A collaboration between Jefferson Lab and Cornell was formally established in the summer of 2004 to test the Cornell digital Low Level RF (LLRF) system on a high Qe cavity in an Energy Recovery Linac (ERL) and on a high Qe cavity under CEBAF like beam loading. The tests took place over the fall and winter in the Jefferson Lab FEL. To accommodate the Cornell LLRF system, Jefferson Lab provided a new transceiver and Clock/Master oscillator so that the Cornell system could synchronize with our cavity frequency and master oscillator. The tests were accomplished over three different weeks. The first week was devoted to initial setup and check out with no high power RF. The second week involved tests with high power RF without beam in a cavity and the third week included tests with beam. The tests were successful for both institutions. For Jefferson Lab they verified that a digital LLRF system is a viable method for controlling a high Qe cavity given the stringent demands for field stability. Meeting tight field stability requirements on high Qe cavities was viewed as a potential technical risk for digital LLRF systems in the 12 GEV upgrade and therefore verification was an R&D goal for the 12 GEV project.


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