Characterization and development of diamond-like carbon coatings for storing ultracold neutrons

In order to determine the suitability of diamond-like carbon (DLC) as a mat erial for storing ultracold neutrons to use in neutron electric-dipole mome nt (EDM) experiments, a number of tests on DLC coatings have been performed . Thin DLC layers deposited on quartz and aluminium substrates by chemical vapour deposition have been characterised by neutron transmission, neutron reflectometry, electron microscopy and neutron and mercury storage and depo larisation lifetime measurements. Two types of DLC have been compared; DLC made by chemical vapour deposition from natural methane and DLC made by che mical vapour deposition from deuterated methane. With these samples we dete rmined the density, hydrogen concentration and Fermi potential of the coati ngs. DLC coatings made from deuterated methane are now succesfully being us ed in an experiment to measure the EDM of the neutron. (C) 1999 Elsevier Sc ience B.V. All rights reserved.