Theoretical study on the electron energy distribution function and electron transport parameters of argon plasma

摘要

Fluid model of argon plasma require the input of transport parameters that depend on the electron energy distribution function (EEDF). The EEDF and electron transport parameters of reduced field and electric field frequency in argon plasma are investigated by solving the Boltzmann equation with the two-term approximation. It is found that the EEDF closes to Druyvesteyn distribution and decreases sharply after several eV when the reduced field is less than 10Td. The low energy part of EEDF flats with the reduced field, and the high energy tail of EEDF increases with the reduced field. The EEDF approaches to dual temperature Maxwellian distribution when the reduced field is larger than 50Td. When the reduced field is larger than 300Td, the high energy tail of EEDF decreases more slowly than Maxwellian distribution, and the shape of EEDF tends to concave. The electron mobility decreases with the reduced field, and tends to a const. The electron diffusion coefficient increases with the reduced field, but exists a local minimum at 50Td. The relationship between EEDF and electric field frequency shows that the EEDF approaches to Maxwellian distribution in a high frequency field because of the collision with electrons and neutral particles. In this case, the electron mobility and diffusion coefficient are complex number, and the imaginary parts raise with the field frequency. The absolute value of transport parameters decrease with the field frequency.