CO2 laser irradiation of solid targets in strong magnetic fields

Abstract

Gain-switched CO2 laser pulses of 225 J were focused onto planar carbon targets in the presence of longitudinal magnetic fields up to 105 kG. For fields above 25 kG, the mass loss and cross-sectional area of the cylindrical blow-off plasma varied as B−6/5. For these cases, only the 60-nsec gain-switched laser spike caused target damage; the 1.5-μsec tail was absorbed by a ∼100-eV partially confined plasma extending several cm from the target. The field dependence of the plasma cross section is consistent with an adiabatic expansion against the magnetic field.