Jefferson Lab, Newport News, Virginia
Operation of the JLab IR Upgrade FEL at CW powers in excess of 10 kW requires sustained production of high electron beam powers by the driver ERL. This in turn demands attention to numerous issues and effects, including: cathode lifetime; control of beamline and RF system vacuum during high current operation; longitudinal space charge; longitudinal and transverse matching of irregular/large volume phase space distributions; halo management; management of remnant dispersive effects; resistive wall, wake-field, and RF heating of beam vacuum chambers; the beam break up instability; the impact of coherent synchrotron radiation (both on beam quality and the performance of laser optics); magnetic component stability and reproducibility; and RF stability and reproducibility. We discuss our experience with these issues and describe the modus vivendi that has evolved during prolonged high current, high power beam and laser operation.
Jefferson Lab, Newport News, Virginia
Notional designs for ERL-driven high average power free electron lasers often invoke amplifier-based architectures. To date, however, amplifier FELs have been limited in average power output to values several orders of magnitude lower than those demonstrated in optical-resonator based systems; this is due at least in part to the limited electron beam powers available from their driver accelerators. In order to directly contrast the performance available from amplifiers to that provided by high-power cavity-based resonators, we have developed a scheme to test an amplifier FEL in the JLab SRF ERL driver. We describe an accelerator system design that can seamlessly and non-invasively integrate a 10 m wiggler into the existing system and which provides, at least in principle, performance that would support high-efficiency lasing in an amplifier configuration. Details of the design and an accelerator performance analysis will be presented.