RF power tests of rf input coupler for the IFMIF/EVEDA RFQ prototype linac

Abstract For the IFMIF/EVEDA accelerator prototype RFQ linac, a 175 MHz rf input coupler based on a 6 1/8 in. co-axial waveguide is designed and manufactured. The rf coupler has cooling channels into the loop antenna and inner/outer-conductors around the RF window for CW operation mode, and the rf vacuum window module is replaceable by flanged connection. For rf power capability, nominal rf power of 160 kW and maximum transmitted rf power of 200 kW are required. In order to test the rf power capability, rf power tests using a high-voltage standing waves on a high-Q load circuit are carried out. For manufactured nine rf couplers including one spare, a stable 14 s CW operation at the equivalent rf power of 200 kW were achieved within 3–5 days rf aging. No rf contact defects, no unnecessary low-Q value and no extraordinary outgassing were validated.