"m=1" coatings for neutron guides

A substantial fraction of the price for a supermirror neutron guide system is the shielding, which is needed because of the gamma radiation produced as a result of neutron absorption in the supermirror layers. Traditional coatings have been made of nickel-titanium heterostructures, but Ni and Ti also have a fairly high absorption cross section for cold and thermal neutrons. We examine a number of alternatives to Ni as part of a study to reduce the gamma radiation from neutron guides. Materials such as diamond and Be have higher neutron scattering density than Ni, smaller absorption cross section, and when a neutron is absorbed they emit gamma photons with lower energies. We present reflectivity data comparing Ni with Be and preliminary results from diamond coatings showing there use as neutron guide coatings. Calculations show that Be and diamond coatings emit two orders of magnitude fewer gamma photons compared to Ni, mainly because of the lower absorption cross section

"m=1" coatings for neutron guides

A substantial fraction of the price for a supermirror neutron guide system is the shielding, which is needed because of the gamma radiation produced as a result of neutron absorption in the supermirror layers. Traditional coatings have been made of nickel-titanium heterostructures, but Ni and Ti also have a fairly high absorption cross section for cold and thermal neutrons. We examine a number of alternatives to Ni as part of a study to reduce the gamma radiation from neutron guides. Materials such as diamond and Be have higher neutron scattering density than Ni, smaller absorption cross section, and when a neutron is absorbed they emit gamma photons with lower energies. We present reflectivity data comparing Ni with Be and preliminary results from diamond coatings showing there use as neutron guide coatings. Calculations show that Be and diamond coatings emit two orders of magnitude fewer gamma photons compared to Ni, mainly because of the lower absorption cross section

Tribological study of diamond coatings on titanium alloys

International audienceThis paper presents the tribological characteristics of PACVD diamond coatings on titanium alloys. The coating morphology and quality have been investigated by SEM and Raman spectroscopy, and the surface roughness has been determined by AFM measurements. Friction and wear characteristics have been studied with a pin-on-disk tribometer as a function of the applied load, the sliding speed and the counterface material. For diamond-on-diamond contact, the dynamic friction coefficient stabilizes at a value of 0.05-0.08 after the surface polishing of diamond crystal tips. For non-diamond coated pins, a surface running in time at low sliding speed is necessary to avoid a coating spalling on the disk. After this step, the sliding speed can be increased to 1 m s(-1) with a friction coefficient equal to or lower than 0.1. The wear of the diamond-coated disk generally cannot be measured