Status of the M-ECCTD F. Peauger - P. Bosland 3rd SRF Collaboration Meeting @ LASA 20 June 2016

Status of the M-ECCTD 1st medium beta cavities ESS067-P01: The heat treatment of the first cavity P01 has been performed at Zanon. As expected, the hydrogen concentration decreased by two decades after 12 hours of heating at 600 °C. Cavity has been delivered to CEA. 12 hours H 2 N2 H2O O2

Status of the M-ECCTD 2nd medium beta cavities ESS067-P02: The first BCP chemical treatment has been done on the cavity P02. Additional temperature probes have been added in the acid circuit and on the cavity surface. The first treatment was done in two steps of 25 minutes (50 minutes in total). Between these two steps, the cavity was emptied and rinsed with pure water. During the treatment the acid temperature was kept below 15 °C. After treatment, the p-mode frequency dropped to about 150 kHz which is consistent with previous BCP and 50 µm material removal. The field flatness have been controlled and is almost the same as before BCP (changed from 89% to 88%). Despite the “low temperature of the acid” the average etching rate of 1 µm/min is still higher than expected and usually observed. Additional thermalisation of the cavity itself before BCP treatment will be performed on the next treatment foreseen the 9th of May.

Status of the M-ECCTD Power couplers: The coupler plating of two additional double wall external conductors have been performed. The main tightness problems of the protecting tool have been solved and the coating aspect have been improved. Four doorknob transitions have been assembled at factory (Figure 2). The acceptance have been pronounced and the delivery at CEA is planned in two weeks.

Status of the M-ECCTD Cryomodule components : (IPNO activity) The thermal shielding fabrication is finished and delivered to Saclay The remaining components to be delivered are showed in the following table: Tubes for bursting discs Beginning of June 2016 Cryogenic circuits Mid May 2016 Diphasic tubes Intercavity belows and cold warm transitions July 2016

Status of the M-ECCTD Assembly toolings and infrastructures: Additional spaceframe insertion operations were performed with improved rails and wheels configuration. The alignment fiducials in the assembly hall have been installed. Two large toolings used to handle the cold warm transition and vacuum vessel doors were delivered at CEA the 2th of May. Power test stations: The call for tender for the second 704 MHz 1.5 MW klystron-based high power RF source have been completed. A candidate have been chosen and the pre-order have been submitted to the Public Procurement Commission. The preliminary 3D design of the cryogenic connexion box is nearly completed

Issues Status of the M-ECCTD Improvement of the acid cooling circuit and cavity during the chemical set-up. Q-disease of the medium beta P01 cavity