Time-Resolved Electron Density Measurements of Laser Produced Plasmas using X-Band Microwave Interferometry

Laser produced plasma channels form a unique and significant laboratory tool for exploring the kinetics of plasma formation and decay. Using a sub-picosecond 100 GW ultraviolet laser system and a microwave interferometer operating at 9.2 GHz, time-resolved measurements are made of the electron density of the plasma. By vacuum sealing part of the interferometer, measurements are made at pressures between 10$^ {-2}$ and 10$^{3}$ Torr, and in a variety of gases, including neon, argon, xenon, nitrogen, and oxygen. Rate constants and multiphoton ionization and excitation cross sections can be extracted from the electron density decay rates, using a simple gas kinetic model in neon. The calculated constants are consistent with existing results.