Energy gain calculations in Penning fusion systems using a bounce-averagedFokker-Planck model

In spherical Penning fusion devices, a spherical cloud of electrons, confin ed in a Penning-like trap, creates the ion-confining electrostatic well. Fu sion energy gains for these systems have been calculated in optimistic cond itions (i.e., spherically uniform electrostatic well, no collisional ion-el ectron interactions, single ion species) using a bounce-averaged Fokker-Pla nck (BAFP) model. Results show that steady-state distributions in which the Maxwellian ion population is dominant correspond to lowest ion recirculati on powers (and hence highest fusion energy gains). It is also shown that re alistic parabolic-like wells result in better energy gains than square well s, particularly at large well depths (> 100 kV). Operating regimes with fus ion power to ion input power ratios (Q-value) > 100 have been identified. T he effect of electron losses on the Q-value has been addressed heuristicall y using a semianalytic model, indicating that large Q-values are still poss ible provided that electron particle losses are kept small and well depths are large. (C) 2000 American Institute of Physics. [S1070- 664X(00)00711-4] .