RF control system for CEBAF

The design goal of the 2.5*10/sup -5/ RMS energy spread for the CEBAF (Continuous Electron Beam Accelerator Facility) electron beam demands strict control of the phase and amplitude of the 1.5-GHz accelerating field. To achieve such control in the presence of microphonic excitations, a separate system for each of the 338 superconducting cavities is required. The RF control system employs a heterodyne scheme which allows the use of high-precision analog circuits operating at 70 MHz. Presently, the 45-MeV CEBAF injector with 18 superconducting cavities is being commissioned, and this effort provides the first full integrated test in the accelerator tunnel, including cryogenics, RF, beam transport, and beam diagnostics. The RF control system design and objectives are discussed and compared to measured performance during the first commissioning phase. Hardware reliability and operational challenges experienced for RF control are presented. Presently, 25 MeV of the 45 MeV injector are installed and operational. It has been shown that 10 superconducting cavities are controlled simultaneously, meeting specifications for uncorrelated errors.<>