Research And Control For Subsystems Of Compact Low Energy Cyclotrons

PET (Positron Emission Tomography) is the most advanced technique of nuclear medicine presently. It has been introduced by many domestic hospitals due to the predominance in detecting of incipient tumors. As the primary isotope generator, most cyclotrons in our country depend on import. So it is significant to develop the compact low energy cyclotron of independent intellectual property rights. The research of the control system is an important step in cyclotron system design, which is related to the safety and stabilization of the cyclotron.In this thesis, the overall structure of the distributed control system is established firstly according to specific requirement of the compact low energy cyclotron. Then some design thought is proposed basing on the comprehensive analysis of the system constitution. The elementary system model of the primary cooling and secondary cooling is built in the foundation of cooling system research. For the secondary cooling, this thesis puts forward two mathematic modeling methods. After educing the mathematic model, a special controller for the time-delay system is designed using Dahlin Algorithm and Smith Predictor and simulated to get the ideal result. In addition, the vacuum system model is also designed with reference to the vacuum system of MINItrace cyclotron. The running logical process has been simulated by Simulink and Stateflow.Finally, the structure of RF System has been established. The method of picking-up a desired aliased signal of DDS output is accepted in the design of RF Power Generator. A device of AD9850 is used to generate RF signal in the system, and the amplitude modulation of system is achieved by a voltage variable attenuator. The amplifier based on tetrode is selected to get the output power of 10kW.Amplifier operates in a grounded cathode configuration. The PID-control strategy has been accepted in control system ,and the relay method has been used to do the measurement .Controller has a built-in Auto-tuning function which allows the PID parameters to be determined automatically using the Ziegler-Nichols method.