A new technique called Streaming Neutral Gas Injection (SNGI) is introduced as another alternative for negative hydrogen ion enhancement. By injecting highly directional neutral hydrogen gas near the extraction aperture, a region of localized high electron-neutral collision rate is created. This process lowers the effective electron temperature of the plasma at the extraction area to values favorable for H- ion production. The H- extraction characteristics in a multicusp plasma source attached with the SNGI device were investigated to confirm its effectiveness in negative ion enhancement. Negative ion density, electron temperature and electron density near the SNGI were measured to clarify their effect on the enhancement of negative ion production. (c) 2005 Elsevier B.V. All rights reserved.