Result of a 700 MHz superconducting cavity for a waste transmutation linear accelerator

In the frame of the 'demonstrator' project for nuclear waste transmutation, a R and D program on the high-energy section of the Superconducting Accelerator for Hybrid (ASH) has been proposed in France. It aims at developing 700 MHz superconducting radiofrequency (SCRF) cavities for the two different beta sections (β = 0.47 and 0.65). As the (β 0.65) cryo-modules will fill up most of the accelerator, focussing was directed towards building and testing one of these cavities. A single-cell (β = 0.65) SCRF cavity has been designed at Saclay and built in industry (CERCA). Mechanical stiffness was analyzed at Orsay. A first cryogenic test has been performed showing excellent RF performance. The Qo value was as high as 7x1010, indicating extremely low RF losses. The accelerating field went up to 26 MeV/m, exceeding by more than a factor of two the design point (around 10 MeV/m). (author)