Benson, S.V.
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| MOOB004 | Recent Results from the IR Upgrade FEL at Jefferson Lab | |
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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 |
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| MOPP053 | Incorporation of a PbSe Array Based Spectrograph into EPICS using LabView at the JLab FEL Facility | 180 |
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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 Lab, and by DOE Contract DE-AC05-84ER40150. A real-time spectrograph with a 1Hz update rate was designed and installed at the JLab FEL facility using a Cal Sensors PbSe array and a Roper Scientific SpectraPro 300 monochrometer. This paper describes the implementation of EPICS channel access on a remote PC running LabView with modification of vendor supplied LabView VI's to allow display of FEL light spectra in real-time on a remote workstation. This allows PC based diagnostics to be used in EPICS |
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| MOPP054 | Electron Gun and Injector Designs for State-of-the-Art FELs | |
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Funding: This work is supported by the Naval Sea Systems Command, the Office of Naval Research, the DoD Joint Technology Office, the Missile Defense Agency and the US Department of Energy. Reliable, high-brightness, high-power injector operation is a critical technology issue for energy recovery linac drivers of high-power free electron lasers (FEL). Advanced Energy Systems is involved in three ongoing injector programs that target up to 0.5 Ampere current levels at emittance values consistent with the requirements of the FEL. One is a DC photocathode gun and superconducting RF (SRF) booster cryomodule. A 748.5 MHz injector of this type is being assembled and will be tested up to 100 mA at the Thomas Jefferson National Accelerator Facility (JLAB) beginning in 2007. The second approach being explored is a high-current normal-conducting RF photoinjector. A 700 MHz gun, presently under fabrication, will undergo thermal test in 2006 at Los Alamos National Laboratory (LANL). Finally, a half-cell 703.75 MHz SRF gun is presently being designed and will be tested to 0.5 Ampere at Brookhaven National Laboratory (BNL) in 2007. The status and projected performance for each of these injector projects is presented. |
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| TUOA001 | Design Challenges in High Power Free-Electron Laser Oscillators | |
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Funding: This work supported by The Office of Naval Research the Joint Technology Office, NAVSEA PMS-405, the Air Force Research Laboratory, U.S. Army Night Vision Lab, the Commonwealth of Virginia, and by DOE Contract DE-AC05-84ER40150. Several FELs have now demonstrated high power lasing and several projects are under construction to deliver higher power or shorter wavelengths. This presentation will summarize progress in upgrading FEL oscillators towards higher power and will discuss some of the challenges these projects face. The challenges fall into three categories: 1. energy recovery with large exhaust energy spread, 2. output coupling and maintaining mirror figure in the presence of high intracavity power loading, and 3. high current operation in an energy recovery linac (ERL). Progress in all three of these areas has been made in the last year. Energy recovery of over 12% of exhaust energy spread has been demonstrated and designs capable of accepting even larger energy spreads have been proposed. Cryogenic transmissive output couplers for narrow band operation and both hole and scraper output coupling have been developed. Investigation of short Rayleigh range operation has started as well. Energy recovery of over 20 mA CW has been demonstrated and several methods of mitigating transverse beam breakup instabilities were demonstrated. This talk will summarize these achievements and give a roadmap of where the field is headed. |
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| TUPP042 | High Power CW Operation of a Hole-Outcoupled Free-Electron Laser | |
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Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Army Night Vision Laboratory, the Air Force Research Laboratory, the Commonwealth of Virginia, and by DOE Contract DE-AC05-84ER40150. In order to provide widely-tunable light to our users, we used a hole outcoupler. To date, we've produced 85 W at 2.8 microns, and been able to continuously tune over a 1 micron spectral range. Besides the anticipated low outcoupling efficiency associated with this scheme, we found that we had considerable problems stabilizing the output when we operated our FEL in cw mode. We believe that this is due to the long time available for mode competition to develop. Measurements of gain, loss, and transverse mode profiles (both intracavity and output) will be compared with our models. |
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| TUPP058 | Calculations and Mitigation of THz Mirror Heating at the Jefferson Lab FEL | |
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Funding: This work supported by the US Army Night Vision Lab, ONR, JTO, the Commonwealth of Virginia, the Air Force Research Laboratory, and DOE Contract DE-AC05-84ER40150. We thank Fred Dylla for his expert advice and encouragement. Short bunches of electrons in the Jefferson Lab FEL emit multiparticle coherent edge radiation as they enter the dipole prior to the outcoupler mirror. This light is more collimated than synchrotron light and furthermore is modified by interference from the last chicane magnet after the high reflector. This light provides an additional heat load on the outcoupler in a wavelength range it was not designed to handle. We have performed calculations of this effect using a new extension of the Synchrotron Radiation Workshop code which, importantly, takes into account both acceleration and velocity (or Coulomb) terms of the emitted electric field. We have also measured THz properties of some of the mirrors. We show how the addition of a decompression chicane mitigates these problems. |
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| THPP069 | Laser Safety System for the IR Upgrade FEL at Jefferson Lab | |
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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. |
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| THPP070 | Temporal Characterization of Electron Beam Bunches with a Fast Streak Camera at the JLab FEL Facility | 640 |
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Funding: This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the Army Night Vision Laboratory, the Air Force Research Laboratory, and by DOE Contract DE-AC05-84ER40150. The design and construction of an optical transport that brings synchrotron radiation from electron bunches to a fast streak camera in a remote area has become a useful tool for online observation of bunch length and stability. This paper will report on the temporal measurements we have done, comparison with simulations, and the on-going work for another imaging optical transport system that will make possible the direct measurement of the longitudinal phase space by measuring the bunch length as a function of energy. |
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