Multi-mode tuning method for medical cyclotrons

Abstract

The invention belongs to the technical field of accelerators, and discloses a multi-mode tuning method for medical cyclotrons. The method comprises that after a radio frequency system is started and turned into a continuous running state, a phase locking loop (PLL) tracking cavity resonant frequency mode is used for tuning, and a fine tuning capacitance plate is placed in the middle of an adjustment stroke; when PLL frequency update tuning operates for 5 minutes to 10 minutes, a digital signal processor controls to switch an analogue switch, the fine tuning capacitance plate is converted from position feedback to capacitance plate tuning, and simultaneously, the PLL uses a current frequency value as a starting point and a final working frequency value as an ending point, and the frequency is reduced to working frequency and fixed in a mode with 0.002 MHz of stepping and an interval of 1s; and capacitance plate position signals are monitored continuously, a stroke intermediate point serves as a reference, protection points are arranged at 4 / 5 positions on the left and right, and the capacitance plate is fixed after being adjusted by the PLL when surpassing the positions. According to the multi-mode tuning method for medical cyclotrons, a whole process of radio frequency starting and running can be covered completely and conveniently, and the whole machine time utilization efficiency is improved.

Description

technical field [0001] The invention belongs to the technical field of accelerators, and in particular relates to a multi-state tuning method for a medical cyclotron. Background technique [0002] The existence of the thermal effect of the RF system causes a large deviation in the resonant frequency of the cavity before and after the thermal equilibrium process. This deviation leads to a discrepancy with the theoretical design value, and the correct acceleration and extraction of the beam cannot be realized. Generally, a frequency adjustment device is added to the cavity design for dynamic tuning, and a fine-tuning capacitor plate is usually used for tuning. In fact, the thermal effect of the cavity is related to the water cooling, system environment and power consumption design. When the water cooling is insufficient, the power consumption is too large, and the space heat dissipation is unfavorable, the fine-tuning capacitor board will not be able to realize the complete i...

AI Technical Summary

Problems solved by technology

In fact, the thermal effect of the cavity is related to the water cooling, system environment and power consumption design. When the water cooling is insufficient, the power consumption is too large, and the space heat dissipation is unfavorable, the fine-tuning capacitor board will not be able to realize the complete implementation of the RF system thermal balance process tuning function, directly The impact will be that the RF power utilization efficiency will be reduced, and the reflection will be too large, which will eventually trigger the RF system protection and cause shutdown

It is also possible to use multiple active shutdowns to artificially interfere with the heat balance process to avoid excessive deviation of the cavity frequency. This method is too low in time utilization efficiency and is generally not used.

Images