Shielding assessment for the HED Science Instrument at the European XFEL

Interaction with plasma of high-power, high-intensity lasers of multi-TW and PW class always produces ‘hot’ electrons with a quasi-Maxwellian energy spectrum, with temperatures between about 10 keV and several MeV for intensities ranging from 1016 W/cm2 up to about 1022 W/cm2. Those electrons interact in turn with the target and the surrounding materials, producing Bremsstrahlung and possibly photo-neutrons. The resulting radiation field is present in all laser-plasma experiments, and drives the shielding design of every facility dedicated to high energy density research.
The proper definition of the radiation source term is a challenging aspect, and the shielding cannot therefore be designed with the conventional tools used in nuclear and accelerator physics. Different, complementary approaches are possible: relying only on analytical formulas, combining those predictions with experimental results to characterize source terms in input to established Monte Carlo codes, and/or interfacing those codes with specialized Particle-In-Cell programs. At the Helmholtz-Beamline of the European XFEL, the shielding design of the High Energy Density (HED) Physics Instrument has been evaluated by using analytical calculations, cross-checked with measurements done at the DRACO laser of the Helmholtz-Zentrum Dresden-Rossendorf. In this work the characterization of the radiation fields and the resulting shielding solutions are summarized.