JPH03171902A - Multiconnection high frequency acceleration cavity - Google Patents

Abstract

PURPOSE:To surely obtain a flat electric field distribution whose power effi ciency is high by providing an adjustable electric field distribution tuner in addition to a tuner for adjusting a resonance on cells of both end parts. CONSTITUTION:In addition to a cylindrical tuner 5 for adjusting a resonance frequency of a cavity, an electric field distribution tuner 8 is added to an end part cell 1a. That is, a disk 10 of a good conductive material such as copper, etc., is attached to the tip of a driving bar 11 consisting of a good conductive material such as copper, etc., as well, the driving bar 11 is connected to an electric field distribution tuner driving mechanism 9, and the position of the disk 10 can be adjusted. When the disk 10 is protruded to the inside of the end part cell 1a from the inside surface of a side plate 2, a capacitance of the end part cell 1a becomes large, and on the contrary, when the disk 10 is drawn in from the inside surface of the side plate 2, the capacitance becomes small. Accordingly, by the electric field distribution tuner 8, an electromagnetic characteristic of the end part cell 1a can be controlled. In such a way, an elec tric field distribution of a multiconnection high frequency acceleration cavity can be flattened.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a high-frequency acceleration cavity used in an accelerator that uses synchrotron radiation, for example. (Prior art) Accelerators are used to accelerate beams of electrons, protons, ions, etc. to high energy states of several billion electron volts (several GeV). In the field, large-scale structures, such as those with a diameter of 1 km or more, are being constructed. In addition, recently, medium-scale and small-scale synchrotron radiation has been applied to new fields such as physical property research using synchrotron radiation, which is generated when the orbit of electrons traveling at almost the speed of light is bent, and ultra-LSI microfabrication (lithography). Dedicated accelerators are also being built.

The accelerator is equipped with a high-frequency acceleration cavity to accelerate electrons and replenish energy lost due to synchrotron radiation. Inside the radio frequency acceleration cavity, a high frequency electric field of several hundred megahertz is generated that is synchronized with the orbit of the electrons, and the electrons are accelerated by this high electric field.

There are various types of high-frequency accelerating cavities, but the high-frequency power that should be supplied to the high-frequency accelerating cavities is approximately 80% of the electron energy.
The number increases in proportion to the power of the electron, so as the electron energy increases, the number of high-frequency acceleration cavities becomes extremely large.
For this reason, so-called multi-connected high-frequency acceleration cavities, in which multiple cavities are connected, are used to reduce the installation space of high-frequency acceleration cavities as much as possible. Figure 6 shows an example of a conventional multi-connected high frequency acceleration cavity, which has five cavities (la). (lb) (hereinafter referred to as cell), hollow cylindrical outer cylinder (1), hollow disc-shaped side plate ■, hollow disc-shaped partition ■, antenna (4), cylindrical tuner ■, tuner drive mechanism It consists of magnitude 0. Note that the high frequency acceleration cavity is connected to the beam duct 0 and maintained in a vacuum.

Such a high-frequency acceleration cavity is designed to have a specified resonant frequency (several hundred megahertz) that is an integral multiple of the frequency at which electrons circulate around the ring-shaped accelerator.

In order to adjust the resonant frequency changes due to temperature rise and deformation due to external pressure during operation, a tuner is provided for each cell or every other cell. Generally, the highest power efficiency is achieved when the electric field generated in each cell is equal and the electric field distribution is flat. However, the electromagnetic characteristics of the central cell (1a), which is sandwiched between other cells on both sides, and the cell (lb), which is connected to the beam duct ω and has a side plate (■) at both ends, have different electromagnetic characteristics. Assuming that the cells have the same structure, as shown in Figure 7, the electric field strength is high in the center cell and becomes lower as it approaches the edge cells. Therefore, the inner diameter of each cell is changed to make the electric field strength of each cell nearly uniform. At the DESY laboratory in West Germany, the inner diameter of the central cell in a 5-cell cavity is 419 mm.
am, the inner diameters of the cells on both sides thereof were set to 422 m, and the inner diameters of the cells at both ends were set to 424 m, but a sufficiently uniform electric field distribution could not be obtained.

(Problem to be solved by the invention) In this way, it is possible to make the electric field strength generated in each cell nearly uniform by changing the inner diameter of each cell, but the inner diameter of each cell is This has to be determined repeatedly, which is time-consuming to manufacture, and it is not always possible to obtain a sufficiently flat electric field distribution as a result. SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-connected high-frequency acceleration cavity that is easy to manufacture, can reliably obtain a flat electric field distribution with high power efficiency, and has excellent high-frequency characteristics.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention has a structure in which cells at both ends are provided with
In addition to the tuner that adjusts the resonant frequency, an adjustable electric field distribution tuner is provided. (Function) By providing electric field distribution tuners on both end cells to adjust the capacitance of the end cells and canceling out the difference in electromagnetic characteristics between the end cells and the center cell, an electric field of the same intensity is applied to each cell. occurs, resulting in a flat electric field distribution.

(Example) Hereinafter, a practical example of the present invention will be explained with reference to Figs. 1 and 2. In this embodiment, five cells (la) and (lb) are connected to form one high frequency acceleration cavity. (1) is a hollow cylindrical outer cylinder, ■ is a disc-shaped side plate joined to the outer cylinder (1) by silver brazing, etc., (3)
is a hollow disk-shaped partition wall for partitioning into a plurality of cells (la) and (lb). The partition wall (3) is also joined to the outer cylinder (1) by silver soldering etc. Both the side plate ■ and the partition wall ■ have circular holes (2a) and (3a) in the center;
The beam passes through the center of a). Circular hole (2a), (3
The reason why the area a) is raised in a nose shape (2b) and (3b) is to improve the characteristics of the high frequency acceleration cavity, and is not necessarily necessary. ■ is an antenna for supplying high frequency energy into the high frequency acceleration cavity.
1) and is connected to a high-frequency power source (not shown). Energy must be transmitted from one antenna to all five cells, so if the energy transmission is insufficient, cut a slot in the bulkhead (3) and connect the cell (l).
a), (lb) In some cases, the mutual coupling may be increased. ■
is a cylindrical tuner for adjusting the resonance frequency of the cavity, and one tuner is attached to each cell, or approximately one tuner is attached to every two cells. 0 is a tuner drive mechanism for inserting tuner 0 into the cell (1a) or pulling it out, and the drive source is an AC servo motor or the like. Note that the high frequency acceleration cavity is connected to the beam duct 0 and maintained in a high vacuum. Up to this point, the structure is similar to the conventional example shown in FIG. 6, but in this embodiment, an electric field distribution tuner (8) is added to the conventional structural elements. Electric field distribution tuner (
8) is shown in FIG. 2. That is,
(10) is a disk made of a highly conductive material such as copper, and is attached to the tip of the driving rod (11) also made of a highly conductive material such as copper. The drive shaft (1l) is connected to the electric field distribution tuner cantering mechanism (9) shown in FIG. 1, and can adjust the position of the disk (10). When the disk (10) is protruded from the inner surface of the side plate ■ into the end cell (la), the capacitance of the end cell (la) increases, and conversely the disk (10)
〉 is retracted from the inner surface of the side plate ■, the capacitance becomes smaller. In this way, the electric field distribution tuner allows control of the electromagnetic characteristics of the end cell. Note that the disc (10) and the drive shaft (11) can also be made of stainless steel plated with copper to a depth several times the skin depth into which the high-frequency current penetrates. circle! A refrigerant path is provided in the drive rod (10) and the drive rod (11) to flow a refrigerant such as pure water to remove heat generated by high frequency current. In addition, the drive rod (11) or disc (10) is pushed by a spring-like conductive contact to make complete electrical contact with the side plate (2), as shown in Figure 2 (a) or (b). There is. Next, the operation of this embodiment will be explained. According to the above configuration, by adjusting the electric field distribution tuner (■), the difference in electromagnetic characteristics between the end cells (la) and the center cell (1b) is canceled out, and the electric field generated in each cell is as shown in FIG. A flat electric field distribution with equal strength and high acceleration efficiency can be obtained, making it possible to improve the performance of multi-connected high-frequency acceleration cavities.

(Other Embodiments) In the above embodiments, an example of a 5-cell cavity was described, but the present invention is applicable to any number of cells.

Furthermore, as shown in FIGS. 4 and 5, similar effects can be obtained by mechanisms other than the disc-shaped tuner.

Figure 4 shows a cylindrical conductor (13
) is inserted from the outer cylinder (1). In this structure, the inductance of the end cell (la) is adjusted, but as a result, the same effect as the disc-shaped tuner (8) can be obtained.

Figure 5 shows the nose attached to the side plate ■ with the diaphragm (1
4), etc., to form a movable nose (15). The movable nose (15) is fixed to the flange of the side plate (2), and the position of the movable nose (15) is adjusted by inserting a spacer between the flanges.

In this structure, the capacitance of both end cells (1a) is adjusted, and the same effect as that of the disc-shaped tuner (8) can be obtained.

[Effects of the Invention] As described above, according to the present invention, it is possible to flatten the electric field distribution of a multi-connected high-frequency acceleration blank using an electric field distribution tuner. A more uniform electric field can be created more reliably than by methods such as changing the inner diameter of each cell during manufacture.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the multi-connected high frequency acceleration cavity of the present invention, FIGS. 2(a) and 2(b) are enlarged sectional views showing the electric field distribution tuner section of FIG. 1, and FIG. The figure is a curve diagram showing the effect of the above embodiment, Figures 4 and 5 are diagrams showing other embodiments, Figure 6 is a vertical cross-sectional view of the conventional example, and Figure 7 is the electric field distribution of the conventional example. 1... Outer cylinder 1a... End cell 1b.
...Central cell 2...Side plates 2a, 3a-Circular holes 2b, 3b-...Nose 3...Partition wall
4...Antenna 5...Tuner
6... Tuner drive mechanism 7... Beam duct
8... Electric field distribution tuner 9... Electric field distribution tuner drive mechanism 10... Disc 1l... Drive rod l2...
・Contact I3・Cylindrical electric field distribution tuner

Claims (1)

[Claims] In a multi-connected high-frequency acceleration cavity in which a plurality of cells are arranged in series through partition walls, a multi-connected high-frequency acceleration cavity is characterized in that each end cell has an electric field distribution tuner that can be adjusted separately from a general frequency adjustment tuner. High frequency acceleration cavity.