• R.L. Geng, G. Ciovati, A.C. Crawford
  JLAB, Newport News, Virginia
• M.S. Champion, D.A. Sergatskov
  Fermilab, Batavia
• F. Furuta, K. Saito
  KEK, Ibaraki

Funding: Supported by DOE
Jefferson Lab plays an active role in the ILC high-gradient SRF R&D. Eight 9-cell cavities have been processed and tested so far by using the state-of-the-art recipes. Five reached a maximum gradient of over 32 MV/m. However, not surprisingly, the high-gradient performance is not necessarily reached during the first test. Re-processing by progressively more material removal can improve performance ultimately, but the number of re-processing cycles needed is un-predictable. Some cavities are quench limited repeatedly at around 20 MV/m. The quench locations are near the equator weld of specific cells. Based on the non-trivial high-gradient experiences in the past two years, we come to the conclusion that new capabilities beyond the state-of-the-art must be added to the existing SRF infrastructures in order to reliably achieve high gradients at a low cost. Targeted R&D is required to identify and characterize gradient limiting defects and field emitters. An enhanced high-gradient R&D program is emerging at JLab for continued contribution to realize the ambitious ILC gradient yield goal.

Slides

• G. Apollinari, I.G. Gonin, T.N. Khabiboulline, G. Lanfranco, A. Mukherjee, J.P. Ozelis, L. Ristori, G.V. Romanov, D.A. Sergatskov, R.L. Wagner, R.C. Webber
  Fermilab, Batavia
• J.D. Fuerst, M.P. Kelly, K.W. Shepard
  ANL, Argonne

The High Intensity Neutrino Source (HINS) project represents the current effort at Fermilab to develop 60 MeV Proton/H^- Linac as a front end for possible use in the Project X. Eighteen superconducting β=0.21 single spoke resonators (SSR), operating at 325 MHz, comprise the first stage of the HINS cold section. Two SSR cavities have now been fabricated in industry under this project and undergone surface treatment that is described here. We report the results of high gradient tests of the first SSR in the Vertical Test System (VTS). The cavity successfully achieved accelerating gradient of 13.5 MV/m; higher than the design operating gradient of 10 MV/m. The history of multipacting and conditioning during the VTS tests will be discussed. Experimental measurements of the cavity mechanical and vibration properties including Lorenz force detuning and measurements of X-rays resulting from field emission are also presented.