General Design of 180 MHz RFQ for BNCT

Accelerator based boron neutron capture therapy (AB-BNCT) is a promising cancer treatment technology. An overall design have been proposed of a 180 MHz radio frequency quadrupole (RFQ) accelerator for BNCT. The particularity of dynamic design of the RFQ is that the average aperture radius changes along the accelerator. Beam dynamics design results show that the length of accelerator which accelerates protons from 35 keV to 2.81 MeV is 5.07 m, and the transmission up to 99.65%. In terms of radio frequency (RF) structure design, two shapes of cross section of cavity were simulated and compared, i.e., quadrilateral cavity and octagonal cavity. The results show that quadrilateral cavity performed better and was finally selected. Meanwhile, in order to keep the frequency of dipole mode away from the working quadrupole mode, 20 pairs of Pi-mode stabilizer rods are considered. The simulation results show that a large mode separation of more than 20MHz between the operating quadrupole mode and nearest dipole mode can be obtained, this is sufficient to deal with the errors caused by machining and misalignment.