| title: | Dielectric Wakefield Accelerator Experiments at the Saber Facility |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | Electron bunches with the unparalleled combination of high charge, low emittances, and short time duration, as first produced at the SLAC Final Focus Test Beam (FFTB), are foreseen to be produced at the SABER facility. These types of bunches have enabled wakefield driven accelerating schemes of multi-GV/m in plasmas. 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 um and 200 um ID hollow tubes above 20 GV/m surface fields. These FFTB tests enabled the measurement of a breakdown threshold in fused silica (with full data analysis still ongoing) [1]. With the construction and commissioning of the SABER facility at SLAC, new experiments would be 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. This 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. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Observations of Underdense Plasma Lens Focusing of Relativistic Electron Beams |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 10 authors: | | | | | | | | | | |
| abstract: | Focusing of a 15 MeV, 19 nC electron bunch by an un- derdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in ex- periments at the Fermilab NICADD Photoinjector Labora- tory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and re- duced 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 un- derdense 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. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| 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_pub |
| Download | View | Details | edit | delete | |
| 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_pub |
| Download | View | Details | edit | delete | |
| 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_pub |
| Download | View | Details | edit | delete | |
| title: | The UCLA Helical Permanent-Magnet Inverse Free Electron Laser |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 7 authors: | | | | | | | |
| abstract: | 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 (OILS) 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. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | High Average Current Betatrons for Industrial and Security Applications |
| format: | conference procceeding |
| conference: | PAC07 |
| year: | 2007 |
| 8 authors: | | | | | | | | |
| abstract: | The fixed-field alternating-gradient (FFAG) betatron has emerged as a viable alternative to RF linacs as a source of high-energy radiation for industrial and security applications. For industrial applications, high average currents at modest relativistic electron beam energies, typically in the 5 to 10 MeV range, are desired for medical product sterilization, food irradiation and materials processing. For security applications, high power x-rays in the 3 to 20 MeV range are needed for rapid screening of cargo containers and vehicles. In a FFAG betatron, high-power output is possible due to high duty factor and fast acceleration cycle: electrons are injected and accelerated in a quasi-CW mode while being confined and focused in the fixed-field alternating- gradient lattice. The beam is accelerated via magnetic induction from a betatron core made with modern low- loss magnetic materials. Here we present the design and status of a prototype FFAG betatron, called the Radiatron, as well as future prospects for these machines. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| 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_pub |
| Download | View | Details | edit | delete | |
| title: | how to use the Docserver |
| format: | journal article |
| year: | |
| 0 authors: | unknown |
| abstract: | this is a test doc. |
| keywords: | pbpl_pub |
| Details | edit | delete | |
| title: | Single spike operation in SPARC SASE-FEL |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | The single spike operation regime has been analyzed in the case of the SPARC injector and freeelectron-laser. Four different beams at 50 pC are studied, with different production condition and performance. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Status of the Fermi@Elettra Photoinjector |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 21 authors: | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The new FERMI@Elettra photoinjector is presently undergoing high-power testing and characterization at MAXlab in Lund, Sweden. This effort is a collaboration between Sincrotrone Trieste, MAX-lab and UCLA. The 1.6-cell RF gun cavity and the focusing solenoid were successfully designed and built by the Particle Beam Physics Laboratory at UCLA, delivered to Sincrotrone Trieste at the beginning of 2008, and installed in the linac tunnel at MAX-lab. Use of the MAX-lab facility will allow the FERMI project to progress significantly with the photoinjector while waiting for the completion of the new linac building extension at Sincrotrone Trieste. We report here on the high-power conditioning of the RF cavity and the first beam tests. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Experimental Generation and Characterization of Uniformly Filled Ellipsoidal Beam Distribution |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 6 authors: | | | | | | |
| abstract: | Recently, a scheme for producing ideal uniformly filled ellipsoidal beam distributions, which depends on the strong longitudinal expansion of an initially very short beam under its own space charge forces, has been demonstrated at the UCLA Pegasus Laboratory. Here we present further work on the characterization of this novel regime of operation of a photoinjector. In particular we study the sensitivity of the generation of the uniformly filled ellipsoidal distribution from the initial transverse laser profile. The ultra-high brightness of the beam created operating in this ‘blow-out’ regime is verified obtaining high quality relativistic electron diffraction patterns from thin Al foils. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | A Novel Fabrication Technique for the Production of RF Photoinjectors |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 9 authors: | | | | | | | | | |
| abstract: | Recent developments in Solid Freeform Fabrication (SFF) technology may make it possible to design and produce near netshape copper structures for the next generation of very high duty factor, high gradient radio frequency (RF) photoinjectors. RF and thermal management optimized geometries could be fully realized without the usual constraints and compromises of conventional machining techniques. A photoinjector design incorporating SFF and results from an initial material feasibility study will be reported. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Design and Fabrication of an X-Band traveling wave deflection mode cavity for longitudinal characterization of ultra-short electron beam pulses |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 9 authors: | | | | | | | | | |
| abstract: | An X-band Traveling wave Deflector mode cavity (XTD) has been developed at Radiabeam Technologies to perform longitudinal characterization of the subpicosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam parameters at the Accelerator Test Facility (ATF) at Brookhaven National Laboratory, and is scalable to higher energies. An XTD is designed to operate at 11.424 GHz, and features short filling time, femtosecond resolution, and a small footprint. RF design, fabrication procedure, and commissioning plans are presented. An experimental program at ATF to utilize the deflector for compressed beam characterization is discussed, including proposed measurements of the phase space filamentation due to non-linear processes in a chicane compressor. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Recent results and future perspectives of the SPARC project |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 77 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in various configurations, a Thomson backscattering source and a plasma accelerator experiment (these last two ones jointly with the project PLASMONX). The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. As a first stage of the commissioning, a complete characterization of the photoinjector has been accomplished with a detailed study of the emittance compensation process downstream the gun-solenoid system: this lead to the first direct experimental demonstration of emittance oscillations in a drift. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching and the demonstration of the “velocity bunching” technique in the linac. SASE and SEEDING experiments are foreseen by the end of the current year. In this paper we report the experimental results obtained so far and the scientific program for the near future. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | Simulation of and progress towards a micron-scale laser-powered dielectric electron source |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 5 authors: | | | | | |
| abstract: | A dielectric, slab-symmetric structure for generating and accelerating low-energy electrons has been under study for the past two years. The resonant device is driven by a side-coupled laser and is configured to maintain field profiles necessary for synchronous acceleration and focusing of nonrelativistic particles. Intended applications of the structure include the production of radiation for medical treatments, imaging, and industrial uses. Results from 3D simulation of the structure geometry and its resonant properties are presented here. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | SPUR: A new code for the calculation of synchrotron radiation from very long undulator systems |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 3 authors: | | | |
| abstract: | The accurate calculation of synchrotron radiation from an undulator is a common problem and numerous codes have been developed that describe the radiation from analytic and measured undulator fields. However, for very long undulator systems there is not a suitable code that can handle the amount of data in a convenient manner and which runs in a practically realisable time limit. The development of a new code, SPontaneous Undulator Radiation (SPUR) [1], is presented which computes the spontaneous radiation from electron beams passing through a system of undulators. The code supports parallel architecture, and uses the HDF5 [2] technology to efficiently handle the multi-dimensional data. The latest developments and benchmarking are presented. |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |
| title: | A real-time bunch length terahertz interferometer |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 5 authors: | | | | | |
| abstract: | The recent development of advanced photoinjectors and next generation light sources guides the progression towards high-current, ultra-short beams. The measurement of these short pulses, with sub-picosecond resolution, is essential for successful beam operation and optimization. This paper describes the development of a real-time, shotto-shot bunch length diagnostic utilizing a novel coherent terahertz radiation autocorrelation technique. The proposed diagnostic is called the real-time interferometer (RTI). |
| keywords: | pbpl_pub |
| Download | View | Details | edit | delete | |