PARTICLE SIZE DISTRIBUTION AT 110,000 FT
135
important degree. Thus, for HASL to fulfill its responsibilities in the
development and evaluation of high-altitude balloon-sampling equipment, particle-size data are necessary in both the design and the
laboratory testing of such devices.
In December 1963 HASL prepared a technical memorandum de-
scribing some preliminary determinations in 1961 and 1962 of the size
distributions of stratospheric aerosols collected at an altitude of about
110,000 ft. In 1963 additional samples were collected with an electrostatic precipitator on two balloon flights, during which the sampling
system operated with complete reliability. This paper summarizes the
results of all the measurements performed so far.
samples of particulate material collected directly on electron-
microscope
grids
were
photomicrographed
and counted for size-
distribution determinations. Because the samples were collected in
conjunction with balloon flight tests of an experimental electrostatic
precipitator designed for another purpose, certain qualifications must
be taken into account in interpreting the results. However, in the ab-
sence of other data for this altitude, the information is presented here
for its use by investigators. Prior to these tests information about the
sizes of stratospheric aerosols was available*!.? only for altitudes
below 100,000 ft.
METHOD OF COLLECTION
Balloon flights to determine the feasibility of an electrostaticprecipitator sampler designed by Del Electronics Corporation were
conducted in Minneapolis, Minn., and San Angelo, Tex., during the
period from October 1961 to June 1963. The sampler was designed
to collect stratospheric aerosols in the region of 70,000to 135,000 ft
for radiochemical analyses. It consisted of a 6-in.-diameter 4-ft-long
aluminum cylinder with an axial corona wire. Air was drawn through
the cylinder by a battery-operated axial vane fan ata rate of either
100 or 200 ambient cubic feet per minute.* The basic componentsof
the sampler are shown in Fig. 1. Collection was made on an aluminum-
foil liner coated with a colloidal graphite suspension on the inner surface of the cylinder. The total collection-surface area was 6 sq ft.
A ‘f-in. strip along the liner in the direction of air flow was not
coated so that, prior to each flight, carbon-coated electron-microscope
specimen grids could be mounted at intervals along the liner. This was
done as an adjunct to the main purpose of the flight tests in the hope
that a sufficient number of particles would be collected for study. How*See paper by P. J. Drevinsky and J. Pecci, this volume