Superconducting RF activities at Saclay: status report

This paper presents the RF superconductivity research and development work at Saclay for cavities designed for electron acceleration at 1.5 GHz. Improvements on diagnostics tools are presented together with recent work on a Nb TE 011 cavity designed for studies on surface resistance. An outline of MACSE, a short electron accelerator under construction, is also given. Sixteen tests were performed using five different cavities. For fields Eac higher than 20 MeV/m, the limitation is always due to a quench. Temperature maps performed at a field level just before the quench in superfluid helium show no temperature increase. This systematic effect seems to indicate that this quench could be induced by multipacting. Calculations show that a two-point multipactor trajectory near the equator is possible at a field level of 24±6 MeV/m. A five cell cavity without coupler was tested and showed a maximum accelerating field of 6.5 MV/m limited by electrons with a Qo value of 1010 at 1.8 K. A three cell cavity has also been tested. For improvement of diagnostics, numerical studies on the influence of the different parameters and operating conditions of the thermometers have been carried out. (N.K.)