Fermilab, Batavia, USA
* A. Zholents, PAC'11.
Fermilab, Batavia, USA
ANL, Argonne, USA
Northern Illinois University, DeKalb, Illinois, USA
We demonstrate the generation of a train of electron bunches with variable spacing at the Argonne Wakefield Accelerator. The photocathode ultraviolet laser pulse consists of a train of four pulses produced via polarization splitting using two alpha-BBO crystals. The photoemitted electron bunches are then manipulated in a horizontally-bending dogleg with variable longitudinal dispersion. A downstream vertically-deflecting cavity is then used to diagnose the temporal profile of the electron beam. The generation of a train composed of four bunches with tunable spacing is demonstrated. Such train of bunch could have application to, e.g., the resonant excitation of wakefield in dielectric-lined waveguides.
Fermilab, Batavia, USA
ANL, Argonne, USA
Northern Illinois University, DeKalb, Illinois, USA
A 1/2-1-1/2 cell normal-conducting 1.3-GHz deflecting cavity was recently installed at the Argonne Wakefield Accelerator. The cavity will soon be included in a transverse-to-longitudinal phase space exchanger that will eventually be used to shaped the current profile of AWA electron bunches in support of dielectric wakefield experimentS with enhanced transformer ratio. In this paper we report on the initial commissioning of the deflecting cavity including rf-conditioning and beam-based measurement of the deflecting strength.
Fermilab, Batavia, USA
Northern Illinois University, DeKalb, Illinois, USA
The Advanced Superconducting Test Acccelerator (ASTA) is being constructed at Fermilab. The existing New Muon Lab (NML) building is being converted for this facility. The accelerator will consist of an electron gun, injector, beam acceleration section consisting of 3 TTF-type or ILC-type cryomodules, multiple downstream beamlines for testing diagnostics and conducting various beam tests, and a high power beam dump. When completed, it is envisioned that this facility will initially be capable of generating a 750 MeV electron beam with ILC beam intensity. An expansion of this facility was recently completed that will provide the capability to upgrade the accelerator to a total beam energy of 1.5 GeV. Two new buildings were also constructed adjacent to the ASTA facility to house a new cryogenic plant and multiple superconducting RF (SRF) cryomodule test stands. In addition to testing accelerator components, this facility will be used to test RF power systems, instrumentation, and control systems for future SRF accelerators such as the ILC and Project-X. This paper describes the current status and overall plans for this facility.
Northern Illinois University, DeKalb, Illinois, USA
MPQ, Garching, Munich, Germany
DESY, Hamburg, Germany
Tech-X, Boulder, Colorado, USA
Dielectric wakefield accelerators offer many advantages over conventional RF accelerators such as higher acceleration gradients and cost effectiveness. In this paper we describe our experimental plans to demonstrate enhanced transformer ratios with drive and witness bunches. The experiment, will be performed at the Free-electron LASer in Hamburg (FLASH) and utilizes unique pulse shaping capabilities using the dual-frequency superconducting linac to produce high transformer ratios (>2). The beam-driven acceleration mechanism will be based on a cylindrical-symmetric dielectric-lined waveguide (DLW). The experimental setup is described, and start-to-end numerical simulations of the experiment will be presented.
Fermilab, Batavia, USA
ANL, Argonne, USA
Northern Illinois University, DeKalb, Illinois, USA
We demonstrate the generation of a train of electron bunches with variable spacing at the Argonne Wakefield Accelerator. The photocathode ultraviolet laser pulse consists of a train of four pulses produced via polarization splitting using two alpha-BBO crystals. The photoemitted electron bunches are then manipulated in a horizontally-bending dogleg with variable longitudinal dispersion. A downstream vertically-deflecting cavity is then used to diagnose the temporal profile of the electron beam. The generation of a train composed of four bunches with tunable spacing is demonstrated. Such train of bunch could have application to, e.g., the resonant excitation of wakefield in dielectric-lined waveguides.
Northern Illinois University, DeKalb, Illinois, USA
Fermilab, Batavia, USA
In this paper we demonstrate the generation of a tunable, longitudinal double-pulse electron beam. Experimental results on the generation of electron bunch trains with sub-picosecond structure have been previously reported where an initial transverse electron beam modulation was produced by masking the electron beam directly*. Here the initial transverse structure is imparted by masking of the photoinjector drive laser to effectively produce two horizontally offset beams at photoemission in the RF gun. A longitudinal double-pulse modulation is then realized after a transverse-to-longitudinal phase-space exchange beamline. Longitudinal profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of coherent transition radiation.
* Y.-E. Sun et al., Tunable Subpicosecond Electron-Bunch-Train Generation Using a Transverse-To-Longitudinal Phase-Space Exchange Technique, Phys. Rev. Lett. 105, 234801 (2010).
Northern Illinois University, DeKalb, Illinois, USA
LANL, Los Alamos, New Mexico, USA
Fermilab, Batavia, USA
The Advanced Superconducting Test Accelerator (ASTA) at Fermilab incorporates a magnetic bunch compressor chicane to compress the 40-MeV electron bunches generated in the photoinjector. In this paper, we present a numerical analysis and parametric study of the bunch compressor's performance for various operating scenarios. The beam dynamics simulations, carried out with Astra, Impact-Z and CSRTrack, are compared against each other. Finally, an operating regime with low phase space dilutions is suggested based on the simulation results.
Northern Illinois University, DeKalb, Illinois, USA
Fermilab, Batavia, USA
The Advanced Superconducting Test Accelerator (ASTA) at Fermilab uses a high-brightness photoinjector capable of producing electron bunches with charges up to 3.2 nC, to be used in support of a variety of advanced accelerator R&D experiments. The photoinjector incorporates an extensive diagnostics suites including a single-shot longitudinal-phase-space diagnostics composed of a horizontally deflecting cavity followed by a vertical spectrometer. In this paper, we present the design, optimization, and performance analysis (including detrimental collective effects) of the longitudinal phase space diagnostics and especially compare two possible choices of deflecting cavity frequencies.
Northern Illinois University, DeKalb, Illinois, USA
In recent years, wakefield acceleration has gained attention due to its high acceleration gradients and cost effectiveness. In beam-driven wakefield acceleration, a critical parameter to optimize is the transformer ratio. It has been shown that current shaping of electron beams allows for enhanced (>2) transformer ratios. In this paper we present the optimization of the pulse shape of the drive bunch for dielectric-wakefield acceleration. We also explore practical techniques capable of tailoring current profiles into these optimal shapes.