The Study Of Automatic Conditioning System For Cyclotron Cavity

In recently years, the high intensity cyclotron had been used in the field as the fundamental physics research, life science, diagnosis and treatment of medicine and so on more and more. Build the medical cyclotron which own the proprietary intellectual property rights,and make it can operating successfully,is a focus of the laboratory of cyclotron in a lot of countries. In the course of debugging for cyclotron, it’s the most time-consuming to finish the conditioning of the RF cavity,and it must use too much difficult method. The thesis regard this as the starting point, through investigating the new technology of auto-conditioning system for the cavity of accelerator, had designed an auto-conditioning system for the cavity of high intensity cyclotron.On the base of discussing the inhibition mechanism of the multipactor, the thesis had design the auto-conditioning system for the cavity of high intensity cyclotron. And according to the own feature of the cavity of high intensity cyclotron, combining the Pulsing model and the CW model, Make the design come true.The thesis researches and achieves the pulse model, this model applies to the preliminary stage of the conditioning,and the multipactor should be serious at this stage. The characteristic of this model is that it use the pulse with low duty ratio to be the input of the conditioning of the cavity for preventing damaging the key component (for example the coupling window)from the high reflected power. The thesis had improve the traditional conditioning of pulse, and used the superiority of high dynamic range(HDR) of the modern phase discriminator, increasing by tuning during the pulsing interval with the lowest power, kept tuning during the pulse, and came true the function of tracking the frequency of the cavity in the pulse model creatively.The thesis researches and achieves the CW model. This model use the CW power to conditioning the cavity deeply after the pulse model had achieve the certain effect. In this model,the thesis researches and achieves FM signal source module based on DDS to come true the function of the CW sweeping frequency, and researches and achieves PI controller to limit reflected power in the conditioning process, and researches and achieves the digital frequency tracking and tuning loop to keep tuning the frequency after successfully establish Dee voltage in the cavity. Finally, the thesis researches and achieves the function of descending amplitude with timing. This design method is beneficial to enter into the multipacting area from the high power direction, and easy to reach the saturation of the oscillating electron cloud in the cavity, and can gain higher conditioning efficiency.Although the thesis aims at the conditioning of cavity for the high intensity cyclotron with the fringe magnetic field, but for the other accelerators, especially aims to the multi-cavity feature of the linac, the thesis has the more generalized significance.