Measurement of the atomic ion fraction of ion emitted from a miniature penning ion source

Penning-type ion source performance for neutron generator applications is characterized partly by the atomic ion fraction, providing one path by which source performance can be improved for increased neutron yields. A miniature penning ion source has been fabricated to investigate the atomic ion fraction of deuterium plasma by a mass-energy analyzer. The discharge current and atomic ion fraction increase with the increase of anode voltage and pressure. Effects of electrode materials on discharge characteristics have been studied. The atomic ion fraction could increase about 2% of the original atomic fraction by Au cathode instead of steel cathode, and it could increase about 1% of the original atomic fraction by Al cathode. The results can provide useful information for improving source performance by selecting more suitable anode voltage, pressure and electrode material.