Engraved frontispiece for The Scale: a vertical pressure ladder rendered as a vintage plate.
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

The inhabited ladder

Step back from the Bay-Area actors above and put generic categories of machine on the same axis, alongside the natural pressure environments we never built. Twenty decades of vacuum, and nature still wins by four.

Pressure ladder — machines vs nature A vertical log-pressure axis (Torr) from 10³ at atmosphere down to 10⁻¹⁷ at the interstellar medium. The machines we build (left column) and the natural pressure environments (right column) sit side by side on the same ruler. What we build What nature provides 103 Torr 10−1 10−5 10−9 10−13 10−17 Vacuum cleaner · 600 Vacuum cleaner · 600 Bench desiccator · 5 Bench desiccator · 5 Freeze dryer · 10⁻¹ to 10⁻³ Freeze dryer Semiconductor fab · 10⁻⁴ to 10⁻⁸ Semiconductor fab Electron tube · 10⁻⁶ to 10⁻⁷ Electron tube Electron microscope · 10⁻⁶ to 10⁻⁹ Electron microscope SRF cryomodule · 10⁻⁹ to 10⁻¹⁰ SRF cryomodule LHC beam pipe · 10⁻¹⁰ to 10⁻¹¹ LHC beam pipe XHV record · 10⁻¹² to 10⁻¹³ XHV record Sea level · 760 Sea level · 760 Everest summit · 250 Everest summit · 250 Kármán line · 10⁻⁴ Kármán line · 10−4 ISS orbit · 10⁻⁸ ISS orbit · 10−8 Lunar surface · 10⁻¹¹ Lunar surface · 10−11 Interstellar medium · 10⁻¹⁷ Interstellar medium · 10−17 Twenty decades of vacuum — and nature still wins by four.

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 →