Marco Cavallone | Searcharxiv

arXiv2020

Dosimetric characterisation and application to radiation biology of a kHz laser-driven electron beam

Laser-plasma accelerators can produce ultra short electron bunches in the femtosecond to picosecond duration range, resulting in high peak dose rates in comparison with clinical accelerators. This peculiar characteristic motivates their application to radiation biology studies to elucidate the effect of the high peak dose rate on the biological response of living cells, which is still being debated. Electron beams driven by kHz laser systems may represent an attractive option for such applications, since the high repetition rate can boost the mean dose rate and improve the stability of the delivered dose in comparison with J-class laser accelerators running at 10 Hz. In this work, we present the dosimetric characterisation of a kHz, low energy laser-driven electron source and preliminary results on in-vitro irradiation of cancer cells. A shot-to-shot dosimetry protocol enabled to monitor the beam stability and the irradiation conditions for each cell sample. Results of survival assays on HCT116 colorectal cancer cells are in good agreement with previous findings reported in literature and validate the robustness of the dosimetry and irradiation protocol.

physics.acc-ph↗

arXiv2019

Shaping of a laser-accelerated proton beam for radiobiology applications via genetic algorithm

Laser-accelerated protons have a great potential for innovative experiments in radiation biology due to the sub-picosecond pulse duration and high dose rate achievable. However, the broad angular divergence makes them not optimal for applications with stringent requirements on dose homogeneity and total flux at the irradiated target. The strategy otherwise adopted to increase the homogeneity is to increase the distance between the source and the irradiation plane or to spread the beam with flat scattering systems or through the transport system itself. Such methods considerably reduce the proton flux and are not optimal for laser-accelerated protons. In this paper we demonstrate the use of a Genetic Algorithm (GA) to design an optimal non-flat scattering system to shape the beam and efficiently flatten the transversal dose distribution at the irradiated target. The system is placed in the magnetic transport system to take advantage of the presence of chromatic focusing elements to further mix the proton trajectories. The effect of a flat scattering system placed after the transport system is also presented for comparison. The general structure of the GA and its application to the shaping of a laser-accelerated proton beam are presented, as well as its application to the optimisation of dose distribution in a water target in air.

physics.med-ph↗