Memo to L Hemplemann, Subject: Empirical Data - Trinity (Att: Graphs and Handwritten Notes re Same)

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1 naraal boron coated cormtar and a standard alnainun Beta Gamaa counter were eat up outside the south shelter in such a position that there was no obstruction between then and the shot. No appreciable change in background wae observed during the shot Ihnediately after the shot a thin window proportional alpha counter was set up outside the south shelter with the window upward. No alpha activity was observed after the shot or for four hours afterward when the observation was discontinued. * iutenatically recording Beta, Ganna counters were set up at Tularosa, Hot Springs,- San Antonie and Carrisse. These machines showed no activity at Hot Springs, Sanw . Antonie and Tularosa* The enter at Carrlzso went off scale and remained off scale until it was returned 12 hours later. Full scale on this Machine was 10,000 counts One week after tin shot we had collected twenty-four dirt samples from surrounding towns. These samples corroborated the activity found by observers on the spot. None of these sanples showed alpha activity. At the present time none of these samples shew any activity. These sanples are being held in U-l. The attached graphs are a* summary of data taken at the crater. Figure 1 is a plot of intensity in r/hr. on the dates given as a function of distance. It illustrates very well the hump in activity at 800 meters north which was noticed by several observers. These readings are an average of two Instruments which were held at waist height with the chamber facing the crater. Figure 2 is a similar plot of intensity along the south road for the dates given. The inconsistence of the upper end of the curves could be attributed to lack of saturation in the chamber*^on to,the wind blowing the sand. Figure 3 ir a pl§#’0f/Intensity vs. time for the hours given. This data was taken from Figures A and 5 are measurements of green fused sand. This sand wae too active to put in the counter. The samples were placed outside the lead shield which surrounds the G-M tube. Consequently, it does not represent the gross decay curve. Figure 6 is a similar measurement of a clear bead which was found at 700 meters north. Green fused sand still shows activity. A sample 1/8" cube gave 20,000 counts/minute on this date (September 28, 1945) when measured with a standard alminum G-U tube. This includes the Beta activity. We hope. In the hear future, to follow the gross activity of this green sand with a Gamma, Beta counter. RJW-dw PRIVACY ACT MATERIAL REMOVED