A device for precision neutralization of electric charge of small drops using ionized air

Abstract

For use in our Millikan type liquid drop searches for fractional charge elementary particles we have developed a simple ionized air device for neutralizing a narrow stream of small drops. The neutralizer has been used for drops ranging in diameter from 10 to 25 µm. The width of the produced charge distribution is given by the Boltzmann equilibrium charge distribution and the mean of the distribution is set by a bias voltage.Using the bias voltage, the mean can be set with a precision of better than e, the electron charge. The use of the neutralizer is illustrated in an application to mineral oil drops produced with charges of the order of 1000e. We also show the interesting case of silicone oil drops that are produced in our drop generator with a charge distribution narrower than the Boltzmann equilibrium charge distribution, the charge distribution being broadened by the neutralizer.

Search for Fractional-Charge Particles in Meteoritic Material

“…The apparatus for this search, shown schematically in Fig. 1, consisted of the Lee et al [23] apparatus we used previously, augmented (a) by a device, called a neutralizer, [24,25] that brings the average drop charge to zero and (b) by increased automatic computer control of the drop trajectories. The piezoelectrically driven, drop-on-demand drop generator [26] produced 0.833 drops per second with an average drop diameter of 26:5 m and a short term (one hour) diameter spread of 0:016 m (0.06%).…”

“…However, the precision measurement of drop charge required a very much smaller charge spread centered at zero charge. The neutralizer we built [25] consisted of a still air vertical space through which the drops fell, the air being continuously ionized by a 200 C 90 Sr source. A horizontal electric field is produced across the vertical space by metal plates, the total voltage, V, can be varied from 3 to ÿ3 volts.…”