  A superconducting half-wave resonator (HWR) of frequency=162.5 MHz and
{\beta}=0.09 has been developed at Institute of Modern Physics. Mechanical
stability of the low beta HWR cavity is a big challenge in cavity design and
optimization. The mechanical deformations of a radio frequency superconducting
cavity could be a source of instability, both in continues wave(CW) operation
or in pulsed mode. Generally, the lower beta cavities have stronger Lorentz
force detuning than that of the higher beta cavities. In this paper, a basic
design consideration in the stiffening structure for the detuning effect caused
by helium pressure and Lorentz force has been presented. The mechanical modal
analysis has been investigated with finite element method(FEM). Based on these
considerations, a new stiffening structure has been promoted for the HWR
cavity. The computation results concerning the frequency shift show that the
low beta HWR cavity with new stiffening structure has low frequency sensitivity
coefficient, Lorentz force detuning coefficient KL and stable mechanical
property.
