Chalk River Nuclear LaboratoriesChalk River, Ontario, Canada KOJ IJO Sumina ry An RFQ linac operating at 100% duty factor (cw) and high currents is required for an accel erator breeder. Two high power structures are being built as part of the RFQ development program. Firstly, a copper 270 MHz "sparker" cavity with RFQ geometry is being tested to determine cw field breakdown levels and conditioning characteristics. The desi gn and status of the "sparker" are presented. Secondly, a 270 MHz cw RFQ linac (RFQ1) is being designed to accelerate a nominal 75 miA from 50 to 600 keV, to study beam quality and stability as well as resonator field tuning and leveling requirements under conditions of high beam loss at high average power. For example, the combination of cw operation and restricted space at the entrance require new approaches in end terminations and tuners. The status of RFQ1 is presented and design innovations outlined.
IntroductionThe low enerly beamn latinching section of an accelerator breeder , as now envisaged, requires a 300 mA 100% duty factor RFQ. This presents new design problenis, for the current is to be much higher than in existing designs, implying either increased vane voltage or increased bore hole size.Since the rf power increases very rapidly with bore hole radius ( r4), it is important to operate at the highest practical voltage gradient, i.e., just safely below the conditioned sparking limit. Although such limits have been studied for relatively high duty factor operation2, no definite information is available for cw operation, especially under conditions of high beam current, noderate beam spill, and a resulting high background pressure.