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TUAAU04 |
On the Design Implications of Incorporating an FEL in an ERL
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273 |
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- G. Neil, S. V. Benson, D. Douglas, P. Evtushenko, T. Powers
Jefferson Lab, Newport News, Virginia
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Encouraged by the successful operation of the JLab Demo in 1998, many high current ERLs are now being designed with not only short pulse synchrotron beamlines but also FELs. Such inclusion has major implications on magnet quality, rf feedback requirements, wiggler design, srf cavity QL, halo, etc. Measurements on the JLab ERL FEL have identified new challenges. The JLab Upgrade was designed with a 160 MeV beam of 10 mA in 75 MHz, 300 fs bunches. FEL designers set transverse emittance and longitudinal bunching, but to accommodate an FEL in our ERL also means setting stringent phase stability requirements of (<6x10-9/fm rms) based on a desired FEL detuning tolerance of 1.2 microns. Recovered beam RF loading on the subsequent accelerated beam complicates satisfying these requirements. Gain in the rf feedback limits the accuracy of energy stability when loaded Qs are ~107 . Energy recovery to <10 MeV sets magnetic field tolerances at 10-4. We present measurements on the JLab ERL showing how to set system requirements to tolerate such FEL lasing.
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Slides
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Talk
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TUPPH009 |
A Design Study of a FIR/THz-FEL for High Magnetic Field Research
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327 |
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- M. Tecimer, L. C. Brunel, J. van Tol
NHMFL, Tallahassee, Florida
- G. Neil
Jefferson Lab, Newport News, Virginia
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Presently a conceptual design work for a NIR-FIR FEL system at the NHMFL/FSU is being undertaken. The system is intended to combine high magnetic field research with an intense, tuneable photon source, spanning the spectral region ~21000 microns. Here, we present a design study involving the FIR/THz part of the NHMFL FEL design proposal. The suggested long-wavelength FEL encompasses in the first phase a thermionic injector (similar to that in use at the Forschungszentrum-Rossendorf ELBE facility) with a planned ~2 mA average current and a ~10 MeV superconducting rf linac module operating at 1.3 GHz. The broadband outcoupling over the envisaged FIR/THz spectral range (1001100 microns) is accomplished by adopting a single (variable height slot) outcoupler in a waveguided cavity. Besides the performance predictions of the suggested long-wavelength FEL, techniques for the generation of high peak power, nanoseconds long THz pulses (for magnetic resonance applications) are also reported.
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TUPPH061 |
Phase Noise Comparision of Short Pulse Laser Systems
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466 |
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- S. Zhang, S. V. Benson, J. Hansknecht, D. Hardy, G. Neil, M. D. Shinn
Jefferson Lab, Newport News, Virginia
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This paper describes the phase noise measurement on several different mode-locked laser systems that have completely different gain media and configurations including a multi-kW free-electron laser. We will focus on the state of the art short pulse lasers, especially the drive lasers for photocathode injectors. A comparison between the phase noise of the drive laser pulses, electron bunches and FEL pulses will also be presented.
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THPPH064 |
Bunch Length Measurements at JLab FEL
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736 |
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- P. Evtushenko, J. L. Coleman, K. Jordan, J. M. Klopf, G. Neil, G. P. Williams
Jefferson Lab, Newport News, Virginia
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The JLab FEL is routinely operated with sub-picosecond bunches. The short bunch length is important for high gain of the FEL. Coherent transition radiation has been used for the bunch length measurements for many years. This diagnostic can be used only in the pulsed beam mode. It is our goal to run FEL with CW beam and 74.85 MHz micropulse repetition rate. Hence it is very desirable to have the possibility of doing the bunch length measurements when running CW beam with any micropulse frequency. We use a Fourier transform infrared interferometer, which is essentially a Michelson interferometer, to measure the spectrum of the coherent synchrotron radiation generated in the last dipole of the magnetic bunch compressor upstream of the FEL wiggler. This noninvasive diagnostic provides the bunch length measurements for CW beam operation at any micropulse frequency. We also compare the measurements made with the help of the FTIR interferometer with the data obtained by the Martin-Puplett interferometer. Results of the two diagnostics are usually agree within 15%. Here we present a description of the experimental setup, data evaluation procedure and results of the beam measurements.
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THPPH066 |
Longitudinal Phase Space Characterization of Electron Bunches At the JLab FEL Facility
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740 |
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- S. Zhang, S. V. Benson, D. Douglas, D. Hardy, G. Neil, M. D. Shinn
Jefferson Lab, Newport News, Virginia
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We report the latest measurement of the longitudinal phase space of electron bunches on our 10kW free-electron laser facility. The design and construction of an all reflective optical transport has made it possible to make full use of broadband synchrotron radiation and perform a high-efficiency dispersion-free measurement with a remote fast streak camera. The evolution of the longitudinal phase space can be observed live when the accelerating RF phase is tuned. The results for different beam setups including low and high current will be presented.
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