Variational principle for optimal accelerated neutralized flow

Minimizing the energy deposited in the electron current in neutralized flows, such as in the Hall thruster, is examined. Modifying the electron current along the channel by inserting emitting electrodes, can enhance the efficiency. By employing variational methods, an optimal electron current distribution is found. The efficiency enhancement due to this effect, however, is shown to be small. (C) 2001 American Institute of Physics. [DOI: 10.1063/1.1331567].