JP2022160053A - Acceleration cavity - Google Patents

Abstract

To solve a problem in which, in a conventional acceleration cavity, an error occurs between the axis of a drift tube and the axis of a charged particle beam by deformation due to resonance frequency adjustment during or after fabrication, and an error also occurs in the distance of a gap space between beam ports, which causes a decrease in the acceleration efficiency of the charged particle beam, but it is difficult to correct this error after fabrication of the acceleration cavity.SOLUTION: A deforming force imparting mechanism capable of imparting a deforming force to three mutually independent axial directions: X-axis direction (beam axis direction), Y-axis direction (perpendicular to the beam axis in the plane containing the beam axis), and Z-axis direction (perpendicular to the X-axis and Y-axis) is provided in an acceleration cavity, and this deformation force imparting mechanism makes it possible to displace the position of the drift tube installed in the acceleration cavity in three axial directions (X-axis, Y-axis, and Z-axis).SELECTED DRAWING: Figure 3

Description

The present application relates to acceleration cavities.

Accelerating cavities are known that accelerate charged particle beams such as electrons or protons (hereinafter also simply referred to as beams) using electric fields generated by resonating high frequencies. A pipe-shaped beam port and a drift tube are arranged on the beam acceleration axis, and charged particles are accelerated by the electric field generated in the gap space between the drift tube and the beam port. The electric field strength depends on the length of the gap space. In order to accelerate particles efficiently, it is necessary to precisely align the center axis of the drift tube, which is the path through which the particles pass, with the beam axis. In order to achieve the acceleration electric field intensity as designed, it is necessary to align the drift tube with the beam axis and the gap between the drift tube and the beam port.

Accelerating cavities include superconducting accelerating cavities using superconducting materials. Superconductivity is achieved by cooling with a coolant. As a result, the electrical resistance of the superconducting acceleration cavity becomes almost zero, and charged particles can be efficiently accelerated without power loss. A superconducting accelerating cavity requires a smooth inner surface to prevent breaking of the superconducting state due to a singularity.

Patent Literature 1 describes a method in which a position adjustment mechanism is provided outside a cavity in the upper part of the drift tube so that the center axis position of the drift tube can be adjusted in only one axial direction.

Patent Literature 2 describes a method in which a position-adjustable structure is provided in the upper part of the drift tube, and the position of the central axis of the drift tube can be adjusted in two axial directions.

Patent Document 3 describes a method in which a deformation mechanism is provided in the beam axis direction in a multiple superconducting accelerating cavity to apply an elastic deformation force to the cells to enable position adjustment in the beam axis direction.

JP-A-4-118900 Japanese Patent Application Laid-Open No. 2009-205939 Japanese Patent Application Laid-Open No. 11-67498

The technique described in Patent Document 1 adjusts the height of the drift tube through a through hole provided on the outer surface of the cavity, so it cannot be applied to a superconducting accelerating cavity that requires a smooth inner surface. Also, the adjustment is limited only in the vertical direction with respect to the beam axis, and adjustment in the beam axis direction and horizontal direction is not possible.

The technique described in Patent Literature 2 adjusts the position of the drift tube through a through hole provided on the outer surface of the cavity, so it cannot be applied to a superconducting accelerating cavity that requires a smooth inner surface. Also, adjustment is limited to the beam axis direction and horizontal direction, and adjustment in the height direction is not possible.

The technique described in Patent Document 3 is only for adjustment in the beam axis direction of the cell boundaries of the multiple superconducting accelerating cavity, and cannot be adjusted in the vertical and horizontal directions with respect to the beam axis.

The present application has been made to solve the above problems, and the position of the drift tube can be adjusted in three axial directions (the direction of the beam axis, the direction perpendicular to the beam axis within the plane containing the beam axis, and the directions in these two directions). The object is to obtain an accelerating cavity with the ability to be easily adjusted in the orthogonal direction).

The accelerating cavity disclosed herein comprises:
two beam ports that are entrances and exits for charged particle beams;
a drift tube arranged in a path through which the charged particle beam passes;
a stem that supports the drift tube;
a deformation force applying mechanism that displaces the installation position of the drift tube in three mutually independent axial directions by applying a deformation force to the stem;
is provided.

According to the acceleration cavity disclosed in the present application, the position of the drift tube can be easily adjusted in three axial directions (the direction of the beam axis, the direction orthogonal to the beam axis in the plane containing the beam axis, and the direction orthogonal to these two directions). It is possible to obtain an accelerating cavity with adjustable functionality.

1 is a schematic cross-sectional view showing an example of a schematic configuration of an acceleration cavity according to Embodiment 1; FIG. 1 is a perspective view of a main part of a spoke-type accelerating cavity that is an example of an accelerating cavity according to Embodiment 1; FIG. FIG. 3 is a schematic cross-sectional view of a main part of the spoke-type accelerating cavity of FIG. 2; 1 is a schematic cross-sectional view showing a QWR-type accelerating cavity (Quarter Wave Resonator) as an example of an accelerating cavity according to Embodiment 1; FIG. FIG. 6 is a schematic cross-sectional view showing a normal-conducting spoke-type accelerating cavity, which is an example of an accelerating cavity according to Embodiment 2; FIG. 10 is a schematic cross-sectional view showing a superconducting spoke-type accelerating cavity as an example of an accelerating cavity according to Embodiment 3; FIG. 12 is a schematic cross-sectional view showing another QWR-type accelerating cavity as an example of the accelerating cavity according to Embodiment 4;

The present application relates to acceleration cavities that use radio frequency electric fields to accelerate charged particle beams, in particular spoke cavities and quarter wave resonators. In these acceleration cavities, in general, in a region where the ratio of particle velocity to light velocity is relatively small (less than 0.5) for protons or heavy ions, in order to widen the gap length that contributes to acceleration, A relatively low frequency is used.

Embodiment 1.
The acceleration cavity 100 according to the first embodiment will be described below with reference to FIGS. 1 to 3. FIG. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an acceleration cavity 100 according to Embodiment 1. FIG. As shown in FIG. 1, in the acceleration cavity 100, a plurality of drift tubes 2 are generally arranged within the cavity wall 5 in the direction of the beam axis 6 through which ions pass.

In FIG. 1, seven drift tubes 2 are shown for simplicity, but more drift tubes are often arranged. The inside of the cavity wall 5 is evacuated. Each drift tube has a cylindrical shape with a central through hole along the beam axis 6 and is supported on the cavity wall 5 by a stem 3 . FIG. 1 shows an example in which stems 3 of adjacent drift tubes alternately extend in opposite directions.

Normally, in the acceleration cavity, high-frequency power is supplied from a high-frequency generator (not shown) into the cavity wall 5, and high-frequency electric fields are generated in the gaps (hereinafter referred to as drift tube gaps) G1, G2, . . . , G6 between adjacent drift tubes. ions traveling along the beam axis 6 are accelerated by this high-frequency electric field. Hereinafter, in order to solve the above-described problems, a specific device configuration for adjusting the positions of these drift tubes and displacing the gaps between the drift tubes will be described in detail.

First, a specific example for adjusting the position of the drift tube 2 will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a perspective view showing an example of a spoke-type acceleration cavity 101, which is one of typical acceleration cavities 100, and FIG. Together they represent an example of a single-spoke accelerating cavity. Here, FIG. 3(a) is a front view of this single-spoke accelerating cavity, and FIG. 3(b) is a sectional view along AA in FIG. 3(a).

2, 3(a) and 3(b), the aforementioned spoke acceleration cavity 101 supports two charged particle beam ports 1 and one drift tube 2 and the drift tube 2. It has one stem 3 . A support rod 4 is attached to the drift tube 2 . This support rod 4 passes through the interior of the stem 3 .

Here, the axis passing through the center of both beam ports 1 described above corresponds to the beam axis. The longitudinal direction of the beam axis is the X-axis, the direction in the plane containing the beam axis and perpendicular to the beam axis is the Y-axis, and the vertical direction from the plane formed by the X-axis and the Y-axis is the Z-axis. Therefore, these three axes are three-dimensional axes orthogonal to each other (independent from each other).

Further, outside the acceleration cavity, a deformation force applying mechanism 11 in the X-axis direction, a deformation force applying mechanism 12 in the Y-axis direction, and a deformation force applying mechanism 13 in the Z-axis direction are installed. are connected to the deforming force imparting mechanisms 11, 12 and 13 described above. The deformation force application mechanism 11 in the X-axis direction, the deformation force application mechanism 12 in the Y-axis direction, and the deformation force application mechanism 13 in the Z-axis direction are collectively referred to as a deformation force application mechanism. call.

By adjusting (operating) the deformation force applying mechanism 11 in the X-axis direction, the position of the drift tube in the X-axis direction is adjusted via the support rod 4 . Thereby, the distance of the gap space formed by the drift tube 2 and the beam port 1 can be adjusted to a predetermined value, and the accelerating electric field intensity on the upstream side and the downstream side of the charged particle beam can be made uniform.

By adjusting (operating) the deforming force applying mechanism 12 in the Y-axis direction and the deforming force applying mechanism 13 in the Z-axis direction, the axial position of the drift tube can be moved to match the beam axis.
As described above, the position of the drift tube can be adjusted by moving the position of the drift tube three-dimensionally. As a result, the component of the acceleration electric field in the off-axis direction can be suppressed, and the charged particle beam can be efficiently accelerated.

As an example of another acceleration cavity, FIG. 4 shows an example of a QWR-type acceleration cavity 102 . Here, FIG. 4(a) is a front view of the QWR accelerating cavity 102, and FIG. 4(b) is a sectional view along AA in FIG. 4(a).

The acceleration cavity comprises two beam ports 1 , drift tube 2 , cavity walls 5 and stem 3 . A support rod 4 passing through the stem 3 is attached to the drift tube 2 . A deformation force applying mechanism 11 in the X-axis direction, a deformation force applying mechanism 12 in the Y-axis direction, and a deformation force applying mechanism 13 in the Z-axis direction are installed outside the acceleration cavity. It is connected to the deforming force imparting mechanisms 11, 12 and 13 described above.

By adjusting the deformation force imparting mechanism 11 in the X-axis direction, a deformation force in the X-axis direction is applied to the drift tube 2 via the support rod 4 . Thereby, the distance of the gap space formed by the drift tube 2 and the beam port 1 can be adjusted, and the accelerating electric field intensity on the upstream side and the downstream side of the charged particle beam can be made uniform. Alternatively, it is also possible to intentionally create a difference between the accelerating electric field strengths on the upstream side and the downstream side of the charged particle beam.

By adjusting the deformation force application mechanism 12 in the Y-axis direction and the deformation force application mechanism 13 in the Z-axis direction, deformation forces in the Y-axis direction and the Z-axis direction are applied to the drift tube 2 via the support rod 4 . As a result, the position of the axis of the drift tube 2 can be moved to match the beam axis. As a result, the component of the accelerating electric field in the off-axis direction can be suppressed, and the charged particle beam can be efficiently accelerated.

Embodiment 2.
Next, an example of the acceleration cavity of Embodiment 2 will be described with reference to FIG. The acceleration cavity according to the second embodiment shown in FIG. 5 is, for example, a normal-conducting spoke-type acceleration cavity 103 without a coolant reservoir. Here, FIG. 5(a) is a front view, and FIG. 5(b) is a sectional view along AA in FIG. 5(a).

The deformation force imparting mechanism 11 in the X-axis direction, the deformation force imparting mechanism 12 in the Y-axis direction, and the deformation force imparting mechanism 13 in the Z-axis direction are each composed of a rotation drive section 14, a ball screw 15, and a reaction force receiver 16. FIG. A reaction force receiver 16 is connected to the outer surface of the acceleration cavity.

The support rod 4 is provided with a screw hole through which a ball screw 15 is passed. Ball screw 15 is supported by reaction force receiver 16 via bearing plate 17 . The reaction force receiver 16 and the bearing plate 17 are assumed to slide on each other.

When the drive shafts of the rotary drive units 14 of the X-axis direction deformation force application mechanism 11, the Y-axis direction deformation force application mechanism 12, and the Z-axis direction deformation force application mechanism 13 rotate, the respective ball screws 15 rotate. The support rod 4 moves in the X-axis direction, the Y-axis direction, and the Z-axis direction by this rotating shaft. The support bar 4 and the fixed drift tube 2 are also subjected to deformation force following this movement.

With the above mechanism, the position of the drift tube 2 can be easily adjusted by moving in three axes (X axis: beam axis direction, Y axis: horizontal direction, Z axis: vertical direction), that is, three-dimensionally.

Embodiment 3.
Next, an example of an acceleration cavity according to Embodiment 3 will be described with reference to FIG. The acceleration cavity according to Embodiment 3 shown in FIG. 6 is, for example, a superconducting spoke-type acceleration cavity 104 . The acceleration cavity includes a jacket 18 whose outer circumference is filled with a refrigerant, and a movable barrel 20 connected to the jacket 18 by a bellows 19 . 6(a) is a front view, and FIG. 6(b) is a cross-sectional view along AA in FIG. 6(a).

A movable barrel 20 is connected to the support rod 4 . A seat with a screw hole is provided on the outer periphery of the movable body, and the ball screw 15 of the deformation force applying mechanism 11 in the X-axis direction, the deformation force applying mechanism 12 in the Y-axis direction, and the deformation force applying mechanism 13 in the Z-axis direction. It is connected to the.

When the rotation drive units 14 of the X-axis direction deformation force application mechanism 11, the Y-axis direction deformation force application mechanism 12, and the Z-axis direction deformation force application mechanism 13 rotate, the respective ball screws 15 rotate and move. The barrel moves in the X, Y, and Z directions. As a result, the support rod 4 and the drift tube 2 connected to the support rod 4 receive a deforming force that follows the movement.

With the above mechanism, even in a superconducting accelerating cavity that requires a smooth inner surface and has a jacket filled with a coolant outside the accelerating cavity, the position of the drift tube 2 can be determined without protruding anything inside the accelerating cavity. It can be easily adjusted by moving three axes (X axis: beam axis direction, Y axis: horizontal direction, Z axis: vertical direction), that is, moving in three dimensions.

Embodiment 4.
Next, an example of an acceleration cavity according to Embodiment 4 will be described with reference to FIG.
An acceleration cavity according to the fourth embodiment includes, for example, a QWR acceleration cavity 105 shown in FIG. 7(a) is a front view of the QWR acceleration cavity 105, FIG. 7(b) is a cross-sectional view of the main part along the BB of the portion surrounded by the dotted line in FIG. 7(a), and FIG. (c) is a view showing the main part of the part surrounded by the dotted line in FIG. 7 (a) as viewed from arrow C, and FIG. 4 is an enlarged view of the winding mechanism; FIG. The white arrow in FIG. 7(d) indicates the rotation direction of the winding mechanism.

In Embodiments 2 and 3, the position of the drift tube is adjusted by the deformation forces of the deformation force applying mechanism 11 in the X-axis direction, the deformation force applying mechanism 12 in the Y-axis direction, and the deformation force applying mechanism 13 in the Z-axis direction. Although an example has been described, the acceleration cavity according to the fourth embodiment has a form different from that of the above-described second and third embodiments, as described below.

In FIG. 6, a mounting seat 51 is attached to the drift tube 2 of the acceleration cavity, a joint rod 52 is connected thereto, and a Z-axis direction adjustment rod 53 is connected thereto. The adjusting rod is fixed to the support seat 54 with, for example, screws. The connecting portion between the mounting seat 51 and the joint rod 52 is spherical and has a degree of freedom of inclination. The connecting portion between the joint rod 52 and the Z-axis direction adjusting rod 53 is spherical and has a degree of freedom of inclination. Two X-axis direction adjustment wires 55 and Y-axis direction adjustment wires 56 are connected to the mounting seat 51 via joint rods 52, and the X-axis direction adjustment wires 55 and Y-axis direction adjustment wires 56 are connected to , the winding mechanism 57 for adjustment in the X-axis direction and the winding mechanism 58 for adjustment in the Y-axis direction. The Z-axis direction adjustment rod 53 is connected to a rotation drive section 59 .

By unwinding and winding the X-axis direction adjustment wire 55 by the X-axis direction adjustment winding mechanism 57, the drift tube 2 can be moved in the XZ direction (X and Z direction) via the X-axis direction adjustment wire 55. direction). At this time, the drift tube 2 can be deformed without tilting the axis of the drift tube with respect to the beam axis by the movement of the connecting portion of the mounting seat 51 and the joint rod 52 .

Further, by unwinding and winding the Y-axis direction adjustment wire 56 by the Y-axis direction adjustment winding mechanism 58, the drift tube 2 can be moved in the YZ direction (Y and (Z direction). Further, by adjusting the rotary drive unit 59, the Z-axis direction adjusting rod 53 moves along the Z-axis, and the drift tube 2 receives deformation force along the Z-axis.

With the above mechanism, the position of the drift tube 2 can be easily adjusted in three axes (X axis: beam axis direction, Y axis: horizontal direction, Z axis: vertical direction). It can also be applied to superconducting accelerating cavities that require smooth inner surfaces.

While this application describes various exemplary embodiments and examples, various features, aspects, and functions described in one or more embodiments may not apply to particular embodiments. can be applied to the embodiments singly or in various combinations.
Accordingly, numerous variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, modification, addition or omission of at least one component, extraction of at least one component, and combination with components of other embodiments shall be included.

1 beam port, 2 drift tube, 3 stem, 4 support rod, 5 cavity wall, 6 beam axis, 11 X-axis direction deformation force application mechanism, 12 Y-axis direction deformation force application mechanism, 13 Z-axis direction deformation force Giving mechanism 14 Rotation drive unit 15 Ball screw 16 Reaction force receiver 17 Bearing plate 18 Jacket 19 Bellows 20 Movable body 51 Mounting seat 52 Joint rod 53 Z-axis direction adjustment rod 54 Support seat 55 X-axis direction adjustment wire, 56 Y-axis direction adjustment wire, 57 X-axis direction adjustment winding mechanism, 58 Y-axis direction adjustment winding mechanism, 100 Acceleration cavity

Claims (5)

two beam ports that are entrances and exits for charged particle beams;
a drift tube arranged in a path through which the charged particle beam passes;
a stem that supports the drift tube;
a deformation force applying mechanism that displaces the installation position of the drift tube in three mutually independent axial directions by applying a deformation force to the stem;
An accelerating cavity comprising: The deforming force imparting mechanism is
The distance between the drift tube and the beam port is displaced so that the acceleration electric field intensity for accelerating the charged particle beam has a predetermined value on the upstream side and the downstream side of the passing path, and displacing the installation position of the drift tube so that the axis and the beam axis connecting the centers of the two beam ports are aligned;
The accelerating cavity according to claim 1, characterized in that: wherein the accelerating cavity is a spoke-type cavity,
The deforming force applying mechanism is connected to the drift tube and applies deforming forces in three mutually orthogonal directions to the drift tube.
3. The accelerating cavity according to claim 1 or 2, characterized in that: The acceleration cavity is a spoke-type acceleration cavity that is made of a superconducting material and is cooled with a coolant so that the electrical resistance approaches zero,
a jacket that is arranged on the outer peripheral side of the acceleration cavity and filled with the coolant that cools the acceleration cavity in a gap between the acceleration cavity and the acceleration cavity;
a movable barrel that connects the jacket and the drift tube via a bellows;
with
A reaction force receiver for the deforming force applying mechanism is provided on the outer peripheral portion of the jacket, and the deforming force applying mechanism is connected to the movable barrel.
4. The accelerating cavity according to any one of claims 1 to 3, characterized in that: Connected to the drift tube and imparting deformation force to the drift tube by joints, wires, and a winding mechanism;
5. The accelerating cavity according to any one of claims 1 to 4, characterized in that:

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