Description
Laser-wakefield accelerators (LWFAs) can deliver Gy-scale doses in a single ~150fs pulse, reaching dose rates exceeding 10¹³Gys⁻¹ [1]. This represents a fundamentally distinct regime, where dose is deposited before radical diffusion and early physico-chemical processes evolve, and where the volumetric density of ionising tracks exceeds that of any previously explored irradiation modality [1]. We report in vitro single-pulse irradiation experiments at the Gemini laser (Central Laser Facility, UK) using LWFA-driven very high energy electron (VHEE) beams across multiple cancer and normal cell lines, including three-dimensional tumour spheroids [1].
In vitro single cell results reveal distinctive features in the biological response to femtosecond-scale irradiation not observed at picosecond timescales [2] or in the FLASH regime. These include a significant increase in relative biological effectiveness, an increased α parameter in linear-quadratic modelling indicative of complex clustered DNA damage, and a reduction in tumour cell radioresistance [1]. 53BP1 foci measurements under oxic and hypoxic conditions imply these effects are not primarily driven by oxygen depletion [1]. A recent Gemini campaign extended this work to comparisons between monolayer and three-dimensional spheroid geometries, and between single-pulse and multi-pulse dose delivery.
[1] McAnespie et al., Phys. Med. Biol. 70, 155001 (2025).
[2] McAnespie et al., Int. J. Radiat. Oncol. Biol. Phys. 118, 1105 (2024).