26 research outputs found
Observation of Skewed Electromagnetic Wakefields in an Asymmetric Structure Driven by Flat Electron Bunches
Relativistic charged-particle beams which generate intense longitudinal
fields in accelerating structures also inherently couple to transverse modes.
The effects of this coupling may lead to beam break-up instability, and thus
must be countered to preserve beam quality in applications such as linear
colliders. Beams with highly asymmetric transverse sizes (flat-beams) have been
shown to suppress the initial instability in slab-symmetric structures.
However, as the coupling to transverse modes remains, this solution serves only
to delay instability. In order to understand the hazards of transverse coupling
in such a case, we describe here an experiment characterizing the transverse
effects on a flat-beam, traversing near a planar dielectric lined structure.
The measurements reveal the emergence of a previously unobserved
skew-quadrupole-like interaction when the beam is canted transversely, which is
not present when the flat-beam travels parallel to the dielectric surface. We
deploy a multipole field fitting algorithm to reconstruct the projected
transverse wakefields from the data. We generate the effective kick vector map
using a simple two-particle theoretical model, with particle-in-cell
simulations used to provide further insight for realistic particle
distributions.Comment: Six pages, seven figures. Submitted to Physical Revie
Adiabatic plasma lens experiments at SPARC
Abstract Passive plasma lenses in the underdense regime have been shown to give extremely strong linear focusing, with strength proportional to the local plasma ion density. This technique has been proposed as the basis of a scheme for future linear colliders that mitigates the Oide effect through adiabatic focusing. In this scenario the plasma density in the lens is ramped slowly on the scale of betatron motion, to funnel the beam to its final focus while forgiving chromatic aberrations. We present to the physics design of an adiabatic plasma lens experiment to be performed at SPARC Lab. We illustrate the self-consistent plasma response and associated beam optics for symmetric beams in plasma, simulated by QuickPIC using exponentially rising density profiles. We discuss experimental plans including plasma source development and betatron-radiation-based beam diagnostics
Plasma-photonic spatiotemporal synchronization of relativistic electron and laser beams
Modern particle accelerators and their applications increasingly rely on precisely coordinated interactions of intense charged particle and laser beams. Femtosecond-scale synchronization alongside micrometre-scale spatial precision are essential e.g. for pump-probe experiments, seeding and diagnostics of advanced light sources and for plasma-based accelerators. State-of-the-art temporal or spatial diagnostics typically operate with low-intensity beams to avoid material damage at high intensity. As such, we present a plasma-based approach, which allows measurement of both temporal and spatial overlap of high-intensity beams directly at their interaction point. It exploits amplification of plasma afterglow arising from the passage of an electron beam through a laser-generated plasma filament. The corresponding photon yield carries the spatiotemporal signature of the femtosecond-scale dynamics, yet can be observed as a visible light signal on microsecond-millimetre scales
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Breaking the Attosecond, Angstrom and TV/M Field Barriers with Ultra-Fast 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 use of very low Q beams may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the LCLS 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 in cryogenic undulator technology, to create compact accelerator-undulator systems that can lase below 0.15 {angstrom}, or be used to permit 1.5 {angstrom} 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
Electron bunch generation from a plasma photocathode
Plasma waves generated in the wake of intense, relativistic laser or particle
beams can accelerate electron bunches to giga-electronvolt (GeV) energies in
centimetre-scale distances. This allows the realization of compact accelerators
having emerging applications, ranging from modern light sources such as the
free-electron laser (FEL) to energy frontier lepton colliders. In a plasma
wakefield accelerator, such multi-gigavolt-per-metre (GV m) wakefields
can accelerate witness electron bunches that are either externally injected or
captured from the background plasma. Here we demonstrate optically triggered
injection and acceleration of electron bunches, generated in a multi-component
hydrogen and helium plasma employing a spatially aligned and synchronized laser
pulse. This ''plasma photocathode'' decouples injection from wake excitation by
liberating tunnel-ionized helium electrons directly inside the plasma cavity,
where these cold electrons are then rapidly boosted to relativistic velocities.
The injection regime can be accessed via optical density down-ramp injection,
is highly tunable and paves the way to generation of electron beams with
unprecedented low transverse emittance, high current and 6D-brightness. This
experimental path opens numerous prospects for transformative plasma wakefield
accelerator applications based on ultra-high brightness beams
Drive Beam Sources and Longitudinal Shaping Techniques for Beam Driven Accelerators
Linear colliders are an attractive platform to explore high-precision physics of newly discovered particles. The recent significant progress in advanced accelerator technologies has motivated their applications to colliders which has been discussed in the alegro workshop. In this paper we discuss structure wakefield acceleration, namely collinear wakefield acceleration and two-beam acceleration. We especially discuss available drive and witness beam sources based on L and S-band radiofrequency technology, and also summarize available and forthcoming longitudinal shaping techniques to improve the overall acceleration efficiency via the transformer ratio
Drive Beam Sources and Longitudinal Shaping Techniques
Linear colliders are an attractive platform to explore high-precision physics of newly discovered particles. The recent significant progress in advanced accelerator technologies has motivated their applications to colliders which has been discussed in the {\sc alegro} workshop. In this paper we discuss one promising scheme, collinear wakefield acceleration. We especially discuss available drive and witness beam sources based on L and S-band radiofrequency technology, and also summarize available and forthcoming longitudinal shaping techniques to improve the overall acceleration efficiency via the transformer ratio