1.0 a) ” 6 = ae oO a w 5 >= 4 oa a \ am oes \ 0 10 20 30 40 50 60 70 ANGLE 6 (DEGREES) FIGURE 3-3. RELATIVE RESPONSE OF THE HPGe DETECTOR MOUNTED IN ITS NORMAL FIELD CONFIGURATION (WITH COLLIMATOR)}) FOR 60 keV GAMMA RAYS AS A FUNCTION OF INCIDENT ANGLE (ZERO DEGREES BEING DIRECTLY BELOW THE DETECTOR). Conversion factors are given for the average 241 4m concentration in the top 3 cm. The detector angular response, R (6), was obtained with the Pb-Cd collimator in place from the data shown in Figure 3-3, pCi/g 44 The final 241Am conversion factor (8.95 ) was obtained for a detector height of 7.4 m, a soil density of 1.5 g/em? and an air density of 1.15 (1073) g/em®, A weighted average was used to account for observed variations in the depth distribution. The actual 241Am conversion factor used in the Enewetak field program was 7.7 ee . This value was based on a soil mass attenuation coefficient of 0.248 em2/g, which is typical for many soils, and a soil density of 1.2 g/em, A detailed study of the soil composition and soil density at Enewetak conducted in December 1979, however, led to a revised value for the soil mass attenuation coefficient and soil density. All final data based on the IMP results given in this report have been corrected for this error. (See Tech Notes 22 and 23 for more detail.) In the following section, each of the input parameters to Equation (8) is discussed in detail Errors in the conversion factor associated with variations in each of these parameters are also discussed. 91