264
VARIABLE-FREQUENCY
HIGH-VOLTAGE
SQUARE=WAVE
GENERATOR
\oenttaron
GENERATOR
AEROSOL
IN
1 f
CORONA WIRES
:
OSCILLOSCOPE
4}
-_
x
rt
:
*
GALVANOMETER
.
CHARGING REGION
ION DRIFT SPACE
_.| ION
4
Reread| |
}
|
TIME
$ 20 M
“*
TRANSIT
°
r
D-C HIGH+VOLTAGE
ans
POWER SUPPLY
ION
PLASTIC
SHUTTER
4
GUARD
COLLECTING PLATE
fa SS METAL SHIELD
SCREEN
AEROSOL <-> SMALL
CHARGER
CORONA +=WIRES
JON—]MOBILITY ANALYZER
Fig. 2—Aerosol charger and small ion-mobility analyzer.
Ref. 10) and a radium D radioactive foil with an activity of 500 uc have
both been used with success for producing the bipolar ions needed for
charge neutralization. The radium D neutralizer was used when a very
high aerosol concentration was needed and when it was undesirable to
have the aerosol concentration reduced by the diluting air from the
sonic-jet ion generator.
When aerosol carrying high electrical charges is mixed with small
ions of both signs, the electrical charge on the aerosol is reduced.
However, the electrical charge is not removed completely. If sufficient
time is allowed for equilibrium to be established, the distribution of
charge
on
the
particles
distribution law:'!
f(n) =
where
f(n)
can be shown to be given by Boltzmann’s
exp [- (ne)*/dpkT]
ate OXP [— (ne)?/dpkT]
is
the
(3)
fraction of particles carrying n units of charge
(dimensionless). According to Eq. 3, 99.3% of all the particles of 0.01