Abstract

Trace levels of lithium are detected on 100-µs time scales using an electrooptically tuned cw dye laser, in conjunction with a high resolution 0.03-Å spectrometer/optical multichannel analyzer. The spectra of Li⁷ resonance lines at 6708 Å are analyzed for their Zeeman splitting patterns, after unfolding the effects of intracavity absorption (ICA) on the line shape. For these time scales, a sensitivity to ~1 × 10⁷ lithium atoms/cc at a level of ΔI/I~ 10% has been observed, corresponding to enhancement factors over single-pass absorption of ~1000×. Intracavity enhancement of the line structure in the wings of the line, .and a weak blue shift asymmetry have also been observed, but always in the presence of a central absorption feature. The 0.1-Å instantaneous laser linewidth is usually scanned over a 1-Å range, at frequencies up to 30 kHz. Ultimately this detection system will enclose a hot, dense fusion plasma, intersecting an 80-keV, 10-mA neutral lithium beam to probe the plasma internal magnetic field structure, in a nonintrusive fashion.

© 1985 Optical Society of America