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Sonofusion Being such a small lab, what would be
a routine shift of resources, a regrouping, is a major effort for
us. Changes in materials and equipment are big changes for us. Our
magazine sales and other revenue just barely pay our rent and our
salaries. There is little left over for materials and equipment
for the lab. Since the Crest oscillators are not working for us,
our alternative has been to examine single frequency excitation
via a signal generator and an audio amplifier. In order to do this,
I have loaned one of my audio amplifiers to the lab, a Mackie M-1200,
a two-channel professional sound reinforcement amplifier, rated
at 600 watts per channel into 2 ohms, regardless of the load reactance.
Many tests have been made with the 70
Vp limitation. Aside from NERL's standard reactor, two modified
reactors have been made. The standard reactor uses Roger's cavity
size of 2.5 inches in diameter with a gap between the piezo drivers
of 0.25 inches. One modified reactor has only a 0.10 inch gap, putting
the entire water volume at approximately the same acoustic pressure,
being far below the quarter wavelength of heavy water in the 40
kHz range. The other has a 0.69 inch gap, corresponding to the half
wavelength of heavy water at 40 kHz, hoping to see standing wave
effects. An impedance curve of a Crest piezoelectric
transducer was published in Issue #40. Since we acquired a digital
storage oscilloscope with computer-driven fast Fourier transform
spectrum analysis, I have been able to plot impedance curves readily.
I have found a bewildering variation of impedance which is influenced
by air or water loading, the thickness of the water chamber, single
or double transducer excitation, temperature, pressure, and other
factors. The impedance curve shifts like wind-blown sand in a desert,
plus multiple peaks and dips exist, far more than the 3 tangent
wave-like spikes seen in the published graph (IE #40). Specific
frequencies for uniform testing are difficult to select. A wide range of tests have been done
on all three reactors, with the 70 Vp limitation. Certain frequencies
have been selected, based upon resonant or near-resonant conditions,
where current is in phase with applied voltage at the input of the
LRC circuit. One hundred percent amplitude modulation covers that
one variable, up to 70 Vp. Argon over-pressure has been varied from
0 to 40 psig. Temperatures have not been regulated, but vary from
room temperature to 80°C. Resonances have drifted with a change
in temperature, and the oscillator frequency has been adjusted throughout
each test. All results have been null, typically showing +/- 0.3
watts or less. The next level of higher amplitude testing
has been started with the addition of a 1:1 isolation transformer,
two 5 mH coils on one ferrite toroidal core. This allowed the Mackie
to be operated in bridged mode for a 140 Vp signal. The two channels
are used to drive one load by driving the second channel with a
reversed polarity signal. The load is connected to the "plus"
polarity terminals of each channel, therefore providing a non-grounded,
differential drive. The isolation transformer makes this compatible
with the grounded wattmeter. Though testing by this method has just
started with the 0.1 inch gapped reactor, all tests have been null
so far. Much more can and will be done with various resonance points,
plus the two other reactor types. Maybe the step-up transformer will "put
us back in the ball park." We also have another option for higher
acoustic amplitudes. Thanks to Jan Roos, my semi-retired, part-time
lab partner who comes in about one day a week, another means is
at our disposal. He recognized that two piezo elements can be used
back-to-back in the same transducer assembly with the same polarizing
voltage for twice the acoustic amplitude. Two metal foils form the
electrodes of a capacitor, for which a piezoelectric ceramic disc
forms a dielectric insulator between the electrodes. Three electrodes
with two piezoelectric discs form this new piezoelectric capacitor,
with the central electrode as the hot terminal and the two outer
electrodes as the grounds. The two piezo elements are axially oriented
with opposite polarity, but when electrically polarized by the metal
plates, produce mechanical strain in the same direction, thus doubling
the acoustic amplitude. Preliminary testing shows this is a practical
method. Yet another option is a fourth reactor
housing which was designed by computer finite element analysis for
its vibrational behavior. A maximum axial amplitude was found for
a different steel end cap support of the piezoelectric assemblies,
increasing the available acoustic field even more. That has been
machined and is awaiting lab trials. Gene Mallove has arranged for testing
for tritium of some of our past test water samples. He will be working
with staff at the University of New Hampshire on a Packard 1600
TR liquid scintillation analyzer that is ordinarily used in radon
studies, but which has the capability of accurate tritium counting
too. This direction has been inspired by the sonofusion work at
Oak Ridge National Laboratory, reported in Science (March
8, 2002). Since I am the only full-time lab employee at the moment, and Jan Roos is here one day a week, I feel like a three-legged cat on a tin roof. And NERL has other, proprietary projects in development, which we are not at liberty to mention in public yet. There are good things to come. We just need more support to bring them to life in a shorter period of time.
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