Separated function RFQ beam dynamics design and commissioning

Separated Function Radio Frequency Quadrupole (SFRFQ) accelerator is a new structure where diaphragms are loaded onto the quadrupole electrodes to form accelerating gaps, while the unmodulated RF quadrupole electric field provides transverse focusing. SFRFQ promises a higher accelerating efficiency than the conventional RFQ for heavy ions at low frequencies. In order to reduce reverse field and avoid RF sparking, an asymmetrical electrode and diaphragms designs were adopted. After simulation and RF design, a full scale SFRFQ prototype cavity with 14 βλ/2 cells has been constructed as a post-accelerator of the Peking University Integral Split Ring (ISR) RFQ. Beam commissioning was carried out to verify its feasibility. It accelerates O+ beam from 64 to 103 keV/u with a beam current exceeding 0.53 mA and the experimental results agree well with the simulation predictions by SFRFQCODEV1.0 [Z. Wang, J.E. Chen, Y.R. Lu, et al., Nucl. Instr. and Meth. A, 572, (2007) 596].