JPH1116699A - Input coupler for superconduction accelerating cavity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate fabrication and welding by making an end part in a semicircular shape, as for an input coupler for a superconduction accelerating cavity to accelerate a charged electron particle. SOLUTION: An input coupler 20 is attached to a superconduction accelerating cavity 1, and a charged electron particle beam 3 is introduced into the cavity 1 through the coupler 20, and an electric wave is inputted from the coupler 20 together with the charged electron particle beam 3 in order to accelerate the charged electron particle beam 3 by an accelerating voltage generated in the cavity 1 by the electric wave 6. Since an end of the input coupler 20 is made to be a semicircular shape, fabrication and welding becomes easier in comparison with a rectangular shape in the past, and product yield is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an input coupler for a superconducting accelerating cavity used in a superconducting accelerator system for accelerating charged particles.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional superconducting accelerator system, showing the inside of a vacuum chamber. In the figure, reference numeral 7 denotes an entire system, which is a device for guiding a charged particle beam into a superconducting accelerating cavity, introducing a radio wave from an input coupler, and accelerating the beam by the energy of the radio wave. 1 is a superconducting acceleration cavity, 2 is an input coupler, 3 is a charged particle beam, 4 is a liquid helium (LHe) tank, 5 is a vacuum tank, 6
Is an electric wave, and 8 is an accelerating voltage generated by the electric wave 6.

In such a device, when a radio wave 6 is injected into the superconducting acceleration cavity 1 through the input coupler 2, an acceleration voltage 8 is generated inside the cavity 1, whereby the charged particle beam 3 is accelerated. . Input coupler 2
Serves as a port for introducing this radio wave 6 into the superconducting acceleration cavity 1.

[0004] The shape of the input coupler 2, the charged particle beam 3 of the current to accelerate (I _B) and an acceleration voltage (V _B)
8. Optimized according to the shape of the cavity.

That is, if Q _i , which is a parameter representing the performance of the input coupler 2, is assumed that the energy increment of the charged particle beam 3 is P _b (= I _B V _B ), it is optimal when the following equation (1) is satisfied. Become.

[0006] In _{P b · Q i = P o} · Q o (1) wherein, Q values representing the P _o, Q _o is loss and performance in each superconducting accelerating cavity within 1.

Conventionally, the shape of the input coupler 2 is as follows.
This is a rectangle obtained by extending a general waveguide, and has an appropriate positional relationship with the superconducting accelerating cavity 1 so as to satisfy the expression (1) (FIG. 6).
(See dimension d shown in (a)).

The superconducting accelerating cavity 1 integrated with the input coupler 2 is mounted in an LHe tank 4 in order to maintain the superconducting state, and the LHe tank 4 is housed in a vacuum tank 5 for further insulation.

[0009]

The conventional input coupler 2 attached to the conventional superconducting acceleration cavity 1 described above.
Has a problem in that the shape of the end is rectangular, and cracks and wrinkles are likely to occur during deep drawing during processing.

As shown in FIG.
This is a structure in which the half couplers 19 are joined together by electron beam welding. In particular, electron beam welding 12 is used for welding in order to maintain the superconducting property and to avoid mixing of impurities. In the electron beam welding 12, it is important to control the welding speed. In the case where the conventional end portion has a rectangular shape, as shown in FIG. Therefore, it is difficult to keep these welding speeds constant, and there is a problem that a stable beat cannot be obtained, the yield is low, and the cost is high.

[0011]

According to the present invention, in order to solve the above-mentioned problems, an input coupler for introducing a charged particle beam and a radio wave in a superconducting accelerator system has a semicircular end portion.

That is, the present invention relates to a superconducting accelerator for guiding a charged particle beam to a superconducting accelerating cavity, introducing a radio wave from one end orthogonal to the direction of introduction of the charged particle beam, and accelerating the charged particle beam by the acceleration voltage. An input coupler for a superconducting acceleration cavity, wherein an end shape of a surface orthogonal to the beam introduction direction at the other end opposite to the one end for introducing the radio wave is made semicircular in the input coupler of the system. I will provide a.

According to the present invention, since the end shape of the input coupler is made semicircular as described above, deep drawability during processing is better than that of a conventional rectangular shape, so that cracks during molding can be reduced. Wrinkles are less likely to occur.

Further, this input coupler usually has
The two half couplers are joined together and welded, but electron beam welding is used to avoid contamination by impurities in order to maintain superconducting properties.
Since the welding line is composed of a straight line, a constant curvature, and a large arc, it is easy to keep the welding speed of electron beam welding constant, and a stable welding bead can be obtained.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a side view of an input coupler for a superconducting acceleration cavity according to an embodiment of the present invention,
FIG. 2 is a view taken along the line AA. In both figures, a charged particle beam 3 is input to a superconducting acceleration cavity 1 by an input coupler 2.
0, and a radio wave 6 is applied from a direction orthogonal to the acceleration axis (center axis) of the charged particle beam 3 of the input coupler 20, and an acceleration voltage 8 is generated therein, whereby the charged particle beam 3 is accelerated. Is done. As shown in FIG. 2, the input coupler 20 has a semicircular shape 15 at the end of the surface viewed from the central axis.

FIG. 3 shows this improved input coupler 2.
0 is a cross-sectional view, (a) is a view seen from the acceleration axis direction, (b)
Is a side view thereof. In the figure, first, the distance L from the electron beam acceleration axis (center axis) to the end of the input coupler 20 is optimized so that the value of the performance Q _i of the input coupler 20 is stabilized. This value is set to 115 mm by a model test or the like. Further, in the present embodiment, the resonance frequency in the cavity is set to 1.3 GHz.
The inner dimension W of the width is 140 mm, and the semicircular portion 1 at the lower end.
The inner radius R of No. 5 was set to 70 mm.

FIG. 6 is a diagram showing characteristics Q _i of the improved input coupler. As shown in (a), the measurement was performed using the distance d between the main body of the superconducting acceleration cavity 1 and the improved input coupler 20 as a parameter, and (b) shows the result. The data shown in FIG.
Using the equation (1), Q _i is obtained from the current (I _B ), voltage (V _B ) of the charged particle beam 3 to be accelerated, and the loss _Po and Q _o value in the superconducting accelerating cavity 1. _The distance d corresponding to _i is determined.

Next, a method of manufacturing the input coupler 20 designed as described above will be described with reference to FIGS. As shown in FIG. 4, a superconducting material (here, niobium material) is deep-drawn using a deep-drawing male die 10 and a deep-drawing female die 11, and the half-drawing as shown in FIG. Two couplers 9 are manufactured. At this time, since the lower end of the input coupler 20 is formed in a semicircular shape, it is known that cracks and wrinkles hardly occur during molding.

Next, as shown in FIG. 5B, the molded half couplers 9 are welded together by electron beam welding 12 or the like.
Since the lower end has a semicircular shape, the welding speed can be kept constant over the entire length of the bead wire, and a good bead can be obtained.

In the next step (c), the beam pipe 16
The improved input coupler 20 is completed by joining the coupler flanges 17 as in the steps shown in FIGS.

The superconducting accelerating cavity 1 provided with the improved input coupler 20 completed in this manner maintains a superconducting state similarly to the conventional example shown in FIG.
e) A vacuum chamber 5 is installed in 4 and further insulated therefrom.
It covers the surroundings.

According to the above-described embodiment, by forming the end portion of the input coupler 20 into the semicircle 15, deep drawing can be performed more favorably at the time of processing than the conventional short input coupler 2. Cracks and wrinkles during molding are less likely to occur. Further, since the welding line 12 is composed of a straight line and an arc having a large curvature, the welding speed of the electron beam welding 12 is easily maintained at a constant level, and a stable welding bead is obtained. It is something that can be done.

[0023]

As described above, according to the present invention, the input coupler for introducing the charged particle beam and the radio wave in the superconducting accelerator system has a semicircular end. The following effects are obtained.

[0024] Deep drawing at the time of working becomes better than the conventional short form, and the occurrence of cracks and wrinkles at the time of forming can be reduced.

Since the welding line is composed of a straight line portion and an arc portion having a constant curvature, the welding speed can be kept constant, so that a stable welding bead can be obtained, the product yield can be improved, and the cost can be improved. Reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a side view of an entire superconducting acceleration cavity to which an input coupler for a superconducting acceleration cavity according to an embodiment of the present invention is attached.

FIG. 2 is a view taken in the direction of arrows AA in FIG.

3A and 3B are diagrams of an input coupler for a superconducting accelerating cavity according to an embodiment of the present invention, wherein FIG. 3A is a cross-sectional view in the direction of an acceleration center axis, and FIG.

FIG. 4 is a sectional view showing a mold for manufacturing an input coupler for a superconducting acceleration cavity according to an embodiment of the present invention.

FIG. 5 is an assembly diagram of an input coupler for a superconducting accelerating cavity according to an embodiment of the present invention, in which (a) is a cross-sectional view of a half coupler after molding, and (b) is an input obtained by welding two half couplers. FIG. 4C is a cross-sectional view of the coupler, FIG. 4C is a cross-sectional view of a state where a beam pipe is coupled to the input coupler, and FIG. 5D is a cross-sectional view of a state where a coupler flange is coupled to the state of FIG.

[6] In the performance characteristic diagram of the input coupler superconducting accelerating cavity according to the embodiment of the present invention, (a) is a diagram showing the distance between the accelerating cavities and the input coupler, (b) the distance and characteristics Q _i FIG.

FIG. 7 is a cross-sectional view of a conventional superconducting accelerator system.

8A and 8B are perspective views showing a state of assembling a conventional input coupler for a superconducting accelerating cavity, in which FIG. 8A shows a state of a half coupler, and FIG. 8B shows a state in which an electron beam of the half coupler is welded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Superconducting acceleration cavity 3 Charged particle beam 4 LHe tank 5 Vacuum tank 6 Radio wave 8 Acceleration voltage 9 Half coupler 10 Male for deep drawing 11 Female for deep drawing 12 Electron beam welding 20 Input coupler

Claims (1)

[Claims] An input of a superconducting accelerator system for guiding a charged particle beam into a superconducting acceleration cavity, introducing radio waves from one end orthogonal to the direction of introduction of the charged particle beam, and accelerating the charged particle beam with the acceleration voltage. An input coupler for a superconducting acceleration cavity, wherein a shape of an end of a surface orthogonal to the beam introduction direction at the other end opposite to the one end for introducing the radio wave is semicircular.