In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.Subject: Re: Neuts!!... 10E4/sec of 'em!
Date: Feb 27, 9:22 pm
Poster: Eugene R. KopfOn Feb 27, 9:22 pm, Eugene R. Kopf wrote:
>All,
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>It was inevitable. I just recorded 4.7 X 10E4 neutrons/sec. I jacked the chamber voltage up to 22kvdc and let the current sit at 5-6ma for 20 minutes, while jockeying the myriad of controls, valves and monitoring a plethora of gauges and meters. It was a wild ride. This time, the fusor was well loaded with D2 and valved off at about 1 micron average pressure.
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> Upon shutting down the system, I immediately ran a 20 minute background check count to go with the 20 minute background check which preceeded the fusor run. These two were averaged and the delta count was ground up in the equation for my counter and range at detection, resulting in the above figure.
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>One interesting thing.... I think I might be the first one to do of this, though it would seem a logical thing to do for anyone with nuclear instrumentation savy. As most of you know, I have been critically concerned with not deceiving myself on the neutron issue and taking heroic steps to avoid a red face.
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>If fusion takes place, even at a low level, the nuclear ash should be detectable. Unfortunately the most intense flux is inside the chamber. What little neutron activation takes place (tiny) would be most vivid inside the chamber. Also 50% of the reaction yields Tritium! I thought, as I noted the TC gauge after shutdown, Hey could I wire this puppy up as a gieger counter reading its own guts??! Why not! I grabbed the Princeton Applied Physics photon counter supply used for the Neutron counter and set the voltage down to about 300 volts. I still had a valve off chamber, remember. The chamber case is grounded, of course. I connected a 10 megohm resistor to the fusor's inner grid lead (after breaking it loose from its HV supply.) To the free end of the resistor, I connected the hot B+ lead of the photon counter. I next placed a .001ufd 4kv disc capacitor on this junction. The other lead went to the signal line of a Radio Shack battery powered audio amp with built in speaker (about $11.00 at any Radio Shack), The amp's shield lead was grounded to the fusor case.
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>By slowly admitting fresh deuterium from the gas manifold up to about 2000 microns or more and slowly raising the voltage to around 500 volts, the tell tale "click", "click" of a geiger counter was noted. The digital counter was attached and this was checked against normal background and was about 2.5 to 3 times above background. Tritium, neutron activation, whatever...we were fusin'!!!
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>However, the power voltage control is touchy as there is little gieger region or geiger plateau in the non-optimum design of the fusor. I found 20 volts one way or the other went from silence, (no counts) to avalache (oscillation/roar)
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>More on this story as it develops.
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>Richard Hull
Richard:
Have you thought about using a prism/diffraction grating and performing spectroscopic analysis before and after a run? You should note some sort of increase in helium spectra.
One parenthetical note about tritium measurement: Tritium is one of the weakest beta emmiters; the betas don't penetrate very far. For that reason, tritium is usually measured with a scintillation counter, not a g-m tube. So, if you want to measure the tritium externally, you may wish to go along this route.