" UNCLASSIFIED Department of Defense agencies utilizing the threshold-detector technique. The results as tabulated are for all miclear weapons tests from Operation TUMBLER-SNAPPER (1952) through Operation HARDTACK (1958). The data are for all clear line-of-sight measurements. Neutron-dose information is presented where sufficient neutron-flux data were available to permit its calculation. It is expected that this compilation of data will be helpful to those whose work entails use of such measurements. CWLR - 2378 - A PORTABLE LOW-LEVEL ALPHA COUNTER FOR FIELD USE. A. Lind and J. C. Goshorn, Jr., March 1960. UNCLASSIFIED (u) In radiological work involving alpha emitters, a system should be available for detecting low-level alpha contamination. One of the preferred methods for detecting alpha contamination in the laboratory has been the swipe technique. If a portable instrument were available for reading the swipes, this method could also be employed in the field. In order to develop an instrument suitable for field use, a survey meter with an air proportional probe, muclear Chicago model 2111 (Pee Wee), has been modified so as to result in a scintillation-survey meter with an enclosed chamber. The modified survey meter uses an end- ~ window multiplier-phototube and a zinc sulfide phosphor mounted in a housing suitable for counting swipes. The swipe technique involves swip- ing the area suspected of contamination with a small piece of filter paper. The paper is then placed in the housing of the chamber and counted, The modified instrument when used with swipes provides a reliable method of detecting very low levels of alpha contamination in the field. Very low levels of alpha contamination can be detected because the geometry of the chamber, and the elimination of a window, provide an overall counting efficiency of approximately 70% of 2x with a U30g standard. wr rg The portable alpha counter enables one to extend the very sensitive swipe technique of detecting alpha contamination to areas only accessible with a portable instrument. The modified instrument is convenient, sensitive, stable, and requires a rinimum of maintenance. WNRC UNCLASSIFIED 66