Analysis of chamber simulations of long probes in high-speed, dense plasmas

We describe chamber tests of simulated electrodynamic tethers (EDTs) of different geometries operating in a dense, high-speed plasma. The geometries tested and described here were cylindrical and flat-ribbon. Several important conclusions that can be drawn from the tests are as follows: the currents collected by cylinder are close to what would be predicted via orbital-motion-limited (OML) current collection theory. The tape tether had comparable current levels to a theoretical equal area OML cylinder collector. However, I-V behavior clearly is different at nearest distances (~ 16 Ad tape width) as compared to furthest test distances (~ 6 \_D tape width). The tape tether did better than a theoretical equal mass solid cylinder. A knee in the I-V curves can be seen in the tape data at a potential that is near the estimated Below this knee the current increases rapidly as voltage is increased. Above the knee the current increases at a rate near that expected from OML current-collection models depending on the relative width. This likely is an example of high-speed plasma flow effect. Perpendicular tape orientation performed slightly better than parallel.