Irradiating a solid target with ultrashort, subpicosecond laser pulses, there is not enough time for the plasma to expand much during the pulse. Heating of the solid density matter occurs by the hot electrons generated in the corona.This is the so-called isochoric heating, by which solid density matter of several hundreds eV is generated. In the interior of stars matter is present in this extreme state, therefore investigating isochoric heating by ultrashort laser pulses is of interest for laboratory astrophysics. In the inertial confinement fusion pellet matter with such parameters is also present, its study is relevant for the fast ignitor inertial confinement fusion, in which case the fusion reaction is ignited by a fast electron or ion beam. KrF laser is one of the possible short pulse laser with which electron beam can be generated with high repetition rate.

       The fast electrons not only heat the solid target up. They penetrate deeply  in the cold matter where colliding with the still cold atom they excite the inner  K-shell. As the inner, K-shell radiation has a pulse duration of the heating  pulse, this method can be used for  the generation of ultrashort hard  x rays.

       At present a von  Hamos crystal x-ray spectrometer is being built, with which both K-shell radiation and isochoric heating will be studied.