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Ferrario, M

Publications and source records attributed to Ferrario, M.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Plasma wakefields in the quasi-nonlinear regime: Experiments at ATF

In this work we present details of planned experiments to investigate certain aspects of the quasi non linear regime (QNL) of plasma wakefield acceleration (PWFA). In the QNL regime it is, in principal, possible to combine the benefits of both nonlinear and linear PWFA. That is, beams of high quality can be maintained through acceleration due to the complete ejection of plasma electrons from beam occupied region, while large energy gains can be achieved through use of transformer ratio increasing schemes, such as ramped bunch trains. With the addition of an short focal length PMQ triplet capable of focusing beams to the few micron scale and the ability to generate tunable bunch trains, the Accelerator Test Facility (ATF) at Brookhaven National Lab offers the unique capabilities to probe these characteristics of the QNL regime.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Time-domain measurement of a self-amplified spontaneous emission free-electron laser with an energy-chirped electron beam and undulator tapering

We report, with an unequivocal time-domain measurement, that an appropriately chosen undulator taper can compensate for an electron beam longitudinal energy-chirp in a free-electron laser amplifier, leading to the generation of single-spike radiation close to the Fourier limit. The measurements were taken using the frequency-resolved optical gating technique by employing an advanced transient-grating diagnostic geometry. The reconstructed longitudinal radiation characteristics are compared in detail to prediction from time-dependent three-dimensional simulations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Self-Amplified Spontaneous Emission Free-Electron Laser with an Energy-Chirped Electron Beam and Undulator Tapering

We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a self-amplified spontaneous emission mode free-electron laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. An increase of more than 1 order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Breaking the Attosecond, Angstrom and TV/m Field Barriers with Ultrafast Electron Beams

Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This scheme uses very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced {approx}2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Angst , or be used to permit 1.5 Angst operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications. We discuss the experimental issues associated with this initiative.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Plasma Wakefields in the Quasi-Nonlinear Regime

It has long been noted that the nonlinear 'blowout' regime of the PWFA has certain critical aspects for producing high quality beams that are owed to the elimination of electron density and current inside of the beam-occupied region: time-independent, linear ion-focusing, and acceleration independent of transverse position. Unfortunately, in applying this scheme to a linear collider, efficiency considerations strongly encourage use of pulse trains, in which one superimposes the wakes of driving and accelerating beams in turn. This implies that one needs to maintain stable wakes with the ability to maintain a resonant response which, given the presence of wave-breaking and amplitude dependent frequency, is not straightforward in the nonlinear regime. Here we propose a solution to this problem: operation in the quasi-nonlinear regime, where one uses beams with relatively low charge and transverse beam size much smaller than a plasma skin-depth. In this case, the beam density may exceed that of the plasma, producing blowout, but due to the small total charge, producing a disturbance that behaves in many ways as linear, having frequency essentially that of linear plasma oscillations. To illustrate the salient characteristics of this regime we present the results of single and multi-pulse simulations, and give a theoretical analysis for the preservation of the plasma frequency. We discuss a proposal for testing this regime at the BNL ATF.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Microbunching and RF Compression

Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Dynamics of Longitudinal Phase-Space Modulations in an rf Compressor for Electron Beams

Free Electron Lasers (FELs) operating in the UV or x-ray radiation spectrum require peak beam currents that are generally higher than those obtainable by present electron sources, thus making bunch compression necessary. Compression, however, may heighten the effects of collective forces and degrade the beam quality. In this paper they provide a framework for investigating some of these effects in rf compressors by focusing on the longitudinal dynamics of small-amplitude density perturbations, which have the potential to cause the disruptive appearance of the so-called microbunching instability. They develop a linear theory valid for low-to-moderate compression factors under the assumption of a 1D impedance model of longitudinal space charge and provide validation against macroparticle simulations.

43 PARTICLE ACCELERATORS↗