Two novel plasma diagnostic tools: fiber sensors and phase conjugation

A rapidly developing technology (single-mode optical fiber sensors) and recent fundamental research in nonlinear optics (phase conjugation) both offer opportunities for novel plasma diagnostics. Single-mode fiber sensors can replace electrical wire probes for current and magnetic field measurements with advantages in voltage insulation requirements, electromagnetic noise immunity, much greater bandwidth, and some configuration flexibility. Faraday rotation measurements through fibers wound on the ZT-40M RFP have demonstrated quantitative results, but competing linear birefringence effects still hinder independent interpretation. Optical phase conjugation (in which a phase reversed copy of a laser beam is generated) allows real time distortion corrections in laser diagnostics. Self-pumped phase conjugation in BaTiO3 improves the quality of phase conjugation imagery and greatly simplifies experimentation directed toward plasma diagnostics. Our initial applications are (a) time-differential refractometry with high spatial resolution and (b) intracavity absorption Zeeman spectroscopy