First nuclear activation experiments at PHELIX laser facility

We activated compound activation targets in conjunction with a novel nuclear pyrometry method [1] for the investigation of the high-energy electron and bremsstrahlung component in relativistic laser-plasma interactions using the PHELIX laser facility at GSI. We used the short pulse of the PHELIX laser with intensities of more than 10 W/cm and laser energies arround 100 J with a pulse duration of 700 fs. The activation targets contain several isotopes with different photo-neutron disintegration thresholds. In the peak intensity regime of a focused short pulse laser relativistic electrons are generated during the lasersolid interaction. These electrons are accelerated into the target. The subsequent deceleration of high-energy electrons inside the target leads to high-energy bremsstrahlung which induces photo-nuclear reactions within the target. After the activation we could reconstruct the initial photon spectrum and the angular distribution of the high-energy bremsstrahlung via a gamma spectroscopy, an autoradiography of the targets (Fig. 1) and a suited analysis method. We observed several decay lines of activated isotopes, up to (γ,5n)-reactions (Fig. 2). The nuclear pyrometry allows