Abstract
Present-day and next-generation accelerators, particularly for applications in driving wakefield-based schemes, require longitudinal beam shaping and attendant longitudinal characterization for experimental optimization. Here we present a diagnostic method which reconstructs the longitudinal beam profile at the location of a wakefield-generating source. The methods presented derive the longitudinal profile of a charged particle beam solely from measurement of the time-resolved centroid energy change due to wakefield effects. The reconstruction technique is based on a deconvolution algorithm that is fully generalizable to any analytically or numerically calculable Green's function for the wakefield excitation mechanism. This method is shown to yield precise features in the longitudinal current distribution reconstruction. We demonstrate the accuracy and efficacy of this technique using simulations and experimental examples, in both plasmas and dielectric structures, and compare to the experimentally measured longitudinal beam parameters as available. The limits of resolution and applicability to relevant scenarios are also examined.
Highlights
Advanced acceleration techniques based on beam-driven wakefields have produced unprecedented results in terms of achievable gradients, exceeding the GeV/m threshold in dielectrics [1], and extending up to 10’s of GeV/m in plasmas [2]
To go beyond proof-of-concept, wakefield research looks to optimize such acceleration schemes. In this regard, maximizing the efficiency of energy transfer to the wakefield acceleration process requires breaking the symmetry in the wake-driving beam distribution by precision manipulation of its longitudinal profile [3]
The prompt and precise characterization of the longitudinal profile is critical for performance enhancement in wakefield accelerators
Summary
Advanced acceleration techniques based on beam-driven wakefields have produced unprecedented results in terms of achievable gradients, exceeding the GeV/m threshold in dielectrics [1], and extending up to 10’s of GeV/m in plasmas [2]. The time-resolved mean energy is acquired with a commonly employed single-shot longitudinal phase space (LPS) diagnostic, consisting of a deflecting cavity and dipole magnet spectrometer [10] This measurement of the energy centroid is differential (made via a comparison between the time dependent mean energy when the wakefield source is present or not), so in the absence of significant longitudinal motion within the distribution it accounts for downstream optics and external sources of energy change. The information gleaned from the manipulating media can doubly yield additional detailed bunch profile
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