The development of ultra-intense electron pulse for applications needs to be accompanied by the implementation of a practical dosimetry system. In this study four different systems were investigated as dosimeters for low doses with a very high-dose-rate source. First, the effects of ultra-short pulses were investigated for the yields of the Fricke dosimeter based on acidic solutions of ferrous sulfate; it was established that the yields were not significantly affected by the high dose rates, so the Fricke dosimeter system was used as a reference. Then, aqueous solutions of three compounds as fluorescence chemical dosimeters were utilized, each operated at a different solution pH: terephthalic acid - basic, trimesic acid - acidic, and coumarin-3-carboxylic acid (C3CA) - neutral. Fluorescence chemical dosimeters offer an attractive alternative to chemical dosimeters based on optical absorption for measuring biologically relevant low doses because of their higher sensitivity. The effects of very intense dose rate (TGy/ s) from pulses of fast electrons generated by a picosecond linear accelerator on the chemical yields of fluorescence chemical dosimeters were investigated at low peak doses (<20 Gy) and compared with yields determined under low-dose-rate irradiation from a 60 Co gamma-ray source (mGy/s). For the terephthalate and the trimesic acid dosimeters changes in the yields were not detected within the estimated (∼10%) precision of the experiments, but, due to the complexity of the mechanism of the hydroxyl radical initiated reactions in solutions of the relevant aromatic compounds, significant reductions of the chemical yield (-60%) were observed when the C3CA dosimeter was irradiated with the ultra-short pulses.

Department of Radiation and Chemical Physics Institute of Physics Czech Academy of Sciences Na Slovance 1999 2 18221 Prague Czech Republic

Department of Spectroscopy J Heyrovsky Institute of Physical Chemistry Czech Academy of Sciences Dolejškova 2155 3 182 23 Prague 8 Czech Republic

ELI Beamlines Institute of Physics Czech Academy of Sciences Za Radnicí 835 252 41 Dolní Břežany Czech Republic

Institut de Chimie Physique ELYSE CNRS UMR 8000 Université Paris Saclay 91400 Orsay France

Laser Plasma Department Institute of Plasma Physics Czech Academy of Sciences Za Slovankou 1782 3 18200 Prague Czech Republic

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