Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

We report experimental results of a single coaxial plasma accelerator in preparation for a colliding plasma experiment. The utilized device consisted of a coaxial pair of electrodes, accelerating the plasma due to J x B forces. A pulse forming network, composed of three capacitors connected in parallel, with a total capacitance of 27 mu F was set up. A thyratron allowed to switch the maximum applied voltage of 9 kV. Under these conditions, the pulsed currents reached peak values of about 103 kA. The measurements were performed in a small vacuum chamber with a neutral-gas prefill at gas pressures between 10 Pa and 14 000 Pa. A gas mixture of ArH2 with 2.8% H-2 served as the discharge medium. H-2 was chosen in order to observe the broadening of the H-beta emission line and thus estimate the electron density. The electron density for a single plasma accelerator reached peak values on the order of 10(16) cm(-3). Electrical parameters, inter alia inductance and resistance, were determined for the LCR circuit during the plasma acceleration as well as in a short circuit case. Depending on the applied voltage, the inductance and resistance reached values ranging from 194 nH to 216 nH and 13 m Omega to 23 m Omega, respectively. Furthermore, the plasma velocity was measured using a fast CCD camera. Plasma velocities of 2 km/s up to 17 km/s were observed, the magnitude being highly correlated with gas pressure and applied voltage. (C) 2015 AIP Publishing LLC.