BUILD 04 · PUMP
What pumping speed actually reaches the chamber?
A pump is sold by its speed at its own flange. What the chamber sees is that speed in series with every tube, elbow, bellows and valve between them. This step computes the difference.
What already answers this
Nothing below is a copy. Each line is the surface of this site that carries the answer, and what it carries.
- /tools/regime-abacus/ names the pump families that work at the target pressure
- /stack/pumps/ holds what each pump family does and where it stops
- /academy/vent-physics/ carries the flow regimes the conductance formulas depend on
The system, laid piece by piece
Drag to turn
Branch by branch
| Branch | Line | Conductance | At flange | At chamber | Delivered | Wall | In the total |
|---|
Every wall the gas sees counts, from the chamber inclusive to the pumps exclusive. A chamber longer than 3 diameters is treated as a tube and carries a parabolic pressure profile, a compact one stays a single node. That threshold is this page's convention, not a published result.
What these figures rest on
The chamber is the node. A branch starts at its pump: put a pump on a port, then lay its line back toward the chamber, section by section, until it reaches. Click the dashed section to lay a piece, press Enter, lay the next. Drag the drawing to turn it. Proportions are representative, only the typed dimensions are computed, and the molecular regime is the only one these formulas hold in.
P. Chiggiato, Vacuum Technology for Ion Sources, CERN, Geneva, arXiv:1404.0960. Read here: Eq. 20 C = C′ A₁ τ ; Eq. 21 the Santeler equation for the transmission probability of a uniform circular tube, stated to better than 0.7 per cent ; Eq. 22 its long tube limit ; Eq. 23 C ≈ 12.3 D³/L for N₂ ; Table 8 unit area conductances at 293 K. F-CHIGGIATO-IONSOURCES
E. Al-Dmour, Fundamentals of Vacuum Physics and Technology, Proceedings of the 2017 CERN Accelerator School course on Vacuum for Particle Accelerators, Glumslov, arXiv:2006.01464. Read here: Eq. 47 C = 3.64 A √(T/M) for a thick orifice ; Eq. 48 C = 11.6 A for air at 23 C ; Eq. 49 C = 3.81 (d³/L) √(T/M) for a long circular tube ; Eq. 50 C = 12.1 d³/L for air at 23 C ; Eq. 51 1/S_eff = 1/C + 1/S_nom. F-ALDMOUR-CAS2017
Outgassing rates are read from the outgassing base by material and surface state, and the key of each reading travels with the result into the dossier.
Not in the base yet
The elbow, the bellows and the gate valve are shop rules. No document opened for this page publishes a formula for them: they are drawn dashed, counted as unsourced in the table, and no correction factor was invented to close the gap.
What already answers this
Not in the base yet
What this step cannot answer, and why. Every count below is read from the corpus at build, so this block shrinks on its own the day the data grows.
- unsourced No pump is in the data. The conductance chain on this page computes what a pumping speed becomes behind a line, and the pumping speed itself has to be typed in from the pump datasheet.
- unsourced The bellows conductance has no source in the corpus. A bellows is computed here as a straight tube of the same bore and length, which UNDERSTATES its resistance, and the field says so on its face.
- unsourced The elbow correction of 1.3 diameters per bend is a shop rule, carried in formulas.ts under the flag COUDE_ILLUSTRATIF. No source in this corpus publishes it.