Tongning Hu

Study of beam transverse properties of a thermionic electron gun for application to a compact THz free electron laser

A novel thermionic electron gun adopted for use in a high power THz free electron laser (FEL) is proposed in this paper. By optimization of the structural and radiofrequency (RF) parameters, the physical design of the gun is performed using dynamic calculations. Velocity bunching is used to minimize the bunchs energy spread, and the dynamic calculation results indicate that high quality beams can be provided. The transverse properties of the beams generated by the gun are also analyzed. The novel RF focusing effects of the resonance cavity are investigated precisely and are used to establish emittance compensation, which enables the injector length to be reduced. In addition, the causes of the extrema of the beam radius and the normalized transverse emittance are analyzed and interpreted, respectively, and slice simulations are performed to illustrate how the RF focusing varies along the bunch length and to determine the effects of that variation on the emittance compensation. Finally, by observation of the variations of the beam properties in the drift tube behind the electron gun, prospective assembly scenarios for the complete THz-FEL injector are discussed, and a joint-debugging process for the injector is implemented.

Anlysis and Design for Resonance Cavity of a Small-scale Medical Cyclotron

A small-scale medical cyclotron has been developing in Huazhong University of Science and Technology (HUST). The RF system mainly consists of a 10kW RF power generator and resonance cavity. Aiming at compact and robust structure, the resonance cavity adopts non-uniform characteristic impedance coaxial structure, and the magnet surface electroplated copper will be used as dummy Dees. The precise shapes and dimensions of cavity are designed and simulation results are carried out in this paper. The distributions of electromagnetic field are illustrated by means of numerical calculation analysis, and fine tuning devices are designed to realize frequency compensation as well. The RF power fed-in system is considered comprehensively with Dee-electrodes which all are settled in vacuum chamber, and the premise design of it has been preceded in this paper. In addition, the wooden model test is preformed before actual machining, and the test results are properly well compared with ideal FDTD calculation results.

Research and design of vacuum system for A 10MeV cyclotron

The particle has to be accelerated in a vacuum chamber to prevent accelerated particle colliding with any other gas molecules, besides, the vacuum is used to insulate the accelerating electrodes which work at a very high potential to earth. A vacuum system which operates at 10−7mbar and has to be completely nonmagnetic need to be designed for a 10 MeV cyclotron (CYCHU-10) developing in Huazhong University of Science and Technology (HUST). The vacuum chamber has to meet the requirements of intensity and airtightness which works at specified temperature and pressure condition, while weld container can completely meet these requirements. Otherwise, we should try to make the mechanical and thermal deformation of chamber induced by atmospheric pressure and thermal radiation of the accelerating electrodes (dees), which will affect the accelerating progress as small as possible. Finite-element analysis based on SOLIDWORKS Simulation will be used for mechanical deformation. The preliminary design of the vacuum system will also be described in this paper.