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Anderson, S. G.

Paper Title Page
MOPAS045 Fiber-Based, Spatially and Temporally Shaped Picosecond UV Laser for Advanced RF Gun Applications 533
 
  • M. Shverdin, S. G. Anderson, C. P.J. Barty, M. Betts, D. J. Gibson, F. V. Hartemann, J. Hernandez, M. Johnson, I. Jovanovic, D. P. McNabb, M. J. Messerly, J. A. Pruet, C. Siders, A. M. Tremaine
    LLNL, Livermore, California
 
  Funding: This work was performed under auspices of the U. S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7504-Eng-48.

The fiber-based, spatially and temporally shaped, picosecond UV laser system described here has been specifically designed for advanced rf gun applications, with a special emphasis on the production of high-brightness electron beams for free-electron lasers and Compton scattering light sources. The laser pulse can be shaped to a flat-top in both space and time with a duration of 10 ps FWHM and rise and fall times under 1 ps. The pulse energy is 100 micro-joules at 261.75 nm and the spot size diameter of the beam at the photocathode measures 2 mm. A fiber oscillator and amplifier system generates a chirped pump pulse at 1047 nm; stretching is achieved in a chirped fiber Bragg grating. A single multi-layer dielectric grating based compressor recompresses the input pulse to 250 fs FWHM and a two stage harmonic converter frequency quadruples the beam. A custom-designed diffractive optic reshapes the input pulse to a flat-top. Temporal shaping is achieved with a Michelson-based ultrafast pulse stacking device with nearly 100% throughput. The integration of the system, as well as preliminary electron beam measurements will be discussed.

 
TUPMS028 Commissioning of a High-Brightness Photoinjector for Compton Scattering X-Ray Sources 1242
 
  • S. G. Anderson, C. P.J. Barty, D. J. Gibson, F. V. Hartemann, M. J. Messerly, M. Shverdin, C. Siders, A. M. Tremaine
    LLNL, Livermore, California
  • H. Badakov, P. Frigola, A. Fukasawa, B. D. O'Shea, J. B. Rosenzweig
    UCLA, Los Angeles, California
 
  Funding: This work was performed under the auspices of the U. S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Compton scattering of intense laser pulses with ultra-relativistic electron beams has proven to be an attractive source of high-brightness x-rays with keV to MeV energies. This type of x-ray source requires the electron beam brightness to be comparable with that used in x-ray free-electron lasers and laser and plasma based advanced accelerators. We describe the development and commissioning of a 1.6 cell RF photoinjector for use in Compton scattering experiments at LLNL. Injector development issues such as RF cavity design, beam dynamics simulations, emittance diagnostic development, results of sputtered magnesium photo-cathode experiments, and UV laser pulse shaping are discussed. Initial operation of the photoinjector is described and transverse phase space measurements are presented.

 
TUPMS029 Gamma-Ray Compton Light Source Development at LLNL 1245
 
  • F. V. Hartemann, S. G. Anderson, C. P.J. Barty, D. J. Gibson, C. Hagmann, M. Johnson, I. Jovanovic, D. P. McNabb, M. J. Messerly, J. A. Pruet, M. Shverdin, C. Siders, A. M. Tremaine
    LLNL, Livermore, California
 
  Funding: This work was performed under the auspices of the U. S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

A new class of tunable, monochromatic gamma-ray sources capable of operating at high peak and average brightness is currently being developed at LLNL for nuclear photo-science and applications. These novel systems are based on Compton scattering of laser photons by a high brightness relativistic electron beam produced by an rf photoinjector. Key technologies, basic scaling laws, and recent experimental results will be presented, along with an overview of future research and development directions.

 
TUPMS030 Optimal Design of a Tunable Thomson-Scattering Based Gamma-Ray Source 1248
 
  • D. J. Gibson, S. G. Anderson, C. P.J. Barty, S. M. Betts, F. V. Hartemann, I. Jovanovic, D. P. McNabb, M. J. Messerly, J. A. Pruet, M. Shverdin, C. Siders, A. M. Tremaine
    LLNL, Livermore, California
 
  Funding: This work was performed under the auspices of the U. S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Thomson-Scattering based systems offer a path to high-brightness high-energy (> 1 MeV) x-ray & gamma-ray sources due to their favorable scaling with electron energy. LLNL is currently engaged in an effort to optimize such a device, dubbed the "Thomson-Radiated Extreme X-Ray" (T-REX) source, targeting up to 680 keV photon energy. Such a system requires precise design of the interaction between a high-intensity laser pulse and a high-brightness electron beam. Presented here are the optimal design parameters for such an interaction, including factors such as the collision angle, focal spot size, optimal bunch charge and laser intensity, pulse duration, and laser beam path. These parameters were chosen based on extensive modelling using PARMELA and in-house, well-benchmarked scattering simulation codes. Also discussed are early experimental results from the newly commissioned system.

 
TUPMS031 High-energy Picosecond Laser Pulse Recirculation for Compton Scattering 1251
 
  • I. Jovanovic, S. G. Anderson, C. P.J. Barty, C. G. Brown, D. J. Gibson, F. V. Hartemann, J. Hernandez, M. Johnson, D. P. McNabb, M. J. Messerly, J. A. Pruet, M. Shverdin, C. Siders, A. M. Tremaine
    LLNL, Livermore, California
 
  Funding: This work was performed under the auspices of the U. S Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Frequency upconversion of laser-generated photons by inverse Compton scattering for applications such as nuclear spectroscopy and gamma-gamma collider concepts on the future ILC would benefit from an increase of average source brightness. The primary obstacle to higher average brightness is the relatively small Thomson scattering cross section. It has been proposed that this limitation can be partially overcome by use of laser pulse recirculation. The traditional approach to laser recirculation entails resonant coupling of low-energy pulse train to a cavity through a partially reflective mirror.* Here we present an alternative, passive approach that is akin to "burst-mode" operation and does not require interferometeric alignment accuracy. Injection of a short and energetic laser pulse is achieved by placing a thin frequency converter, such as a nonlinear optical crystal, into the cavity in the path of the incident laser pulse. This method leads to the increase of x-ray/gamma-ray energy proportional to the increase in photon energy in frequency conversion. Furthermore, frequency tunability can be achieved by utilizing parametric amplifier in place of the frequency converter.

* G. Klemz, K. Monig, and I. Will, "Design study of an optical cavity for a future photon-collider at ILC", Nucl. Instrum. Meth. A 564, 212-224 (2006).

 
TUPMS035 The FINDER Photoinjector 1260
 
  • A. Fukasawa, H. Badakov, E. Hemsing, B. D. O'Shea, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • S. G. Anderson
    LLNL, Livermore, California
 
  The FINDER project at LLNL is an inverse-Compton scattering demonstration, aimed at creating MeV-class, narrow band photons for interrogation of nuclear materials. The requirements experiment requires a state-of-the-art photoinjector. Such a device is under development by a UCLA/LLNL collaboration. We report on a number of design innovations, such as photocathode gun RF symmetrization and large mode separation, which sets this device apart from previous generations of the BNL/SLAC/UCLA 1.6 cell gun. Measurements characterizing the RF photocathode gun and emittance compensation solenoid are presented.