Enabling Femtosecond nC-class laser plasma accelerators using plasma mirror injectors: application to high-dose deposition at ultra-high dose rates – FemtoDose

In-vivo experiments demonstrated a strong difference of sensitivity of healthy vs unhealthy tissues to ionizing radiations when these are delivered within short and bright pulses. This so-called ultra-high dose rate radiotherapy (RT) or FLASH-RT has paved the way to a high-potential innovation in medical treatments.

To date, mechanisms behind the benefits of FLASH-RT have not been elucidated. Their understanding requires a deeper insight into the basis of radiation toxicity on biological samples at disparate timescales ranging from femtoseconds (fs) (molecule excitation) to the hour (cellular response) and beyond.

At present, only laser-based particle sources can open this route as they leverage on the ultrashort duration (<25fs) of high-power laser pulses. Such sources have the potential to deliver doses at unexplored dose rates (>10^7 Gy/s vs 30Gy/s in conventional FLASH-RT).

Yet, laser-based accelerators still suffer from major limitations that prevent their use as efficient sources for RT. In the case of laser-based electron accelerators, which are at the core of this project, the most important limitation comes from the difficulty to level up the electron charge per bunch from tens of pC up to a nC while
maintaining a high beam quality. This is paramount to deliver a therapeutic dose in a few seconds as required in FLASH-RT.

The main goal of this project is to increase by almost two orders of magnitude (up to nC-scale) the charge per electron bunch accelerated with lasers while preserving a high beam quality. This will be achieved thanks to a novel electron injection technique based on remarkable physical systems called ‘plasma mirrors’ that can act as high-charge injectors. The newly-developed source will be used to demonstrate dose deposition at ultra-high dose rates. In the future, such source should help understanding the fundamental mechanisms of ultra high-dose rate deposition in yet unexplored regimes.