科研之友
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摘要
[Background] The 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. [Purpose] This study aims to develop a new method to select a single bunch before RFQ to facilitate the superconducting linear accelerator of CiADS. [Methods] Under 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 & Conclusions] Simulation 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%.
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