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