Fong K.

Paper	Title	Page
MO402	Recent Progress in the Superconducting RF Program at TRIUMF/ISAC	42
	R. E. Laxdal, K. Fong, M. Laverty, A. Mitra, Q. Zheng, V. Zvyagintsev TRIUMF
	The first phase of the ISAC-II superconducting accelerator has recently been commissioned. The heavy ion linac adds 20MV to the 1.5MeV/u beam injected from the ISAC post accelerator. The linac is composed of five cryomodules; each cryomodule housing four 106 MHz quarter wave resonators (Beta0= .057, 0.071) and one 9 T superconducting solenoid all operating at 4K. On-line performance has confirmed cw cavity operation at a peak surface field in excess of 35 MV/m. Performance after 18 months of operation and a full thermal cycle during the annual shutdown shows very little degradation in performance. The second phase of the program will see the installation of a further 20 MV of 141 MHz quarter wave cavities with (beta0=0.11. Two prototypes of the cavities are now in production. The mechanical drive for the coupling loop of the Phase I cavities is now being modified to improve the motion as part of the Phase II hardware development. TRIUMF is proposing to build a 50MeV electron driver as part of the next five year plan. Consequently plans are now underway to upgrade the SRF lab to support developments at 1.3 GHz. The report will summarize all aspects of the program.
	Slides(PDF)
TUP21	RF Cavity Performance for the ISAC-II Superconducting Linac	166
	R. E. Laxdal, K. Fong, M. Laverty, A. Mitra, Q. Zheng, V. Zvyagintsev TRIUMF
	The ISAC-II superconducting linac with twenty 106 MHz quarter wave cavities is now operational since April 2006. The cryomodule design is such that the cavity rf surfaces share the vacuum space with the thermal isolation volume. Because of this we are interested in logging the performance of the cavities over time to estimate degradation due to contamination during operation or maintenance. Early commissioning demonstrated on-line cw performance at a peak surface field in excess of 35 MV/m. Performance after one year of operation and a full thermal cycle during the annual shutdown shows very little degradation in performance. The paper summarizes the rf performance with a particular look at maintenance and operation issues.
WEP76	Performance of RF amplifiers for ISAC-II medium beta linac operation	685
	A. K. Mitra, K. Fong, R. E. Laxdal, J. Lu, R. Shanks TRIUMF
	A heavy ion superconducting linac at TRIUMF to increase the final energy of radioactive beams from the existing room temperature ISAC accelerator is now operational. The linac consists of twenty quarter wave cavities operating at 106 MHz to produce an accelerating voltage gain of 20 MV. This paper describes the operational experience of the 106 MHz rf tube amplifiers which were installed and commissioned for the medium beta linac in October 2005. Total rf power installed is 16 kW where one quarter power is used for regular linac operation. During the initial commissioning of the amplifiers, only one power tube was found to be noisy and was replaced. The first major tube failure occurred in April 2007 after 9000 operating filament hours. Soon thereafter five more tubes showed signs of loss of gain. It was evident that most of the tubes reached their tube life by this time and all were replaced with new tubes. The extension of tube life, and prediction of tube failure are the main concerns of these tube amplifiers. Efforts are being made to incorporate reduced filament power operation in order to get longer tube life. Systematic check of the amplifier performance during scheduled maintenance and shutdown period is undertaken. Reduction of tube emission and hence gain degradation from their nominal value causes excessive drive power from the rf control system to keep the cavity voltage constant under closed loop. Hence monitoring the drive power is useful to predict early tube failure. Input drive power and gain of all the 20 amplifiers are available at the EPICS data archive which can be monitored and plotted. This will allow early warning of tube failure so that tubes can be replaced before they actually fail. The failure modes of the tubes and diagnostics to predict tube failure will be described.