Re: [DIYbio] How cheaply could you DIY a high-vacuum pump...

Thought experiment: what is the lower bound on the cost of making a DIY high-vaccum pump, say with a budget around $500?

Let's define "High vacuum" as 100 mPa - 0.05 mPa.

Jürgen Gross provides a good introduction to the vacuum ranges and requisite pumps used to create them for Mass Spec in "Mass Spectrometry: Ch4 Instrumentation" (Springer, libgen).

In "Working in a Vacuum" (The Amateur Scientist. Sept 1996. Scientific American), Shawn Carlson described the construction of DIY sorption pump that was surely less than $500 in materials and could reach ~1.33 Pa (still a couple of orders of magnitude away from High vac):

"For many applications, sorption pumps are the vehicles of choice for creating a good vacuum. They have no moving parts; instead they work by chilling a type of substance, called a sorbent, to a temperature at which it absorbs gases. Activated charcoal works, but a molecular sieve is better. Molecular sieves are little pellets with so many microscopic nooks and crannies that they have fantastically large surface areas; a one-gram pellet may have more than 1,000 square meters of surface.

When chilled, air molecules get caught in these microchasms. A 50-gram supply can pump a one-liter volume down to 10 millitorr in 20 minutes. (Atmospheric pressure is about 760 torr.) Half a gallon of molecular sieve from Duniway Stockroom sells for about $35."

In the chapter "A Homemade Atom Smasher" (pdf) in "The Scientific American Book of Projects for the Amateur Scientists" (libgen), Clair Stong describes a DIY high-vacuum system based on salvaged refrigerator pumps and a home-made mercury (!) diffusion pump that can reach around 2 mPa. It is unclear how much the entire setup cost but Stong implies that it was around $50-100 in 1960, or $400-800 today.

Lastly, Stephen Hansen hosts a lot of information on DIY vacuum systems at belljar.net. Of particular note is a pdf of correspondence he shared with Frank Lee on Homemade Oil Diffusion Pumps. The file includes a basic design Lee reckons could have been machined in 1965 for $10 (~$80 today) that would reach 5x10^-6 torr, or 0.666 mPa.

Oh, and he also hosts a short article that might be of interest to some: "Home Built Mass Spectrometers - the Development of a Simple Quadrupole Gas Analyzer" (Carl Helber. The Bell Jar Vol.6 No.2 Spring 1997)

I'm curious to know if anyone has more elegant solutions for high vacuum systems.

Mac

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