Absorption Spectroscopy Of A Radiatively Heated Aluminium Layer

Abstract

We present here a direct diagnostic of the shallow temperature gradient created in the very dense region of a laser irradiated target by X-UV radiation. A multilayered target composed of a plastic substrate covered with a thin samarium layer is irradiated with a 0.26 μm wavelength laser pulse at irradiances of 3. 10¹⁴ W/cm². A thin aluminium layer is inserted in the plastic as an absorbing tracer at different distances from the samarium. Kα absorption lines appear in the samarium quasi-continuum emission around 1.5 keV. The analysis of these lines gives the temperature of the aluminium layer. A shallow temperature gradient between 40 and 100 eV is measured and compared with radiative hydrocode simulations which predict that the X-UV emission of samarium around 400 eV create a radiative heat wave responsible of the observed temperature gradient.