Figure 1: Quarter Wave- Length Cavity Geometry. Figure 2: Half Wave-Length Cavity Geometry.

We report the possible improvements of accelerating RF cavities for COSY proton-deuteron SC Linac [1]. The accepted accelerating structures are two-gap half-wave straight coaxial resonators. The terms of improvements are an accelerating field increase and tuning and chemical treatment simplification. Structures electrodynamics simulations and mechanic analysis have been provided. 1 CROSS-CAVITY INSTALLATION For the range of particle velocity β=v/c up to 0.2 the most common structure is a quarter-wavelength resonator (QWR) (Fig.1). However, this cavity up to now is used only in the heavy ion accelerators[2]. The existence of the magnetic field on the beam path makes problematic to use QWR for light particle acceleration [3]. Thats why a half-wavelength cavity HWR (Fig.2) is more favourable for protons or deuterons