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LOYSEN
Several balloon flights were made during which particle size
samples were collected. The sampler used in the last three flights of
the series embodied improvements based on experience in the earlier
flights; therefore measurements of samples from these last flights
were used for most of the data reported here. The flight series is
identified in Table 1. The relatively few measurements from flights
2556, 2562, 2569, and 2572 were consolidated.
Table 1— FLIGHT TEST DESIGNATION
Flight No.
Date
Location
Altitude, ft
2956
2962
2569
2572
2611
T-781-A
T-796-A
August 1961
September 1961
October 1961
October 1961
October 1962
May 1963
June 1963
Minneapolis, Minn.
Minneapolis, Minn.
Minneapolis, Minn.
Minneapolis, Minn.
Minneapolis, Minn.
San Angelo, Tex.
San Angelo, Tex.
106,000
115,000
109,000
109,006
108,000
106,000
106,000
METHOD OF COUNTING AND SIZING PARTICLES
The grids were examined at HASL in an electron microscope.
Approximately 150 fields were photographed at magnifications ranging
from 300 to 190,000x, depending on the size of the particles. Photographic enlargements were made from the film plates, generally to an
8- by 10-in. size. This resulted in overall magnifications of 1200 to
764,000 x. In all cases particles were sized by equal-area techniques
by using either a series of transparent overlays or a Zeiss automatic
particle counter. Size groups were established in a geometric progression, and particles were classified in each group.
RESULTS
The size-distribution results for the seven tests are presented in
Table 2, and graphical representations are given in Figs. 3 to 6.
Photomicrographs of several types of particles collected by the sampler are included as Figs. 7 to 14. Upon examination of the figures,
the median diameters can be estimated to range from 0.002 to 0.13 yp as
shown in Table 3.
The differences in median size among the four test groups may be
explained by the fact that a large number of particles in some size
ranges were counted from a single or a few photographs. This caused
the distribution to be biased. Correlation of the differences in the size
distributions with the occurrence of weapons tests, the radioactivity