Laser induced fluorescence diagnostic for measuring small magnetic fields

A novel, spatially and temporally resolved diagnostic is being developed to measure small B fields by detecting Zeeman shifts much smaller than the transition linewidth. This diagnostic technique will be used to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as envisioned for particle beam fusion. High sensitivity is achieved by a variation on the Babcock technique using 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, ΔM=0 fluorescence is not observed, while ΔM=±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 ΔM=±1 absorption transitions into resonance with the laser and shifts the other transition further out of resonance. For small field strengths, the d...