Source-to-sample characterization of laser-driven proton beams for radiobiological applications

Laser-driven plasma accelerators (LPA) are compact sources of ultra-short, intense proton pulses in the multi-10-MeV energy range. These unique parameters predestine LPAs as powerful tools for ultra-high dose rate radiobiology research. The sources’ capabilities were recently demonstrated in the first successful small animal pilot study on radiation-induced tumor growth delay in mice using an LPA proton source [1].
To promote further sophisticated radiobiological studies at LPAs, adapted approaches for primary LPA source characterization, beam monitoring and dosimeters are required. Here, most prominent challenges are LPA-inherent pulse-to-pulse fluctuation in terms of intensity as well as proton energy distribution, the ultra-high pulse dose rate and the harsh plasma environment, featuring a strong electromagnetic pulse (EMP) and an intense mixed radiation background. These conditions call for robust online monitoring solutions.
We present the solutions for source-to-sample characterization implemented at the ALBUS-2S beamline [2] at the Draco Petawatt laser system [3] at Helmholtz-Zentrum Dresden-Rossendorf. These include firstly an online beam monitoring system based on a time-of-flight spectrometer (ToF BMS). A core feature of the ToF BMS method is a precise spectrum-based forward-calculation of the corresponding volumetric dose distribution via Monte-Carlo simulation. Secondly, a dosimetric system for volumetric mm-scale sample irradiations was conceptualized and tested during an in vivo irradiation study, showing a solution for precise dosimetric characterization of ultra-high dose rate pulses at the ~500 mGy pulse dose range.
Lastly, with the OCTOPOD and MiniSCIDOM, two devices for online, single pulse characterization of volumetric dose distributions are presented, applicable for the primary LPA source and mm-scale dose distributions at the sample site, respectively. Both devices are based on volumetric scintillators as active detector material and rely on tomographic reconstruction for signal retrieval.

[1] F. Kroll, et al., Tumour irradiation in mice with a laser-accelerated proton beam, Nat Phys, 18, (2022), 316.
[2] F.-E. Brack, et al., Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline, Sci Rep, 10, (2020), 9118.
[3] U. Schramm, et al., First results with the novel petawatt laser acceleration facility in Dresden, J. Physics: Conf. Ser, 874, (2017), 012028.