• X. Wu, C. Compton, M. Doleans, W. Hartung, R.C. York, Q. Zhao
  NSCL, East Lansing, Michigan

An 8 GeV proton linac is being considered for the Fermilab accelerator complex. A design calls for five superconducting cavity types: three types of half-wave and two types of multi-cell elliptical structures. The elliptical cavity types have a frequency of 1.3 GHz with a beta = 0.81 and a beta = 1 and provide acceleration from 420 MeV to 8 GeV. An alternative concept would be to use an additional 1.3 GHz elliptical cavity type starting at 150 MeV. The alternative design may reduce project cost and risk. It would increase the technology overlap between Project X and the International Linear Collider. Preliminary simulations show the alternative linac layout has adequate longitudinal acceptance. This paper will discuss the beam dynamics studies for the alternative linac layout in comparison with the baseline layout.

• J. Popielarski, C. Compton, W. Hartung, M.J. Johnson, F. Marti, J.C. Oliva, R.C. York
  NSCL, East Lansing, Michigan

A medium-velocity half wave resonator has been designed and prototyped at the National Superconducting Cyclotron Laboratory for use in a heavy ion linac. The cavity is designed to provide 3.7 MV of accelerating voltage at an optimum beta = v/c = 0.53, with peak surface electric and magnetic fields of 32.5 MV/m and 79 mT, respectively. The resonant frequency is 322 MHz. The cavity was designed to reduce sensitivity to bath pressure fluctuations while maintaining a structure that can be easily fabricated, cleaned, and tuned. Deep draw forming dies and a copper cavity prototype were fabricated to confirm tolerances and formability. A prototype tuner was built; the helium vessel and power coupler have been designed. Measurements were performed to confirm finite element predictions for the mechanical modes, bath pressure sensitivity, tuner stiffness, and tuning range.

• J.-P. Carneiro, I.G. Gonin, N. Solyak, V.P. Yakovlev
  Fermilab, Batavia
• W. Hartung
  NSCL, East Lansing, Michigan
• B. Mustapha, P.N. Ostroumov
  ANL, Argonne

A superconducting cavity has been designed for acceleration of particles traveling at 81% the speed of light (beta = 0.81). The application of interest is an 8 GeV proton linac proposed for a Fermilab upgrade; at present, the cavity is to be used from 420 MeV to 1.3 GeV. The cavity is similar to the 805 MHz high-beta cavity developed for the SNS Linac, but the resonant frequency (1.3 GHz) and beam tube diameter (78 mm) are the same as for the beta = 1 cavities developed for the TESLA Test Facility. Four single-cell prototype cavities have been fabricated and tested. Two multi-cell prototypes have also been fabricated, but they have not yet been tested. The original concept was for an 8-cell cavity, but the final design and prototyping was done for 7 cells. An 11-cell cavity was proposed recently to allow the cryomodules for the beta = 0.81 cavity and downstream 9-cell beta = 1 cavities to be identical. The choice of number of cells per cavity affects the linac design in several ways. The impact of the number of cells in the 8 GeV linac design will be explored in this paper. Beam dynamics simulations from the ANL code TRACK will be presented.

• X. Wu, C. Compton, M. Doleans, W. Hartung, D. Lawton, F. Marti, R.C. York, Q. Zhao
  NSCL, East Lansing, Michigan

Funding: This work is supported by the U.S. Department of Energy

The superconducting (SC) driver linac developed for the proposed Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) will be able to accelerate stable beams of heavy ions to > 200 MeV/u with beam powers up to 400 kW. The driver linac front-end will include ECR ion sources, a bunching system for multi-charge state beams and a radio frequency quadrupole (RFQ). The superconducting linac will have a base frequency of 80.5 MHz primarily using SC cavities and cryomodules developed for the Rare Isotope Accelerator (RIA), the FRIB predecessor. A charge-stripping chicane and multiple-charge state acceleration will be used for the heavier ions in the driver linac. A beam delivery system will transport beam to the in-flight particle fragmentation target station. The paper will discuss recent progress in the accelerator system design for the superconducting driver linac.