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Technical Information
Pump Operation
The diffusion pump works by heating the pump fluid to its boiling point. The vapors
travel upward inside the jet assembly and are accelerated out and downward
through the jet nozzles toward the cool outer walls of the pump, where the vapor
condenses back into a fluid. As the vapor passes the inlet, it picks up elements of
the gas to be exhausted and carries them to the ejector and out of the pump via the
foreline. The pump's ability to reach low pressures is governed in part by the inlet
size. The gas migrates by thermal motion and is captured and expelled, thus
lowering the pressure in the evacuation vessel.
Large diffusion pumps achieve a vacuum using a five-stage jet assembly consisting
of four diffusion stages and one ejector stage. The cold cap and body are water
cooled. Optional stainless steel Quick Cool coils quickly suppress boiling by cooling
the heater; they require an independently valved water supply.
Technical Specifications
The Technical Characteristics of the large diffusion pumps are given in Table 4.
The graphs in Figure 3 through Figure 6 show air speed and throughput as a
function of inlet pressure. The dimensions of the inlet flange that connects to
the system to be evacuated are given in Table 6 through Table 12.
The data in Table 4 refers to pumps charged with DC-704 diffusion pump fluid.
NOTE
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High Throughput Diffusion Pumps User Manual
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