Charged particle beam transport device and charged particle beam neutralization method

Abstract

A charged particle beam transport device 20 comprises: one or more injection ports 8a, 8b, 8c for injecting a neutralizer for neutralizing a space charge, the injection ports 8a, 8b, 8c being arranged along a beam trajectory; flow rate regulators 9a, 9b, 9c for controlling the injection amount of the neutralizer from the injection ports 8a, 8b, 8c; and a control device 12. The injection amount is controlled on the basis of an evaluation of the space charge distribution and the beam loss rate. This makes it possible to provide a charged particle beam transport device and a charged particle beam neutralization method that achieve stable supply of a charged particle beam for a longer time than before.

Description

Charged particle beam transport device and method for neutralizing a charged particle beam

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

[0002] As an example of a technology for correcting the space charge effect with high uniformity within the plane of the electron trajectory, reducing electron beam loss due to collisions between electrons and ions, and efficiently neutralizing the space charge, thereby increasing the beam current and achieving high throughput, Patent Document 1 describes a technology that includes ion generating means that has a function of converging the electron beam emitted from an electron gun and is provided around the trajectory region of the electron beam, and ion irradiating means that irradiates the trajectory region of the electron beam with an ion beam generated from the ion generating means, and that neutralizes the space charge formed by the electron beam and reduces the space charge effect by irradiating the trajectory region of the electron beam with the ion beam.

[0003] Japanese Patent Application Laid-Open No. 2007-19195

[0004] When transporting a charged particle beam, the charged particles in the beam diverge due to Coulomb repulsion. This beam divergence is called the space charge effect. To suppress this space charge effect, charged particles with the opposite charge to the charged particles in the beam are irradiated onto the beam orbit. This reduces the space charge because both positive and negative charged particles exist on the beam orbit.

[0005] A technique for suppressing the space charge effect on an electron beam is described in Japanese Patent Laid-Open No. 2003-222299.

[0006] However, when a neutralizing agent is injected to reduce the space charge effect of a charged particle beam, the reaction between the charged particle beam and the neutralizing agent also neutralizes the charged particle beam itself. The neutralized beam cannot be accelerated or controlled by electromagnetic interactions, so it is lost during beam transport. In other words, it is necessary to effectively reduce the space charge while minimizing the loss of the charged particle beam.

[0007] To achieve this, it is necessary to increase the amount of neutralizing agent injected in areas where the trajectory of the charged particle beam is concentrated and the space charge is high, and to decrease the amount of neutralizing agent injected in areas where the trajectory is broadened and the space charge is low.

[0008] Patent Document 1 describes a method for uniformly neutralizing space charge in a vertical plane by irradiating an ion beam from an axially symmetric direction in the vertical plane with respect to the trajectory of an electron beam, and also describes an apparatus for efficiently reducing the space charge effect by adjusting the irradiation position of the ion beam depending on the magnitude of the current density.

[0009] However, the technique described in Patent Document 1 is premised on the neutralization of local space charges in a small system such as an electron beam exposure apparatus.

[0010] In large-scale systems such as industrial and medical charged particle beam accelerators, it is necessary to control the amount of neutralizing agent injected, taking into account its distribution after injection. It is also necessary to control the neutralizing agent distribution while taking into account beam losses due to interactions between the charged particle beam and the neutralizing agent.

[0011] To provide a stable charged particle beam for a long period of time, a device is required that can control the amount and distribution of the neutralizing agent injected according to changes in the state of the charged particle beam and the device.

[0012] The present invention provides a charged particle beam transport device and a method for neutralizing a charged particle beam that can provide a stable supply of a charged particle beam for a longer period of time than conventional methods.

[0013] The present invention includes a plurality of means for solving the above-mentioned problems. One example of such a means is a charged particle beam transport device, which includes one or more neutralizing agent injection units arranged along the beam trajectory for injecting a neutralizing agent that neutralizes space charge, and an injection amount control device for controlling the injection amount of the neutralizing agent from the neutralizing agent injection units, and which controls the injection amount based on an evaluation of the space charge distribution and the beam loss rate.

[0014] According to the present invention, it is possible to realize a stable supply of a charged particle beam for a longer period of time than in the past. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments.

[0015] Fig. 1 is a schematic diagram of the configuration of a charged particle beam transport device according to a first embodiment; Fig. 2 is a diagram showing a control flow of injection amount of a space charge neutralizer according to the first embodiment; Fig. 3 is a schematic diagram of the configuration of a charged particle beam transport device according to a second embodiment; Fig. 4 is a schematic diagram of the configuration of a charged particle beam transport device according to a third embodiment; Fig. 5 is a diagram showing an example of an outline of data recorded in a recording device of the charged particle beam transport device according to the third embodiment;

[0016] Hereinafter, embodiments of the charged particle beam transport device and the method for neutralizing a charged particle beam of the present invention will be described with reference to the drawings. In the drawings used in this specification, identical or similar reference numerals are used to designate identical or corresponding components, and repeated description of these components may be omitted.

[0017] First Embodiment A first embodiment of a charged particle beam transport apparatus and a method for neutralizing a charged particle beam according to the present invention will be described with reference to FIGS. 1 and 2. FIG.

[0018] First, the overall configuration of a charged particle beam transport system will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of the configuration of a charged particle beam transport system according to a first embodiment.

[0019] The charged particle beam transport device 20 shown in FIG. 1 is a device for transporting charged particles generated in a plasma generation device 1 to downstream equipment, and is composed of a charged particle beam 2, a vacuum chamber 3, a focusing coil 4, a bending electromagnet 5, injection ports 8a, 8b, and 8c, flow rate regulators 9a, 9b, and 9c, measuring devices 10a, 10b, and 10c, an arithmetic unit 11, and a control unit 12.

[0020] The plasma generating device 1 is a device that generates a charged particle beam, and can be any of a variety of devices, such as a microwave ion source, an ECR (Electron Cyclotron Resonance) ion source, a duoplasmatron, an electron gun, etc. In this embodiment, a configuration employing a microwave ion source will be described as an example.

[0021] The plasma generated in the plasma generating device 1 is extracted by the potential difference with the extraction electrode 6, and a charged particle beam 2 is generated.

[0022] The charged particle beam 2 is focused by a focusing coil 4 in a vacuum chamber 3, deflected by a bending electromagnet 5, and transported to a downstream device such as a post-accelerator. Here, the focusing coil 4 can be provided with magnetic poles made of a magnetic material.

[0023] Here, the post-accelerator is, for example, a radio frequency accelerator such as an RFQ (Radio Frequency Quadrupole) or a DTL (Drift Tube Linac), and either one or both of these can be used. Alternatively, it can be an electrostatic accelerator such as a Cockcroft-Walton type or a Van de Graaff type. It can also be an electromagnet for orbital control or a neutralization cell for neutralizing the beam.

[0024] When the charged particle beam 2 is transported through the vacuum chamber 3, it diverges due to Coulomb repulsion between the charged particles that make up the charged particle beam 2. This is called the space charge effect.

[0025] The beam divergence due to the space charge effect can be expressed by the following equation (1).

[0026]

[0027] In equation (1), F is the force acting on the charged particles that make up the charged particle beam 2, and is expressed as a function of the electric field E and magnetic flux density B perpendicular to the beam direction, as well as the elementary charge e and velocity v, as shown in the second term. As can be seen from the above equation, the forces of the electric field and the magnetic field cancel each other out.

[0028] This is expressed as the third term, where the elementary charge e and the charge density ρ ０ , dielectric constant ε ０ When we transform this into a function of the distance r from the central orbit, the speed of light c, and the velocity v, we can see that the divergence force increases as the velocity decreases.

[0029] From equation (1), it can be seen that the low-energy charged particle beam 2 before acceleration is more strongly affected by the space charge effect and diverges.

[0030] Emittance, which is expressed as the phase space area of ​​the positions and momentum of the charged particles that make up the beam, is an index that indicates the divergence of the charged particle beam 2. Emittance, which increases due to the space charge effect, etc., cannot be reduced unless a special process called beam cooling is used.

[0031] For example, when the charged particle beam 2 is focused by the focusing coil 4, the charged particles constituting the charged particle beam 2 can be focused to the center of the orbit, but the dispersion of the momentum increases. Therefore, even if the charged particle beam 2 is focused by the focusing coil 4, the emittance cannot be reduced.

[0032] A large emittance means that the trajectory of the charged particle beam 2 diverges or the momentum dispersion of the constituent charged particles is large, resulting in loss due to departing from the stable control range in the downstream transport system or accelerator.

[0033] In order to prevent the emittance from increasing, it is necessary to reduce the Coulomb force expressed by equation (1). Since the Coulomb force is proportional to the charge density, the charge density on the orbit of the charged particle beam 2 must be reduced.

[0034] Here, reducing the charge density on the orbit of the charged particle beam 2 means spatially reducing the charge by arranging charged particles having an opposite charge to that of the charged particle beam 2 on the orbit. This is called space charge reduction or neutralization.

[0035] In order to neutralize the space charge, there is a method of injecting a neutralizing agent onto the trajectory of the charged particle beam 2. Here, the neutralizing agent may be a neutral gas, an electron beam, an ion beam, or plasma.

[0036] For example, when a neutral gas is injected onto the orbit of the charged particle beam 2, the charged particles in the beam react with the neutral gas, causing a reaction in which electrons are ionized from the neutral gas.

[0037] When the charged particle beam 2 is composed of positively charged ions, electrons ionized from the neutral gas are accumulated on the orbit due to the Coulomb force between the beam particles and the electrons. On the other hand, ions ionized from the neutral gas are removed from the beam orbit due to the repulsive force from the charged particle beam 2. In this way, the space charge is neutralized by the accumulation of electrons on the orbit of the positively charged charged particle beam 2.

[0038] Even when an electron beam, an ion beam, or a plasma is used as a neutralizer, the beam neutralization process is similar except for the ionization process of the neutral gas.

[0039] In this embodiment, an example will be described in which a neutral gas is used as the neutralizing agent.

[0040] One or more injection ports 8a, 8b, and 8c are provided along the beam trajectory and are used to inject a neutralizing agent to neutralize the space charge. In this embodiment, three injection ports are provided, but the number of injection ports is not limited to three and can be one or more. It is also possible to provide multiple injection ports at the same position on the beam trajectory.

[0041] The flow rate regulators 9a, 9b, and 9c are provided on the pipes connecting the cylinder 7 containing the neutral gas to the injection ports 8a, 8b, and 8c, respectively, and regulate the amount of neutralizing agent injected from the injection ports 8a, 8b, and 8c. The control amount for controlling the injection amount is adjusted by the control device 12. It is desirable to provide the same number of flow rate regulators as the number of injection ports. In this embodiment, an example in which three flow rate regulators are provided is shown, but the number of flow rate regulators is not limited to three and can be one or more. It is also possible to provide multiple flow rate regulators at the same position in the beam trajectory direction. In this case, it is desirable to change their radial positions.

[0042] The measuring instruments 10a, 10b, and 10c are measuring devices that measure beam trajectories or charge densities, and can be various measuring instruments, such as destructive types using wires or electrodes, or non-destructive types using gas or optical sensors.

[0043] As with the inlets 8a, 8b, 8c and the flow rate regulators 9a, 9b, 9c, the installation positions and number of the measuring instruments 10a, 10b, 10c do not need to be the same as those of the neutralizing agent inlets 8a, 8b, 8c. The trajectory of the charged particle beam 2 outside the measurement range of the measuring instruments 10a, 10b, 10c can be estimated from the measurement values ​​by beam trajectory calculation or the like. Alternatively, the beam trajectory of the entire beam transport device may be estimated only by beam trajectory calculation without installing the measuring instruments 10a, 10b, 10c.

[0044] The calculation device 11 is a part that evaluates the space charge distribution and the beam loss rate, and preferably calculates the space charge distribution on the beam orbit evaluated based on the beam orbit or charge density measured by the measuring instruments 10 a, 10 b, and 10 c, the distribution of the neutralizing agent, and the amount of neutralizing agent to be injected based on the calculation results of the beam loss rate, and outputs a signal related to the calculated injection amount to the control device 12.

[0045] The control device 12 receives the signal, calculates the adjustment amount of the flow regulators 9a, 9b, and 9c to realize the injection amount of neutralizing agent from each injection port 8a, 8b, and 8c, and controls the operation of the flow regulators 9a, 9b, and 9c.

[0046] The arithmetic unit 11, the control unit 12, and the recording unit 16 of a third embodiment described later are configured by a computer having, for example, a display device such as a liquid crystal display, an input device, a recording device, a CPU, a memory, etc. The operation of each device is controlled by the arithmetic unit 11 and the control unit 12 based on various programs recorded in the recording device.

[0047] The control processes for the operations executed by the arithmetic unit 11 and the control unit 12 may be integrated into one program, or may be divided into multiple programs, or may be a combination of these. Furthermore, some or all of the programs may be realized by dedicated hardware or may be modularized.

[0048] Neutral gas for reducing space charge is injected through injection ports 8a, 8b, and 8c, and the injection amount is adjusted by flow rate regulators 9a, 9b, and 9c.

[0049] If the amount of neutralizing agent injected is insufficient, the space charge is not neutralized sufficiently, causing the charged particle beam 2 to diverge. On the other hand, if the amount of neutralizing agent injected is excessive, the charged particles in the charged particle beam 2 interact with charged particles having the opposite charge, causing the charged particle beam 2 to be neutralized.

[0050] The neutralized charged particle beam 2 is not deflected by the bending electromagnet 5 and is lost without being transported to the downstream equipment. Since the neutralized beam cannot be controlled by electromagnetic force, the trajectory cannot be controlled and the beam is lost even in configurations other than this embodiment.

[0051] In order to minimize the loss of the charged particle beam 2 due to the injection of the neutralizing agent while suppressing beam divergence by space charge neutralization to the specifications required by the device, it is necessary to control the distribution of the neutralizing agent according to the space charge distribution on the beam orbit.

[0052] In the region of the beam orbit where the space charge is high, the beam divergence due to the space charge effect is large, so the neutralizer density must be increased. On the other hand, in the region of the beam orbit where the space charge is low, the space charge effect is small, so the neutralizer density must be reduced to take into account the loss due to beam neutralization.

[0053] As described above, by measuring the trajectory and charge density of the charged particle beam 2 with the measuring instruments 10a, 10b, and 10c, the space charge distribution on the beam trajectory at each moment can be evaluated almost in real time.

[0054] Here, the beam trajectory calculation can be performed using a linear calculation using a transfer matrix or a numerical simulation such as Particle In Cell (PIC).

[0055] The charge distribution on the trajectory of the charged particle beam 2 can be evaluated by the above-described trajectory calculation, and therefore the amount and distribution of neutral gas required for neutralization can be determined.

[0056] The neutral gas distribution in the vacuum chamber 3 can be calculated by molecular flow simulation, assuming that the mean free path is sufficiently long.

[0057] The number of electrons ionized from the neutral gas can be expressed by the velocity, cross-sectional area, and respective densities of the charged particle beam 2. The generated electrons are diffused and lost due to the energy at the time of generation, the distribution of the space potential, recombination with the charged particle beam 2, and the like.

[0058] The electron density on the orbit of the charged particle beam 2 when the neutral gas is injected is expressed by equation (2).

[0059]

[0060] (2) In the formula, ρ ｅ , ρ ｉ and ρ ｎ represents the densities of the electrons, beam particles, and neutral gas. σ, v, and d represent the cross-sectional area of ​​the beam and neutral gas, the velocity of the beam particles, and the diffusion and extinction coefficients.

[0061] density ρ ｉ and ρ ｎ can be determined by beam trajectory calculations and molecular flow simulations. The velocity v of the beam particle is determined by the acceleration conditions. The cross-sectional area σ can be determined by referring to cross-sectional area data.

[0062] The diffusion / dissipation coefficient d can be calculated by numerical calculation using PIC or a fluid model, or can be determined experimentally.

[0063] The neutralization rate of the charged particle beam 2 due to the injection of the neutral gas can also be determined by numerical simulation or experiment.

[0064] By incorporating the electron density and neutralization rate on the orbit of the charged particle beam 2 into the beam orbit calculation, the emittance after space charge neutralization can be evaluated.

[0065] Orbit calculations taking space charge neutralization into account are possible by multiplying the charge density by the space charge neutralization rate in the Poisson equation being calculated, as shown in equation (3).

[0066]

[0067] In equation (3), ΔΦ is the electric potential, ρ is the charge density of the charged particle beam 2, and ε ０represents the dielectric constant of a vacuum. By multiplying this charge density ρ by the space charge neutralization rate α, the electric potential when the space charge is neutralized can be calculated.

[0068] The space charge neutralization rate α is calculated by multiplying equation (2) by the charge density ρ of the charged particle beam 2. ｉ This can be expressed as equation (4) divided by

[0069]

[0070] In addition, since the beam neutralization rate is proportional to the number of electrons on the beam orbit, the beam loss rate due to neutralization can also be calculated.

[0071] The beam trajectory calculation taking into account space charge neutralization as described above may be performed by solving all interactions between the charged particle beam 2 and neutral gas particles using the Monte Carlo method. However, with the current computer performance, it is impossible to calculate the behavior of all charged particles, so an approximation method is used in which only superparticles, which are a collection of many particles, are calculated.

[0072] Other computational methods such as fluid simulations can also be applied, but because of the issue of experimental reproducibility, it is necessary to apply an appropriate computational method for each evaluation system.

[0073] From the above, the distribution of the neutralizing agent required can be calculated by calculating the beam trajectory of the entire beam transport system.

[0074] In actual operation, it is preferable to evaluate the space charge distribution of the entire beam transport system and the necessary neutral gas distribution based on the beam trajectory measured by measuring instruments 10a, 10b, and 10c using a calculation device 11. Based on the evaluation results, a control device 12 controls a plurality of flow rate regulators 9a, 9b, and 9c to adjust the amount of neutralizing agent injected from injection ports 8a, 8b, and 8c.

[0075] The control flow for the injection amount and position of the neutralizing agent in this embodiment will be described with reference to Fig. 2. Fig. 2 is a diagram showing the control flow for the injection amount of the space charge neutralizing agent.

[0076] Step S101: The trajectory and current density of the charged particle beam 2 are measured by the measuring instruments 10a, 10b, and 10c.

[0077] Step S102: Based on the measurement results of the measuring instruments 10a, 10b, and 10c obtained in step S101, the calculation device 11 calculates the space charge distribution on the beam orbit and the distribution of the necessary neutralizing agent.

[0078] Step S103: The distribution of the neutralizing agent when the injection amount from each of the injection ports 8a, 8b, and 8c is changed is calculated by molecular flow simulation.

[0079] Step S104: Determine whether the neutralizer distribution calculated in step S103 satisfies the required value. If it does not, return to step S103 and calculate the neutralizer distribution under different conditions. If it does satisfy the required value, proceed to step S105.

[0080] Step S105: The flow rate regulators 9a, 9b, and 9c are controlled by the control device 12 to adjust the amount of neutralizing agent injected so that the conditions required in step S104 are met.

[0081] Step S106: It is determined whether the beam meets the target values ​​in step S105. Here, an index other than emittance may be used as an index of the beam divergence. If the emittance and beam loss rate meet the target values, the control flow ends. On the other hand, if the emittance and beam loss rate do not meet the target values, step S107 is executed.

[0082] Step S107: If the target value is not met in step S106, the difference between the calculation result after adjusting the neutralizer distribution and the measurement result is added as a correction amount, and the calculation in step S102 is performed again to execute the control flow again.

[0083] Next, the effects of this embodiment will be described.

[0084] The charged particle beam transport device 20 of the first embodiment of the present invention described above includes one or more injection ports 8 a, 8 b, and 8 c arranged along the beam trajectory for injecting a neutralizing agent for neutralizing space charge, flow rate regulators 9 a, 9 b, and 9 c for controlling the injection amount of the neutralizing agent from the injection ports 8 a, 8 b, and 8 c, and a control device 12, and controls the injection amount based on evaluation of the space charge distribution and the beam loss rate.

[0085] This allows the amount and position of neutralizing agent injection to be controlled for all charged particle beams, taking into account the charged particle beam trajectory and neutralizing agent distribution throughout the entire beam transport system, thereby suppressing losses due to beam neutralization and efficiently reducing space charge, thereby achieving low-divergence and highly efficient beam transport.As a result, it is possible to provide a stable charged particle beam for a longer period of time than conventional methods.

[0086] Such a charged particle beam transport device 20 is suitable for use in a linear accelerator, but can also be applied to an ion supply source in a nuclear fusion power reactor, neutron capture therapy (BNCT: Boron Neutron Capture Therapy), or a particle beam therapy device using a synchrotron accelerator.

[0087] The system further includes a calculation unit 11 for evaluating the space charge distribution and the beam loss rate. The calculation unit 11 determines the injection amount based on the calculation results of the space charge distribution on the beam orbit, the distribution of the neutralizing agent, and the beam loss rate, and therefore, it is possible to realize control of the injection amount of the neutralizing agent according to the state of the charged particle beam using the processing described above.

[0088] Furthermore, by further providing measuring instruments 10a, 10b, and 10c for measuring the beam trajectory or charge density, and evaluating the space charge distribution based on the beam trajectory or charge density measured by the measuring instruments 10a, 10b, and 10c, it is possible to realize control of the injection amount of neutralizing agent according to the state of the charged particle beam at each time.

[0089] In the above embodiment, the calculation device 11 evaluates the space charge distribution and the beam loss rate using the measurement results of the measuring instruments 10 a, 10 b, and 10 c, but the operator may evaluate the space charge distribution and the beam loss rate using the measurement results of the measuring instruments 10 a, 10 b, and 10 c. In this case, the operator also manually controls the injection amount of the neutralizing agent that neutralizes the space charge.

[0090] Alternatively, without providing the measuring instruments 10a, 10b, and 10c, the space charge distribution and the beam loss rate can be evaluated in advance by beam trajectory calculation or the like during the design and manufacturing stages of the charged particle beam transport device 20, and the injection amount of the neutralizing agent can be controlled automatically or manually based on the evaluation results during the design and manufacturing stages.

[0091] Second Embodiment A charged particle beam transport system and a method for neutralizing a charged particle beam according to a second embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a schematic diagram of the configuration of the charged particle beam transport system according to the second embodiment.

[0092] The charged particle beam transport system 20A of this embodiment shown in FIG. 2 is a system that uses either electrons or ions as a neutralizing agent, and generates electrons or ions to neutralize the space charge on the beam orbit.

[0093] When an electron beam, ion beam, or plasma is used as the neutralizing agent, an electron gun, an ion source, a plasma source, or the like is used, and the amount of implantation is controlled by the device configuration, such as the applied voltage, current, or incident angle.

[0094] For example, one or more ion generators 13a and 13b are arranged along the trajectory of the charged particle beam 2 to generate an ion beam having an opposite charge to that of the charged particle beam 2. The ion generation method may be a filament or microwave.

[0095] The ions generated by the ion generators 13a and 13b are irradiated onto the trajectory of the charged particle beam 2 due to the potential difference.

[0096] The ion beam irradiation dose can be controlled by the current or voltage supplied from the power supply 14. The ion beam irradiation dose can also be controlled by changing the flow rate of the gas injected into the ion generators 13a and 13b to generate ions.

[0097] The ion beam irradiation amount is controlled in the same manner as in the first embodiment.

[0098] As in the first embodiment, the space charge distribution and the necessary neutralizing agent distribution are calculated by the calculation device 11A based on the trajectory of the charged particle beam 2 measured by the measuring devices 10a, 10b, and 10c, and the irradiation doses of the ion generators 13a and 13b are adjusted based on the calculation results.

[0099] The other configurations and operations are substantially the same as those of the charged particle beam transport apparatus and the charged particle beam neutralization method of the first embodiment described above, and details thereof will be omitted.

[0100] The charged particle beam transport system and the charged particle beam neutralization method according to the second embodiment of the present invention also provide substantially the same effects as those of the charged particle beam transport system and the charged particle beam neutralization method according to the first embodiment described above.

[0101] <Third Embodiment> A charged particle beam transport apparatus and a method for neutralizing a charged particle beam according to a third embodiment of the present invention will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a schematic diagram of the configuration of the charged particle beam transport apparatus according to the third embodiment, and Fig. 5 is a diagram showing an example of an outline of data recorded in a recording device.

[0102] In the charged particle beam transport device 20B of this embodiment shown in Figure 4, the calculation device 11 in the charged particle beam transport device 20 of embodiment 1 is replaced with a recording device 16 having a table recording the injection amount of neutralizing agent for each beam condition, and the flow rate regulators 9a, 9b, 9c and the control device 12B are configured to control the injection amount by referring to the table for each beam condition.

[0103] In this embodiment, the emittance and beam loss rate are measured or calculated in advance for each amount of neutralizing agent injected from each of the injection ports 8a, 8b, and 8c, and the measurement or calculation results are stored in the recording device 16. The data stored in the recording device 16 is a table of the emittance and beam loss rate for each amount of neutralizing agent injected, as shown in FIG.

[0104] Then, the control device 12B refers to the amount of neutralizing agent injection required in accordance with the beam conditions to be used, and adjusts the flow rate regulators 9a, 9b, and 9c based on the reference result.

[0105] In the transliteration embodiment, if the conditions of the beam used change, a table must be created for each beam condition. Also, in order to control the injection amount of the neutralizing agent in response to the beam conditions that change during operation, a comprehensive table must be prepared for the beam conditions.

[0106] The other configurations and operations are substantially the same as those of the charged particle beam transport apparatus and the charged particle beam neutralization method of the first embodiment described above, and details thereof will be omitted.

[0107] The charged particle beam transport system and the charged particle beam neutralization method according to the third embodiment of the present invention also provide substantially the same effects as those of the charged particle beam transport system and the charged particle beam neutralization method according to the first embodiment described above.

[0108] In addition, a recording device 16 is provided which has a table recording the injection amount of neutralizing agent for each beam condition, and the flow rate regulators 9a, 9b, 9c and the control device 12B control the injection amount by referring to the table for each beam condition, thereby eliminating the need for calculation time as in embodiment 1 and enabling faster control.

[0109] The third embodiment is not limited to a configuration in which a neutral gas is used as a neutralizing agent, and may be a configuration in which electrons or ions are implanted as in the second embodiment.

[0110] <Others> The present invention is not limited to the above-described examples, and includes various modifications. The above-described examples have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations.

[0111] It is also possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of one embodiment to the configuration of another embodiment.It is also possible to add, delete, or replace part of the configuration of each embodiment with the configuration of another embodiment.

[0112] REFERENCE SIGNS LIST 1... Plasma generation device 2... Charged particle beam 3... Vacuum chamber 4... Convergence coil 5... Deflection electromagnet 6... Extraction electrode 7... Cylinder 8a, 8b, 8c... Inlet (neutralizing agent injection section) 9a, 9b, 9c... Flow rate regulator (injection amount control device) 10a, 10b, 10c... Measuring device (measuring device) 11, 11A... Arithmetic device 12, 12B... Control device (injection amount control device) 13a, 13b... Ion generation device 14... Power supply 16... Recording device 20, 20A, 20B... Charged particle beam transport device

Claims

1. A charged particle beam transport device comprising: one or more neutralizing agent injection units arranged along the beam trajectory for injecting a neutralizing agent that neutralizes space charge; and an injection amount control device for controlling the injection amount of the neutralizing agent from the neutralizing agent injection units, wherein the injection amount is controlled based on an evaluation of the space charge distribution and the beam loss rate.

2. A charged particle beam transport device as claimed in claim 1, further comprising a calculation device for evaluating space charge distribution and beam loss rate, said calculation device determining said injection amount based on the calculation results of said space charge distribution on said beam orbit, said distribution of said neutralizing agent, and said beam loss rate.

3. A charged particle beam transport device as claimed in claim 1, further comprising a recording device having a table in which the injection amount of the neutralising agent for each beam condition is recorded, and the injection amount control device controls the injection amount by referring to the table for each beam condition.

4. A charged particle beam transport apparatus according to claim 2 or 3, further comprising a measuring device for measuring the beam trajectory or charge density, and evaluating the space charge distribution based on the beam trajectory or the charge density measured by the measuring device.

5. A charged particle beam transport apparatus according to claim 1, wherein the neutralizing agent is any one of a neutral gas, electrons, and ions.

6. A method of neutralizing a charged particle beam in which a neutralizing agent for neutralizing the space charge is injected from one or more neutralizing agent injection sites positioned along the beam trajectory based on an evaluation of the space charge distribution and the beam loss rate.

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