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An Experimental Study of an FEL Oscillator with a Linear Taper

Description: Motivated by the work of Saldin, Schneidmiller and Yurkov, we have measured the detuning curve widths, spectral characteristics, efficiency, and energy spread as a function of the taper for low and high Q resonators in the IR Demo FEL at Jefferson Lab. Both positive and negative tapers were used. Gain and frequency agreed reasonably well with the predictions of a single mode theory. The efficiency agreed reasonably well for a negative taper with a high Q resonator but disagreed for lower Q values due to the large slippage parameter and the non-ideal resonator Q. We saw better efficiency for a negative taper than for the same positive taper. The energy spread induced in the beam, normalized to the efficiency is larger for the positive taper than for the corresponding negative taper. This indicates that a negative taper is preferred over a positive taper in an energy recovery FEL.
Date: January 1, 2001
Creator: Benson, S.; Gubeli, J. & Neil, G.R.
Partner: UNT Libraries Government Documents Department

Second Harmonic FEL Oscillation

Description: We have produced and measured for the first time second harmonic oscillation in the infrared region by the high average power Jefferson Lab Infrared Free Electron Laser. Although such lasing is ideally forbidden, since gain is zero on axis for a perfect electron beam in an infinite wiggler, the finite geometry and beam emittance allows sufficient gain for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 watts average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM01 mode. We present results of initial source performance measurements and comparisons of gain as calculated by different approaches.
Date: September 1, 2001
Creator: Neil, George R.; Benson, S.V.; Biallas, G.; Freund, H.P.; Gubeli, J.; Jordan, K. et al.
Partner: UNT Libraries Government Documents Department

Lasing in Forbidden Regions: Second Harmonic FEL Oscillation

Description: We have produced and measured for the first time second harmonic oscillation in the infrared region by the high average power Jefferson Lab Infrared Free Electron Laser. Although such lasing is ideally forbidden, since gain is zero on axis for a perfect electron beam in an infinite wiggler, the finite geometry allows sufficient gain in this situation for lasing to occur. We were able to lase at pulse rates up to 74.85 MHz and could produce over 4.5 watts average and 40 kW peak of IR power in a 40 nm FWHM bandwidth at 2925 nm. In agreement with predictions, the source preferentially lased in a TEM-01 mode. We present results of initial source performance measurements and comparisons of gain as calculated by different approaches.
Date: March 1, 2001
Creator: Neil, G.R.; Benson, S.V.; Biallas, G.; Gubeli, J.; Jordan, K.; Myers, S. et al.
Partner: UNT Libraries Government Documents Department

THE JLAMP VUV/SOFT X-RAY USER FACILITY AT JEFFERSON LABORATORY

Description: Jefferson Lab (JLab) is proposing JLAMP (JLab Amplifier), a 4th generation light source covering the 10-100 eV range in the fundamental mode with harmonics stretching towards the oxygen k-edge. The new photon science user facility will feature a two-pass superconducting LINAC to accelerate the electron beam to 600MeV at repetition rates of 4.68MHz continuous wave. The average brightness from a seeded amplifier free electron laser (FEL) will substantially exceed existing light sources in this device's wavelength range, extended by harmonics towards 2 nm. Multiple photon sources will be made available for pump-probe dynamical studies. The status of the machine design and technical challenges associated with the development of the JLAMP are presented here.
Date: May 1, 2010
Creator: Benson, S.V.; Douglas, D.; Evtushenko, P.; Gubeli, J.; Hannon, F.E.; Jordan, K. et al.
Partner: UNT Libraries Government Documents Department

First operation of an FEL in same-cell energy recovery mode

Description: The driver for Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers 75% of the electron-beam power and converts it to radio frequency power. As reported in FEL'98, the accelerator operated ''straight-ahead'' to deliver 38 MeV, 1.1 mA cw current for lasing at wavelengths in the vicinity of 5 microns. The waste beam was sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. The machine has now recirculated cw average current up to 4.6 mA and has lased cw with energy recovery up to 1,720 W output at 3.1 microns. This is the first FEL to ever operate in the ''same-cell'' energy recovery mode. Energy recovery offers several advantages (reduced RF power and dramatically reduced radio-nuclide production at the dump) and several challenges will be described. The authors have observed heating effects in the mirrors which will be described. They will also report on the additional performance measurements of the FEL that have been performed and connect those measurements to standard models.
Date: September 1, 1999
Creator: Neil, G.R.; Benson, S.; Biallas, G.; Bohn, C.L.; Douglas, D.; Dylla, H.F. et al.
Partner: UNT Libraries Government Documents Department

Sustained Kilowatt Lasing in a Free-Electron Laser with Same Cell Energy Recovery

Description: TJNAF recently commissioned its high-average-power infrared free-electron laser (FEL). It incorporates a superconducting accelerator that recovers about 75% of the electron-beam power and converts it to radio-frequency power. In achieving first lasing, the accelerator operated straight-ahead to deliver 38 MeV, 1.1 mA cw average current through the wiggler for lasing at wavelengths near 5 {micro}m. The waste beam was then sent directly to a dump. Stable operation at up to 311 W cw was achieved in this mode. Using a transport loop to send the waste electron beam back to the linac for energy recovery, the machine recently lased cw at up to 1720 W average power at 3.1 {micro}m, for which the electron-beam energy and average current were 48 MeV and 4.4 mA, respectively.
Date: September 1, 1999
Creator: Neil, G.R.; Benson, S.; Biallas, G.; Bohn, C.L.; Douglas, D.; Dylla, H.F. et al.
Partner: UNT Libraries Government Documents Department

Status of the Jefferson Lab IR/UV High Average Power Light Source

Description: Jefferson Lab is in the process of building an upgrade to our Free-Electron Laser Facility with broad wavelength range and timing flexibility. The facility will have two cw free-electron lasers, one in the infrared operating from 1 to 14 microns and one in the infrared operating from 0.25 to 1 micron [1]. In addition, there will be beamlines for Thompson-backscattered femtosecond X-rays, and broadband THz radiation. The average power levels for each of these devices will exceed any other available sources by at least 2 orders of magnitude. Timing of the available laser pulses can be continuously mode-locked at least 4 different (MHz) repetition rates or in macropulse mode with pulses of a few microseconds in duration with a repetition rate of many kHz. The status of the construction of this facility and a review of its capabilities will be presented.
Date: September 2002
Creator: Neil, G. R.; Benson, S. V.; Biallas, G.; Boyce, J.; Dillon-Townes, L. A.; Douglas, D. et al.
Partner: UNT Libraries Government Documents Department

The Jefferson Lab Sub-picosecond X-ray Program

Description: The kW-class infrared (IR) Free Electron Laser (FEL) at Jefferson Lab had the capability of producing intracavity Thomson scattering of the IR off the electron beam thus producing high average flux, sub-picosecond x-rays. We have measured these x-rays and demonstrated the energy tuneability range from 3.5 keV to 18 keV. The corresponding flux and brightness has been estimated and will be discussed. This year, 2002, the FEL was disassembled and has been reconfigured to produce 10 kW average power IR. We present the estimated x-ray capabilities for the new FEL and discuss potential applications.
Date: November 1, 2002
Creator: Boyce, J.R.; Benson, S.V.; Bohn, C.L.; Douglas, D.R.; Dylla, H.F.; Gubeli, J.F. et al.
Partner: UNT Libraries Government Documents Department