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.