A rapid bolometer made by sputtering on thin films

Thin Films. - The method of making thin films of collodion by drying weak solutions in ether and alcohol on the surface of clean mercury, and their subsequent removal, is described. Flexible films are also made in the same way, using a modified formula, producing very robust films which withstand great distortion, and will stand being punctured without fracture. Both types can be produced rapidly and cheaply down to a thickness of one wavelength of light. Sputtering. - Two novel types of sputtering apparatus are described, together with working data. A table is given containing sputtering data for 25 metals, nine of which appear for the first time. Notes relating to the effects of Shape and Age of Kathode, Shape of Anode, Form of Dark-Space and Kathode Temperature appear, together with novel modifications in the design of the Wehnelt break. Approximate temperature coefficients of resistance are assigned to eight new metals and more accurate values to three others, that relating to gold being new. The apparatus used for these determinations is described. Notes and curves on ageing appear regarding six metals and resistances for films of standard size for ten metals. A curve is given throwing, perhaps, some light on the formation of a sputtered film. Bolometer. - Apparatus is described by which rings are moulded for supporting the thin collodion films and providing a reliable contact for overlying sputtered metallic films. The method of making the bolometers, together with holders of various types, and apparatus for blackening, are detailed. The comparative sensitivity of these new bolometers is discussed, and curves and an empirical formula given from which an estimation of the speed of the instruments can be determined. The new type is roughly 400 per cent. faster than a representative bolometer of the Lummer and Kurlbaum type. The thickness of the component metal film is estimated.