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.