Investigation of the Early Phases of Plasma Production by Laser Irradiation of Plane Solid Targets

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Abstract
The time development of line radiation emitted from a plasma produced by focusing a Q‐switched ruby laser onto a solid magnesium target has been investigated in the vacuum‐ultraviolet wavelength region using a 2‐m grazing incidence monochromator. The electron temperature was obtained using the foil‐absorption method. The time of appearance of MgIX and MgX lines at the target was measured as a function of the laser power. For the lowest laser power at which both ionic lines appeared, MgIX radiated before MgX. The appearance time of each line decreased as laser power was increased until at the higher powers they appeared at about the same time‐2 nsec after the beginning of the laser pulse. The ionization processes occurring in front of the target are discussed using a simple model for the plasma. From the time of appearance of the lines, conclusions on the electron temperature in the ``heating zone'' can be drawn as well as on an over‐all heating rate.