3_12_18 first good rf neutrons

For Farnsworth type designs.

3_12_18 first good rf neutrons

Postby Doug Coulter » Mon Mar 12, 2018 6:08 pm

Well, interesting day. Got the fusor up with the RF drive, way NOT optimized, but got some decent neutron counts. From the scopes and the data, in this mode it's a little lower Q average (see the grid heating, and this is on ~360w input to the driver, so less to the grid) but some really good peaks when it drifted into a good timing.
Sadly, this run also took out the 2nd $80 chinese power supply for no obvious reason. Doesn't seem to matter which vendor on amazon...it's the same innards, and this fried at 6 amp output - rated at 10. I'll try to get a post mortem on these and see if they are repairable.
I found running the stepup transformer off resonance (which is also lower effective stepup ratio) seems a bit more efficient - Less heat in things not supposed to get hot an any rate - and off resonance is most of the available frequency range. Really high frequencies seem to have the parallel resonance issue and I just could not get much voltage output (didn't draw much input current either). If that turns out to be where we want to be, I'll hope some external C or L will help there.

To the pictures:
big scope

Green is the furthest faraday, which has a semi loaded ion grid "in the way" - the DC ion supply is wired up, but not on, shielding this one a little bit I'd guess.
Blue is the near faraday probe - the one that looks like a 2.4 ghz antenna (it is that too).
Violet is an ac coupled pickup a few inches from the end of the HV feedthrough (near the tank end).
Yellow is neutron (hornyak). When this is clipped, like here, it seems to mean a neutron burst.
Yellow is HV probe on grid. Blue is xfrmr input one side.
ss2.PNG (8.38 KiB) Viewed 289 times

Some data in the db for this one.

I was running 60 to 65 khz in this (before the DC PS fried). It looked to me like about 1/3 of the grid volts were positive, and 2/3 negative, corresponding very roughly to +10 kv and -20 kv here.

The grid got pretty hot - hotter than it does with the normal DC conditions for the roughly same drive power (here I only know what I put *in* to the stepup xfrmr, or that minus the wires from the PS, which get warm...)
The grid at equilibrium
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Doug Coulter
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Location: Floyd county, VA, USA

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