DESIGN CONSIDERATIONS FOR THE MECHANICAL TUNER OF THE RHIC ELECTRON COOLER SRF CAVITY *

The ECX Project, Brookhaven Lab's predecessor to the RHIC e-Cooler, includes a prototype RF tuner mechanism capable of both coarse and fast tuning. This tuner concept, adapted originally from a DESY design, has longer stroke and significantly higher loads attributable to the very stiff ECX cavity shape. Structural design, kinematics, controls, thermal and RF issues are discussed and certain improvements are proposed. DESIGN BASIS Several important parameters for the 5-cell SRF cavity of the ECX derive the design basis for the mechanical tuner (tuner, hereafter). The cavity fundamental RF mode is 703.75 MHz with a required 475 kHz tuning range. The calculated cavity stiffness is 6.84 kN/mm with tunin