Physical Design Of QWR Cavity, Cryostat And ISOL High Mass Resolution Spectrometry For BRIF Project

Superconductivity technology is playing more important role in accelerator field. As an example, QWR superconducting cavity characterized with high mechanical stability and wide TTF range is used widely in low energy accelerating structure. Nb sputtered cavities, which are formed by coating Nb on copper bases, have better thermal stability and mechanical stability by inheriting not only superconductivity of Nb but also good thermal conductivity of copper. Based on this kind of cavity , the superconducting booster in Tandem Upgrade Project at China Institute of Atomic Energy (CIAE) will boost beam energy 2 MV/q higher by 4 Nb sputtered QWR cavities with 3.5MV/m of efficient accelerating gradient and 0.18m of efficient accelerating length.In this article, 3D electromagnetic field simulations are done. By Comparing with existing data, design frequency of QWR cavity at normal temperature is given, and geometry for this frequency is also optimized. Meanwhile 3D electromagnetic filed is introduced into beam dynamics codes to analyze cavity's performance on rf and beam dynamics. Simulations show that asymmetric distribution in QWR cavity will affect beam transportion, more attention should be paid when many QWR cavites are online. Physical analysis about mechanical tuner and rf coupling loop are also done as references for farther design.Physical design of high mass resolution spectrometer for ISOL system is also presented in this article. 20000 of mass resolution is necessary by request of physicists, but energy spread of beam coming from ion source and high voltage platform is much larger than this spectrometer can accept. In order to eliminate dispersion caused by energy spread of beam, a big&small dipoles structure based on Hermann Wollnik's idea is adopted and analyzed in details. TRANSPORT and TURTLE simulations for this spectrometry are carried out. According to results of simulations, an transverse reversing and matching section is introduced into the big&small dipoles structure to minimize energy spread dispersion.For the sake of completeness of my work on superconducting QWR cavities,description about beam dynamics and optics design I have done for ISAC-II project at TRIUMF Lab. in Canada is given in this article. In ISAC-II project, four type of QWR cavities are proposed, two of them are in manufacture, and the rest are in design. In my works, optimized β values and cavity's geometry for these values are given, beam dynamics comparison for different combinations is also done.