Demonstration of ultra-high dose rate electron irradiation at FLASH𝑙𝑎𝑏@PITZ and new capabilities in the future

The Photo Injector Test facility at DESY in Zeuthen (PITZ) is building up an R&D platform, known as FLASH𝑙𝑎𝑏@PITZ, for systematically studying the FLASH effect in cancer treatment by employing its high-brightness electron beams, which can provide a uniquely large dose parameter range for radiation experiments. To demonstrate the capabilities, experiments with a reduced parameter range have been conducted on a startup beamline, which has delivered electron beams to the experimental site for irradiation at conventional and ultra-high dose rates (UHDR) of 0.05 Gy/s and several 1e5 Gy/s, respectively, and a varying dose up to 60 Gy, with the UHDR experiments finished within a single RF pulse (less than 1 millisecond). One major task is to predict and measure the delivered doses at the two distinct dose rates, with optimized electron beam generation and transport to establish reproducible irradiation. In this paper, the dose measurement with Gafchromic films and Monte Carlo simulations by FLUKA, both performed on the startup beamline, will be presented. The functionality of this setup has been further demonstrated in biochemical experiments; the results of irradiation of plasmid DNA will be discussed. The validated beam and dose parameters from the startup beamline justified the upgrade to a full FLASH𝑙𝑎𝑏@PITZ beamline, which will be capable of preserving the high beam quality from the PITZ photoinjector and therefore further expand the dose parameter space with more flexible dose delivery mechanisms. Beam dynamics simulations have been conducted to optimize the electron beam properties, while new technologies, e.g., for pencil beam scanning (PBS) with electrons, have been considered for the dose generation. Two typical experimental scenarios, with spatiotemporally constant and varying beams, respectively, have been verified with Monte Carlo simulations.