KR101501456B1 - Magnetic device for ecr ion source and system thereof - Google Patents

Abstract

The present invention relates to a plasma processing apparatus, A plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; A first solenoid lens including a six-pole magnet winding for generating a magnetic field in the circumferential direction formed around the plasma container, the first solenoid lens being installed inside the cryo refrigerator; And an ECR ion source system including a second solenoid lens that adjusts the magnitude and incidence angle of the beam compensated for by the first solenoid lens and is provided outside the cryo freezer.
Through the above-mentioned ECR ion source system, the present invention can increase the efficiency of the entire accelerator by forming a small-sized and good quality beam by adjusting the two solenoid lenses, and constitute a highly reliable and economical cryostat system There is an effect that can be done.

Description

TECHNICAL FIELD [0001] The present invention relates to a magnetic field generating device for an ECR ion source and a system including the same.

The present invention relates to an apparatus for generating a magnetic field for an ECR ion source and a system including the ECR ion source, and more particularly, to an ECR ion source capable of obtaining a higher number of polyvalent ions and a larger current ion beam, And a system including the same.

In order to produce such a radioactive ion beam (or a radioisotope beam), an accelerated ion beam is injected into various kinds of targets so that it can be transmitted through an in-flight system or an isotope separation on line (ISOL) system Thereby producing a radioactive ion beam.

In North America, Japan, and Europe, large accelerators are being designed or constructed for the production of radioactive ion beams as essential facilities for next-generation nuclear physics research. In the case of the Rare isotope accelerator (RIA) Using a superconducting linear accelerator accelerates all the particles in a nuclear chart to hundreds of meV / u (nuclear energy per subunit), making it possible to use both in-flight and ISOL methods.

In order to increase the acceleration efficiency and produce high energy radiation, interest in radiation accelerator using heavy ion has been increased. To this end, ionization devices for making heavy ions have been actively studied.

ECR (Electron Cyclotron Resonance) ion source is one of the most effective ways to generate the multivalent ions of various atoms. This ECR ion source has a strong magnetic mirror structure in the ion source, By using resonance, electrons can be intensively heated to several keV or more, so that electrons located in the atomic interior of the atom can be separated from the orbit.

The most important point in designing such an ECR ion source is to not only have a strong magnetic field structure to increase the sealing efficiency of high energy electrons but also to make the resonance efficiency efficient and to increase the ionization efficiency, And to design a multipole magnetic field generator to make it.

Such a multipolar magnetic field generator has a very complicated structure for designing a strong magnetic field, which is not suitable for application to general ECR ion sources.

In addition, the multipolar magnetic field generator applied to the ECR ion source is made up of magnets having various kinds of magnetization directions. As a result of being influenced by an external magnetic field, magnetic force due to magnetic stresses There is a problem in that it becomes weaker and there is a problem that a strong magnetic field is not formed if a magnet having a strong coercive force is used to overcome the weakening of the magnetic force due to magnetic stress.

As such, the current world-class level of development of superconducting ECR ion sources has not been able to fully achieve the required output of a heavy ion accelerator, so research and development is underway and even though this target is achieved, The better the performance of the ECR ion source, the higher the level of experimentation can be.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic field generator for an ECR ion source capable of obtaining a large current of a multiform ion beam by improving the ion beam transport system and a system .

It is still another object of the present invention to provide a magnetic field generator for an ECR ion source capable of increasing the efficiency of the entire accelerator through adjustment of two solenoid lenses and a system including the same.

According to an aspect of the present invention, there is provided a plasma display apparatus comprising: a plasma container; A plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; And a six pole magnet winding for generating a magnetic field in the circumferential direction formed around the plasma vessel.

Wherein the axial direction component magnetic field at the plasma vessel inlet side is not less than 4.4 tesla and the axial direction component magnetic field at the exit side is not less than 3.2 tesla, the magnitude of the circumferential magnetic field is not less than 2.2 tesla, Five solenoid coils are installed, and the electron resonance region can be controlled through the adjustment of the minimum magnetic field gradient by the currents of the three coils.

In addition, the present invention provides a plasma display panel comprising: a plasma container; A plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; And a coil of a six-pole magnet for generating a magnetic field in the circumferential direction formed around the plasma vessel, wherein the first solenoid lens installed inside the cryo freezer and the first solenoid lens for adjusting the size of the beam compensated for by the first solenoid lens And an ECR ion source system including a second solenoid lens provided outside the cryo freezer, the incident angle being adjusted.

As described above, the present invention provides a multipolar magnetic field generating apparatus for an ECR ion source.

Thereby, there is an effect that a higher number of multi-ion ions and a larger current ion beam can be obtained than in the superconducting ECR ion source of the other apparatus.

In addition, by adjusting the two solenoid lenses, it is possible to make a beam of small size and good quality, so that the efficiency of the entire accelerator can be increased, and a reliable and economical Cryo system can be constructed.

1 is a perspective view showing a configuration of a main magnet of a superconducting ECR ion source constituted by the present invention;
FIG. 2 is a graph showing the distribution of magnetic field components of axial components realized by the five superconducting solenoid magnets according to FIG. 1; FIG.
FIG. 3 is a graph showing the distribution of magnetic field components in the circumferential direction, which is realized by the superconducting two-pole magnet according to FIG. 1; FIG.
4 is a plan view showing possible winding methods of a two-pole magnet;
FIG. 5 is a graph showing the relationship among the five solenoid coils constituting the superconducting ECR ion source, the first solenoid lens installed in the cryotank and the second solenoid lens installed outside the cryotank, the ion source being a spherical magnet wound in a saddle- .
6 is a graph of magnetic field waveforms of axial components due to electromagnets and yoke structure according to FIG.
7 is a layout diagram of structures installed inside an electromagnet in an ECR plasma.
8 is a layout diagram of structures installed outside an electromagnet in an ECR plasma.
Fig. 9 is a layout diagram of structures installed axially on both sides of the electromagnet; Fig.
Fig. 10 is a graph showing the thermal load of each region based on the structure and arrangement of the cryostat system and the thermal insulation conditions.
11 is a schematic diagram showing an example of beam transport by a single solenoid lens in a superconducting ECR ion source.
12 is a schematic diagram showing an example of beam transport by two solenoid lenses in a superconducting ECR ion source.
13 shows a simulation result showing that the quality of the beam is improved when two solenoid lenses are used to extract uranium multi-valent ion beams.
14 shows a simulation result showing that the beam quality is improved when two solenoid lenses are used to extract the proton beam.
15 is a cross-sectional view showing the entire configuration of a superconducting ECR ion source system including a multipole magnetic field generating apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of an apparatus for generating an ECR ion source multi-pole magnetic field and a system including the same will be described in detail with reference to the accompanying drawings.

Prior to this, terms and words used in the present specification and claims should not be construed as being limited to ordinary or dictionary terms, and the inventor should appropriately define the concept of the term to describe its invention in the best way The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

Fig. 1 is a perspective view showing the configuration of a main magnet of a superconducting ECR ion source constructed according to the present invention, and Fig. 2 is a graph showing the distribution of magnetic field components of axial components realized by the five superconducting solenoid magnets according to Fig. Graph. FIG. 3 is a graph showing the distribution of magnetic field components in a circumferential direction component realized by the superconducting magnetic pole magnet according to FIG. 1, and FIG. 4 is a plan view showing possible winding methods of the pole magnet.

Hereinafter, an ECR ion source multi-pole magnetic field generator according to the present invention will be described with reference to the drawings.

An ECR ion source multi-field magnetic field generator according to the present invention comprises: a plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; And a six pole magnet winding for generating a circumferential magnetic field formed around the plasma vessel.

Particularly, it is preferable that the plasma component inlet side axial component magnetic field is 4.4 tesla or more, the outlet side axial component magnetic field is 3.2 tesla or more, and the circumferential magnetic field size is 2.2 tesla or more.

Also, in the multipole magnetic field generator according to the embodiment of the present invention, five of the annular superconducting solenoid coils are provided, and the electron resonance region can be controlled through the adjustment of the minimum magnetic field gradient by the currents of the three coils .

FIG. 1 shows the structure of a superconducting magnet for generating an axial magnetic field and a circumferential magnetic field, which are the basic magnetic field structures of a superconducting ECR ion source constructed by applying the present invention, in which five superconducting solenoid magnets are arranged to make an axial magnetic field , Six permanent magnets are arranged long along the outer wall of the plasma vessel to create a circumferential magnetic field structure, all of which can be maintained at 4K by liquid helium in the cryotank.

As described above, the shape of the axial magnetic field realized by the five solenoid magnets (St0, St1, St2, SL1, SL2) can be shown graphically as shown in FIG. By the current distribution of the middle three coils, it is possible to control the magnetic field by a strong magnetic field mode such as green waveform and a high frequency resonance control mode such as red waveform. In the strong magnetic field mode, the maximum magnetic field on the plasma vessel inlet side is more than 4.4 tesla and the axial component magnetic field on the exit side is more than 3.2 tesla.

As shown in FIG. 1, the circumferential magnetic field shape realized by the six superconducting two-pole magnets arranged along the plasma vessel can be represented by a graph according to FIG. The size of the magnetic field in the circumferential direction on the outer wall of the plasma container can be obtained by the magnetic field of circumferential radius of 2.2 T by six yoke magnets wound in a saddle shape on the vessel wall and a yoke mounted in the center of each magnet shown in green in Fig. have. As shown in FIG. 4 (c), the winding of the pole magnet can use a special jig to saddle the winding of the container along the curvature of the container wall.

The present invention relates to a plasma processing apparatus, A plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; A first solenoid lens installed inside the cryo freezer in addition to a multipole magnetic field generator including a six pole magnet winding for generating a magnetic field in the circumferential direction formed around the plasma vessel; And a second solenoid lens arranged outside the cryo freezer to adjust the size and incidence angle of the beam compensated by the first solenoid lens.

The five solenoid coils constituting the superconducting ECR ion source having the above-described constitution, the first solenoid lens installed in the cryotank and the second solenoid lens installed in the cryotank, The arrangement of the solenoid lenses is shown in Fig.

The ferromagnetic magnets and the Solanoid electromagnets are assembled in a structure that can sufficiently absorb the strong electromagnetic force acting on each other. The outermost part of the cryotank can shield the magnetic field generated by the electromagnets and realize the required magnetic field line waveform. The magnetic field waveforms of the axial components due to the electromagnets and the yoke structure thus designed are shown in the graph shown in FIG.

As shown in the graph of FIG. 6, the magnetic field structure of various waveforms can be produced by the current distribution of the respective electromagnets, and the magnetic field structure can affect the performance of the ECR ion source under various conditions.

In particular, a first solenoid lens L1 installed in the cryo freezer; And a second solenoid lens (L2) provided outside the cryo freezer to adjust the size and incident angle of the beam compensated for by the first solenoid lens.

By installing the first solenoid lens L1 in the cryo freezer as described above, it is possible to compensate for the spread of the beam due to the space charge as quickly as possible, and by providing the second solenoid lens L2 outside the cryo freezer, The beam having a small beam size and a small divergence angle can be maintained before and after the electromagnet by appropriately adjusting the beam size and the incident angle of the beam.

Such an effect can be achieved by two solenoid lenses according to the simulation results to be described later, that is, at the entrance of the mass analysis electromagnet which is the next beam line component, a beam close to parallel with a beam of a smaller size.

In the superconducting ECR ion source, it is necessary to extract various ion beams in the form of various electric charges, and finally, only the ion beam of the required number of electric charges is picked out. The simulations of the designed ion source beam, The design results were verified using beam extraction simulation code.

Cryo systems that superconducting magnets are cooled to 4K in the superconducting ECR ion source and maintained at that temperature have the following problems. The parameters reflected in the design for the heat shield basically affect the performance of the ion source. Reliability is determined. The position of each structure in the radial direction and the axial direction from the ECR plasma reflected in the ion source design to the outer surface of the vacuum chamber of the cryostat system is shown in FIG. 7, FIG. 8, and FIG. FIG. 7 is a layout diagram of structures installed inside the electromagnet in the ECR plasma, and FIG. 8 is a layout diagram of structures installed outside the electromagnet in the ECR plasma. 9 is a layout diagram of structures installed axially on both sides of the electromagnet.

The thermal loads that the Cryo system should bear include 300 K of radiant heat from the object, conduction heat through the gas or structure, resistance heat from the electromagnet lead wire, and X-rays from the ECR plasma, Conducted heat can be suppressed through the use of nonconductors. In ECR plasma, bremsstrahlung X-rays with high energy electrons collide with plasma particles or vessel walls and generate a continuous spectrum. Since the emission energy reaches the MeV region, it can accumulate in the superconducting magnet through the material, For this purpose, a tantalum (Ta) plate of 3 mm thickness, which has a high attenuation factor of X-rays and is relatively easy to process, is used. A plastic disc is inserted for thermal insulation between the thermal insulation and the liquid nitrogen container, and a structure for fixing the liquid nitrogen container to the vacuum container at room temperature is made of G10 strip and stainless steel.

FIG. 10 shows data obtained by estimating the thermal load of each region based on the structure and arrangement of the cryogenic system and the thermal insulation conditions. The cooling of the 70 K heat shield is cooled using a 50 K freezer, and the electromagnets requiring 4 K cooling close to 1000 kg in mass, so once cooled down to 70 K with liquid nitrogen and cooled with liquid helium from 70 K After that, in the temperature maintenance step, the refrigerator and the helium recondenser constituting the self-circulating circuit are charged.

The superconducting ECR ion source needs to extract various kinds of ions from hydrogen ions with a small mass number to uranium ions with a very large mass number in the form of multi-valent ion beams. Therefore, the beam extraction characteristics of the ion source must be different depending on the type of the ion beam to be extracted from the ion source. Therefore, the beam source of the ECR ion source must be capable of extracting the optimum beam reflecting these various changing conditions.

In particular, the beam extraction voltage can be adjusted within 30 kV, and the gap of the beam extraction electrode can be adjusted manually by adjusting the thickness of the extraction electrode fixing ring so that experiments on various beam types can be performed So that the distance between the extraction port and the mass analysis electromagnet can be minimized to maximize the beam transport efficiency.

However, the decelerating electrode can be added to the deceleration electrode instead of omitting the electrode gap fine adjustment function because electrons accelerating in the opposite direction of the beam to prevent reverse electrons entering the ion source chamber as well as in view of beam optics. In most superconducting ECR ion sources, the distance between the beam outlet and the solenoid lens is determined by the size of the cryo cooling system for cooling the superconducting magnet.

FIG. 11 is a schematic view showing an example of beam transport by a single solenoid lens in a superconducting ECR ion source, and FIG. 12 is a schematic diagram showing an example of beam transport by two solenoid lenses in a superconducting ECR ion source.

11 and 12, when the current of the outgoing beam is large, even when the beam is drawn out optimally in the ion source drawing system, the beam spreads largely while reaching the solenoid lens area by the space charge, Even if the beam is converged and transmitted to the electromagnet entrance in the form of a parallel beam as possible, the characteristics of the beam that has passed through the electromagnet through the electromagnet are analyzed by the already-enlarged beam. Configure the system with two solenoid lenses.

Particularly, by installing the first solenoid lens in the cryocooler, it is possible to compensate the spread of the beam by the space charge as soon as possible, and then the size and incident angle of the beam at the electromagnet entrance are appropriately adjusted by the second solenoid lens, The beam having a small divergence angle can be maintained before and after the electromagnet.

In the superconducting ECR ion source, it is necessary to extract various ion beams into various charge types, and to select only the ion beam of the necessary charge number finally, the simulation of the ion source beam, which is the designed ion source beam, The design results were verified using symmetric 3D simulation beam extraction simulation code.

FIG. 13 is a simulation result showing that the quality of the beam is improved when two solenoid lenses are used for drawing uranium multi-valent ion beams, and FIG. 14 is a simulation result showing that when two solenoid lenses are used to draw the proton beam, The simulation results show that the quality is better.

13 shows the simulation result of the polyvalent uranium beam withdrawal, which is one of the main radionuclides targeted by the superconducting ECR ion source, and the result of simulating the same by applying the proton 10 mA single beam to the same conditions is shown in FIG. 14 It looked. In each case, the top beam extraction simulation results are the result when the beam drawn from the ion source passes through a system without a solenoid lens, the second is the result when there is one solenoid lens, The result of the last line is the result of two solenoid lenses, one inside the cryo tank and one outside the cryo tank.

As can be seen from the simulation results, it can be seen that the two solenoid lenses can finally produce a near-parallel beam with a smaller beam at the entrance of the mass analyzer, which is the next beamline component.

15 is a cross-sectional view showing the entire configuration of a superconducting ECR ion source system including a multipole magnetic field generating apparatus according to the present invention.

The superconducting ECR ion source designed as described above can be expected to be disassembled and reassembled from time to time for purposes such as replacement of oven lifetime for uranium beam withdrawal, adjustment and maintenance of beam gap system, and the like. In order to perform the maintenance including the reassembly effectively, it is designed to be disassembled into six configurations as described below.

In a first configuration, the superconducting magnet bundle includes five solenoid coils, a two-pole magnet, a superconducting solenoid lens, and a cryo refrigerator system. Next, in a second configuration, the ECR plasma vessel comprises a high voltage insulation tube and a thallium X-ray shielding tube. In a third configuration, the ion source input port includes an RF port, a bias disk, a gas supply line, an oven system, and a vacuum exhaust system. In a fourth configuration, the beam outlet port includes a normal conducting solenoid lens, a beam extraction electrode, a high voltage insulation, and a vacuum exhaust system. In a fifth configuration, the mass spectrometry system includes a mass spectrometry electromagnet, a beam angle tuning magnet, and a beam diagnostic port. In a sixth configuration, the RF system includes an RF vacuum window, a DC brake, and a 28 GHz RF system.

For the ion source plasma chamber which confines the ECR plasma, a 2 mm PEEK with a Cryo system and a ceramic ring brazed to a vacuum container with a beam extraction electrode are insulated with a DC brake from the RF system. In particular, the assembly structure of the beam extraction port and the plasma vessel connecting the beam extraction electrodes in the entire structure does not use the bolt, and the O-ring It is easy to maintain by using inner / outer compression bonding method.

The ECR ion source multi-pole magnetic field generator according to the present invention described above and its system can increase the efficiency of the entire accelerator because it can make small size and good quality beam by adjusting the two solenoid lenses, There is an effect that the Cryo system can be configured.

Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

The present invention is applied to the ECR ion source system field.

Claims (5)

delete delete delete delete A plasma vessel; A plurality of annular superconducting solenoid coils for generating an axial component magnetic field of the plasma vessel; And a six-pole magnet winding for generating a circumferential magnetic field formed around the plasma vessel,
A first solenoid lens installed inside the cryo freezer; And
And a second solenoid lens arranged outside the cryo freezer to adjust the size and incidence angle of the beam compensated for by the first solenoid lens,
Wherein the axial direction component magnetic field of the plasma vessel inlet side is not less than 4.4 tesla, the axial direction component magnetic field of the outlet side is not less than 3.2 tesla, and the magnitude of the circumferential magnetic field is not less than 2.2 tesla,
Wherein five of the annular superconducting solenoid coils are provided, and the electron resonance region can be controlled by adjusting the minimum magnetic field gradient by the currents of the three coils.

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