| Paper |
Title |
Page |
| 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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| TUPMS037 |
Simulation of an Iris-guided Inverse Free-electron Laser Micro-bunching Experiment
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1266 |
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- J. T. Frederico, S. Reiche, R. Tikhoplav
UCLA, Los Angeles, California
- G. Gatti
INFN/LNF, Frascati (Roma)
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The Free-Electron Laser code Genesis 1.3 has been modified to include waveguides within the undulator, reducing the diffraction effects for long wavelength FELs. Several types of waveguides are considered, which are rectangular and circular waveguides as well as iris-loaded open waveguides. Studies are presented here on the enhancement of FEL and IFEL with these wave-guiding structures in comparison to free-space propagation of the radiation wave.
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| WEOAKI02 |
Observations of Underdense Plasma Lens Focusing of Relativistic Electron Beams
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1907 |
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- M. C. Thompson, M. C. Thompson
LLNL, Livermore, California
- H. Badakov, J. B. Rosenzweig, R. Tikhoplav, G. Travish
UCLA, Los Angeles, California
- R. P. Fliller, G. M. Kazakevich, J. K. Santucci
Fermilab, Batavia, Illinois
- J. L. Li
Rochester University, Rochester, New York
- P. Piot
Northern Illinois University, DeKalb, Illinois
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Funding: This work was performed under the auspices of the US Department of Energy under Contract No. DE-FG03-92ER40693 and W-7405-ENG-48.
Focusing of a 15 MeV, 19 nC electron bunch by an underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in experiments at the Fermilab NICADD Photoinjector Laboratory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam-envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Correlations between the beam charge and the properties of the beam focus corroborate this conclusion. Time resolved measurements of the focused electron bunch are also reported and all results are compared to simulations.
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Slides
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| THPMS020 |
Beam-Driven Dielectric Wakefield Accelerating Structure as a THz Radiation Source
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3041 |
| |
- 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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| THPMS026 |
The UCLA Helical Permanent-Magnet Inverse Free Electron Laser
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3055 |
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- R. Tikhoplav, J. T. Frederico, G. Reed, J. B. Rosenzweig, S. Tochitsky, G. Travish
UCLA, Los Angeles, California
- G. Gatti
INFN/LNF, Frascati (Roma)
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The Inverse Free Electron Laser (IFEL) is capable, in principle, of reaching accelerating gradients of up to 1 GV/m making it a prospective accelerator scheme for linear colliders. The Neptune IFEL at UCLA utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC and a CO2 laser with peak energy of up to 100 J, and will be able to accelerate electrons to 100 MeV over an 80 cm long, novel helical permanent-magnet undulator. Past IFELs have been limited in their average accelerating gradient due to the Gouy phase shift caused by tight focusing of the drive laser. Here, laser guiding is implemented via an innovative Open Iris-Loaded Waveguide Structure scheme which ensures that the laser mode size and wave front are conserved through the undulator. The results of the first phase of the experiment are discussed in this paper, including the design and construction of a short micro-bunching undulator, testing of the OILS waveguide, as well as the results of corresponding simulations.
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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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