• S. Barbanotti, M.H. Foley, I.G. Gonin, J. Grimm, T.N. Khabiboulline, L. Ristori, N. Solyak, V.P. Yakovlev
  Fermilab, Batavia

Project X is a proposed high-intensity proton accelerator complex that could provide beam to create a high-intensity neutrino beam, feed protons to kaon- and muon-based precision experiments, and for other applications still under investigation. The present configuration of the proton accelerator foresees a section with 650 MHz beta = 0.6 and beta = 0.9 elliptical cavities. Prototypes of single-cell 650 MHz cavities and five-cell beta = 0.9 650 MHz cavities are being designed and fabricated at Fermilab in the R&D process for Project X. This paper summarizes the design status of the beta = 0.6 and beta = 0.9 single-cell prototype cavities, and also addresses the design effort focused on the five-cell beta = 0.9 cavities.

• N. Solyak
  Fermilab, Batavia

Project X is a proposed high-intensity H^- accelerator complex that could provide beam for a variety of physics projects: neutrino-, kaon- and muon-based precision experiments. Other applications are under investigation. In the current proposal CW 3MW linac would contains few types of superconducting cavities and focising elements to accelerate beam from 2.5 MeV up to 3 GeV. The paper presents the status of the 3GeV x 1mA CW linac, including design and testing of the linac components, beam physics studies and future plans.

• T.N. Khabiboulline, S. Barbanotti, I.G. Gonin, N. Solyak, I. Terechkine, V.P. Yakovlev
  Fermilab, Batavia

Front end of a CW linac of the Project X contains a H^- source, an RFQ, a medium energy transport line with the beam chopper, and a SC low-beta linac that accelerates H^- from 2.5 MeV to 160 MeV. SC Single ' spoke Resonators (SSR) will be used in the linac, because Fermilab already successfully developed and tested a SSR for beta 0.21. Two manufactured cavities achieve 2-3 times more than design accelerating gradients. One of these cavities completely dressed, e.g. welded to helium vessel with integrated slow and fast tuners, and tested in CW and pulse regimes. Successful tests of beta=0.21 SSR give us a confidence to use this type of cavity for low beta (0.117) and for high- beta (0.4) as well. Both types of these cavities are under development. In present report the basic constrains, parameters, electromagnetic and mechanical design for all the three SSR cavities, and first test results of beta=0.21 SSR are presented.

• V.A. Lebedev, J.-F. Ostiguy, N. Solyak
  Fermilab, Batavia
• A.V. Aleksandrov, A.P. Shishlo
  ORNL, Oak Ridge, Tennessee

A beam loss in the superconducting part of the SNS linac has been observed during its commissioning and operation. Although this loss does not prevent the SNS high power operation it results in an almost uniform irradiation of linac components and increased radiation levels in the tunnel. A multi-particle tracking could not explain the beam loss and its dependence on the machine parameters. It was recently found that the loss is related to the intrabeam particle collisions resulting in a stripping of one of two H^- ions. The paper describes experimental observations and corresponding calculations of the intrabeam stripping.