  A superconducting half-wave resonator has been designed with the frequency of
325 MHz and beta of 0.51. Different geometry parameters and shapes of inner
conductors (racetrack, ring-shape and elliptical-shape) were optimized to
decrease the peak electromagnetic fields to obtain higher accelerating
gradients and minimize the dissipated power on the cavity walls. To suppress
the operation frequency shift caused by the helium pressure fluctuations and
maximize the tuning ranges, the frequency shifts and mechanical properties were
studied on the electric and magnetic areas separately. At the end, the helium
vessel was also designed to keep the mechanical structure as robust as
possible. The fabrication and test of the prototype will be completed in the
beginning of 2016.
