The prototype pump of this design was intended for use as a visual display for
teaching undergraduate students in Physical Chemistry at Arizona State University.
The original work order for this design was to build a glass diffusion pump similar to
the metal diffusion pump used in the teaching lab so that students could better
observe how an oil vapor diffusion pump operates. A 4" metal diffusion pump was
disassembled and critical dimensions were taken and scaled to accommodate
standard glass tubing sizes. Construction of the first pump involved several trials
(and errors) in determining the most effective method of building the jet assembly for
the pump. After completing the pump, it was attached to a mechanical forepump,
cold traps, a manifold and vacuum gauges. It made a successful debut in the
teaching lab, providing a visual display of the inner workings of an oil diffusion
pump. It is considered our most effective teaching aide in high vacuum principles
and techniques.

Further testing of the pump revealed that the pump was functional and the pumping
speed far exceeds that of traditional glass oil diffusion pumps. After making several
refinements to the pump, I began systematically replacing the old style glass oil and
mercury diffusion pumps and currently have 30 vacuum pumping stations of this
design in daily operation at Arizona State University. All research groups using these
pumping stations report that they produce lower ultimate vacuum and faster pumping
speeds than other glass diffusion pump designs. (The traditional glass diffusion
pumps have advertised pumping speeds of 7 to 30 liters per second. The 4" pump
operates at 375 liters per second. Quite an improvement in performance!)

Arizona State University was very generous in allowing the release of this pump
design to the chemical research industry. Construction details for this pump design
were presented at the American Scientific Glassblowers Society symposium in
Seattle, WA, in June 1995. The "Proceedings of the A.S.G.S. 1995 Sumposium",
"4" Glass Oil Diffusion Pump", by Michael D. Wheeler, pages 24-30, carries the full