work in progress....
different pumps for different pressures:
Pumps come in many different shapes, sizes, and types.
When we want to get to really low pressures (which is most of the time here at LCLS) we use layered tiers of pumping: where we turn on one type, wait until the pressure stops dropping, then turn on the next, and again when the pressure stops dropping again we turn on a third type.
An example pumping sequence goes like this:
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