Our progress

For posts specifically relating to fusor design, construction, and operation.
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David Lloyd-George
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Joined: Mon Apr 24, 2017 2:36 am
Real name: david lloyd-george

Our progress

Post by David Lloyd-George » Sun Dec 30, 2018 10:29 pm

we have made some progress with our fusor efforts. We bought a vacuum pump from eBay. the model is a a Trivac D8A. We inspected it using the very helpful guide on this forum and put new vacuum oil in. The oil used is VacOil 19 grade and we filled and drained the pump with this oil a few times to clean it out fully. The pump seems to be working well however we do not have a working vacuum gauge at the moment.
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We had bought a 6in CF flange T-fitting a while back but decided to go with a 2.75CF flange 5 port chamber instead because of the price and availability of similar fittings. We constructed our chamber with a 2.75CF butterfly valve and an air cooled diffusion pump which we haven't used yet but have taken apart and inspected. The heater element has an electrode that is missing but we were still able to test it and it seems to function properly. We have done several pump downs with our roughing pump however, we have been unable measure due to the lack of a vacuum gauge.
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We have ordered a vacuum gauge and a HV feedthrough and are expecting those to arrive soon. We hope to be able to achieve a basic plasma within a few weeks.

Thank you,
David Lloyd-George and Beauregard Pearl

Pablo Llaguno
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Joined: Sun Feb 05, 2017 11:00 pm
Real name: Pablo Llaguno

Re: Our progress

Post by Pablo Llaguno » Sun Dec 30, 2018 11:14 pm

Looks good! If I may ask, where did you get that nice air cooled diff pump? Those are hard to get nowadays :)

Also, for the vacuum gauge I highly recommend the MKS 901p transducer, I have a post (and also others) on how to set it up very easily with an Arduino board and LCD/OLED display, very cool little gauge that works very well!

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Richard Hull
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Real name: Richard Hull

Re: Our progress

Post by Richard Hull » Mon Dec 31, 2018 3:34 am

That little diff pump is as cute as a button. It should serve well in the smaller chamber you now plan to use.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

David Lloyd-George
Posts: 8
Joined: Mon Apr 24, 2017 2:36 am
Real name: david lloyd-george

Re: Our progress

Post by David Lloyd-George » Fri Mar 15, 2019 7:14 pm

We have made some progress in our efforts. After buying a Teledyne Hastings DV-6M gauge and controller, we tested out our pump. We connected the gauge directly to the inlet of the pump and after 20min of pumping, we had hit 15mTorr. Since we have two TC gauges, we corroborated our results with the second one and got approximately the same values after 20min. We then tested the vacuum chamber however we got significant leaks in the inlet of the diffusion pump. We added some teflon tape onto the inlet however that didn't stop the leaking by that much.
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(vacuum gauge readout at ~12mTorr)
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(our setup for pump testing)

In regards to the other parts for the fusor, we have made some progress as well. We now have a better X-ray transformer capable of outputting 100kv @ 10ma (we still have to do further testing though) and we have bought a 30kv high voltage feedthrough along with ceramic tubing to use as an insulator.
We have bought a 60KΩ 225W wire wound resistor that we will use as our ballast resistor. 50kv high voltage wiring and 30kv 100ma diodes were purchased as well.
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(X-ray transformer)
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(feedthrough with ceramic tubing on stalk)

Any comments or questions about anything would be much appreciated.

Thanks,
DLG & BP

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Richard Hull
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Re: Our progress

Post by Richard Hull » Sun Mar 17, 2019 10:07 am

It looks as if your materials on hand are just fine. Good luck.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

David Lloyd-George
Posts: 8
Joined: Mon Apr 24, 2017 2:36 am
Real name: david lloyd-george

Re: Our progress

Post by David Lloyd-George » Mon Mar 25, 2019 3:58 pm

We have been able to achieve some more results in our journey to fusion. After buying a few more flanges and components, we were able to test our main chamber. We pumped down for ~30min and managed to get a vacuum of around 12mTorr. We were very happy with this result considering that it was very close to our final vacuum when testing at the pump inlet. We can therefore say that we have no significant leaks or other issues with our vacuum at this vacuum level and chamber set up. We haven't tested our diffusion pump yet as we do not have oil yet and considering that 12mTorr should be just fine for a demo set up, we shouldn't need it yet.
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(our set up used for vacuum testing)

We put together our high voltage system and followed a design similar to that of Andrew Seltzmann's. We used our 30kv diodes and decided to do a full wave rectified negative output. We built our mount for the transformer out of HDPE and used 1/2in PVC for the beams. We then placed the whole set up in a 5 gallon bucket and filled it with mineral oil. We then set up our electrical measurement systems. We will describe these in detail in another post in the HV section but the general gist is that we made our own HV divider and will be using a multimeter to measure the output. We are doing the same thing with the current metering and are using a 10Ω 25W shunt resistor with a multimeter to measure the voltage across it.
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(X-ray Transformer in mount)

All of our main equipment will be housed and put inside a 2 X 2 X 2 cube that we have constructed from 1in aluminum square tubing. this is also where
our main ground will be and all of the necessary equipment will have wires running to this point. We will then run a wire from this to earth ground. All of our ground wires are on a single bolt together.

As always, please feel free to comment or ask questions if any clarifications are needed.

Thanks,
DLG & BP

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