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New experiments
All,
I ran a test with the hydrogen thyratron circuit replacing the spark gap
which was interesting. Some may remember that the H2 thyratron was a very
poor performer in the DC power supply tests which I ran over X-mas. As a
matter of fact, it produced no electrostatics from the TC at all, but gave a
perfect text book damped wave of reduced amplitude but good solid RF output
as in a tube coil. This, I then attributed to the fact that the device was
unidirectional and cut off at the first zero crossing in the primary
waveform. Thus, some scheme was needed to prolong the pri/sec exchange of
energy.
Tesla actually had a circuit which he put forward in the CSN on July 2 1899
which held out a bit of promise. Namely circuits #2 and #3 for that date.
For those not in posession of the CSN, I will elaborate.
Imagine a power transformer secondary with the normal gap placed across its
secondary. Now place a larger or smaller than normal (non-resonant) value
capacitor in series with the TC primary. Also, however, place the normal
resonant capacitor across the primary (in shunt).
A one way break (unidirectional- H2 thyratron), when conducting, would allow
the series capacitor, once charged, to throw a large magnetic field out from
the primary. Now the thyratron is off and reverse biased anyway as the
current in the primary reverses (field collapses). This, in effect, throws
the series cap out of circuit. The magnetic energy now collapses back in on
the primary and the shunt resonant capacitor across the primary rings up and
down from that intial enrgy blast from the series cap.
I used a larger C in series, and the system did indeed ring up and down as
predicted and did increase the system spark output, but just by a little.
Amazingly, the system now supplied a steady but slow positive going charge
on the isolated 12" sphere 5 feet away from the TC! I used the Keithley 610C
electrometer, and collected 10^-8 coulomb in 10 seconds.
The waveform captured on a 3 foot long whip antenna 10 feet away was a real
doozy!! It was a normal ring up, but no energy packets were seen, as with
the regular spark gaps. The system had a long nice ring down as did the old
H2 thyratron system, but there were numerous ring ups and downs over 3-4
cycles at the resoant frequency. They came and went many times in the ever
diminishing ring down period. NO trace of a low frequency associated with
the large cap was seen. Thus it appeared to be out of circuit. I might
have a correlation in the lower frequency of the undulating ring down, ala
beat frequency with the larger cap as in an AM signal. However, the tube
did spark back a bit and some conduction in the reverse direction may have
occured. This never happened in the normal circuit tested over x-mas.
The system was a real current hog and drew up to 100 watts with 4,000 VDC
input. This was undoubtedly due to the larger (.028ufd) series cap. The
normal shunt resonant cap was .008ufd. I'll have to try a smaller than
normal cap in series to reduce this current. (maybe a .003ufd)
I hope to produce a future circuit employing two back to back thyratrons to
alleviate the reverse conduction/break down problem in the near future.
This system will have a variable grid turn on pulse width and rep rate for
extensive experimentation on the gap question.
More as I get the data.
Richard Hull, TCBOR