TIME-RESOLVED STUDY OF NONLOCAL ELECTRON HEAT-TRANSPORT IN HIGH-TEMPERATURE PLASMAS

Exploiting the high absorption efficiency of intense, ultrashort laser pulses in gases of atomic clusters we have created plasma filaments w ith temperatures of >1 keV and electron densities in excess of 10(20) cm(-3). Using picosecond laser pulses, we have interferometrically mea sured the temporal and spatial evolution of the electron density in th ese plasmas on a fast (<50 ps) time scale. Our measurements indicate t hat nonlocal heat transport by hot electrons drives a fast ionization wave, and the data agree well with a nonlocal heat transport model. [S 0031-9007(97)05139-9].