JPH0465520B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field This invention relates to a cyclotron that adjusts the resonant frequency of a resonant box provided in connection with an accelerating electrode (hereinafter referred to as a DE) in order to apply a high voltage to the DE. This invention relates to a frequency adjustment device.

(b) Prior Art In a cyclotron, in order to perform resonance acceleration of charged particles, it is necessary to apply a sufficiently high high frequency voltage to the D, which serves as an accelerating electrode. In order to obtain this accelerating voltage, a resonant box formed by inserting a stem with a dee attached to one end through an external conductor is used, and the resonant frequency and the accelerating frequency are matched. By the way, even if the acceleration frequency slightly deviates from the resonance value, the voltage applied to the derailleur will significantly decrease. Therefore, various cyclotron frequency adjustment devices that change the tuning conditions of the resonant box have been proposed and implemented. For example, the following methods are available for changing the resonant frequency of a resonant box.

A shorting plate is formed at the terminal end of the stem inserted into the outer conductor, and is in contact with the inner wall of the outer conductor. By sliding this shorting plate along the axial direction, the resonant frequency of the resonant box is changed. However, the terminal end of the stem has the largest current value and generates a lot of heat, so it is necessary to cool this part sufficiently. However, as described above, when a sliding portion is provided at the end of the stem, heat generation increases due to contact resistance. Therefore, this device is prone to failures and has the disadvantage that the structure of the resonance box is complicated due to cooling and the like.

There is a device that changes the resonant frequency of a resonant box by varying the inductance of the resonant box by changing the distance between the stem and the outer conductor facing the stem (Japanese Patent Publication No. 13080/1973). This type of device includes
(1) A foldable panel is housed in a resonant box and the resonant frequency of the resonant box is changed by expanding and contracting the panel; (2) one end is pivoted and the other end is an inner wall of the external conductor. There is a method in which the resonant frequency of the resonant box is changed by rotating a movable conductor piece that is in contact with the outer conductor along the inner wall of the outer conductor. However, the former has an extremely complicated structure and is not practical, while the latter has the problem of heat generation on the sliding surface.

(C) Purpose The purpose of the present invention is to provide a highly reliable cyclotron frequency adjustment device that can suppress heat generation in the device with a relatively simple configuration.

(D) Structure The cyclotron frequency adjustment device according to the present invention includes a stem having an accelerating electrode attached to one end of a bottomed cylindrical external conductor in which a small chamber and a large chamber are formed along the axial direction. The other end of the stem is inserted coaxially to short-circuit the other end of the stem and the bottom of the external conductor, and a sliding tube is fitted into the external copper body so as to be slidable along the axial direction. One end of the opening edge is electrically connected to the inner wall of the small chamber, and the other end of the opening edge is electrically connected to the inner wall of the large chamber.

(e) Embodiment FIG. 1 is a sectional view schematically showing the structure of an embodiment of a cyclotron frequency adjustment device according to the present invention, and FIG. 2 is a sectional view taken along the line II in FIG. 1.

In the figure, reference numeral 1 denotes an outer conductor formed of a bottomed cylindrical tube made of copper or the like. As a result of the diameter of the opening at one end of the external conductor 1 being reduced, a small chamber 2 is formed on the opening side in the external copper body, and a large chamber 3 is formed on the bottom side. 4 shows a stem made of copper pipe. A day 5 is attached to one end of the stem 4. The other end of the stem 4 is connected to the external conductor 1.
It is inserted coaxially into the bottom and short-circuited to the bottom.

Reference numeral 6 denotes a sliding tube that is slidably fitted along the axial direction of the outer conductor 2. One end of the sliding tube 6 is inserted into the small chamber portion 2. The other end of the sliding tube 6 has an enlarged diameter and is close to the inner wall of the large chamber 3. Sliders 7 and 7' are attached along the opening edges at both ends of the sliding tube 6, respectively. The sliders 7, 7' are made of elastic metal plates, such as phosphor bronze, formed into a comb shape. The sliders 7, 7' are electrically connected to the inner walls of the small chamber 2 and the large chamber 3, respectively. Such a sliding tube 6 is driven in the axial direction by a drive rod 8.

A resonance box composed of an outer conductor 1, a stem 4, etc. has impedances M1 and M2 determined by a stem outer diameter d1 and outer conductor inner diameters d2 and d3.
The impedance M1 is related to the capacity of the small chamber 2, and the impedance M2 is related to the capacity of the large chamber 3. Therefore, when the sliding tube 6 is driven in the axial direction by the drive rod 8, the length L1 of the small chamber portion 2 and the length L1 of the large chamber portion 3
Since the length L3 changes, the capacity inside the corner chamber also changes accordingly. As a result, the impedance M
1, M2 changes. For example, suppose that the sliding tube 6 moves to the right in FIG. In this case, the capacity of the large chamber section 3 becomes smaller, while the capacity of the small chamber section 2 increases. As a result, M1, which has a large impedance, becomes small, and M2, which has a small impedance, becomes large. Since the amount of decrease in M1 is greater than the amount of increase in M2, the impedance of the resonant box as a whole decreases, thereby increasing the resonant frequency. Conversely, moving the sliding tube 6 to the left lowers the resonance frequency of the resonance box. By moving the sliding tube 6 along the axial direction in this manner, the frequency of the cyclotron can be adjusted.

Next, the high frequency current flowing through such a resonant box will be explained.

The high frequency current has the largest value at the bottom of the outer conductor 1 where the other end of the stem 4 is short-circuited (A shown in FIG. 1). The current flowing through the slider 7 provided in the enlarged diameter part of the sliding tube 6 and the slider 7' in the reduced diameter part (B and C shown in FIG. 1) is higher than the current A flowing in the short circuit part. becomes significantly smaller. Therefore, the amount of heat generated in this sliding portion is sufficiently small.

In the above embodiments, the outer conductor is described as a circular tube, but it may also be a tube with a square cross section.

(F) Effect The frequency adjustment device for a cyclotron according to the present invention is configured so that a large current does not flow through the sliding portion between the sliding tube and the inner wall of the outer conductor, so that heat generation in the sliding portion can be suppressed. , thereby improving the reliability of the device.

Further, since the resonance frequency of the resonance box is adjusted by sliding the sliding tube in the axial direction, the configuration of the device can be relatively simple.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a cyclotron frequency adjustment device according to the present invention, and FIG. 2 is a sectional view taken along line II in FIG. DESCRIPTION OF SYMBOLS 1...Outer conductor, 2...Small chamber part, 3...Large chamber part, 4...Stem, 5...Die, 6...Sliding tube, 7, 7'...Slider.

Claims (1)

[Claims] 1. A stem having an acceleration electrode attached to one end and the other end thereof is coaxially inserted into a bottomed cylindrical outer conductor in which a small chamber and a large chamber are formed along the axial direction. While short-circuiting the other end of the stem and the bottom of the external conductor, a sliding cylinder is fitted into the external conductor so as to be slidable along the axial direction, and one end of the sliding cylinder is connected to the inner wall of the small chamber. A frequency adjustment device for a cyclotron, characterized in that the opening edge at the other end is electrically connected to the inner wall of a large chamber.