A standlard for ultraviolet radiation.

Photoemission diode standards for accurately measuring monochromatic ultraviolet light intensity (3000 A-11OO A) are described that are also blind to visible ligh (lambda> 3600 A). The standard uses an opaque photocathode of Cs(2)Te and is unique because of its combination of thinness (19 mm), high sensitivity (Q.E. > 10%), time stability, and uniformity of response. Design criteria, construction methods, and difficulties overcome in obtaining a stable, unform, high yield photocathode responses are discussed. Cs(2)Te is discussed in terms of a model for high yield photoemitters.