Spectroscopic Measurements of Plasma Ion Density by Neutral Beam Probing

A method of determining plasma ion density by spectroscopic measurement of line emission from a probing neutral beam, attenuated by resonance charge transfer interaction with plasma ions, is proposed and tested. A hydrogen plasma produced by an R.F. discharge was used as the subject of the test. The parameters of the hydrogen probing beam in the region of observation were ∼400 eV average energy, ∼3×10 12 cm -3 peak density and ∼2 µs pulse width. The beam was produced by a z -pinch-gun, a neutral beam source. From the attenuation rate of H β emission and the known cross-section of the interaction, the ion density was determined when it was in the range from 2×10 14 cm -3 to 5×10 14 cm -3 . The value determined agreed well with the electron density measured with an He–Ne laser interferometer.