Spectroscopic Measurements on an H- Ion Source Discharge

Spectral emission lines from an H- Penning surface-plasma source (SPS), the 4X source, are examined in the visible and near ultraviolet. Electron distribution temperatures are deduced from integral line-strength measurements. These temperatures are surprisingly low, about 0.5 eV. Electron density values of about 1.5 × 1014 cm-3 and H-atom energies between 2 and 2.6 eV are determined from the measured Balmer-line profiles. Assuming the H- energy is identical to the H-atom energy, an emittance limit of 0.006¿·cm·mrad is deduced for this source with a 5.4-mm aperture.