Plasma-Neutral Heat Transfer in Coaxial RF Argon Discharges

Particle-in-cell/Monte Carlo Collision (PIC/MCC) algorithms comprise a numerical model to assess the discharge characteristics of an RF plasma microthruster concept that exploits an RF capacitively coupled discharge (RFCCD) to heat a propellant. The effects of heat transfer between the discharge and the neutral species on microthruster performance are discussed. Heat transfer within the plasma discharge has been shown to greatly affect the discharge characteristics and thruster performance. Increasing the neutral temperature reduces the amount of power transmitted into the fluid through a reduction of the neutral density, and thus reduces effectiveness of the discharge. The PIC/MCC modeling showed that the power transmitted into the fluid increases faster than linear with respect to an increase in applied potential, but the total power absorbed increases on the order of a linear trend. The power transmission efficiency is found to be directly proportional to the applied potential, making the discharge more efficient at higher voltages. The theoretical specific impulse also increases as the applied potential or discharge pressure is increased