||Considering the popularity of reflector-type High Pressure Mercury lamps, it was perhaps a logical development to extend similar principles to the High Pressure Sodium lamp. The first such lamps were introduced in high wattage ratings for industrial lighting by Osram-GEC in 1976, however the design never became especially popular for the reasons explained on that page. GE of America followed suit with a 70W lamp in large R125 bulb for outdoor floolighting applications, and Westinghouse of USA developed another 70W lamp in a dichroic PAR38 envelope to provide a cool light source for the illumination of coal mines, but neither were a great success.
Thorn Lighting instead attacked the commercial interior lighting market, and in 1980 launched this 70 watt lamp in the much more compact R-95 bulb, making it the smallest diameter high pressure sodium reflector lamp ever commercialised. Because of the axially mounted arc tube within an aluminised bulb, a remarkably tight beam with excellent optical control is achieved.
It found favour in certain interior locations which demand high lighting levels and low operating costs, but where colour rendering is not of paramount importance. Typical applications include low-profile ceiling downlight luminaires in such places as corridors or wherever all-night interior security lighting is called for, where the integral reflector permits small and discreet installations. Today it has been largely superseded by compact fluorescent lamps in recessed ceiling luminaires, which can provide very nearly the same light intensity at high efficacy, but with a white light which is generally more desirable in such applications.