JP5481411B2 - Laser ion source and laser ion source driving method - Google Patents

Description

  Embodiments described herein relate generally to a laser ion source that generates ions by laser light irradiation, and more particularly to a laser ion source having a multivalent ion selection mechanism and a method for driving the laser ion source.

  In recent years, cancer treatment methods using high-energy carbon ion irradiation have been developed. In fact, ion accelerators have been installed in general hospitals, and treatment has begun. In order to further improve the performance of this type of apparatus, an ion source that generates high-density hexavalent carbon ions is indispensable. Since conventional ion sources using microwave discharge plasma are ineffective in this respect, development of a new ion source is strongly desired.

  Laser ion sources have been developed as ion sources capable of generating high-density ion beams. This laser ion source condenses and irradiates laser light onto a target and ionizes the target with the energy of the laser light. Then, ions generated from the target are electrostatically extracted to generate an ion beam.

  However, this type of laser ion source has the following problems. That is, the ions transported from the laser ion source are mixed with ions having a plurality of valences depending on the energy and density of the laser beam. For this reason, although ions to be extracted are hexavalent carbon ions, ions having other valences are also released.

  By providing the downstream linear accelerator with a valence selection function, only hexavalent ions can be selected and used. However, in this case, ions with an unnecessary valence stay as dirt in the linear accelerator, which causes contamination of the electrode or causes discharge. In order to prevent this, it is necessary to periodically remove ions adhering in the linear accelerator. However, the linear accelerator is a very large and precise machine, and its maintenance involves a great deal of labor.

Japanese Patent No. 3713524 JP 2009-37764 A

  In the laser ion source described above, since ions of a plurality of valences are mixed and enter the downstream linear accelerator, unnecessary ions may stay in the linear accelerator, contaminate the electrode, and cause discharge. It was a challenge.

  The present invention has been made in order to solve the above-described problems, and is capable of suppressing the emission of unnecessary ions and capable of reducing contamination on the downstream linear accelerator side by unnecessary ions. It is an object of the present invention to provide a source and a method for driving a laser ion source.

  A laser ion source according to an embodiment of the present invention includes a container that is evacuated, an irradiation box that is disposed in the container and contains a target that generates multivalent ions when irradiated with laser light, and the irradiation box Ion beam extraction means for electrostatically extracting ions from the container and guiding them to the outside of the container as an ion beam, an electromagnetic lens for converging the ion beam extracted from the irradiation box by electromagnetic force, and a downstream side of the electromagnetic lens And an aperture that allows an ion beam focused at the position to pass therethrough.

  According to the embodiment of the present invention, it is possible to suppress emission of unnecessary ions, and it is possible to reduce contamination on the downstream linear accelerator side due to unnecessary ions.

1 is a cross-sectional view showing a schematic configuration of a laser ion source according to a first embodiment. Sectional drawing which shows the mode of selection of the ion beam in 1st Embodiment. (A) And (b) is a schematic explanatory drawing for demonstrating the principle of selection of the ion beam in 1st Embodiment. Sectional drawing which shows the principal part structure of the laser ion source concerning 2nd Embodiment. The top view which shows the principal part structure of the laser ion source concerning 3rd Embodiment. (A) is a top view which shows the modification of 3rd Embodiment, (b) is the top view and sectional drawing which show another modification. Sectional drawing which shows schematic structure of the laser ion source concerning 4th Embodiment. Sectional drawing which shows schematic structure of the laser ion source concerning 5th Embodiment. (A) And (b) is a schematic explanatory drawing for demonstrating the principle of selection of the ion beam in 5th Embodiment. Sectional drawing which shows schematic structure of the laser ion source concerning 6th Embodiment. Sectional drawing which shows schematic structure of the laser ion source concerning 7th Embodiment. (A) to (c) are schematic explanatory views for explaining the principle of ion beam selection in the seventh embodiment. Sectional drawing which shows schematic structure of the laser ion source concerning 8th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a sectional view showing a schematic configuration of a laser ion source according to the first embodiment of the present invention. 2 is an enlarged cross-sectional view of a part of FIG. 1 (a part surrounded by a broken-line circle).

  The laser ion source of the present embodiment includes an ion source main body 100, an ion source transport system 200, and a linear accelerator (RFQ) 300.

  The ion source main body 100 includes a vacuum vessel 10, a lead electrode 12, an irradiation box 20, and the like. The container 10 is made of stainless steel, and an irradiation box 20 for covering the laser irradiation unit is installed at the center of the container 10. In the irradiation box 20, an element that becomes an ion or a target 21 containing the element is installed. For example, a carbon plate member is selected as the target 21.

On the upper surface of the irradiation box 20, a window 22 for entering laser light is provided. Then, the laser beam 31 enters the irradiation box 20 through an optical system (not shown), and is focused on the target 21. As a light source for emitting laser light, a Co ₂ laser or an Nd-YAG laser can be used.

  The irradiation box 20 is supported by the insulating support 11, and a high voltage is applied by a high voltage power source (not shown). A positive potential is applied when generating a positive ion beam, and a negative potential is applied when generating a negative ion beam.

  A window 23 for taking out ions is provided on one side surface (right side surface in the figure) of the irradiation box 20. The extraction electrode 12 is installed so as to face one side surface of the irradiation box 20 where the window 23 is provided. The extraction electrode 12 is a disk-shaped conductor having a circular hole in the center, and is maintained at a ground potential in order to extract ions from the irradiation box 20.

  An exhaust port 13 is formed on the upper surface of the container 10, and a vacuum pump (not shown) is connected to the exhaust port 13 so that the inside of the container 10 is evacuated. An ion beam extraction unit (ion source transport unit 200) is formed on a side surface of the container 10 that faces the one side surface where the window 23 of the irradiation box 20 is formed. The take-out portion is configured by a cylinder 41 connected to one side surface of the container 10 and a flange 42 at the tip of the cylinder 41. The flange 42 is connected to the next linear accelerator 300. In the case where the ion implantation apparatus is used instead of the accelerator, a deflection apparatus or an electrostatic lens may be connected instead of the linear accelerator 300.

  In addition to the basic configuration so far, in the present embodiment, an electrostatic lens 51 for converging a multivalent ion beam is provided on the container 10 side of the cylindrical body 41, and an aperture 52 is provided on the linear accelerator side. The electrostatic lens 51 converges the ion beam by electrostatic force by, for example, three electrodes spaced apart in the axial direction. The aperture 52 has a small-diameter opening at the center. A valve 43 is provided between the flange 42 and the linear accelerator 200. The valve 43 is, for example, a gate valve or a butterfly valve attached so that the beam traveling path is an opening, and has a function of keeping the opening and closing of the beam passage conduit airtight.

  Next, the operation of the laser ion source configured as described above will be described.

  It is assumed that the inside of the container 10 is sufficiently exhausted by a vacuum pump or the like connected to the exhaust port 13. For example, a positive potential is applied to the irradiation box 20 and a ground potential is applied to the extraction electrode 12.

  In this state, when the target 21 is focused and irradiated with the laser beam 31 from a pulse-driven laser light source (not shown), the laser beam 31 focused on the target 21 causes a minute portion of the target 21 at the laser focusing point. Is heated to a high temperature. The portion heated to a high temperature is turned into plasma and emitted toward the space. The atoms and ions in the plasma also receive energy from the laser beam 31 and multivalent ions are generated.

  What is ejected into the space inside the irradiation box 20 is called an ablation plume or simply a plume. In the irradiation box 20, a window 23 is provided in the plume emission direction, and an extraction electrode 12 having a ground potential is provided outside the window 23. For this reason, ions are extracted from the irradiation box 20 by the electric field between the irradiation box 20 and the extraction electrode 12, and are simultaneously accelerated into an ion beam. The ion beam is further accelerated by the subsequent linear accelerator 300.

  By the way, the multivalent ion beam 33 drawn out from the ion source main body 100 is converged by the electrostatic lens 51 in the ion source transport system 200, but the convergence position (focal length) differs depending on each valence. Therefore, as shown in FIG. 2, it is possible to selectively extract only the ion beam 33a having the valence Z1 by installing the aperture 52 at the focal position of the ion beam 33a having the required valence Z1. An ion beam other than the valence Z1 that passes near the central axis passes through the aperture 52 without being blocked by the aperture 52, but the amount thereof is extremely small compared to the total amount, and contamination due to this hardly causes a problem. .

  FIG. 3 shows ion beams of various valences and how they converge. (A) is a figure which shows the positional relationship of the target 21, the lens 51, and the aperture 52, (b) is a figure which shows the relationship between the distance x from a lens center, and the position of a beam.

As can be seen from FIG. 3, since the ion beam 33 is more affected by the electric field by the electrostatic lens 51 as the valence is larger, the focal position with respect to the lens 51 becomes shorter in the order of C ^{1+ to} C ^6+. . Therefore, for example, if the aperture 52 is installed at a C ⁶⁺ focal position (for example, x = 95 mm), the C ⁶⁺ ion beam passes through the aperture 52 almost unobstructed, and other ion beams pass through the aperture 52. At 52, the majority will be blocked.

  As described above, according to the present embodiment, by providing the electrostatic lens 51 and the aperture 52 in the ion source transport system 200, the ion beam having an unnecessary valence is reduced, and only the ion beam 33a having a necessary valence is supplied. Can be selectively extracted. For this reason, unnecessary ion inflow to the downstream linear accelerator 300 side can be reduced, and contamination of the linear accelerator 300 can be reduced. Since the laser ion source emits multivalent ions, such valence selection is particularly effective.

  Since the unnecessary ion beam is blocked by the aperture 52 without being transported to the downstream side, there is a concern that the contamination on the ion source side may increase. However, maintenance of the ion source is much easier than maintenance of the linear accelerator 300, and contamination of the ion source can be easily removed. Further, in the laser ion source, it is necessary to periodically replace the target 21. At this time, maintenance for removing contamination may be performed.

(Second Embodiment)
FIG. 4 is a cross-sectional view showing the configuration of an ion source transport system for explaining a laser ion source according to the second embodiment of the present invention. In FIG. 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and description of the structure of those parts is omitted.

  The basic configuration of the second embodiment is the same as that of the first embodiment, and this embodiment is different from the first embodiment in that the aperture 52 in the ion source transport system 200 is placed in a vacuum. The stage 53 to be driven is provided. The stage 53 has a drive mechanism (not shown), and can move in the cylindrical body 41 in the beam axis direction with one end of the aperture 52 fixed. In addition, a signal cable is connected to the stage 53 via a vacuum introduction terminal, so that the stage 53 can be controlled outside the vacuum.

  Thus, in the present embodiment, the aperture 52 attached to the stage 53 can be moved in the ion beam axis direction. Therefore, if the aperture 52 is moved to the focal position P1 of the ion beam 33a having the valence Z1, the ion beam 33a having the valence Z1 can be selectively transported. Further, if the aperture 52 is moved to the focal position P2 of the ion beam 33b having the valence Z2, the ion beam 33b having the valence Z2 can be selectively transported. In other words, when an ion beam having a different valence is to be extracted from the multivalent ion beam, the ion beam having a necessary valence is selected without breaking the vacuum, and unnecessary ion flow into the downstream linear accelerator 300 side. To reduce contamination.

  Therefore, it is possible to easily select the valence of the ion beam as well as to obtain the same effect as that of the first embodiment.

  In addition, as a drive mechanism of the aperture 52, a linear introduction machine may be used, or a rotation introduction machine and a gear may be combined to form a movement mechanism in the ion beam axis direction. Furthermore, by making the stage 53 a three-axis stage, it is possible to have a function of remotely aligning the aperture 52 with the ion beam axis.

  Further, a mechanism such as a shutter stop may be provided in the aperture 52 so that the aperture diameter of the aperture 52 can be varied. In this case, since the aperture diameter can be set in accordance with the beam diameter at the convergence position of the ion beam to be selected, the selection control with higher accuracy is possible.

(Third embodiment)
FIG. 5 is a plan view for explaining a laser ion source according to the third embodiment of the present invention, and shows a configuration of an aperture provided in the ion source transport system.

  The basic configuration is the same as that of the first embodiment, and this embodiment is different from the first embodiment in that an aperture for allowing an ion beam to pass through the aperture 52 in the ion source transport system 200. Apart from 52a, an exhaust opening 52b for securing conductance for vacuum exhaust is provided.

  The aperture 52 is provided with a small-diameter opening 52a for allowing the ion beam to pass through at the center and an exhaust opening 52b at the periphery. A plurality of exhaust openings 52b are provided outside the multivalent ion beam maximum diameter 52c in the ion beam transport system 200 after passing through the electrostatic lens 51.

  In the laser ion source, as shown in FIG. 1, if the opening 52a of the aperture 52 is small in order to exhaust from the exhaust port 13 provided on the upper surface of the container 10, the downstream side of the aperture 52 is sufficiently exhausted. There are cases where it is not possible. On the other hand, by providing the aperture 52 with a relatively large diameter in addition to the opening 52 a as in the present embodiment, it is possible to suppress a decrease in vacuum conductance downstream of the aperture 52. Therefore, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and there is an advantage that a decrease in conductance due to the provision of the aperture 52 can be suppressed.

  As another method of providing the exhaust opening in the aperture 52, the diameter of the aperture 52 may be made smaller than the size of the vacuum duct of the ion beam transport system 200. Further, as shown in FIG. 6A, a notch 52 d may be provided outside the aperture 52. Further, as shown in FIG. 6B, a configuration in which an aperture 521 having a small diameter and a plate 522 having a diameter larger than the aperture 521 provided with an opening smaller than the aperture 521 at the center may be combined.

(Fourth embodiment)
FIG. 7 is a sectional view showing a schematic configuration of a laser ion source according to the fourth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and the detailed description is abbreviate | omitted. Further, the configuration other than the main part is shown in a simplified manner.

  This embodiment is different from the first embodiment in that an electromagnetic lens 55 is used instead of the electrostatic lens 51 as an ion beam selection mechanism. That is, an electromagnetic lens 55 for converging a multivalent ion beam by electromagnetic force is provided on the container 10 side of the cylinder 41 of the ion source transport system 200, and an aperture 52 is provided on the linear accelerator 300 side.

  Even in such a configuration, as in the first embodiment, since the convergence position of the ion beam by the electromagnetic lens 55 differs depending on the valence, the aperture 52 is set at the convergence position of the ion beam having the necessary valence. As a result, only the ion beam having the required valence can be extracted. Therefore, the same effect as the first embodiment can be obtained.

  Moreover, this embodiment can also combine the structure of 2nd-3rd embodiment similarly to 1st Embodiment.

(Fifth embodiment)
FIG. 8 is a sectional view showing a schematic configuration of a laser ion source according to the fifth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and the detailed description is abbreviate | omitted. Further, the configuration other than the main part is shown in a simplified manner.

  This embodiment is different from the first embodiment in that a deflector and an aperture are used as an ion beam selection mechanism. That is, a deflecting electromagnet 61 for deflecting a multivalent ion beam is provided on the container 10 side of the ion source transport system 200, and an aperture 62 is provided on the linear accelerator 300 side. The deflection electromagnet 61 deflects the ion beam by electromagnetic force, and is provided outside the cylindrical body 41. The aperture 62 has an opening at the center, and has a larger diameter than the opening of the aperture 51 used in the first embodiment.

  In the present embodiment configured as described above, the multivalent ion beam 33 drawn from the ion source main body 100 is deflected by the deflecting electromagnet 61. Since the deflection radius differs depending on the valence, the necessary valence is required. By installing the aperture 62 on the orbit of the Z1 ion beam 33a, it is possible to selectively transport the ion beam 33a having the valence Z1. Moreover, since neutral particles go straight regardless of the magnetic field strength, neutral particles can be eliminated at the same time. Furthermore, when it is desired to extract ion beams having different valences from the multivalent ion beam, ions having a valence that can pass through the aperture 62 can be selected by changing the magnetic field strength of the deflection electromagnet 12. Further, ions can be selected by providing the aperture 62 with the moving mechanism described in the second embodiment.

  FIG. 9 shows ion beams of various valences and how they are deflected. (A) is a figure which shows the positional relationship of the deflection electromagnet 61, the aperture 62, and an ion beam, (b) is a figure which shows the relationship between the distance x from the center of the deflection electromagnet 61, and the deflection position of a beam.

As can be seen from FIG. 9, the ion beam 33 is greatly deflected in the order of C ^{1+ to} C ⁶⁺ because the ion beam 33 is more affected by the magnetic field by the deflecting electromagnet 61 as the valence is larger. Therefore, for example, if the aperture of the aperture 62 is positioned at the C ⁶⁺ deflection position, the C ⁶⁺ ion beam passes without being blocked by the aperture 62, and other ion beams are blocked by the aperture 62. Will be.

  As described above, according to the present embodiment, by providing the deflecting electromagnet 61 and the aperture 62 in the ion source transport system 200, the ion beam having an unnecessary valence is reduced, and only the ion beam 33a having the necessary valence Z1 is provided. Can be selectively extracted. Therefore, the same effect as the first embodiment can be obtained.

  Further, when it is desired to focus the ion beam, or when it is desired to enhance the effect of ion selection, a configuration is adopted in which the deflecting electromagnet 61 is arranged in combination with the configuration described in the first to third embodiments in the ion source transport system 200. It is also possible.

(Sixth embodiment)
FIG. 10 is a sectional view showing a schematic configuration of a laser ion source according to the sixth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same part as FIG. Further, the configuration other than the main part is shown in a simplified manner.

  This embodiment is different from the fifth embodiment in that a deflection electrode 65 is used instead of the deflection electromagnet 61 as an ion beam selection mechanism. That is, a deflection electrode 65 for deflecting a multivalent ion beam by electrostatic force is provided on the container 10 side of the cylindrical body 41 of the ion source transport system 200, and an aperture 62 is provided on the linear accelerator 300 side.

  Even in such a configuration, as in the fifth embodiment, the deflection position of the ion beam by the deflection electrode 65 differs depending on the valence, and thus the aperture 62 is set at the deflection position of the ion beam having the required valence. As a result, only the ion beam having the required valence can be extracted. Therefore, the same effect as the fifth embodiment can be obtained.

(Seventh embodiment)
FIG. 11 is a sectional view showing a schematic configuration of a laser ion source according to the seventh embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and the detailed description is abbreviate | omitted. Further, the configuration other than the main part is shown in a simplified manner.

  This embodiment is different from the first embodiment in that a deflector and an aperture capable of high-speed deflection are used as an ion beam selection mechanism. That is, a pulse electrode 71 for pulsing the multivalent ion beam 33 in a pulse manner is provided in the cylinder 41 of the ion source transport system 200 on the container 10 side, and an aperture 72 is provided on the linear accelerator 300 side. Since the aperture 72 serves as a beam dump, the downstream wall of the ion source transport system 200 can be substituted.

  In the present embodiment configured as described above, the multivalent ion beam 33 extracted from the ion source main body 100 is deflected by applying a deflection voltage to the pulse electrode 71 and blocked by the aperture 72. The multivalent ion beam 33 has a time structure, and the higher the valence, the faster the speed. Accordingly, by driving the pulse electrode 71 in accordance with the passage time of the ion beam, the valence of the ion beam blocked by the aperture 72 can be selected. Specifically, if a pulse voltage is applied to the pulse electrode 71 while avoiding the passage time of the ion beam 33a having the necessary valence Z1, unnecessary ion beams having other valences are separated from the axis of the ion source transport system 200a. It is removed and collides with the downstream aperture 72 to be eliminated. As a result, only the ion beam 33a having the valence Z1 can be extracted.

  On the contrary, it is also possible to extract only the ion beam 33a having the valence Z1 by applying the pulse voltage only during the time when the ion beam 33a having the valence Z1 passes. In this case, the deflection direction by the deflection electrode 71 may be configured to coincide with the axis of the ion transport system 200 to the linear accelerator 300.

  FIG. 12 shows ion beams having various valences and how they are deflected. (A) shows the time distribution of ions, (b) shows the pulse electric field, and (c) shows the deflection state of the ion beam.

As can be seen from FIG. 12, the ion beam 33 has a higher speed as the valence is larger, and the time required to reach the position of the aperture 72 varies depending on the valence. Therefore, if the pulse voltage is not applied only during the time when the ion beam 33a having the required valence C ⁶⁺ passes through the aperture 72 and the pulse voltage is applied at other times, the ion beam of C ⁶⁺ can be applied to the aperture 72. The ion beam passes without being blocked by the aperture 72, and the other ion beams are blocked by the aperture 72.

  As described above, according to the present embodiment, by providing the pulse electrode 71 and the aperture 72 in the ion source transport system 200, the ion beam having an unnecessary valence is reduced, and only the ion beam 4a having the necessary valence Z1 is provided. Can be selectively extracted. Therefore, the same effect as the first embodiment can be obtained.

  Further, when it is desired to focus the ion beam or when it is desired to enhance the effect of ion selection, it is possible to adopt a configuration combined with the configurations of the first to fourth embodiments.

(Eighth embodiment)
FIG. 13 is a sectional view showing a schematic configuration of a laser ion source according to the eighth embodiment of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 11 and an identical part, and the detailed description is abbreviate | omitted. Further, the configuration other than the main part is shown in a simplified manner.

  This embodiment differs from the seventh embodiment in that a pulse electromagnet 75 is used instead of the pulse electrode 71 as a deflector capable of high-speed deflection as an ion beam selection mechanism. That is, a pulse electromagnet 75 that deflects the multivalent ion beam 33 in a pulse manner is provided on the container 10 side in the cylindrical body 41 of the ion source transport system 200, and an aperture 72 is provided on the linear accelerator 300 side. Since the aperture 72 serves as a beam dump, the downstream wall of the ion source transport system 200 can be substituted.

  Even in such a configuration, an unnecessary valence ion beam can be eliminated by applying a pulse voltage when an unnecessary valence ion beam passes through the pulse electromagnet 75 as in the seventh embodiment. Only the ion beam having the required valence can be taken out. Therefore, the same effect as in the seventh embodiment can be obtained.

  Further, when it is desired to focus the ion beam or when it is desired to enhance the effect of ion selection, it is possible to adopt a configuration combined with the configurations of the first to fourth embodiments.

(Modification)
In addition, this invention is not limited to each embodiment mentioned above, Each embodiment can also be combined. Further, the structure, material, and the like of each part are not limited to the embodiment, and can be appropriately changed according to specifications.

In the embodiment, the extraction electrode is provided to extract the ion beam from the irradiation box. However, the wall surface of the container can be used as the extraction electrode. The wall surface of the irradiation box does not necessarily have a plate shape, and may have a mesh shape. The target is not necessarily limited to carbon, but may be any element that becomes a polyvalent ion or contains it. Further, the laser light source is not limited to the Co ₂ laser or the YAG laser, and any laser light source capable of performing high-energy short pulse irradiation (several J / pulse) may be used.

  In the embodiment, the ion used is carbon as a heavy particle. However, in some cases, helium (He), nitrogen (N), oxygen (O), neon (Ne), silicon (Si), argon ( It is also possible to use Ar).

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Vacuum container 12 ... Extraction electrode 20 ... Irradiation box 21 ... Target 31 ... Laser beam 41 ... Cylindrical body 42 ... Flange 43 ... Valve 51 ... Electrostatic lens 52, 62, 72 ... Aperture 55 ... Electromagnetic lens 61 ... Deflection magnet 65 ... Deflection electrode 71 ... Pulse electrode 75 ... Pulse electromagnet 100 ... Ion source body 200 ... Ion source transport system 300 ... Linear accelerator (RFQ)

Claims (10)

A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
An electrostatic lens that converges the ion beam extracted from the irradiation box by an electrostatic force;
An aperture provided at a position on the downstream side of the electrostatic lens, and allowing an ion beam focused at the position to pass through;
A laser ion source comprising: A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
An electromagnetic lens for converging the ion beam drawn from the ion source by electromagnetic force;
An aperture provided at a position on the downstream side of the electromagnetic lens, for passing an ion beam converged at the position;
A laser ion source comprising:   3. The laser ion source according to claim 1, wherein the aperture is provided so as to be movable in a traveling direction of the ion beam.   4. The laser ion source according to claim 3, wherein the aperture is provided so that a diameter of an opening for allowing a part of the ion beam to pass therethrough is variable.   3. The laser ion according to claim 1, wherein an exhaust opening is provided outside the maximum diameter of the ion beam, in addition to the opening for allowing a part of the ion beam to pass through the aperture. source. A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
A deflecting electromagnet that deflects the ion beam extracted from the irradiation box with electromagnetic force;
An aperture that is provided downstream of the deflection electromagnet and allows an ion beam deflected by a predetermined amount by the deflection electromagnet to pass through;
A laser ion source comprising: A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
A deflection electrode that electrostatically deflects the ion beam drawn from the irradiation box;
An aperture that is provided on the downstream side of the deflection electrode and passes an ion beam deflected by a predetermined amount by the deflection electrode;
A laser ion source comprising: A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
A pulse electrode capable of deflecting an ion beam extracted from the irradiation box at an interval shorter than a time distribution width of the ion beam;
An aperture that is provided downstream of the pulse electrode and blocks an ion beam deflected by the pulse electrode;
A laser ion source comprising: A container to be evacuated;
An irradiation box disposed in the container and containing a target that generates multivalent ions by irradiation with laser light; and
Ion beam extraction means for electrostatically extracting ions from the irradiation box and guiding the ions to the outside of the container;
A pulse electromagnet capable of deflecting the ion beam extracted from the irradiation box at intervals shorter than the time distribution width of the ion beam;
An aperture that is provided downstream of the pulse electromagnet and blocks the ion beam deflected by the pulse electromagnet;
A laser ion source comprising: Laser ion source comprising a pulse deflector capable of deflecting an ion beam extracted from the ion source body at intervals shorter than the time distribution width of the ion beam, and an aperture provided downstream of the pulse deflector Driving method,
At the timing when an ion beam having a required valence passes through an installation region of the pulse deflector, a deflection signal is not applied to the deflector, and the ion beam having a required valence is allowed to pass through the aperture without being deflected.
By applying a deflection signal to the deflector at a timing when an ion beam having an unnecessary valence passes through an installation region of the pulse deflector, the ion beam having an unnecessary valence is deflected and blocked by the aperture.
A method of driving a laser ion source.

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