the soil contribution, the thermal "magic number" is multiplied by the thermal-neutron flux divided by 1xi0'* n/em? and added to the fast-neutron “magic numoer" multiplied by the fast-neutron flux (Pu) divided by 1x10°? n/em. This result is miltiplied by k using the formula: tek = YR JR + /3 cos 6 where 9 = angle between normal to surface of ground and path of neutron beam from point of detonation R= os Ca where Ss microscopic scattering cross section of soil o, = microscopic absorption cross section of soil and then multiplied by the build-up factor for soil. The constants for Nevada-type soil are: Thermal "Magic Number" = 523r Fast "Magic Number” = 35lr VR = 8.17 Build-up factor = 1.3 » . 2 10°? 30) 2 13 1x10°? n/en? 1x10"? n/en? 1878r + 3754r = 5632r cos 9 = 500 yds US 1119 yds 1-k =e ys 8.17 + J/3 x 0.447 Ss 0.47 7.17 8.17 + .773 223 = 1-17 8.943 = 0.802