Accelerator system and discharge detector

Abstract

The invention provides an accelerator system and a discharge detector capable of suppressing the influence of discharge on the interior of an accelerator. An accelerator system (100) is provided with a discharge detector (60) that detects discharge inside an accelerator (1). And a discharge detector (60) that detects a continuous discharge and thereby cuts off the discharge at a stage prior to the occurrence of an influence caused by the discharge inside the accelerator (1). Therefore, even if a continuous discharge has occurred inside the accelerator (1), the influence caused by the discharge can be suppressed by cutting off the discharge in advance. As a result, the influence of discharge on the interior of the accelerator (1) can be suppressed.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2023-218202 filed on December 25, 2023. The entire content of the Japanese application is incorporated herein by reference. Technical Field

[0002] The present invention relates to an accelerator system and a discharge detector. Background Art

[0003] Conventionally, as a technique in this field, an accelerator system described in Patent Document 1 below is known. The accelerator system generates a high-frequency electric field in a chamber inside the accelerator to accelerate particles.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-110040

[0005] Here, in the above accelerator system, discharge sometimes occurs inside the accelerator (e.g., in the chamber). In the case of continuous discharge among such discharges, effects caused by the discharge such as discharge craters, current paths, and scratches on the inner wall are generated inside the accelerator. Thus, if effects caused by the discharge occur, problems such as breakage of parts inside the accelerator and deterioration of performance may occur. Regarding such problems, a method of confirming the discharge by increasing and decreasing the vacuum degree inside the accelerator has been conventionally adopted. Since this method detects based on an indirect index generated due to the occurrence of continuous discharge, the time lag from the occurrence of continuous discharge to detection is large. Therefore, there is a problem that the effects generated inside the accelerator due to continuous discharge cannot be sufficiently suppressed. Summary of the Invention

[0006] An object of the present invention is to provide an accelerator system and a discharge detector capable of suppressing the influence of discharge on the inside of the accelerator.

[0007] The accelerator system of the present invention includes: an accelerator that accelerates particles; and a discharge detector that detects discharge inside the accelerator, wherein the discharge detector detects continuous discharge and cuts off the discharge at a stage prior to the generation of effects caused by the discharge inside the accelerator based on this.

[0008] The accelerator system according to the present invention includes a discharge detector that detects discharge inside the accelerator. The discharge detector detects continuous discharge and cuts off the discharge at a stage prior to the generation of effects caused by the discharge inside the accelerator based on this. Therefore, even when continuous discharge has occurred inside the accelerator, by cutting off the discharge in advance, the effects caused by the discharge can be suppressed. Thereby, the influence of discharge on the inside of the accelerator can be suppressed.

[0009] The discharge detector can cut off the discharge according to the electrical waveform of the chamber of the accelerator. The electrical waveform of the chamber is different from the degree of vacuum inside the accelerator, etc., and can directly detect the occurrence of discharge. Therefore, in the case of continuous discharge, the discharge detector can quickly detect the discharge.

[0010] The accelerator system may include an upper system that controls the accelerator and a control unit that controls the voltage applied to the chamber of the accelerator. The control unit has a discharge detector. At this time, the discharge detector can detect the discharge in the control unit that controls the chamber without going through the upper system. Therefore, the discharge detector can quickly detect the discharge.

[0011] The discharge detector can cut off the discharge when it detects that the number of discharges within a specified time in the chamber of the accelerator is equal to or more than a specified number. At this time, the discharge detector can detect continuous discharges of the type where single discharges occur repeatedly.

[0012] The discharge detector can cut off the discharge when it detects that the discharge in the chamber of the accelerator has continued for more than a specified time. At this time, the discharge detector can detect continuous discharges of the type where the discharge continues.

[0013] The discharge detector can cut off the discharge when the electrical waveform of the chamber of the accelerator has been short-circuited for a specified time. At this time, the discharge detector can detect continuous discharges caused by the short circuit.

[0014] The discharge detector according to the present invention is a discharge detector that detects discharges inside an accelerator that accelerates particles. Among them, the discharge detector can detect continuous discharges and, based on this, cut off the discharge at a stage prior to the occurrence of an impact caused by the discharge inside the accelerator.

[0015] According to this discharge detector, the same operational effects as the above accelerator system can be obtained.

[0016] According to the present invention, there is provided an accelerator system and a discharge detector that can suppress the influence of discharges on the inside of the accelerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a block diagram showing the accelerator system according to the present embodiment.

[0018] Figure 2 is a perspective view showing the accelerator.

[0019] Figure 3 is a schematic view showing the chamber.

[0020] Figure 4 is a graph showing the waveform for detection by the discharge detector.

[0021] Figure 5It is a circuit diagram showing the circuit structure of a discharge detector.

[0022] Figure 6 It is a block diagram showing the accelerator system related to the comparative example.

[0023] Figure 7 It is a chart showing the waveform for detecting discharge of the accelerator system related to the comparative example.

[0024] Figure 8 It is a photograph showing an example of the influence of continuous discharge on the inside of the accelerator.

[0025] In the figure: 1 - accelerator, 6 - chamber, 60 - discharge detector, 100 - accelerator system. Detailed implementation mode

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and repeated descriptions are omitted. And the positional relationships such as up, down, left, and right are set based on the positional relationships of the drawings.

[0027] Figure 1 It is a block diagram showing the accelerator system 100 according to the present embodiment. As Figure 1 shown, the accelerator system 100 includes an accelerator 1 and a control system 101. The accelerator 1 is a device that accelerates particles to generate a beam. The control system 101 controls the accelerator 1.

[0028] Refer to Figure 2 to describe the accelerator 1. Figure 2 It is a perspective view showing the inside of the accelerator 1. In Figure 2 it, a state is shown in which the upper side of the accelerator 1 is disassembled and the built-in parts are visible. In the present embodiment, a cyclotron is exemplified as the accelerator 1.

[0029] The accelerator 1 is a device that generates a proton beam, and accelerates cations (particles) of hydrogen supplied from an ion source (not shown) inside a vacuum vessel 3 to generate and emit a proton beam. The vacuum vessel 3 is formed of, for example, stainless steel or the like. And a vacuum pump (not shown) is connected to the vacuum vessel 3. The vacuum vessel 3 forms a vacuum environment for ion acceleration inside.

[0030] The accelerator 1 includes a yoke 4 arranged opposite to each other up and down and an exciting coil 5 that forms a magnetic field inside the vacuum vessel 3. And the accelerator 1 includes a chamber 6 that generates a high-frequency electric field to impart energy to the proton beam and an RF tuner 11 that adjusts the resonance frequency of the chamber 6.

[0031] A magnetic field is formed within the vacuum vessel 3 by means of the yoke 4 and the exciting coil 5, and a high-frequency electric field is formed by the cavity 6. Thus, the proton beam performs a rotational motion in a helical orbit, and as the radius of the rotational orbit increases, the traveling speed of the proton beam increases. Additionally, in Figure 2 the lower yoke 4 is illustrated, and the upper yoke 4 is omitted.

[0032] Moreover, the accelerator 1 is provided with: a deflector 7 provided on the inner surface side of the side wall of the vacuum vessel 3 and used for extracting the accelerated proton beam, a gradient corrector 8 for correcting the magnetic field gradient, a collimator 9 for emitting the proton beam in a specified direction (horizontal direction), and a permanent magnet quadrupole magnet (quadrupole) 10 for adjusting the focus of the emitted proton beam. The accelerated proton beam within the vacuum vessel 3 is extracted by the deflector 7, the magnetic field gradient is corrected by the gradient corrector 8, and the emission direction is adjusted by the collimator 9. The focus of the emitted proton beam is adjusted by the permanent magnet quadrupole magnet 10.

[0033] Figure 3 is a schematic cross-sectional view of the cavity 6. In the accelerator 1, a pair of cavities 6 are provided above and below sandwiching the passage of the proton beam B. As Figure 3 shown, the pair of cavities 6 have the same or equivalent structures that are substantially symmetric above and below each other. Therefore, hereinafter, in order to omit repeated explanations, only the structure of the lower cavity 6 will be described.

[0034] The cavity 6 has a D-shaped electrode 21, a ground plate 23, and a stem 27. The ground plate 23 is separated from the D-shaped electrode 21, and is in the shape of a bottomed cup that internally houses the D-shaped electrode 21, and is embedded in the recess of the yoke 4. The ground plate 23 is made of, for example, oxygen-free copper. A stem 27 extends upward from the bottom surface of the ground plate 23, and the D-shaped electrode 21 is fixed to the upper end of the stem 27.

[0035] The upper edge portion of the ground plate 23 constitutes the D-box 29. And a gap is provided between the upper edge portion of the ground plate 23 and the D-shaped electrode 21, and this gap constitutes the acceleration gap G between the D-shaped electrode 21 and the D-box 29. A high-frequency electric field corresponding to the rotational phase of the proton beam B is generated between the D-shaped electrode 21 and the D-box 29, whereby the proton beam B is accelerated each time it passes through the acceleration gap G.

[0036] Return to Figure 1, the control system 101 includes an upper-level system 50, a control unit 51, and an amplifier 52. The upper-level system 50 is a system that controls the accelerator 1. The upper-level system 50 controls the overall operation of the accelerator 1. The control unit 51 controls the application of voltage to the chamber 6 of the accelerator 1. The control unit 51 receives a control signal from the upper-level system 50 and controls the chamber 6 according to this control signal. The amplifier 52 is a device that amplifies the input signal input from the control unit 51 to the chamber 6.

[0037] The control unit 51 has a discharge detector 60. The discharge detector 60 detects discharges inside the accelerator 1. The discharge detector 60 is a device that detects continuous discharges and cuts off the discharge at the previous stage based on this to generate an impact caused by the discharge inside the accelerator 1. Here, since the chamber 6 has electrodes that apply a high electric field, a discharge phenomenon will occur. The discharge phenomenon includes single discharges and continuous discharges. A single discharge is a discharge phenomenon where the discharge is single and completed in a short time. A continuous discharge is a discharge phenomenon where the discharges occur continuously. The continuous discharge includes a type of discharge that repeats multiple single discharges in a short period (represented by "TP1" in Figure 4 and a type of discharge where the discharge continues for a specified time (represented by "TP2" in Figure 4 ).

[0038] Continuous discharges can generate impacts such as internal discharge craters in the chamber 6, current paths, and scratches on the inner wall (impacts caused by discharges), and there is a possibility of chamber breakage and performance degradation. Therefore, the discharge detector 60 implements an interlock when continuous discharges occur and cuts off the discharge at the previous stage before an impact caused by the discharge is generated inside the accelerator 1, thereby protecting the chamber 6. Figure 8 In (a) in Figure 8 is a photograph showing the internal state of the chamber 6 before an impact caused by the discharge appears although continuous discharges have occurred. As Figure 8 shown by "A" in (b) in

[0039] , in the case of continuous discharges, it shows a situation where an impact caused by the discharge has occurred after the protection based on the discharge detector 60 of the present embodiment has not been performed. As shown by "A" in (b) in Figure 4As shown, the discharge detector 60 detects a situation where continuous discharge has occurred based on the waveform of the chamber voltage obtained by detecting the chamber voltage of the detection chamber 6. Then, if it is detected based on the waveform that continuous discharge has occurred, the discharge detector 60 implements an interlock, thereby interrupting the application of voltage to the chamber 6 and cutting off the discharge.

[0040] Specifically, the discharge detector 60 cuts off the discharge when it detects that the number of discharges within a specified time in the chamber 6 of the accelerator 1 is equal to or more than a specified number. As Figure 4 shown, in the case where no discharge occurs, the chamber voltage becomes a constant voltage. In contrast, if discharge occurs, the chamber voltage becomes lower than the discharge threshold TH. If a discharge lower than the discharge threshold TH is detected, the discharge detector 60 starts measuring time. In the case of continuous discharge of the type where single discharges repeat, the chamber voltage immediately recovers, but then the next single discharge immediately occurs. The discharge detector 60 counts the number of discharges. The discharge detector 60 only counts the number of discharges within a preset specified counting time T1. When the number of discharges generated during the counting time T1 is equal to or more than a preset specified count value, the discharge detector 60 detects that continuous discharge has occurred. Alternatively, the discharge detector 60 can detect continuous discharge at the moment when the number of discharges in the stage before passing through the counting time T1 reaches the specified count value. If continuous discharge is detected, the discharge detector 60 outputs an interlock signal, thereby interrupting the application of voltage to the chamber 6. Thus, the discharge of the chamber 6 is cut off. The length of the counting time T1 is not particularly limited and can be set arbitrarily, but for example, it can be set to about 2 μs to 65000 μs. In addition, the discharge period PD during continuous discharge is approximately 2 μs.

[0041] Moreover, the discharge detector 60 cuts off the discharge when it detects that the discharge in the chamber 6 of the accelerator 1 has continued for a specified time or more. That is, the discharge detector 60 cuts off the discharge when the electrical waveform of the chamber 6 of the accelerator 1 has short-circuited for a specified time. As Figure 4 shown, there are sometimes cases where, although a specified voltage is being applied to the chamber 6, the state where the chamber voltage is lower than the discharge threshold TH continues, resulting in waveform short-circuit (refer to Figure 4("TP2"). If a discharge lower than the discharge threshold TH is detected, the discharge detector 60 starts measuring time. In the case of continuous discharges of the type where the discharge continues, the state where the chamber voltage is lower than the discharge threshold TH continues without recovery. The discharge detector 60 determines whether this state has continued for a preset specified duration T2. If it is detected that the state where the chamber voltage is lower than the discharge threshold TH has continued for a duration of T2 or more, the discharge detector 60 detects that a continuous discharge has occurred. If a continuous discharge is detected, the discharge detector 60 outputs an interlock signal, thereby interrupting the application of voltage to the chamber 6. Thus, the discharge of the chamber 6 is cut off. In addition, the length of the duration T2 is not particularly limited and can be set arbitrarily. For example, it can be set to about 2 μs to 65000 μs.

[0042] Next, refer to Figure 5 An example of the specific structure of the discharge detector 60 will be described. Figure 5 It is a circuit diagram showing the circuit structure of the discharge detector 60. As Figure 5 shown, the discharge detector 60 includes a discharge detection circuit 61, a discharge duration detection circuit 62, an interval discharge count confirmation circuit 63, latches 64A, 64B, and an OR circuit 65.

[0043] The discharge detection circuit 61 is a circuit that monitors the chamber electric power and detects the occurrence of a discharge. In the discharge detection circuit 61, the value of the discharge threshold TH is pre-input before the accelerator 1 operates. Thus, the discharge detection circuit 61 sets the input value as the discharge threshold TH. During the operation of the accelerator 1, the chamber voltage is input to the discharge detection circuit 61. Thus, the discharge detection circuit 61 compares the input chamber voltage with the discharge threshold TH to detect a discharge. The discharge detection circuit 61 outputs the detection result of the discharge to the discharge duration detection circuit 62 and the interval discharge count confirmation circuit 63.

[0044] The discharge duration detection circuit 62 is a circuit that detects continuous discharges of the continuous type (TP2). In the discharge duration detection circuit 62, the value of the duration T2 is pre-input as a parameter before the accelerator 1 operates. The discharge duration detection circuit 62 sets the input value as the duration T2. If it is detected that the discharge has continued for a duration of T2 or more, the discharge duration detection circuit 62 outputs an interlock command signal to the OR circuit 65 via the latch 64A.

[0045] The interval discharge count confirmation circuit 63 is a circuit that detects continuous discharges of the type (TP1) in which single discharges are repeated. In the interval discharge count confirmation circuit 63, before the accelerator 1 operates, the count value and the value of the count time T1 are input in advance as parameters. The interval discharge count confirmation circuit 63 sets the input values as the count value and the count time T1. If it is detected that discharges equal to or more than the count value have continued for a duration T2 or more during the count time T1, the interval discharge count confirmation circuit 63 outputs a latching command signal to the OR circuit 65 via the latch 64A.

[0046] The latches 64A and 64B are devices having the function of maintaining the states of the circuits 62 and 63. If a latching command signal is received from each of the circuits 62 and 63, the latches 63A and 64 output the command signal to the OR circuit 65. If a latching command signal is received from at least one of the discharge duration detection circuit 62 and the interval discharge count confirmation circuit 63, the OR circuit 65 outputs the command signal to the latching section (not shown) of the control unit 51.

[0047] Next, the operation and effects of the accelerator system 100 and the discharge detector 60 according to the embodiment of the present invention will be described.

[0048] First, with reference to Figure 6 and Figure 7 the accelerator system 200 according to the comparative example will be described. In the accelerator system 200 according to the comparative example, a vacuum control board 70 is used instead of the above-described discharge detector 60 to detect continuous discharges. The vacuum control board 70 is a device that detects the degree of vacuum inside the chamber 6. The vacuum control board 70 receives the degree of vacuum inside the chamber 6 and outputs it to the host system 50. The host system 50 detects the occurrence of continuous discharges based on the received degree of vacuum, and if continuous discharges are detected, it implements latching. The host system 50 outputs a command signal for stopping the application of voltage to the chamber 6 to the control unit 51. According to this command signal, the control unit 51 interrupts the application of voltage to the chamber 6, thereby cutting off the discharge.

[0049] For example, in the accelerator system 200 according to the comparative example, as Figure 7 shown, the host system 50 performs detection based on a timing signal. If a deterioration in the degree of vacuum is detected, the host system 50 monitors for a specified time T3. If it is detected that the state of deteriorated degree of vacuum has continued for the specified time T3, the host system 50 detects continuous discharges. The timing signal of the host system 50 has a period of 1 Hz to 10 Hz, and one cycle takes about 0.1 s to 1 s. Therefore, the time T3 is set to about several seconds. And in Figure 7In this case, for convenience, a state in which the degree of vacuum rapidly changes is shown. However, even when continuous discharge occurs, the degree of vacuum gradually changes. Therefore, it takes a certain amount of time to detect the deterioration of the degree of vacuum. Thus, in the accelerator system 200 according to the comparative example, it takes about several seconds from the occurrence of continuous discharge to the implementation of the interlock. Therefore, during the period before the implementation of the interlock, the discharge may sometimes affect the chamber.

[0050] In contrast, the accelerator system 100 according to the present embodiment includes a discharge detector 60 that detects discharge inside the accelerator 1. The discharge detector 60 detects continuous discharge and thereby cuts off the discharge at a stage prior to the occurrence of an influence caused by the discharge inside the accelerator 1. Thus, even when continuous discharge has occurred inside the accelerator 1, by cutting off the discharge in advance, it is possible to suppress the occurrence of an influence caused by the discharge. Thereby, it is possible to suppress the influence of the discharge on the inside of the accelerator 1.

[0051] The discharge detector 60 can cut off the discharge based on the electrical waveform of the chamber 6 of the accelerator 1. The electrical waveform of the chamber 6 can directly detect the occurrence of discharge, which is different from the degree of vacuum inside the accelerator 1 and the like. Therefore, in the case of continuous discharge, the discharge detector 60 can quickly detect the discharge.

[0052] The accelerator system 100 may include an upper system 50 that controls the accelerator 1 and a control unit 51 that controls the voltage applied to the chamber 6 of the accelerator 1, and the control unit 51 includes the discharge detector 60. At this time, the discharge detector 60 can detect the discharge in the control unit 51 that controls the chamber 6 without going through the upper system 50. Therefore, the discharge detector 60 can quickly detect the discharge.

[0053] The discharge detector 60 can cut off the discharge when it detects that the number of discharges within a specified time in the chamber 6 of the accelerator 1 is equal to or more than a specified number. At this time, the discharge detector 60 can detect continuous discharge of the type in which single discharges repeatedly occur.

[0054] The discharge detector 60 can cut off the discharge when it detects that the discharge in the chamber 6 of the accelerator 1 has continued for more than a specified time. At this time, the discharge detector 60 can detect continuous discharge of the type in which the discharge continues.

[0055] The discharge detector 60 can cut off the discharge when the electrical waveform of the chamber 6 of the accelerator 1 has been short-circuited for a specified time. At this time, the discharge detector 60 can detect continuous discharge caused by the short circuit.

[0056] The discharge detector 60 according to this embodiment is a discharge detector 60 that detects discharges inside the accelerator 1 that accelerates particles. It can detect continuous discharges and, based on this, cut off the discharges at an earlier stage before the effects caused by the discharges occur inside the accelerator 1.

[0057] With this discharge detector 60, the same operational effects as those of the above-described accelerator system 100 can be obtained.

[0058] The present invention is not limited to the above-described embodiment.

[0059] The type of accelerator is not limited to a cyclotron. For example, as the accelerator, various accelerators such as a linear accelerator and a synchrotron can also be used. Also, the object for which discharges are detected is not limited to a chamber, and can be appropriately applied to any device that uses high frequency, such as a deflector or an ion source. Moreover, the present invention can be applied to all DC power supplies of the accelerator 1.

Claims

1. An accelerator system comprising: accelerators, which accelerate particles; and a discharge detector for detecting discharge inside the accelerator, The accelerator system is characterized in that The discharge detector detects continuous discharge and accordingly cuts off the discharge before an effect caused by the discharge occurs inside the accelerator.

2. The accelerator system according to claim 1, characterized in that The discharge detector cuts off discharge according to an electrical waveform of a chamber of the accelerator.

3. The accelerator system according to claim 1, characterized in that: have: A host system controls the accelerator; and a control unit for controlling a voltage applied to the chamber of the accelerator, The control unit includes the discharge detector.

4. The accelerator system according to claim 1, characterized in that: The discharge detector cuts off discharge when detecting that the number of discharges in the chamber of the accelerator within a predetermined time is equal to or greater than a predetermined number.

5. The accelerator system according to claim 1, characterized in that: The discharge detector cuts off the discharge when detecting that the discharge in the chamber of the accelerator continues for a predetermined time or longer.

6. The accelerator system according to claim 1, characterized in that: The discharge detector cuts off discharge when an electrical waveform in the chamber of the accelerator is short-circuited for a predetermined period of time.

7. A discharge detector for detecting discharge inside an accelerator for accelerating particles, characterized in that: The discharge detector detects continuous discharge and accordingly cuts off the discharge before an effect caused by the discharge occurs inside the accelerator.

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