Vacuum Pumps

6 03 2009

Let’s explore the world of vacuum pumps! 

Starting with units.

The pascal (symbol: Pa) is the SI derived unit of pressure.

The torr (symbol: torr[1]) is a non-SI unit of pressure defined as 1/760 of an Atmosphere. 1 torr = 133,322 pascal.

1 mbar  = 0.1 kPa

psi  = 6.894757 kPa.

Cubic feet per minute (CFPM or CFM) is a non-SI unit of measurement of the flow of a gas or liquid that indicates how much volume in cubic feet pass by a stationary point in one minute. The lower the CFPM the better the suction. 1 cfm = 4.71945×10-4 m3 s-1


Our target vacuum quality is 10^-9 torr, or 1.33322368 × 10-7 pascals.


Lets look at the different types of pumps:


Now lets take a look at what’s available on ebay:

rotary vane pump here is the spec sheet. possible rough pump.

varian diffusion pump

turbomolecular pump

cryo-trap to prevent back flow from diffusion pump.


I think the idea setup would be chamber -> cryo-trap -> oil diffusion pump -> rough pump.



One response

7 03 2009
M. Simon

As I said in a previous post: for this kind of work stay away from diffusion pumps.

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