Focused beam dosimetry of short VHEE bunches (Invited Paper)

Accelerators driven by 10s TW-class lasers can produce electron bunches with femtosecond-scale duration and energy of 100s of MeV. A potential application of such short bunches is high-dose rate radiotherapy, which could transition to FLASH radiotherapy if a sufficiently large dose is delivered in a single shot. Here we present Monte Carlo simulations to study the bunch length evolution of an electron beam propagating in a water phantom. We show that for electron energies above 100 MeV the bunch lengthens to 1–10 ps duration after interaction with a 30 cm long water phantom, both for a collimated and weakly focused geometry. The corresponding dose rates are on the order of 200 Gy/s per primary electron, much higher than in conventional radiotherapy.