Comments on the Validity of Ballistic Pendulum Measurements with Pulsed Plasma Accelerators

The pendulum configuration was suggested as a possible fault in a previous condemnation of the ballistic pendulum as a useful momentum measurement tool with pulsed plasma accelerators. A ballistic pendulum was presented in which the entire discharge system of a rail-type plasma accelerator, including the electrodes, is surrounded completely by the pendulum bob. Finally, with this arrangement, any momentum components due to surface sputtering of the pendulum are cancelled through multiple collisions with the walls, with the possible exception of a negligible error introduced by impingement of sputtered mass onto the electrodes.