The Development Of TOPOPIC Code And Halo Suppression Study In FODO Channel

A new linear accelerator designs and simulations code TOPOPIC (Trace ofparticle orbit with PIC) based on Particle-In-Cell method is developed at IMP by theauthor. The code was benchmarked with BEAMPATH which shows very goodagreements. It is applied for detailed beam evolution studies in RFQ for theInjector-II of CADS (Chinese Accelerator Driven Subcritical-system) project.For CADS project and other high intensity superconducting linacs, the beam losswhich is mainly related to beam halo, is of the big concern. Beam dynamics inperiodical channel is the basic model to study the halo mechanism. In this thesis, boththe analytical and the numerical studies are carried out for this subject. For the case ofhigh intensity beam in FODO channel, the beam halo which is generated due to thenonlinear space charge, has been always accompanying beam evolution. In order tomitigate the deleterious effects of the beam halo in the channel, two duodecapole lenswere inserted in one FODO period to depress the space charge effect at the beamboundary. In our simulations, the results demonstrate that the beam halo is suppressedeffectively in the above setup.As other related works, the author also designed the low energy beam transportline and RFQ for HIAF (Heavy Ion Accelerator Facility) project. The scheme ofmulti-harmonic-buncher (MHB) and RFQ with initial phase45is adopted todecrease the longitudinal rms emittance at the exit of RFQ, which well satisfies thedesign requirements.