Ionization of a background gas by cross-propagating YAG and CO/sub 2/ laser pulses

Summary form only given, as follows. We report the results of measurements on a plasma created by transversely propagating YAG and CO/sub 2/ laser beams that are focused to the same spot in a background gas. The goal is to design a plasma shutter for controlling the length of a CO/sub 2/ laser pulse, which will be used later in plasma wave excitation experiments. We describe the gas breakdown dynamics of each laser alone, and then together. The gases used are helium and argon. The CO/sub 2/ laser pulse is nominally 100 ns long and can be varied up to 5 Joules. The green YAG laser pulse is nominally 7 ns long and can be varied up to 500 mJ.