Mechanism For H <sup> - </sup> Production In Cs-Seeded Ion Sources
摘要
Measurements of the rovibrational population of H2 products following dissociative charge transfer of D3+ in Cs vapor are reported in the context of the recent observation that the addition of Cs to an ion source discharge can lead to a significant increase in the H- ions extracted from the source. Consideration is also given to wall and plasma effects. It is concluded that dissociative charge transfer produces a hot H2(v) distribution, centered around v=6,with all levels populated into the vibrational continuum. It is also found that the discharge is an efficient producer of H atoms. Through wall collisions these H atoms can contribute both directly and indirectly to H- production in a Cs seeded discharge. Comparison with results from Xe seeded H2 discharges suggest that in Cs seeded discharges the effectiveness of the magnetic filter may be reduced, the electron density is significantly increased and the plasma potential will be increased. However, with Xe seeding, there is no conclusive evidence for electron cooling of the bulk electrons.