  A high-intensity continuous wave (CW) radio frequency quadrupole (RFQ)
accelerator is designed for boron neutron capture therapy (BNCT). The
transmission efficiency of a 20-mA proton beam accelerated from 30 keV to 2.5
MeV can reach 98.7% at an operating frequency of 200 MHz. The beam dynamics has
good tolerance to errors. By comparing the high-frequency parameters of
quadrilateral and octagonal RFQ cross-sections, the quadrilateral structure of
the four-vane cavity is selected owing to its multiple advantages, such as a
smaller cross section at the same frequency and easy processing. In addition,
tuners and undercuts are designed to tune the frequency of the cavity and
achieve a flat electric field distribution along the cavity. In this paper, the
beam dynamics simulation and electromagnetic design are presented in detail.

Accelerator Physics