deine Lawn,
static Precipitators, etc., yields particle size distributions that may
have no relation to reality, being artifacts introduced by the sampling
rate, the sampling mathod, the counting technique employed, etc.
3ven
mechanical soil analysis of the NPG area produces conflictingresults.
The median soil particle diameter appears to be a very strong function
of the method employed to measure particle sizes.
The reader should be
cautioned that in this section only the particle size of the soil debris
4s discussed and ne statements are made concerning the particle size
distribution of the cloud aerosol itself exclusive of the soil that is
sucked up into the cload during near surface explosions.
D.
Identifying Fall-out from the Stam and Mushroom of the Atomic
Cloud
A study of Figures 6 through 9 of this report indicates that
there {s a minimim radioactive fall-out area which 1s presumed to have
come from the area between the base of the mushroom and the top of the
stem of the atomic cloud.
The minima’ radioactive zone between the stem
and the mushroom has some reality in ».2servation.
During the tower
shots of T/S and U/K Test Operations =ne clear sky showed through in
this portion of the atomic cloud after 10 to 15 minutes from time of
detonation.
For some unexplained reason the formerly continuous stem
and mushroem appear to separate after 10 to 15 ninutes.
The reader may
have seen movies of air drops where the stem is seen to be discontimuous
with the mshroom from the start, because it forms after the mushroom
has begun to rise,
This is not the proper explanation for this case,
however, because during low tower shots the stem and nushroom are contin-
UEIZbO
C3-ey,
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UATLASSIFiED