Construction of the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating linac represents the largest scale application of superconducting RF (SRF) technology to date. The accelerating structures in CEBAF are 169 pairs of 1.5 GHz SRF five-cell cavities-9 pairs in an injector and 80 pairs each in two linacs. Commissioning is now underway, with full energy beam expected in early 1995. All of the cavities have been assembled and have completed RF testing at 2.0 K in vertical dewars and in the accelerator. There was a significant reduction in performance in the accelerator. The difference in Q is ascribed to hydride precipitation enhanced by the slower cooldown in the accelerator.
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