Collimation of Laser-Driven Proton Beams for in vivo radiobiological investigation of FLASH Radiotherapy

Laser-driven ion acceleration (LDA) promises a more compact and cost-effective alternative to conventional proton therapy. Ultra-high dose rates have been shown to differentially spare healthy tissue relative to tumor tissue (FLASH effect). LDA beams can achieve these dose rates with the use of a beam transport system to compensate for the substantial divergence and energy spread of the beams following the laser-target interaction. Presented here is the implementation of a compact, permanent magnet-based beam transport to deliver 10 MeV protons to in vivo biological samples to investigate the FLASH effect. Dosimetry was performed by a suite of diagnostics including multiple online integrating current transformers to indirectly estimate the dose, a scintillating screen for dose profile monitoring, and radiochromic films for the on-target dose profile. This work further establishes the practicality of employing compact LDA proton sources for FLASH studies and showcases the capability of the BELLA Center iP2 beamline to accommodate additional radiobiological experiments.