Silane coatings for laser-driven polarized hydrogen sources and targets

It is necessary to use special coatings on the surfaces of volumes containing polarized atoms in order to minimize depolarizing spin interactions during wall collisions. We are studying coatings of organosilicon compounds that preserve hydrogen and potassium polarizations and prevent molecular recombination of hydrogen during wall collisions in a laser-driven polarized hydrogen source. Continuing problems with coatings for these sources has been the reproducibility of high-quality surfaces and reliable assessment of surface quality before installation of coated parts in the laser-driven source. We have used an atomic force microscope to scan surfaces coated with different organosilicon compounds with the goal of assessing surface quality and determining a method of preparing reproducible surfaces that do not degrade with time. Here we show AFM scans of the different coatings, discuss the quality of coatings made with different chemicals and application procedures, and present the results of coating stability tests as a function of temperature and exposure to potassium. We find that a simple organosilicon afterwash gives a significantly improved surface.