[Eng-div] COLLOQUIUM-December 15, 2010

[Gayle Coleman]

COLLOQUIUM

Wednesday, December 15, 2010
4pm with coffee and cookies at 3:45
Auditorium

The Dawn of Higher Energy Photon Science at Jefferson Lab - Initial
Lasing results from the UV Demo Free-Electron Laser

Michelle Shinn and Steve Benson

The Jefferson Lab FEL facility was always envisioned as having both an
infrared and an ultraviolet (UV) free-electron laser. Recently we have
completed the UV electron beam-line, installed the optics and started
commissioning of the UVFEL operated at both a red wavelength and in the
violet and ultraviolet region. This region is much more challenging than
the IR region due to a much greater sensitivity to the electron beam
quality and to mirror heating. We were therefore pleasantly surprised to
find that the lasing has been extremely robust, with gains of more than
100% per pass and an efficiency of almost 1%. Though mirror heating is
substantial, we have achieved over 100 Watts even at the ultraviolet
wavelength of 370 nm and 200 W at 400 nm. We are making a concerted
effort to try to match simulated results to the experimental results and
have found that reasonable agreement is found when three-dimensional
guiding effects are included in the simulations. We now plan to operate
with a hole output coupler that will allow us to push to much higher
photon energies. These runs take advantage of higher harmonic
wavelengths naturally produced in the FEL. Initial experiments are
planned to use light with a photon energy of 10 eV. In this presentation
we will discuss the experiments that motivated the construction of this
machine and outline some of the proposed experiments in the vacuum
ultraviolet.

This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the
Air Force Office of Scientific Research, DOE Basic Energy Sciences, the
Office of Naval Research, and the Joint Technology Office.


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