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In the rocket samplers some breakup of the fallout particles was thought
to be likely in passng through the shock front in the diffuser throat,
A series
of experiments carried out by NRDL on the shock tube at the University of
California Engineering Experiment Station indicated that coral fallout grains
were not fractured by Mach 2 shock waves (Reference 58).
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:
/
Impact with the
4
filter is another possible cause of particle breakup in all the sampling de-
i
vices, but little or nothing is known about this effect.
2.3
DESCRIPTION OF FIELD OPERATIONS
2.3.1
Meteorology.
It was indicated in section 1.3.3 that samples to
be used for the determination of fallout partition by the UCRL method should
be collected from the light and variable layer, if well defined, or from higher locations in the cloud.
The cloud heights and wind structure in the upper
atmosphere are therefore important characteristics to consider in devising
operational plans,
It is known from previous work that the clouds rise toa
maximum altitude in the first few minutes and then settle back toa "stabilized" level.
Based on height-yield curves derived from photographic data on
earlier shots (Reference 21), it was estimated that the stabilized altitudes
would be around 72,000 feet for Koa and Walnut and 99, 000 feet for Oak
(Reference 59).
The altitudes observed by project aircraft were considerably
lower (Reference 60).
A radar record for shot Koa indicated that the cloud
rose to 72,000 feet at 5 minutes and then settled rapidly (Reference 61).
The light and variable layer existed for all the shots, being possibly
50