| Paper |
Title |
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| MOOAAB02 |
Experimental Results with the SPARC Emittance-meter
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80 |
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- 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
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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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Slides
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| TUPMN038 |
Coherent Cherenkov Radiation as a Temporal Diagnostic for Microbunched Beams
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998 |
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- G. Gatti
INFN/LNF, Frascati (Roma)
- A. M. Cook, J. B. Rosenzweig, R. Tikhoplav
UCLA, Los Angeles, California
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Cherenkov radiation of a relativistic e-beam traversing a thin section of aerogel is analized, putting the stress on the coherent contribution due to the intra-beam, transverse and longitudinal structure. The use of this tool as a temporal diagnostic for micro-bunched beams makes possible to improve the amount of collected power at the microbunching frequency several orders of magnitude more respect to the uncoherent Cherenkov contribution. The non-idealities of a real beam are taken in account, and some techniques aimed on enhancing the coherent part of radiation are proposed and analized analitically and through simulation codes.
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| TUPMS033 |
Chicane Radiation Measurements with a Compressed Electron Beam at the BNL ATF
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1254 |
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- 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
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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.
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| WEPMS034 |
Mitigation of Electric Breakdown in an RF Photoinjector by Removal of Tuning Rods in High-Field Regions
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2415 |
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- A. M. Cook, M. P. Dunning, J. B. Rosenzweig, K. M. Serratto
UCLA, Los Angeles, California
- P. Frigola
RadiaBeam, Los Angeles, California
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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.
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| THPMS020 |
Beam-Driven Dielectric Wakefield Accelerating Structure as a THz Radiation Source
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3041 |
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- A. M. Cook, H. Badakov, R. J. England, J. B. Rosenzweig, R. Tikhoplav, G. Travish, O. Williams
UCLA, Los Angeles, California
- A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio
- M. C. Thompson
LLNL, Livermore, California
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Funding: United States Department of Energy
Experimental work is planned to study the performance of a beam-driven cylindrical dielectric wakefield accelerating structure as a source of THz coherent Cerenkov radiation. For an appropriate choice of dielectric tube geometry and driving electron bunch parameters, the device operates in a single-mode regime, producing narrow-band radiation in the THz range. This source can potentially produce high power levels relative to currently available sources, with ~50 μJ radiated energy per pulse achievable using the electron beam currently in operation at the Neptune Advanced Accelerator Research Laboratory at UCLA (~13 MeV beam energy, ~200 μm RMS bunch length, ~500 pC bunch charge). Preparations underway for installation of the experiment are discussed.
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| THPMS021 |
Optimum Electron Bunch Creation in a Photoinjector Using Space Charge Expansion
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3044 |
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- 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
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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.
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| THPMS027 |
Dielectric Wakefield Accelerator Experiments at the SABER Facility
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3058 |
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- G. Travish, H. Badakov, A. M. Cook, J. B. Rosenzweig, R. Tikhoplav
UCLA, Los Angeles, California
- M. K. Berry, I. Blumenfeld, F.-J. Decker, M. J. Hogan, R. Ischebeck, R. H. Iverson, N. A. Kirby, R. Siemann, D. R. Walz
SLAC, Menlo Park, California
- A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio
- P. Muggli
USC, Los Angeles, California
- M. C. Thompson
LLNL, Livermore, California
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Funding: Work supported in part by Department of Energy contracts DE-AC02-76SF00515, DE-FG02-92-ER40745, DE-FG03-92ER40693 and W-7405-ENG-48
Electron bunches with the unparalleled combination of high charge, low emittances, and short time duration, as first produced at the SLAC FFTB, are foreseen to be produced soon at the SABER facility. These types of bunches have enabled wakefield driven accelerating schemes of >10 GV/m. In the context of the Dielectric Wakefield Accelerators (DWA) such beams, having rms bunch length as short as 20 um, have been used to drive 100 μm and 200 μm ID hollow tubes above 20 GV/m surface fields. These FFTB tests enabled the measurement of a breakdown threshold in excess of 4 GV/m (2 GV/m accelerating field) in fused silica. With the construction and commissioning of the SABER facility at SLAC, new experiments are made possible to test further aspects of DWAs including materials, tube geometrical variations, direct measurements of the Cerenkov fields, and proof of acceleration in tubes >10 cm in length. The E169 collaboration will investigate breakdown thresholds and accelerating fields in new materials including CVD diamond. Here we describe the experimental plans, beam parameters, simulations, and progress to date as well as future prospects for machines based of DWA structures.
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