Electron trapping and reinjection in prepulse-shaped gas targets for laser-plasma accelerators
Physical Review Accelerators and Beams American Physical Society 23:11 (2020) 111301
Abstract:
A novel mechanism for injection, emittance selection, and postacceleration for laser wakefield electron acceleration is identified and described. It is shown that a laser prepulse can create an ionized plasma filament through multiphoton ionization and this heats the electrons and ions, driving an ellipsoidal blast-wave aligned with the laser-axis. The subsequent high-intensity laser-pulse generates a plasma wakefield which, on entering the leading edge of the blast-wave structure, encounters a sharp reduction in electron density, causing density down-ramp electron injection. The injected electrons are accelerated to ∼2 MeV within the blast-wave. After the main laser-pulse has propagated past the blast-wave, it drives a secondary wakefield within the homogenous background plasma. On exiting the blast-wave structure, the preaccelerated electrons encounter these secondary wakefields, are retrapped, and accelerated to higher energies. Due to the longitudinal extent of the blast-wave, only those electrons with small transverse velocity are retrapped, leading to the potential for the generation of electron bunches with reduced transverse size and emittance.Guiding of high-intensity laser pulses in 100mm-long hydrodynamic optical-field-ionized plasma channels
Physical Review Accelerators and Beams American Physical Society 23:8 (2020) 081303
Abstract:
Hydrodynamic optically-field-ionized (HOFI) plasma channels up to 100mm long are investigated. Optical guiding is demonstrated of laser pulses with a peak input intensity of $6\times10^{17}$ W cm$^{-2}$ through 100mm long plasma channels with on-axis densities measured interferometrically to be as low as $n_{e0} =(1.0\pm0.3)\times10^{17}$cm$^{-3}$. Guiding is also observed at lower axial densities, which are inferred from magneto-hydrodynamic simulations to be approximately $7\times10^{16}$cm$^{-3}$. Measurements of the power attenuation lengths of the channels are shown to be in good agreement with those calculated from the measured transverse electron density profiles. To our knowledge, the plasma channels investigated in this work are the longest, and have the lowest on-axis density, of any free-standing waveguide demonstrated to guide laser pulses with intensities above $>10^{17}$ W cm$^{-2}$.Numerical modelling of chromatic effects on axicon-focused beams used to generate HOFI plasma channels
Journal of Physics: Conference Series IOP Publishing 1596 (2020)
Abstract:
Hydrodynamic optical-field-ionised (HOFI) plasma channels promise a route towards high repetition-rate, metre-scale stages for future laser plasma accelerators. These channels are formed by hydrodynamic expansion of a plasma column produced by optical field ionisation at the focus of a laser, typically from an axicon lens. Since the laser pulses used to generate the initial plasma column are of sub-picosecond duration, chromatic effects in the axicon lens could be important. In this paper we assess these effects using a numerical propagation code. The code is validated using analytical formulae and experimental data. For the parameter range investigated, dispersive effects are found to be of minor importance, reducing the peak on-axis intensity in the focal region by approximately 10%.Excitation and control of plasma wakefields by multiple laser pulses
Physical Review Accelerators and Beams American Physical Society 119 (2017) 044802
Electron bunch profile reconstruction based on phase-constrained iterative algorithm
Physical Review Accelerators and Beams American Physical Society 19:3 (2016)