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Re: Joe Gayo's Fusor

Posted: Mon Jan 14, 2019 6:21 am
by Richard Hull
No! I am talking about two full and complete fusion runs as close to identical as possible. Same voltage, current and D2 pressure, (as close as possible), and the exact same run times. The only difference being is that one run is made with moderator and tube together as a neutron measuring run and the other full fusion run with the moderator removed to some distance and just the naked tube doing the counting at the exact distance from the fusor as in the run with the moderator and tube.

I hate having to keep reiterating all of this. This is to see if you are really counting neutrons.

Check out the dramatic example - the second Tuesday follow up run.

viewtopic.php?f=18&t=7893

Richard Hull

Re: Joe Gayo's Fusor

Posted: Mon Jan 14, 2019 6:31 am
by Joe Gayo
I think we said the same thing ... with and without the moderator ...

I was proposing an additional test without Deuterium but thinking about it, that isn’t valuable

And if you are a forum moderator for 18 years, you will probably repeat yourself a lot

Re: Joe Gayo's Fusor

Posted: Mon Jan 14, 2019 6:47 am
by Richard Hull
The only real value in an air, nitrogen or argon test, (no deuterium - tube in or out of moderator), is if you get many counts, you have a nice x-ray detector and not a neutron counter.

However, if you have already run deuterium over time, some D is buried in the shell and you will get some limited fusion as they exit the shell walls under bombardment in an air run.

It is best to just do a couple of tube-in / tube out runs. We don't really need CPM values, just gross counts as both runs are of the exact same time frame.

Richard Hull

Re: Joe Gayo's Fusor

Posted: Mon Jan 14, 2019 6:08 pm
by Joe Gayo
I've done this test before but I re-ran this morning (detector in same relative position to fusor for all tests, 10cm) -

30 minute background with moderator: 24 counts

No moderator / No activation oven (within 3m):
28 mTorr D2
35kV @ 10mA
90 seconds, 274 counts
(note: pulse has leading negative component and positive amplitude prohibits discrimination ... windowing might work)

Moderator:
28 mTorr D2
35kV @ 10mA
90 seconds, 2506 counts

Re: Joe Gayo's Fusor

Posted: Tue Jan 15, 2019 3:54 am
by Joe Gayo
Based on looking at the pulse waveform from the amplifier with an oscilloscope I was able to setup a window discriminator (2.1-5.9V) to reject the majority of events that occur without a moderator. It does appear that most non-moderator events have a leading negative voltage spike and a subsequent >6.5V event.

29 mTorr D2
32kV @ 12mA
90 sec without moderator: 3 counts
90 sec with moderator: 291 counts

Re: Joe Gayo's Fusor

Posted: Tue Jan 15, 2019 1:09 pm
by Dennis P Brown
Nice work. Your detector system has a good bit of noise. I enclosed my neutron detector tube in a copper tube, electrically sealed both ends and had almost zero noise issues; however, rejection works as well. I'd like to see your activation results if it isn't too much extra work (and not needed - your current results are good) - Ag activation really shows you have a high neutron flux.

Re: Joe Gayo's Fusor

Posted: Tue Jan 15, 2019 4:14 pm
by Cristiano_Machado
Dear Mr Brown,

Sorry for my ignorance, but how do you "electrically seal" a tube? I would like to test this on my detector.

Thanks,

Cristiano

Re: Joe Gayo's Fusor

Posted: Tue Jan 15, 2019 5:49 pm
by Dennis P Brown
I solder two copper end caps on the copper tube (the neutron detector is inside. I placed some electrical tape around both ends of the detector tube a such that it (the tube) makes a semi tight fit inside. Don't want it moving around.) One end has a proper co-axial connector fitted to the cap. The inside is connected to the neutron detector and the outer one gets your detector coaxial cable. Works extremely well.

Re: Joe Gayo's Fusor

Posted: Tue Jan 15, 2019 7:43 pm
by Cristiano_Machado
Thank you for the instructions. I will test that!

Re: Joe Gayo's Fusor

Posted: Wed Jan 16, 2019 3:22 am
by Joe Gayo
I think it's x-ray detection not noise.