A design for an X-band rf photoinjector that was developed jointly by SLAC National Accelerator Laboratory (SLAC) and Lawrence Livermore National Laboratory (LLNL) is presented. The photoinjector is based around a 5.59 cell rf gun that has state-of-the-art features including: elliptical contoured irises; improved mode separation; an optimized initial half cell length; a racetrack input coupler; and coupling that balances pulsed heating with cavity fill time. Radio-frequency and beam dynamics modeling have been done using a combination of codes including PARMELA, HFSS, IMPACT-T, ASTRA, and the ACE3P suite of codes developed at SLAC. The impact of lower gradient operation, magnet misalignment, solenoid multipole errors, beam offset, mode beating, wakefields, and beam line symmetry have been analyzed and are described. Fabrication and testing plans at both LLNL and SLAC are discussed.

The rf photoinjector and linear accelerator in the Mono-Energetic Gamma-ray (MEGa-ray) facility at LLNL is presented. This machine uses 11.4GHz rf technology to accelerate a high-brightness electron beam up to 250MeV to produce MeV γ-rays through Compton scattering with a Joule-class laser pulse. Compton scattering-based generation of high flux, narrow bandwidth γ-rays places stringent requirements on the performance of the accelerator. The component parts of the accelerator are presented and their requirements described. Simulations of expected electron beam parameters and the resulting light source properties are presented.

Submitted for the DPP09 Meeting of The American Physical Society 120-Hz Diode-Pumped Kilowatt Class Laser for Compton Scattering Sources ANDY BAYRAMIAN, GLENN BEER, ROB CAMPBELL, BARRY FREITAS, WILLIAM MOLANDER, STEVE SUTTON, STEVE TELFORD, CHRIS BARTY, Lawrence Livermore National Laboratory — A MonoEnergetic Gamma-Ray (MEGa-ray) Compton scattering light source is currently based on a 120-Hz electron accelerator. A 120-Hz laser source can increase the current gamma ray production by more than an order of magnitude and further enhancements are possible. Diode pumped solid state lasers (DPSSLs) offer the potential to operate at these higher repetition rates where flash lamp pumped laser systems are currently limited by thermal and lamp lifetime issues. Utilizing LLNL expertise in high energy DPSSLs, a 10-J, 120-Hz diode-pumped Nd:YAG laser architecture has been developed. The laser design makes use of advances in diode packaging, power conditioning, and beam conditioning to provide over 100-kW peak power array. Sapphire heatsinks and longitudinal cooling of the amplifier yields low parasitic loss and low wavefront distortion. An image relayed architecture and adaptive optics will yield a diffraction limited beam ideal for Compton scattering. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Andy Bayramian Lawrence Livermore National Laboratory Date submitted: 14 Jul 2009 Electronic form version 1.4

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. J. Bayramian, J. P. Armstrong, G. K. Beer, R. W. Campbell, R. R. Cross, A. C. Erlandson, B. L. Freitas, R. A. Kent, J. A. Menapace, W. A. Molander, K. I. Schaffers, C. W. Siders, S. B. Sutton, J. B. Tassano, S. Telford, J. E. Wolfe, C. A. Ebbers, J. A. Caird, and C. P. J. Barty, "Design of a 10 Hz Femto-Petawatt Laser Pumped by the Mercury Laser Facility," in Advanced Solid-State Photonics, OSA Technical Digest Series (CD) (Optica Publishing Group, 2008), paper MC1. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

A large-aperture high-average-power gas-cooled Ti:sapphire slab pumped by the Mercury laser is the final amplifier in a chirped pulse amplification chain capable of producing a compressed peak power >1 petawatt and peak intensity >1023 W/cm2.

We report on the construction, commissioning and characterization of a reactive ion mill capable of submicron pattern transfer into hard dielectric materials on optical substrates as large as 2 x 1 m, for application to fielding high-Energy Petawatt (HEPW) capability on the National Ignition Facility (NIF) laser. Scanning Faraday cup current probe measurements have been used to optimize the ion beam spatial uniformity. Using process parameters obtained from this study, an 81 cm round optic was etched, and etch depth uniformity of {+-} 3.1% absolute was demonstrated. Uniformity of multilayer dielectric gratings of designs employing an etch-stop layer will have etch depth uniformities of approximately a factor of 10 better than this. We also report on initial results of etching multilayer dielectric gratings.

In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test station is being developed to investigate accelerator optimization for future upgrades. This test station will enable work to explore the science and technology paths required to boost the current mono-energetic gamma-ray (MEGa-Ray) technology a higher effective repetition rate, potentially increasing the average gamma-ray brightness by two orders of magnitude. The test station will consist of a 5.5 cell X-band RF photoinjector, single accelerator section, and beam diagnostics. Beam quality must be exceedingly high in order to produce narrow-bandwidth gamma-rays, requiring a robust state of the art photoinjector. The photoinjector will be a high gradient (200 MV/m cathode field) standing wave structure, featuring a dual feed racetrack coupler, elliptical irises, and an optimized first cell length. Detailed design of the RF photoinjector for this test station is complete, and is presented with modeling simulations, and layout plans.