Particle-in-cell modeling of negative-ion transport and extraction processes in a hydrogen negative-ion source

To understand the effect of the magnetic field on the H- extraction, the temporal behavior and spatial structure of the electrostatic potential near the plasma grid have been studied in detail by particle-in-cell simulation in the collisionless limit. Also, a parameter study of the dependence of the extracted H- current on the magnetic field has been done. The results show that the intrinsic physical mechanism to enhance H- extraction is possibly explained by the difference in dynamics between electrons and ions and by the resultant ambipolar electric field under the presence of the "weak" magnetic field. (c) 2006 American Institute of Physics.