Vacuum System - Ryan Ginter

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Ryan Ginter
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Vacuum System - Ryan Ginter

Post by Ryan Ginter »

Depicted below is the progress I've made on my fusor. In its current state the vacuum system is nearly complete, the only item I'm still searching for is a valve to throttle the turbomolecular pump.

My project started with the purchase of a Leybold Trivac D16E 2-stage rotary vane pump. While it's perhaps excessive for use in a fusor it was listed for a fair price and the seller accepted returns, so I went ahead and purchased it. I encountered quite a few issues after receiving the pump. The first was that it would not start up when switched on. Upon investigation, I found it had become damaged during shipping. The fan shroud and start capacitor were dented, causing the issues during startup.

The motor would not rotate due to the cooling fan contacting the dented shroud. Removing the shroud, I was able to use a hammer and anvil to remove the dent. After replacing the shroud the motor was able to be rotated by hand, so I connected a 6" hose and thermocouple gauge and ran the pump for four minutes. At the end of the run, the pump had reached a pressure of 35 microns.

I removed all oil from the pump and filled it with new, after which I let it run for an hour. At the end of the hour, the oil was again dumped and filled with new. Measuring the vacuum again, it had gone down to 15 microns. The process was repeated once more, after which the pump reached a pressure of 3 microns.

Upon connecting the pump to a vacuum chamber, the damage to the start capacitor became apparent. When the pump is under load for more than a few seconds, it bogs down and stalls. While it would be wise to replace the start capacitor, I have currently been using a right angle valve to slowly introduce air to the pump. Once the chamber pressure drops below 1/2 an atmosphere, the valve can be opened all the way without effecting the speed of the pump.

After searching ebay for a few months, I came across a Leybold TMP 50D and Turbotronik 50 for sale. The items had both been in storage, but came with a reciept for a rebuild they had undergone before being stored away.

I next went about collecting parts for my vacuum chamber. I was debating between building my own spherical chamber or using a 4-way cross when I came upon an MDC Precision 4-Way Cross, 6" sphere on ebay.
PXL_20221211_003156188.jpg
It seemed perfect for use in a fusor and was listed for a good price, so I had to pick it up. Over the course of a few months, I collected various other vacuum components. Once I had collected everything, they were cleaned first with acetone, and then with anhydrous IPA. The 4-way cross had some unknown white powder coating the inside. As this could have been anything, I carefully wiped it up and disposed of it without getting it on anything. Pictured below is the inside of the cross after cleaning.
PXL_20221211_021930736.jpg
After all parts were cleaned and assembled, I realized that what I thought was a 6" - 4.5" conflat adapter turned out to be a 3.38" adapter, So I had to order another to mount my turbomolecular pump.
PXL_20221211_041803134.jpg
After assembling everything, I placed the vacuum chamber on a temporary T-slot fixture.
PXL_20221218_152735133.jpg
The roughing pump fed into a right angle valve and then a T-pipe, to which one end had a Teledyne Hastings DV-6 thermocouple gauge and the other connected to the intake of the turbomolecular pump.
PXL_20221218_010459454.jpg
A few seconds after starting the pump, the thermocouple gauge indicated a roughing pressure of 5 microns.
PXL_20221217_154919135.jpg
Next I started up the turbomolecular pump. As it had sat in storage for a few years, I cycled it through many startups and shutdowns, gradually increasing the rpm with each cycle. Once I was confident the bearing grease was properly lubricating the pump, I allowed it to reach its full speed.

The chamber pressure was measured using an Edwards AIM-S cold cathode gauge. I ran it off my lab bench power supply and measured its output with a voltmeter. After about an hour of runtime, the gauge read just under 2x10^-6 Torr, with the roughing line reading just over 20 microns.
PXL_20221217_180006386.jpg
After this run, air was very gradually reintroduced to the chamber using a mass flow valve, pictured below.
PXL_20221218_152803494.jpg
I apologize for this being a rather long post, I've been working on this project over the past year but only recently signed up to the forums. As a result, I've dumped all of this progress into one post.

I'll be turning my attention to the high voltage system next, though it may be some time before my next update. I haven't decided what the final design will be, but it should be roughly along these lines.
PXL_20221218_022223635~2.jpg
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Richard Hull
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Re: Vacuum System - Ryan Ginter

Post by Richard Hull »

A great report with plenty of fine images. All your final pressures tend to show very good sealing of the system with all components working a one would expect. You will have a fine system when it is time to do fusion. All the best. You obviously read the FAQ on conditioning a used mechanical pump, and got the pump down to a clean and first rate condition on the third oil change without the need to get invasive. You received a good pump that just needed some TLC and it responded.

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
Ryan Ginter
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Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

Thanks Richard, looking forward to it!
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Re: Vacuum System - Ryan Ginter

Post by Tom Hanley »

Looks like some quality equipment there. been collecting for a few years and still not there.
Good luck. Tom
Ryan Ginter
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Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

I've acquired two more parts to add to the list.

A Huntington GVA-250V 4.5" manual gate valve with a funnel shaped 4.5" to 6" conflat adapter.
PXL_20230326_045159586.jpg
As well as a 60kV ceramic feedthrough from MDC Precision
PXL_20230321_223543143.jpg
Both parts were purchased used on eBay.

I've been making some progress with the power supply but I still have a lot of work to do. I'll be using a ZVS driver to run a ferrite core transformer and CW-multiplier, a new post will soon be made to document my progress.
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Richard Hull
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Re: Vacuum System - Ryan Ginter

Post by Richard Hull »

Wow, first rate insulator! You are spending the long buck and getting impressive results, thus far. Good bottoming pressure in a nice plus-ultra system.
You will be doing fusion soon, I hope.

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
Ryan Ginter
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Joined: Fri Nov 25, 2022 9:25 am
Real name: Ryan Ginter

Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

Thanks, Richard

I plan on starting with a lower power system, something like 30kV @10ma. I want to ensure the system will be equipped to handle higher power levels as I gain experience. The high-end components won't be put to full use from the start, but as my goal is to eventually conduct activation experiments I'd prefer to only purchase components once.

With the vacuum side of things being easier to understand, I'm okay with spending the money on quality equipment. As for the power supply, there is still plenty I'm working on properly understanding. For this reason, I'm designing it to be fairly modular so that it can be easily upgraded over time.
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Richard Hull
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Re: Vacuum System - Ryan Ginter

Post by Richard Hull »

Smart man. I have always noted that so many people do not take the time to learn real operation of a fusor system in an effort to rush forward, often doing damage to things or failing to get to fusion. The operation of fusor is somewhat of an art. Once learned it is never lost.

Study the simple magic of controlling the plasma first. Balancing pressure, voltage and current is the key, regardless of any one of those set as a goal.

Might I suggest using air, nitrogen or argon plasmas at first without the turbo running. There will be plenty of time for deep pumping and admission of expensive, hard won deuterium. Practice on a non-fusible gas at between 25 and 10 microns.

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
Ryan Ginter
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Joined: Fri Nov 25, 2022 9:25 am
Real name: Ryan Ginter

Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

Sound advice, as the only purpose of the turbomolecular pump is to maintain the purity of deuterium fuel. I fully intend to take my time learning to control the plasma using air before I make any attempt at fusion.
William Turner
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Re: Vacuum System - Ryan Ginter

Post by William Turner »

Really nice setup!

What is your plan for the neutron detection system?
Ryan Ginter
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Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

I will probably go with a Helium-3 proportional counter. To be honest, I haven't really thought about it all that much yet. I still consider myself a fair ways off from attempting any fusion runs. Ultimately it will come down to whatever deal I find seems the most reasonable.

I have a few pancake probe Geiger counters purchased a few years ago from eBay, I repaired and recalibrated them with a certified check source. Once my power supply is finished, I'll just be using these to monitor X-rays from various locations around the fusor while I learn to control the plasma. After I'm confident with this process, I'll get a hold of a neutron detector.
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Dennis P Brown
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Re: Vacuum System - Ryan Ginter

Post by Dennis P Brown »

How you calibrated those instruments would be of interest here. Maybe write a short post on how you did that in the "Neutrons, Radiation, and Detection" section?
Ryan Ginter
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Re: Vacuum System - Ryan Ginter

Post by Ryan Ginter »

Yeah, I could do that if there is interest. I've only calibrated the digital type, I'm not too familiar with analog detectors but the process of using the source would be the same.

The counts per minute of the detector won't be effected by calibration, that is solely determined by the type of detector and the cross-sectional area of the mica window exposed to the source, or volume in the case of gamma and X-rays of sufficient energy to penetrate the walls of the probe. The calibration is solely to determine radiation dose. This dose measurement will only be accurate to the energy peak of the calibration source material, if you want to use it for another isotope you would need to apply a conversion factor based on the differences in the average energy of the emissions.

While you could probably make a conversion factor to monitor exposure to the X-rays emitted based on the value of your applied voltage, I would take that reading with a grain of salt. The actual emission energies of X-rays leaving the chamber will fall into a wide range of values.
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