Dual stage approach to laser-driven helical coil proton acceleration

Abstract

Helical coil accelerators are a recent development in laser-driven ion production, acting on the intrinsically wide divergence and broadband energy spectrum of laser-accelerated protons to deliver ultra-low divergence and quasi-monoenergetic beams. The modularity of helical coil accelerators also provides the attractive prospective of multi-staging. Here we show, on a proof-of-principle basis, a two-stage configuration which allows optical tuning of the energy of the selected proton beamlet. Experimental data, corroborated by particle tracing simulations, highlights the importance of controlling precisely the beam injection. Efficient post-acceleration of the protons with an energy gain up to ~16 MeV (~8 MeV per stage, at an average rate of ~1 GeV/m) was achieved at an optimal time delay, which allows synchronisation of the selected protons with the accelerating longitudinal electric fields to be maintained through both stages.

Proton imaging of high-energy-density laboratory plasmas

“…During an experiment, the protons are emitted by the source, propagate a distance r s to the interaction region where they acquire small deflections due to the electromagnetic fields, and then travel ballistically a distance r d to the detector. In a number of experiments (Paudel et al, 2012;Ahmed et al, 2016;Obst-Huebl et al, 2018;Ferguson et al, 2023), self-probing arrangements have also been demonstrated, where the TNSA protons accelerated from a foil are used to probe phenomena initiated by the same laser pulse that has accelerated them, for instance, in parts of the same target from which they are emitted, or in the surrounding medium. The top image is of 13 MeV protons, and the bottom image is of 14.7 MeV protons.…”

“…As an example, recent experiments by Zhang et al (2020) studied the electron-Weibel instability generated in a low-density gas-jet plasma using a circularly polarized laser via electron imaging with bunches of 45 MeV electrons from a linear accelerator. Efforts to image relativistic plasmas with wakefield-accelerated electron bunches were reported by Schumaker et al (2013), Zhang et al (2016), and Wan et al (2022, 2023. Schumaker et al (2013) were the first to demonstrate plasma probing applications employing wakefield-accelerated electrons, which enabled the detection of highly transient magnetic fields generated by an ultrashort, intense laser pulse on a solid target.…”

Synchronous post-acceleration of laser-driven protons in helical coil targets by controlling the current dispersion

“…Kar et al [21] conceived a two-beam laser-triggered HC current, allowing protons to travel through the HC twice, and the maximum energy in the simulation exceeded 100 MeV. This scheme was experimentally implemented by Ferguson et al [29] . Two laser beams with energies of approximately 50 J and approximately 60 J, respectively, interact with two coil targets sequentially.…”