• S. V. Benson, K. Beard, G. H. Biallas, J. Boyce, D. B. Bullard, J. L. Coleman, D. Douglas, H. F.D. Dylla, R. Evans, P. Evtushenko, C. W. Gould, A. C. Grippo, J. G. Gubeli, D. Hardy, C. Hernandez-Garcia, C. Hovater, K. Jordan, J. M. Klopf, R. Li, S. W. Moore, G. Neil, M. Poelker, T. Powers, J. P. Preble, R. A. Rimmer, D. W. Sexton, M. D. Shinn, C. Tennant, R. L. Walker, G. P. Williams, S. Zhang
  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.

• Y. Zhang, S. A. Bogacz, P. B. Brindza, A. Bruell, L. S. Cardman, J. R. Delayen, Y. S. Derbenev, R. Ent, P. Evtushenko, J. M. Grames, A. Hutton, G. A. Krafft, R. Li, L. Merminga, J. Musson, M. Poelker, A. W. Thomas, B. Wojtsekhowski, B. C. Yunn
  Jefferson Lab, Newport News, Virginia
• V. P. Derenchuk
  IUCF, Bloomington, Indiana
• V. G. Dudnikov
  BTG, New York
• W. Fischer, C. Montag
  BNL, Upton, Long Island, New York
• P. N. Ostroumov
  ANL, Argonne, Illinois

Experiments on the study of fundamental quark-gluon structure of nucleons require an electron-light ion collider of a center of mass energy from 20 to 65 GeV at luminosity level of 10³⁵ cm^-2s-1 with both beams polarized. A CEBAF accelerator based ring-ring collider of 7 GeV electrons/positrons and 150 GeV light ions is envisioned as a possible next step after the 12 GeV CEBAF Upgrade. The developed ring-ring scheme takes advantage of the existing polarized continuous electron beam and SRF linac, the green-field design of the collider rings and the ion accelerator complex with electron cooling. We report results of our design studies of the ring-ring version of an electron-light ion collider of the required luminosity.

• R. Li
  Jefferson Lab, Newport News, Virginia

In this study, we analyze the longitudinal effective CSR force for an energy-chirped Gaussian bunch moving relativistically on a circular orbit. With the geometry of the bunch tilt in dispersive regions (as induced by the initial energy-chirp) included in the retardation relation, the longitudinal effective CSR force thus calculated displays a variety of behaviors depending on the level of bunch compression. The variety ranges from the suppression of the longitudinal CSR force, for an undercompressed thin bunch, to an enhancement of the CSR interaction above that for a projected bunch, in a duration of path length shortly after the bunch crosses over the full compression point. The amplitude and duration of the enhancement depends on the bunch and lattice parameters. During this enhancement, the longitudinal effective CSR force depends sensitively on the particle's transverse position in the bunch. The physical picture of this phenomenon will be discussed.