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.