Laser radiography

Summary form only given, as follows. When a high power laser is focused onto a solid or gaseous target at very high intensities the electron motion in the electric field of the laser becomes relativistic and MeV electrons and ions are observed both from interactions with gaseous and solid targets. The relativistic threshold is usually given as I/spl gamma//sup 2/=1.3/spl times/10/sup 18/ W cm/sup -2/ 5 m/sup 2/, where the average kinetic energy of the electron oscillating in the laser field becomes equivalent to the particle's rest mass. The most powerful lasers have been able to focus the laser light to intensities in excess of 10/sup 20/ W cm/sup -2/ with pulses containing up to several hundred Joules of laser radiation on target. Experiments investigating short pulse length (/spl sim/1 ps), high intensity (/spl sim/10/sup 20/ W/cm/sup 2/) laser beams on the Vulcan Laser at the Rutherford Appleton Laboratory have yielded significant X-ray doses which are in the energy regime of interest to the flash radiography community at AWE. The results from a series of experiments conducted at RAL are presented. These were designed to characterise the magnitude and spectral content of the radiation flux output from the Vulcan laser using thermoluminescent dosimetry. Dosimetry results are also compared with MCNP calculations. The radiation output derived from the laser/target interaction would then be used to radiograph spherical, very high density models. These radiographic images are then compared with existing flash radiographic images obtained at AWE with traditional pulsed power e-beam accelerators.