Introduction: DIY Ultra High Vacuum Research Project

This Instructable will detail a project I have been working on for many years to accomplish, This is a high science project done out of my sheer wish to learn. I desire no monetary gain, this is not a college project nor is it aimed at any specific goal. This is a personal project that was simply started out of my desire to understand the nuance and complexity in the various subjects of physics you typically only get to see in universities.

I learn in many ways, but actually doing physical projects that require me to expand my abilities teach me the most. I took interest in this project some years ago after seeing a video of Ben Krasnow's on an ultra high vacuum system used for an electron microscope which he has also used for DIY sputter coating to make conductive glass. This project was very far outside my realm of possibilities and experience at the time, so I decided to start my own project from the ground up, engineer every part and work out every issue on my own to expand my knowledge of engineering and science. You don't just learn from the research I want to do with this project, you learn so much about engineering which you can apply to other parts of your life.

Other people have done projects like this before, but I want to do this as professionally as possible, as if I was doing this in a university setting, so I can learn as much as possible, on a very meager budget.

Step 1: What Is This?

This project is intended for multiple uses, and is designed to be partially modular to enable a variety of experiments to be carried out. The first proof of concept experiment of this system will be a Farnsworth Hirsch Fusor. This system will be able to achieve a very high level of vacuum capable of making a very functional fusor. The Vacuum chamber's upper window will be exchangeable to set it up for different experiments, for example, when set up as a fusor there will be a high voltage feedthrough in the upper window for the inner grid and Deuterium gas backfill.

Another use for this project could be for coating glass with metal via the sputtering process to create DIY LCD panels. Creating thin film transistors, or partially silvered and fully silvered first surface mirrors for use in laser systems.

Step 2: Components

This Ultra high vacuum system utilizes a retired 4 inch water cooled Daia DPF-4z oil diffusion pump and 2 stage rotary vane pump to achieve very high levels of vacuum. The Diffusion pump is majorly overkill for this project, but it was found for a great deal on ebay, and was impossible to pass up.

The Rotary vane pump is a harbor freight special pump, made by US general. It isn't the highest quality pump, but it will be operated relatively rarely, and only used to pump air, and not refrigerants as it was originally intended.

A Varian 841 vacuum Ionization gauge was acquired on ebay for a small price is questionable condition, with the intention of repair as sub small project. Repairing old equipment like this and integrating into your designs are a great way to learn about how to fix electronic devices and engineer your own!

The actual vacuum chamber is a CF flanged tube from a larger system also acquired from ebay, but as we do not need a large chamber volume, this small chamber will work perfectly.

There is also a cooling system for the pump, various electrical work, an adapter plate that needed to be machined to interface the pump to the standard CF flange chamber.

Step 3: The Diffusion Pump

The most integral part of this system is the diffusion pump, used to increase vacuum levels farther than mechanical means can achieve. A roughing pump, the US General rotary vane pump pulls the initial rough vacuum needed in the chamber and the diffusion pump, and the diffusion pump then activates as the second stage, increasing to the final vacuum level.

This specific diffusion pump operates on the oil diffusion principle for gas molecule removal, by which in the bottom of the diffusion pump, oil is boiled and vapor travels up the chimney, and the vapor is ejected out to capture as many gas molecules as possible, and fired downwards towards the outlet of the pump to carry the gas to the mechanical vacuum pump. Now, we do not want this oil splashing into the main chamber, so there is a liquid cooled baffle used to cool and condense the oil before it can get into the chamber.

To mate this Japanese made pump to the standard CF flange chamber, I needed to engineer an adapter plate out of aluminum. I used a CNC machine to mill out a plate of MIC-6 toolplate to keep a perfectly flat surface, as the o-ring mating surface needs to be perfectly flat, while supporting the weight of the pump and chamber.

Step 4: Connections and Cooling

The system after being adapted then needs to be mated, the pump head has an o-ring groove for sealing against the bottom of the plate, and the plate has a groove machined to seal against the bottom of the vacuum chamber. High vacuum grease is used to properly seal the o-rings against the mating surfaces. The diffusion pump then had its outlet tube modified to connect to the roughing pump.

This diffusion pump is large, and subsequently liquid cooled, so a water cooling system must be utilized. I made a water cooling loop by modifying and reusing an old office water cooler, and adding a pump and cooling lines to connect up with the diffusion pump. This water cooler has a stainless steel bucket that contains the liquid, in this case methanol, with the copper refrigerant coils wrapped around it, and a ceramic pump that pumps the cooled liquid around water jacket of the diffusion pump, and then returns it to the bucket to be cooled again.

The water cooler was picked up from its way to the dump, and was modified in the following ways, the entire cooler was shortened to half its height by folding the coils over on the back of the unit, and the entire system was cut in half, removing the water filter unit. A small water pump from eBay was installed, and plumbed into the system. The electrical system was then modified to power the pump when the cooling is on, and the thermostat turned down to prevent overcooling.

Step 5: What Needs to Be Done

This system is a work in progress, one I wanted to share as there has been a lot of progress, and a lot more needs to be done. I need to repair the and configure the vacuum gauges, machine acrylic windows and bolt the system together and seal it. The pump needs to be cleaned, oil put in, and put on a step down transformer (Japanese 100v pump)

To set this system up for fusion, An inner grid will need to be made, fed through the upper chamber window, and a bottle of deuterium gas purchased and a backfill valve integrated into the system. A high voltage transformer will be used to create the electrostatic field necessary for fusion.

Comments

author
43totheN made it!(author)2016-02-14

Nice project! Definitely educational, fun, and also a really cool thing to have in the garage. :)

A few tips that might save you some hair:

Below about 10^-6 Torr the seal types become very important. Plastic/rubber seals allow noticeable amounts of gas to diffuse through them. How much varies from plastic to plastic, with Teflon and Viton generally considered to have the lowest diffusion coefficients. There are certain vacuum compatible epoxies available for permeant seals as well.

Also, below about 10^-4 Torr the gas remaining in a vacuum chamber is mostly water. The water sticks to the internal surfaces and gets pumped out very slowly. The water can be driven off with external heat or internal UVC (aka germicidal UV) to achieve a lower ultimate vacuum.

If you need to weld anything exposed to vacuum, TIG/Heliarc is the way to go. That's the only technique that doesn't produce pinholes or 'virtual leaks'.

Finally, FYI back in the day they used to use solder and copper pipe to make vacuum connections and it seemed to work fairly well. However this method has been abandoned in modern labs, probably for the same reasons as why we use TIG welding.

You can also get vacuum parts, particularly things like ion gauges, from Duniway Stockroom. They're a pain to deal with (you have to call them on the phone for everything), but they do make good products.

author
SpectrHz made it!(author)2016-02-14

Thank you for all this information! I wasn't aware of the issues with certain seals, I was just going to buy buna-n o-rings, but will definitely try to find viton or the like. I will most likely have a set of high current coils that get wrapped around the chamber to produce some heat and drive off water, however it can double as a plasma cleaner if I backfill with other gasses and use a high frequency.

Speaking of Duniway, they are fantastic, they provided me with the manual and circuit diagram to my old Varian Ion gauge controller.

author
TheThinker made it!(author)2016-02-14

I appreciate your approach to this project! You will go far with an attitude of learning like this.

author
SpectrHz made it!(author)2016-02-14

Thanks so much! :)

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Bio: Maker, Engineer, Geek Girl.
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