First Name: J.
Middle Name: B.
Last Name: Rosenzweig
Full Name: J.B. Rosenzweig
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8 papers
| title: | Generation and Measurement of Relativistic Electron Bunches Characterizzed by a Linearly Ramped Current Profile |
| format: | journal article |
| year: | May 28, 2008 |
| 3 authors: | | | |
| abstract: | We report the first successful attempt to generate ultrashort (1–10 ps) relativistic electron bunches characterized by a ramped longitudinal current profile that rises linearly from head to tail and then falls sharply to zero. Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free-electron lasers as a means of reducing asymmetry in microbunching due to slippage. The scheme used to generate the ramped bunches employs an aniso-chronous dogleg beam line with nonlinear correction elements to compress a beam having an initial positive time-energy chirp. The beam current profile is measured using a deflecting mode cavity, and a pseudoreconstruction of the beam’s longitudinal phase space distribution is obtained by using this diagnostic with a residual horizontal dispersion after the dogleg. |
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| title: | Breakdown Limits on Gigavolt-per-Meter Electron-Beam-Driven Wakefields in Dielectric Structures |
| format: | journal article |
| year: | May 27, 2008 |
| 15 authors: | | | | | | | | | | | | | | | |
| abstract: | First measurements of the breakdown threshold in a dielectric subjected to GV=m wakefields produced by short (30 – 330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100 |
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| title: | Experimental Generation and Characterization of Uniformly Filled Ellipsoidal Electron-Beam Distributions |
| format: | journal article |
| year: | 2008 |
| 5 authors: | | | | | |
| abstract: | For 40 years, uniformly filled ellipsoidal beam distributions have been studied theoretically, as they hold the promise of generating self-fields linear in the coordinate offset in all three directions. Recently, a scheme for producing such distributions, based on the strong longitudinal expansion of an initially very short beam under its own space-charge forces, has been proposed. In this Letter we present the experimental demonstration of this scheme, obtained by illuminating the cathode in a rf photogun with an ultrashort laser pulse ( |
| keywords: | pbpl prl |
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| title: | Laser-Powered Dielectric Structure as a Micron-Scale Electron Source |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 3 authors: | | | |
| abstract: | We describe a resonant laser-powered structure, measur- ing 1 mm or less in every dimension, that is capable of generating and accelerating electron beams to low ener- gies ( ∼ 1–2 MeV). Like several other recently investigated dielectric-based accelerators, the device is planar and res- onantly excited with a side-coupled laser; however, exten- sive modifications are necessary for synchronous accelera- tion and focusing of nonrelativistic particles. Electrons are generated within the device via a novel ferroelectric-based cathode. The accelerator is constructed from dielectric ma- terial using conventional microfabrication techniques and powered by a 1-μm gigawatt laser. The electron beams pro- duced are suitable for a number of existing industrial and medical applications. |
| keywords: | pbpl |
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| title: | Observation of Multi-GeV Breakdown Thresholds in Dielectric Wakefield Structures |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | An experiment designed to test the breakdown threshold of a dielectric subjected to the GV/m-scale electric-fields of an intense electron-beam has been completed. In this experiment at the Final Focus Test Beam (FFTB) facility, the 28.5 GeV SLAC electron beam was focused down and propagated through short fused-silica capillary-tubes with internal diameters of as little as 100 μm. The electric field at the inner surface of the tubes was varied from about 1 GV/m to 22 GV/m by adjusting the longitudinal compres- sion of the electron bunch. We observed a sharp increase in optical emissions from the capillaries in the middle part of this surface field range which we believe indicates the transition between sustainable field levels and breakdown. If this initial interpretation is correct, the multi-GV/m sur- faced fields that were sustained equate to on axis accelerat- ing field of several GV/m. |
| keywords: | pbpl |
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| title: | Commissioning of the UCLA Neptune X-band Deflecting Cavity and Applications to Current Profile Measurement of Ramped Electron Bunches |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 5 authors: | | | | | |
| abstract: | A 9-cell standing-wave deflecting cavity has recently been constructed and installed at the UCLA Neptune Lab- oratory for use as a temporal diagnostic for the 13 MeV, 300 to 700 pC electron bunches generated by the Neptune photoinjector beamline. The cavity is a center-fed Glid- Cop structure operating in at TM110-like deflecting mode at 9.59616 GHz with a π phase advance per cell. At the maximum deflecting voltage of 530 kV, the theoretical res- olution limit of the device is 50 fs, although with current beam parameters and a RMS spot size of 460 μm the ef- fective resolution is approximately 400 fs. We discuss the operation and testing of the cavity as well as its intended application of measuring the temporal current profile of ramped electron bunches generated using the Neptune dog- leg compressor, and we present the first measurements of the electron beam current profile obtained using the deflect- ing cavity. |
| keywords: | pbpl |
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| title: | Beam-driven Dielectric Wakefield Accelerating Structure as a Thz Radiation Source |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 9 authors: | | | | | | | | | |
| abstract: | Experimental work is planned to study the performance of a beam-driven cylindrical dielectric wakefield accelerat- ing structure as a source of THz coherent Cerenkov radi- ation (CCR). For an appropriate choice of dielectric tube geometry and driving electron bunch parameters, the de- vice operates in a single-mode regime, producing 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 elec- tron beam currently in operation at the Neptune advanced accelerator 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. |
| keywords: | pbpl |
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| title: | The UCLA/FNPL Time Resolved Underdense Plasma Lens Experiment |
| format: | journal article |
| year: | 2005 |
| 11 authors: | | | | | | | | | | | |
| abstract: | A gaussian underdense plasma lens with peak density 5 × 1012cm-3and a full width half maximum (FWHM) length of 2.2 cm has been used to focus a relativistic electron beam. This plasma lens has a focusing strength equivalent to a quadrupole magnet with a 150 T/m field gradient. The lens focused a 15 MeV, 16 nC electron beam with initial dimensions σr= 500 μm and σz= 5 mm onto an optical transition radiation (OTR) screen 2 cm downstream of the lens. The average transverse area of the plasma focused electron beam was typically demagnified by a factor of 22. The light from the OTR screen was imaged into a streak camera in order to directly measure the correlation between z and σrwithin the beam. |
| keywords: | pbpl |
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