Fast ion and neutron emission in CO2 laser irradiation of solid deuterium targets

Experimental results obtained from 10.6 μm irradiation of plane targets have shown a fast ion distribution whose peak occurs at an energy value of a few keW and whose maximum energy is higher than 60 keV. Of the 25 to 30% of the incident laser energy absorbed by the plasma only 6 to 8% was directed toward plasma heating. This fact indicates that 60% of the absorbed energy was carried out by ions with energies greater than 10 keV. For the yield of 104 neutrons with 2.45 MeV energy, the fastest of these ions are responsible. Interferometric measurements have shown a significant density profile modification. These results lead to the conclusion that resonant absorption becomes predominant over bremsstrahlung absorption for intensities greater than 1013 W/cm2. The associated ponderomotive force could be considered as a possible mechanism for fast ion generation