Emma - Fusor Number 1. First deuterium run

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Emma Black
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Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Whist I have a few threads going with the fusor, as the first deuterium was run though it this week, though it was about time for a dedicated thread. Huge thanks to everyone on this site for all the help. Looking forward to lots more experiments in the future.

Power Supply - 110v to 33kv oversized potential transformer, rectified and controlled via variac.

Pumps – Edwards Diffstak 700 diffusion pump & Edwards E2M18 two stage vane pump.

Chamber and valves - 4.5” / 2.75 Conflat cross, manual valve for diffusion pump throttle & sapphire precision leak valve for gas inlet. Deuterium generated via the Horizon PEM kit and held in a 60ml syringe. Grid uses a tungsten carbine ring.

Metering – voltage via high voltage probe and meter. Current via nichrome wire shunt, calibrated manually. Low pressure via Edwards Penning gauge. “High” pressure via Edwards Pirani gauge.

Neutron detection via Ludlum 2363 with prescilla probe. CPM/graphs calculated via Andrew Seltzman’s standalone program.

Run details:
First Run with Deuterium
Duration 10 minutes
Voltage 29KV
Current 11ma
Pressure 8 microns
Recorded CPM (With Andrews code): 37.5CPM

Using the Ludlum over several hours the background count seems stable at 5-6 CPM. After several previous runs this seems unaffected when in proper position next to the fusor and operating on hydrogen only.
The 37.5CPM is potentially low and maybe not sufficient to decisively prove fusion is taking place yet, but this was the very first run with deuterium.
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Jim Kovalchick
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Re: Emma - Fusor Number 1. First deuterium run

Post by Jim Kovalchick »

Nice work Emma!
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Richard Hull
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Re: Emma - Fusor Number 1. First deuterium run

Post by Richard Hull »

Emma, A first first rate report. Just the thing we are looking for.

Now: A proton recoil detector is not a great detector for fast neutrons at amateur levels specially at 29kv which is just starting to "get there".
I used this same type of Bicron detector in 1998-99 to detect and claim fusion at 30kv back then. I know its terrible 0.5% to 1% efficiency as well as its gamma reject capacity.

As such, coupled with your claim of a net 10X increase in numbers over a careful background count, I am going to place you in the neutron club. I would hope you can get that voltage and pressure up a bit in future as long as you are strapped to the Prescila probe. I rapidly graduated to the BF3 tube in an Eberline PNC-1 and got far better results, (higher numbers over background, 100X). Finally with the 3He 4 atm. I can get reliable neutron detection at 15kv. (30,000 X over background at 40kv)

You squeaked into the neutron club just like I did using proton recoil detection in a good probe made for a much higher flux of fast neutrons.

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
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Re: Emma - Fusor Number 1. First deuterium run

Post by Matt_Gibson »

I’ve got this Ludlum and can detect neutrons at that voltage, so I’d also agree that you’re seeing them. Congrats!

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Liam David
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Re: Emma - Fusor Number 1. First deuterium run

Post by Liam David »

Congrats! No doubt you're doing fusion. Welcome to the club.

When you push the voltage higher and counts start to increase, do be aware that Andrew's program will lose accuracy due to how the meter accumulates and calculates the dose. You'll want to calculate TIER from the dose directly. Also, the hammer is somewhat sensitive to x-rays. At much higher voltages (>50kV) my unshielded Prescilla probe gave 1-2 orders of magnitude too many counts. Probably not an issue for you yet, but something to keep in mind if you run at a higher voltage in your current configuration. I've managed to push those 30 kV feedthroughs to 70 kV in air with a toroid, so you have lots of headroom. Use low-profile socket head screws to get that extra little bit, and keep things clean.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Amazing I’m so pleased- thank you Richard!

Upgrading the neutron detection is definitely on the list of projects. I want to learn more about the different setups, as my knowledge of detection tubes, amplifier modules, signal shaping etc is very limited and I’m quite keen to get some hands on experience. Plus being able to experiment with moderators and how they effect the counts is really interesting.

Liam, that’s a very good point - sounds like I have some interesting maths to do to when the counts hopefully start to improve. Before I added the torrid you could literally start to hear what I assume was corona discharge. Good to know that you can push these things. Adding a voltage multiplier is also on the future list as well as some cooling, this thing gets warm!

Also I think there may be a minor leak on the deuterium inlet side so think some air is still getting in diluting the deuterium, so plenty of immediate work to do.
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Jim Kovalchick
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Re: Emma - Fusor Number 1. First deuterium run

Post by Jim Kovalchick »

Pushing a feedthrough is not without risk. I pushed one designed for 30 kV in the 40 kV range and ruined it. A small blow through in the ceramic at the throat of the connection with the chamber made the feedthrough permanently unusable. It's a crap shoot. You can try it but don't be surprised when it fails.
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Dennis P Brown
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Re: Emma - Fusor Number 1. First deuterium run

Post by Dennis P Brown »

Congratulations on measuring neutrons and building a very good system. I also get neutron detection at 30 kV but yes, a 3He detector should do better. Jim raises a good point - those feed-thru's have a rating level that should not be pushed. I isolate my feed-thru by mounting it on a large glass disk that is used as the vacuum flange for my chamber.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Yes fair point - I do have a couple of spares but would rather not blow one. Wondering how difficult it would be to make something custom from scratch. A friend of mine is excellent at pottery with a kiln etc. Initial idea would be to 3D print the shape of the ceramic needed, make a mould and then slip cast (liquid clay) the ceramic, before finishing, firing and glazing etc.

Anyway. This morning think I have fixed the little leak, todays short run was a bit better:

Voltage & current - 32kv 10ma
Pressure 9 microns
Average CPM= 64.5 over 6.75 min
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Re: Emma - Fusor Number 1. First deuterium run

Post by Matt_Gibson »

I also push my 30kV insulator to 70kV using a toroid on top and a half toroid over the bolts.

What mR/hr values are you seeing on your Ludlum?

-Matt
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Liam David
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Re: Emma - Fusor Number 1. First deuterium run

Post by Liam David »

When pushing the 30 kV feedthroughs much beyond their rating, cleanliness is paramount. That includes a lack of any metal scrapes or deposits, as well as loose dust. A bakeout can also help tremendously. For those not wanting to go the acid cleaning route, I've found that 30 min - 1 hr in a heated ultrasonic bath works to remove all metal from the insulator. Add Alconox or some other strong cleaner, and after a rinse, it's UHV ready.

Rolling your own feedthrough is definitely a possibility, and I'd certainly follow along with interest. Just be sure that the parts are non-porous and don't have any residual binders, or anything other than ceramic, for that matter.
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Re: Emma - Fusor Number 1. First deuterium run

Post by Matt_Gibson »

Does current (increasing heating) come into consideration when pushing a feed through way beyond its rating? I’ve pushed a 20kV to 54kV and a 30kV to 70kV without any problems, but I also don’t get much more than 10mA at these higher voltages.

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Liam David
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Re: Emma - Fusor Number 1. First deuterium run

Post by Liam David »

I haven't had issues up to 20 mA. The plasma heating load certainly goes up, but these feedthroughs are rated to something like 350 or 450 C.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Matt - I'm getting 2-3 mR/hr and the hammer is 34cm from the centre of the fusor.
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Re: Emma - Fusor Number 1. First deuterium run

Post by Matt_Gibson »

That’s pretty good for 30kV from that distance. I have mine around that distance and get around 8mR/hr pushing 70kV (8mA).

-Matt
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Liam David
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Re: Emma - Fusor Number 1. First deuterium run

Post by Liam David »

Your cathode doesn't look very symmetric within the chamber. Fixing that might help improve rates a little, although with that geometry it might not make that big of a difference. With 2-3 mrem/hr and 34 cm, I'm calculating 2.3-3.4e5 n/s. Not too shabby at that voltage/current.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Yep I know. It's off by a few degrees although it looks worse in the photo than it is. I can only think I must have knocked it during a clean, but didn't initially notice. With the chamber now getting down to 3.5x10-7 mbar I'm reluctant to open it again for the moment.

Feel I should know this but out of pure laziness in asking, what is the equation used for calculating the n/s in this situation? Edit: I should have looked at the FAQ's...it's been a long day.
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Re: Emma - Fusor Number 1. First deuterium run

Post by Luca Aldridge »

Emma,
Well done. The build looks professional and something I’d aspire to. Good luck on improving your flux!
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Thanks Luca, you will get there soon :)

I've been running it few times a day for the past few days now and it seems to be improving by 5-10% better counts each time.

There still must be either a leak or lot of off gassing happening though, as when left overnight, it takes a while for the current to drop at the higher pressures as the deuterium takes over inside. The plasma is an interesting whiteish colour during this stage. This seems to be getting quicker each time as I assume the chamber gets cleaner.

Hopefully I can have a go at some simple activations in the next few weeks.

The raw data from the Ludlum for a short run:

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Re: Emma - Fusor Number 1. First deuterium run

Post by Luca Aldridge »

That’s good, I guess it’s all down to practice.
Data looks good!
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Dennis P Brown
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Re: Emma - Fusor Number 1. First deuterium run

Post by Dennis P Brown »

Is the plasma white or rather a faint blue white? Deuterium tends to be red or a light blue in my experience.

Doubt you have a leak if the system is improving with time; that tends to indicate out gassing and that issue is being reduced by pumping and plasma interactions.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

Yeah it was a blue white glow and was decreasing with each run.

Another one of the rubbish diodes has blown anyway. So while I wait for a better quality replacement to arrive, I opened the chamber to sort the cathode alignment.

Have a look at the colours in the steel, being a small chamber with welds, the heat is very intense.

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Dennis P Brown
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Re: Emma - Fusor Number 1. First deuterium run

Post by Dennis P Brown »

Sputtering of the cathode is normal with a fusor. In mine, the window was so coated it appeared as a high quality mirror. Needless to say, I added a protective glass plate to stop that. Cleaning off the window wasn't fun nor good for the window.

Those diodes are, at best, rated to 20 kV but likely that is optimistic and considering that the voltage rms is a good bit higher then what we measure on a voltmeter, even using two in series (40 kV) isn't really much insurance.
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Emma Black
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Re: Emma - Fusor Number 1. First deuterium run

Post by Emma Black »

I'm not even sure how you would go about cleaning that!

Yep I used 3 of the 20kv ones in series but they still failed in the high 30's. The failure took me a minute to figure out what was going on.

All running fine and the plasma suddenly died. No current. As I increased the pressure in the chamber, the plasma lit up again. Then current suddenly spiked massively and would probably have popped a fuse etc had I not had my hand on the variac to immediately turn it down. The power supply is now outputting AC only and is only able to support plasma at higher than normal pressures.
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Re: Emma - Fusor Number 1. First deuterium run

Post by Matt_Gibson »

I might have missed it, but are you using a ballast resistor? They will save your diodes when current spikes like that. Something like this is a good one:

https://www.ebay.com/itm/114714898756?m ... media=COPY

Also, try to control current via pressure control. Run at lower pressures and very gradually increase to increase current.

-Matt
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