Multidirectional Alignment of Liquid Crystals on Polystyrene Surface

Abstract

A method is described for measuring the radon content of three litre samples of atmospheric air without pretreatment. The apparatus used consists of a 12 in. photomultiplier with ZnS(Ag) phosphor and counting chamber. A measured efficiency of 38%, when the phosphor is negatively charged, is in good agreement with theory. The ultimate sensitivity is governed by the background which is equivalent to a concentration of 5 x c I-'.