A negative hydrogen ion source has been built which will yield from 25 to 30 &mgr;a of H−ions focused on a ¼‐inch diameter spot. This is accomplished by first producing positive ions in a magnetic ion source. These ions are extracted and accelerated by at most 17.5 kv. The ions then pass through an electron pickup capillary tube into the center of which the electron donating gas is introduced. The H−ions emerging from this tube are accelerated by an additional 20 to 30 kv while the emerging secondary electrons are electrostatically repelled. The negative ions are then focused by an electrostatic ``saddle field'' lens and magnetically analyzed. An Evapor‐ion pump is used to maintain the pressure in the ion source container less than 10−4mm Hg.