Development of a Polyatomic Molecular Ion Source with a Hollow Cathode

A duoplasmatron type ion source with a hollow cathode has been designed and the beam extraction performance under various discharge conditions tested. An ion beam extracted from a hydrogen plasma showed a clear peak of C
₂
H
₂
⁺
in the mass spectrum with the source operation H
₂
gas pressure of 5.2×10
^-3
Pa in the downstream of the extraction aperture, 20 mA discharge current, 616 V discharge voltage and 1 kV extraction voltage. Hydrogen plasma confinement in the beam extraction region of the ion source seems necessary to enhance molecular ion beam extraction from the source.