Diamond-like carbon coated ultracold neutron guides

It has been shown recently that diamond-like carbon (DLC) with a sp3 fraction above 60% is a better wall coating material for ultracold neutron applications than beryllium.We report on results of Raman spectroscopic and XPS measurements obtained for diamond-like carbon coated neutron guides produced in a new facility, which is based on pulsed laser deposition at 193 nm. For diamond-like carbon coatings on small stainless steel substrates we find sp3 fractions in the range from 60 to 70% and showing slightly increasing values with laser pulse energy and pulse repetition rate.