JLAB UPGRADE AND HIGH CURENT CAVITY DEVELOPMENTS*

We present the status and recent results from the development of new SRF cavities for the CEBAF 12 GeV upgrade and for future light source applications. The JLab 12 GeV upgrade requires ten new high-performance CW cryomodules. These will each contain eight seven-cell cavities of a "low-loss " design with HOM damping sufficient for ~1mA of continuous current. Jlab has fabricated and tested a number of such cavities and demonstrated compliance with all 12 GeV project requirements with conventional BCP cavity processing. Recently we have also electro-polished several cavities of this type and shown significantly better performance than the standard BCP. This processing method could provide improved operational margin and lower cryogenic loads at the CEBAF working point. For future light source applications such as FELs or ERLs, cavities with higher beam current capability are desirable. Jlab has developed a high-current cavity for such applications with a cell shape optimized to optimize HOM power extraction and maximize the BBU threshold. We report on the latest tests of this design and on plans to assemble a two-cavity cryomodule for testing with beam in the recirculation loop of the JLab FEL. CEBAF 12 GEV UPGRADE The CEBAF accelerator [1] will require several significant upgrades to support the 12 GeV program. This includes the installation of 10 cryomodules, 5 in each linac, providing an additional 1 GeV of energy gain per pass. Each cryomodule contains 8 SRF cavities, RF power couplers, cryogenic end caps, and thermal transition beampipes providing 108 MV of voltage which includes operational overhead for nominal operations at 100 MV. These cryomodules will be placed in the empty slots already existing at the high energy ends of the two linacs. SRF Cavities The cavity assembly, C100 cavity designation, include