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Dunning, M. P.

Paper Title Page
MOOAAB02 Experimental Results with the SPARC Emittance-meter 80
  • M. Ferrario, D. Alesini, M. Bellaveglia, S. Bertolucci, R. Boni, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, M. Incurvati, C. Ligi, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario
    INFN/LNF, Frascati (Roma)
  • A. Bacci, S. Cialdi, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • L. Catani, E. Chiadroni, A. Cianchi
    INFN-Roma II, Roma
  • A. M. Cook, M. P. Dunning, P. Frigola, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • L. Giannessi, M. Quattromini, C. Ronsivalle
    ENEA C. R. Frascati, Frascati (Roma)
  • P. Musumeci, M. Petrarca
    INFN-Roma, Roma
  The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive a SASE-FEL in the visible light. As a first stage of the commissioning a complete characterization of the photoinjector has been done with a detailed study of the emittance compensation process downstream the gun-solenoid system. For this purpose a novel beam diagnostic device, called emittance meter, has been developed and used at SPARC. This device has allowed to measure the evolution of beam sizes, energy spread and rms transverse emittances at different location along the beamline, in the region where space-charge effects dominate the electron dynamics and the emittance compensation process takes place. In this paper we report our commissioning experience and the results obtained. In particular a comparison between the performances of a Gaussian laser pulse versus a Flat Top laser pulse will be discussed. We report also the first experimental observation of the double emittance minima effect on which is based the optimised matching with the SPARC linac.  
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TUPMS033 Chicane Radiation Measurements with a Compressed Electron Beam at the BNL ATF 1254
  • G. Andonian, R. B. Agustsson, A. M. Cook, M. P. Dunning, E. Hemsing, A. Y. Murokh, S. Reiche, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Babzien, K. Kusche, R. Malone, V. Yakimenko
    BNL, Upton, Long Island, New York
  The radiation emitted from a chicane compressor has been studied at the Brookhaven National Laboratory (BNL) Accelerator Test Facility (ATF). Coherent edge radiation (CER)is emitted from a compressed electron beam as it traverses sharp edge regions of a magnet. The compression is accompanied by strong self-fields, which are manifested as distortions in the momentum space called beam bifurcation. Recent measurements indicate that the bunch length is approximately 100 fs rms. The emitted THz chicane radiation displays strong signatures of CER. This paper reports on the experimental characterization and subsequent analysis of the chicane radiation measurements at the BNL ATF with a discussion of diagnostics development and implementation. The characterization includes spectral analysis, far-field intensity distribution, and polarization effects. Experimental data is benchmarked to a custom developed start-to-end simulation suite.  
TUPMS034 Seeded VISA: A 1064 nm Laser-Seeded FEL Amplifier at the BNL ATF 1257
  • M. P. Dunning, G. Andonian, E. Hemsing, S. Reiche, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • M. Babzien, V. Yakimenko
    BNL, Upton, Long Island, New York
  An experimental study of a seeded free electron laser (FEL) using the VISA undulator and a Nd:YAG seed laser will be performed at the Accelerator Test Facility at Brookhaven National Laboratory. The study is motivated by the demand for a short Rayleigh length FEL amplifier at 1 micron for high power transmission with minimal damage of transport optics. Planned measurements include transverse and longitudinal coherence, angular distribution, and wavelength spectrum of the FEL radiation. The effects of detuning the electron beam energy will be studied, with an emphasis on control of the radiation emission angles and increase of the amplifier efficiency. Results of start-to-end simulations will be presented with preliminary experimental results.  
WEPMS034 Mitigation of Electric Breakdown in an RF Photoinjector by Removal of Tuning Rods in High-Field Regions 2415
  • A. M. Cook, M. P. Dunning, J. B. Rosenzweig, K. M. Serratto
    UCLA, Los Angeles, California
  • P. Frigola
    RadiaBeam, Los Angeles, California
  Funding: United States Department of Energy

The pi-mode resonant frequency of the 1.6 cell SLAC/BNL/UCLA style RF photoinjector electron gun is conventionally tuned using cylindrical copper tuning pieces that extend into the full-cell cavity through holes in the side of the gun. This design begins to fail in many versions of this popular gun design at higher voltage levels, when the cavity undergoes electric breakdown in the vicinity of the tuners. In order to remove the tuners from the region of high electric field, mitigating this problem, the full cell geometry must be changed significantly. We report on a method of accomplishing this, in which we use a mechanical device of custom design to stretch the cavity structure of an existing photoinjector in order to tune the resonant frequency up by over 2 MHz. We present results of testing the modified photoinjector in an RF test bed with both copper and magnesium cathodes, succeeding in putting approximately 8 - 10 MW of RF power into the gun. This is an improvement over the 4 MW routinely achieved in a similar gun using conventional tuning methods installed at the UCLA Neptune laboratory.

THPMS021 Optimum Electron Bunch Creation in a Photoinjector Using Space Charge Expansion 3044
  • J. B. Rosenzweig, A. M. Cook, M. P. Dunning, R. J. England, P. Musumeci
    UCLA, Los Angeles, California
  • M. Bellaveglia, M. Boscolo, G. Di Pirro, M. Ferrario, D. Filippetto, G. Gatti, L. Palumbo, C. Vicario
    INFN/LNF, Frascati (Roma)
  • L. Catani, A. Cianchi
    INFN-Roma II, Roma
  • S. M. Jones
    Jet Propulsion Laboratory, Pasadena, California
  Recent studies have shown that by illuminating a photocathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped electron bunch can be dynamically formed. Linear space-charge fields then exist in all dimensions inside of the bunch, which minimizes emittance growth. Here we study this process, and its marriage to the standard emittance compensation scenario that is implemented in most modern photoinjectors. We show that the two processes are compatible, with simulations indicating that a very high brightness beam can be obtained. An initial time-resolved experiment has been performed at the SPARC injector in Frascati, involving Cerenkov radiation produced at an aerogel. We discuss the results of this preliminary experiment, as well as plans for future experiments to resolve the ellipsoidal bunch shape at low energy. Future measurements at high energy based on fs resolution RF sweepers are also discussed.