A scintillating fiber imaging spectrometer for active characterisation of laser-driven proton beams

Next generation high-power laser facilities are expected to generate hundreds-of-MeV proton beams and operate at multi-Hz repetition-rates, presenting opportunities for medical, industrial and scientific applications requiring bright pulses of energetic ions. Characterising the spectro-spatial profile of these ions at high repetition-rates in the harsh radiation environments created by laser-plasma interactions remains challenging but is paramount for further source development. To address this, we present a compact scintillating fiber imaging spectrometer based on the tomographic reconstruction of proton energy deposition in a layered fiber array. Modelling indicates that spatial resolution of ∼1 mm and energy resolution of<10% at protons energies>20 MeV are readily achievable with existing 100 μmdiameter fibers. Measurements with a prototype beam profile monitor using 500 μmfibers demonstrate active readout with invulnerability to electromagnetic pulses, and <100 Gy sensitivity. The performance of the full instrument concept is explored with Monte-Carlo simulations, accurately reconstructing a proton beam with a multiple-component spectro-spatial profile.