STATUS OF THE LANL ACTIVITIES IN THE FIELD OF RF SUPERCONDUCTIVITY

Since the last workshop we have tested six b=0.64, 700 MHz, 5-cell elliptical superconducting cavities in collaboration with JLAB in vertical cryostats. All the cavities exceeded the requirements for Accelerator Production of Tritium (APT) (Q0 = 5 x 109 at Eacc = 5 MV/m) with ample margin. The low-field Q0 at 2 K was 2-3 x 1010 and the maximum accelerating field reached 12 MV/m, which corresponds to peak electric and magnetic fields of 41 MV/m and 835 Oe, respectively. Power couplers have also been tested in a test bench up to over 1 MW. Since the APT project has transitioned to Advanced Accelerator Applications (AAA) project, a new type of superconducting accelerating structure called spoke cavity emerged as an excellent candidate for the low energy sections between the RFQ and the elliptical cavities. We tested a b=0.29, 340 MHz, 2-gap spoke cavity on loan from Argonne National Laboratory. The results showed Q0 = 2 x 109 at low fields and a maximum accelerating field Eacc = 12.5 MV/m at 4 K. At 5 MV/m, the Q0 was 1.5 x 109. Encouraged by these results, we started fabricating some spoke cavities and are planning to test one of them inmore » the beamline of LEDA (Low Energy Demonstration Accelerator) in the future.« less