THE PRESSURE LADDER

The Scale

One ruler, fifteen decades — and the mean free path is its unit.

Pressure is the single axis every vacuum problem shares. A dispenser cathode, a neutral-atom trap, a synchrotron and a fusion target look unrelated until you put them on the same ruler — then they are just different decades of the same descent. The unit of that ruler is the mean free path: how far a molecule travels before it hits another one. At one atmosphere that is shorter than a wavelength of light; at the bottom of this ladder it wraps around the Earth.

Rough / primary Rotary vane · scroll · diaphragm

Medium Roots booster · turbo (entry)

High vacuum Turbomolecular · diffusion · cryo

Ultra-high Ion pump · TSP · NEG, after bakeout

Extreme-high Ion + NEG + TSP, fully baked

760Torr λ ≈ 66 nmshorter than a wavelength of light

1Torr λ ≈ 50 µmthe width of a human hair

1e-3Torr λ ≈ 5 cmthe palm of your hand

1e-6Torr λ ≈ 50 ma city block

1e-9Torr λ ≈ 50 kmacross a city

1e-12Torr λ ≈ 50 000 kmaround the Earth, and then some

1e-13Torr

Pacific Fusion 1e-5 frontier Lawrence Livermore Lab / NIF 1e-5 national lab HeatWave Labs 1e-6 industrial eBeam, Inc. 1e-6 industrial CPI / Eimac (heritage) 1e-7 industrial Applied Materials 1e-7 industrial Lam Research 1e-7 industrial

PsiQuantum 1e-8 frontier Atom Computing 1e-10 frontier Rigetti Computing 1e-10 frontier SLAC / LCLS-II 1e-10 national lab Lawrence Berkeley Lab / ALS 1e-10 national lab

Read top to bottom, the map sorts itself. Industry, fusion and the chip fabs cluster in high vacuum (1e-6 to 1e-7). The quantum scale-ups and the accelerators push into ultra-high vacuum — and below 1e-10, where the common gauge starts reporting its own X-rays instead of the pressure, only the accelerators have a reason to live. That floor, and the discipline it demands, is the whole subject of the field notes.

The actors → Regime abacus → The stack →