceleration electrodes (2, 3, 4), an insulator (5), an O-ring (7), an equipotential electrode (6), and an X-ray shield tube (9) ) Is laminated between the high voltage side flange (1) and the ground side flange (8) in sequence, and then fastened with nuts (11) while aligning the electrodes using a high-strength insulator rod (10) and a centering aid. However, in the accelerator tube of the high current accelerator, the position of the accelerator electrodes is remote from the insulators, and the distance between these electrodes is sufficiently narrowed to maintain the strong focusing property, and the structure and the insulator having the electron reflecting electrode 12 at the rear end of the accelerator tube. Prefabricated acceleration tube for high current ion acceleration, characterized in that the coupling of the electrode and the vacuum sealing is composed of O-ring and flange.