Electric field measurement device and electric field measurement method

Abstract

To provide an electric field measurement device and an electric field measurement method capable of performing electric field measurement with higher accuracy when an electric field is measured by arranging a perturbation body in an acceleration cavity.SOLUTION: An electric field measurement device for measuring an electric field in an acceleration cavity includes: a perturbation body arranged in the acceleration cavity and perturbing the electric field; a support body disposed along an axial direction in the acceleration cavity to support the perturbation body; a drive mechanism for driving the support body to move the perturbation body; electric field measurement means for measuring an electric field in the acceleration cavity; and displacement measurement means for detecting displacement of the perturbation body from a reference position.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to an electric field measuring device and an electric field measuring method.

Background Art

[0002] Generally, in an accelerating cavity such as a linear accelerator (e.g., radio frequency quadrupole linear accelerator (RFQ), drift tube linac (DTL)), electric field measurement is performed to compare the electric field distribution of the fabricated cavity with the design value. As a method of electric field measurement, a perturbation (bead pull) method is known in which a small dielectric or metal perturbation body that causes a perturbation in the electric field is inserted into the accelerating cavity, and the electric field is measured from the change in the resonance frequency. As a specific method, the perturbation body is held by a thread, moved inside the accelerating cavity, the frequency at each point in the axial direction is measured, and converted into an electric field distribution (see, for example, Patent Document 1).

[0003] In the above-described electric field measurement, it is necessary to hold the perturbation body at a predetermined position. Due to the weight of the perturbation body, sag occurs in the thread holding the perturbation body, and if it deviates in the vertical direction, perturbation occurs at a position different from the original position, so the acquired electric field distribution will contain errors.

[0004] Such errors are particularly significant when the beam duct has a large diameter and wide-range measurements are performed, or when the antenna size for frequency measurement is limited due to constraints on the internal structure of the accelerating cavity, and the weight increases by increasing the size of the perturbation body to maintain the signal intensity.

[0005] Also, for wide-range measurements, the thread may deform due to long-term measurement, resulting in insufficient tension of the thread set at the beginning of the measurement. Further, if the displacement of the position of the perturbation body is measured in such a way that it mechanically contacts the perturbation body, the frequency fluctuates greatly and the electric field distribution cannot be measured. In the conventional method, the position of the perturbation body is determined only by the support structure of the thread, and the displacement of the position of the perturbation body generated inside the accelerating cavity appears as an error in the measured electric field distribution.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] As described above, in the conventional electric field measurement device and electric field measurement method, there is a problem that an error occurs in the electric field measurement inside the acceleration cavity, and the electric field cannot be measured with high precision.

[0008] The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric field measurement device and an electric field measurement method capable of performing more accurate electric field measurement when measuring an electric field by arranging a perturbing body in an acceleration cavity.

Means for Solving the Problems

[0009] The electric field measurement device according to the embodiment is an electric field measurement device for measuring an electric field inside an acceleration cavity, and includes a perturbing body that is arranged inside the acceleration cavity and gives a perturbation to the electric field, a support member that is disposed along the axial direction inside the acceleration cavity and supports the perturbing body, a drive mechanism that drives the support member to move the perturbing body, an electric field measurement means for measuring the electric field inside the acceleration cavity, and a displacement measurement means for detecting a displacement of the perturbing body from a reference position.

Effects of the Invention

[0010] According to the embodiment of the present invention, it is possible to provide an electric field measurement device and an electric field measurement method capable of performing more accurate electric field measurement when measuring an electric field by arranging a perturbing body in an acceleration cavity.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, an electric field measurement device and an electric field measurement method according to embodiments will be described with reference to the drawings.

[0013] (First Embodiment) First, a first embodiment will be described with reference to FIG. 1. In this first embodiment, the acceleration cavity 1 is the measurement target. The acceleration cavity 1 specifically includes, in addition to a simple pillbox cavity, cavities for accelerating and decelerating charged particles such as electrons and ions, such as a radio frequency quadrupole linear accelerator (RFQ), a drift tube linac (DTL), and other linear high-frequency acceleration cavities. Further, the target is generally cavities that change the behavior of the movement of charged particles by applying high-frequency power, such as bunchers and debunchers.

[0014] The support member 2 is arranged inside the acceleration cavity 1 along its axial direction. The support member 2 is supported by a support member fixture 3. The support member 2 is preferably made of a thin material with a small mass, such as a thread or a wire. Fishing lines such as nylon, fluorocarbon, and polyethylene can be applied.

[0015] The support member fixture 3 is used to fix the position of the support member 2 inside the acceleration cavity 1. The support member fixture 3 can have a shape like a pulley that rotates the contact part with the support member 2 to smoothly move the support member 2, or can have a shape such as providing holes or notches in a plate made of nylon or the like and passing the support member 2 through it. In any case, it is desirable to perform R processing on the contact part of the support member fixture 3 with the support member 2 to avoid damaging the support member 2.

[0016] A perturbation body 4 is connected to the support member 2. The shape of the perturbation body 4 is preferably a shape having symmetry such as a spherical shape, a cylindrical shape, or a rectangular parallelepiped shape. Examples of the material of the perturbation body 4 include dielectrics. In addition to materials with excellent processability such as nylon and acrylic, ceramics such as barium titanate, silicon nitride, and alumina with a high dielectric constant can be applied. The higher the dielectric constant, the greater the perturbation of the electric field even with the same volume, and the S / N ratio is improved. Also, it is possible to use metal in addition to the dielectric. In this case, aluminum with a low specific gravity is suitable.

[0017] A driving device 5 is connected to the support member 2. As the driving device 5, for example, by using a motor to drive the support member 2, the perturbation body 4 is conveyed inside the acceleration cavity 1, and the measurement position is changed. In addition to measuring the electric field while continuously conveying the perturbation body 4 using an induction motor or the like, the perturbation body 4 can be stopped at a specific position using a servo motor, a stepping motor, or the like for measurement.

[0018] Also, a weight 6 is connected to the support member 2 to generate tension so that the perturbation body 4 does not hang down due to its weight. The weight 6 can be configured by using the weight of the weight itself as it is, or by generating tension with an arm controlled by a motor. Further, a displacement measuring device 7 is arranged to detect the case where the perturbation body 4 hangs down and displacement occurs. The displacement measuring device 7 is not particularly limited as long as it can detect the displacement from a predetermined position of the perturbation body 4. The detection accuracy of the displacement in this case varies depending on the specifications of the acceleration cavity 1 and the perturbation body 4 used, the high-frequency power used for accelerating charged particles, etc. For example, it is about 1 millimeter to several millimeters.

[0019] For example, as the displacement measuring device 7, a device for measuring the tension or load applied to the perturbation body 4 can be used. For example, as the displacement measuring device 7, a contact (mechanical) tensiometer is used to contact the support member 2 to measure the tension. Alternatively, as the displacement measuring device 7, a sonic tensiometer or a tram tensiometer can be used to measure the tension non-contactingly from the vibration frequency, sound wave, etc. of the support member 2 or the perturbation body 4. Furthermore, a load measuring instrument can be used as the displacement measuring device 7 to measure the load. By using such a displacement measuring device 7, when the tension or load applied to the perturbation body 4 fluctuates from the original value, this can be detected as the displacement of the perturbation body 4.

[0020] An antenna 8 for frequency measurement is disposed in the acceleration cavity 1. As the structure of the antenna 8, for example, a loop made of a rod-shaped metal such as copper or stainless steel is connected to the vacuum surface side of a feed-through flange with an introduction terminal that can be vacuum-sealed. The shape of the loop is composed of a circular shape, an elliptical shape, a rectangular shape, or a combination of these shapes.

[0021] A frequency measuring device 9 is connected to the antenna 8 via a cable. As the frequency measuring device 9, a network analyzer or the like can be used. As the cable, a coaxial cable connected with a BNC connector, an N connector, an SMA connector, etc. can be used. Between the acceleration cavity 1 and the frequency measuring device 9, in addition to connecting one antenna 8 for absorption measurement, two antennas 8 can also be used for transmission measurement in two channels.

[0022] In the first embodiment configured as described above, the perturbation of the electric field in the acceleration cavity 1 caused by the perturbation body 4 can be measured by the frequency measuring device 9 as a change in frequency or phase. Therefore, in combination with the displacement measuring device 7, the measurement error can be suppressed by measuring the frequency or phase for converting to the electric field distribution only when the displacement of the perturbation body 4 does not occur.

[0023] (Second Embodiment) Next, the second embodiment will be described with reference to FIG. 2. Components identical to those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0024] In the second embodiment, a device that irradiates electromagnetic waves is used as the displacement measuring device 7. For example, as the displacement measuring device 7, a laser rangefinder or a reflection type laser sensor is installed outside the acceleration cavity 1, and the laser is irradiated toward the perturbation body 4.

[0025] In this case, for example, when no displacement occurs at the position of the perturbation body 4 and it remains at a predetermined position, the laser is not detected, and the displacement measuring device 7 is fixed at a position and direction where the laser is detected only when a displacement occurs. Alternatively, as shown in FIG. 2, a transmissive laser sensor separated into an irradiation body and a detection side of the electromagnetic wave is used. The irradiation body is installed outside the acceleration cavity 1, and the detection side is installed at the other end of the acceleration cavity 1. When the perturbation body 4 remains at a predetermined position, the laser is detected on the detection side, and the irradiation body and the detection side are fixed at positions and directions where the laser is not detected only when a displacement of the perturbation body 4 occurs. Lenses, filters, mirrors, etc. are arranged between the displacement measuring device 7 and the perturbation body 4 as necessary, and the displacement measuring device 7 and the perturbation body 4 do not have to be arranged in a straight line.

[0026] In the second embodiment configured as described above, when the perturbation body 4 is displaced from a predetermined position, the displacement measuring device 7 can detect the displacement. And the measurement error can be suppressed by measuring the frequency or phase for converting into the electric field distribution only when no displacement of the perturbation body 4 occurs.

[0027] (Third Embodiment) Next, the third embodiment will be described with reference to FIG. 3. Components identical to those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0028] In the third embodiment, as the displacement measuring device 7, an imaging device for the reflected light from the perturbation body 4 is used. Specifically, the imaging directions of a camera or a video camera are installed facing the perturbation body 4. If necessary, lenses, filters, mirrors, etc. are arranged on the optical path. In conjunction with the conveyance of the perturbation body 4, the position of the perturbation body 4 is photographed and recorded. Based on the image data of the recorded video or image, the position of the perturbation body 4 is estimated.

[0029] In the third embodiment configured as described above, when the perturbation body 4 is displaced from a predetermined position, the displacement can be detected by the displacement measuring device 7. And when there is no displacement of the perturbation body 4, the measurement error can be suppressed by measuring the frequency or phase for conversion into the electric field distribution only.

[0030] (Fourth Embodiment) Next, the fourth embodiment will be described with reference to FIG. 4.

[0031] In the fourth embodiment, the displacement information acquired by the displacement measuring device 7 is input as a trigger signal to the frequency measuring device 9. When displacement occurs, the recording is stopped, and recording is performed only when there is no displacement. Depending on the signal input mode of the frequency measuring device 9, the trigger signal is inverted and used by using a NOT circuit. Alternatively, as the frequency measuring device 9, it is combined with a recording device such as a network analyzer, a logger, and an oscilloscope to synchronize and record the displacement signal as data.

[0032] In the fourth embodiment configured as described above, when the perturbation body 4 is displaced from a predetermined position, the displacement can be detected by the displacement measuring device 7, and the frequency and phase, which are the electric field data, can be synchronously recorded. In this way, the position displacement of the perturbation body 4 is detected, the measurement is automatically performed only when there is no displacement, and the measurement error can be suppressed.

[0033] Furthermore, in the fourth embodiment, by detecting the position displacement of the perturbation body 4 and recording it in synchronization with the frequency and phase which are the electric field data, only the data without displacement is extracted in the post-measurement data processing, thereby constructing the electric field distribution only with the data points without displacement and suppressing the measurement error.

[0034] (Fifth Embodiment) Next, the fifth embodiment will be described with reference to FIG. 5. Note that the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0035] In the fifth embodiment, as shown in FIG. 5, the support member 2 is configured in a loop shape using the support member fixture 3. Further, based on the displacement information obtained by the displacement measuring device 7, the tension of the support member 2 is adjusted by the tension adjusting means until the displacement disappears. As the tension adjusting means, those that electrically drive the support member fixture 3 to change the loop length to adjust the tension of the support member 2, or those that apply an additional load to the weight 6 to adjust the tension of the support member 2, etc. can be used. As the additional load, there are methods such as changing the weight of the weight 6 by an electric arm.

[0036] In the fifth embodiment configured as described above, when the perturbation body 4 is displaced from a predetermined position, after the displacement is detected by the displacement measuring device 7, the tension of the support member 2 is adjusted to eliminate the displacement. In this way, by automatically eliminating the position displacement of the perturbation body 4, measurement can be performed with an optimal tension without manual adjustment, and measurement error can be suppressed and measurement can be performed automatically.

[0037] (Sixth Embodiment) Next, the sixth embodiment will be described with reference to FIG. 6. Note that the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0038] In the sixth embodiment, as shown in FIG. 6, a control device 10 is connected to the drive device 5 and the frequency measuring device 9. As the control device 10, a personal computer (PC), a programmable logic unit (PLC), a motor driver, a motor controller, etc. are used as necessary. Further, a measurement signal from the displacement measuring device 7 is input to the control device 10.

[0039] Using the control device 10, the drive device 5 and the frequency measuring device 9 are operated in conjunction. First, the entire area to be measured is conveyed, and the tension is adjusted so that no position displacement of the perturbation body 4 occurs in the entire area. After the exploration of the entire area is completed, the measurement area is conveyed again under the same tension setting, and the frequency and phase, which are the electric field distribution data, are recorded. If displacement is recorded during conveyance due to changes over time of the support material 2 or the like, the tension is adjusted again, and the entire area is conveyed and the data is recorded. Thereafter, the adjustment and measurement are repeated until recording can be performed without adjusting the tension even once in the entire area to be measured. As the tension adjusting means for adjusting the tension of the support material 2, for example, adjustment of the weight 6 or a method of electrically driving the support fixture 3 and changing the loop length as in the fifth embodiment shown in FIG. 5 can be used.

[0040] In the sixth embodiment configured as described above, it is possible to record data without adjusting the tension even once in the entire measurement area of the acceleration cavity 1. That is, in the entire measurement area of the acceleration cavity 1, it is possible to obtain electric field data with a uniform tension setting and without any position displacement of the perturbation body 4, and it is possible to suppress measurement errors caused by changes in tension and position displacement of the perturbation body 4.

[0041] As described above, some embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0042] 1... Accelerating cavity, 2... Support member, 3... Support member fixture, 4... Perturbation body, 5... Driving device, 6... Weight, 7... Displacement measuring device, 8... Antenna, 9... Frequency measuring instrument, 10... Control device.

Claims

1. An electric field measuring device for measuring the electric field in an accelerating cavity, comprising: A perturbation body disposed in the accelerating cavity for perturbing the electric field; A support member disposed along the axial direction in the accelerating cavity for supporting the perturbation body; A drive mechanism for driving the support member to move the perturbation body; Electric field measuring means for measuring the electric field in the accelerating cavity; Displacement measuring means for detecting the vertical displacement of the perturbation body from a reference position in the accelerating cavity; Comprising: The electric field measuring device, characterized in that the displacement measuring means comprises tension detecting means for detecting the tension of the support member.

2. An electric field measuring device for measuring the electric field in an accelerating cavity, comprising: A perturbation body disposed in the accelerating cavity for perturbing the electric field; A support member disposed along the axial direction in the accelerating cavity for supporting the perturbation body; A drive mechanism for driving the support member to move the perturbation body; Electric field measuring means for measuring the electric field in the accelerating cavity; Displacement measuring means for detecting the vertical displacement of the perturbation body from a reference position in the accelerating cavity; Comprising: The electric field measuring device, characterized in that the displacement measuring means measures the load applied to the perturbation body.

3. An electric field measuring device for measuring the electric field in an accelerating cavity, comprising: A perturbation body disposed in the accelerating cavity for perturbing the electric field; A support member disposed along the axial direction in the accelerating cavity for supporting the perturbation body; A drive mechanism for driving the support member to move the perturbation body; Electric field measuring means for measuring the electric field in the accelerating cavity; Displacement measuring means for detecting the vertical displacement of the perturbation body from a reference position in the accelerating cavity; Comprising: The electric field measuring device, characterized in that the displacement measuring means irradiates electromagnetic waves to the perturbation body and detects the displacement from the response of the electromagnetic waves.

4. An electric field measuring device for measuring the electric field in an accelerating cavity, comprising: A perturbation body disposed in the accelerating cavity for perturbing the electric field; A support member disposed along the axial direction in the accelerating cavity for supporting the perturbation body; A drive mechanism for driving the support member to move the perturbation body; Electric field measuring means for measuring the electric field in the accelerating cavity; Displacement measuring means for detecting the vertical displacement of the perturbation body from a reference position in the accelerating cavity; Comprising: The electric field measuring device, characterized in that the displacement measuring means captures the reflected light from the perturbation body and detects the displacement from the video or image thereof.

5. An electric field measuring device for measuring an electric field in an accelerating cavity, comprising: a perturbing body disposed in the accelerating cavity for perturbing the electric field; a support member disposed along the axial direction in the accelerating cavity for supporting the perturbing body; a driving mechanism for driving the support member to move the perturbing body; an electric field measuring means for measuring the electric field in the accelerating cavity; a displacement measuring means for detecting a vertical displacement of the perturbing body from a reference position in the accelerating cavity; characterized in that when the displacement measuring means detects a displacement of the perturbing body from the reference position, the electric field measuring device has a tension adjusting means for adjusting the tension of the support member for fixing the perturbing body until the displacement disappears.

6. The driving mechanism drives the perturbing body across the entire measurement region to adjust the tension of the support member by the tension adjusting means, and thereafter, the perturbing body is driven again across the entire measurement region, and a control device is provided for controlling the measurement of the electric field by the electric field measuring means. The electric field measuring device according to claim 5, characterized in that.

7. The electric field measuring means comprises an antenna for frequency measurement inserted into the accelerating cavity and a frequency measuring device connected to the antenna. The electric field measuring device according to any one of claims 1 to 6, characterized in that.

8. The electric field measuring means comprises an antenna for frequency measurement inserted into the accelerating cavity and a frequency measuring device connected to the antenna, when the displacement measuring means detects a displacement of the perturbing body from the reference position, a displacement signal is output to the frequency measuring device, and the frequency measuring device stops acquiring a frequency measurement signal when the displacement signal is input. The electric field measuring device according to any one of claims 1 to 4, characterized in that.

9. The electric field measuring means comprises an antenna for frequency measurement inserted into the accelerating cavity and a frequency measuring device connected to the antenna, and the displacement information of the perturbing body from the reference position by the displacement measuring means and the measurement signal by the frequency measuring device are measured simultaneously. The electric field measuring device according to any one of claims 1 to 4, characterized in that.

10. An electric field measuring method for measuring an electric field in an accelerating cavity, characterized in that the electric field is measured using the electric field measuring device according to any one of claims 1 to 9.

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