Longitudinal phase space dynamics of witness bunch during the Trojan Horse injection for plasma-based particle accelerators

Abstract

In the Trojan Horse injection process for plasma-based particle accelerators, we have investigated how the longitudinal phase space of the witness bunch would be governed by the parameters of the ionization laser and background plasma in the limit of quasistatic wakefield approximation. The tunneling ionization rate distribution by the laser pulse is introduced to describe the ionization time interval and initial distribution of the witness electrons. The quasilinear (or equivalently quasistatic) regime of the charged particle beam-driven wakefield is considered to make the phase of the wake potential constant in time in the driver beam frame. In the simulations, it is shown that the ionization laser phase on the quasistatic wake potential determines the longitudinal space-charge field of the witness bunch. We also find that the relative energy spread of the witness bunch can be estimated by the sum of three effects: The ionization time interval, wakefield slope, and space-charge fields of the witness bunch. Analytical expressions for the characteristic distance from the ionization to trapping positions, rms length, and relative energy spread of the witness bunch are obtained approximately and compared with the particle-in-cell simulations.Published under license by AIP Publishing. https://doi. Phys. Plasmas 13, 056709 (2006). FIG. 6. The average energy and energy spread of the witness bunch for k p n i ¼ -3.3. (blue dashed line) The asymptotic behavior of the relative energy spread. (blue solid curve) The analytical expression (10) for the relative energy spread. (blue circles) The PIC simulation result of the relative energy spread. (red circles) The PIC simulation result of the average energy. Physics of Plasmas ARTICLEscitation.org/journal/php

Ultrahigh brightness beams from plasma photoguns

“…When the accelerating and focusing electric field profile is thereby constant, and the plasma blowout is larger and/or the electron driver beam is shorter as in E-210 so that there is no driver beam kick that could increase the transverse momentum of released HIT electrons, realization of witness bunches with normalized emittances down to nm rad scale, and hence ultrahigh brightness can be achieved in E-310. This is consistent with earlier works and estimations of emittance and brightness in plasma photocathode scenarios [15,17,19,[33][34][35][36][37][38][39][40][41]. The central importance of emittance and beam quality of electron beams for various applications is highlighted e.g.…”

Plasma accelerator-based ultrabright x-ray beams from ultrabright electron beams

“…The remaining residual energy spread ∆W rms,min ∆W res,max obtained in this simulation can be further reduced by decreasing the ionisation volume with smaller laser spot sizes and operation at lower plasma wave medium densities n 0 , because in the first order approximation the absolute energy spread scales as ∆W res,max ∝ w 2 0 √ n 0 ; 10 this scaling has been confirmed in Ref. 17. Although computationally more costly to simulate, experimentally such operation at lower plasma densities is in many ways easier as it naturally improves the spatiotemporal precision of injection.…”

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“…This is consistent with earlier works and estimations of emittance and brightness in plasma photocathode scenarios. [22,23,27,29,30,[32][33][34][35]38,40,67] Figure 12 visualizes and contrasts the E-210 scenario (top panel) with a potential E-310 scenario (bottom panel). The electron driver beam (green) propagates from top left to bottom right and excites the plasma wave.…”