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SESSION II DISCUSSION
The charge on the aerosol which must be taken care of by the
neutralization equipment results from the atomization of the dye solution. Most of the time this charge is a mixture of positively and negatively charged drops. In a few cases we observed a unipolar negative
charge on water and alcohol solutions of dye. As the atomized droplets
evaporate,
the
charge
is
conserved, and what was initially a low
charge-to-mass ratio droplet becomes a high charge-to-mass ratio
solid particle.
charge on the
neutralization
in two steps.
In charging experiments, one must eliminate theinitial
droplet. This is the reason for the elaborate drying and
equipment ahead of the charger. Neutralization is done
First, the evaporating droplets are mixed with bipolar
ions generated by a sonic jet ionizer. After passing through the diffu-
Sion dryer, the solid particles are again exposed to bipolar ions generated by 500uc of RaD. This brings the charge on the dry particles
to near Boltzmann equilibrium. At this equilibrium the number of
particles with positive and negative charges is equal. This is the same
charge equilibrium that exists in the atmosphere on sufficiently aged
particles. It is independent of concentration and depends only on size
distribution.
We use positive ions in the charger because at low pressures the
corona discharge generates a Significant number of free electrons, as
well as negative ions. These free electrons make a calculation of the
charging conditions difficult.
FROM THE FLOOR: Concerning the fission products in the stratosphere, do you think they are charged positively or negatively depending upon whether or not they are beta emitters?
WHITBY: I do not know about the charge distribution of radioactive particles in the stratosphere, but I would suspect that they are
near Boltzmann equilibrium because the charging rate of the particles
due to radioactive decay would be much less than the frequency of
collision with bipolar ions in the atmosphere. Thus they should reach
Boltzmann equilibrium within a few hours.
WALLACE: Dr. Feely’s observations show a rather marked de-
crease of "Sr concentrations with height above 70,000 ft. In view of the
rather vigorous eddies that are known to exist at these levels, I wonder
whether the upward mixing of radioactive debris by turbulence might
play an important role in producing the observed concentration
gradient.
FEELY: The highest altitude sampled was about 105,000 ft. The
activity was decreasing at 70,000 and at 105,000 ft had decreased
markedly. The movement upward of all of this debris would produce
very substantial increases in the concentrations in the region above
100,000 ft, where there is relatively little air. If the debris is mixed