Helium-3 - Wikiparency

# Helium-3 Helium-3 is the light, non-radioactive isotope of [[Helium]] with two protons and one neutron — a candidate aneutronic fusion fuel and cryogenic superfluid, anchoring the energy-frontier branch of the Thury spine. That one missing [[Neutron|neutron]] flips the atom's statistics from Bose to Fermi, and every other property on this page descends from it. ## Microsims — three.js <iframe src="https://wikitube-3d-microsims.netlify.app/Helium-3.html" width="100%" height="620" frameborder="0" loading="lazy" sandbox="allow-scripts allow-same-origin" title="Helium-3 — three.js microsim"></iframe> **`Helium-3` (three.js).** The sim holds two ensembles side by side in momentum space — helium-4 on the left, helium-3 on the right — and cools them together under a single logarithmic temperature slider running from 10 K down to 1 mK. Drag it downward and watch the asymmetry appear: the bosons collapse into a bright bead at k = 0, while the fermions can only fill a sphere out to the Fermi wavevector k_F and merely sharpen its edge, which is Pauli exclusion made visible. Occupations are sampled from real Bose–Einstein and Fermi–Dirac distributions with the chemical potential solved by bisection at every step so that particle number is conserved, and the result is checked rather than asserted: the condensate fraction reproduces 1 − (T/T_c)^{3/2} to about one part in 10⁹, and μ/E_F tracks the Sommerfeld expansion to about one part in 10⁸, without the code ever being told either answer. The HUD prints both transition temperatures with their pressures stated — 2.1768 K for helium-4 at saturated vapour pressure, and helium-3's 2.49 mK on the melting curve against 0.93 mK at zero pressure — which is precisely the distinction the rest of this article is about.  ## Microsims — p5.js ### Helium-3 (p5.js) <div class="microsim-player"> <iframe src="https://editor.p5js.org/sciencenibber/full/clpT03_2G" width="100%" height="480" frameborder="0" loading="lazy" sandbox="allow-scripts allow-same-origin" title="Helium-3 — p5.js microsim"></iframe> </div> *The rare light isotope: two protons and a single neutron, prized for dilution refrigeration and neutron detection where ordinary helium-4 cannot serve.* **Open in the editor:** [▶ fork this sketch](https://editor.p5js.org/sciencenibber/sketches/clpT03_2G) · library `p5js` ### Related microsims Live sims on neighbouring articles — 2 of them inside this article's own Wikipedia link tree: - [[Helium]] *(in tree)* - [[Helium-4]] *(in tree)* *Sim hosted off-article; the article owns the reference, not the runtime (WIKI_RULES §10.4). Placed by `g08_place_microsims.py`.*  ## Reveal %%REVEAL:three%% --- *Concept aligned with [Wikipedia](https://en.wikipedia.org/wiki/Helium-3); adapted text, where present, is licensed [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0/).* ## Overview The rule that makes the missing [[Neutron|neutron]] decisive is [[Spin_(physics)|spin]]-statistics, not an empirical measurement: **a composite particle is a [[Boson|boson]] if it contains an even total number of [[Fermion|fermions]], a fermion if that number is odd.** Count them. Helium-4: two [[Proton|protons]], two neutrons, two [[Electron|electrons]] — six fermions, even — a boson atom whose nucleus has spin I = 0 (Jπ = 0⁺, [[Binding_energy|binding energy]] 28.296 MeV). Helium-3: two protons, one neutron, two electrons — five fermions, odd — a **fermion** atom whose nucleus, three fermions, has I = ½ (Jπ = ½⁺). Three fermions in the nucleus, five in the atom: two isotopes of one [[Noble_gas|noble gas]], chemically indistinguishable, obeying opposite [[Quantum_mechanics|quantum]] statistics. Everything below descends from that. A fermion cannot pile into a single state, so ³He cannot go [[Superfluidity|superfluid]] as [[Superfluid_helium-4|helium-4]] does at the lambda point; it must pair first, at roughly a thousandth the temperature, which places the subject inside [[Cryogenics|cryogenic]] [[Helium_cryogenics|helium engineering]]. A spin-½ nucleus has a magnetic moment, so ³He serves precision magnetometry, [[Nuclear_magnetic_resonance|nuclear magnetic resonance]] and [[Hyperpolarization_(physics)|hyperpolarized]]-gas [[Magnetic_resonance_imaging|MRI]]. ³He and tritium are mirror nuclei 764 keV apart in mass, so a slow neutron converts ³He to a [[Proton|proton]] and a triton with enormous probability — the whole of ³He [[Neutron_detection|neutron detection]]. And D + ³He releases 18.353 MeV wholly into charged particles, making it the canonical [[Aneutronic_fusion|aneutronic]] [[Nuclear_fusion|fusion]] fuel. One nucleon, four industries. Two things reference works blur. ³He is **stable**: its scarcity owes nothing to [[Radioactive_decay|radioactivity]]. And the helion — the bare nucleus — masses 3.014 932 246 932(74) u against the neutral atom's [[Atomic_mass|atomic mass]] of about 3.016 029 3 u. ## Where the atoms come from Two routes, wildly unequal. A little ³He is primordial — made in [[Nucleosynthesis|Big Bang nucleosynthesis]], still resupplied from the [[Sun|Sun]] by the solar wind, which implants it in lunar [[Regolith|regolith]], puts the [[Moon|Moon]] on every supply map beside terrestrial [[Natural_gas|natural gas]], and has [[Nuclear_fusion|fusion]] planners pointing at [[Jupiter|Jupiter]] and the gas giants. Nearly all ³He anyone has used comes by the other route: tritium [[Beta_decay|beta-decays]] to ³He with a [[Half-life|half-life]] of **12.32 ± 0.02 y** (~5.5% per year), and the [[Decay_product|daughter]] is collected when weapons reservoirs are serviced. In air it is a trace of a trace: CIAAW puts ³He at a mole fraction of 0.000002(2) of atmospheric [[Helium|helium]], and helium is ~5.24 ppmv of air, so ³He is around 7 parts per trillion of the atmosphere by volume. **The atmospheric ratio is actively disputed and must not be printed as settled.** Clarke et al. (1976) give Rₐ = **1.384 ± 0.006 ×10⁻⁶**; Mamyrin et al. (1970) give **1.399 ± 0.013 ×10⁻⁶**; Mishima et al. (2018), calibrating against a synthesised HESJ standard gas, propose **1.340 ± 0.006 ×10⁻⁶** — a 3–4% discrepancy the authors could not explain. Rₐ is the denominator of nearly every ³He/⁴He [[Accuracy_and_precision|measurement]] in geochemistry, so the shift propagates everywhere. Quote the range; name the ends. The isotope also separates the [[Earth|Earth]]'s interior from its shell. Mantle helium is comparatively ³He-rich, a primordial signature never fully outgassed; [[Crust_(geology)|crustal]] helium — what collects in gas fields, is won by [[Fractional_distillation|fractional distillation]], and feeds the [[Helium_production_in_the_United_States|US helium industry]] and the [[National_Helium_Reserve|National Helium Reserve]] — is overwhelmingly radiogenic ⁴He from [[Alpha_decay|alpha decay]] of [[Uranium|uranium]] and thorium, running a few hundredths of Rₐ. The much-quoted 70–242 ppb of ³He in natural-gas helium traces only to secondary citations: an order of magnitude, not a measurement. Either way, mantle flux is "not even a few kilograms per year," and no terrestrial reservoir is worth working for ³He alone. ## Why it is scarce: a governance failure, not a geological one Essentially all commercial ³He is harvested from [[Radioactive_decay|decaying]] tritium in nuclear-weapons reservoirs — in the US from NNSA operations at Savannah River, historically topped up by Russian supply of ~25,000 L/y in 2004–2008. There is no significant terrestrial primary source, [[Crust_(geology)|crustal]] or [[Natural_gas|natural-gas]]: the supply is a by-product of an arsenal, on the arsenal's schedule — a [[Cold_War|Cold-War]] inheritance inside a civilian market. Demand broke that after 11 September 2001, when over 1,400 [[Neutron|neutron]]-sensitive radiation portal [[Sensor|monitors]] went out at US borders to catch smuggled [[Uranium|uranium]] and [[Plutonium|plutonium]]; GAO records demand as having "nearly tripled." The shortage surfaced in **June 2008**, when the Spallation Neutron Source — a [[Neutron_diffraction|neutron-scattering]] facility — requested 35,000 L against an inventory that could not supply it; it went public in Congressional testimony in November 2009. GAO's finding is the part usually dropped, and it is the point. **The failure was governance, not geology:** GAO-11-472 (12 May 2011) reports that **"no DOE entity had stewardship responsibility"** for [[Helium|helium]]-3. [[Helium_production_in_the_United_States|Extraction capacity]] was **8,000–10,000 L/y** against average sales near **30,000 L/y** in 2003–2009. Of ~260,000 L available in 2003, 209,888 L went out by 2009; NNSA held ~31,000 L by February 2011. CRS records prices moving from $40–85/L at auction to $365–1,000/L allocated in 2009–2011 and $2,000/L commercially. [[Helium_storage_and_conservation|Inventory management]], not scarcity of matter. The 2026 position is better and still tight. DOE credits [[Helium_storage_and_conservation|recycling]] and alternative [[Neutron_detection|detectors]] — [[Boron|boron]]-lined and ¹⁰BF₃ counters, [[Lithium|lithium]]-6 glass — and projects **federal demand below 6,000 L/y** against the 70,000 L/y peak of 2008. Laurentis Energy Partners (Ontario Power Generation) announced on 16 September 2021 that it was extracting ³He from tritium stored at the Darlington [[Nuclear_engineering|CANDU]] station: the **first civilian, non-military source**, quantities undisclosed. Russian supply has been effectively excluded from Western markets since 2022. The fastest-growing demand is no longer detection but [[Quantum_computing|quantum computing]], whose [[Dilution_refrigerator|dilution refrigerators]] each need a ³He charge to reach the [[Cryogenics|millikelvin]] stage where [[Superconductivity|superconducting]] qubits run. On 16 September 2025 Bluefors contracted with Interlune for up to **10,000 L/y of [[Lunar_resources|lunar]] ³He, 2028–2037** (100,000 L total): a commitment against a resource nobody has yet [[In_situ_resource_utilization|extracted]]. Treat the circulating market figures with care — 22,000–30,000 L/y of production against 40,000–60,000 L/y of demand, $1,900–2,600/L, ~40 L per large fridge — as secondary compilations, marked `[UNVERIFIED]` here. One error they correctly flag: a [[Dilution_refrigerator|dilution refrigerator]]'s ³He circulates in a **sealed loop indefinitely**, so its charge is one-time inventory, not annual consumption. ## Four uses, four numbers Each has its own article and sim. Here is the number that matters and the caveat that travels with it. ### Dilution refrigeration The [[Dilution_refrigerator|dilution refrigerator]] works because ³He stays soluble in [[Liquid_helium|liquid]] [[Helium-4|⁴He]] down to absolute zero — about **6.6% at saturated vapour pressure** (sources quote 6.4–6.6%, so print no third decimal). Below the tricritical point, **0.8669 ± 0.0005 K at x₃ = 0.6716 ± 0.0014**, the mixture undergoes a [[Phase_transition|phase separation]], and driving ³He across the boundary absorbs heat — an [[Entropy|entropy]]-of-mixing effect — because its [[Thermodynamics|enthalpy]] is higher in the dilute phase. Both enthalpies scale as T², so cooling power is **Q̇ = 84 ṅ₃T_mc²** — ṅ₃ in mol/s, T in kelvin, Q̇ in watts — or ṅ₃(95T_mc² − 11T_ex²) more precisely. A power law rather than an exponential is why the method survives where [[Boiling_point|evaporative]] cooling dies. **Caveat:** Oxford Instruments' guide prints that coefficient in mW·K⁻²·(mol/s)⁻¹, a factor of 10³ from the textbook form. [[Cryogenics|Cryogen]]-free machines — now the workhorse of [[Quantum_computing|quantum-computing]] cryostats — reach ~10 mK routinely, 5–7 mK commonly, below 5 mK continuous at best (25 µW at 20 mK); **~2 mK is the practical floor**. ### Neutron detection n + ³He → p + T is exoergic by **763.8 keV**, sharing out for a thermal [[Neutron|neutron]] as a **572.6 keV [[Proton|proton]] and a 191.3 keV triton** — an unambiguous [[Signal-to-noise_ratio|signature]] in a proportional counter, and why ³He tubes dominated [[Neutron_detection|neutron detection]] and [[Neutron_diffraction|neutron-scattering]] instruments. The cross-section has two defensible values: **5333 ± 7 b** at 2200 m/s (0.0253 eV) in the Sears/NIST evaluated table, **5316 b** at the same energy in Carlson's international standards — cite the standards value for [[Accuracy_and_precision|metrology]]. It tracks 1/v from 0.0253 eV to 50 keV, exactly the interval over which ³He(n,p)T is a designated standard. **Caveat:** the virtue is the vice — a [[Sensor|detector]] gas this good at absorbing neutrons is why 1,400 portal monitors could drain a national stockpile, and why [[Boron|boron]] and [[Lithium|lithium]] alternatives came back. ### Hyperpolarized gas MRI At 310 K in a 1.5 T [[Superconducting_magnet|magnet]] the thermal nuclear polarization of ³He is **3.77×10⁻⁶** — far too little to image. Optical pumping breaks that ceiling: [[Spin_(physics)|spin]]-exchange pumping reaches **up to 85%**, metastability-exchange 55–85%, an enhancement near **1.3×10⁵** (clinical production historically 30–50%). The shielded helion gyromagnetic ratio is 32.434 100 033(28) MHz/T — 48.65 MHz at 1.5 T. Polarization survives ~100 h in a good storage cell and about **20 s** in a breathing lung, because oxygen dominates relaxation so completely that alveolar oxygen tension is *measured* from it: p_AO₂ = ξ/T1, ξ = 2.61 bar·s at 37 °C. **Caveat:** this is now largely history. [[Xenon|Xenon]]-129 displaced ³He on cost — ~£500/L against ~£150/L for enriched ¹²⁹Xe — and XENOVIEW, approved 23 December 2022, is the first and only FDA-approved [[Hyperpolarization_(physics)|hyperpolarized]] [[Magnetic_resonance_imaging|MRI]] agent. **There is no approved ³He agent.** ³He keeps real advantages in [[Nuclear_magnetic_resonance|gyromagnetic ratio]], polarization and gas-phase [[Diffusion|diffusivity]], and survives in research [[Medicine|medicine]] and neutron spin filters. ### D–³He fusion D + ³He → p + ⁴He releases **18.353 MeV**, more than D–T's 17.589 MeV, and releases it entirely as charged [[Ion|particles]]: a **14.64 MeV [[Proton|proton]] and a 3.71 MeV [[Alpha_particle|alpha]]**, computed relativistically at zero centre-of-mass [[Energy|energy]]. The familiar "14.68 and 3.67 MeV" is the naive mass-number split, wrong in the third digit. Charged products invite direct [[Energy_transformation|conversion]] to electricity and do not activate structure — the attraction for [[Nuclear_engineering|reactor designers]], [[Nuclear_fuel|fuel-cycle]] analysts and [[Fusion_rocket|fusion-rocket]] concepts. **Caveat, and it is large: the reaction is not aneutronic in practice.** Deuterium — the heavy isotope of [[Hydrogen|hydrogen]] — fuses with itself, half the time yielding 2.45 MeV [[Neutron|neutrons]], and bred tritium burns too unless removed. The neutron share of fusion power runs **~1% to ~20%**: about 5–6% for a stoichiometric 50:50 [[Plasma_(physics)|plasma]] at a reactor-relevant 60–100 keV with tritium burning, ~1% only with prompt tritium extraction, ~2% for deuterium-lean fuel, above 20% at 20 keV. Any figure without its fuel ratio, temperature and tritium assumption is meaningless. Reactivity is the second caveat: at 10 keV ⟨σv⟩ is 2.126×10⁻²⁵ m³/s for D–³He against 1.136×10⁻²² m³/s for D–T, and the D–³He curve still climbs at 190 keV (2.68×10⁻²² m³/s), the top of Bosch–Hale validity — so no D–³He "peak temperature" can honestly be cited from that fit. ## The lunar arithmetic [[Sun|Solar]]-wind [[Ion|ions]] implant a few tens of nanometres into [[Regolith|regolith]] grains and are held preferentially in ilmenite, whose [[Crystal_structure|crystal structure]] makes the high-titanium [[Moon|lunar]] maria the target; abundances span roughly **1.4–20 ppb by mass** (Apollo 11 soil 10084: 9.22–17.9 ppb, mean 11.8), and heating to 700–800 °C recovers most of it. Global inventories span **0.66 Mt** (Fa & Jin 2010, from Chang'E-1 radiometry), **~1 Mt** (the Wisconsin figure) and **2.47 Mt** (Slyuta 2007) — all *resources in place*. The one published *reserve*, Cameron 1992 at 50% minability in Mare Tranquillitatis, is **7,041 t**: three orders of magnitude below the headline. A tonne [[Nuclear_fusion|fully burned]] gives 5.87×10¹⁷ J = 163 TWh thermal, so "25 tonnes would supply the entire United States' [[Energy|energy]] needs for a year" (Schmitt, 2000) is off by about **7×** — 13.9 quads thermal against 94–96 quads of primary consumption. It works only for *electricity*, and only at the 70–80% direct [[Energy_transformation|conversion]] Schmitt assumed in 1988, never demonstrated at reactor scale. [[Lunar_resources|Lunar resources]] and [[In_situ_resource_utilization|in-situ resource utilization]] are serious subjects; this number is not evidence for them. ## The quantum-fluid story, corrected [[Superfluid_helium-4|Helium-4]] goes [[Superfluidity|superfluid]] at the lambda point, **T_λ = 2.1768 K at 5041.8 Pa** on the saturated-vapour line; the ubiquitous "2.17 K" and "2.172 K" are truncations of that ITS-90 value. It gets there free, because the atom is a [[Boson|boson]] — [[Zero-point_energy|zero-point motion]] having kept both isotopes [[Liquid_helium|liquid]] to absolute zero in the first place. Helium-3 cannot. Its atoms are [[Fermion|fermions]], so macroscopic occupation of one [[Quantum_mechanics|quantum]] state is open only to **pairs**; and because the hard core of the interatomic potential forbids the s-wave singlet pairing of ordinary [[Superconductivity|superconductors]], the pairs form [[Spin_(physics)|spin]]-triplet and p-wave, S = 1 and L = 1. Anderson and Morel gave the anisotropic state in 1961 (predicting a transition "below 0.02 K," an order of magnitude too warm), Balian and Werthamer the isotropic-gap state in 1963, and Anderson and Brinkman in 1973 the spin-fluctuation feedback that stabilises the first; "ABM" conflates two papers twelve years apart, so cite both. The order parameter is a 3×3 matrix, not one complex number, which is why the [[Phase_transition|transition]] yields a family of phases. Four things are commonly got wrong here, and correcting them is the most useful work this page does. **The first paper was about the solid.** Osheroff, Richardson and Lee, *Phys. Rev. Lett.* **28**, 885 (3 April 1972), is titled **"Evidence for a New Phase of Solid He³"** — two anomalies in the pressurisation of ³He along the melting curve under Pomeranchuk cooling, which works because [[Crystal_structure|solid]] ³He holds more nuclear-[[Spin_(physics)|spin]] [[Entropy|entropy]] than the [[Liquid_helium|liquid]], attributed to the solid. The liquid identification came in the **second** paper, PRL **29**, 920, on [[Nuclear_magnetic_resonance|NMR]] evidence; Leggett's PRL **29**, 1227 argued the phases were an anisotropic [[Superfluidity|superfluid]]. The 1996 Nobel Prize in [[Physics|Physics]] went to Lee, Osheroff and Richardson "for their discovery of superfluidity in helium-3"; Leggett shared the 2003 prize with Abrikosov and Ginzburg. (Leggett died on 8 March 2026.) **2.491 mK is not "the" transition temperature.** It is the A transition **at melting pressure, 34.338 bar, on the Greywall 1986 scale**; on PLTS-2000, the official [[Cryogenics|low-temperature]] scale, the same point is **2.444 mK at 3.43407 MPa**. English Wikipedia prints 2.491 mK with no pressure at all, which is how the error travels. **At zero pressure it is about a third of that** — Tc = **0.929 mK (Greywall), 0.908 mK (PLTS-2000)**. One trap: Greywall's solid Néel transition at melting pressure is 0.931 mK, numerically almost identical to the zero-pressure Tc and physically unrelated. The two get swapped constantly. **There is no A phase at zero pressure.** In zero field the A phase exists only above the polycritical point, **21.22 bar and 2.273 mK**; at saturated vapour pressure the [[Phase_transition|transition]] runs normal → **B** directly. And do not quote the discovery-era "2.7 mK and 2.1 mK": those sit on a pre-1986 [[Accuracy_and_precision|temperature scale]], and Greywall noted that his 2.49 mK "differs quite substantially from the currently accepted value of about 2.7 mK." Reaching the millikelvin at all takes the other isotope: the [[Dilution_refrigerator|dilution refrigerator]] cools by diluting ³He into [[Helium-4|⁴He]], so the [[Fermion|fermion]]'s superfluid is reached through the [[Boson|boson]]'s, kelvin by hard-won kelvin. Nowhere here are the two interchangeable — and the odd nucleon is the reason. ## Sources Primary literature actually relied on. Items marked `[UNVERIFIED]` could not be confirmed against a primary source and should not be repeated without checking. - **Osheroff, Richardson & Lee (1972),** "Evidence for a New Phase of Solid He³," *Phys. Rev. Lett.* **28**, 885. [10.1103/PhysRevLett.28.885](https://doi.org/10.1103/PhysRevLett.28.885) — the discovery paper, and the title that proves the initial attribution was to the solid. - **Osheroff, Gully, Richardson & Lee (1972),** "New Magnetic Phenomena in Liquid He³ below 3 mK," *Phys. Rev. Lett.* **29**, 920. [10.1103/PhysRevLett.29.920](https://doi.org/10.1103/PhysRevLett.29.920) — the NMR evidence locating the transitions in the liquid. - **Leggett (1972),** "Interpretation of Recent Results on He³ below 3 mK: A New Liquid Phase?" *Phys. Rev. Lett.* **29**, 1227. [10.1103/PhysRevLett.29.1227](https://doi.org/10.1103/PhysRevLett.29.1227); and **Leggett (1975),** *Rev. Mod. Phys.* **47**, 331, [10.1103/RevModPhys.47.331](https://doi.org/10.1103/RevModPhys.47.331) — the identification of the phases as p-wave spin-triplet superfluids, and the standard review. - **Anderson & Morel (1961),** *Phys. Rev.* **123**, 1911, [10.1103/PhysRev.123.1911](https://doi.org/10.1103/PhysRev.123.1911); **Balian & Werthamer (1963),** *Phys. Rev.* **131**, 1553, [10.1103/PhysRev.131.1553](https://doi.org/10.1103/PhysRev.131.1553); **Anderson & Brinkman (1973),** *Phys. Rev. Lett.* **30**, 1108, [10.1103/PhysRevLett.30.1108](https://doi.org/10.1103/PhysRevLett.30.1108) — the A and B order-parameter states and the spin-fluctuation stabilisation behind the "ABM" label. - **Greywall (1986),** "³He specific heat and thermometry at millikelvin temperatures," *Phys. Rev. B* **33**, 7520. [10.1103/PhysRevB.33.7520](https://doi.org/10.1103/PhysRevB.33.7520) — the Greywall scale: Tc = 2.491 mK at melting pressure, 0.929 mK at zero pressure. - **Tian, Smith & Parpia (2022),** "Conversion Between ³He Melting Curve Scales Below 100 mK," *J. Low Temp. Phys.* **208**, 298. [10.1007/s10909-022-02721-z](https://doi.org/10.1007/s10909-022-02721-z) — the source for both the zero-pressure values and the Greywall ↔ PLTS-2000 conversion. See also the [PTB description of PLTS-2000](https://www.ptb.de/cms/en/ptb/fachabteilungen/abt7/fb-74/ag-744/the-provisional-low-temperature-scale-of-2000-plts-2000.html) for the melting-curve fixed points; the polycritical point at 21.22 bar / 2.273 mK is from *Nat. Commun.* **13**, 7871 (2022), [10.1038/s41467-022-35532-7](https://doi.org/10.1038/s41467-022-35532-7). - **Vollhardt & Wölfle (1990),** *The Superfluid Phases of Helium 3*, Taylor & Francis. [10.1201/b12808](https://doi.org/10.1201/b12808) — the standard monograph. - **BIPM (2018),** *Guide to the Realization of the ITS-90 — Vapour-Pressure Scales* — the lambda point as 2.1768 K at 5041.8 Pa. [PDF](https://www.bipm.org/documents/20126/41773843/Guide_ITS-90_3_VPS_p_2018.pdf/dcd65f47-8699-d2f2-cace-44885f4f49fb) - **London, Clarke & Mendoza (1962),** "Osmotic Pressure of He³ in Liquid He⁴, with Proposals for a Refrigerator to Work below 1 °K," *Phys. Rev.* **128**, 1992. [10.1103/PhysRev.128.1992](https://doi.org/10.1103/PhysRev.128.1992) — the dilution-refrigerator proposal, following London's 1951 Oxford conference note; first working machine Das, de Bruyn Ouboter & Taconis (Leiden, built 1964, published 1965, 0.22 K), [10.1007/978-1-4899-6443-4_133](https://doi.org/10.1007/978-1-4899-6443-4_133). - **Kierstead (1979),** *J. Low Temp. Phys.* **35**, 25. [10.1007/BF00121720](https://doi.org/10.1007/BF00121720) — the tricritical point, 0.8669 ± 0.0005 K at x₃ = 0.6716 ± 0.0014. - **Pobell (2007),** *Matter and Methods at Low Temperatures*, 3rd ed., Springer. [10.1007/978-3-540-46360-3](https://doi.org/10.1007/978-3-540-46360-3) — the cooling-power expressions and the ~2 mK practical floor. Note the unit-convention conflict with Oxford Instruments' *Principles of Dilution Refrigeration*: `[UNVERIFIED]` which of W and mW is intended in the vendor guide. - **Carlson (2011),** "The neutron cross section standards, evaluations and applications," *Metrologia* **48**, S328. [10.1088/0026-1394/48/6/S09](https://doi.org/10.1088/0026-1394/48/6/S09) — ³He(n,p)T as an international standard over 0.0253 eV–50 keV, σ = 5316 b; compare the [NIST NCNR table](https://www.ncnr.nist.gov/resources/activation/scattering_table.html) value of 5333 ± 7 b. - **Bosch & Hale (1992),** "Improved formulas for fusion cross-sections and thermal reactivities," *Nucl. Fusion* **32**, 611. [10.1088/0029-5515/32/4/I07](https://doi.org/10.1088/0029-5515/32/4/I07) — the reactivity parameterisation, valid to 190 keV for ³He(d,p)⁴He with ~10% underlying uncertainty. Q values cross-checked against Ongena, *EPJ Web Conf.* **268**, 00011 (2022), [10.1051/epjconf/202226800011](https://doi.org/10.1051/epjconf/202226800011); product energies computed relativistically from [CODATA-2022 masses](https://physics.nist.gov/cuu/Constants/Table/allascii.txt). - **Gentile, Nacher, Saam & Walker (2017),** "Optically polarized ³He," *Rev. Mod. Phys.* **89**, 045004. [10.1103/RevModPhys.89.045004](https://doi.org/10.1103/RevModPhys.89.045004) — the authoritative source for SEOP/MEOP polarizations and cell relaxation times. - **Stewart et al. (2022),** *Br. J. Radiol.* **95**, 20210207. [10.1259/bjr.20210207](https://doi.org/10.1259/bjr.20210207) — documents the ³He → ¹²⁹Xe transition and its economics; **Taskiran et al. (2022),** *Tomography* **8**, 2268, [10.3390/tomography8050190](https://doi.org/10.3390/tomography8050190) — p_AO₂ = ξ/T1 with ξ = 2.61 bar·s; **MacLeod et al. (2025),** *Diagnostics* **15**, 474, [10.3390/diagnostics15040474](https://doi.org/10.3390/diagnostics15040474) — confirms clinical status through 2025. - **GAO-11-472 (12 May 2011),** *Managing Critical Isotopes: Weaknesses in DOE's Management of Helium-3 Delayed the Federal Response to a Critical Supply Shortage*. [gao.gov/products/gao-11-472](https://www.gao.gov/products/gao-11-472) — the stewardship finding and the production/sales/inventory figures. - **CRS R41419 (2010, rev. 2011),** *The Helium-3 Shortage: Supply, Demand, and Options for Congress*. [congress.gov PDF](https://www.congress.gov/crs_external_products/R/PDF/R41419/R41419.8.pdf) — stockpile trajectory and price history. Current allocation and the sub-6,000 L/y federal demand projection: [DOE NIDC](https://www.isotopes.gov/Supply-and-Demand-of-Helium-3). - **Mishima et al. (2018),** *Geochem. Geophys. Geosyst.* **19**, 3399. [10.1029/2018GC007554](https://doi.org/10.1029/2018GC007554) — the proposed revision of the atmospheric ³He/⁴He ratio and the unexplained 3–4% discrepancy with Clarke (1976) and Mamyrin (1970). Isotopic composition from [CIAAW](https://www.ciaaw.org/helium.htm). - **Fa & Jin (2010),** *Chin. Sci. Bull.* **55**, 4005, [10.1007/s11434-010-4198-9](https://doi.org/10.1007/s11434-010-4198-9); **Slyuta, Abdrakhimov & Galimov (2007),** LPSC XXXVIII [abs. 2175](https://www.lpi.usra.edu/meetings/lpsc2007/pdf/2175.pdf); **Cameron (1992),** *Helium Resources of Mare Tranquillitatis*, [WCSAR-TR-AR3-9207-1](https://fti.neep.wisc.edu/fti.neep.wisc.edu/pdf/wcsar9207-1.pdf); **Olson (2021),** AIAA ASCEND, [NTRS 20210022801](https://ntrs.nasa.gov/api/citations/20210022801/downloads/AIAA%20ASCEND%202021%20Paper_211018.pdf) — the low, high and reserve-grade lunar estimates and the Apollo sample data. **Schmitt (1988),** [NTRS 19890005478](https://ntrs.nasa.gov/api/citations/19890005478/downloads/19890005478.pdf) states the 70–80% direct-conversion assumption underlying every "X tonnes powers Y" claim. - **De Temmerman, Chuard & Rudelle (2021),** "The helium bubble: prospects for ³He-fuelled nuclear fusion," *Joule* **5**, 1312. [10.1016/j.joule.2021.05.001](https://doi.org/10.1016/j.joule.2021.05.001) — the sceptical counterweight and the mantle-flux figure. Cite its conclusions, not its statement of regolith concentration in µg/g, which is a units slip of three orders of magnitude. - `[UNVERIFIED]` — 2025–26 world production and price figures (22,000–30,000 L/y; $1,900–2,600/L; ~40 L per large dilution refrigerator); ³He content of natural-gas helium (70–242 ppb); "1.4–15 ppb in sunlit areas" and the ~50 ppb polar figure, which rests on Schmitt's cold-trapping hypothesis rather than measurement.  *Built to the [[WT!P5_js_Microsim_Master_Class|p5.js Master Class]].*   *Linked from the [[WT!Thury_Hydrodynamics_Compendium|Thury Hydrodynamics Compendium]], section 14, Helium-3 and fusion.*  ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Helium-3) : [Wikitube](https://en.wikitube.io/wiki/Helium-3) ## Previous hub tags Hubs: `Life_Physics`. Portals: [[PORTAL_Thury_Hydrodynamics_Apex_Spine]], [[PORTAL_Helium-3]].