LASER-INDUCED FLUORESCENCE DIAGNOSTIC FOR MEASURING SMALL MAGNETIC-FIELDS

A novel, spatially and temporally resolved diagnostic is being develop ed to measure small B fields by detecting Zeeman shifts much smaller t han the transition linewidth. This diagnostic technique will be used t o measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as envisioned for particle beam fusion. H igh sensitivity is achieved by a variation on the Babcock technique us ing laser-induced fluorescence (LIF) spectroscopy. The LIF from a J = 1 --> 0 transition in a probe species is viewed parallel to B. In this direction, Delta M = 0 fluorescence is not observed, while Delta M = +/- 1 fluorescence is right- and left-circularly polarized and can be measured separately using polarization filters. If a narrow-band pump laser is tuned to a half-maximum point of the unsplit transition line, the presence of the magnetic field shifts one of the Delta M = +/- 1 absorption transitions into resonance with the laser and shifts the ot her transition further out of resonance. For small field strengths, th e difference in the fluorescence signals is proportional to the Zeeman split. (C) 1997 American Institute of Physics.