Shepard, K.W.

Paper	Title	Page
TUP26	Alternating Phase Focusing in Low-Velocity Heavy-Ion Superconducting Linac	348
	P.N. Ostroumov, K.W. Shepard ANL/Phys, Argonne, Illinois A. Kolomiets ITEP, Moscow E.S. Masunov MEPhI, Moscow
	The low-charge-state injector linac of the RIA post-accelerator is based on ~60 independently phased SC resonators providing total ~70 MV accelerating potential. The low charge-state beams, however, require stronger transverse focusing, particularly at low velocities, than is used in existing SC ion linacs. For the charge-to-mass ratios considered here (q/A = 1/66) the proper focusing can be reached by the help of strong SC solenoid lenses with the field up to 15 T. Magnetic field of the solenoids can be reduced to 9 T applying an Alternating Phase Focusing (APF). A method to set the rf field phases has been developed and studied both analytically and by the help of the three-dimensional ray tracing code. The paper discusses the results of these studies.
THP05	Superconducting beta=0.15 Quarter-Wave Cavity for RIA	605
	M. Kelly ANL, Argonne, Illinois Z.A. Conway, J.D. Fuerst, M. Kedzie, K.W. Shepard ANL/Phys, Argonne, Illinois
	A production-design 115 MHz niobium quarter-wave cavity with a full stainless steel helium jacket has been built and tested as part of the R&D for the Rare Isotope Accelerator (RIA) driver linac. The two-gap cavity is designed to accelerate ions over the velocity range 0.14<β<0.24. Processing of the cavity RF surfaces, including high-pressure rinsing and assembly of the cavity with a moveable high-power RF coupler were all performed under clean room conditions. Cold test results including high-field cw operation, microphonics, and helium pressure sensitivity will be presented in this paper. Performance of a pneumatically actuated slow-tuner device suitable not only for this cavity but a number of other cavities required for RIA will also be discussed.
THP06	Cold Tests of a Superconducting Co-Axial Half-Wave Cavity for RIA	608
	M. Kelly ANL, Argonne, Illinois J.D. Fuerst, M. Kedzie, K.W. Shepard ANL/Phys, Argonne, Illinois
	This paper reports cold tests of a superconducting niobium half-wave cavity with integral helium vessel, the design of which is suitable for production for the Rare Isotope Accelerator (RIA) driver linac. The cavity operates at 172 MHz and can provide more than 2 MV of accelerating voltage per cavity for ions with 0.24<β<0.37. Cavity RF surfaces were prepared using electropolishing, high-pressure rinsing and clean assembly. Measurements of Q0 show a residual RF surface resistance RS = 5 nΩs in both 2 K and 4 K operations. The cavity can be operated at 4.5 K with EAcc >10 MV/m (EPeak >30 MV/m). Performance exceeds RIA specifications of an input power of 12 Watts at 4.5 K and EAcc = 6.9 MV/m. RMS frequency jitter is only 1.6 Hz at EAcc = 8 MV/m and T = 4.5 K as determined from microphonics measurements in a realistic accelerator environment connected to the ATLAS refrigerator.
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