162.5 MHz RFQ加速器的单束团选择
摘要
BackgroundThe nuclear physics experiment terminal of the China initiative accelerator driven system (CiADS) accelerator device requires a single bunch. The frequency of radio-frequency quadrupole (RFQ) accelerator of CiADS facitily is 162.5 MHz, so the pulse width of a single bunch is 6.15 ns. Due to the falling edge width of the conventional constant voltage Chopper is close to 20 ns, the 6.15 ns field-free area cannot be achieved.PurposeThis study aims to develop a new method to select a single bunch before RFQ to facilitate the superconducting linear accelerator of CiADS.MethodsUnder the premise of without changing the physical size of the deflector and the beam line layout in the low energy section of the beam chopper, a linearly alternating positive and negative voltage applied to the deflector plate of the chopper at CiADS prototype II was implemented to select a single bunch. The pulse alternating high voltage demand for 6.15 ns single bunch was calculated, and applied to the simulation software Tracewin to verify its performance.Results & ConclusionsSimulation results indicate that the voltage change slope needs to be 201.8 V·ns-1 for a 20 keV proton beam, so that a 6.15 ns single bunch can be selected. At the same time, the multi-particle simulation results show that the transmission of the low energy beam transport line (LEBT) is 80.7%, the RFQ transmission is 54.4%, and the overall transmission is 43.9%.