Laser power stabilization in the TRIUMF optically pumped polarized H- ion source

Power stabilization of the lasers, used in the TRIUMF optically pumped polarized ion source prior to 1991, was crucial to maintaining the laser wavelength and hence nuclear polarization. Output power of the dye lasers was dependent on a number of variables, including the relative drift between the transmission peaks of the birefringent filter and the etalon used to tune each dye laser. The power control system used a program running in a CAMAC crate based PC/AT to control the birefringent filter. Heuristic algorithms implemented to control power and their performance in the steady state and the wavelength shifting modes are described