Physics — Phase: helium-4 (superfluid)

title "Helium-4 phase diagram"
// Pressures are in bar, which is what this engine captions them with.
// They were 5050 and 227 — the first in pascals, the second in
// kilopascals — so the figure asserted a 5,050 bar lambda point and a
// 227 bar critical point, both off by orders of magnitude against a
// caption that reads "bar".
//
// The lower point is the LAMBDA point (He I / He II), 2.17 K and
// 0.0505 bar. Helium-4 has no ordinary triple point: it does not
// solidify at any pressure below about 25 bar. `triple` is the only
// keyword this notation has for marking a point, so it is used here and
// the caption reads "Triple" — a limitation of the notation, recorded
// rather than papered over.
type pt
triple 2.17 0.0505
critical 5.20 2.27
region "Solid He" at (0.25, 0.88) color slate
region "He I (normal liquid)" at (0.6, 0.5) color teal
region "He II (superfluid)" at (0.3, 0.4) color blue
region "Gas" at (0.78, 0.15) color amber