Abstract
New experiments show that above threshold energy per unit area of 6mJmm−2, the mass ablated and accelerated in the plasma sheet comes predominantly from the erosion of the copper electrodes rather than Teflon ablation. Experiments were conducted using copper electrodes separated at a distance of 1cm, 3cm and 5cm in a parallel plate Pulsed Plasma Thruster (PPT) configuration,charged with a 4μF capacitor between 900V - 3100V and obtained peak currents of ≈ 4kA - 8kA. Experimental results show repeatability and form a data set in which a newly developed PPT model is validated against. The model is based on a one dimensional circuit that is solved simultaneously with the dynamics of the accelerated plasma sheet. Similar models to date have treated mass ablation and the resistance of the plasma sheet as separate effects; they have also assumed that only a single plasma sheet has been created. Using a PPT without Teflon (or any other standard propellant) has allowed a direct link to be established between electrode ablation and plasma parameters. The overall discharge is the summation of multiple plasma sheets that are produced each time the voltage across the capacitor reverses. Individual plasma sheets are modeled by the ablation of material from the electrodes by cathode spot processes into a mixing region. The high discharge currents flowing through the mixing region are then affected by z-pinch constriction which will alter bulk plasma properties. Modeled results are within the expected error of the experimental data. Calculated ablated material from copper electrodes, for a 6.8J discharge, was 19μg per pulse, other PPT performance parameters fall within typical values.