Thermonuclear Fusion Plasma by Lasers
As lasers have an ability to deliver a large amount of energy very rapidly to matters, one can produce thermonuclear temperature plasma. We observed the neutron yield from a solid deuterium target irradiated by the beam of glass laser, wave length of 1.06 μ, pulse width of 2 ns and power of about 10 GW.
The heating process by laser is one of the most interesting subject in plasma physics. The classical absorption becomes weak at high temperatures and the over-dense plasma is to perfectly reflect the laser beam. Considering the experimental results, anomalous absorption induced by the high electric field of laser beam seems to be introduced. The electron temperature was estimated from the soft x-ray measurement. The reflection intensity of laser beam from plasma and the time of flight of ions were investigated. These data have a close correlation with the event of the neutron yield. Until up to 200 eV of the electron temperature near the cut off density, the absorption is caused by the classical process and beyond this threshold the parametric instability, predicted by Nishikawa, begins to be functional. The electron temperature showed a steep rise with increase of the incident laser power after the threshold, 1013W/cm2. Near the threshold the oscillation of reflected beam was often observed. The fast component of ions began to appear.
In appendix, brief descriptions of damages in glass laser rods are presented as for the reference.
KeywordsElectron Temperature Neutron Yield Neutron Emission Parametric Instability Glass Laser
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