Session: TUBxS - 31 Aug 2004
FEL Technology II

TUBIS01 Attosecond X-ray Pulses in the LCLS using the Slotted Foil Method
Paul J Emma, Zhirong Huang (SLAC, Menlo Park, California), Michael Borland (ANL/APS, Argonne, Illinois)

A proposal has been made to generate femtosecond and sub-femtosecond x-ray pulses in the Linac Coherent Light Source (LCLS) SASE FEL by using a slotted spoiler foil located at the center of the second bunch compressor chicane. This previous study highlighted a simple case, using the nominal LCLS parameters, to produce a 2-fsec fwhm, 8-keV x-ray pulse. The study also pointed out the possibility of attaining sub-femtosecond pulses by somewhat modifying the LCLS compression parameters, but did not undertake a full tracking simulation for this more aggressive case. We take the opportunity here to study this `attosecond' case in detail, including a full tracking simulation, pushing the limit of the technique.

TUBOS02 Longitudinal Space Charge Effects in the JLAB IR FEL SRF Linac
Carlos Hernandez-Garcia, Kevin Beard, Chris Behre, Stephen Vincent Benson, George Herman Biallas, James Boyce, David Douglas, Fred Dylla, Richard Evans, Al Grippo, Joe Gubeli, David Hardy, Kevin Jordan, Lia Merminga, George Neil, Joe Preble, Michelle D. Shinn, Tim Siggins, Richard Walker, Gwyn Williams, Byung Yunn, Shukui Zhang (Jefferson Lab, Newport News, Virginia)

Observations of energy spread asymmetry when operating the Linac on either side of crest and longitudinal emittance growth have been confirmed by extending PARMELA simulations from the injector to the end of the first SRF Linac module. The asymmetry can be explained by the interaction of the accelerating electric field with that from longitudinal space charge effects within the electron bunch. This can be a major limitation to performance in FEL accelerators.

TUBOS03 High Average Power Operation of a Scraper-Outcoupled Free-Electron Laser
Michelle D. Shinn, Chris Behre, Stephen Vincent Benson, Michael Bevins, Don Bullard, James Coleman, L. Dillon-Townes, Tom Elliott, Joe Gubeli, David Hardy, Kevin Jordan, Ronald Lassiter, George Neil, Shukui Zhang (Jefferson Lab, Newport News, Virginia)

We describe the design, construction, and operation of a high average power free electron laser using scraper outcoupling. Using the FEL in this all-reflective configuration, we achieved approximately 2 kW of stable output at 10 um. Measurements of gain, loss, and output mode will be compared with our models.

TUBOS04 LCLS Undulator Design Development
Isaac Vasserman, Roger J. Dejus, Patric Den Hartog, Elizabeth Moog, Shigemi Sasaki, Emil Trakhtenberg, Marion White (ANL/APS, Argonne, Illinois)

The fractional variation in deflection parameter K between segments of the 130.4-m-long undulator line for the Linac Coherent Light Source (LCLS) must be < 1.5 x 10-4. Mechanical shims were used to set the undulator gap to control K in the prototype, but this is too tedious a procedure to be used for all 33 undulator segments. Although the prototype undulator met all of the LCLS specifications, development continued in order to simplify the system. Various other alternatives for adjusting the field were considered. A canted-pole geometry was adopted that allows the K value to be changed by lateral translation of the entire undulator segment. This scheme also facilitates tapering the undulator line to accommodate energy loss in the electron beam. The prototype undulator was subsequently modified to test the canted-pole concept. Magnetic measurements demonstrated that the undulator with canted poles meets all LCLS specifications, and is more cost-effective to implement.

TUBOS05 Commissioning of the TTF Linac Injector at the DESY VUV-FEL
Katja Honkavaara (DESY, Hamburg)

The upgrade of the TESLA Test Facility (TTF) Linac at DESY is almost completed. With electron beam energies up to 1 GeV, it will be able to drive a new SASE FEL user facility (VUV-FEL) in the wavelength range from VUV to soft X-rays. The first phase of the redesigned photoinjector is finished. We report on its commissioning during spring 2004, including the first measurements of electron beam parameters. Since this injector is also a prototype for the XFEL injector, the results obtained are important for future SASE XFEL drive linacs.