User:Marshallsumter/Radiation astronomy/Distillations

"Intrinsic contaminations of radioisotopes in liquid xenon detectors are a serious background source in rare-event experiments such as searches for dark matter [1,2,3,4] and neutrinoless double beta-decay searches [5]. The two most important internal sources of radioactive backgrounds are 85Kr and 222Rn. While krypton can be removed by cryogenic distillation before the start of a measurement [6,7,8,9], 222Rn is continuously produced inside detector materials due to the decay of trace amounts of 2262Ra. As a noble gas with a half-life of 3.8 days, 222Rn can enter the liquid xenon target by means of diffusion or recoil from prior α-decays. Once in the liquid, 222Rn distributes homogeneously, reaching also the innermost part of the detector. Subsequent beta-decays in the 222Rn decay chain are sources of low energy background [2,3,4]."

The "purification of xenon from traces of the radioactive noble gas radon [uses] a cryogenic distillation column [...] integrated into the gas purification loop of the XENON100 detector for online radon removal [enabling] to significantly reduce the constant 222Rn background originating from radon emanation."

"After achieving the dark matter science goal with XENON100, the gas purification system of the detector was extended with a cryogenic distillation column, operated as a 222Rn removal system. We significantly reduced the 222Rn activity concentration without any xenon losses (off-gas)."

The cryostat and shield of the XENON100 is shown at right. The shield consists of an outer layer of 20 cm of water, a 20 cm layer of lead, a 20 cm layer of polyethylene, and on the interior a 5 cm copper layer.

Distillations
Def. the "separation of the volatile parts of a substance from the more fixed; specifically, the operation of driving off gas or vapor from volatile liquids or solids, by heat in a retort or still, and the condensation of the products as far as possible by a cool receiver, alembic, or condenser; rectification; vaporization; condensation" is called distillation.

Weakly interacting massive particles
Supersymmetric extensions of the Standard Model of particle physics readily predict a new particle in the 100 GeV mass range that interacts via the electroweak force to thermally produce an abundance of dark matter that requires a self-annihilation cross section of $$\langle \sigma v \rangle \simeq 3 \times 10^{-26} \mathrm{cm}^{3} \;\mathrm{s}^{-1},$$. A new particle with these properties, is known as the "WIMP miracle", and a stable supersymmetric partner has long been a prime WIMP candidate.

Recent null results from dark matter direct-detection experiments along with the failure to produce evidence of supersymmetry in the Large Hadron Collider (LHC) experiment has cast doubt on the simplest WIMP hypothesis.

Coal gases
Def. a mixture of gases (chiefly hydrogen, methane, and carbon monoxide) obtained by the destructive distillation of coal, or gas given off when coal is burned, is called coal gas.

Coal tars
Def. a "black, oily, sticky, viscous substance, consisting mainly of hydrocarbons produced by the distillation of [derived from] organic materials such as wood, peat, or coal" is called a tar.

Def. a "black, viscous tar made by the destructive distillation of coal (to make coke and town gas)" is called a coal tar.

It contains at least benzene, naphthalene, phenols, and aniline.

Crude oil distillations
The crude oil distillation unit (CDU), the first processing unit in virtually all petroleum refineries, distills the incoming crude oil into various fractions of different boiling ranges, each of which is then processed further in the other refinery processing units, and is often referred to as the atmospheric distillation unit because it operates at slightly above atmospheric pressure.

Greenland ice sheet petrogony
"In the figure at the right the Atlantic [United Nations’ International Atomic Energy Agency] IAEA stations are divided into groups of ocean, coast and continental stations. Further grouping in a tropical-subtropical (red), a temperate (green) and a polar (violet) category shows linear relationships between annual δ versus temperature within each category, which suggests (1) the influence of re-evaporated fresh water from the continents, and (2) the existence of at least two more or less separate distillation columns in the Atlantic Ocean, a tropical-subtropical and a temperate one, perhaps even a polar one. This is an effect of the air taking up new vapour during its travel toward higher latitudes, i.e. a precipitation pattern more complicated than that considered in [the first diagram at the right]."

Moon
"Distillation has been suggested as a process which produced refractory material from less refractory precursors in the pre-solar or early solar nebula. Some coarse-grained Allende inclusions, ie. C1 and EK 1-4-1, had large fractionations of the magnesium (1) and silicon (2,3) isotopes which might have been produced by distillation. The surfaces of lunar soil grains were enriched in heavy isotopes of silicon and oxygen by a mechanism that may have combined particle-induced impact melting, volatilization and escape of lighter isotopes from the lunar surface, and condensation of the heavier isotopes onto lunar soil grain surfaces (4,5)."

"Distillation and sputtering of magnesium have produced fractionations of Mg isotopes that fit a Rayleigh process model and sputtering also gave "negative" fractionation, enrichment of the light isotopes (6,7)."

The "trend in silicon isotopic fractionation during distillation is to enrich the heavier isotopes in the residue (8) and that isotopic anomalies [non-linear effects] are not produced by distillation."

Hot rocky exoplanets
"Data suggest that most rocky exoplanets with orbital period p < 100 d ("hot" rocky exoplanets) formed as gas-rich sub-Neptunes that subsequently lost most of their envelopes".

There is "a pathway by which 1–1.7 R⊕ (1–10 M⊕) rocky exoplanets with orbital periods of 10–100 days can acquire long-lived 10–2000 bar atmospheres that are H2O-dominated, with mean molecular weight >10. These atmospheres form during the planets' evolution from sub-Neptunes into rocky exoplanets. H2O that is made by reduction of iron oxides in the silicate magma is highly soluble in the magma, forming a dissolved reservoir that is protected from loss so long as the H2-dominated atmosphere persists. The large size of the dissolved reservoir buffers the H2O atmosphere against loss after the H2 has dispersed."

A "long-lived, water-dominated atmosphere is a common outcome for efficient interaction between a nebula-derived atmosphere (peak atmosphere mass fraction 0.1–0.6 wt%) and oxidized magma (>5 wt% FeO), followed by atmospheric loss."

Most "rocky planets that have orbital periods of 10–100 days and that have radii within 0.1–0.2 R⊕ of the lower edge of the radius valley still retain H2O atmospheres."

Atmospheric "escape distills the products of chemical reactions between silicate magma and nebula-derived H2 to yield hot rocky exoplanets with 10-2000 bar, long-lived H2O atmospheres."

Magma-atmosphere "equilibrium in the Fe-Mg-Si-O-H system [neglects] Fe3+ and He, and [assumes] that volatiles equilibrate with magma at T ∼ 2500 K. H2 from the nebula is oxidized by magmatic Fe2+O to form H2O (this has previously been proposed as a way to form oceans on habitable-zone planets, e.g. Sasaki 1990; Ikoma & Genda 2006). The key reaction is FeO(l) + H2(g) = Fe(l) + H2O(g)."

Detectors
The PMTs on the top array shown on the right are placed in concentric circles to improve the reconstruction of the radial position of observed events.

As WIMP interactions are expected to be extremely rare events, a thorough campaign was launched during the construction and commissioning phase of XENON100 to screen all parts of the detector for radioactivity using high-purity Germanium detectors and in a few cases performing mass spectrometry on low mass plastic samples to achieve the design goal of <10−2 events/kg/day/keV.

The detector was installed at the Laboratori Nazionali del Gran Sasso (Gran Sasso National Laboratory) in 2008 in the same shield as the XENON10 detector, where each science run failed to observe a dark matter signal above the expected background, leading to the most stringent limit on the spin independent WIMP-nucleon cross section in 2012, with a minimum at $2 cm2$ for a $65 GeV/c2$ WIMP mass. These results constrain interpretations of signals in other experiments as dark matter interactions, and rule out exotic models such as inelastic dark matter, which would resolve this discrepancy. XENON100 has also provided improved limits on the spin dependent WIMP-nucleon cross section. An axion result was published in 2014, setting a new best axion limit.

XENON100 operated the then-lowest background experiment, for dark matter searches, with a background of 50 mDRU (1 mDRU=10−3 events/kg/day/keV).