Variational principle for optimal accelerated neutralized flow

Minimizing the energy deposited in the electron current in neutralized flow s, such as in the Hall thruster, is examined. Modifying the electron curren t along the channel by inserting emitting electrodes, can enhance the effic iency. By employing variational methods, an optimal electron current distri bution 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].