Electron density is a key parameter in designing and constructing a pumping system for high power transversely excited atmospheric (TEA) pressure CO2 laser. It is necessary to ensure uniform volumetric discharge in order to enhance the output power and the efficiency of gas laser. It is, however, very hard for TEA-CO2 laser to achieve electron density of more than 1014cm-3 necessary for volumetric discharge as the pressure of active gas of the laser is higher than atmospheric pressure.
Recent-developed external pre-ionization systems such as those based on high-energy field emission, ultraviolet or X-ray have enabled atmospheric pressure volumetric discharge in a short time of about 1㎲ and raised the output power of pulsed laser up to the level of GW. The main factor of getting higher power (over tens of GW) is to ensure that electron avalanche caused by inelastic collisions between CO2 (or N2 and He) molecule and cold electrons with energy of hundreds of keV is spatially uniform, and that non-self-sustained main discharge is conducted as a uniform volumetric one. It means that finding out the characteristics of change of electron density is of primary importance in developing high power TEA-CO2 laser.
The model of electron density for uniform volumetric discharge is a nonlinear model describing microphysical processes such as pre-ionization, avalanche ionization, recombination, attachment and so on. So far, there have been no general solutions of this model but only special solutions for some extreme cases.
Yun Tu Hon, a researcher at the Faculty of Physical Engineering, has proposed a method of general solutions for the nonlinear model and verified the accuracy and generality of his method by comparing the results with the data reported in the literature. He also reported some new special solutions unknown in the literature and the experimental results for them.
The proposed method will prove to be valuable for high power TEA-CO2 laser of hundreds of MW.
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