TIME-RESOLVED TEMPERATURE MEASUREMENT OF A LASER-HEATED SURFACE

It has been shown by spectroscopic measurements that a laser beam focused on a metal surface in a vacuum gives a radiant temperature of 8500±1500°K. More precisely, with a time-resolved spectrometric technique the temperature rises to its peak value in 30 ns after the laser peak, and then falls with a thermal time constant of approximately 100 ns. The thermionic emission of electrons and ions was also recorded and found to consist substantially of two pulses separated in time by a few tenths of a microsecond. A simple qualitative theory is suggested which accounts for most of the experimental results. This involves charge separation from the plasma of vaporized metal, which was found by Langmuir probe measurements to have an electron temperature of approximately 105°K.