This abstract was not submitted electronically.
[D13.02] Short Wavelength SASE Experiments at BNL
X.J. Wang (National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973)
It is now widely recognized in both free electron laser (FEL) and synchrotron light source community that, next generation light source most likely will be FEL based X-ray and UV coherent source. Self Amplified Spontaneous Emission (SASE) and High Gain Harmonic Generation (HGHG) are two most promising candidates for UV to X-ray FELs. National synchrotron light source of Brookhaven National Laboratory has been actively pursuit research in both SASE and HGHG FELs in the past decade. As part of US national experimental effort of proof-of-principle for SASE and HGHG fels, several demonstrational experiments are now underway at the Brookhaven Accelerator Test Facility (ATF) and NSLS Source Development Laboratory (SDL) for SASE and HGHG FELs for wavelength range from near IR to UV.
SASE at wavelength 1064 nm and 633 nm were observed using MIT microwiggler at ATF for electron beam energies of 34 MeV and 48 MeV. For 1064 nm radiation, enhancement of emission from 2 to 6 times of the spontaneous emission were measured. In collaboration with ANL APS, a SASE FEL for 5 to 10 micrometer using a two meter long wiggler is now installed at the ATF. For a 40 MeV electron beam produced by the ATF photocathode RF gun (Normalized rms emittance 2.5 mm-mrad, peak current more than 200 A), several orders of magnitude gain in SASE is expected. We intend to carry out detailed studies of SASE FELs, such as gain length as function of electron beam parameters, start-up noise and angular divergence of the SASE radiation
[D13.03] RAFEL: a SASE Experiment with Feedback
Dinh Nguyen (Los Alamos National Laboratory)
We report the first experimental demonstration in the infrared of the Regenerative Amplifier FEL (RAFEL), a self-amplified spontaneous emission (SASE) experiment with feedback. We show that by re-injecting less than 10 percent of the optical power, we can achieve optical saturation in a few passes. By varying the beam current, we can also obtain the effective number of gain lengths and thus determine the exponential gain. The SASE results showed a single-pass gain of more than 500 and an enhancement of 60 over spontaneous undulator radiation. With feedback, the optical power grew by six orders of magnitude above the SASE signal and achieved saturation in less than ten passes. The highest energy achieved in each micropulse was 0.5 mJ, corresponding to a peak optical power of 50 MW. This new FEL has operated at high peak power without optical damage to the feedback optics.
[D13.04] 3-D Effects in SASE Start-Up
Kwang-Je Kim (Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439)
The physical process of initial spontaneous undulator radiation evolving to an exponentially growing self-amplified spontaneous emission (SASE) is reviewed, with an emphasis on 3-D effects. A clear understanding of the 3-D effects due to diffraction, betatron motion and finite bunch length is necessary for a correct interpretation of the present on-going proof-of-principle SASE experiments at infrared wavelengths and for predicting the performance of the proposed x-ray SASE machines.
[D13.05] New Developments in High-Brightness Electron Sources
Dennis Thomas Palmer (SLAC/Stanford University)
The present state of the art in emittance compensated rf photoinjector designs will be presented. Simulations and/or experimental results from both proposed and operational emittance compensated rf photoinjectors, operating, in the frequency ranges of L-band (1.424 GHz) to X-band (11.424 GHz), will be presented.
Both simulations and experimental beam dynamics results of the L-Band AFEL will be presented as they relate to resent SASE results in the IR.
PARMELA simulation will be compared to experimental results of the BNL/SLAC/UCLA 1.6 cell emittance compensated S-band rf photoinjector. Reasonable agreement is found between PARMELA and experimental results for the normalized rms transverse emittance. With respect to the longitudinal emittance, PARMELA simulations do not predict the experimental measured electron bunch length.
Beam dynamics simulations and low level rf cold test results will be presented for a novel integrated X-band emittance compensated photoinjector will also be presented.
Future research directions will be discussed that could possibly allow for the production and measurements of high charge low emittance beams necessary for X-ray FELs, such as SLAC's LCLS or the TTF FEL.
[D13.06] Advanced beam diagnostics for SASE FEL experiments
James Rosenzweig (UCLA Dept. of Physics and Astronomy)
The electron beams used in SASE free-electron laser experiments are characterized by very high brightness, meaning high charge, low emittance, and pulse lengths of picoseconds. These beams are typically created in photoinjectors, an environment where large acceleration and focusing fields are used to control the beam's plasma behavior, which leads to pulse lengthening and/or emittance growth. In order to produce the beam quality for next-generation SASE FELS, and measure the effects of the SASE process on the electron beam itself, diagnostics are undergoing vigorous development. In this talk we discuss recent advances in beam diagnostics at UCLA. We examine transverse diagnostics such transport matrix measurements in high field systems, and emittance measurements methods such as quadrupole scans and pepper pots, which must extract information about ultra-low temperature beam distributions in the presence of large space-charge fields. Subpicosecond-resolution, longitudinal diagnostics discussed include in coherent radiation-based diagnosis of single bunches, and SASE-induced microbunch trains with bunch spacing in the near infra-red to optical range.