Computational studies of electron transport and reaction rate models for argon plasma
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A validation study was performed on a capacitively coupled argon discharge to determine the most suitable models for chemistry and electron transport. Chemical reaction rate and electron transport models choices include equilibrium or non-equilibrium electron EDFs. Experimental studies performed by our collaborative partners in the Colorado School of Mines. Conditions for the studies are 138, 315, and 618 mTorr where the cycle averaged power varied at 20, 50, and 80 Watts in which the voltage supply was driven at 13.56 MHz. Simulations were performed using pressures and voltage used in experiments. The most accurate case was for 138 mTorr at 50 Watts using a non-Maxwellian EDF based chemistry (called Bolsig+ chemistry) and a constant electron momentum transfer cross section of 20 Angstroms which was computed from Boeuf’s paper; this model accurately modeled power deposition to within 2.6%. Furthermore, species number densities, electron temperature, and sheath thicknesses are obtained. Using Bolsig+ chemistry resulted in 20,000K higher electron temperatures than using Arrhenius chemistry rates. Results indicate that power deposition occurs due to electrons gaining energy from the sheath which in turn bombard neutral species producing metastable argon.