High Outgassing Rates Research Articles

Marine Phosphate Level During the Archean Constrained by the Global Redox Budget

AbstractUnderstanding the oceanic phosphate concentration is critical for understanding marine productivity and oxygen evolution throughout Earth history. During the Archean, estimates of marine phosphate levels range from scarce to enriched conditions. However, biogeochemical conditions required for sustaining high phosphate concentrations while retaining an anoxic atmosphere during the Archean remain ambiguous. Here, we employ a biogeochemical model of the marine phosphate cycle to determine the conditions under which oceanic phosphate levels could have been higher than present‐day values during the Archean after the emergence of oxygenic photoautotrophs (OP). We show that, under the presence of OP, phosphate‐rich oceans require the limitation by factors other than phosphate, or a high outgassing rate of reducing gases. If these conditions were not met, the occurrence of oceanic phosphate levels higher than present‐day values during the Archean would require the absence of OP.

Investigation of the intrinsic outgassing rates for narrow structured vacuum devices under readsorption effect

The narrow structure within the vacuum system usually results in a slow evacuation process. Additionally, the high outgassing rate caused by the large surface-to-volume ratio can prevent the vacuum level from meeting the performance requirements of the device. In this paper, the evacuation of the stainless steel parallel plates is established based on a two-dimensional equation combined with the outgassing theory of the recombination–dissociation-limited model. The relationship between the measured and intrinsic outgassing rates was investigated by varying the gap size, pump-out port size, and temperature. The results show that the internal pressure is nonuniformly distributed during the pump-down process, even reaching a quasiequilibrium state. This indicates that the widely used throughput method can make a difference in measuring outgassing rates. This provides a theoretical basis for testing intrinsic outgassing rates, calculating pressure distribution, and configuring pumps or getters in complex vacuum systems.

Vacuum chamber conditioning and saturation simulation tool (VacuumCOST): Enabling time-dependent simulations of pressure and NEG sticking in UHV chambers

Modern particle accelerators, synchrotrons, and other machines requiring UHV frequently make use of NEG coatings to achieve low pressures and resulting high beam stability and lifetime. It is the nature of NEG pumps and coatings, that a limited amount of gas can be pumped before saturation is reached, at which point the NEG must be re-activated to pump efficiently again. While the pumping mechanism and absorption limits are well understood and software packages exist for simulating the steady-state vacuum systems, there is a need for simulating the temporal evolution of the pumping capability of NEG coatings in regions of high outgassing rates such as near crotch absorbers. This paper presents a simple framework, written in Python, for running time-dependent simulations of NEG-coated vacuum systems in molecular flow, by making use of the command-line interface of the already widely used MolFlow simulation software. It also compares simulation results with accelerator pressure measurements.

Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

Abstract. We present a statistical survey of large-amplitude, asymmetric plasma and magnetic field enhancements detected outside the diamagnetic cavity at comet 67P/Churyumov–Gerasimenko from December 2014 to June 2016. Based on the concurrent observations of plasma and magnetic field enhancements, we interpret them to be magnetosonic waves. The aim is to provide a general overview of these waves' properties over the mission duration. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of these waves and their characteristics. In total, we identified ∼ 70 000 steepened waves in the magnetic field data by means of machine learning. We observe that the occurrence of these steepened waves is linked to the activity of the comet, where steepened waves are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressional nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual steepened waves. With increasing mass loading, the average amplitude of the waves decreases, while the skewness increases. Using a modified 1D magnetohydrodynamic (MHD) model, we investigated if the waves can be described by the combination of nonlinear and dissipative effects. By combining the model with observations of amplitude, width and skewness, we obtain an estimate of the effective plasma diffusivity in the comet–solar wind interaction region and compare it with suitable reference values as a consistency check. At 67P/Churyumov–Gerasimenko, these steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

Systematic study of the outgassing behavior of different ceramic materials

The outgassing rates of various ceramic materials were systematically investigated. This paper intercompares the most relevant ceramic material classes used in vacuum technology, namely, oxide (five different types investigated) and non-oxide based ceramics, including nitrides (four different types) and carbides (three different types). For this purpose, the Outgassing Measurement Apparatus, which uses the difference method, was applied. Besides time, also, temperature dependence of outgassing was studied to check whether a previous heat treatment of the ceramics is necessary. Additionally, the outgassing species were qualitatively determined by a quadrupole mass spectrometer. In total, relatively large differences were found between the investigated ceramic materials for their initial outgassing rates as well as for their behavior at elevated temperatures. All investigated types of carbide ceramics showed very low outgassing rates of less than 3 × 10−8 Pa m3/(s m2) after 100 h at room temperature, whereas rather high outgassing rates of about 10−5 Pa m3/(s m2) were found for magnesia as well as the tested nitride ceramic types. Thus, depending on the ceramic material, a heat treatment is strongly recommended before use in ultrahigh vacuum applications.

Photochemical Oxygen in Non-1-bar CO2 Atmospheres of Terrestrial Exoplanets

Abstract Atmospheric chemistry models have shown that molecular oxygen can build up in CO2-dominated atmospheres on potentially habitable exoplanets without input of life. Existing models typically assume a surface pressure of 1 bar. Here we present model scenarios of CO2-dominated atmospheres with the surface pressure ranging from 0.1 to 10 bars, while keeping the surface temperature at 288 K. We use a one-dimensional photochemistry model to calculate the abundance of O2 and other key species, for outgassing rates ranging from a Venus-like volcanic activity up to 20 times Earth-like activity. The model maintains the redox balance of the atmosphere and the ocean, and includes the pressure dependency of outgassing on the surface pressure. Our calculations show that the surface pressure is a controlling parameter in the photochemical stability and oxygen buildup of CO2-dominated atmospheres. The mixing ratio of O2 monotonically decreases as the surface pressure increases at very high outgassing rates, whereas it increases as the surface pressure increases at lower-than-Earth outgassing rates. Abiotic O2 can only build up to the detectable level, defined as 10−3 in volume mixing ratio, in 10-bar atmospheres with the Venus-like volcanic activity rate and the reduced outgassing rate of H2 due to the high surface pressure. Our results support the search for biological activities and habitability via atmospheric O2 on terrestrial planets in the habitable zone of Sun-like stars.

Outgassing behavior of different high-temperature resistant polymers

In vacuum applications, polymers often need to be used in spite of their relatively high outgassing rates, e.g., as sealing or spacer material. For some polymers—like Viton®, which is used for O-rings—data on outgassing rates can be found in literature, while for others, in particular, the most relevant ones that can be used at higher temperatures, only few results are available. Therefore, different high-temperature resistant polymers were measured at the Outgassing Measurement Apparatus, which uses the difference method. These polymers were polyimides like Kapton®, Vespel®, and Meldin®, as well as a polyetheretherketone and a polybenzimidazole. In order to investigate the temperature behavior of the outgassing of the polymers, the measurements were performed at room temperature, 100 °C, and 200 °C. The outgassing species were determined by a mass spectrometer. In addition, the dependence of the outgassing on the material thickness was analyzed. The paper shows that the outgassing rates of the examined polymers are higher than 10−4 (Pa m3)/(s m2) after 10 h at room temperature, except for the thin Kapton samples. Thus, further treatment of the materials will be necessary depending on the application. It is shown that a vacuum bake-out at not less than 200 °C is favorable. The main outgassing species is water, as expected, but also different hydrocarbons with higher mass can be seen for the polyimides. Concerning different thicknesses, the outgassing rate of a thin sample generally decreases more steeply than the outgassing rate of the thicker sample. Nevertheless, the steepest decrease was found for the thickest Kapton sample, with a difference of nearly factor 500 between 10 and 100 h at room temperature.

Quantifying melt production and degassing rate at mid‐ocean ridges from global mantle convection models with plate motion history

AbstractThe Earth's surface volcanism exerts first‐order controls on the composition of the atmosphere and the climate. On Earth, the majority of surface volcanism occurs at mid‐ocean ridges. In this study, based on the dependence of melt fraction on temperature, pressure, and composition, we compute melt production and degassing rate at mid‐ocean ridges from three‐dimensional global mantle convection models with plate motion history as the surface velocity boundary condition. By incorporating melting in global mantle convection models, we connect deep mantle convection to surface volcanism, with deep and shallow mantle processes internally consistent. We compare two methods to compute melt production: a tracer method and an Eulerian method. Our results show that melt production at mid‐ocean ridges is mainly controlled by surface plate motion history, and that changes in plate tectonic motion, including plate reorganizations, may lead to significant deviation of melt production from the expected scaling with seafloor production rate. We also find a good correlation between melt production and degassing rate beneath mid‐ocean ridges. The calculated global melt production and CO2 degassing rate at mid‐ocean ridges varies by as much as a factor of 3 over the past 200 Myr. We show that mid‐ocean ridge melt production and degassing rate would be much larger in the Cretaceous, and reached maximum values at ∼150–120 Ma. Our results raise the possibility that warmer climate in the Cretaceous could be due in part to high magmatic productivity and correspondingly high outgassing rates at mid‐ocean ridges during that time.

真空用材料

Vacuum chambers, components and related systems consist of various materials according to requiring material performance. Austenitic stainless steels have been used for vacuum chambers due to high mechanical strength, anti-corrosion and low outgassing. Aluminum alloy have been used for special vacuum systems such as particle accelerator due to non-magnetism and low radioactivation. Copper has been used for flange gasket due to good ductility. Ceramics have been used for components of electrical insulator, high temperature system and so on due to good stability under harsh environments. Organic materials are less used due to their high outgassing rate compared with inorganic materials. It is important to select and put the right material in the right place in a vacuum system.

EXTREME-ULTRAVIOLET AND X-RAY OBSERVATIONS OF COMET LOVEJOY (C/2011 W3) IN THE LOWER CORONA

We present an analysis of EUV and soft X-ray emission detected toward Comet Lovejoy (C/2011 W3) during its post-perihelion traverse of the solar corona on December 16, 2011. Observations were recorded by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory and the X-Ray Telescope (XRT) aboard Hinode. A single set of contemporaneous images is explored in detail, along with prefatory consideration for time evolution using only the 171 A data. For each of the eight passbands, we characterize the emission and derive outgassing rates where applicable. As material sublimates from the nucleus and is immersed in coronal plasma, it rapidly ionizes through charge states seldom seen in this environment. The AIA data show four stages of oxygen ionization (O III - O VI) along with C IV, while XRT likely captured emission from O VII, a line typical of the corona. With a nucleus of at least several hundred meters upon approach to a perihelion that brought the comet to within 0.2 solar radii of the photosphere, Lovejoy was the most significant sungrazer in recent history. Correspondingly high outgassing rates on the order of 10^32.5 oxygen atoms per second are estimated. Assuming that the neutral oxygen comes from water, this translates to a mass-loss rate of about 9.5E9 g/s, and based only on the 171 A observations, we find a total mass loss of approximately 10^13 g over the AIA egress. Additional and supporting analyses include a differential emission measure to characterize the coronal environment, consideration for the opening angle, and a comparison of the emission's leading edge with the expected position of the nucleus.

Wall cleanings for pre-treatment on EAST

Wall cleaning has been used popularly on tokamaks to reduce impurities and fuel recycling. Since 2008, the plasma facing components of EAST have been all of graphite. Due to the special crystal structure of graphite, high outgassing rate and strong absorption of hydrogen gas are induced. The wall cleaning is in particular important for the pre-treatment before the plasma operation of the machine. In this article, we introduce the wall conditioning system on EAST, and study the removal efficiency of device baking and glow discharge cleaning in different working gases and at different operating parameters. The long duration baking and GDC cleaning in EAST notably reduce the wall outgassing, and impurity radiation. After the cleanings, plasma is easily obtained, which is beneficial for the plasma physics experiment.

Vacuum-compatible vibration isolation stack for an interferometric gravitational wave detector TAMA300

Interferometric gravitational wave detectors require a large degree of vibration isolation. For this purpose, a multilayer stack constructed of rubber and metal blocks is suitable, because it provides isolation in all degrees of freedom at once. In TAMA300, a 300 m interferometer in Japan, long-term dimensional stability and compatibility with an ultrahigh vacuum environment of about 10−6 Pa are also required. To keep the interferometer at its operating point despite ground strain and thermal drift of the isolation system, a thermal actuator was introduced. To prevent the high outgassing rate of the rubber from spoiling the vacuum, the rubber blocks were enclosed by gas-tight bellows. Using these techniques, we have successfully developed a three-layer stack which has a vibration isolation ratio of more than 103 at 300 Hz with control of drift and enough vacuum compatibility.

被覆電線およびエラストマー・プラストマー材料等のガス放出速度測定

Some kinds of the electrical cables and elastomer/plastomer materials, though having high outgassing rates, are occasionally used in a high vacuum system. In order to evaluate the ultimate pressure of the system in which those materials are to be installed, their outgassing rates have been measured as a function of pumping time by a through-put method. The outgassing rates of the cables and glass-fiber sleevings ranged from 10-9 to 10-5 Pa·m3. s-1. m-1 at 100 h, depending on the insulation materials or varnishing treatment. From the tests of the elastomer/plastomer materials, it was ascertained that the organic materials give high outgassing rates of the orders of 10-5 to 10-3 Pa·m3·s-1·m-2 at 100 h.

Synthesis And Characterization Of Fluorinated Poly(Arylethers): Organic Polymers For Ic Imd

AbstractAmong the more promising approaches to minimizing capacitance in the multilevel interconnect of integrated circuits containing sub-half micron metal spacings is the development of organic polymers which exhibit high performance in key attributes such as thermal stability, low dielectric constant, and low moisture absorption coupled with high outgassing rates of what little moisture may be present. The use of such polymers as the intermetal dielectric can reduce power consumption and cross talk, while increasing signal propagation speed. While polyimides are the most extensively characterized polymer thin film dielectrics, and are in many cases suitable for the intermetal dielectrics in multichip modules, their tendency to absorb significant quantities of moisture, coupled with relatively slow outgas characteristics (presumably due to hydrogen bonding between water molecules and the carbonyls of the polyimide) constitute significant impediments to throughput in the fabrication of IC interconnects.The search for alternative polymers which incorporate the “good” characteristics of polyimides while exhibiting improvements in electrical, moisture, and processing characteristics led us to the development of nominally 1 μm spin-on films derived from a family of noncarbonyl containing aromatic polyethers. Fluorinated poly(arylethers) based on decafluorobiphenyl exhibit thermal stability comparable to polyimides, from ten to forty times lower moisture absorption, dielectric constants in the mid-two's, and good retention of storage modulus above their glass transition temperatures. The precursor spin-on solutions, formulated in low toxicity organic solvents, exhibit excellent shelf life, and can be prepared with extremely low levels of metallic contamination. This paper describes the synthesis and both solution and film properties of this newly developed class of highly processible thermally stable polymers, first reported by Mercer, et. al. [1]. The characteristics of the polymers when spin-coated on silicon wafers is emphasized. Thermal and thermomechanical properties of nominally 10-25 μm free standing films are also described.

Field ion microscope with photostimulable phosphor screen — new approach for quantitative analysis of FIM images-

Adaptability of a photostimulable phosphor screen, called an imaging plate (IP), for field emission and field ion microscopies was examined. The photostimulated luminescence (PSL) of the IP for He + is strong enough for field ion microscopy, but that for Ne + is less than one tenth of He +, like an ordinary fluorescent material. The digitized computer-processed images of W, W-Re and Pt-Ir are unexpectedly clear. The image brightness seems to increase with the number of incoming ions and the PSL intensity ratio of a dark atom to a bright atom is found to be as large as 1 to 160, suggesting the possibility of a quantitative analysis of electron tunneling and a field ionization probability over individual surface atoms. However, this ratio is significantly smaller than the expected dynamic range of the IP, 10 4, possibly due to the charge up of the IP's surface, low ion energies and an IP's high outgassing rate, which deteriorates vacuum and induces high background counting. Accordingly, darkly imaged “invisible atoms” of the alloys are hardly recognizable at present.

電解研磨法および乾式切削法によるアルミニウム合金製箱形真空容器の真空特性

Two aluminum alloy chambers designed to hold the magnets and electrodes of a pulse beam stretcher were manufactured. The inner surface of one chamber was treated with electropolishing. The inner surface of the other chamber was treated with machining in a dry atmosphere.The electropolished chamber contained hydrate at the surface and showed a high outgassing rate of 1×10-9 Pa·m3/ (s·m2) after a 150°C, 24-hour bakeout. The chamber machined in the dry atmospher contained less hydrate at the surface than the electropolished chamber did and showed a low outgassing rate of 1.5×10-10 Pa·m3/ (s·m2) after a 150°C, 24-hour bakeout.

Outgassing rate of aluminum alloy vacuum chamber for tristan ultra-high vacuum system.

The TRISTAN Electron Positron Colliding Ring consists of a main ring of 30GeV (e-, e+) with a diameter of approx. 1000m, and a subordinate ring of 6-8GeV (e-, e+) with a diameter of approx. 100m for preacceleration and storage. Both rings require a pressure of approx. 10-9 Torr at Beam On and a pressure of approx. 10-10 Torr at Beam Off, respectively.Considering the effect of beam on the vacuum, the chamber is made of aluminum alloy with a high cooling efficiency because the inner walls are exposed to very powerful radiation (3kW/m (approx. 100W/cm2)). Generally, aluminum alloy with a high outgassing rate has been thought of as unsuitable for ultra-high vacuum material. A newly developed aluminum alloy produced by special extrusion, however, shows an outgassing rate in the order of 10-14 Torr l/s·cm2 due to 24-hour baking at 150°C. Also, the residual radioactivity in the aluminum new alloy is noticeably reduced, compared with stainless steel. The above-mentioned facts prove that this alloy is excellent as ultra-high vacuum material.As a result of the experiment using the aluminum alloy in all vacuum parts it is confirmed that, contrary to the conventional view, aluminum alloy is most suitable for ultra-high vacuum material and that the TRISTAN Ring in which the alloy is used can be operated with a satisfactory performance.

3128. Influence of the manufacturing parameters on film structure and properties of reactively sputtered vanadium dioxide films

Due to the ease of moulding light components of any shape, excellent electrical insulation and nonmagnetic properties of epoxy resins, their use in vacuum systems is quite wide spread. However, their relatively high outgassing rates—approximately one hundred times that of unbaked glass or metals and one million times that of baked glass and metals—is a serious drawback and can cause formidable vacuum problems unless this aspect is duly considered in the design. This effect is usually manifested in impracticably high pumping speeds which would be required to attain pressures below 10−5 torr (10−3 Pa), in systems using large surface areas of epoxy. In situations where large epoxy surfaces are unavoidable, some means of reducing the outgassing rate would be desirable. This paper presents the results of many trials in this direction. It was found that outgassing rate can be reduced by an aquadag coating (by a factor of 5), by a vacuum evaporated aluminium coating (by a factor of 10) or by cladding with aluminium or stainless steel foils (by a factor of 20). However, these surface treatments would obviously affect the surface dependent electrical properties of the epoxy.

Outgassing from epoxy resins and methods for its reduction

Due to the ease of moulding light components of any shape, excellent electrical insulation and nonmagnetic properties of epoxy resins, their use in vacuum systems is quite wide spread. However, their relatively high outgassing rates—approximately one hundred times that of unbaked glass or metals and one million times that of baked glass and metals—is a serious drawback and can cause formidable vacuum problems unless this aspect is duly considered in the design. This effect is usually manifested in impracticably high pumping speeds which would be required to attain pressures below 10 −5 torr (10 −3 Pa), in systems using large surface areas of epoxy. In situations where large epoxy surfaces are unavoidable, some means of reducing the outgassing rate would be desirable. This paper presents the results of many trials in this direction. It was found that outgassing rate can be reduced by an aquadag coating (by a factor of 5), by a vacuum evaporated aluminium coating (by a factor of 10) or by cladding with aluminium or stainless steel foils (by a factor of 20). However, these surface treatments would obviously affect the surface dependent electrical properties of the epoxy.

Preliminary EM6 Modifications for in situ Chemical Vapor Deposition

An AEI EM6 electron microscope is being modified for in situ chemical vapor deposition. The objective is to observe the nucleation and growth kinetics and structure of silicon deposited by SiH4 gas pyrolysis on substrates of sapphire (single crystal α-Al2O3).An Edwards DCB2 thermoelectrically cooled baffle has been installed using a simple adapter which permitted attachment without drilling or cutting of the EM6 frame or vacuum system. Prior to installation the measured contamination rate was 240Å/min; afterward the contamination rate was less than 100 Å/min.An auxiliary pumping system is mounted to the left rear of the column and attached by a special stainless steel flexible bellows to the pumping port at the rear of the specimen chamber. The auxiliary system has an ultimate presure <1 × 10-6 torr, but the measured pressure in the specimen chamber was no better than 1 × 10-5 torr, due primarily to the high outgassing rate of the beam deflector coil immediately above the specimen chamber.