they were positioned amounted to approximately 10 percent based upon measured results, and the error in converting film dosimeter readings to quartz-fiber response is about 10 percent. These errors combined to about 30 percent for overall accuracy. In individual cases where the residual-gamma contamination was proportionately larger, the accuracy may be reduced, particularly in those cases where the residual-gamma contamination was estimated. These cases are discussed individually as they appear. The photographic and quartz-fiber dosimeter readings are generally recommendedas being most reliable on a statistical basis, since they were put out in large numbers and in many ranges at each station location. Statistical variation for these individual detectors was within 10 percent. The residual-exposure values, after correction for shielding effects and energy response, should be accurate to within 50 percent. This accuracy is based primarily on variations in the individual dosimeters due to response characteristics and station shielding effects. The variance of a particular type of dosimeter at a given location was 15 percent. 2.3.1 Initial Exposure Calibration. The radiation spectrum of a 10-Mev betatron (3.5-Mev effective average energy) is believed to approximate the initial spectrum of a nuclear detonation. To normalize exposure readings from a film dosimeter based on Cocalibrations to the energy Se Distance, cm ~— 10 1 fo ot ttt 10 i.op Ft tt to2 1 jt ti tit Exposure Rote ,r/hr 105 al eal SN 104 10 Figure 2.6 200 curie Co™ calibration curve. of this betatron, field exposure values are multiplied by a normalization factor. To obtain such normalization factors, NBS has exposed photographic dosimeters to Co® and to the Naval Ordnance Laboratory (NOL) 10-Mev betatron on several occasions in the past 5 years (References 2, 3, 4, 15, and 25). Examination of these results showed that the normalization factors were a function of the particular photographic emulsion, batch, and age. The betatron calibration planned for the Operation Redwing film emulsions could not be accomplished because of schedule difficulties among NBS, NOL, and this laboratory. Comparison of Co" calibration curves for the various Operation Redwing emulsions with similar curves for Operation Teapot indicated so little change that the Operation Teapot average betatron normalization factor (0.863 + .031) rounded off to 0.9 was used for all Operation Redwing emulsions. Air Force Special Weapons Center (AFSWC), in cooperation with Los Alamos Scientific Labo~ ratory (LASL) and Evans Signal Laboratory (ESL), exposed film to the Godiva bare assembly at Los Alamosin order to study the effects of neutrons on photographic emulsions. Results indicated that the film sensitivity for neutrons was relatively low. This experiment also yielded additional data on rate dependence of these emulsions in that there was no significant change in emul- sion response due to a gamma rate of exposure of 1 r/sec as compared to 10% r/sec for equivalent total exposure. 22