JP7717586B2 - Electric field measuring device and electric field measuring method - Google Patents

Description

Embodiments of the present invention relate to an electric field measurement device and an electric field measurement method.

In accelerating cavities, such as linear accelerators (e.g., radio frequency quadrupole linacs (RFQs) and drift tube linacs (DTLs)), electric field measurements are generally performed to compare the electric field distribution of the fabricated cavity with the design value. A known method for measuring the electric field is the perturbation (bead-pull) method, in which a small dielectric or metallic perturber is inserted into the accelerating cavity to perturb the electric field, and the electric field is measured from changes in the resonant frequency. Specifically, the perturber is held by a string and moved within the accelerating cavity, and the frequency at each point in the axial direction is measured and converted into the electric field distribution (see, for example, Patent Document 1).

In the electric field measurements described above, the perturber must be held in a predetermined position. The weight of the perturber causes sagging in the string holding the perturber, and if it shifts vertically, the perturbation will occur at a different position from its intended position, resulting in errors in the acquired electric field distribution.

Such errors become particularly noticeable when the beam duct has a large diameter and measurements are being performed over a wide range, or when the size of the antenna for frequency measurement is limited due to constraints on the internal structure of the accelerating cavity, and the weight increases as the size of the perturbation body is increased to maintain signal strength.

In addition, because measurements are performed over a wide range, the string deforms over long periods of time, and the string tension set at the beginning of the measurement may not be sufficient. Furthermore, if the displacement of the perturbation body's position is measured using a method that mechanically contacts the perturbation body, the frequency fluctuates significantly, making it impossible to measure the electric field distribution. With conventional methods, the position of the perturbation body is determined only by the string's support structure, and any displacement of the perturbation body's position that occurs inside the accelerating cavity appears as an error in the measured electric field distribution.

Patent No. 6625915

As mentioned above, conventional electric field measurement devices and methods have the problem that errors occur when measuring the electric field inside the accelerating cavity, making it impossible to measure the electric field with high precision.

The present invention has been made to solve the above-mentioned problems, and aims to provide an electric field measurement device and electric field measurement method that can measure the electric field with higher accuracy when placing a perturbation body inside an accelerating cavity to measure the electric field.

An electric field measuring device according to an embodiment is an electric field measuring device for measuring an electric field within an accelerating cavity, and includes a perturber disposed within the accelerating cavity for perturbing the electric field, a support member disposed along the axial direction within the accelerating cavity for supporting the perturber, a drive mechanism for driving the support member to move the perturber, electric field measuring means for measuring the electric field within the accelerating cavity, and displacement measuring means for detecting the displacement of the perturber from a reference position.

Embodiments of the present invention provide an electric field measurement device and an electric field measurement method that can measure the electric field with higher accuracy when placing a perturbation body inside an accelerating cavity to measure the electric field.

FIG. 1 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a first embodiment. FIG. 10 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a second embodiment. FIG. 10 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a third embodiment. FIG. 10 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a fourth embodiment. FIG. 10 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a fifth embodiment. FIG. 13 is a diagram schematically showing a vertical cross-sectional configuration of an electric field measuring device according to a sixth embodiment.

The electric field measurement device and electric field measurement method according to the embodiment will be described below with reference to the drawings.

(First embodiment)
First, a first embodiment will be described with reference to FIG. 1 . In this first embodiment, an acceleration cavity 1 is the measurement target. Specific examples of the acceleration cavity 1 include a simple pillbox cavity, as well as 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 radio frequency acceleration cavities. Furthermore, the target cavity may be any cavity that changes the behavior of charged particle motion by applying radio frequency power, such as a buncher or debuncher.

The support material 2 is placed inside the acceleration cavity 1 along its axial direction. The support material 2 is supported by a support material fixture 3. The support material 2 is preferably made of a thin material with a small mass, such as thread or wire. Fishing line made of nylon, fluorocarbon, polyethylene, etc. can be used.

The support material fixture 3 is used to fix the position of the support material 2 inside the acceleration cavity 1. The support material fixture 3 can be shaped like a pulley, allowing the part in contact with the support material 2 to rotate, allowing smooth movement of the support material 2, or it can be shaped like a nylon plate with holes or notches through which the support material 2 can pass. In either case, it is desirable to apply a rounded finish to the part of the support material fixture 3 that comes into contact with the support material 2, to prevent damage to the support material 2.

A perturbator 4 is connected to the support material 2. The shape of the perturbator 4 is preferably a symmetrical shape such as a sphere, cylinder, or rectangular parallelepiped. Possible materials for the perturbator 4 include dielectrics, such as nylon, acrylic, and other materials with excellent workability, as well as ceramics with high dielectric constants such as barium titanate, silicon nitride, and alumina. The higher the dielectric constant, the greater the electric field perturbation for the same volume, improving the S/N ratio. Metals can also be used instead of dielectrics, in which case aluminum, which has a light specific gravity, is suitable.

A drive unit 5 is connected to the support material 2. The drive unit 5 uses, for example, a motor to drive the support material 2, thereby transporting the perturber 4 inside the acceleration cavity 1 and changing the measurement position. In addition to measuring the electric field while continuously transporting the perturber 4 using an induction motor or the like, it is also possible to stop the perturber 4 at a specific position and perform measurements using a servo motor, stepping motor, or the like.

A weight 6 is also connected to the support material 2 to generate tension so that the perturber 4 does not sag due to its own weight. The weight 6 can be configured by using the weight itself, or by generating tension using a motor-controlled arm. A displacement measuring device 7 is also provided to detect any sagging and displacement of the perturber 4. There are no particular restrictions on the displacement measuring device 7, as long as it can detect the displacement of the perturber 4 from a predetermined position. The accuracy of displacement detection in this case varies depending on the specifications of the accelerating cavity 1 and the perturber 4 used, the high-frequency power used to accelerate the charged particles, and other factors, but is typically on the order of 1 to several millimeters.

As one example, the displacement measuring device 7 can be a device that measures the tension or load applied to the perturbation body 4. For example, a contact-type (mechanical) tension meter can be used as the displacement measuring device 7, which comes into contact with the support material 2 to measure its tension. Alternatively, an ultrasonic tension meter or trance tension meter can be used as the displacement measuring device 7 to measure the tension from the vibration frequency or sound waves of the support material 2 or perturbation body 4 in a non-contact manner. Furthermore, a load measuring meter can also 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 deviates from its original value, this can be detected as a displacement of the perturbation body 4.

An antenna 8 for frequency measurement is placed in the accelerating cavity 1. The structure of the antenna 8 is, for example, a loop made of a rod-shaped metal such as copper or stainless steel connected to the vacuum side of a feedthrough flange with a vacuum-sealable lead-in terminal. The shape of the loop can be circular, elliptical, rectangular, or a combination of these.

A frequency measuring device 9 is connected to the antenna 8 via a cable. A network analyzer or similar device can be used as the frequency measuring device 9. The cable can be a coaxial cable with a BNC connector, N connector, SMA connector, or similar. In addition to connecting one antenna 8 between the accelerating cavity 1 and the frequency measuring device 9 to perform absorption measurements, two antennas 8 can also be used to perform two-channel transmission measurements.

In the first embodiment configured in this manner, the perturbation of the electric field inside the accelerating cavity 1 caused by the perturber 4 can be measured as a change in frequency or phase using the frequency measuring device 9. Therefore, by combining it with the displacement measuring device 7, measurement errors can be reduced by measuring the frequency or phase for conversion into an electric field distribution only when no displacement of the perturber 4 is occurring.

Second Embodiment
Next, a second embodiment will be described with reference to Fig. 2. Note that the same components as those in the first embodiment shown in Fig. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the second embodiment, a device that emits electromagnetic waves is used as the displacement measurement device 7. For example, a laser rangefinder or a reflective laser sensor is installed outside the accelerating cavity 1 as the displacement measurement device 7, and emits a laser toward the perturber 4.

In this case, for example, if no displacement occurs in the position of the perturber 4 and it remains in a predetermined position, the laser is not detected, and the displacement measuring device 7 is fixed in a position and orientation where the laser is detected only when displacement occurs. Alternatively, as shown in Figure 2, a transmission-type laser sensor that is separated into an electromagnetic wave emitting device and a detecting side is used, and the emitting device is installed outside the accelerating cavity 1, and the detecting side is installed at the other end of the accelerating cavity 1. If the perturber 4 remains in a predetermined position, the laser is detected on the detecting side, and only when displacement of the perturber 4 occurs are the emitting device and the detecting side fixed in a position and orientation where the laser is not detected. Lenses, filters, mirrors, etc. can be placed between the displacement measuring device 7 and the perturber 4 as needed, and the displacement measuring device 7 and the perturber 4 do not need to be placed in a straight line.

In the second embodiment configured in this manner, when the perturbation body 4 is displaced from a predetermined position, the displacement can be detected by the displacement measuring device 7. Then, measurement errors can be reduced by measuring the frequency or phase for conversion into an electric field distribution only when the perturbation body 4 is not displaced.

(Third embodiment)
Next, a third embodiment will be described with reference to Fig. 3. Note that the same components as those in the first embodiment shown in Fig. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the third embodiment, the displacement measuring device 7 uses an imaging device for capturing light reflected from the perturbation body 4. Specifically, a camera or video camera is installed with its imaging direction facing the perturbation body 4. Lenses, filters, mirrors, etc. are placed on the light path as needed. The position of the perturbation body 4 is photographed and recorded in conjunction with the transport of the perturbation body 4. The position of the perturbation body 4 is estimated based on the image data of the recorded video or image.

In the third embodiment configured in this manner, when the perturbation body 4 is displaced from a predetermined position, the displacement can be detected by the displacement measuring device 7. Then, measurement errors can be reduced by measuring the frequency or phase for conversion into an electric field distribution only when no displacement of the perturbation body 4 occurs.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG.

In the fourth embodiment, the displacement information acquired by the displacement measuring device 7 is input to the frequency measuring device 9 as a trigger signal, and recording is stopped when displacement occurs and continues only when no displacement occurs. The trigger signal is inverted using a NOT circuit depending on the signal input format of the frequency measuring device 9. Alternatively, the frequency measuring device 9 is combined with a network analyzer and a recording device such as a logger or oscilloscope, and the displacement signal is synchronized and recorded as data.

In the fourth embodiment configured in this manner, when the perturber 4 is displaced from its predetermined position, the displacement measuring device 7 detects the displacement and synchronously records the electric field data, which are frequency and phase. In this way, the positional displacement of the perturber 4 is detected and measurements are automatically performed only when there is no displacement, thereby reducing measurement errors.

Furthermore, in the fourth embodiment, the positional displacement of the perturber 4 is detected and recorded in synchronization with the frequency and phase of the electric field data. By extracting only data in which no displacement has occurred during data processing after measurement, an electric field distribution can be constructed using only data points in which no displacement has occurred, thereby reducing measurement errors.

Fifth Embodiment
Next, a 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 description will be omitted.

In the fifth embodiment, as shown in Figure 5, the support material 2 is configured into a loop shape using a support material fixture 3. Furthermore, based on the displacement information obtained by the displacement measuring device 7, the tension of the support material 2 is adjusted by a tension adjustment means until the displacement disappears. As a tension adjustment means, a means can be used that electrically drives the support material fixture 3 and changes the loop length to adjust the tension of the support material 2, or a means that adjusts the tension of the support material 2 by adding an additional load to the weight 6. One method of adding an additional load is to change the weight of the weight 6 using an electric arm.

In the fifth embodiment configured in this manner, when the perturber 4 is displaced from its predetermined position, the displacement is detected by the displacement measuring device 7, and the tension of the support material 2 is then adjusted to eliminate the displacement. In this way, by automatically eliminating the positional displacement of the perturber 4, measurements can be performed at the optimal tension without manual adjustment, reducing measurement errors and enabling automatic measurements.

Sixth Embodiment
Next, a 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 description will be omitted.

In the sixth embodiment, as shown in FIG. 6, a control device 10 is connected to the drive device 5 and frequency measuring device 9. The control device 10 may be a personal computer (PC) or a programmable logic unit (PLC), and, if necessary, a motor driver, motor controller, etc. In addition, a measurement signal from the displacement measuring device 7 is input to the control device 10.

The drive unit 5 and frequency measuring device 9 are operated in conjunction with the control device 10. First, the entire area of the measurement target is transported, and the tension is adjusted so that no positional displacement of the perturber 4 occurs throughout the entire area. After the entire area has been explored, the measurement area is transported again under the same tension setting, and electric field distribution data, such as frequency and phase, is recorded. If displacement is recorded during transport due to changes in the support material 2 over time, for example, the tension is adjusted again, and the entire area is transported and data is recorded. Thereafter, adjustment and measurement are repeated until data can be recorded throughout the entire area of the measurement target without any tension adjustment. The tension adjustment means for adjusting the tension of the support material 2 can be, for example, adjustment of the weight 6, or, as in the fifth embodiment shown in Figure 5, a method of electrically driving the support material fixture 3 and changing the loop length, etc.

In the sixth embodiment configured in this way, data can be recorded without any tension adjustments being made across the entire measurement region of the accelerating cavity 1. In other words, electric field data can be obtained with a uniform tension setting and no positional displacement of the perturbation body 4 across the entire measurement region of the accelerating cavity 1, thereby minimizing measurement errors caused by changes in tension and positional displacement of the perturbation body 4.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, modifications, and combinations may be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

1...Acceleration cavity, 2...Support, 3...Support fixture, 4...Perturber, 5...Driver, 6...Weight, 7...Displacement measuring device, 8...Antenna, 9...Frequency measuring device, 10...Control device.

Claims (10)

An electric field measuring device for measuring an electric field in an accelerating cavity, comprising:
a perturbation body disposed within the accelerating cavity for perturbing the electric field;
a support member disposed along the axial direction within the acceleration cavity and supporting the perturbation body;
a drive mechanism that drives the support member to move the perturbation body;
an electric field measuring means for measuring an electric field within the accelerating cavity;
a displacement measuring means for detecting a vertical displacement of the perturbation body from a reference position within the accelerating cavity;
Equipped with
10. An electric field measuring device, wherein the displacement measuring means comprises tension detecting means for detecting the tension of the support material. An electric field measuring device for measuring an electric field in an accelerating cavity, comprising:
a perturbation body disposed within the accelerating cavity for perturbing the electric field;
a support member disposed along the axial direction within the acceleration cavity and supporting the perturbation body;
a drive mechanism that drives the support member to move the perturbation body;
an electric field measuring means for measuring an electric field within the accelerating cavity;
a displacement measuring means for detecting a vertical displacement of the perturbation body from a reference position within the accelerating cavity;
Equipped with
10. An electric field measuring device, wherein the displacement measuring means measures a load applied to the perturbation body. An electric field measuring device for measuring an electric field in an accelerating cavity, comprising:
a perturbation body disposed within the accelerating cavity for perturbing the electric field;
a support member disposed along the axial direction within the acceleration cavity and supporting the perturbation body;
a drive mechanism that drives the support member to move the perturbation body;
an electric field measuring means for measuring an electric field within the accelerating cavity;
a displacement measuring means for detecting a vertical displacement of the perturbation body from a reference position within the accelerating cavity;
Equipped with
10. An electric field measuring device, wherein the displacement measuring means irradiates the perturbing body with an electromagnetic wave and detects the displacement from the response of the electromagnetic wave. An electric field measuring device for measuring an electric field in an accelerating cavity, comprising:
a perturbation body disposed within the accelerating cavity for perturbing the electric field;
a support member disposed along the axial direction within the acceleration cavity and supporting the perturbation body;
a drive mechanism that drives the support member to move the perturbation body;
an electric field measuring means for measuring an electric field within the accelerating cavity;
a displacement measuring means for detecting a vertical displacement of the perturbation body from a reference position within the accelerating cavity;
Equipped with
An electric field measuring device characterized in that the displacement measuring means photographs the light reflected from the perturbation body and detects the displacement from the video or image. An electric field measuring device for measuring an electric field in an accelerating cavity, comprising:
a perturbation body disposed within the accelerating cavity for perturbing the electric field;
a support member disposed along the axial direction within the acceleration cavity and supporting the perturbation body;
a drive mechanism that drives the support member to move the perturbation body;
an electric field measuring means for measuring an electric field within the accelerating cavity;
a displacement measuring means for detecting a vertical displacement of the perturbation body from a reference position within the accelerating cavity;
Equipped with
An electric field measuring device characterized in that the displacement measuring means has a tension adjusting means for adjusting the tension of the support material fixing the perturbation body until the displacement disappears when the displacement measuring means detects a displacement of the perturbation body from a reference position. the driving mechanism drives the perturbation body over the entire measurement region, and the tension of the support material is adjusted by the tension adjusting means;
6. The electric field measuring device according to claim 5, further comprising a control device that controls the perturbation body to be driven again over the entire measurement region after the measurement and measure the electric field by the electric field measuring means. The electric field measuring means
7. The electric field measuring device according to claim 1, further comprising: an antenna for measuring a frequency inserted into the acceleration cavity; and a frequency measuring device connected to the antenna. the electric field measuring means comprises an antenna for measuring a frequency inserted into the acceleration cavity, and a frequency measuring device connected to the antenna;
when the displacement measuring means detects a displacement of the perturbation body from a reference position, the displacement measuring means outputs a displacement signal to the frequency measuring device;
5. The electric field measuring device according to claim 1, wherein the frequency measuring device stops acquiring the frequency measuring signal when the displacement signal is input. the electric field measuring means comprises an antenna for measuring a frequency inserted into the acceleration cavity, and a frequency measuring device connected to the antenna;
5. The electric field measuring device according to claim 1, wherein the displacement information of the perturbation body from a reference position measured by the displacement measuring means and the measurement signal measured by the frequency measuring device are measured simultaneously. 1. An electric field measurement method for measuring an electric field in an accelerating cavity, comprising:
An electric field measuring method, comprising measuring an electric field using the electric field measuring device according to any one of claims 1 to 9.