Titanium Ring Cathode

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Matt_Gibson
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Titanium Ring Cathode

Post by Matt_Gibson »

Hi everyone,

I recently got a neat little titanium ring cathode as well as a SS version using 316L steel.

I’ve been experimenting with the titanium version quite a bit and found odd behavior.

Before, using my three ring tungsten wire cathode, my usual runs would go:
14 microns, 52kV, 13mA, 7.6cm from cathode center, and result in 35mR/hr using my Ludlum Priscilla Probe hammer.

The titanium ring:
30 microns (yup, much higher pressure), 48kV, 13mA, 7.6cm from cathode center, and I’m only getting 6mR/hr.

Once the titanium cathode gets glowing, pressure goes up 5 microns and voltage drops back a bit, while current stays the same.

I understand that the titanium out gases the deuterium, causing pressure to climb, but why am I getting such lousy results? I have the probe placed directly to the side of the beam thinking this is where neutrons would be the highest.

-Matt
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John Futter
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Re: Titanium Ring Cathode

Post by John Futter »

Titanium is used in getter pumps it also stores all the other gas species especially hydrogen from water vapor
Matt_Gibson
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Re: Titanium Ring Cathode

Post by Matt_Gibson »

Hi John,

Would it help to just let it run awhile, or is this just a futile effort?

Trying to decide if I should switch over to the SS cathode or not…

-Matt
John Futter
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Re: Titanium Ring Cathode

Post by John Futter »

Matt
It will come right unless you come back up to atmosphere.
keeping it under high vacuum you should see better and better results as the other gases depar to be replaced with D2 with each heat and cool cycle
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Richard Hull
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Re: Titanium Ring Cathode

Post by Richard Hull »

I agree with John. All things get better in a more or less never opened fusor. Opening and closing to improve things tends to always show a degradation in results until may days of continued operation with the system left under vacuum and unopened. We all want to do better with each improvement that demands opening of the fusor, but give it time to get back to at least where it was. A good operator, over time, will get a feel if the supposed "improvment" is not "taking well".

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
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Re: Titanium Ring Cathode

Post by Matt_Gibson »

Thanks guys, I’ll concentrate on heating/cooling cycles. I’m able to get the cathode glowing pretty good each time.

My vacuum holds pretty well. It’s leaking at a rate of around 0.03 microns per minute. So that hopefully keeps moisture at bay.
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Matt_Gibson
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Re: Titanium Ring Cathode

Post by Matt_Gibson »

Time for an update:

I’ve been doing two “runs” per day and watching things steadily get worse.

A “run” to me is a full 100mL syringe of deuterium. Each run has several start/stops to let my audio amp cool off a bit. I am usually able to get the cathode glowing red hot for a few minutes before my amp shuts down on me.

I let the voltage get up to around 52kV, current up to 12mA, and pressure up to 35microns. I keep it here until the amp has had enough, which is about 5mins.

Each run, I see outgassing start once the cathode glows red and I see pressure climb up 5 microns. By this point, I can also see a hot spot forming in the chamber wall where the beam hits it…Maybe the SS is now outgassing and ruining things? Cooling is just a fan blowing on the chamber.

My typical neutron reads from the Priscilla are during the beginning of the run and max around 10mR/hr and then begin to get worse as I make my way through the syringe.

So, do I keep on forging ahead, or did I figure out that titanium cathodes might not do well in a 4 way cross :-) The SS cathode is looking mighty tempting at this point.

-Matt
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Jim Kovalchick
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Re: Titanium Ring Cathode

Post by Jim Kovalchick »

The characteristics of titanium you are seeing are why I abandoned using Titanium. I tried it as grid material and as a grounded target for beams. At one time I had some much heat induced outgassing that I shutoff my deuterium supply and still had pressure running up. More gas made more current which released more gas. I had to turn of my high voltage to get it to stop.
Matt_Gibson
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Re: Titanium Ring Cathode

Post by Matt_Gibson »

Jim,

I fortunately don’t have it that bad. Cutting off my deuterium supply causes pressure to drop very quickly to below “zero” (my gauge goes to 0.1 microns).

Reducing power causes it to drop back to 35microns.

It would seem that it should be doing way better with operating pressure up around 35 microns compared to what I could manage with the tungsten wire cathode.

The rest of my capacitors arrived for my new multiplier, so I have that to distract myself with while I keep working this titanium cathode some more. I may see how it does at a much higher voltage and then pull it at that point.

-Matt
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