Boltzmann analysis of electron swarm parameters in CHF3+CF4 mixtures


Abstract: The electron drift velocity, mean energy, ionization, attachment, effective ionization coefficient, limit electrical field, and synergism of pure CHF3 (fluoroform), pure CF4 (tetrafluoromethane), and CHF3+CF4 gas mixtures are calculated by Boltzmann equation analysis in a wide range of density normalized electrical fields (E/N). The finite difference method is used to solve the two-term approximation of the Boltzmann equation under steady-state Townsend conditions. To our knowledge, no previous electron swarm parameters of these mixtures have been published. At constant E/N values, the electron mean energies and drift velocities increase with decreasing CHF3 content. The addition of CF4 into the mixture increases the attachment coefficient but reduces the ionization coefficient since CF4 is more electronegative than CHF3. Furthermore, the limit electrical fields increase with increasing CF4 concentration.

Keywords: Gas discharge characteristics, fluoroform, tetrafluoromethane, Boltzmann equations

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