Medical superconducting cyclotron resonant cavity capacitor tuning device and method

Abstract

The invention discloses a medical superconducting cyclotron resonant cavity capacitor tuning device and method. The device comprises a cavity and two sets of DEE plates arranged end to end in the cavity. Upper and lower sides of each set of DEE plates are respectively vertically connected with an inner rod. A tuning structure which moves relative to an end face of each Dee plate is arranged in the cavity. The tuning structure consists of a tuning capacitor plate and a moving rod. The tuning method comprises the steps that a vector network analyzer is used to adjust the resonant frequency; the reflection coefficient S11 is measured; the frequency point f1 corresponding to the minimum S11 is observed; f1 and the resonant frequency f0 are compared; if f1 is greater than f0, the capacitor plate is slowly moved to the left, otherwise the capacitor plate is slowly moved to the right; the change of the frequency point corresponding to the minimum S11 is observed; and if f1 is equal to f0, the moving of the capacitor plate is stopped to reach the frequency point of the working resonant cavity. According to the invention, automatically cavity frequency adjusting is realized; and the equivalent capacitance of a resonant circuit is changed by automatically controlling the capacitor plate to move to the right and left and tune the resonant cavity.

Description

technical field [0001] The invention belongs to the technical field of superconducting cyclotrons, and relates to a capacitance tuning device and method for a resonant cavity of a medical superconducting cyclotron. Background technique [0002] Cyclotrons are not only widely used in basic research fields such as nuclear physics, particle and solid state physics, but also play an important role in medical PET diagnosis, proton therapy, isotope production and industrial irradiation. It is imperative to build a medical cyclotron with independent intellectual property rights and put it into operation smoothly. [0003] When designing the cavity of a medical superconducting cyclotron, the resonant frequency should first be met. Because the operating frequency of the accelerator is single, the frequency selectivity of the cavity is required to be steep. However, in order to match the operating frequency of the magnet, the frequency of the cavity is expected to be A certain range ...

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Problems solved by technology

However, due to the thermal effect of the radio frequency system when the accelerator is in normal operation, there is a large deviation in the resonant frequency of the cavity before and after the thermal balance process. The existence of this deviation leads to a discrepancy with the theoretical design value, and the correct acceleration and extraction of the beam cannot be realized.

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