ZDependence of the Laser-Intensity Threshold for Inhibited Electron Thermal Conduction

Temporally resolved sub-kiloelectronvolt x-ray emission pulses have been obtained from disk targets illuminated with 1.06-μm wavelength laser light at 5×${10}^{14}$ W/${\mathrm{cm}}^2$. Striking variations in the x-ray pulse shape from Be, Ti, Sn, Au, and U targets indicate the onset of strongly inhibited electron thermal conduction during the rise of the laser intensity. The laser intensity threshold for this strong inhibition is found to increase with target atomic number $Z$.