• S.V. Benson, K. Beard, C.P. Behre, G.H. Biallas, J. Boyce, D. Douglas, H.F.D. Dylla, R. Evans, A.G. Grippo, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, L. Merminga, G. Neil, J.P. Preble, M.D. Shinn, T. Siggins, R.L. Walker, G.P. Williams, S. Zhang
  Jefferson Lab, Newport News, Virginia
• N. Nishimori
  JAEA/FEL, Ibaraki-ken

Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, the US Army Night Vision Laboratory, and by DOE Contract DE-AC05-84ER40150.

After demonstrating 10 kW operation with 1 second pulses, the Jefferson Lab program switched to demonstrating high power operation at short wavelengths using a new 8 cm period wiggler and a THz suppression chicane. We report here on the lasing results to date using this new configuration. We have demonstrated a large reduction in THz heating on the mirrors. We have also eliminated heating in the mirror steering assemblies, making operation at high power much more stable. Finally, we have greatly reduced astigmatism in the optical cavity, allowing operation with a very short Rayleigh range. The laser has been tuned from 0.9 to 3.1 microns using the new wiggler. User experiments commenced in April of 2005 with the FEL Upgrade operating over the 1-3 micron range. We are in the process of installing a 5.5 cm permanent magnet wiggler that will give us even larger tuning range and higher power.

Corresponding author: Tel: 1-757-269-5026; fax: 1-757-269-5519; E-mail address: felman@jlab.org

• J.L. Coleman, S.V. Benson, R. Evans, A.G. Grippo, K. Jordan
  Jefferson Lab, Newport News, Virginia

Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Air Force Research Laboratory, The Army Night Vision Laboratory and by DOE Contract DEAC05-84ER40150

The Jefferson Lab FEL poses a number of challenges regarding laser safety. The IR FEL is designed to lase at powers in excess of 10 kWatt and at wavelengths from 1 to 10 microns and the UV FEL will lase at the kilowatt level from 1 micron to 250 nanometers. Additionally there are table top Class 4 lasers and a THz beam line that produces hundreds of watts. The FEL operation is further complicated by Class 4 powers in the coherent harmonics of the FEL. There are 3 modes that we operate in: alignment mode, hutch mode, and full power exclusionary. This paper describes the experience with our current Laser Safety System and the upgrades planned to allow safe operation with these many hazards.