Commission, step 7 of 8

How long until it reaches the number I specified?

The pumpdown curve is the first measurement of the assembled chamber. This step compares the predicted curve against the specification set in step one.

read read from the base typed entered by hand, outside the base

The machine you laid

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Reading the machine you laid.

What already answers this

Each line links a page of this site and says what it carries for this step.

/tools/outgassing/#calculate runs the pumpdown from the sourced gas load, and names the key it read
/academy/surface-science/ carries the desorption that makes the tail of the curve
/scale/ places the reached pressure back on the ruler the specification used

Pumpdown for this machine

The machine you laid at step four carries its walls, their material and their state, and the speed the network delivers at the chamber. The outgassing base carries what those walls give off at the times somebody measured them. The curve combines these two inputs only.

Curve and admission detail

typed The target this machine has to meet. Entered by hand, outside the base, and carried in the address with the machine.

Target pressure, Torr By, hours of pumping

At one hour, ten hours and a hundred hours
Pumping time	Pressure	Gas load	What dominates

Commission assumptions

What these figures rest on

Surfaces are counted by one rule: Every wall the gas sees counts, from the chamber inclusive to the pumps exclusive.

The pressure formula is F-CHIGGIATO-IONSOURCES, P. Chiggiato, Vacuum Technology for Ion Sources, CERN, Geneva, arXiv:1404.0960.

Open dossier

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Not in the base yet

What this step cannot answer, and why. Every count below is read from the corpus at each build.

unsourced The pumpdown model reads 258 entries of sourced outgassing and no pump curve at all. A pump that loses speed near its base pressure is not modelled, so a predicted time near the ultimate is optimistic and the calculator says so.
unsourced No commissioning record from a real machine is carried. Nothing here is validated against a chamber that was actually pumped down.

Your machines

kept in this browser, never sent anywhere