Negative hydrogen ion beam extracted from a Bernas‐type ion source

Negative hydrogen $(H−)$ ion beam was produced without cesium seeding by a Bernas‐type ion source with a coaxial hot cathode. The amount of $H−$ ion beam current extracted from an original Bernas‐type ion source using a hairpin shape filament as a hot cathode was 1 μA with the 0.4 A arc current, while that 300 eV beam energy. In the other hand, $H−$ ion beam current using the Bernas‐type ion source with a coaxial hot cathode reached 4 μA under the same condition. Production efficiency was enhanced by the focused plasma produced by a coaxial hot cathode.