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 quasi-monoenergetic beams. The modularity helical also provides attractive prospective multi-staging. Here we show, proof-of-principle basis, two-stage configuration which allows optical tuning selected proton beamlet. Experimental data, corroborated by particle tracing simulations, highlights importance controlling precisely beam injection. Efficient post-acceleration with an gain up ∼16 MeV (∼8 per stage, at average rate ∼1 GeV m −1 ) was achieved optimal time delay, synchronisation accelerating longitudinal electric fields be maintained through both stages.