Conway Z.A.

Paper	Title	Page
TUP75	Progress on Cavity Fabrication for the ATLAS Energy Upgrade	331
	J. D. Fuerst, K. W. Shepard, M. P. Kelly, S. M. Gerbick, Z. A. Conway, G. P. Zinkann ANL
	An accelerator improvement project has been underway for several years to increase the energy of the ATLAS heavy ion linac at ANL. A new cryomodule containing drift-tube-loaded superconducting cavities is nearing the end of construction, with seven new cavities complete and ready for clean assembly into the cryostat. We describe the present status of the project, focusing particularly on cavity fabrication. Several cost saving techniques suitable for multi-unit production have been used, including electric discharge machining (EDM) part trimming and multi-part electron beam weld (EBW) fixturing. Subsystem fabrication including couplers, slow tuners, and VCX fast tuners is also described as are the clean processing techniques used for particle-free assembly.
WE205	Electro-mechanical properties of spoke-loaded superconducting cavities	404
	Z. A. Conway, J. D. Fuerst, M. P. Kelly, K. W. Shepard ANL G. K. Davis, J. Delayen TJNAF
	This paper presents experimental data characterizing the electro-mechanical properties of superconducting spoke-loaded cavities developed for high-intensity ionlinac applications, such as the cw ANL Advanced Exotic Beams Laboratory (AEBL) driver linac and the pulsed FNAL High Intensity Neutrino Source (HINS, now project X) proton driver linac. High-gradient cw operation at 4.2 K can produce violent boiling in the liquid helium coolant causing microphonic frequency noise. A spoke cavity designed to minimize the effects of helium pressure on RF eigenfrequency, the total microphonic induced RF frequency variations, were found to be on the level of the phase noise in the reference oscillator. To determine the pulsed cavity RF performance, the Lorentz transfer function was measured and used to predict the dynamic detuning in pulsed operation. There is good agreement between the predicted fit and the measured data, demonstrating the utility of the Lorentz transfer function, which can completely characterize the dynamics of the coupling between the mechanical cavity structure and the cavity RF field due to the Lorentz force.
	Slides(PDF)
WEP67	Low-level RF control of microphonics in superconducting spoke-loaded cavities	669
	Z. A. Conway, M. P. Kelly, S. I. Sharamentov, K. W. Shepard ANL G. K. Davis, J. Delayen TJNAF L. R. Doolittle LBNL
	This paper presents the results of cw RF frequency control and RF phase-stabilization experiments performed with a piezoelectric fast tuner mechanically coupled to a superconducting, 345 MHz, beta = 0.5 triple-spoke-loaded cavity operating at 4.2K. The piezoelectric fast tuner damped low-frequency microphonic-noise by an order of magnitude. Two methods of RF phase-stabilization were characterized: overcoupling with negative phase feedback, and also fast mechanical tuner feedback. The beta = 0.5 triple-spoke-loaded cavity RF field amplitude and phase errors were controlled to +(-)0.5% and +(-)30 respectively.