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Inter University Centre (IUAC) in collaboration with Argonne National Laboratory, U.S.A., where the world's first heavy ion linac booster was installed, started developing RF superconducting Niobium quarter wave coaxial line resonators optimized for accelerating ions from our Pelletron accelerator upto mass A=100. The resonators will operate at 97 MHz and optimized for particle beta,(v/c)=0.08 . Resonators are fabricated entirely of niobium and are jacketed in a stainless steel vessel which contains the liquid helium. shows the QWCL resonator's sketch. A stainless steel to Niobium explosively bonded flange provides the welding transition between niobium and stainless steel. A novel pneumatic slow tuner in the form of a niobium bellow provides a tuning range of approximately 100 kHz, substantially larger than any working QWR resonator. All new design features have performed according to expectation in cold tests. QWR has exceeded the design goal of 3 MV/m @ 4W of RF power. Some of the design properties of the resonator are:
Multipacting in the cylindrically symmetric design do not pose any problem and is overcome by RF conditioning for a period of 14-18 hr.
Excellent mechanical stability, RF eigenfrequency jitter of only 10-20 Hz even when connected with recirculating helium refrigeration plant
The explosively bonded niobium to stainless steel transition proved reliable in exhibiting no observable vacuum leaks under repeated cycling over the temperature range 4K to 358K.
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