Stability of the modulator in a plasma-modulated plasma accelerator
Physical Review E American Physical Society 108:1 (2023) 15204
Abstract:
We explore the regime of operation of the modulator stage of a recently proposed laser-plasma accelerator scheme [Phys. Rev. Lett. 127, 184801 (2021)], dubbed the plasma-modulated plasma accelerator (P-MoPA). The P-MoPA scheme offers a potential route to high-repetition-rate, GeV-scale plasma accelerators driven by picosecond-duration laser pulses from, for example, kilohertz thin-disk lasers. The first stage of the P-MoPA scheme is a plasma modulator in which a long, high-energy “drive” pulse is spectrally modulated by copropagating in a plasma channel with the low-amplitude plasma wave driven by a short, low-energy “seed” pulse. The spectrally modulated drive pulse is converted to a train of short pulses, by introducing dispersion, which can resonantly drive a large wakefield in a subsequent accelerator stage with the same on-axis plasma density as the modulator. In this paper we derive the 3D analytic theory for the evolution of the drive pulse in the plasma modulator and show that the spectral modulation is independent of transverse coordinate, which is ideal for compression into a pulse train. We then identify a transverse mode instability (TMI), similar to the TMI observed in optical fiber lasers, which sets limits on the energy of the drive pulse for a given set of laser-plasma parameters. We compare this analytic theory with particle-in-cell (PIC) simulations and find that even higher energy drive pulses can be modulated than those demonstrated in the original proposal.Modulational instability in large-amplitude linear laser wakefields
Physical Review E American Physical Society 107 (2023) L023201
Abstract:
We investigate the growth of ion density perturbations in large-amplitude linear laser wakefields via two-dimensional particle-in-cell simulations. Growth rates and wave numbers are found to be consistent with a longitudinal strong-field modulational instability (SFMI). We examine the transverse dependence of the instability for a Gaussian wakefield envelope and show that growth rates and wavenumbers can be maximised off-axis. On-axis growth rates are found to decrease with increasing ion mass or electron temperature. These results are in close agreement with the dispersion relation of a Langmuir wave with energy density that is large compared to the plasma thermal energy density. The implications for wakefield accelerators, in particular multi-pulse schemes, are discussed.Demonstration of kilohertz operation of hydrodynamic optical-field-ionized plasma channels
Physical Review Accelerators and Beams American Physical Society 25 (2022) 011301
Abstract:
We demonstrate experimentally that hydrodynamic optical-field-ionized (HOFI) plasma channels can be generated at kHz-scale pulse repetition rates, in a static gas cell and for an extended period. Using a pump-probe arrangement, we show via transverse interferometry that the properties of two HOFI channels generated 1 ms apart are essentially the same. We demonstrate that HOFI channels can be generated at a mean repetition rate of 0.4 kHz for a period of 6.5 h without degradation of the channel properties, and we determine the fluctuations in the key optical parameters of the channels in this period. Our results suggest that HOFI and conditioned HOFI channels are well suited for future high-repetition rate, multi-GeV plasma accelerator stages.GeV-scale accelerators driven by plasma-modulated pulses from kilohertz lasers
Physical Review Letters American Physical Society 127 (2021) 184801
Abstract:
We describe a new approach for driving GeV-scale plasma accelerators with long laser pulses. We show that the temporal phase of a long, high-energy driving laser pulse can be modulated periodically by copropagating it with a low-amplitude plasma wave driven by a short, low-energy seed pulse. Compression of the modulated driver by a dispersive optic generates a train of short pulses suitable for resonantly driving a plasma accelerator. Modulation of the driver occurs via well-controlled linear processes, as confirmed by good agreement between particle-in-cell (PIC) simulations and an analytic model. PIC simulations demonstrate that a 1.7 J, 1 ps driver, and a 140 mJ, 40 fs seed pulse can accelerate electrons to energies of 0.65 GeV in a plasma channel with an axial density of 2.5 × 1017cm−3. This work opens a route to high repetition-rate, GeV-scale plasma accelerators driven by thin-disk lasers, which can provide joule-scale, picosecond-duration laser pulses at multikilohertz repetition rates and high wall-plug efficiencies.EuPRAXIA Conceptual Design Report (vol 229, pg 3675, 2020)
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS Springer Science and Business Media LLC 229:1 (2021) 4285-4287