Charged particle beam transport apparatus, method for manufacturing a charged particle beam transport apparatus, and method for neutralizing a charged particle beam

Abstract

To provide a charged particle beam transport device, a manufacturing method of a charged particle beam transport device, and a neutralization method of charged particle beams, which are capable of achieving both a reduction in beam divergence due to space charge and a reduction in loss due to beam neutralization.SOLUTION: A charged particle beam transport device 20 includes: collimators 13a, 13b each having an inner diameter that becomes smaller toward a convergence part of charged particle beams 1; and inlets 9b1, 9b2, 9b3, 9b4 through which a space charge neutralizer neutralizing space charge is injected toward a space surrounded by the collimators 13a, 13b.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a charged particle beam transport device, a method for manufacturing a charged particle beam transport device, and a method for neutralizing a charged particle beam.

Background Art

[0002] A technique for reducing beam divergence due to the space charge effect of a charged particle beam is described in Patent Document 1. This Patent Document 1 describes "an electron beam device characterized by irradiating an ion beam into the orbit region of an electron beam to neutralize the space charge formed by the electron beam and reduce the space charge effect." and "The ion generation means is characterized by changing the ion beam density according to the magnitude of the current density of the electron beam along the orbit of the electron beam."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 describes a device aimed at efficiently reducing the space charge effect by adjusting the irradiation position of an ion beam according to the magnitude of the current density of an electron beam.

[0005] However, in the device described in Patent Document 1, only the irradiation position is adjusted, and since the irradiated neutralizing agent spreads spatially, there is a problem that the concentration of ions, which are the neutralizing agent, in the beam convergence part with a high current density cannot be made sufficiently high. This effect is particularly remarkable when a neutral gas is used as the neutralizing agent. In addition, the device described in Patent Document 1 has a problem that space charge neutralization according to the space charge distribution caused by the variation in the current density in the beam diameter direction cannot be achieved.

[0006] Due to the factors described above, in regions with high space charge, the degree of neutralization of the space charge is insufficient, causing the beam to diverge and leading to beam loss. On the other hand, in regions with low space charge, beam neutralization due to the reaction between the beam and the neutralizing agent becomes excessive, similarly leading to beam loss.

[0007] The present invention provides a charged particle beam transport device capable of simultaneously reducing beam divergence due to space charge and reducing losses through beam neutralization, a method for manufacturing a charged particle beam transport device, and a method for neutralizing a charged particle beam. [Means for solving the problem]

[0008] The present invention includes multiple means for solving the above problems, but one example is a charged particle beam transport device, wherein the focusing section of the charged particle beam The charged particle beam transport device is provided on the inlet side of the charged particle beam, and the inlet The inner diameter decreases towards the end. In addition, it is provided on the outlet side of the charged particle beam in the charged particle beam transport device, and the inner diameter decreases toward the outlet. The system comprises a convergent structure, an inlet for injecting a space charge neutralizing agent into the space enclosed by the convergent structure, and a control device for controlling the amount of space charge neutralizing agent injected. [Effects of the Invention]

[0009] According to the present invention, it is possible to achieve both a reduction in beam divergence due to space charge and a reduction in losses due to beam neutralization. Other problems, configurations, and effects will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the configuration of a linear accelerator including a charged particle beam transport device according to the first embodiment. [Figure 2] This figure shows the flow of controlling the injection amount of the space charge neutralizing agent according to the first embodiment. [Figure 3] This is a schematic diagram showing the arrangement of the space charge neutralizer injection port and beam distribution meter in the charged particle beam transport apparatus according to the second embodiment. [Figure 4] This is a schematic diagram showing a modified example of a charged particle beam transport apparatus according to the second embodiment. [Figure 5] This is a schematic diagram showing a modified example of a charged particle beam transport apparatus according to the second embodiment. [Figure 6] This is a schematic diagram showing an example of a collimator in a charged particle beam transport apparatus according to the third embodiment. [Figure 7] This is a schematic diagram showing a modified example of the collimator of the charged particle beam transport apparatus according to the third embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the charged particle beam transport apparatus, the method for manufacturing the charged particle beam transport apparatus, and the method for neutralizing a charged particle beam according to the present invention will be described below with reference to the drawings. In the drawings used herein, the same or corresponding components are denoted by the same or similar reference numerals, and repeated descriptions of these components may be omitted.

[0012] <First Embodiment> A first embodiment of the charged particle beam transport apparatus, a method for manufacturing the charged particle beam transport apparatus, and a method for neutralizing a charged particle beam of the present invention will be described with reference to Figures 1 and 2.

[0013] First, the overall configuration of the linear accelerator 30, including the charged particle beam transport device, will be explained using Figure 1. Figure 1 is a schematic diagram of the configuration of the linear accelerator, including the charged particle beam transport device, according to the first embodiment.

[0014] The charged particle beam transport device 20 shown in Figure 1 is a device for injecting the charged particle beam 1 generated by the charged particle beam generator 4, which consists of an ion source and the like, into the downstream accelerator 5. It consists of a vacuum chamber 2, focusing coils 3a and 3b, a neutralizing agent reservoir 7, an injection amount control device 8, injection ports 9a and 9b, a vacuum gauge 10, a beam distribution meter 11, a beam current meter 12, collimators 13a and 13b, and a vacuum pump 14.

[0015] When manufacturing such a charged particle beam transport device 20, at least the steps of providing collimators 13a and 13b whose inner diameters decrease toward the converging portion of the charged particle beam 1, and the steps of providing inlets 9a and 9b for injecting a space charge neutralizing agent for neutralizing the space charge toward the space surrounded by the collimators 13a and 13b are performed.

[0016] Here, the charged particle beam generation device 4 is a device that generates the charged particle beam 1, and its types include, for example, a microwave ion source, an ECR (Electron Cyclotron Resonance) ion source, a duoplasmatron, an electron gun, etc., and it can be any of these devices. In this embodiment, the configuration of a linear accelerator employing a microwave ion source will be described as an example.

[0017] The plasma generated by microwaves in the charged particle beam generation device 4 is extracted by the potential difference with the extraction electrode 6, and the charged particle beam 1 is generated.

[0018] The charged particle beam 1 is converged by the converging coils 3a and 3b in the vacuum chamber 2 and is incident on the subsequent accelerator 5. Here, the converging coils 3a and 3b can be provided with magnetic poles using a magnetic material.

[0019] The subsequent accelerator 5 is, for example, a high-frequency accelerator, etc., including an RFQ (Radio Frequency Quadrupole), a DTL (Drift Tube Linac), etc., and either one or both of them can be used. Alternatively, it can also be an electrostatic accelerator such as a Cockcroft-Walton type or a Van de Graaff type.

[0020] The charged particle beam 1, injected into the vacuum chamber 2 from the charged particle beam generator 4, is focused by the focusing coils 3a and 3b to adjust its shape so that it can be injected into the downstream accelerator 5. At this time, divergence occurs due to Coulomb repulsion between the charged particles constituting the charged particle beam 1, i.e., the space charge effect. Therefore, as the beam current value increases, a divergence force is generated that exceeds the focusing force of the focusing coils 3a and 3b.

[0021] One method for neutralizing space charge is to inject neutral gas or plasma into the region through which the charged particle beam 1 passes. When neutral gas is injected, the charged particle beam 1 collides with the neutral gas, causing it to ionize and emit electrons. If the charged particle beam 1 has a positive charge, the electrons emitted by ionization are attracted to the beam trajectory by the Coulomb force between them. On the other hand, the ionized gas is pulled away from the beam trajectory by the repulsion caused by the Coulomb force between it and the charged particle beam 1. Through the above action, ions with the opposite charge to the charged particle beam 1 accumulate in the trajectory, neutralizing the space charge. Space charge is neutralized by a similar action when plasma is injected. In this embodiment, an example using neutral gas as the neutralizing agent is explained, but the details are the same when plasma is injected as when neutral gas is introduced, so the explanation is omitted.

[0022] If there is insufficient neutralizing agent, the charged particle beam 1 will diverge due to insufficient neutralization of space charges. On the other hand, if there is an excess of space charge neutralizing agent, the charged particles in the charged particle beam 1 will combine with ions of the opposite sign, leading to increased loss of the charged particle beam 1 due to beam neutralization. Therefore, the charged particle beam transport device needs to suppress beam divergence due to space charge effects to a level acceptable under the injection conditions of the downstream accelerator 5, while minimizing the loss rate of the charged particle beam 1.

[0023] Therefore, in the charged particle beam transport device 20 of this embodiment, the concentration of the neutralizing agent in the focusing section, where the space charge is higher than in other sections, is increased. Here, "focusing section" refers to the "connection section between the charged particle beam generator 4 and the charged particle beam transport device 20," which is the inlet side of the charged particle beam 1 into the charged particle beam transport device 20, and / or the "connection section between the charged particle beam transport device 20 and the downstream accelerator 5," which is the outlet side.

[0024] In this first embodiment, the amount of neutral gas stored in the neutralizing agent reservoir 7 is adjusted by an injection amount control device 8 that controls the amount of neutral gas injected as a space charge neutralizer, and the neutralizing of space charge is performed particularly at the inlet and / or outlet sides of the charged particle beam 1 where the space charge is high.

[0025] Furthermore, in this embodiment, in order to generate a neutralizing agent distribution corresponding to the distribution of space charge generated by the divergent and convergent trajectories of the charged particle beam 1, tapered collimators 13a and 13b are provided that are matched to the divergent and convergent trajectories.

[0026] Collimators 13a and 13b are structures whose inner diameter decreases towards the convergence point of the charged particle beam 1. Collimator 13b is located on the exit side of the charged particle beam 1 and has an inner diameter that decreases towards the exit. In contrast, collimator 13a is located on the inlet side of the charged particle beam 1 and has an inner diameter that decreases towards the inlet.

[0027] Injection port 9a is an opening for injecting a space charge neutralizing agent toward the space surrounded by collimator 13a, and injection port 9b is an opening for injecting a space charge neutralizing agent toward the space surrounded by collimator 13b. The concentration of the neutralizing agent can be increased as the inner diameter of collimators 13a and 13b decreases. This makes it possible to increase the space charge neutralization rate in the region where the charged particle beam 1 converges and the space charge becomes high.

[0028] The injection volume of the neutralizing agent and the shapes of collimators 13a and 13b are determined in advance based on beam simulations and gas distribution simulations. In the beam simulations, beam trajectory calculations that consider space charge effects, such as the PIC (Particle In Cell) method, are used. In the gas distribution simulations, the mean free path of the neutral gas used as the neutralizing agent is assumed to be sufficiently long, and the gas distribution is calculated using a simulator that calculates it as molecular flow.

[0029] Note that the lengths of collimators 13a and 13b in the transport direction depend on the beam's design trajectory, and as shown in Figure 1, the collimator 13b on the exit side is not necessarily longer than the collimator 13a on the inlet side.

[0030] As mentioned earlier, the charged particle beam transport device 20 needs to suppress beam divergence due to space charge effects so that the shape of the charged particle beam 1 falls within the allowable limits of the downstream accelerator 5.

[0031] Therefore, based on beam simulations, the amount of space charge at each spatial position on the trajectory of charged particle beam 1 is evaluated, and the required space charge neutralization rate at each spatial position is determined. In addition, by using gas distribution simulations to evaluate the neutral gas distribution with respect to the shapes of collimators 13a and 13b, collimators 13a and 13b are determined so that the neutral gas distribution approaches the space charge distribution evaluated in the beam simulations described above.

[0032] Furthermore, the beam distribution under conditions where the required space charge neutralization rate is achieved is calculated in advance using beam simulation, and the amount of neutral gas injected is determined so that the measured beam distribution measured by the beam distribution analyzer 11 approaches the calculated value.

[0033] More specifically, the injection amount control device 8 can adjust the injection amount of the space charge neutralizer based on the measurement results from the beam distribution meter 11, which measures the distribution of the charged particle beam 1. When it is determined that the beam distribution in the cross-section in the transport direction is narrower than a first predetermined range, the injection amount of the space charge neutralizer is reduced compared to the determination timing. When it is determined that the beam distribution is wider than a second predetermined range, which is wider than the first predetermined range, the injection amount of the space charge neutralizer is increased compared to the determination timing.

[0034] The beam distribution analyzer 11 may be either a non-contact measuring instrument that measures the potential of electrodes excited by electromagnetic waves or charged particle beam 1 generated in the beam trajectory, or a contact-type measuring instrument such as a Faraday cup or wire chamber.

[0035] In actual operation, however, the amount of neutralizing agent required to be injected is very likely to change due to the time variation of the current of the charged particle beam 1 and the change in the pumping speed of the vacuum pump 14 installed in the vacuum chamber 2.

[0036] Therefore, the injection volume control device 8 can adjust the flow rate of the space charge neutralizer based on the measurement results of the beam current value (increase or decrease in total current) measured by the beam current meter 12, in addition to the measurement results of the beam distribution meter 11. Furthermore, the flow rate of the space charge neutralizer can be adjusted based on the measurement results of the vacuum level (change in the concentration of the neutralizer due to a change in the vacuum pumping speed) measured by the vacuum meter 10, which measures the vacuum level inside the charged particle beam transport device 20.

[0037] For example, the amount of space charge neutralizer injected can be adjusted so as to reduce the amount of space charge neutralizer injected when it is determined that the beam current value is less than a first predetermined value or greater than a second predetermined value greater than the first predetermined value, and further, when it is determined that the vacuum level is lower than a third predetermined value or higher than a fourth predetermined value.

[0038] The beam current meter 12 can be a non-contact type CT (Current Transformer), etc. The vacuum gauge 10 can be configured in various known configurations.

[0039] Even when adjusting the injection amount of the neutralizing agent based on the measurement results of the beam current meter 12 and the vacuum meter 10, it is desirable to adjust the injection amount so that the beam distribution measured by the beam distribution meter 11 ultimately matches the target distribution (see Figure 2).

[0040] Furthermore, it is desirable that the vacuum pump 14, which evacuates the charged particle beam transport device 20, be installed in the intermediate portion between the inlet collimator 13a and the outlet collimator 13a, i.e., in an equidistant portion or around it, and at a distance from the injection ports 9a and 9b.

[0041] Next, the neutralization method for the charged particle beam 1 according to this embodiment will be described with reference to Figure 2. Figure 2 is a flowchart for controlling the injection amount of the neutralizing agent in this embodiment.

[0042] First, the injection volume control device 8 calculates the amount of neutralizing agent to be injected based on the vacuum level measured by the vacuum gauge 10 and the beam current measured by the beam current meter 12, as described above (step S101).

[0043] Next, the injection volume control device 8 determines whether the beam current and vacuum level acquired in step S101 are within a preset tolerance range (step S102).

[0044] If it is determined in step S102 that the result is outside the acceptable range, the process proceeds to step S103, where the injection amount control device 8 adjusts the injection amount of the neutralizing agent to a preset amount for the beam current and vacuum level (step S103). After that, the process returns to step S101 to confirm the effect of the injection.

[0045] In contrast, if it is determined in step S102 that the amount is within an acceptable range, the injection volume control device 8 waits for a certain period of time until the distribution of the injected neutralizing agent in the vacuum chamber 2 stabilizes (step S104).

[0046] Next, the beam distribution is measured using the beam distribution meter 11 (step S105).

[0047] Subsequently, the injection volume control device 8 determines whether the difference between the beam distribution measured in step S105 and the target beam distribution is within an acceptable range (step S106).

[0048] If it is determined in step S106 that the result is outside the acceptable range, the process proceeds to step S107. The injection amount control device 8 compares the measured beam distribution with the target distribution and controls the injection amount to a preset level, increasing it if the beam divergence is large, and decreasing it to account for beam loss if the beam divergence is small (step S107). After that, the process returns to step S105 to confirm the effect of the injection.

[0049] If it is determined in step S106 that the amount of neutralizing agent injected is within an acceptable range, the control of the neutralizing agent injection amount is terminated.

[0050] In addition, since it is desirable to at least adjust the beam distribution in each step in Figure 2, steps S101 to S104 may be omitted and only steps S105 to S107 may be executed. However, it is desirable to execute all of them as shown in Figure 2.

[0051] The flow shown in Figure 2 should preferably be performed at predetermined intervals during the generation of the charged particle beam 1.

[0052] Next, the effects of this embodiment will be described.

[0053] The charged particle beam transport apparatus 20 of the first embodiment of the present invention described above includes collimators 13a and 13b whose inner diameter decreases toward the convergence portion of the charged particle beam 1, and injection ports 9a and 9b for injecting a space charge neutralizing agent toward the space surrounded by the collimators 13a and 13b, thereby increasing the concentration of the neutralizing agent in the convergence portion.

[0054] This allows the amount of space charge neutralizer injected to reduce excess or deficiency of space charge neutralization in accordance with the space charge distribution in the beam trajectory direction associated with the divergence and convergence trajectories of the charged particle beam, and the space charge distribution in the circumferential direction relative to the beam trajectory associated with the charge distribution of the charged particle beam. As a result, losses due to divergence and beam neutralization of the charged particle beam can be reduced compared to conventional methods.

[0055] Such a charged particle beam transport device 20 is preferably suitable for linear accelerators and can be applied to ion sources in fusion power reactors, Boron Neutron Capture Therapy (BNCT), or particle beam therapy devices using synchroton accelerators.

[0056] Furthermore, the collimator 13b is located on the exit side of the charged particle beam 1, and its inner diameter decreases towards the exit. This allows for a more effective increase in the neutralization rate of the portion of the charged particle beam 1 that is focused toward the subsequent accelerator 5.

[0057] Furthermore, the collimator 13a is also provided on the inlet side of the charged particle beam 1, and its inner diameter decreases towards the inlet, thereby further increasing the neutralization rate of the focused portion of the charged particle beam 1 drawn out from the charged particle beam generator 4 on the inlet side.

[0058] Furthermore, because collimators 13a and 13b have a tapered shape, the introduced space charge neutralizer is introduced more smoothly along the tapered surface, towards the outlet and inlet sides where the convergence is tighter, thereby achieving more effective neutralization.

[0059] Furthermore, the system includes a beam distribution meter 11 for measuring the distribution of the charged particle beam 1, and an injection amount control device 8 for controlling the amount of space charge neutralizer injected. The injection amount control device 8 adjusts the amount of space charge neutralizer injected so that the beam distribution in the cross-section in the transport direction takes on a desired shape. In particular, when it is determined that the beam distribution is narrower than a first predetermined range, the amount of space charge neutralizer injected is reduced from the determined timing, and when it is determined that the beam distribution is wider than a second predetermined range which is wider than the first predetermined range, the amount of space charge neutralizer injected is increased from the determined timing, thereby adjusting the charged particle beam 1 to a beam shape more suitable for the downstream accelerator 5.

[0060] Furthermore, by installing a vacuum pump 14 for evacuating the charged particle beam transport device 20 in the intermediate section between the inlet collimator 13a and the outlet collimator 13b, the space charge neutralizing agent being introduced can be evacuated early, reliably preventing deviations from the intended amount.

[0061] Furthermore, the system further includes a beam current meter 12 for measuring the current of the charged particle beam 1 and an injection amount control device 8 for controlling the injection amount of space charge neutralizer, wherein the injection amount control device 8 adjusts the flow rate of the space charge neutralizer based on the measurement result of the beam current value by the beam current meter 12, or further includes a vacuum meter 10 for measuring the vacuum level inside the charged particle beam transport device 20 and an injection amount control device 8 for controlling the injection amount of space charge neutralizer, wherein the injection amount control device 8 adjusts the flow rate of the space charge neutralizer based on the measurement result of the vacuum meter 10, thereby enabling the injection of a space charge neutralizer that is even more suitable for the state of the charged particle beam 1.

[0062] In this embodiment, we have shown a configuration in which the amount of space charge neutralizer injected is adjusted based on the results measured by the beam distribution meter 11, beam current meter 12, and vacuum meter 10. However, it is also possible to control the amount of injection without a measurement system, based on the results obtained in advance through simulation.

[0063] <Second Embodiment> A second embodiment of the present invention, a charged particle beam transport apparatus, a method for manufacturing the charged particle beam transport apparatus, and a method for neutralizing a charged particle beam, will be described with reference to Figures 3 to 5. Components identical to those in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted. The same applies to the following embodiments. Figures 3 to 5 are schematic diagrams showing the arrangement of the space charge neutralizer injection port and beam distribution meter in the charged particle beam transport apparatus according to the second embodiment.

[0064] In this embodiment shown in Figure 3, multiple injection ports 9b1, 9b2, 9b3, and 9b4 are provided, and the injection amount control device 8 independently controls the injection amount at each position of the multiple injection ports 9b1, 9b2, 9b3, and 9b4 arranged to the side of the beam, according to the spatial charge distribution in the plane perpendicular to the beam axis of the charged particle beam 1.

[0065] When actually transporting the charged particle beam 1, the beam current distribution may become biased depending on the state of the charged particle beam 1, which can result in an asymmetric space charge distribution in the plane perpendicular to the beam axis. Therefore, the injection amount control device 8A can perform space charge neutralization corresponding to the asymmetric space charge distribution by independently controlling the injection amount ratio according to the positions of injection ports 9b1, 9b2, 9b3, and 9b4.

[0066] Figure 3 illustrates an example in which four beam dispersers 11a, 11b, 11c, and 11d, and four neutralizing agent inlets 9b1, 9b2, 9b3, and 9b4 are arranged symmetrically at 90-degree intervals to the side of the charged particle beam 1.

[0067] In this case, the beam distribution meters 11a, 11b, 11c, and 11d, and the injection ports 9b1, 9b2, 9b3, and 9b4 do not necessarily need to be placed in the same plane. Each of the four beam distribution meters 11a, 11b, 11c, and 11d, and the injection ports 9b1, 9b2, 9b3, and 9b4 are connected to the injection amount control device 8A, which controls the injection amount to increase the injection amount ratio of the neutralizing agent from the injection ports 9b1, 9b2, 9b3, and 9b4 on the side with greater beam divergence, based on the beam distribution measured by the beam distribution meter 11.

[0068] For example, based on the beam divergence evaluated from the beam distribution measured by beam distribution meters 11a and 11c, the injection rate ratio is adjusted while maintaining the total injection amount at the vertical injection ports 9b2 and 9b4. Similarly, for other directions, the ratio of neutralizing agent injection from the direction with greater divergence is increased while maintaining the total injection amount.

[0069] In this embodiment, as shown in Figure 4, a single beam distribution meter 11a, 11d may be installed perpendicular to the line connecting the opposing inlets 9b1, 9b2, 9b3, 9b4, and the injection amount control device 8B may be used to adjust the injection amount of space charge neutralizer from inlets 9b1, 9b2, 9b3, 9b4. In other words, this embodiment can be established with half the number of beam distribution meters 11 compared to Figure 3. Furthermore, the number of opposing inlets 9b1, 9b2, 9b3, 9b4 and beam distribution meters 11a, 11d may be greater than those in Figures 3 and 4.

[0070] Alternatively, as shown in Figure 5, the beam distributors 11a1, 11b1, 11c1, and 11d1 may be configured as contact-type detectors, and the injection amount control device 8C may be used to adjust the injection amount of space charge neutralizer from injection ports 9b1, 9b2, 9b3, and 9b4. In the case of contact-type beam distributors 11a1, 11b1, 11c1, and 11d1, the extent to which the beam halo portion 15, which has diverged from the charged particle beam 1, extends is measured, and the injection amount ratio of the opposing beam distributors 11a1, 11b1, 11c1, and injection ports 9b1, 9b2, 9b3, and 9b4, which are in the same axial direction as the beam halo portion 15, is adjusted according to the divergence region of the beam halo portion 15.

[0071] Other configurations and operations are substantially the same as those of the charged particle beam transport apparatus, the method for manufacturing the charged particle beam transport apparatus, and the method for neutralizing the charged particle beam described in the first embodiment above, and details are omitted.

[0072] In the second embodiment of the present invention, the charged particle beam transport apparatus, the method for manufacturing the charged particle beam transport apparatus, and the method for neutralizing a charged particle beam also provide substantially the same effects as those of the first embodiment described above.

[0073] Furthermore, the injection volume control device 8A independently controls the injection volume ratio according to the positions of the injection ports 9b1, 9b2, 9b3, and 9b4, enabling the injection of a more appropriate space charge neutralizer to correct the beam bias even when bias occurs.

[0074] <Third Embodiment> A third embodiment of the present invention, a charged particle beam transport apparatus, a method for manufacturing the charged particle beam transport apparatus, and a method for neutralizing a charged particle beam, will be described with reference to Figures 6 and 7. Figures 6 and 7 are schematic diagrams showing an example of a collimator in the charged particle beam transport apparatus according to the third embodiment.

[0075] As shown in Figure 6, this embodiment uses a collimator 16 with a stepped structure whose diameter decreases to match the convergence trajectory of the charged particle beam 1, instead of the collimator 13b of Embodiment 1. By directing the injection port 9b towards the inside of such a collimator 16 and injecting the neutralizing agent, the concentration of the neutralizing agent in the convergence section of the charged particle beam 1, which has a high space charge, can be increased. The inlet side can also have a similar stepped structure, but the inlet and outlet sides do not need to have the same structure.

[0076] In Figure 7, as in Figure 6, by providing a collimator 17 with a smaller inner diameter to match the convergence trajectory of the charged particle beam 1, the concentration of the neutralizing agent in the convergence section of the charged particle beam 1, which has a high space charge, can be increased. In Figure 7, the inlet side can also be made into a stepped structure, and it does not have to be the same structure. However, a stepped structure with fine steps like in Figure 6 or a smooth tapered structure like in Figure 1 allows for a smoother change in the concentration distribution of the neutralizing agent, thus increasing the efficiency of space charge neutralization.

[0077] In this embodiment as well, the design of the structure and the amount of space charge neutralizing agent injected can be determined in the same way as in Embodiment 1. Similarly, the amount of neutralizing agent injected is controlled according to the control flow shown in Figure 2.

[0078] Other configurations and operations are substantially the same as those of the charged particle beam transport apparatus, the method for manufacturing the charged particle beam transport apparatus, and the method for neutralizing the charged particle beam described in the first embodiment above, and details are omitted.

[0079] In the third embodiment of the present invention, the charged particle beam transport apparatus, the method for manufacturing the charged particle beam transport apparatus, and the method for neutralizing a charged particle beam also provide substantially the same effects as those described above for the first embodiment of the present invention.

[0080] <Other> It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described.

[0081] Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0082] Embodiments of the present invention may also be in the following forms.

[0083] (1) A charged particle beam transport device comprising a focusing structure whose inner diameter decreases toward the focusing section of the charged particle beam, and an injection port for injecting a space charge neutralizer into the space enclosed by the focusing structure to neutralize space charge.

[0084] (2) In the charged particle beam transport apparatus described in (1), the focusing structure is provided on the outlet side of the charged particle beam in the charged particle beam transport apparatus, and its inner diameter decreases toward the outlet.

[0085] (3) In the charged particle beam transport apparatus described in (1) or (2), the focusing structure is further provided on the inlet side of the charged particle beam in the charged particle beam transport apparatus, and its inner diameter decreases toward the inlet.

[0086] (4) In the charged particle beam transport device described in any of (1) to (3), the focusing structure is tapered.

[0087] (5) A charged particle beam transport apparatus according to any one of (1) to (4) further comprises a distribution measuring instrument for measuring the distribution of the charged particle beam and a control device for controlling the amount of space charge neutralizer injected, wherein the control device adjusts the amount of space charge neutralizer injected so that the beam distribution in the cross-section in the transport direction takes on a desired shape.

[0088] (6) In the charged particle beam transport apparatus described in (5), the control device reduces the amount of space charge neutralizer injected from the determined timing when it is determined that the beam distribution is narrower than a first predetermined range, and increases the amount of space charge neutralizer injected from the determined timing when it is determined that the beam distribution is wider than a second predetermined range which is wider than the first predetermined range.

[0089] (7) In the charged particle beam transport apparatus described in any of (1) to (6), the focusing structure is provided on the inlet side and the outlet side of the charged particle beam, and a vacuum exhaust section for evacuating the inside of the charged particle beam transport apparatus is provided in an intermediate portion between the focusing structure on the inlet side and the focusing structure on the outlet side.

[0090] (8) A charged particle beam transport apparatus according to any one of (1) to (7) further comprises a current measuring instrument for measuring the current of the charged particle beam and a control device for controlling the amount of space charge neutralizer injected, wherein the control device adjusts the flow rate of the space charge neutralizer based on the measurement result of the beam current value by the current measuring instrument.

[0091] (9) The charged particle beam transport apparatus according to any one of (1) to (8) further comprises a vacuum level measuring instrument for measuring the vacuum level inside the charged particle beam transport apparatus and a control device for controlling the amount of space charge neutralizer injected, wherein the control device adjusts the flow rate of the space charge neutralizer based on the vacuum level measurement result by the vacuum level measuring instrument.

[0092] (10) The charged particle beam transport apparatus according to any one of (1) to (9) is further provided with a plurality of injection ports and a control device for independently controlling the amount of space charge neutralizer injected into each of the plurality of injection ports.

[0093] (11) A method for manufacturing a charged particle beam transport device, comprising the steps of: providing a focusing structure whose inner diameter decreases toward the focusing portion of the charged particle beam; and providing an injection port for injecting a space charge neutralizer into the space surrounded by the focusing structure to neutralize space charge.

[0094] (12) A method for neutralizing a charged particle beam, comprising providing a focusing structure whose inner diameter decreases toward the focusing portion of the charged particle beam, and injecting a space charge neutralizing agent into the space surrounded by the focusing structure to neutralize the space charge. [Explanation of symbols]

[0095] 1…Charged particle beam 2… Vacuum chamber 3a, 3b... Converging coils 4…Charged particle beam generator 5...Late stage accelerator 6...Drawer electrodes 7. Neutralizing agent storage container 8, 8A, 8B, 8C… Injection volume control devices 9a,9b,9b1,9b2,9b3,9b4...Inlet 10...Vacuum gauge (vacuum measuring device) 11, 11a, 11a1, 11b, 11b1, 11c, 11c1, 11d, 11d1... Beam distribution meter (distribution measuring instrument) 12…Beam ammeter (current measuring instrument) 13, 13a, 13b, 16, 17... Collimators (converging structures) 14… Vacuum exhaust pump (vacuum exhaust section) 15... Beam halo section 20... Charged particle beam transport device 30…Linear accelerator

Claims

1. A charged particle beam transport device, A focusing structure provided on the inlet side of the charged particle beam in the charged particle beam transport device, which is the focusing section of the charged particle beam, and whose inner diameter decreases toward the inlet, and also provided on the outlet side of the charged particle beam in the charged particle beam transport device, and whose inner diameter decreases toward the outlet, It comprises an inlet for injecting a space charge neutralizing agent into the space enclosed by the aforementioned convergence structure, which neutralizes space charges. Charged particle beam transport device.

2. In the charged particle beam transport apparatus according to claim 1, The aforementioned convergence structure has a tapered shape. Charged particle beam transport device.

3. In the charged particle beam transport apparatus according to claim 1, A distribution measuring instrument for measuring the distribution of the charged particle beam, The system includes a control device for controlling the amount of the space charge neutralizing agent injected, The control device adjusts the amount of space charge neutralizer injected so that the beam distribution in the cross-section in the transport direction takes on a desired shape. Charged particle beam transport device.

4. In the charged particle beam transport apparatus according to claim 3, The control device, when it is determined that the beam distribution is narrower than a first predetermined range, reduces the amount of space charge neutralizer injected from the determined timing, and when it is determined that the beam distribution is wider than a second predetermined range which is wider than the first predetermined range, increases the amount of space charge neutralizer injected from the determined timing. Charged particle beam transport device.

5. In the charged particle beam transport apparatus according to claim 1, A vacuum exhaust section for evacuating the inside of the charged particle beam transport apparatus is provided in the intermediate portion between the convergence structure on the inlet side and the convergence structure on the outlet side. Charged particle beam transport device.

6. In the charged particle beam transport apparatus according to claim 1, A current measuring instrument for measuring the current of the charged particle beam, The system includes a control device for controlling the amount of the space charge neutralizing agent injected, The control device adjusts the flow rate of the space charge neutralizer based on the measurement result of the beam current value by the current measuring instrument. Charged particle beam transport device.

7. In the charged particle beam transport apparatus according to claim 1, A vacuum level measuring instrument for measuring the vacuum level inside the charged particle beam transport device, The system includes a control device for controlling the amount of the space charge neutralizing agent injected, The control device adjusts the flow rate of the space charge neutralizer based on the vacuum level measurement result obtained by the vacuum level measuring instrument. Charged particle beam transport device.

8. In the charged particle beam transport apparatus according to claim 1, The facility has multiple inlets, The system further includes a control device that independently controls the amount of the space charge neutralizing agent injected into each of the multiple injection ports. Charged particle beam transport device.

9. A method for manufacturing a charged particle beam transport device, The step of providing a focusing structure in the charged particle beam transport device, which is the focusing section of the charged particle beam, which is provided on the inlet side of the charged particle beam and whose inner diameter decreases toward the inlet, and which is provided on the outlet side of the charged particle beam transport device and whose inner diameter decreases toward the outlet, The step includes providing an inlet for injecting a space charge neutralizing agent into the space enclosed by the aforementioned convergence structure. A method for manufacturing a charged particle beam transport device.

10. A neutralization method for neutralizing the space charge of a charged particle beam in a charged particle beam transport device, A space charge neutralizer is injected into a space surrounded by a converging structure, which is provided on the inlet side of the charged particle beam in the charged particle beam transport device, which is the converging section of the charged particle beam, and whose inner diameter decreases toward the inlet, and which is provided on the outlet side of the charged particle beam transport device, and whose inner diameter decreases toward the outlet. A method for neutralizing charged particle beams.

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