JP2001126900A - High frequency acceleration cavity and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency acceleration cavity that the Q factor can be regulated as desired, reducing beam loading and the ion beam can be accelerated uniformly, and to provide a control method of the same. SOLUTION: The high frequency acceleration cavity has a vacuum duct 1A and 1B, and a magnetic core 2A and 2B divided into two surrounding the vacuum duct 1a in a concentric circle in the outer periphery of this vacuum duct, and an outside cover 3 to contain the vacuum duct 1A and 1B, and the magnetic core 2A and 2B. The vacuum duct 1A and 1B have a predetermined gap 5, and they are connected with a ring 4 consisting of ceramic material to being each longitudinal central axis in line. And the distance W between the magnetic core 2A and 2B are adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-frequency acceleration cavity and a method of controlling the high-frequency acceleration cavity.
The present invention relates to a high-frequency acceleration cavity and a method for controlling the high-frequency acceleration cavity that can be suitably used in a high-intensity, high-energy ion accelerator or the like.

[0002]

2. Description of the Related Art At present, high-intensity, high-energy ion accelerators are required to accelerate ions to a high energy region of several GeV to several thousand GeV. On the other hand, a circular accelerator is preferably used as a high-intensity and high-energy ion accelerator as described above because it can stably accelerate a circulating ion beam.

In a circular accelerator, acceleration of an ion beam is mainly performed by a high-frequency acceleration cavity constituting the accelerator. The high-frequency accelerating cavity has a vacuum duct having a predetermined gap, and by applying high-frequency power synchronized with a circulation cycle of the ion beam passing through the vacuum duct to the gap, the ion beam is applied to the ion beam. A high frequency voltage is applied to accelerate the ion beam. In accelerating the ion beam, since the high-frequency acceleration cavity is an essential high-frequency resonator, the energy of the magnetic field and the energy of the electric field are synchronized with the input high-frequency power in the cavity. Are alternately converted, and the ion beam is accelerated by applying electric field energy to the ion beam.

The energy range where the effect of relativity is weak (10
In GeV), an external force is applied to the ion beam to increase the speed of the ion beam.
The time to orbit the circular accelerator changes. Therefore,
The high-frequency voltage synchronized with the cycle of the ion beam rotation as described above is applied to the gap to accelerate the ion beam.

[0005] In the high-frequency acceleration cavity for an ion beam as described above, a bias current is applied to a magnetic core mounted in the cavity to change the magnetic flux density in the core. By adjusting the inductance, the resonance frequency in the cavity can be controlled. Therefore, even when the input high frequency fluctuates, by controlling the resonance frequency, the ion beam can be accelerated in synchronization with the circulation cycle of the ion beam. Such a high-frequency accelerating cavity
It is generally called a tuned high-frequency accelerating cavity.

[0006]

Ferrite is mainly used for the magnetic core of the tunable high-frequency acceleration cavity.
When the magnetic core is made of ferrite, when the magnetic flux density in the magnetic core is small (10 Gauss or less), the magnetic core has a short impedance (loss resistance) R = V ² / 2P large enough to withstand use.
(V: peak gap voltage, P: power supplied to the high-frequency accelerating cavity by the high-frequency power supply). However, when the magnetic flux density becomes large (more than 100 Gauss),
The shunt impedance of the magnetic core becomes small. For this reason, the magnetic core as described above has a practical magnetic flux density limit, and the acceleration voltage also has a limit.

From this point of view, a non-tunable accelerating cavity having a magnetic core having a wide bandwidth and high-frequency characteristics tunable to an ion beam and removing a mechanism for applying a bias current has been developed and put into practical use. . FIG. 1 is a diagram showing an example of such a non-tuned high-frequency acceleration cavity. FIG.
(A) is a figure which shows the cross section at the time of cutting | disconnecting a non-tuning type high frequency acceleration cavity along the longitudinal direction, FIG.
Shows the tunable high-frequency accelerating cavity shown in FIG.
By cutting along the line A, the sectional shape of the magnetic core is shown.

A tuned high-frequency accelerating cavity 10 shown in FIG.
Is a vacuum duct 1A and 1B, a magnetic core 2 concentrically surrounding the vacuum duct 1A at the outer periphery of the vacuum duct 1A, and an outer cover 3 for accommodating the vacuum ducts 1A and 1B and the magnetic core 2. It has. And
The vacuum ducts 1A and 1B are connected with a gap 5 by a ring 4 made of a ceramic material. Further, flanges 6A and 6B are fixed to one ends of the vacuum ducts 1A and 1B, respectively, and are configured to be connectable to other vacuum ducts.

The vacuum ducts 1A and 1B, the outer cover 3, and the ring 4 constitute a λ / 4 resonator. High-frequency power (high-frequency voltage) is applied to the gap 5 from a high-frequency power supply 7, thereby accelerating an ion beam passing through the vacuum ducts 1A and 1B. The magnetic core 2 is a continuous body as shown in FIG. 1B, and a magnetic field is induced inside the core so as to wind a vacuum duct. Then, even if the frequency of the input high frequency fluctuates, a high-frequency voltage corresponding to the fluctuation is formed in the gap portion of the vacuum duct, so that the ion beam can always be accelerated uniformly.

In recent years, magnetic cores 2
Research using A core (Magnetic Alloy core) is in progress. A tunable high-frequency accelerating cavity with a large accelerating voltage is realized by using an MA core having almost uniform characteristics without deteriorating the shunt impedance even for a large magnetic flux density in the core exceeding 100 Gauss. Have been.

Such an untuned high-frequency accelerating cavity has an inherently small Q value (ratio of resonance width to resonance frequency).
have. However, if the Q value is small, the index R / Q value indicating the effect (beam loading) of the ion beam on the high-frequency acceleration cavity becomes large. When the beam loading becomes large, unfavorable effects for the circular accelerator appear such as instability of the ion beam. Therefore, it is preferable that the Q value be as large as the bandwidth allows. In addition, R /
By lowering the Q value, operation at a higher frequency becomes possible, and the frequency range of the high-frequency acceleration cavity can be expanded.

However, in the conventional non-tuned high-frequency accelerating cavity as shown in FIG. 1, the Q value is determined by the characteristics of the selected magnetic core and the like, and is required from the specifications of the entire accelerator. It has been extremely difficult to achieve an optimal Q value.

According to the present invention, there is provided a high frequency accelerating cavity capable of arbitrarily adjusting a Q value, thereby reducing beam loading and uniformly accelerating an ion beam.
And a method for controlling a high-frequency accelerating cavity.

[0014]

In order to achieve the above object, a high-frequency accelerating cavity according to the present invention has a plurality of vacuum ducts, and the vacuum ducts are concentrically formed on at least one outer peripheral portion of the plurality of vacuum ducts. An enclosing magnetic core, and an outer cover for accommodating the plurality of vacuum ducts and the magnetic core. The plurality of vacuum ducts have a predetermined gap and are connected by a ring made of a ceramic material such that their central axes in the longitudinal direction coincide with each other. Further, the ion beam passing through the plurality of vacuum ducts is configured to resonate and accelerate with a high-frequency electric field generated in the gap. The magnetic core is divided into a plurality of parts.

Further, in the method of controlling a high-frequency acceleration cavity according to the present invention, in the high-frequency acceleration cavity according to the present invention as described above, the ion beam is accelerated by adjusting an interval between divided surfaces of the magnetic core. The state is adjusted.

The present inventors have intensively studied to achieve the above object. As a result, it was surprisingly found that the Q value changes by dividing the magnetic core by a plane including the central axis, that is, by dividing the magnetic core into a plurality in the longitudinal direction of the magnetic core. And
It has been found that the Q value can be set to an arbitrary value irrespective of the material of the magnetic core by adjusting the interval between the divided surfaces. Therefore, by obtaining a desired Q value, beam loading can be sufficiently reduced, and the ion beam can be stably accelerated, and the ion beam can be accelerated at a higher frequency. Also,
The range of choices for the material of the magnetic core is widened, and a higher magnetic flux density than before can be obtained. Therefore, the acceleration voltage of the ion beam can be further improved.

As described above, the Q value changes by dividing the magnetic core into a plurality, and the Q value can be set to an arbitrary value by adjusting the interval between the divided surfaces of the magnetic core. The reason can be inferred as follows. Most of the power supplied to the high-frequency acceleration cavity is consumed by the magnetic material in the high-frequency acceleration cavity. That is, the energy consumption of the high-frequency acceleration cavity is determined by the volume of the magnetic core. On the other hand, when the magnetic core is divided along a plane including the central axis, the magnetic path is divided at such a portion, and the continuity of the magnetic permeability is lost, so that the magnetic resistance increases and the stored energy increases. That is, even if the magnetic core is separated as described above, the volume of the magnetic core remains constant, so that the consumed energy takes a substantially constant value. On the other hand, the stored energy can be changed to an arbitrary value by appropriately adjusting the distance between the division planes. From the definition, the Q value of the high-frequency accelerating cavity is given by the ratio of stored energy to consumed energy per unit time. Therefore, the Q value can be changed to an arbitrary value by the energy change due to the separation of the magnetic core.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments of the present invention. FIG. 2 is a diagram showing an example of the high-frequency acceleration cavity of the present invention. FIG. 2A is a diagram showing a cross section in the longitudinal direction of the high-frequency acceleration cavity, and FIG.
2B is a cross-sectional view of the magnetic core shown in FIG. 2A taken along line AA. The high-frequency acceleration cavity 20 of the present invention shown in FIG. 2 has basically the same configuration as the conventional high-frequency acceleration cavity 10 shown in FIG. Therefore, similar parts are denoted by the same reference numerals.

The high frequency accelerating cavity 20 of the present invention shown in FIG.
Has magnetic cores 2A and 2B divided into two along a plane including the central axis. That is, the high-frequency accelerating cavity 20 shown in FIG. 2 constitutes a single magnetic core with a set of two divided magnetic cores. The magnetic core constituting the high-frequency accelerating cavity need not necessarily be divided into two as shown in FIG. 2, and the number is not limited as long as it is divided into a plurality. However, as shown in FIG. 2, the desired Q value can be easily obtained by dividing the magnetic core into two and adjusting the interval between the divided surfaces. Further, when the magnetic core is divided into three or more, the means for holding the magnetic material becomes complicated, and the operation for adjusting the interval between the divided surfaces tends to be complicated. Therefore,
The magnetic core is preferably divided into two as shown in FIG.

In the case of the high-frequency accelerating cavity shown in FIG. 2, the interval between the divided surfaces of the magnetic core, that is, the magnetic cores 2A and 2A
The distance W from B is preferably in the range of 0 to several tens cm. As a result, the Q value can be changed, for example, in the range of 1 to several tens, and the beam loading can be extremely reduced even when the magnetic core is made of any material. The magnetic core 2
When the interval W between A and 2B is 0, it means that the divided surfaces of the magnetic cores 2A and 2B are in contact with each other.

FIG. 3 is a diagram showing another example of the high-frequency acceleration cavity of the present invention. 1A and 1B, FIG. 3A is a longitudinal sectional view, and FIG. 3B is a sectional view of FIG.
It is cut along the -A line to show the cross-sectional shape of the magnetic core. 3, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals. The high frequency accelerating cavity 30 of the present invention shown in FIG.
The magnetic cores 2A, 2B and 12A, 12B concentrically surround the outer peripheral portions of the vacuum ducts 1A and 1B, respectively, at the left and right symmetrical positions of a ring 4 made of a ceramic material connecting the two. And the magnetic core 2
A and 2B and 12A and 12B are paired with each other to constitute a magnetic core for each vacuum duct. Magnetic cores 2A, 2B and magnetic core 12
Each of A and 12B is obtained by dividing one magnetic core by a plane including its central axis, that is, in the longitudinal direction thereof.

A high-frequency accelerating cavity 3 having a structure as shown in FIG.
At 0, high-frequency voltages having opposite phases are applied to the vacuum ducts 1A and 1B from the high-frequency power supply 7 by a push-pull method, respectively, as compared with the case of the high-frequency acceleration cavity shown in FIGS. A double voltage can be generated in the gap 5. Therefore, in addition to the effects of the present invention described above, an additional effect that the ion beam can be accelerated more effectively can be obtained.

In the high-frequency accelerating cavity shown in FIG. 3, the number of magnetic cores surrounding the outer peripheral portions of the vacuum ducts 1A and 1B is not limited as long as the magnetic cores are each divided into a plurality. However, for the same reason as the high-frequency accelerating cavity shown in FIG. 2, it is preferable to divide the magnetic core surrounding each vacuum duct into two as shown in FIG.

FIG. 4 is a view showing a modification of the high-frequency acceleration cavity shown in FIG. FIG. 4A shows a longitudinal section of the high-frequency accelerating cavity, and FIG. 4B shows a magnetic core obtained by cutting the section shown in FIG. 4A along the line AA. FIG. In addition, about the part similar to FIGS. 1-3, it represents using the same code | symbol.
In the high-frequency accelerating cavity 40 shown in FIG. 4, a driving device 13A is provided below the magnetic cores 2B and 12B shown in FIG.
And 13B. Further, an interface 15 for converting monitor information such as the acceleration state of the ion beam, particularly the above-mentioned Q value, into an electric signal is provided. further,
Beam monitor panel 1 for arithmetically processing the electric signal
9 and a control device 17 for transmitting a control signal to the driving devices 13A and 13B based on the calculation result of the beam monitor panel 19. The control device 17 and the beam monitor panel 19 are provided with a high-frequency accelerating cavity 40 shown in FIG.
Of the control unit.

The high-frequency accelerating cavity 40 shown in FIG. 4 has a Q value which is a ratio of a resonance width to a resonance frequency of the cavity calculated from an acceleration state of the ion beam, in particular, a circulating frequency of the ion beam, an ion beam intensity, and the like. Is constantly monitored by a probe (not shown), and the monitor information is converted into an electric signal at the interface 15 and then transmitted to the beam monitor panel 19. Then, an arithmetic process based on the electric signal is performed in the beam monitor panel 19, and an electric signal for accelerating the ion beam in an optimum state is transmitted.

This electric signal is transmitted to the control device 17,
A control signal corresponding to the electric signal is transmitted from the control signal 17 to drive the driving devices 13A and 13B. The distance between the magnetic cores 2A and 2B and the distance between the magnetic cores 12A and 12B can be adjusted in real time during acceleration of the ion beam. Therefore, since the Q value of the high-frequency acceleration cavity can be controlled in real time, the acceleration state of the ion beam can always be maintained in a good state.

FIG. 5 is a schematic view of a circular accelerator including the high-frequency accelerating cavity of the present invention. A circular accelerator 50 shown in FIG. 5 includes a high-frequency accelerating cavity 51 according to the present invention for accelerating an ion beam and a bending electromagnet 52 for polarizing the ion beam so that the path of the ion beam is circular. And a converging / diverging electromagnet 54 for beam control. And between these, the vacuum duct 5
3, and the inside of the vacuum duct 53 is constantly evacuated by the vacuum pump 55 to maintain a high vacuum.

The circular accelerator 50 shown in FIG. 5 has the high-frequency accelerating cavity of the present invention. Therefore, irrespective of the type of material of the magnetic core that constitutes the high-frequency accelerating cavity, the optimum Q value required from the specifications of the entire accelerator is realized simply by dividing the magnetic core and changing the interval. Can be done. For this reason, stable ion beam acceleration is always possible.

[0029]

EXAMPLE In this example, a beam loading test using an electron beam was performed using a high-frequency accelerating cavity 20 as shown in FIG. Magnetic alloys or magnetic alloys were used for the magnetic cores 2A and 2B, and the distance W was varied as a parameter. The ring 4 was made of stainless steel, and the width d of the gap 5 was 20 mm. Then, the voltage induced in the gap 5 by the electron beam passing through the vacuum ducts 1A and 1B was observed while changing the interval W, that is, using the Q value as a parameter.
As a result, the index R / Q indicating the beam loading can be controlled by changing the interval W, and a system that is not affected by the beam loading can be realized.

As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and the present invention is not limited thereto. All modifications and changes are possible.

[0031]

As described above, according to the high-frequency accelerating cavity and the method of controlling the high-frequency accelerating cavity of the present invention, any type of material of the magnetic core constituting the high-frequency accelerating cavity can be used. Can be obtained. Therefore, the optimum Q value required from the specifications of the entire accelerator can be realized, and stable ion beam acceleration can be performed for a long time. Further, since the use bandwidth of the high-frequency acceleration cavity is increased, the ion beam can be accelerated at a higher frequency.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a conventional high-frequency acceleration cavity.

FIG. 2 is a diagram showing an example of a high-frequency acceleration cavity of the present invention.

FIG. 3 is a diagram showing another example of the high-frequency acceleration cavity of the present invention.

FIG. 4 is a view showing a modification of the high-frequency acceleration cavity shown in FIG. 3;

FIG. 5 is a diagram schematically showing a circular accelerator of the present invention.

[Explanation of symbols]

 1A, 1B, 53 Vacuum duct 2, 2A, 2B, 12A, 12B Magnetic core 3 Outer cover 4 Ring 5 Gap 6A, 6B Flange 7 High frequency power supply 13A, 13B Driving device 15 Interface 17 Control device 19 Beam monitor panel 10, 20 , 30, 40, 51 High-frequency accelerating cavity 50 Circular accelerator 52 Bending electromagnet 54 Converging / diverging electromagnet 55 Vacuum pump

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masato Yoshii 1-1-1, Oho, Tsukuba-shi, Ibaraki F-term in the High Energy Accelerator Research Organization Accelerator Research Facility (reference) 2G085 BA05 BA08 BA09 BB01 BC11 BE03 BE05 BE06 BE10 CA06 CA12 DA08

Claims (11)

[Claims] 1. A plurality of vacuum ducts, a magnetic core concentrically surrounding the vacuum duct on at least one outer peripheral portion of the plurality of vacuum ducts, and the plurality of vacuum ducts and the magnetic core are housed. An outer cover for the plurality of vacuum ducts, wherein the plurality of vacuum ducts have a predetermined gap and are connected by a ring made of a ceramic material so that their central axes in the longitudinal direction coincide with each other; A high-frequency accelerating cavity configured to resonate and accelerate an ion beam passing through the gap in a high-frequency electric field generated in the gap, wherein the magnetic core is divided into a plurality by a plane including a central axis thereof. Characterized by a high-frequency accelerating cavity. 2. The high-frequency accelerating cavity according to claim 1, wherein the magnetic core is divided into two parts by a plane including a center axis thereof. 3. The magnetic core comprises a plurality of magnetic cores which concentrically surround the outer peripheral portions of the plurality of vacuum ducts at positions symmetrical with respect to the ring, and wherein the plurality of magnetic cores are 2. The high-frequency accelerating cavity according to claim 1, wherein the cavity is divided into a plurality of parts by a plane including their central axes. 4. The high-frequency accelerating cavity according to claim 3, wherein the plurality of magnetic cores are each divided into two by a plane including their central axes. 5. The high-frequency device according to claim 1, further comprising a control unit configured to adjust an interval between divided surfaces of the magnetic core divided by the plane. Accelerating cavity. 6. The control unit calculates an optimum interval between the divided surfaces of the magnetic core from a ratio of a resonance width to a high-frequency acceleration cavity calculated from a circulation frequency of the ion beam and monitor information of the ion beam intensity. The high-frequency accelerating cavity according to claim 5, further comprising: a calculation unit that performs the operation, and a driving unit that drives the magnetic core to adjust the width of the division surface. 7. A circular accelerator comprising the high-frequency accelerating cavity according to claim 1. 8. A housing for accommodating a plurality of vacuum ducts, a magnetic core concentrically surrounding the vacuum duct in at least one outer peripheral portion of the plurality of vacuum ducts, and the plurality of vacuum ducts and the magnetic core. An outer cover for the plurality of vacuum ducts, wherein the plurality of vacuum ducts have a predetermined gap and are connected by a ring made of a ceramic material so that their central axes in the longitudinal direction coincide with each other; A method for controlling a high-frequency accelerating cavity in which an ion beam passing through the inside is resonantly accelerated by a high-frequency electric field generated in the gap, wherein the magnetic core is divided into a plurality by a plane including a central axis thereof. Adjusting the acceleration state of the ion beam by adjusting the interval between the divided surfaces of the magnetic core divided by the plane. Characterized in that as the high-frequency accelerating cavity control method. 9. The high-frequency voltage of opposite phase is applied to each of the vacuum ducts located on the left and right of the ring by being connected by the ring. Control method of high frequency accelerating cavity. 10. The high-frequency accelerating cavity includes a control unit for adjusting the interval between the divided surfaces of the magnetic core, and changing the interval between the divided surfaces during the acceleration of the ion beam, so that The method for controlling a high-frequency accelerating cavity according to claim 8 or 9, wherein an acceleration state of the beam is adjusted. 11. The control unit calculates an optimum distance between the divided surfaces of the magnetic core from a ratio of a resonance width to a high-frequency acceleration cavity calculated from a circulation frequency of the ion beam and monitor information of the ion beam intensity. The method of controlling a high-frequency acceleration cavity according to claim 10, further comprising: an operation unit that performs the operation, and a driving unit that drives the magnetic core to adjust the width of the division surface.