Demonstration of ultra-high dose rate electron irradiation at FLASHlab@PITZ

<i>Objective.</i>The photo injector test facility at DESY in Zeuthen (PITZ) is building up an R&D platform, known as FLASH<b><i>lab</i></b>@PITZ, for systematically studying the FLASH effect in cancer treatment with its high-brightness electron beams, which can provide a uniquely large dose parameter range for radiation experiments. In this paper, we demonstrate the capabilities by experiments with a reduced parameter range on a startup beamline and study the potential performance of the full beamline by simulations.<i>Approach.</i>To measure the dose, Gafchromic films are installed both in front of and after the samples; Monte Carlo simulations are conducted to predict the dose distribution during beam preparation and help understand the dose distribution inside the sample. Plasmid DNA is irradiated under various doses at conventional and ultra-high dose rate (UHDR) to study the DNA damage by radiations. Start-to-end simulations are performed to verify the performance of the full beamline.<i>Main results.</i>On the startup beamline, reproducible irradiation has been established with optimized electron beams and the delivered dose distributions have been measured with Gafchromic films and compared to FLUKA simulations. The functionality of this setup has been further demonstrated in biochemical experiments at conventional dose rate of 0.05 Gy s^-1and UHDR of several 10⁵ Gy s^-1and a varying dose up to 60 Gy, with the UHDR experiments finished within a single RF pulse (less than 1 millisecond); the observed conformation yields of the irradiated plasmid DNA revealed its dose-dependent radiation damage. The upgrade to the full FLASH<b><i>lab</i></b>@PITZ beamline is justified by simulations with homogeneous radiation fields generated by both pencil beam scanning and scattering beams.<i>Significance.</i>With the demonstration of UHDR irradiation and the simulated performance of the new beamline, FLASH<b><i>lab</i></b>@PITZ will serve as a powerful platform for studying the FLASH effects in cancer treatment.