Energetic electrons and x-ray photons from multiterawatt Ti: Sapphire lasers

The energy distribution and yield of electrons and hard x-ray photons were investigated by irradiating tungsten and tantalum targets with ∼30 fs pulses in the intensity range 10¹⁸-10¹⁹ W cm^-2 by using the Laboratoire d'Optique Appliquée (LOA) as well as the Max Born Institut (MBI) multiterawatt Ti : sapphire lasers. For the measurement of the hard x-ray emission in the energy range from 15 keV to 700 keV at the LOA a 9-channel spectrometer of calibrated thermoluminescence detectors (TLD) was used. The scaling of the hard x-rays was studied by varying the incident laser energy within one order of magnitude and the pulsewidth by a factor of 5. The hot electron output was investigated in the range 300 keV-1 MeV with the new MBI Ti : sapphire laser by using a time-of-flight spectrometer. The results indicate a sensitive interplay between the temporal laser shape and laser intensity.