To achieve useful total reflection optical systems for imaging and focusing soft X-rays, the mirrors used are required to have smooth surfaces and to increase the grazing angles of incidence. Materials of high bulk density coated on the mirrors can enlarge the grazing angle. Film surfaces can be made smoother by combining materials.

Researchers in Japan have now developed and characterised high density platinum-palladium alloys which give smoother film and better performance as reflecting surfaces (K. Nakajima, S. Sudo, H. Kanda, T Ishii and S. Aoki,Fpn. F Jpn. J. Appl Phys., 1993, 32, (3A), 1275-1278).

Sputter deposited platinum-palladium alloy was characterised by X-ray reflectivity measurements. Grain growth of the polycrystalline platinum film was controlled by adding small amounts of palladium. A platinum-1.8 atomic per cent palladium film has a 1 ~ 6 per cent higher reflectivity than a pure platinum film at grazing angles up to about 1°.