Observation of Indirect, Time-Dependent Heating of Solid Targets from Ultraintense, Ultrashort Pulse Laser Light

Summary form only given. We have observed indirect, picosecond heating of solid targets from high intensity (>10¹⁷ W/cm ²), ultrashort pulse (500 fs) laser pulses. The study was performed on foil targets consisting of 1000 Aring Al and 12.5 mum Ti. The targets were illuminated from the aluminum side to eliminate direct laser heating of the Ti foil. Time-resolved measurements of the Ti K_alpha (2.749 Aring) were made using a sub-picosecond X-ray streak camera interfaced to a von Hamos crystal spectrograph. In addition to the time-resolved Ti K_alpha data, a spherical crystal, X-ray imaging spectrometer was fielded to determine the emission region of the Ti K_alpha and an electron spectrometer was used to observe the non-thermal electron distribution. Finally, the spectrally resolved backscattered laser light was observed to help determine if laser-driven instabilities produce the hot electrons. The data will be presented along with a preliminary interpretation of the results