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Sample records for gaseous helium pressurant

  1. Pressure-Volume-Temperature (PVT) Gauging of an Isothermal Cryogenic Propellant Tank Pressurized with Gaseous Helium

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2014-01-01

    Results are presented for pressure-volume-temperature (PVT) gauging of a liquid oxygen/liquid nitrogen tank pressurized with gaseous helium that was supplied by a high-pressure cryogenic tank simulating a cold helium supply bottle on a spacecraft. The fluid inside the test tank was kept isothermal by frequent operation of a liquid circulation pump and spray system, and the propellant tank was suspended from load cells to obtain a high-accuracy reference standard for the gauging measurements. Liquid quantity gauging errors of less than 2 percent of the tank volume were obtained when quasi-steady-state conditions existed in the propellant and helium supply tanks. Accurate gauging required careful attention to, and corrections for, second-order effects of helium solubility in the liquid propellant plus differences in the propellant/helium composition and temperature in the various plumbing lines attached to the tanks. On the basis of results from a helium solubility test, a model was developed to predict the amount of helium dissolved in the liquid as a function of cumulative pump operation time. Use of this model allowed correction of the basic PVT gauging calculations and attainment of the reported gauging accuracy. This helium solubility model is system specific, but it may be adaptable to other hardware systems.

  2. Modelling and Experimental Verification of Pressure Wave Following Gaseous Helium Storage Tank Rupture

    NASA Astrophysics Data System (ADS)

    Chorowski, M.; Grabowski, M.; Jędrusyna, A.; Wach, J.

    Helium inventory in high energy accelerators, tokamaks and free electron lasers may exceed tens of tons. The gaseous helium is stored in steel tanks under a pressure of about 20 bar and at environment temperature. Accidental rupture of any of the tanks filled with the gaseous helium will create a rapid energy release in form of physical blast. An estimation of pressure wave distribution following the tank rupture and potential consequences to the adjacent research infrastructure and buildings is a very important task, critical in the safety aspect of the whole cryogenic system. According to the present regulations the TNT equivalent approach is to be applied to evaluate the pressure wave following a potential gas storage tank rupture. A special test stand was designed and built in order to verify experimentally the blast effects in controlled conditions. In order to obtain such a shock wave a pressurized plastic tank was used. The tank was ruptured and the resulting pressure wave was recorded using a spatially-distributed array of pressure sensors connected to a high-speed data acquisition device. The results of the experiments and the comparison with theoretical values obtained from thermodynamic model of the blast are presented. A good agreement between the simulated and measured data was obtained. Recommendations regarding the applicability of thermodynamic model of physical blast versus TNT approach, to estimate consequences of gas storage tank rupture are formulated. The laboratory scale experimental results have been scaled to ITER pressurized helium storage tanks.

  3. Thermodynamic Vent System Performance Testing with Subcooled Liquid Methane and Gaseous Helium Pressurant

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S. L.; Tucker, S. P.

    2007-01-01

    Due to its high specific impulse and favorable thermal properties for storage, liquid methane (LCH4) is being considered as a candidate propellant for exploration architectures. In order to gain an -understanding of any unique considerations involving micro-gravity pressure control with LCH4, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the performance of a spray-bar thermodynamic vent system (TVS) with subcooled LCH4 and gaseous helium (GHe) pressurant. Thirteen days of testing were performed in November 2006, with total tank heat leak conditions of about 715 W and 420 W at a fill level of approximately 90%. The TVS system was used to subcool the LCH4 to a liquid saturation pressure of approximately 55.2 kPa before the tank was pressurized with GHe to a total pressure of 165.5 kPa. A total of 23 TVS cycles were completed. The TVS successfully controlled the ullage pressure within a prescribed control band but did not maintain a stable liquid saturation pressure. This was likely. due to a TVS design not optimized for this particular propellant and test conditions, and possibly due to a large artificially induced heat input directly into the liquid. The capability to reduce liquid saturation pressure as well as maintain it within a prescribed control band, demonstrated that the TVS could be used to seek and maintain a desired liquid inlet temperature for an engine (at a cost of propellant lost through the TVS vent). One special test was conducted at the conclusion of the planned test activities. Reduction of the tank ullage pressure by opening the Joule-Thomson valve (JT) without operating the pump was attempted. The JT remained open for over 9300 seconds, resulting in an ullage pressure reduction of 30 kPa. The special test demonstrated the feasibility of using the JT valve for limited ullage pressure reduction in the event of a pump failure.

  4. Liquid Hydrogen Propellant Tank Sub-Surface Pressurization with Gaseous Helium

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Cartagena, W.

    2015-01-01

    A series of tests were conducted to evaluate the performance of a propellant tank pressurization system with the pressurant diffuser intentionally submerged beneath the surface of the liquid. Propellant tanks and pressurization systems are typically designed with the diffuser positioned to apply pressurant gas directly into the tank ullage space when the liquid propellant is settled. Space vehicles, and potentially propellant depots, may need to conduct tank pressurization operations in micro-gravity environments where the exact location of the liquid relative to the diffuser is not well understood. If the diffuser is positioned to supply pressurant gas directly to the tank ullage space when the propellant is settled, then it may become partially or completely submerged when the liquid becomes unsettled in a microgravity environment. In such case, the pressurization system performance will be adversely affected requiring additional pressurant mass and longer pressurization times. This series of tests compares and evaluates pressurization system performance using the conventional method of supplying pressurant gas directly to the propellant tank ullage, and then supplying pressurant gas beneath the liquid surface. The pressurization tests were conducted on the Engineering Development Unit (EDU) located at Test Stand 300 at NASA Marshall Space Flight Center (MSFC). EDU is a ground based Cryogenic Fluid Management (CFM) test article supported by Glenn Research Center (GRC) and MSFC. A 150 ft3 propellant tank was filled with liquid hydrogen (LH2). The pressurization system used regulated ambient helium (GHe) as a pressurant, a variable position valve to maintain flow rate, and two identical independent pressurant diffusers. The ullage diffuser was located in the forward end of the tank and was completely exposed to the tank ullage. The submerged diffuser was located in the aft end of the tank and was completely submerged when the tank liquid level was 10% or greater

  5. Analyzing the Use of Gaseous Helium as a Pressurant with Cryogenic Propellants with Thermodynamic Venting System Modelling and Test Data

    NASA Astrophysics Data System (ADS)

    Hedayat, A.; Nelson, S. L.; Hastings, L. J.; Flachbart, R. H.; Vermilion, D. J.; Tucker, S. P.

    2008-03-01

    Cryogens are viable candidate propellants for NASA's Lunar and Mars exploration programs. To provide adequate mass flow to the system's engines and/or prevent feed system cavitation, gaseous helium (GHe) is frequently considered as a pressurant. A Thermodynamic Venting System (TVS) is designed to maintain tank pressure during low gravity operations without propellant resettling. Tests were conducted in the Marshall Space Flight Center (MSFC) Multi-purpose Hydrogen Test Bed (MHTB) to evaluate the effects of GHe pressurant on pressure control performance of a TVS with liquid hydrogen (LH2) and nitrogen (LN2) test liquids. The TVS used comprises a recirculation pump, a Joule-Thomson (J-T) expansion valve, and a parallel flow concentric tube heat exchanger combined with a longitudinal spray bar. A small amount of liquid extracted from the tank recirculation line was passed through the J-T valve and then through the heat exchanger, extracting thermal energy from the bulk liquid and ullage and thereby enabling pressure control. The LH2/GHe tests were performed at fill levels of 90%, 50%, and 25%, and LN2/GHe tests were conducted at fill levels of 50% and 25%. Moreover, each test was conducted with a specified tank ullage pressure control band. A one-dimensional TVS performance program was used to analyze and correlate the test data. Predictions were compared with test data of ullage pressure and temperature and bulk liquid saturation pressure and temperature.

  6. Analyzing the Use of Gaseous Helium as a Pressurant with Cryogenic Propellants with Thermodynamic Venting System Modelling and Test Data

    NASA Technical Reports Server (NTRS)

    Hedayat, A.; Nelson, S.L.; Hastings, L.J.; Flachbart, R.H.; Vermillion, D.J.; Tucker, S.P.

    2007-01-01

    Cryogens are viable candidate propellants for NASA's Lunar and Mars exploration programs. To provide adequate mass flow to the system's engines and/or to prevent feed system cavitation, gaseous helium (GHe) is frequently considered as a pressurant. During low gravity operations, a Thermodynamic Venting System (TVS) is designed to maintain tank pressure during low gravity operations without propellant resettling. Therefore, a series of tests were conducted in the Multi-purpose Hydrogen Test Bed (MHTB) of Marshall Space Flight Center (MSFC) in order to evaluate the effects of GHe pressurant on pressure control performance of a TVS with liquid hydrogen (LH2) and nitrogen (LN2) as the test liquids. The TVS used in these test series consists of a recirculation pump, Joule-Thomson (J-T) expansion valve, and a parallel flow concentric tube heat exchanger combined with a longitudinal spray bar. Using a small amount of liquid extracted from the tank recirculation line, passing it through the J-T valve, and then through the heat exchanger, thermal energy is extracted from the bulk liquid and ullage thereby enabling pressure control. The LH2/GHe tests were performed at fill levels of 90%, 50%, and 25% and LN2/GHe tests were conducted at fill levels of 50% and 25%. Moreover, each test was conducted with a specified tank ullage pressure control band. A one-dimensional TVS performance program was used to analyze and correlate the test data. Predictions and comparisons with test data of ullage pressure and temperature and bulk liquid saturation pressure and temperature with test data are presented.

  7. Characterization of gaseous helium jet dispersion to atmosphere

    NASA Astrophysics Data System (ADS)

    Khan, H. J.; Figueroa, O.; Rhee, M.

    A major ground-based experiment to be performed for the Superfluid Helium On Orbit Transfer (SHOOT) program is the accidental loss of the vacuum guard of the super-insulated dewar. The design of the dewar vent-path requires adequate mass removal after a preset pressure is reached due to external heat transfer. The existing helium creates a turbulent buoyant jet, expanding in air with entrainment of the jet interface to the surrounding. Transient analysis is performed for axial and radial jet temperature prediction using the self-similarity assumption applied to mass, momentum, and the energy-balance equations of helium. The predicted jet temperature profiles with vertical and radial expansion up to 1.6 and 1.0 m, respectively, demonstrate the low temperature core established by gaseous helium. For all time steps, the axial and radial temperature predictions are observed to be within 8 and 20 percent, respectively.

  8. Validity of the Ruff-MKW boiling point method: Vapor pressures, diffusion coefficients in argon and helium, and viscosity coefficients for gaseous cadmium and zinc

    NASA Astrophysics Data System (ADS)

    Wahlbeck, P. G.; Myers, D. L.; Truong, V. V.

    1985-09-01

    The Ruff-MKW boiling point method is used to determine equilibrium vapor pressures greater than 660 Pa (5 Torr). Samples are vaporized from a Ruff cell, which has a capillary exit, in the presence of an inert gas. Viscosity coefficients and gaseous interdiffusion coefficients may be determined also. This is a second study of the method using Cd(l) and Zn(l) as samples. For the first study with CsCl(l), see J. Chem. Phys. 81, 915 (1984). Vapor pressure data are in good agreement with previous data and gave a third-law ΔsubH0(298) for Cd(s) of 111.95±0.42 kJ/mol and for Zn(s) of 130.65±0.48 kJ/mol. Analyses of the diffusion coefficients gave atomic diameters of 4.06×10-10 m for Cd and 3.46×10-10 m for Zn; these values are somewhat larger than previously measured values. In these experiments when the equilibrium vapor pressures were greater than 13 000 Pa (100 Torr), the need to consider heat transfer from the furnace to the vaporizing sample was noted, i.e., sample cooling occured due to rapid vaporization. Validity of the MKW analysis was found.

  9. Purge Monitoring Technology for Gaseous Helium (GHe) Conservation

    NASA Technical Reports Server (NTRS)

    Dickey, Jonathan; Lansaw, John

    2010-01-01

    John C. Stennis Space Center provides rocket engine propulsion testing for the NASA space programs. Since the development of the Space Shuttle, every Space Shuttle Main Engine (SSME) has gone through acceptance testing before going to Kennedy Space Center for integration into the Space Shuttle. The SSME is a large cryogenic rocket engine that used Liquid Oxygen (LO2) and Liquid Hydrogen (LH2) as propellants. Due to the extremely cold cryogenic conditions of this environment, an inert gas, helium, is used as a purge for the engine and propellant lines since it can be used without freezing in the cryogenic environment. As NASA moves forward with the development of the new ARES V launch system, the main engines as well as the upper stage engine will use cryogenic propellants and will require gaseous helium during the development testing of each of these engines. The main engine for the ARES V will be similar in size to the SSME.

  10. Liquid Oxygen Thermodynamic Vent System Testing with Helium Pressurization

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.

    2014-01-01

    This report presents the results of several thermodynamic vent system (TVS) tests with liquid oxygen plus a test with liquid nitrogen. In all tests, the liquid was heated above its normal boiling point to 111 K for oxygen and 100 K for nitrogen. The elevated temperature was representative of tank conditions for a candidate lunar lander ascent stage. An initial test series was conducted with saturated oxygen liquid and vapor at 0.6 MPa. The initial series was followed by tests where the test tank was pressurized with gaseous helium to 1.4 to 1.6 MPa. For these tests, the helium mole fraction in the ullage was quite high, about 0.57 to 0.62. TVS behavior is different when helium is present than when helium is absent. The tank pressure becomes the sum of the vapor pressure and the partial pressure of helium. Therefore, tank pressure depends not only on temperature, as is the case for a pure liquid-vapor system, but also on helium density (i.e., the mass of helium divided by the ullage volume). Thus, properly controlling TVS operation is more challenging with helium pressurization than without helium pressurization. When helium was present, the liquid temperature would rise with each successive TVS cycle if tank pressure was kept within a constant control band. Alternatively, if the liquid temperature was maintained within a constant TVS control band, the tank pressure would drop with each TVS cycle. The final test series, which was conducted with liquid nitrogen pressurized with helium, demonstrated simultaneous pressure and temperature control during TVS operation. The simultaneous control was achieved by systematic injection of additional helium during each TVS cycle. Adding helium maintained the helium partial pressure as the liquid volume decreased because of TVS operation. The TVS demonstrations with liquid oxygen pressurized with helium were conducted with three different fluid-mixer configurations-a submerged axial jet mixer, a pair of spray hoops in the tank

  11. Primary helium heater for propellant pressurization systems

    NASA Technical Reports Server (NTRS)

    Reichmuth, D. M.; Nguyen, T. V.; Pieper, J. L.

    1991-01-01

    The primary helium heater is a unique design that provides direct heating of pressurant gas for large pressure fed propulsion systems. It has been conceptually designed to supply a heated (800-1000 R) pressurization gas to both a liquid oxygen and an RP-1 propellant tank. This pressurization gas is generated within the heater by mixing super critical helium (40-300 R and 3000-1600 psi) with an appropriate amount of combustion products from a 4:1 throttling stoichiometric LO2/LH2 combustor. This simple, low cost and reliable mixer utilizes the large quantity of helium to provide stoichiometric combustor cooling, extend the throttling limits and enhance the combustion stability margin. Preliminary combustion, thermal, and CFD analyses confirm that this low-pressure-drop direct helium heater can provide the constant-temperature pressurant suitable for tank pressurization of both fuel and oxidizer tanks of large pressure fed vehicles.

  12. Carburization of austenitic alloys by gaseous impurities in helium

    SciTech Connect

    Lai, G.Y.; Johnson, W.R.

    1980-03-01

    The carburization behavior of Alloy 800H, Inconel Alloy 617 and Hastelloy Alloy X in helium containing various amounts of H/sub 2/, CO, CH/sub 4/, H/sub 2/O and CO/sub 2/ was studied. Corrosion tests were conducted in a temperature range from 649 to 1000/sup 0/C (1200 to 1832/sup 0/F) for exposure time up to 10,000 h. Four different helium environments, identified as A, B, C, and D, were investigated. Concentrations of gaseous impurities were 1500 ..mu..atm H/sub 2/, 450 ..mu..atm CO, 50 ..mu..atm CH/sub 4/ and 50 ..mu..atm H/sub 2/O for Environment A; 200 ..mu..atm H/sub 2/, 100 ..mu..atm CO, 20 ..mu..atm CH/sub 4/, 50 ..mu..atm H/sub 2/O and 5 ..mu..atm CO/sub 2/ for Environment B; 500 ..mu..atm H/sub 2/, 50 ..mu..atm CO, 50 ..mu..atm CH/sub 4/ and < 0.5 ..mu..atm H/sub 2/O for Environment C; and 500 ..mu..atm H/sub 2/, 50 ..mu..atm CO, 50 ..mu..atm CH/sub 4/ and 1.5 ..mu..atm H/sub 2/O for Environment D. Environments A and B were characteristic of high-oxygen potential, while C and D were characteristic of low-oxygen potential. The results showed that the carburization kinetics in low-oxygen potential environments (C and D) were significantly higher, approximately an order of magnitude higher at high temperatures, than those in high-oxygen potential environments (A and B) for all three alloys. Thermodynamic analyses indicated no significant differences in the thermodynamic carburization potential between low- and high-oxygen potential environments. It is thus believed that the enhanced carburization kinetics observed in the low-oxygen potential environments were related to kinetic effects. A qualitatively mechanistic model was proposed to explain the enhanced kinetics. The present results further suggest that controlling the oxygen potential of the service environment can be an effective means of reducing carburization of alloys.

  13. 2. SOUTHEAST SIDE. HIGH PRESSURE HELIUM STORAGE TANKS AT LEFT. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. SOUTHEAST SIDE. HIGH PRESSURE HELIUM STORAGE TANKS AT LEFT. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Helium Compression Plant, Test Area 1-115, intersection of Altair & Saturn Boulevards, Boron, Kern County, CA

  14. Molecular dynamics study of helium bubble pressure in tungsten

    NASA Astrophysics Data System (ADS)

    Cui, Jiechao; Li, Min; Wang, Jun; Hou, Qing

    2015-06-01

    Molecular dynamics simulations were performed to calculate the stress field in a tungsten matrix containing a nano-scale helium bubble. A helium bubble in tungsten is found to consist of a core and an interface of finite thickness of approximately 0.6 nm. The core contains only helium atoms that are uniformly distributed. The interface is composed of both helium and tungsten atoms. In the periphery region of the helium bubble, the stress filed is found to follow the stress formula based on the elasticity theory of solid. The pressure difference between both sides of the interface can be well described by the Young-Laplace equation for the core size of a helium bubble as small as 0.48 nm. A comparison was performed between the pressure in the helium bubble core and the pressure in pure helium. For a core size larger than 0.3 nm, the pressure in the core of a helium bubble is in good agreement with the pressure in pure helium of the same helium density. These results provide guidance to larger scale simulation methods, such as in kinetic Monte Carlo methods and rate theory.

  15. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... pressure and 70 degrees Fahrenheit temperature) of gaseous helium or 7510 liters of liquid helium delivered... provide to the Contracting Officer the following data within 10 days after the Contractor or...

  16. High-Pressure Gaseous Burner (HPGB) Facility Became Operational

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2003-01-01

    A gas-fueled high-pressure combustion facility with optical access, developed over the last 3 years, is now collecting research data in a production mode. The High-Pressure Gaseous Burner (HPGB) rig at the NASA Glenn Research Center can operate at sustained pressures up to 60 atm with a variety of gaseous fuels and liquid jet fuel. The facility is unique because it is the only continuous-flow, hydrogen-capable 60-atm rig in the world with optical access. It will provide researchers with new insights into flame conditions that simulate the environment inside the ultra-high-pressure-ratio combustion chambers of tomorrow s advanced aircraft engines. The facility provides optical access to the flame zone through four fused-silica optical windows, enabling the calibration of nonintrusive optical diagnostics to measure chemical species and temperature. The data from the HPGB rig enable the validation of numerical codes that simulate gas turbine combustors.

  17. SIGN, a WIMP detector based on high pressure gaseous neon

    NASA Astrophysics Data System (ADS)

    White, J. T.; Gao, J.; Maxin, J.; Miller, J.; Salinas, G.; Wang, H.

    A new WIMP detector concept based on the measurement of Scintillation and Ionization in Gaseous Neon (SIGN) is presented. The detector employs room temperature gaseous neon at a pressure of ≥100 bars as the WIMP target. The ionization is readout using either charge gain or electrofluorescence or both in a modified cylindrical proportional chamber geometry. The primary scintillation is detected by placing a CsI photocathode on the inside wall of the cylindrical chamber. The neon is doped with xenon (≤0.5%) for signal enhancement. Theoretical considerations suggest that the measurement of both scintillation and ionization will provide discrimination between nuclear and electron recoils in this gas mixture.

  18. Proof-of-principle demonstration of a virtual flow meter-based transducer for gaseous helium monitoring in particle accelerator cryogenics

    SciTech Connect

    Arpaia, P.; Blanco, E.; Inglese, V.; Pezzetti, M.; Serio, L.; Girone, M.; Piccinelli, F.

    2015-07-15

    A transducer based on a virtual flow meter is proposed for monitoring helium distribution and consumption in cryogenic systems for particle accelerators. The virtual flow meter allows technical and economical constraints, preventing installation of physical instruments in all the needed measurement points, to be overcome. Virtual flow meter performance for the alternative models of Samson [ http://www.samson.de (2015)] and Sereg-Schlumberger [ http://www.slb.com/ (2015)] is compared with the standard IEC 60534-2-1 [Industrial-process control valves—Part 2-1: Flow capacity—sizing equations for fluid flow under installed conditions (2011), https://webstore.iec.ch/publication/2461], for a large temperature range, for both gaseous and liquid helium phases, and for different pressure drops. Then, the calibration function of the transducer is derived. Finally, the experimental validation for the helium gaseous state on the test station for superconducting magnets in the laboratory SM18 [Pirotte et al., AIP Conf. Proc. 1573, 187 (2014)] at CERN is reported.

  19. Proof-of-principle demonstration of a virtual flow meter-based transducer for gaseous helium monitoring in particle accelerator cryogenics

    NASA Astrophysics Data System (ADS)

    Arpaia, P.; Blanco, E.; Girone, M.; Inglese, V.; Pezzetti, M.; Piccinelli, F.; Serio, L.

    2015-07-01

    A transducer based on a virtual flow meter is proposed for monitoring helium distribution and consumption in cryogenic systems for particle accelerators. The virtual flow meter allows technical and economical constraints, preventing installation of physical instruments in all the needed measurement points, to be overcome. Virtual flow meter performance for the alternative models of Samson [http://www.samson.de (2015)] and Sereg-Schlumberger [http://www.slb.com/ (2015)] is compared with the standard IEC 60534-2-1 [Industrial-process control valves—Part 2-1: Flow capacity—sizing equations for fluid flow under installed conditions (2011), https://webstore.iec.ch/publication/2461], for a large temperature range, for both gaseous and liquid helium phases, and for different pressure drops. Then, the calibration function of the transducer is derived. Finally, the experimental validation for the helium gaseous state on the test station for superconducting magnets in the laboratory SM18 [Pirotte et al., AIP Conf. Proc. 1573, 187 (2014)] at CERN is reported.

  20. Proof-of-principle demonstration of a virtual flow meter-based transducer for gaseous helium monitoring in particle accelerator cryogenics.

    PubMed

    Arpaia, P; Blanco, E; Girone, M; Inglese, V; Pezzetti, M; Piccinelli, F; Serio, L

    2015-07-01

    A transducer based on a virtual flow meter is proposed for monitoring helium distribution and consumption in cryogenic systems for particle accelerators. The virtual flow meter allows technical and economical constraints, preventing installation of physical instruments in all the needed measurement points, to be overcome. Virtual flow meter performance for the alternative models of Samson [ http://www.samson.de (2015)] and Sereg-Schlumberger [ http://www.slb.com/ (2015)] is compared with the standard IEC 60534-2-1 [Industrial-process control valves-Part 2-1: Flow capacity-sizing equations for fluid flow under installed conditions (2011), https://webstore.iec.ch/publication/2461], for a large temperature range, for both gaseous and liquid helium phases, and for different pressure drops. Then, the calibration function of the transducer is derived. Finally, the experimental validation for the helium gaseous state on the test station for superconducting magnets in the laboratory SM18 [Pirotte et al., AIP Conf. Proc. 1573, 187 (2014)] at CERN is reported.

  1. Phase separation in hydrogen–helium mixtures at Mbar pressures

    PubMed Central

    Morales, Miguel A.; Schwegler, Eric; Ceperley, David; Pierleoni, Carlo; Hamel, Sebastien; Caspersen, Kyle

    2009-01-01

    The properties of hydrogen–helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures ≈5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter. PMID:19171896

  2. Reversal of nitrogen narcosis in rats by helium pressure.

    PubMed

    Thomas, J R

    1976-09-01

    Changes in operant behavior were obtained for rats breathing nitrogen, helium, and both gases combined. Exposure to 12.9 ATA of nitrogen (O2 maintained at normobaric value of 0.2 ATA) produced complete cessation of responding on a fixed-ratio reinforcement schedule for 1 hour. The addition of elevated pressure of helium (12.1, 18.2, and 24.2 ATA) to the 12.9 ATA of nitrogen resulted in a reinstatement of responding during 1-hour hyperbaric exposures. The reinstatement of responding indicated a reversal of the nitrogen effects on behavior by increased helium pressures. The functional changes in behavior appeared to parallel the pressure produced reversal of anesthesia obtained at much higher pressures.

  3. The thermodynamical instability induced by pressure ionization in fluid helium

    NASA Astrophysics Data System (ADS)

    Li, Qiong; Liu, Hai-Feng; Zhang, Gong-Mu; Zhao, Yan-Hong; Lu, Guo; Tian, Ming-Feng; Song, Hai-Feng

    2016-11-01

    A systematic study of pressure ionization is carried out in the chemical picture by the example of fluid helium. By comparing the variants of the chemical model, it is demonstrated that the behavior of pressure ionization depends on the construction of the free energy function. In the chemical model with the Coulomb free energy described by the Padé interpolation formula, thermodynamical instability induced by pressure ionization is found to be manifested by a discontinuous drop or a continuous fall and rise along the pressure-density curve as well as the pressure-temperature curve, which is very much like the first order liquid-liquid phase transition of fluid hydrogen from the first principles simulations. In contrast, in the variant chemical model with the Coulomb free energy term empirically weakened, no thermodynamical instability is induced when pressure ionization occurs, and the resulting equation of state achieves a good agreement with the first principles simulations of fluid helium.

  4. Effect of dynamic diffusion of air, nitrogen, and helium gaseous media on the microhardness of ionic crystals with juvenile surfaces

    NASA Astrophysics Data System (ADS)

    Klyavin, O. V.; Fedorov, V. Yu.; Chernov, Yu. M.; Shpeizman, V. V.

    2015-09-01

    The load dependences of the microhardness of surface layers of NaCl and LiF ionic single crystals with juvenile surfaces and surfaces exposed to air for a long time measured in the air, nitrogen, and helium gaseous media have been investigated. It has been found that there is a change in the sign of the derivative of the microhardness as a function of the load for LiF crystals indented in helium and after their aging in air, as well as a weaker effect of the nitrogen and air gaseous media on the studied dependences as compared to NaCl crystals. It has also been found that, after the aging of the surface of NaCl crystals in air, there is a change in the sign of the derivative of the microhardness in the nitrogen and air gaseous media, as well as a pronounced change in the microhardness as a function of the time of aging the samples in air as compared to the weaker effect of the gaseous medium for LiF crystals. The obtained data have been analyzed in terms of the phenomenon of dislocation-dynamic diffusion of particles from the external medium into crystalline materials during their plastic deformation along the nucleating and moving dislocations. It has been shown that this phenomenon affects the microhardness through changes in the intensity of dislocation multiplication upon the formation of indentation rosettes in different gaseous media. The performed investigation of the microhardness of the juvenile surface of NaCl and LiF crystals in different gaseous media has revealed for the first time a different character of dislocation-dynamic diffusion of these media in a "pure" form.

  5. Optimization of gaseous helium heater for 2 K cryogenic system for VECC’s superconducting electron linac

    NASA Astrophysics Data System (ADS)

    Ahammed, Manir; Ghosh, Siddhartha; Saha, Subrata; Singh, Sandeep Kumar; Bhattacharya, Tamal Kumar; DuttaGupta, Anjan; Pal, Gautam; Naik, Vaishali; Chakrabarti, Alok

    2014-09-01

    Niobium superconducting radiofrequency cavities are generally operated at around 2 K temperature to achieve a high quality factor by reducing residual surface losses. 2 K temperature is produce by lowering down the pressure of the helium by employing a sub-atmospheric vacuum pumping system. The cavities are immersed in liquid helium bath, maintained in the helium chamber. A special heater is optimized for warming up the helium gas coming out from the helium chamber to 300 K before it enters the pumping system. Keeping in view the uninterrupted and reliable operation of the superconducting electron linac and safe running of the liquid helium plant, a tubular heat exchanger type of heater is designed. Current is passed through the tubes of the heater so as to let the tube banks themselves act as heating element. He gas, passing through the tubes, absorbs the heat and warms up to the desired temperature. Unlike common notion, it has been observed that heater with longer length could reduce the requirement of the heater power but at the cost of extra pumping power, required to counter balance the excess pressure drop caused by the additional length of the heater. Pressure drop is kept within 50 Pa for 2 g/s helium flow rate. The whole lot of tubes, divided into 4 bundles, are electrically connected in series so that current rating of the feed-through could be kept within 750 A. This paper discusses the methodology used for optimizing the design of the heater.

  6. Cold Helium Gas Pressurization For Spacecraft Cryogenic Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Morehead, Robert L.; Atwell. Matthew J.; Hurlbert, Eric A.; Melcher, J. C.

    2017-01-01

    To reduce the dry mass of a spacecraft pressurization system, helium pressurant may be stored at low temperature and high pressure to increase mass in a given tank volume. Warming this gas through an engine heat exchanger prior to tank pressurization both increases the system efficiency and simplifies the designs of intermediate hardware such as regulators, valves, etc. since the gas is no longer cryogenic. If this type of cold helium pressurization system is used in conjunction with a cryogenic propellant, though, a loss in overall system efficiency can be expected due to heat transfer from the warm ullage gas to the cryogenic propellant which results in a specific volume loss for the pressurant, interpreted as the Collapse Factor. Future spacecraft with cryogenic propellants will likely have a cold helium system, with increasing collapse factor effects as vehicle sizes decrease. To determine the collapse factor effects and overall implementation strategies for a representative design point, a cold helium system was hotfire tested on the Integrated Cryogenic Propulsion Test Article (ICPTA) in a thermal vacuum environment at the NASA Glenn Research Center Plum Brook Station. The ICPTA vehicle is a small lander-sized spacecraft prototype built at NASA Johnson Space Center utilizing cryogenic liquid oxygen/liquid methane propellants and cryogenic helium gas as a pressurant to operate one 2,800lbf 5:1 throttling main engine, two 28lbf Reaction Control Engines (RCE), and two 7lbf RCEs (Figure 1). This vehicle was hotfire tested at a variety of environmental conditions at NASA Plum Brook, ranging from ambient temperature/simulated high altitude, deep thermal/high altitude, and deep thermal/high vacuum conditions. A detailed summary of the vehicle design and testing campaign may be found in Integrated Cryogenic Propulsion Test Article Thermal Vacuum Hotfire Testing, AIAA JPC 2017.

  7. Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid Hydrogen

    NASA Astrophysics Data System (ADS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S. L.; Tucker, S.

    2008-03-01

    In support of the development of a micro-gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center (MSFC) with the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray-bar thermodynamic vent system (TVS). The testing, with an ambient heat leak of about 70 W and tank fill levels of 90, 50, and 25%, was performed for 14 days during August and September 2005. The TVS successfully controlled the tank pressure within a ±3.45 kPa band with various gaseous helium (GHe) masses in the ullage. Relative to pressure control with an "all hydrogen" ullage, the GHe presence resulted in 37 to 68% longer pressure reduction cycle durations, depending on the fill level, during the mixing/venting phase of the control cycle. Testing was also conducted to evaluate thermodynamic venting without the recirculation pump operating, at a very low fill level. Although ullage stratification was present, the ullage pressure was successfully controlled without the pump. It was evident that the spray-bar and heat exchanger configuration, which extended almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the pump operating.

  8. 80. DETAIL OF TYPICAL PRESSURE GAUGE IN NITROGEN AND HELIUM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    80. DETAIL OF TYPICAL PRESSURE GAUGE IN NITROGEN AND HELIUM STORAGE AND TRANSFER CONTROL SKIDS ON NORTH END OF SLC-3W FUEL APRON - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  9. Anomalous behavior of cristobalite in helium under high pressure

    NASA Astrophysics Data System (ADS)

    Sato, Tomoko; Takada, Hiroto; Yagi, Takehiko; Gotou, Hirotada; Okada, Taku; Wakabayashi, Daisuke; Funamori, Nobumasa

    2013-01-01

    We have investigated the high-pressure behavior of cristobalite in helium by powder X-ray diffraction. Cristobalite transformed to a new phase at about 8 GPa. This phase is supposed to have a molar volume of about 30 % larger than cristobalite, suggesting the dissolution of helium atoms in its interstitial voids. On further compression, the new phase transformed to a different phase which showed an X-ray diffraction pattern similar to cristobalite X-I at about 21 GPa. On the other hand, when the new phase was decompressed, it transformed to another new phase at about 7 GPa, which is also supposed to have a molar volume of about 25 % larger than cristobalite. On further decompression, the second new phase transformed to cristobalite II at about 2 GPa. In contrast to cristobalite, quartz did not show anomalous behavior in helium. The behavior of cristobalite in helium was also consistent with that in other mediums up to about 8 GPa, where the volume of cristobalite became close to that of quartz. These results suggest that dissolution of helium may be controlled not only by the density (amount of voids) but also by the network structure of SiO4 tetrahedra (topology of voids).

  10. Spontaneous Raman Scattering Diagnostics for High-pressure Gaseous Flames

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet; Reddy, D. R. (Technical Monitor)

    2002-01-01

    A high-pressure (up to 60 atm) gaseous burner facility with optical access that provides steady, reproducible flames with high precision, and the ability to use multiple fuel/oxidizer combinations has been developed. In addition, a high-performance spontaneous Raman scattering system for use in the above facility has also been developed. Together, the two systems will be used to acquire and establish a comprehensive Raman scattering spectral database for use as a quantitative high-pressure calibration of single-shot Raman scattering measurements in high-pressure combustion systems. Using these facilities, the Raman spectra of H2-Air flames were successfully measured at pressures up to 20 atm. The spectra demonstrated clear rotational and ro-vibrational Raman features of H2, N2, and H2O. theoretical Raman spectra of pure rotational H2, vibrational H2, and vibrational N2 were calculated using a classical harmonic-oscillator model with pressure broadening effects and fitted to the data. At a gas temperature of 1889 K for a phi = 1.34 H2-Air flame, the model and the data showed good agreement, confirming a ro-vibrational equilibrium temperature.

  11. Measurement of uranium enrichment for gaseous uranium at low pressure

    SciTech Connect

    Close, D.A.; Pratt, J.C.; Atwater, H.F.; Malanify, J.J.; Nixon, K.V.; Speir, L.G.

    1985-01-01

    X-ray fluoresence determines the amount of total uranium present in gaseous UF/sub 6/ inside cascade header pipes of a uranium centrifuge enrichment facility. A highly collimated source, highly collimated detector, and a very rigid, reproducible geometry are required. Two measurements of the 185.7-keV gamma ray from /sup 235/U using two collimators determine the amount of /sup 235/U present only in the gas phase. The ratio of the gas-only /sup 235/U signal to the total uranium gas-only signal is directly proportional to the enrichment of the process UF/sub 6/ gas. This measurement technique is independent of the deposit that forms on a surface in contact with UF/sub 6/. This measurement technique is independent of the pressure of the gaseous UF/sub 6/. This technique has the required sensitivity to determine whether the process gas is of uranium enrichment less than or equal to 20% or >20%. 6 refs., 4 figs., 4 tabs.

  12. Measurements of the principal Hugoniots of dense gaseous deuterium-helium mixtures: Combined multi-channel optical pyrometry, velocity interferometry, and streak optical pyrometry measurements

    NASA Astrophysics Data System (ADS)

    Li, Zhi-Guo; Chen, Qi-Feng; Gu, Yun-Jun; Zheng, Jun; Chen, Xiang-Rong

    2016-10-01

    The accurate hydrodynamic description of an event or system that addresses the equations of state, phase transitions, dissociations, ionizations, and compressions, determines how materials respond to a wide range of physical environments. To understand dense matter behavior in extreme conditions requires the continual development of diagnostic methods for accurate measurements of the physical parameters. Here, we present a comprehensive diagnostic technique that comprises optical pyrometry, velocity interferometry, and time-resolved spectroscopy. This technique was applied to shock compression experiments of dense gaseous deuterium-helium mixtures driven via a two-stage light gas gun. The advantage of this approach lies in providing measurements of multiple physical parameters in a single experiment, such as light radiation histories, particle velocity profiles, and time-resolved spectra, which enables simultaneous measurements of shock velocity, particle velocity, pressure, density, and temperature and expands understanding of dense high pressure shock situations. The combination of multiple diagnostics also allows different experimental observables to be measured and cross-checked. Additionally, it implements an accurate measurement of the principal Hugoniots of deuterium-helium mixtures, which provides a benchmark for the impedance matching measurement technique.

  13. Quantitative Thermochemical Measurements in High-Pressure Gaseous Combustion

    NASA Technical Reports Server (NTRS)

    Kojima, Jun J.; Fischer, David G.

    2012-01-01

    We present our strategic experiment and thermochemical analyses on combustion flow using a subframe burst gating (SBG) Raman spectroscopy. This unconventional laser diagnostic technique has promising ability to enhance accuracy of the quantitative scalar measurements in a point-wise single-shot fashion. In the presentation, we briefly describe an experimental methodology that generates transferable calibration standard for the routine implementation of the diagnostics in hydrocarbon flames. The diagnostic technology was applied to simultaneous measurements of temperature and chemical species in a swirl-stabilized turbulent flame with gaseous methane fuel at elevated pressure (17 atm). Statistical analyses of the space-/time-resolved thermochemical data provide insights into the nature of the mixing process and it impact on the subsequent combustion process in the model combustor.

  14. High-pressure soot formation and diffusion flame extinction characteristics of gaseous and liquid fuels

    NASA Astrophysics Data System (ADS)

    Karatas, Ahmet Emre

    High-pressure soot formation and flame stability characteristics were studied experimentally in laminar diffusion flames. For the former, radially resolved soot volume fraction and temperature profiles were measured in axisymmetric co-flow laminar diffusion flames of pre-vaporized n-heptane-air, undiluted ethylene-air, and nitrogen and carbon dioxide diluted ethylene-air at elevated pressures. Abel inversion was used to re-construct radially resolved data from the line-of-sight spectral soot emission measurements. For the latter, flame extinction strain rate was measured in counterflow laminar diffusion flames of C1-4 alcohols and hydrocarbon fuels of n-heptane, n-octane, iso-octane, toluene, Jet-A, and biodiesel. The luminous flame height, as marked by visible soot radiation, of the nitrogen- and helium-diluted n-heptane and nitrogen- and carbon dioxide-diluted ethylene flames stayed constant at all pressures. In pure ethylene flames, flame heights initially increased with pressure, but changed little above 5 atm. The maximum soot yield as a function of pressure in nitrogen-diluted n-heptane diffusion flames indicate that n-heptane flames are slightly more sensitive to pressure than gaseous alkane hydrocarbon flames at least up to 7 atm. Ethylene's maximum soot volume fractions were much higher than those of ethane and n-heptane diluted with nitrogen (fuel to nitrogen mass flow ratio is about 0.5). Pressure dependence of the peak carbon conversion to soot, defined as the percentage of fuel's carbon content converted to soot, was assessed and compared to previous measurements with other gaseous fuels. Maximum soot volume fractions were consistently lower in carbon dioxide-diluted flames between 5 and 15 atm but approached similar values to those in nitrogen-diluted flames at 20 atm. This observation implies that the chemical soot suppression effect of carbon dioxide, previously demonstrated at atmospheric pressure, is also present at elevated pressures up to 15 atm

  15. Contamination of liquid oxygen by pressurized gaseous nitrogen

    NASA Technical Reports Server (NTRS)

    Zuckerwar, Allan J.; King, Tracy K.; Ngo, Kim Chi

    1989-01-01

    The penetration of pressurized gaseous nitrogen (GN2) into liquid oxygen (LOX) was investigated experimentally in the 7-inch High Temperature Tunnel, the pilot tunnel for the 8-foot High Temperature Tunnel (8'HTT) at Langley Research Center. A preliminary test using a nuclear monitor revealed the extent of the liquid nitrogen (LN2) build-up at the LOX interface as a function of GN2 pressure. Then an adaptation of the differential flash vaporization technique was used to determine the binary diffusivity of the LOX-LN2 system at a temperature of 90.2 K. The measured value D equals 0.000086 sq cm/s + or - 25 percent together with two prior measurements at lower temperatures revealed an excellent fit to the Arrhenius equation, yielding a pre-exponential factor D sub 0 equals 0.0452 sq cm/s and an activation enthalpy H equals 1.08 kcal/mol. At a pressure of 1700 psi and holding time of 15 min, the penetration of LN2 into LOX (to a 1 percent contamination level) was found to be 0.9 cm, indicating but minimal impact upon 8'HTT operations.

  16. Process to recover tritium from high-pressure helium

    SciTech Connect

    Finn, P.A.; Sze, D.K.

    1986-01-01

    A coolant that has gained increased prominence in fusion reactor designs is high-pressure (greater than or equal to 50 atm) helium. One of the major problems to be resolved with this coolant is effective tritium removal and recovery so that environmental losses are minimized but the efficiency of the plant is not compromised. Since the worse case situation is one in which the high-pressure helium coolant is used not only as a coolant but also as the main tritium recovery route, we directed our attention to designing a tritium recovery system that could handle this worst case, as well as simpler cases. The design that evolved was a system in which a liquid getter (sodium is our example case) is used to strip all tritium, deuterium, and oxygen species from the high-pressure helium. The hydrogen species are removed from the sodium either by using a cold trap or by contacting the sodium with a molten salt. The tritium can be recovered from the molten salt by electrolysis. Impurities, including oxygen, are removed from the sodium through the use of a cold trap on a small fraction (less than or equal to 10%) of the total sodium flow.

  17. Superconducting cable cooling system by helium gas at two pressures

    DOEpatents

    Dean, John W.

    1977-01-01

    Thermally contacting, oppositely streaming, cryogenic fluid streams in the same enclosure in a closed cycle that changes the fluid from a cool high pressure helium gas to a cooler reduced pressure helium gas in an expander so as to be at different temperature ranges and pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T.sub.1. By first circulating the fluid from a refrigerator at one end of the line as a cool gas at a temperature range T.sub.2 to T.sub.3 in the go leg, then circulating the gas through an expander at the other end of the line where the gas becomes a cooler gas at a reduced pressure and at a reduced temperature T.sub.4 and finally by circulating the cooler gas back again to the refrigerator in a return leg at a temperature range T.sub.4 to T.sub.5, while in thermal contact with the gas in the go leg, and in the same enclosure therewith for compression into a higher pressure gas at T.sub.2 in a closed cycle, where T.sub.2 >T.sub.3 and T.sub.5 >T.sub.4, the fluid leaves the enclosure in the go leg as a gas at its coldest point in the go leg, and the temperature distribution is such that the line temperature decreases along its length from the refrigerator due to the cooling from the gas in the return leg.

  18. Extreme ultraviolet spectroscopy of low pressure helium microwave driven discharges

    NASA Astrophysics Data System (ADS)

    Espinho, Susana; Felizardo, Edgar; Tatarova, Elena; Alves, Luis Lemos

    2016-09-01

    Surface wave driven discharges are reliable plasma sources that can produce high levels of vacuum and extreme ultraviolet radiation (VUV and EUV). The richness of the emission spectrum makes this type of discharge a possible alternative source in EUV/VUV radiation assisted applications. However, due to challenging experimental requirements, publications concerning EUV radiation emitted by microwave plasmas are scarce and a deeper understanding of the main mechanisms governing the emission of radiation in this spectral range is required. To this end, the EUV radiation emitted by helium microwave driven plasmas operating at 2.45 GHz has been studied for low pressure conditions. Spectral lines from excited helium atoms and ions were detected via emission spectroscopy in the EUV/VUV regions. Novel data concerning the spectral lines observed in the 23 - 33 nm wavelength range and their intensity behaviour with variation of the discharge operational conditions are presented. The intensity of all the spectral emissions strongly increases with the microwave power delivered to the plasma up to 400 W. Furthermore, the intensity of all the ion spectral emissions in the EUV range decreases by nearly one order of magnitude as the pressure was raised from 0.2 to 0.5 mbar. Work funded by FCT - Fundacao para a Ciencia e a Tecnologia, under Project UID/FIS/50010/2013 and grant SFRH/BD/52412/2013 (PD-F APPLAuSE).

  19. Real-time portal imaging devices operating on high-pressure gaseous electronic principles

    NASA Astrophysics Data System (ADS)

    Giakos, George C.; Richardson, Donna B.; Ghotra, P.; Pillai, Bindu; Seetharaman, Lakshmi; Passalaqua, Anthony M.; DiBianca, Frank A.; Endorf, Robert J.; Devidas, Sreenivas

    1995-05-01

    A novel real-time portal imaging scanning detector, based on high-pressure gaseous electronics principles and operating up to 60 atmospheres, is presented and the predicted performance of this detector is analyzed. The idea is to utilize high pressure gaseous electronics imaging detectors operating in the saturation regime, aimed at improving image performance characteristics in real time portal imaging. As a result, beam localization errors are controlled, identified and corrected accurately and the patient radiotherapy treatment becomes more effective.

  20. Influence of flowing helium gas on plasma plume formation in atmospheric pressure plasma

    SciTech Connect

    Yambe, Kiyoyuki; Konda, Kohmei; Ogura, Kazuo

    2015-05-15

    We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and a foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. The helium gas flowing out of quartz tube mixes with air, and the flow channel is composed of the regions of flowing helium gas and air. The plasma plume length is equivalent to the reachable distance of flowing helium gas. Although the amount of helium gas on the flow channel increases by increasing the inner diameter of quartz tube at the same gas flow velocity, the plasma plume length peaks at around 8 m/s of gas flow velocity, which is the result that a flow of helium gas is balanced with the amount of gas. The plasma plume is formed at the boundary region where the flow of helium gas is kept to the wall of the air.

  1. Plasmid DNA damage induced by helium atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Han, Xu; Cantrell, William A.; Escobar, Erika E.; Ptasinska, Sylwia

    2014-03-01

    A helium atmospheric pressure plasma jet (APPJ) is applied to induce damage to aqueous plasmid DNA. The resulting fractions of the DNA conformers, which indicate intact molecules or DNA with single- or double-strand breaks, are determined using agarose gel electrophoresis. The DNA strand breaks increase with a decrease in the distance between the APPJ and DNA samples under two working conditions of the plasma source with different parameters of applied electric pulses. The damage level induced in the plasmid DNA is also enhanced with increased plasma irradiation time. The reactive species generated in the APPJ are characterized by optical emission spectra, and their roles in possible DNA damage processes occurring in an aqueous environment are also discussed.

  2. Refraction of cylindrical converging shock wave at an air/helium gaseous interface

    NASA Astrophysics Data System (ADS)

    Zhai, Zhigang; Li, Wei; Si, Ting; Luo, Xisheng; Yang, Jiming; Lu, Xiyun

    2017-01-01

    Refraction of a cylindrical converging shock wave at an inclined air/helium interface is investigated. Experimentally, based on the shock dynamics theory, a special wall profile is designed to generate a perfectly cylindrical converging shock wave. A soap film technique is developed to form an inclined discontinuous air/helium interface, and high-speed schlieren photography is adopted to capture the flow. Numerical simulations are also performed to compare with the experimental counterparts and to show details of refraction. In this work, two initial incident angles (45° and 60°) are considered. As the incident shock converges inward, the shock intensity increases while the incident angle decreases, causing possible transitions among the wave patterns. For the case of 45°, an irregular refraction of free precursor refraction (FPR) first occurs and gradually transits into regular refraction, while for the case of 60°, various irregular refractions of twin von Neumann refraction (TNR), twin regular refraction (TRR), free precursor von Neumann refraction (FNR), and FPR occur in sequence. The transition sequences do not belong to any groups described in the planar counterpart, indicating that the classification of the refraction phenomenon in the planar case is not exhaustive or cannot be applied to the converging case. It is also the first time to observe the transition from FNR to FPR, providing an experimental evidence for the previous numerical results. It is deemed that the difference between the velocities of the incident and transmitted shocks propagating along the interface is the primary factor that induces the transitions among wave patterns.

  3. Stimulation of wound healing by helium atmospheric pressure plasma treatment

    NASA Astrophysics Data System (ADS)

    Vasile Nastuta, Andrei; Topala, Ionut; Grigoras, Constantin; Pohoata, Valentin; Popa, Gheorghe

    2011-03-01

    New experiments using atmospheric pressure plasma have found large application in treatment of living cells or tissues, wound healing, cancerous cell apoptosis, blood coagulation on wounds, bone tissue modification, sterilization and decontamination. In this study an atmospheric pressure plasma jet generated using a cylindrical dielectric-barrier discharge was applied for treatment of burned wounds on Wistar rats' skin. The low temperature plasma jet works in helium and is driven by high voltage pulses. Oxygen and nitrogen based impurities are identified in the jet by emission spectroscopy. This paper analyses the natural epithelization of the rats' skin wounds and two methods of assisted epithelization, a classical one using polyurethane wound dressing and a new one using daily atmospheric pressure plasma treatment of wounds. Systemic and local medical data, such as haematological, biochemical and histological parameters, were monitored during entire period of study. Increased oxidative stress was observed for plasma treated wound. This result can be related to the presence in the plasma volume of active species, such as O and OH radicals. Both methods, wound dressing and plasma-assisted epithelization, provided positive medical results related to the recovery process of burned wounds. The dynamics of the skin regeneration process was modified: the epidermis re-epitelization was accelerated, while the recovery of superficial dermis was slowed down.

  4. Applying Chemical Potential and Partial Pressure Concepts to Understand the Spontaneous Mixing of Helium and Air in a Helium-Inflated Balloon

    ERIC Educational Resources Information Center

    Jee-Yon Lee; Hee-Soo Yoo; Jong Sook Park; Kwang-Jin Hwang; Jin Seog Kim

    2005-01-01

    The spontaneous mixing of helium and air in a helium-inflated balloon is described in an experiment in which the partial pressure of the gases in the balloon are determined from the mole factions and the total pressure measured in the balloon. The results described provide a model for teaching concepts of partial pressure, chemical potential, and…

  5. 75 FR 53353 - Notice of Availability of Final Interim Staff Guidance Document No. 25 “Pressure and Helium...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-31

    ... COMMISSION Notice of Availability of Final Interim Staff Guidance Document No. 25 ``Pressure and Helium... Guidance Document No. 25 (ISG-25) ``Pressure and Helium Leakage Testing of the Confinement Boundary of... helium leakage testing and ASME Code required pressure (hydrostatic/pneumatic) testing that is...

  6. Quartz Tuning Fork Pressure Gauge for High-Pressure Liquid Helium

    NASA Astrophysics Data System (ADS)

    Botimer, J.; Velasco, A.; Taborek, P.

    2017-01-01

    We have measured the quality factor Q and the frequency f of a 32-kHz quartz tuning fork immersed in liquid ^4He between 0.9 and 3.0 K, over pressures ranging from the saturated vapor pressure to ≈ 25 atm. At constant pressure, as a function of temperature, the quality factor and frequency have strong features related to the temperature dependence of the superfluid fraction. At constant temperature, Q depends on the superfluid fraction, while the frequency is a smooth function of pressure. The behavior is explained using a simple hydrodynamic model. The liquid helium viscosity is obtained from measured values of Q, and together with tabulated values of the helium density as a function of pressure and temperature, the frequency shift can be parameterized as a function of temperature and pressure. The observed sensitivity is ≈ 7.8 Hz/atm. The quartz tuning fork provides a compact low power method of measuring the pressure in the bulk liquid.

  7. Experimental investigation on pressurization performance of cryogenic tank during high-temperature helium pressurization process

    NASA Astrophysics Data System (ADS)

    Lei, Wang; Yanzhong, Li; Yonghua, Jin; Yuan, Ma

    2015-03-01

    Sufficient knowledge of thermal performance and pressurization behaviors in cryogenic tanks during rocket launching period is of importance to the design and optimization of a pressurization system. In this paper, ground experiments with liquid oxygen (LO2) as the cryogenic propellant, high-temperature helium exceeding 600 K as the pressurant gas, and radial diffuser and anti-cone diffuser respectively at the tank inlet were performed. The pressurant gas requirements, axial and radial temperature distributions, and energy distributions inside the propellant tank were obtained and analyzed to evaluate the comprehensive performance of the pressurization system. It was found that the pressurization system with high-temperature helium as the pressurant gas could work well that the tank pressure was controlled within a specified range and a stable discharging liquid rate was achieved. For the radial diffuser case, the injected gas had a direct impact on the tank inner wall. The severe gas-wall heat transfer resulted in about 59% of the total input energy absorbed by the tank wall. For the pressurization case with anti-cone diffuser, the direct impact of high-temperature gas flowing toward the liquid surface resulted in a greater deal of energy transferred to the liquid propellant, and the percentage even reached up to 38%. Moreover, both of the two cases showed that the proportion of energy left in ullage to the total input energy was quite small, and the percentage was only about 22-24%. This may indicate that a more efficient diffuser should be developed to improve the pressurization effect. Generally, the present experimental results are beneficial to the design and optimization of the pressurization system with high-temperature gas supplying the pressurization effect.

  8. Low temperature plasma RF capacitive discharge in helium at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Hakki, A.; Fayrushin, I.; Kashapov, N.

    2016-01-01

    The paper describes Low temperature plasma RF capacitive discharge in helium at atmospheric pressure. The circuit has been done, to obtain output currentabout 90mA,and the maximum power was 100W, The frequency of the discharging was f = 40MHz.Twolamps (DУ-50) were used in power supply. Helium consumption was about 1.5l/m.

  9. Contrasting pressure-support ventilation and helium-oxygen during exercise in severe COPD.

    PubMed

    Hussain, Omar; Collins, Eileen G; Adiguzel, Nalan; Langbein, W Edwin; Tobin, Martin J; Laghi, Franco

    2011-03-01

    Helium-oxygen mixtures and pressure-support ventilation have been used to unload the respiratory muscles and increase exercise tolerance in COPD. Considering the different characteristics of these techniques, we hypothesized that helium-oxygen would be more effective in reducing exercise-induced dynamic hyperinflation than pressure-support. We also hypothesized that patients would experience greater increases in respiratory rate and minute ventilation with helium-oxygen than with pressure-support. The hypotheses were tested in ten patients with severe COPD (FEV(1) = 28 ± 3% predicted [mean ± SE]) during constant-load cycling (80% maximal workrate) while breathing 30% oxygen-alone, helium-oxygen, and pressure-support in randomized order. As hypothesized, helium-oxygen had greater impact on dynamic hyperinflation than did pressure-support (end-exercise; p = 0.03). For the most part of exercise, respiratory rate and minute ventilation were greater with helium-oxygen than with pressure-support (p ≤ 0.008). During the initial phases of exercise, helium-oxygen caused less rib-cage muscle recruitment than did pressure-support (p < 0.03), and after the start of exercise it caused greater reduction in inspiratory reserve volume (p ≤ 0.02). Despite these different responses, helium-oxygen and pressure-support caused similar increases in exercise duration (oxygen-alone: 6.9 ± 0.8 min; helium-oxygen: 10.7 ± 1.4 min; pressure-support: 11.2 ± 1.6 min; p = 0.003) and similar decreases in inspiratory effort (esophageal pressure-time product), respiratory drive, pulmonary resistance, dyspnea and leg effort (p < 0.03). In conclusion, helium-oxygen reduced exercise-induced dynamic hyperinflation by improving the relationship between hyperinflation and minute ventilation. In contrast, pressure-support reduced hyperinflation solely as a result of lowering ventilation. Helium-oxygen was more effective in reducing exercise-induced dynamic hyperinflation in severe COPD, and was

  10. Miscibility of hydrogen and helium mixtures at megabar pressures

    SciTech Connect

    Klepeis, J.E.; Schafer, K.J.; Barbee, T.W. III; Ross, M.

    1991-09-01

    Models of Jupiter and Saturn postulate a central rock core surrounded by a fluid mixture of hydrogen and helium. These models suggest that the mixture is undergoing phase separation in Saturn but not Jupiter. State-of-the-art total energy calculations of the enthalpy of mixing for ordered alloys of hydrogen and helium confirm that at least partial phase separation has occurred in Saturn and predict that this process has also begun in Jupiter. 15 refs., 2 figs.

  11. High-Pressure Liquid and Gaseous Oxygen Impact Sensitivity Evaluation of Materials For Use At Kennedy Space Center.

    DTIC Science & Technology

    1976-02-01

    NASA TECHNICAL NOTE NASA TN D-8160 "St 19960227 043 HIGH-PRESSURE LIQUID AND GASEOUS OXYGEN IMPACT SENSITIVITY EVALUATION OF MATERIALS FOR USE...Accession No 3. Recipient’s Catalog Na. HIGH-PRESSURE LIQUID AND GASEOUS OXYGEN IMPACT SENSITIVITY EVALUATION OF MATERIALS FOR USE AT KENNEDY...Supplementary Notes 16. Abstract Many materials will ignite or explode when in contact with gaseous oxygen (GOX) or liquid oxygen (LOX) if

  12. Calibrating the Helium Pressurization System for the Space Shuttle Liquid-Hydrogen Tank

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Analysis of the results from the STS-114 tanking tests and subsequent launch called into question existing thermal and mass models of helium pressurization of the liquid hydrogen tank. This hydrogen tank, which makes up the bottom two-thirds of the External Tank, is pressurized prior to launch to avoid cavitation in the Shuttle Main Engine pumps. At about 2 minutes prior to launch, the main vent valve is closed, and pressurized helium flows into the tank ullage space to achieve set point pressure. As the helium gas cools, its pressure drops, calling for additional helium. Subsequent helium flows are provided in short, timed pulses. The number of pulses is taken as a rough leak indicator. An analysis of thermal models by Marshall Space Flight Center showed considerable uncertainty in the pressure-versus-time behavior of the helium ullage space and the ability to predict the number of pulses normally expected. Kennedy Space Center proposed to calibrate the dime-sized orifice, which together with valves, controls the helium flow quantity (Figure 1). Pressure and temperature sensors were installed to provide upstream and downstream measurements necessary to compute flow rate based on the orifice discharge coefficient. An assessment of flow testing with helium indicated an extremely costly use of this critical resource. In order to reduce costs, we proposed removing the orifices from each Mobile Launcher Platform (MLP) and asking Colorado Engineering Experiment Station Inc. (CEESI) to calibrate the flow. CEESI has a high-pressure air flow system with traceable flow meters capable of handling the large flow rates. However, literature research indicated that square-edged orifices of small diameters often exhibit significant hysteresis and nonrepeatability in the vicinity of choked or sonic flow. Fortunately, the MLP orifices behaved relatively well in testing (Figure 2). Using curve fitting of the air-flow data, in conjunction with ASME orifice modeling equations, a

  13. Transfer of gaseous oxygen from high-pressure containers and the Joule-Thomson inversion

    NASA Technical Reports Server (NTRS)

    Schumann, E. R.

    1974-01-01

    From the experiments performed in study, it was determined that oxygen transferred at ambient temperature and pressures up to 10,000 psig consistently dropped in temperature. All results therefore indicate that gaseous oxygen transferred at ambient temperature does not exhibit Joule-Thomson inversion below 10,000 psig.

  14. Modeling the pressure increase in liquid helium cryostats after failure of the insulating vacuum

    SciTech Connect

    Heidt, C.; Grohmann, S.; Süßer, M.

    2014-01-29

    The pressure relief system of liquid helium cryostats requires a careful design, due to helium's low enthalpy of vaporization and due to the low operating temperature. Hazard analyses often involve the failure of the insulating vacuum in the worst-case scenario. The venting of the insulating vacuum and the implications for the pressure increase in the helium vessel, however, have not yet been fully analyzed. Therefore, the dimensioning of safety devices often requires experience and reference to very few experimental data. In order to provide a better foundation for the design of cryogenic pressure relief systems, this paper presents an analytic approach for the strongly dynamic process induced by the loss of insulating vacuum. The model is based on theoretical considerations and on differential equation modeling. It contains only few simplifying assumptions, which will be further investigated in future experiments. The numerical solutions of example calculations are presented with regard to the heat flux into the helium vessel, the helium pressure increase and the helium flow rate through the pressure relief device. Implications concerning two-phase flow and the influence of kinetic energy are discussed.

  15. Measurement of viscosity of gaseous mixtures at atmospheric pressure

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Mall, G. H.; Chegini, H.

    1986-01-01

    Coefficients of viscosity of various types of gas mixtures, including simulated natural-gas samples, have been measured at atmospheric pressure and room temperature using a modified capillary tube method. Pressure drops across the straight capillary tube section of a thermal mass flowmeter were measured for small, well-defined, volume flow rates for the test gases and for standard air. In this configuration, the flowmeter provides the volumetric flow rates as well as a well-characterized capillary section for differential pressure measurements across it. The coefficients of viscosity of the test gases were calculated using the reported value of 185.6 micro P for the viscosity of air. The coefficients of viscosity for the test mixtures were also calculated using Wilke's approximation of the Chapman-Enskog (C-E) theory. The experimental and calculated values for binary mixtures are in agreement within the reported accuracy of Wilke's approximation of the C-E theory. However, the agreement for multicomponent mixtures is less satisfactory, possible because of the limitations of Wilkes's approximation of the classical dilute-gas state model.

  16. Method and apparatus for the selective separation of gaseous coal gasification products by pressure swing adsorption

    DOEpatents

    Ghate, M.R.; Yang, R.T.

    1985-10-03

    Bulk separation of the gaseous components of multi-component gases provided by the gasification of coal including hydrogen, carbon monoxide, methane, and acid gases (carbon dioxide plus hydrogen sulfide) are selectively adsorbed by a pressure swing adsorption technique using activated carbon zeolite or a combination thereof as the adsorbent. By charging a column containing the adsorbent with a gas mixture and pressurizing the column to a pressure sufficient to cause the adsorption of the gases and then reducing the partial pressure of the contents of the column, the gases are selectively and sequentially desorbed. Hydrogen, the least absorbable gas of the gaseous mixture, is the first gas to be desorbed and is removed from the column in a co-current direction followed by the carbon monoxide, hydrogen and methane. With the pressure in the column reduced to about atmospheric pressure the column is evacuated in a countercurrent direction to remove the acid gases from the column. The present invention is particularly advantageous as a producer of high purity hydrogen from gaseous products of coal gasification and as an acid gas scrubber. 2 figs., 2 tabs.

  17. Method and apparatus for the selective separation of gaseous coal gasification products by pressure swing adsorption

    DOEpatents

    Ghate, Madhav R.; Yang, Ralph T.

    1987-01-01

    Bulk separation of the gaseous components of multi-component gases provided by the gasification of coal including hydrogen, carbon monoxide, methane, and acid gases (carbon dioxide plus hydrogen sulfide) are selectively adsorbed by a pressure swing adsorption technique using activated carbon, zeolite or a combination thereof as the adsorbent. By charging a column containing the adsorbent with a gas mixture and pressurizing the column to a pressure sufficient to cause the adsorption of the gases and then reducing the partial pressure of the contents of the column, the gases are selectively and sequentially desorbed. Hydrogen, the least absorbable gas of the gaseous mixture, is the first gas to be desorbed and is removed from the column in a co-current direction followed by the carbon monoxide, hydrogen and methane. With the pressure in the column reduced to about atmospheric pressure the column is evacuated in a countercurrent direction to remove the acid gases from the column. The present invention is particularly advantageous as a producer of high parity hydrogen from gaseous products of coal gasification and as an acid gas scrubber.

  18. Recovery of purified helium or hydrogen from gas mixtures

    DOEpatents

    Merriman, J.R.; Pashley, J.H.; Stephenson, M.J.; Dunthorn, D.I.

    1974-01-15

    A process is described for the removal of helium or hydrogen from gaseous mixtures also containing contaminants. The gaseous mixture is contacted with a liquid fluorocarbon in an absorption zone maintained at superatomspheric pressure to preferentially absorb the contaminants in the fluorocarbon. Unabsorbed gas enriched in hydrogen or helium is withdrawn from the absorption zone as product. Liquid fluorocarbon enriched in contaminants is withdrawn separately from the absorption zone. (10 claims)

  19. CFD Modeling of Helium Pressurant Effects on Cryogenic Tank Pressure Rise Rates in Normal Gravity

    NASA Technical Reports Server (NTRS)

    Grayson, Gary; Lopez, Alfredo; Chandler, Frank; Hastings, Leon; Hedayat, Ali; Brethour, James

    2007-01-01

    A recently developed computational fluid dynamics modeling capability for cryogenic tanks is used to simulate both self-pressurization from external heating and also depressurization from thermodynamic vent operation. Axisymmetric models using a modified version of the commercially available FLOW-3D software are used to simulate actual physical tests. The models assume an incompressible liquid phase with density that is a function of temperature only. A fully compressible formulation is used for the ullage gas mixture that contains both condensable vapor and a noncondensable gas component. The tests, conducted at the NASA Marshall Space Flight Center, include both liquid hydrogen and nitrogen in tanks with ullage gas mixtures of each liquid's vapor and helium. Pressure and temperature predictions from the model are compared to sensor measurements from the tests and a good agreement is achieved. This further establishes the accuracy of the developed FLOW-3D based modeling approach for cryogenic systems.

  20. Evaluation of membrane oxygenators and reservoirs in terms of capturing gaseous microemboli and pressure drops.

    PubMed

    Guan, Yulong; Palanzo, David; Kunselman, Allen; Undar, Akif

    2009-11-01

    An increasing amount of evidence points to cerebral embolization during cardiopulmonary bypass (CPB) as the principal etiologic factor of neurologic complications. In this study, the capability of capturing and classification of gaseous emboli and pressure drop of three different membrane oxygenators (Sorin Apex, Terumo Capiox SX25, Maquet QUADROX) were measured in a simulated adult model of CPB using a novel ultrasound detection and classification quantifier system. The circuit was primed with 1000 mL heparinized human packed red blood cells and 1000 mL lactated Ringer's solution (total volume 2000 mL, corrected hematocrit 26-28%). After the injection of 5 mL air into the venous line, an Emboli Detection and Classification Quantifier was used to simultaneously record microemboli counts at post-pump, post-oxygenator, and post-arterial filter sites. Trials were conducted at normothermic (35 degrees C) and hypothermic (25 degrees C) conditions. Pre-oxygenator and post-oxygenator pressure were recorded in real time and pressure drop was calculated. Maquet QUADROX membrane oxygenator has the lowest pressure drops compared to the other two oxygenators (P < 0.001). The comparison among the three oxygenators indicated better capability of capturing gaseous emboli with the Maquet QUADROX and Terumo Capiox SX25 membrane oxygenator and more emboli may pass through the Sorin Apex membrane oxygenator. Microemboli counts uniformly increased with hypothermic perfusion (25 degrees C). Different types of oxygenators and reservoirs have different capability of capturing gaseous emboli and transmembrane pressure drop. Based on this investigation, Maquet QUADROX membrane oxygenator has the lowest pressure drop and better capability for capturing gaseous microemboli.

  1. Electrical Properties for Capacitively Coupled Radio Frequency Discharges of Helium and Neon at Low Pressure

    NASA Astrophysics Data System (ADS)

    Tanisli, Murat; Sahin, Neslihan; Demir, Suleyman

    2016-10-01

    In this study, the symmetric radio frequency (RF) electrode discharge is formed between the two electrodes placing symmetric parallel. The electrical properties of symmetric capacitive RF discharge of pure neon and pure helium have been obtained from current and voltage waveforms. Calculations are done according to the homogeneous discharge model of capacitively coupled radio frequency (CCRF) using with the data in detail. Electrical properties of bulk plasma and sheath capacitance are also investigated at low pressure with this model. This study compares the electrical characteristics and sheath capacitance changes with RF power and pressure for helium and neon discharges. Also, the aim of the study is to see the differences between helium and neon discharges' current and voltage values. Their root-mean-square voltages and currents are obtained from Tektronix 3052C oscilloscope. Modified homogeneous discharge model of CCRF is used for low pressure discharges and the calculations are done using experimental results. It is seen that homogeneous discharge model of CCRF is usable with modification and then helium and neon discharge's electrical properties are investigated and presented with a comparison. Helium discharge's voltage and current characteristic have smaller values than neon's. It may be said that neon discharge is a better conductor than helium discharge. It is seen that the sheath capacitance is inversely correlation with sheath resistance.

  2. Thermodynamic analysis of helium boil-off experiments with pressure variations

    NASA Astrophysics Data System (ADS)

    Cha, Y. S.; Niemann, R. C.; Hull, J. R.

    A thermodynamic analysis by calorimetric experiments in a system with changing pressure is presented. A general equation is derived for use in calculating the rate of heat loss from measured mass flow rate. The results show that the largest contribution from pressure variation is the sensible heat of liquid helium in a Dewar. A dimensionless parameter that was identified provides an indication of the importance of pressure variation relative to the latent heat of vaporization during an experiment. This dimensionless parameter is a function of system pressure land the thermodynamic properties of helium), rate of change of system pressure, liquid helium inventory in the Dewar and measured mass flow rate. In the special case when the effect of pressure variation is small compared to the latent heat of vaporization, the heat loss rate is the product of the measured mass flow rate and the latent heat of vaporization, multiplied by a correction factor that is a function of the ratio of vapour density to liquid density. This correction factor is significant for helium at pressures near or above 1 atm and should always be included in the calculation.

  3. Bronchomotor response to cold air or helium-oxygen at normal and high ambient pressures.

    PubMed

    Jammes, Y; Burnet, H; Cosson, P; Lucciano, M

    1988-05-01

    Effects of inhalation of cold air or helium-oxygen mixture on lung resistance (RL) were studied in anesthetized and tracheotomized rabbits under normal ambient pressure and in human volunteers under normo- and hyperbaric conditions. In artificially ventilated rabbits, an increase in RL occurred when the tracheal temperature fell to 10 degrees C. This effect was more than double with helium breathing compared to air, despite a lower respiratory heat loss by convection (Hc) with helium. In 3 normal humans, inhalation of cold air (mouth temperature = 8 degrees C) at sea level had no effect on RL value. However, with a helium-nitrogen-oxygen mixture, a weak but significant increase in RL due to cold gas breathing was measured in 1 subject at 2 ATA and in 2 individuals at 3.5 ATA. The density of inhaled gas mixture (air or He-N2-O2) was near the same in the three circumstances (1, 2, and 3.5 ATA) but Hc value increased with helium. At 8 ATA a 30-55% increase in RL occurred in the 3 divers during inhalation of cold gas (Hc was multiplied by 6 compared to air at sea level) and at 25 ATA the cold-induced bronchospasm ranged between 38 and 95% (Hc multiplied by 27). Thus, in rabbits and humans helium breathing enhanced the cold-induced increase in RL at normal or elevated ambient pressure, and this effect was interpreted as resulting from different mechanisms in the two circumstances.

  4. Design and Test of a Liquid Oxygen / Liquid Methane Thruster with Cold Helium Pressurization Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Melcher, John C.; Morehead, Robert L.; Atwell, Matthew J.; Hurlbert, Eric A.

    2015-01-01

    A liquid oxygen / liquid methane 2,000 lbf thruster was designed and tested in conjuction with a nozzle heat exchanger for cold helium pressurization. Cold helium pressurization systems offer significant spacecraft vehicle dry mass savings since the pressurant tank size can be reduced as the pressurant density is increased. A heat exchanger can be incorporated into the main engine design to provide expansion of the pressurant supply to the propellant tanks. In order to study the systems integration of a cold-helium pressurization system, a 2,000 lbf thruster with a nozzle heat exchanger was designed for integration into the Project Morpheus vehicle at NASA Johnson Space Center. The testing goals were to demonstrate helium loading and initial conditioning to low temperatures, high-pressure/low temperature storage, expansion through the main engine heat exchanger, and propellant tank injection/pressurization. The helium pressurant tank was an existing 19 inch diameter composite-overwrap tank, and the targert conditions were 4500 psi and -250 F, providing a 2:1 density advantage compared to room tempatrue storage. The thruster design uses like-on-like doublets in the injector pattern largely based on Project Morpheus main engine hertiage data, and the combustion chamber was designed for an ablative chamber. The heat exchanger was installed at the ablative nozzle exit plane. Stand-alone engine testing was conducted at NASA Stennis Space Center, including copper heat-sink chambers and highly-instrumented spoolpieces in order to study engine performance, stability, and wall heat flux. A one-dimensional thermal model of the integrated system was completed. System integration into the Project Morpheus vehicle is complete, and systems demonstrations will follow.

  5. Equation of State and Electrical Conductivity of Helium at High Pressures and Temperatures

    NASA Astrophysics Data System (ADS)

    McWilliams, R. S.; Eggert, J. H.; Loubeyre, P.; Brygoo, S.; Collins, G.; Jeanloz, R.

    2004-12-01

    Helium, the second-most abundant element in the universe and giant planets, is expected to metallize at much higher pressures and temperatures than the most abundant element, hydrogen. The difference in chemical-bonding character, between insulator and metal, is expected to make hydrogen-helium mixtures immiscible throughout large fractions of planetary interiors, and therefore subject to gravitational separation contributing significantly to the internal dynamics of giant planets. Using laser-driven shock waves on samples pre-compressed in high-pressure cells, we have obtained the first measurements of optical reflectivity from the shock front in helium to pressures of 146 GPa. The reflectivity exceeds 5% above \\ensuremath{\\sim} 100 GPa, indicating high electrical conductivity. By varying the initial pressure (hence density) of the sample, we can access a much wider range of final pressure-temperature conditions than is possible in conventional Hugoniot experiments. Our work increases by nine-fold the pressure range of single-shock measurements, in comparison with gas-gun experiments, and yields results in agreement with the Saumon, Chabrier and Van Horn (1994) equation of state for helium. This changes the internal structures inferred for Jupiter-size planets, relative to models based on earlier equations of state (e. g., SESAME).

  6. Numerical Investigation of Thermal Distribution and Pressurization Behavior in Helium Pressurized Cryogenic Tank by Introducing a Multi-component Model

    NASA Astrophysics Data System (ADS)

    Lei, Wang; Yanzhong, Li; Zhan, Liu; Kang, Zhu

    An improved CFD model involving a multi-component gas mixturein the ullage is constructed to predict the pressurization behavior of a cryogenic tank considering the existence of pressurizing helium.A temperature difference between the local fluid and its saturation temperature corresponding to the vapor partial pressure is taken as the phase change driving force. As practical application of the model, hydrogen and oxygen tanks with helium pressurization arenumerically simulated by using themulti-component gas model. The results presentthat the improved model produce higher ullage temperature and pressure and lower wall temperaturethan those without multi-component consideration. The phase change has a slight influence on thepressurization performance due to the small quantities involved.

  7. [High pressure processing of spices in atmosphere of helium for decrease of microbiological contamination].

    PubMed

    Windyga, Bozena; Fonberg-Broczek, Monika; Sciezyńska, Halina; Skapska, Sylwia; Górecka, Krystyna; Grochowska, Anna; Morawski, Andrzej; Szczepek, Janusz; Karłowski, Kazimierz; Porowski, Sylwester

    2008-01-01

    The aim of the study was to investigate the microbiological decontamination of coriander and caraway when HPP technology was applied in elevated temperature in helium atmosphere. The HPP and heat treatment was conducted for 30 minutes at 800 and 1 000 MPa and temperature range was 60 - 121 degrees C. Contamination with aerobic mesophilic bacteria was decreased by about 2 logarithmic cycles. Total elimination of coliform and yeast and moulds was observed. The efficacy of HPP treatment under helium atmosphere depended on the content of the water in tested samples. It can be concluded that high pressure treatment under atmosphere of helium, combination of proper high pressure and time improved the microbiological quality of spices.

  8. Dynamics of liquid helium boil-off experiments with a step change in pressure

    NASA Astrophysics Data System (ADS)

    Cha, Y. S.; Niemann, R. C.; Hull, J. R.

    The results of dynamic analysis of the effect of pressure variations during helium boil-off experiments are presented. A general solution of the diffusion equation with a time-dependent boundary condition is employed to describe the dynamic response of the liquid helium system under variable pressure conditions, and a solution is obtained for the special case when the system is subjected to a step change in pressure. The calculated temperature response of the liquid indicates that most of the experiments were not likely to have reached equilibrium as a result of the low thermal diffusivity of liquid helium. The initial rate of evaporation or condensation is large, and the rate decreases sharply with time. A method is proposed to account for the transient effect that is observed during calculation of the heat loss rate from a helium boil-off experiment. By assuming that there is no mixing at all, the present analysis provides an estimate of the upper (condensation) or lower (evaporation) bound of the heat loss rate as a result of a pressure increase or decrease in the system. A previously reported equilibrium analysis is expected to apply to situations where complete mixing occurred in the bulk liquid and provides the opposite limits.

  9. Thermophysical properties of helium-4 from 4 to 3000 R with pressures to 15000 psia

    NASA Technical Reports Server (NTRS)

    Mccarty, R. D.

    1972-01-01

    Data on many of the properties of helium commonly used in engineering calculations are compiled over as wide a temperature and pressure range as is practical. These properties are presented in a form which is convenient to the engineer. All of these properties have been critically evaluated and represent the best values for that property at this time.

  10. Phase equilibria in molecular hydrogen-helium mixtures at high pressures

    NASA Technical Reports Server (NTRS)

    Streett, W. B.

    1973-01-01

    Experiments on phase behavior in hydrogen-helium mixtures have been carried out at pressures up to 9.3 kilobars, at temperatures from 26 to 100 K. Two distinct fluid phases are shown to exist at supercritical temperatures and high pressures. Both the trend of the experimental results and an analysis based on the van der Waals theory of mixtures suggest that this fluid-fluid phase separation persists at temperatures and pressures beyond the range of these experiments, perhaps even to the limits of stability of the molecular phases. The results confirm earlier predictions concerning the form of the hydrogen-helium phase diagram in the region of pressure-induced solidification of the molecular phases at supercritical temperatures. The implications of this phase diagram for planetary interiors are discussed.

  11. Compression of helium to high pressures and temperatures using a ballistic piston apparatus

    NASA Technical Reports Server (NTRS)

    Roman, B. P.; Rovel, G. P.; Lewis, M. J.

    1971-01-01

    Some preliminary experiments are described which were carried out in a high enthalpy laboratory to investigate the compression of helium, a typical shock-tube driver gas, to very high pressures and temperatures by means of a ballistic piston. The purpose of these measurements was to identify any problem areas in the compression process, to determine the importance of real gas effects duDC 47355s process, and to establish the feasibility of using a ballistic piston apparatus to achieve temperatures in helium in excess of 10,000 K.

  12. Study on the Property Evolution of Atmospheric Pressure Plasma Jets in Helium

    NASA Astrophysics Data System (ADS)

    Chang, Zhengshi; Yao, Congwei; Mu, Haibao; Zhang, Guanjun

    2014-01-01

    Nowadays atmospheric pressure plasma jets (APPJs) are being widely applied to many fields and have received growing interests from cold plasma community. A helium APPJ with co-axial double ring electrode configuration is driven by an AC high voltage power with an adjustable frequency of 1-60 kHz. Experiments are conducted for acquiring the electrical and optical properties of APPJ, including the discharge mode, current peak's phase and APPJ's length, etc. Moreover, the actions of Penning effect on APPJ are discussed by adding impurity nitrogen into highly pure helium. The results may contribute to further research and applications of APPJs.

  13. Cold Helium Pressurization for Liquid Oxygen/Liquid Methane Propulsion Systems: Fully-Integrated Hot-Fire Test Results

    NASA Technical Reports Server (NTRS)

    Morehead, R. L.; Atwell, M. J.; Melcher, J. C.; Hurlbert, E. A.

    2016-01-01

    Hot-fire test demonstrations were successfully conducted using a cold helium pressurization system fully integrated into a liquid oxygen (LOX) / liquid methane (LCH4) propulsion system (Figure 1). Cold helium pressurant storage at near liquid nitrogen (LN2) temperatures (-275 F and colder) and used as a heated tank pressurant provides a substantial density advantage compared to ambient temperature storage. The increased storage density reduces helium pressurant tank size and mass, creating payload increases of 35% for small lunar-lander sized applications. This degree of mass reduction also enables pressure-fed propulsion systems for human-rated Mars ascent vehicle designs. Hot-fire test results from the highly-instrumented test bed will be used to demonstrate system performance and validate integrated models of the helium and propulsion systems. A pressurization performance metric will also be developed as a means to compare different active pressurization schemes.

  14. Gaseous electron multiplier gain characteristics using low-pressure Ar/CO2

    NASA Astrophysics Data System (ADS)

    Rogers, T.; McEntaffer, R.; Schultz, T.; McCoy, J.; Miles, D.; Tutt, J.

    2017-04-01

    Gaseous Electron Multiplier detectors, or GEMs, show promise for use on space-based X-ray missions. Operating pressure strongly affects the gain of the detector and must be optimized for best performance. We have measured the gain characteristics of a GEM detector at various pressures below atmosphere using a mixture of Ar:CO2 with the goal of maximizing gain to push GEM capabilities to the lowest energies possible. This paper discusses our tests, results, and their implications for choosing a detector pressure. We found that at any operating pressure the detector voltage can be adjusted to achieve roughly the same maximum gain prior to the onset of electrical discharges. We also find that the gain varies substantially by spatial location across the detector, but this variation is insensitive to changes in pressure allowing it to be calibrated and corrected if necessary. The detector pressure can therefore be optimized in the interest of other performance parameters such as leak rate, window stress, power requirements, or quantum efficiency without concern for negatively affecting the gain. These results can inform the choice of operating pressure and voltage for GEMs used onboard future space missions.

  15. Gaseous electron multiplier gain characteristics using low-pressure Ar/CO2

    NASA Astrophysics Data System (ADS)

    Rogers, T.; McEntaffer, R.; Schultz, T.; McCoy, J.; Miles, D.; Tutt, J.

    2017-03-01

    Gaseous Electron Multiplier detectors, or GEMs, show promise for use on space-based X-ray missions. Operating pressure strongly affects the gain of the detector and must be optimized for best performance. We have measured the gain characteristics of a GEM detector at various pressures below atmosphere using a mixture of Ar:CO2 with the goal of maximizing gain to push GEM capabilities to the lowest energies possible. This paper discusses our tests, results, and their implications for choosing a detector pressure. We found that at any operating pressure the detector voltage can be adjusted to achieve roughly the same maximum gain prior to the onset of electrical discharges. We also find that the gain varies substantially by spatial location across the detector, but this variation is insensitive to changes in pressure allowing it to be calibrated and corrected if necessary. The detector pressure can therefore be optimized in the interest of other performance parameters such as leak rate, window stress, power requirements, or quantum efficiency without concern for negatively affecting the gain. These results can inform the choice of operating pressure and voltage for GEMs used onboard future space missions.

  16. Measured pressure distributions of large-angle cones in hypersonic flows of tetrafluoromethane, air, and helium

    NASA Technical Reports Server (NTRS)

    Jones, R. A.; Hunt, J. L.

    1973-01-01

    An experimental study of surface pressure distributions on a family of blunt and sharp large angle cones was made in hypersonic flows of helium, air, and tetrafluoromethane. The effective isentropic exponents of these flows were 1.67, 1.40, and 1.12. Thus, the effect of large shock density ratios such as might be encountered during planetary entry because of real-gas effects could be studied by comparing results in tetrafluoromethane with those in air and helium. It was found that shock density ratio had a large effect on both shock shape and pressure distribution. The differences in pressure distribution indicate that for atmospheric flight at high speed where real-gas effects produce large shock density ratios, large-angle cone vehicles can be expected to experience different trim angles of attack, drag coefficient, and lift-drag ratios than those for ground tests in air wind tunnels.

  17. Thermodynamics of hydrogen-helium mixtures at high pressure and finite temperature

    NASA Technical Reports Server (NTRS)

    Hubbard, W. B.

    1972-01-01

    A technique is reviewed for calculating thermodynamic quantities for mixtures of light elements at high pressure, in the metallic state. Ensemble averages are calculated with Monte Carlo techniques and periodic boundary conditions. Interparticle potentials are assumed to be coulombic, screened by the electrons in dielectric function theory. This method is quantitatively accurate for alloys at pressures above about 10 Mbar. An alloy of equal parts hydrogen and helium by mass appears to remain liquid and mixed for temperatures above about 3000 K, at pressures of about 15 Mbar. The additive volume law is satisfied to within about 10%, but the Gruneisen equation of state gives poor results. A calculation at 1300 K shows evidence of a hydrogen-helium phase separation.

  18. High-Pressure Gaseous Burner (HPGB) Facility Completed for Quantitative Laser Diagnostics Calibration

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet

    2002-01-01

    A gas-fueled high-pressure combustion facility with optical access, which was developed over the last 2 years, has just been completed. The High Pressure Gaseous Burner (HPGB) rig at the NASA Glenn Research Center can operate at sustained pressures up to 60 atm with a variety of gaseous fuels and liquid jet fuel. The facility is unique as it is the only continuous-flow, hydrogen-capable, 60-atm rig in the world with optical access. It will provide researchers with new insights into flame conditions that simulate the environment inside the ultra-high-pressure-ratio combustion chambers of tomorrow's advanced aircraft engines. The facility provides optical access to the flame zone, enabling the calibration of nonintrusive optical diagnostics to measure chemical species and temperature. The data from the HPGB rig enables the validation of numerical codes that simulate gas turbine combustors, such as the National Combustor Code (NCC). The validation of such numerical codes is often best achieved with nonintrusive optical diagnostic techniques that meet these goals: information-rich (multispecies) and quantitative while providing good spatial and time resolution. Achieving these goals is a challenge for most nonintrusive optical diagnostic techniques. Raman scattering is a technique that meets these challenges. Raman scattering occurs when intense laser light interacts with molecules to radiate light at a shifted wavelength (known as the Raman shift). This shift in wavelength is unique to each chemical species and provides a "fingerprint" of the different species present. The facility will first be used to gather a comprehensive data base of laser Raman spectra at high pressures. These calibration data will then be used to quantify future laser Raman measurements of chemical species concentration and temperature in this facility and other facilities that use Raman scattering.

  19. The Role of Helium Metastable States in Radio-Frequency Helium-Oxygen Atmospheric Pressure Plasma Jets: Measurement and Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Niemi, Kari; Waskoenig, Jochen; Sadeghi, Nader; Gans, Timo; O'Connell, Deborah

    2011-10-01

    Absolute densities of metastable He atoms were measured line-of sight integrated along the plasma channel of a capacitively-coupled radio-frequency driven atmospheric pressure plasma jet operated in helium oxygen mixtures by tunable diode-laser absorption spectroscopy. Dependencies of the He metastable density with oxygen admixtures up to 1 percent were investigated. Results are compared to a 1-d numerical simulation, which includes a semi-kinetical treatment of the electron dynamics and the complex plasma chemistry (20 species, 184 reactions), and very good agreement is found. The main formation mechanisms for the helium metastables are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  20. Atmospheric pressure helium afterglow discharge detector for gas chromatography

    DOEpatents

    Rice, Gary; D'Silva, Arthur P.; Fassel, Velmer A.

    1986-05-06

    An apparatus for providing a simple, low-frequency electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

  1. Atmospheric pressure helium afterglow discharge detector for gas chromatography

    DOEpatents

    Rice, G.; D'Silva, A.P.; Fassel, V.A.

    1985-04-05

    An apparatus for providing a simple, low-frequency, electrodeless discharge system for atmospheric pressure afterglow generation. A single quartz tube through which a gas mixture is passed is extended beyond a concentric electrode positioned thereabout. A grounding rod is placed directly above the tube outlet to permit optical viewing of the discharge between the electrodes.

  2. Nonequilibrium gaseous heat transfer in pressure-driven plane Poiseuille flow.

    PubMed

    John, Benzi; Gu, Xiao-Jun; Emerson, David R

    2013-07-01

    Nonequilibrium heat and mass transfer in a pressure-driven plane Poiseuille flow is investigated using the direct simulation Monte Carlo method from the early slip to the free molecular regime. Our investigations reveal several nonintuitive, nonequilibrium thermal flow patterns, including expansion cooling near the walls, a nonconstant pressure profile, and counter-gradient heat transfer along the channel center-line. A bimodal trend in the tangential heat flux is found in the slip and the early transition regime. In the upper transition and free molecular regime, the net heat flow in the entire channel is largely unidirectional and in the opposite direction of mass flow. However, in the slip and the early transition regime, a two-way heat flow is observed in the channel as the normal heat flux profile plays a key role in determining the net gaseous heat flow direction. Moreover, the heat flow rate profile exhibits a maximum value at an intermediate value of Knudsen number. The effects of incomplete surface accommodation on nonequilibrium heat flow are also investigated in this work. It is shown that for very low values of the accommodation coefficient, the gaseous heat flow direction is reversed and is consistently in the direction of mass flow.

  3. Methods to improve pressure, temperature and velocity accuracies of filtered Rayleigh scattering measurements in gaseous flows

    NASA Astrophysics Data System (ADS)

    Doll, Ulrich; Burow, Eike; Stockhausen, Guido; Willert, Christian

    2016-12-01

    Frequency scanning filtered Rayleigh scattering is able to simultaneously provide time-averaged measurements of pressure, temperature and velocity in gaseous flows. By extending the underlying mathematical model, a robust alternative to existing approaches is introduced. Present and proposed model functions are then characterized during a detailed uncertainty analysis. Deviations between the analytical solution of a jet flow experiment and measured results could be related to laser-induced background radiation as well as the Rayleigh scattering’s spectral distribution. In applying a background correction method and by replacing the standard lineshape model by an empirical formulation, detrimental effects on pressure, temperature and velocity accuracies could be reduced below 15 hPa, 2.5 K and 2.7 m s-1.

  4. Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S.; Tucker, S.

    2006-01-01

    In support of the development of a zero gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray bar thermodynamic vent system (TVS). Fourteen days of testing was performed in August - September 2005, with an ambient heat leak of about 70-80 watts and tank fill levels of 90%, 50%, and 25%. The TVS successfully controlled the tank pressure within a +/- 3.45 kPa (+/- 0.5 psi) band with various helium concentration levels in the ullage. Relative to pressure control with an "all hydrogen" ullage, the helium presence resulted in 10 to 30 per cent longer pressure reduction durations, depending on the fill level, during the mixing/venting phase of the control cycle. Additionally, the automated control cycle was based on mixing alone for pressure reduction until the pressure versus time slope became positive, at which time the Joule-Thomson vent was opened. Testing was also conducted to evaluate thermodynamic venting without the mixer operating, first with liquid then with vapor at the recirculation line inlet. Although ullage stratification was present, the ullage pressure was successfully controlled without the mixer operating. Thus, if vapor surrounded the pump inlet in a reduced gravity situation, the ullage pressure can still be controlled by venting through the TVS Joule Thomson valve and heat exchanger. It was evident that the spray bar configuration, which extends almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the mixer operating. Details regarding the test setup and procedures are presented in the paper. 1

  5. Use of Interrupted Helium Flow in the Analysis of Vapor Samples with Flowing Atmospheric-Pressure Afterglow-Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Storey, Andrew P.; Zeiri, Offer M.; Ray, Steven J.; Hieftje, Gary M.

    2017-02-01

    The flowing atmospheric-pressure afterglow (FAPA) source was used for the mass-spectrometric analysis of vapor samples introduced between the source and mass spectrometer inlet. Through interrupted operation of the plasma-supporting helium flow, helium consumption is greatly reduced and dynamic gas behavior occurs that was characterized by schlieren imaging. Moreover, mass spectra acquired immediately after the onset of helium flow exhibit a signal spike before declining and ultimately reaching a steady level. This initial signal appears to be due to greater interaction of sample vapor with the afterglow of the source when helium flow resumes. In part, the initial spike in signal can be attributed to a pooling of analyte vapor in the absence of helium flow from the source. Time-resolved schlieren imaging of the helium flow during on and off cycles provided insight into gas-flow patterns between the FAPA source and the MS inlet that were correlated with mass-spectral data.

  6. Innovative Method for Developing a Helium Pressurant Tank Suitable for the Upper Stage Flight Experiment

    NASA Technical Reports Server (NTRS)

    DeLay, Tom K.; Munafo, Paul (Technical Monitor)

    2001-01-01

    The AFRL USFE project is an experimental test bed for new propulsion technologies. It will utilize ambient temperature fuel and oxidizers (Kerosene and Hydrogen peroxide). The system is pressure fed, not pump fed, and will utilize a helium pressurant tank to drive the system. Mr. DeLay has developed a method for cost effectively producing a unique, large pressurant tank that is not commercially available. The pressure vessel is a layered composite structure with an electroformed metallic permeation barrier. The design/process is scalable and easily adaptable to different configurations with minimal cost in tooling development 1/3 scale tanks have already been fabricated and are scheduled for testing. The full-scale pressure vessel (50" diameter) design will be refined based on the performance of the sub-scale tank. The pressure vessels have been designed to operate at 6,000 psi. a PV/W of 1.92 million is anticipated.

  7. Investigation of atmospheric pressure glow microdischarge between flat cathode and needle anode in helium and argon

    NASA Astrophysics Data System (ADS)

    Astafiev, Alexander; Belyaev, Vladimir; Zamchii, Roman; Kudryavtsev, Anatoly; Stepanova, Olga; Chen, Zhaoquan

    2016-09-01

    DC atmospheric-pressure glow microdischarge was generated between a flat cathode and needle anode with a diameter of 100 μm in a special chamber with helium or argon. Dependences of discharge parameters on an interelectrode gap was investigated with an original experimental setup based on a movable arm on the hinge joint which allowed changing the gap with a step of 5 μm. The gap was varied from 5 to 700 μm. Discharge current was 1-21 mA. Such discharge cell has a very low interelectrode capacitance and provides increasing the stability of the discharge against arc formation (transition to RC oscillations mode) at low currents of 1 mA. A weak dependence of discharge voltage across the gap was revealed in helium at 100-250 μm between the electrodes (normal discharge). In contrast to this, glow microdischarge in argon has a descending current-voltage characteristic and unstable nature. The discharge voltage depending on the gap changes significantly slower than in helium. According to our estimations, the strength of electrical field of positive glow in argon is 5 times lower than in helium. Saint Petersburg State University (Grant No. 0.37.218.2016).

  8. A computational modeling study on the helium atmospheric pressure plasma needle discharge

    NASA Astrophysics Data System (ADS)

    Qian, Mu-Yang; Yang, Cong-Ying; Liu, San-Qiu; Wang, Zhen-Dong; Lv, Yan; Wang, De-Zhen

    2015-12-01

    A two-dimensional coupled model of neutral gas flow and plasma dynamics is employed to investigate the streamer dynamics in a helium plasma needle at atmospheric pressure. A parametric study of the streamer propagation as a function of needle tip curvature radius and helium gas flow rate is presented. The key chemical reactions at the He/air mixing layer which drive the streamer propagation are the direct ionization via collision with electrons, the Penning effect being not so crucial. With increasing the gas flow rate from 0.2 standard liter per minute (SLM) to 0.8 SLM, however, the emissions resulting from reactive oxygen and nitrogen species change from a solid circle to a hollow profile and the average streamer propagation velocity decreases. Air impurities (backdiffusion from ambient air) in the helium jet result in a significant increase in the streamer propagation velocity. Besides, with decreasing the tip curvature radiusfrom 200 μm to 100 μm, the electron avalanche process around the near-tip region is more pronounced. However, the spatially resolved plasma parameters distributions (electron, helium metastables, ground state atomic oxygen, etc.) remain almost the same, except that around the near-tip region where their peak values are more than doubled. Project supported partly by the National Natural Science Foundation of China (Grant No. 11465013), the Natural Science Foundation of Jiangxi Province, China (Grant No. 20151BAB212012), and in part by the International Science and Technology Cooperation Program of China (Grant No. 2015DFA61800).

  9. Helium atmospheric pressure plasma jets touching dielectric and metal surfaces

    NASA Astrophysics Data System (ADS)

    Norberg, Seth A.; Johnsen, Eric; Kushner, Mark J.

    2015-07-01

    Atmospheric pressure plasma jets (APPJs) are being investigated in the context plasma medicine and biotechnology applications, and surface functionalization. The composition of the surface being treated ranges from plastics, liquids, and biological tissue, to metals. The dielectric constant of these materials ranges from as low as 1.5 for plastics to near 80 for liquids, and essentially infinite for metals. The electrical properties of the surface are not independent variables as the permittivity of the material being treated has an effect on the dynamics of the incident APPJ. In this paper, results are discussed from a computational investigation of the interaction of an APPJ incident onto materials of varying permittivity, and their impact on the discharge dynamics of the plasma jet. The computer model used in this investigation solves Poisson's equation, transport equations for charged and neutral species, the electron energy equation, and the Navier-Stokes equations for the neutral gas flow. The APPJ is sustained in He/O2 = 99.8/0.2 flowing into humid air, and is directed onto dielectric surfaces in contact with ground with dielectric constants ranging from 2 to 80, and a grounded metal surface. Low values of relative permittivity encourage propagation of the electric field into the treated material and formation and propagation of a surface ionization wave. High values of relative permittivity promote the restrike of the ionization wave and the formation of a conduction channel between the plasma discharge and the treated surface. The distribution of space charge surrounding the APPJ is discussed.

  10. Pressure Relief Devices for High-Pressure Gaseous Storage Systems: Applicability to Hydrogen Technology

    SciTech Connect

    Kostival, A.; Rivkin, C.; Buttner, W.; Burgess, R.

    2013-11-01

    Pressure relief devices (PRDs) are viewed as essential safety measures for high-pressure gas storage and distribution systems. These devices are used to prevent the over-pressurization of gas storage vessels and distribution equipment, except in the application of certain toxic gases. PRDs play a critical role in the implementation of most high-pressure gas storage systems and anyone working with these devices should understand their function so they can be designed, installed, and maintained properly to prevent any potentially dangerous or fatal incidents. As such, the intention of this report is to introduce the reader to the function of the common types of PRDs currently used in industry. Since high-pressure hydrogen gas storage systems are being developed to support the growing hydrogen energy infrastructure, several recent failure incidents, specifically involving hydrogen, will be examined to demonstrate the results and possible mechanisms of a device failure. The applicable codes and standards, developed to minimize the risk of failure for PRDs, will also be reviewed. Finally, because PRDs are a critical component for the development of a successful hydrogen energy infrastructure, important considerations for pressure relief devices applied in a hydrogen gas environment will be explored.

  11. Helium atmospheric pressure plasma jets touching dielectric and metal surfaces

    SciTech Connect

    Norberg, Seth A. Johnsen, Eric; Kushner, Mark J.

    2015-07-07

    Atmospheric pressure plasma jets (APPJs) are being investigated in the context plasma medicine and biotechnology applications, and surface functionalization. The composition of the surface being treated ranges from plastics, liquids, and biological tissue, to metals. The dielectric constant of these materials ranges from as low as 1.5 for plastics to near 80 for liquids, and essentially infinite for metals. The electrical properties of the surface are not independent variables as the permittivity of the material being treated has an effect on the dynamics of the incident APPJ. In this paper, results are discussed from a computational investigation of the interaction of an APPJ incident onto materials of varying permittivity, and their impact on the discharge dynamics of the plasma jet. The computer model used in this investigation solves Poisson's equation, transport equations for charged and neutral species, the electron energy equation, and the Navier-Stokes equations for the neutral gas flow. The APPJ is sustained in He/O{sub 2} = 99.8/0.2 flowing into humid air, and is directed onto dielectric surfaces in contact with ground with dielectric constants ranging from 2 to 80, and a grounded metal surface. Low values of relative permittivity encourage propagation of the electric field into the treated material and formation and propagation of a surface ionization wave. High values of relative permittivity promote the restrike of the ionization wave and the formation of a conduction channel between the plasma discharge and the treated surface. The distribution of space charge surrounding the APPJ is discussed.

  12. Atmospheric pressure discharge plasma decomposition for gaseous air contaminants -- Trichlorotrifluoroethane and trichloroethylene

    SciTech Connect

    Oda, Tetsuji; Yamashita, Ryuichi; Takahashi, Tadashi; Masuda, Senichi

    1996-03-01

    The decomposition performance of gaseous environmental destructive contaminants in air by using atmospheric pressure discharged plasma including the surface discharge induced plasma chemical processing (SPCP) was examined. The main contaminants tested were chlorofluorocarbon (CFC-113) and trichloroethylene, typically. The discharge exciting frequency range studied was wide--50 Hz to 50 kHz. Results showed the low frequency discharge requires high voltage to inject high electric power in the gas and to decompose the contaminants. A Gas Chromatograph Mass Spectrometer was used to analyze discharge products of dense CFC-113 or trichloroethylene. Among the detected products were HCl, CClFO, and CHCl{sub 3}. Two different electrode configurations; the silent discharge (coaxial) electrode and the coil-electrode were also tested and compared to each other as a gas reactor.

  13. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media

    DOEpatents

    McLellan, Edward J.

    1983-01-01

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode (1) and cathode (2) to below breakdown voltage using a dc voltage source (3). An array of resistors (4) or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit (5) producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO.sub.2 laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  14. Numerical Modeling and Test Data Comparison of Propulsion Test Article Helium Pressurization System

    NASA Technical Reports Server (NTRS)

    Holt, Kimberly; Majumdar, Alok; Steadman, Todd; Hedayat, Ali; Fogle, Frank R. (Technical Monitor)

    2000-01-01

    A transient model of the propulsion test article (PTA) helium pressurization system was developed using the generalized fluid system simulation program (GFSSP). The model included pressurization lines from the facility interface to the engine purge interface and liquid oxygen (lox) and rocket propellant-1 (RP-1) tanks, the propellant tanks themselves including ullage space, and propellant feed lines to their respective pump interfaces. GFSSP's capability was extended to model a control valve to maintain ullage pressure within a specified limit and pressurization processes such as heat transfer between ullage gas, propellant, and the tank wall as well as conduction in the tank wall. The purpose of the model is to predict the flow system characteristics in the entire pressurization system during 80 sec of lower feed system priming, 420 sec of fuel and lox pump priming, and 150 sec of engine firing.

  15. Columnar discharge mode between parallel dielectric barrier electrodes in atmospheric pressure helium

    SciTech Connect

    Hao, Yanpeng; Zheng, Bin; Liu, Yaoge

    2014-01-15

    Using a fast-gated intensified charge-coupled device, end- and side-view photographs were taken of columnar discharge between parallel dielectric barrier electrodes in atmospheric pressure helium. Based on three-dimensional images generated from end-view photographs, the number of discharge columns increased, whereas the diameter of each column decreased as the applied voltage was increased. Side-view photographs indicate that columnar discharges exhibited a mode transition ranging from Townsend to glow discharges generated by the same discharge physics as atmospheric pressure glow discharge.

  16. Temperature- and pressure-dependent absorption cross sections of gaseous hydrocarbons at 3.39 µm

    NASA Astrophysics Data System (ADS)

    Klingbeil, A. E.; Jeffries, J. B.; Hanson, R. K.

    2006-07-01

    The pressure- and temperature-dependent absorption cross sections of several neat hydrocarbons and multi-component fuels are measured using a 3.39 µm helium-neon laser. Absorption cross section measurements are reported for methane, ethylene, propane, n-heptane, iso-octane, n-decane, n-dodecane, JP-10, gasoline and jet-A with an estimated uncertainty of less than 3.5%. The experimental conditions range from 298 to 673 K and from 500 to 2000 Torr with nitrogen as the bath gas. An apparatus is designed to facilitate these measurements, and specific care is taken to ensure the compositional accuracy of the hydrocarbon/N2 mixtures. The absorption cross sections of the smallest hydrocarbons, methane and ethylene, vary with temperature and pressure. The cross sections of larger hydrocarbons show negligible dependence on pressure and only a weak dependence on temperature. The reported data increase the range of conditions and the number of hydrocarbons for which cross section measurements are available at the HeNe laser wavelength.

  17. Benchmarking density functionals for hydrogen-helium mixtures with quantum Monte Carlo: Energetics, pressures, and forces

    DOE PAGES

    Clay, Raymond C.; Holzmann, Markus; Ceperley, David M.; ...

    2016-01-19

    An accurate understanding of the phase diagram of dense hydrogen and helium mixtures is a crucial component in the construction of accurate models of Jupiter, Saturn, and Jovian extrasolar planets. Though DFT based rst principles methods have the potential to provide the accuracy and computational e ciency required for this task, recent benchmarking in hydrogen has shown that achieving this accuracy requires a judicious choice of functional, and a quanti cation of the errors introduced. In this work, we present a quantum Monte Carlo based benchmarking study of a wide range of density functionals for use in hydrogen-helium mixtures atmore » thermodynamic conditions relevant for Jovian planets. Not only do we continue our program of benchmarking energetics and pressures, but we deploy QMC based force estimators and use them to gain insights into how well the local liquid structure is captured by di erent density functionals. We nd that TPSS, BLYP and vdW-DF are the most accurate functionals by most metrics, and that the enthalpy, energy, and pressure errors are very well behaved as a function of helium concentration. Beyond this, we highlight and analyze the major error trends and relative di erences exhibited by the major classes of functionals, and estimate the magnitudes of these e ects when possible.« less

  18. Benchmarking density functionals for hydrogen-helium mixtures with quantum Monte Carlo: Energetics, pressures, and forces

    SciTech Connect

    Clay, Raymond C.; Holzmann, Markus; Ceperley, David M.; Morales, Maguel A.

    2016-01-19

    An accurate understanding of the phase diagram of dense hydrogen and helium mixtures is a crucial component in the construction of accurate models of Jupiter, Saturn, and Jovian extrasolar planets. Though DFT based rst principles methods have the potential to provide the accuracy and computational e ciency required for this task, recent benchmarking in hydrogen has shown that achieving this accuracy requires a judicious choice of functional, and a quanti cation of the errors introduced. In this work, we present a quantum Monte Carlo based benchmarking study of a wide range of density functionals for use in hydrogen-helium mixtures at thermodynamic conditions relevant for Jovian planets. Not only do we continue our program of benchmarking energetics and pressures, but we deploy QMC based force estimators and use them to gain insights into how well the local liquid structure is captured by di erent density functionals. We nd that TPSS, BLYP and vdW-DF are the most accurate functionals by most metrics, and that the enthalpy, energy, and pressure errors are very well behaved as a function of helium concentration. Beyond this, we highlight and analyze the major error trends and relative di erences exhibited by the major classes of functionals, and estimate the magnitudes of these e ects when possible.

  19. Simplified Methodology to Estimate the Maximum Liquid Helium (LHe) Cryostat Pressure from a Vacuum Jacket Failure

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Richards, W. Lance

    2015-01-01

    The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared astronomical observation experiments. These experiments carry sensors cooled to liquid helium temperatures. The liquid helium supply is contained in large (i.e., 10 liters or more) vacuum-insulated dewars. Should the dewar vacuum insulation fail, the inrushing air will condense and freeze on the dewar wall, resulting in a large heat flux on the dewar's contents. The heat flux results in a rise in pressure and the actuation of the dewar pressure relief system. A previous NASA Engineering and Safety Center (NESC) assessment provided recommendations for the wall heat flux that would be expected from a loss of vacuum and detailed an appropriate method to use in calculating the maximum pressure that would occur in a loss of vacuum event. This method involved building a detailed supercritical helium compressible flow thermal/fluid model of the vent stack and exercising the model over the appropriate range of parameters. The experimenters designing science instruments for SOFIA are not experts in compressible supercritical flows and do not generally have access to the thermal/fluid modeling packages that are required to build detailed models of the vent stacks. Therefore, the SOFIA Program engaged the NESC to develop a simplified methodology to estimate the maximum pressure in a liquid helium dewar after the loss of vacuum insulation. The method would allow the university-based science instrument development teams to conservatively determine the cryostat's vent neck sizing during preliminary design of new SOFIA Science Instruments. This report details the development of the simplified method, the method itself, and the limits of its applicability. The simplified methodology provides an estimate of the dewar pressure after a loss of vacuum insulation that can be used for the initial design of the liquid helium dewar vent stacks. However, since it is not an exact

  20. Modeling the chemical kinetics of high-pressure glow discharges in mixtures of helium with real air

    NASA Astrophysics Data System (ADS)

    Stalder, K. R.; Vidmar, R. J.; Nersisyan, G.; Graham, W. G.

    2006-05-01

    Atmospheric and near-atmospheric pressure glow discharges generated in both pure helium and helium-air mixtures have been studied using a plasma chemistry code originally developed for simulations of electron-beam-produced air plasmas. Comparisons are made with experimental data obtained from high-pressure glow discharges in helium-air mixtures developed by applying sinusoidal voltage wave forms between two parallel planar metallic electrodes covered by glass plates, with frequencies ranging from 10 to 50 kHz and electric field strengths up to 5 kV/cm. The code simulates the plasma chemistry following periodic pulsations of ionization in prescribed E/N environments. Many of the rate constants depend on gas temperature, electron temperature, and E/N. In helium plasmas with small amounts (~850 ppm) of air added, rapid conversion of atomic helium ions to molecular helium ions dominate the positive ion kinetics and these species are strongly modulated while the radical species are not. The charged and neutral species concentrations at atmospheric pressure with air impurity levels up to 10 000 ppm are predicted. The negative ion densities are very small but increase as the air impurity level is raised, which indicates that in helium-based systems operated in open air the concentration of negative ions would be significant. If water vapor at typical humidity levels is present as one of the impurities, hydrated cluster ions eventually comprise a significant fraction of the charged species.

  1. Measurements on Melting Pressure, Metastable Solid Phases, and Molar Volume of Univariant Saturated Helium Mixture

    NASA Astrophysics Data System (ADS)

    Rysti, J.; Manninen, M. S.; Tuoriniemi, J.

    2014-06-01

    A concentration-saturated helium mixture at the melting pressure consists of two liquid phases and one or two solid phases. The equilibrium system is univariant, whose properties depend uniquely on temperature. Four coexisting phases can exist on singular points, which are called quadruple points. As a univariant system, the melting pressure could be used as a thermometric standard. It would provide some advantages compared to the current reference, namely pure He, especially at the lowest temperatures below 1 mK. We have extended the melting pressure measurements of the concentration-saturated helium mixture from 10 to 460 mK. The density of the dilute liquid phase was also recorded. The effect of the equilibrium crystal structure changing from hcp to bcc was clearly seen at mK at the melting pressure MPa. We observed the existence of metastable solid phases around this point. No evidence was found for the presence of another, disputed, quadruple point at around 400 mK. The experimental results agree well with our previous calculations at low temperatures, but deviate above 200 mK.

  2. Helium:oxygen versus air:oxygen noninvasive positive-pressure ventilation in patients exposed to sulfur mustard.

    PubMed

    Ghanei, Mostafa; Rajaeinejad, Mohsen; Motiei-Langroudi, Rouzbeh; Alaeddini, Farshid; Aslani, Jafar

    2011-01-01

    Exposure to sulfur mustard (SM) causes a variety of respiratory symptoms, such as chronic bronchitis and constrictive bronchiolitis. This study assessed the effectiveness of noninvasive positive-pressure ventilation, adjunct with 79:21 helium:oxygen instead of 79:21 air:oxygen, in 24 patients with a previous exposure to SM presenting with acute respiratory failure. Both air:oxygen and helium:oxygen significantly decreased systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse rate, respiratory rate, dyspnea, and increased oxygen saturation (P values: .007, .029, .002, <.001, <.001, <.001, and .002 for air:oxygen, respectively, and <.001, .020, .001, <.001, <.001, <.001, and .002, for helium:oxygen, respectively). Moreover, helium:oxygen more potently improved systolic pressure, mean arterial pressure, pulse rate, respiratory rate, and dyspnea (P values: .012, .048, <.001, <.001, and .012, respectively). The results of our study support the benefit of using helium:oxygen adjunct with noninvasive positive-pressure ventilation in patients exposed to SM with acute respiratory decompensation.

  3. Numerical study of the interaction of a helium atmospheric pressure plasma jet with a dielectric material

    NASA Astrophysics Data System (ADS)

    Wang, Lijun; Zheng, Yashuang; Jia, Shenli

    2016-10-01

    This is a computational modeling study of a cold atmospheric pressure helium plasma jet impinging on a dielectric surface placed normal to the jet axis. This study provides insights into the propagation mechanism of the plasma jet, the electrical properties, and the total accumulated charge density at the dielectric surface. For the radial streamer propagation along the dielectric surface, Penning ionization and the electron impact ionization of helium atoms are the major ionization reactions in the streamer head, while Penning ionization is the only dominant contributor along the streamer body. In addition, the plasma bullet velocity along the dielectric surface is 10-100 times lower than that in the plasma column. Increasing tube radius or helium flow rate lowers air entrainment in the plasma jet, leading to a decrease of the radial electric field and the accumulated charge density at the dielectric surface. Furthermore, the tube radius has weaker influence on the plasma properties as tube radius increases. For a target dielectric with lower relative permittivity, a higher radial electric field penetrates into the material, and the surface ionization wave along the dielectric surface extends farther. Higher relative permittivity of the treated dielectric results in more charging at the dielectric surface and more electron density in the plasma column.

  4. High pressure liquid and gaseous oxygen impact sensitivity evaluation of materials for use at Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Bryan, C. J.

    1976-01-01

    The sensitivity of materials in contact with gaseous oxygen (GOX) or liquid oxygen (LOX) was examined. Specifically, the reactivity of materials when in contact with GOX or LOX if subjected to such stimuli as mechanical impact, adiabatic compression (pneumatic impact), or an electrical discharge in the form of a spark were examined. Generally, materials are more sensitive in gaseous oxygen than in liquid oxygen and impact sensitivity is known to increase with increasing pressure. Materials presently being used or considered for use in oxygen systems at KSC were evaluated. Results are given in tabular form.

  5. Development of miniaturized, spectroscopically assisted Penning gauges for fractional helium and hydrogen neutral pressure measurements

    NASA Astrophysics Data System (ADS)

    Flesch, K.; Kremeyer, T.; Schmitz, O.; Soukhanovskii, V.; Wenzel, U.

    2016-11-01

    Direct measurements of the helium (He) fractional neutral pressure in the neutral gas around fusion devices is challenging because of the small mass difference between the abundant D2 molecules and the He ash which will be produced by deuterium-tritium fusion. To study He exhaust, an in situ Penning gauge system is being developed at UW-Madison that is optimized for good pressure and high spectroscopic sensitivity. Three different anode geometries have been studied regarding their vacuum electrostatic fields, light output, and ion current. The light output of the two new anode configurations are at least one order of magnitude above the currently available designs, hence improving the spectroscopic sensitivity at similar total neutral pressure resolution.

  6. SHOOT flowmeter and pressure transducers. [for Superfluid Helium On-Orbit Transfer system

    NASA Technical Reports Server (NTRS)

    Kashani, A.; Wilcox, R. A.; Spivak, A. L.; Daney, D. E.; Woodhouse, C. E.

    1990-01-01

    A venturi flowmeter has been designed and constructed for the Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The calibration results obtained from the SHOOT venturi demonstrate the ability of the flowmeter to meet the requirements of the SHOOT experiment. Flow rates as low as 20 cu dm/h and as high as 800 cu dm/h have been measured. Performances of the SHOOT differential and absolute pressure transducers, which have undergone calibration and vibration tests, are also included. Throughout the tests, the responses of the transducers remained linear and repeatable to within + or - 1 percent of the full scales of the transducers.

  7. Cold Helium Pressurization for Liquid Oxygen / Liquid Methane Propulsion Systems: Fully-Integrated Initial Hot-Fire Test Results

    NASA Technical Reports Server (NTRS)

    Morehead, R. L.; Atwell, M. J.; Melcher, J. C.; Hurlbert, E. A.

    2016-01-01

    A prototype cold helium active pressurization system was incorporated into an existing liquid oxygen (LOX) / liquid methane (LCH4) prototype planetary lander and hot-fire tested to collect vehicle-level performance data. Results from this hot-fire test series were used to validate integrated models of the vehicle helium and propulsion systems and demonstrate system effectiveness for a throttling lander. Pressurization systems vary greatly in complexity and efficiency between vehicles, so a pressurization performance metric was also developed as a means to compare different active pressurization schemes. This implementation of an active repress system is an initial sizing draft. Refined implementations will be tested in the future, improving the general knowledge base for a cryogenic lander-based cold helium system.

  8. Production of stable, non-thermal atmospheric pressure rf capacitive plasmas using gases other than helium or neon

    DOEpatents

    Park, Jaeyoung; Henins, Ivars

    2005-06-21

    The present invention enables the production of stable, steady state, non-thermal atmospheric pressure rf capacitive .alpha.-mode plasmas using gases other than helium and neon. In particular, the current invention generates and maintains stable, steady-state, non-thermal atmospheric pressure rf .alpha.-mode plasmas using pure argon or argon with reactive gas mixtures, pure oxygen or air. By replacing rare and expensive helium with more readily available gases, this invention makes it more economical to use atmospheric pressure rf .alpha.-mode plasmas for various materials processing applications.

  9. Helium pressures in RHIC vacuum cryostats and relief valve requirements from magnet cooling line failure

    SciTech Connect

    Liaw, C.J.; Than, Y.; Tuozzolo, J.

    2011-03-28

    A catastrophic failure of the RHIC magnet cooling lines, similar to the LHC superconducting bus failure incident, would pressurize the insulating vacuum in the magnet and transfer line cryostats. Insufficient relief valves on the cryostats could cause a structural failure. A SINDA/FLUINT{reg_sign} model, which simulated the 4.5K/4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the vacuum cryostat and discharging via the reliefs into the RHIC tunnel, had been developed to calculate the helium pressure inside the cryostat. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces were included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Existing relief valve sizes were reviewed to make sure that the maximum stresses, caused by the calculated maximum pressures inside the cryostats, did not exceed the allowable stresses, based on the ASME Code B31.3 and ANSYS results. The conclusions are as follows: (1) The S/F simulation results show that the highest internal pressure in the cryostats, due to the magnet line failure, is {approx}37 psig (255115 Pa); (2) Based on the simulation, the temperature on the cryostat chamber, INJ Q8-Q9, could drop to 228 K, which is lower than the material minimum design temperature allowed by the Code; (3) Based on the ASME Code and ANSYS results, the reliefs on all the cryostats inside the RHIC tunnel are adequate to protect the vacuum chambers when the magnet cooling lines fail; and (4) In addition to the pressure loading, the thermal deformations, due to the temperature decrease on the cryostat chambers, could also cause a high stress on the chamber, if not properly supported.

  10. Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution

    SciTech Connect

    Laroche, G.; Vallade, J.; Bazinette, R.; Hernandez, E.; Hernandez, G.; Massines, F.; Nijnatten, P. van

    2012-10-15

    This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm Multiplication-Sign 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45 Degree-Sign beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

  11. Variable Temperature Setup for Scanning Electron Microscopy in Liquids and Atmospheric Pressure Gaseous Environments

    NASA Astrophysics Data System (ADS)

    Al-Asadi, Ahmed; Zhang, Jie; Li, Jianbo; Denault, Lauraine; Potyrailo, Radislav; Kolmakov, Andrei

    2014-03-01

    A thermoelectric cooling / heating setup for commercial Quantomix QX WETSEM scanning electron microscopy environmental cells was designed and tested. This addition allows extending ambient pressure in situ studies to be conducted in a wide temperature range both in liquid and gaseous environments. Instead of cooling/heating the entire body of QX-WETCELL, ultrathin polyimide electron transparent membrane window supported by metal mesh on the top of the cell has been used as an agent for heat transfer to/ from the Pelltier element. A butterfly wing of Morph sulkowskyi has been used as a model object in the QX-WETCELL's chamber due to its unique micro/nanostructure and peculiar wettability behavior. The dynamics of the water desorption, condensation and freezing processes were observed complementary using both optical microscopy and Scanning Electron Microscopy in vivo. The observations revel that the initial droplet formation were most likely taking place on the top of the wing ridges due to the waxy component of its surface. In addition, The SEM observation showed that the high intensity electron beam can heat the butterfly wing locally delaying the water condensation and freezing processes.

  12. Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution.

    PubMed

    Laroche, G; Vallade, J; Bazinette, R; van Nijnatten, P; Hernandez, E; Hernandez, G; Massines, F

    2012-10-01

    This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm × 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45° beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

  13. The role of helium metastable states in radio-frequency driven helium-oxygen atmospheric pressure plasma jets: measurement and numerical simulation

    NASA Astrophysics Data System (ADS)

    Niemi, K.; Waskoenig, J.; Sadeghi, N.; Gans, T.; O'Connell, D.

    2011-10-01

    Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium-oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the homogeneous-glow-like α-mode plasma with oxygen admixtures up to 1% were investigated. The results are compared with a one-dimensional numerical simulation, which includes a semi-kinetical treatment of the pronounced electron dynamics and the complex plasma chemistry (in total 20 species and 184 reactions). Very good agreement between measurement and simulation is found. The main formation mechanisms for metastable helium atoms are identified and analyzed, including their pronounced spatio-temporal dynamics. Penning ionization through helium metastables is found to be significant for plasma sustainment, while it is revealed that helium metastables are not an important energy carrying species into the jet effluent and therefore will not play a direct role in remote surface treatments.

  14. Metastable densities in rf-driven atmospheric pressure microplasma jets in argon and helium

    NASA Astrophysics Data System (ADS)

    Boeke, Marc; Spiekermeier, Stefan; Winter, Joerg

    2016-09-01

    Rf-driven atmospheric pressure microplasma jets (μ-APPJ) are usually operated in the homogeneous glow mode (α-mode). At higher powers the glow discharge becomes unstable due to thermal instabilities and turns into a constricted γ-like discharge (constricted mode), which can damage the jet due to the significantly increased temperature in this operation mode. To prevent these instabilities, rf-driven μ-APPJs are predominantly operated in helium since it provides a better thermal conductivity than argon. However, since argon is much more cost-effective, it is worthwhile to achieve a stable operation of the μ-APPJ using argon as feed gas. Metastable atoms play an important role in the stability of atmospheric pressure discharges, since they pose an important source of electrons via stepwise ionization and penning ionization. To understand the basic processes that lead to the transition from α- to the constricted mode, helium and argon metastable densities have been determined in the μ-APPJ in different operation modes using tunable diode laser absorption spectroscopy (TDLAS). Supported by DFG within (FOR1123).

  15. Hydroxyl radical-PLIF measurements and accuracy investigation in high pressure gaseous hydrogen/gaseous oxygen combustion

    NASA Astrophysics Data System (ADS)

    Vaidyanathan, Aravind

    In-flow species concentration measurements in reacting flows at high pressures are needed both to improve the current understanding of the physical processes taking place and to validate predictive tools that are under development, for application to the design and optimization of a range of power plants from diesel to rocket engines. To date, non intrusive measurements have been based on calibrations determined from assumptions that were not sufficiently quantified to provide a clear understanding of the range of uncertainty associated with these measurements. The purpose of this work is to quantify the uncertainties associated with OH measurement in a oxygen-hydrogen system produced by a shear, coaxial injector typical of those used in rocket engines. Planar OH distributions are obtained providing instantaneous and averaged distribution that are required for both LES and RANS codes currently under development. This study has evaluated the uncertainties associated with OH measurement at 10, 27, 37 and 53 bar respectively. The total rms error for OH-PLIF measurements from eighteen different parameters was quantified and found as 21.9, 22.8, 22.5, and 22.9% at 10, 27, 37 and 53 bar respectively. These results are used by collaborators at Georgia Institute of Technology (LES), Pennsylvania State University (LES), University of Michigan (RANS) and NASA Marshall (RANS).

  16. Use of a torsional pendulum as a high-pressure gage and determination of viscosity of helium gas at high pressures

    NASA Technical Reports Server (NTRS)

    Maisel, J. E.; Webeler, R. W. H.; Grimes, H. H.

    1973-01-01

    Three torsional crystal parameters were examined for suitability in sensing pressure in gases up to 131 million newtons per square meter. The best parameters were found to be the change in crystal decrement at resonance and the change in crystal electrical resistance at resonance. The change in crystal resonant frequency did not appear to be a reliable pressure measuring parameter. Pure argon and pure helium gases were studied for use as working fluids. Helium functioned better over a wider pressure range. Calibration of the gage also provided a measure of the viscosity-density product of the gas as a function of pressure. These data, together with known extrapolated density data, permitted the determination of the viscosity of helium to 131 million N/square meter.

  17. Numerical Modeling of Helium Pressurization System of Propulsion Test Article (PTA)

    NASA Technical Reports Server (NTRS)

    Steadman, Todd; Majumdar, Alok; Holt, Kimberly

    2001-01-01

    A transient model of the Propulsion Test Article (PTA) Helium Pressurization System was developed using the Generalized Fluid System Simulation Program (GFSSP). The model included feed lines from the facility interface to the engine purge interface and Liquid Oxygen (LOX) and Rocket Propellant 1 (RP-1) tanks, the propellant tanks themselves including ullage space and propellant feed lines to their respective pump interfaces. GFSSP's capability was extended to model a control valve to maintain ullage pressure within a specified limit and pressurization processes such as heat transfer between ullage gas, propellant and the tank wall. The purpose of the model is to predict the flow system characteristics in the entire pressurization system during 80 seconds of lower feed system priming, 420 seconds of fuel and LOX pump priming and 150 seconds of engine firing. Subsequent to the work presented here, the PTA model has been updated to include the LOX and RP-1 pumps, while the pressurization option itself has been modified to include the effects of mass transfer. This updated model will be compared with PTA test data as it becomes available.

  18. Temporally, spatially, and spectrally resolved barrier discharge produced in trapped helium gas at atmospheric pressure

    SciTech Connect

    Chiper, Alina Silvia; Popa, Gheorghe

    2013-06-07

    Experimental study was made on induced effects by trapped helium gas in the pulsed positive dielectric barrier discharge (DBD) operating in symmetrical electrode configuration at atmospheric pressure. Using fast photography technique and electrical measurements, the differences in the discharge regimes between the stationary and the flowing helium are investigated. It was shown experimentally that the trapped gas atmosphere (TGA) has notable impact on the barrier discharge regime compared with the influence of the flowing gas atmosphere. According to our experimental results, the DBD discharge produced in trapped helium gas can be categorized as a multi-glow (pseudo-glow) discharge, each discharge working in the sub-normal glow regime. This conclusion is made by considering the duration of current pulse (few {mu}s), their maximum values (tens of mA), the presence of negative slope on the voltage-current characteristic, and the spatio-temporal evolution of the most representative excited species in the discharge gap. The paper focuses on the space-time distribution of the active species with a view to better understand the pseudo-glow discharge mechanism. The physical basis for these effects was suggested. A transition to filamentary discharge is suppressed in TGA mode due to the formation of supplementary source of seed electrons by surface processes (by desorption of electrons due to vibrationally excited nitrogen molecules, originated from barriers surfaces) rather than volume processes (by enhanced Penning ionisation). Finally, we show that the pseudo-glow discharge can be generated by working gas trapping only; maintaining unchanged all the electrical and constructive parameters.

  19. Evaluation of neonatal membrane oxygenators with respect to gaseous microemboli capture and transmembrane pressure gradients.

    PubMed

    Qiu, Feng; Guan, Yulong; Su, Xiaowei; Kunselman, Allen; Undar, Akif

    2010-11-01

    A series of studies performed at our center demonstrates that gaseous microemboli (GME) remain a challenge in cardiac surgical procedures. Evaluation of novel oxygenators must address hemodynamic parameters and microemboli capture capability. The objective of this study is to compare two neonatal membrane oxygenators, the Quadrox-i (MAQUET Cardiopulmonary AG, Hirrlingen, Germany) and the Capiox RX05 (Terumo Corporation, Tokyo, Japan), with respect to GME capture and hemodynamic energy delivery. The experimental circuit included a Maquet HL-20 heart-lung machine, a Heater-Cooler Unit HCU 30 (MAQUET Cardiopulmonary AG), a membrane oxygenator (Quadrox-i Neonatal or Capiox RX05), and ¼-inch tubing from the COBE Heart/Lung Perfusion Pack (COBE Cardiovascular, Inc., Arvada, CO, USA). A Capiox cardiotomy reservoir CX*CR10NX (Terumo Corporation) acted as a pseudopatient. The circuit was primed with human packed red blood cells and lactated Ringer's solution and de-aired according to clinical priming procedure. Heparin (5000IU) was added into the circuit. The total volume was 400mL and hematocrit was 30%. Pump flow rate was maintained at 500 or 1000mL/min under both pulsatile and nonpulsatile modes. All trials were conducted under 100mm Hg of circuit pressure at normothermia (35°C). In each trial, bolus air (0.5mL) was injected into the circuit at the prepump site over 5s. Total emboli counts and total emboli volume were significantly reduced by the Quadrox-i Neonatal membrane oxygenator compared to the Capiox RX05 membrane oxygenator. Classification and quantification of GME detected at the postoxygenator site at two different flow rates indicated that the Quadrox-i Neonatal captures the majority of microemboli larger than 40µm in diameter. The Quadrox-i Neonatal membrane oxygenator had a higher transmembrane pressure drop at 500mL/min, whereas it had a lower pressure drop at 1000mL/min compared to the Capiox Baby RX05 oxygenator. Additionally, the Quadrox-i Neonatal

  20. The Gaseous Explosive Reaction at Constant Pressure : Further Data on the Effect of Inert Gases

    NASA Technical Reports Server (NTRS)

    Stevens, F W

    1932-01-01

    An investigation of gaseous explosive reactions is discussed in this report. Measurements were taken to calculate the maximum flame temperature attained and making correlations with existing thermal data on this reaction.

  1. Probe measurements of electron energy spectrum in Helium/air micro-plasma at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Demidov, V. I.; Adams, S. F.; Miles, J. A.; Koepke, M. E.; Kurlyandskaya, I. P.; Hensley, A. L.; Tolson, B. A.

    2016-09-01

    It is experimentally demonstrated that a wall probe may be a useful instrument for interpretation of electron energy spectrum in a micro-plasma with a nonlocal electron distribution function at atmospheric pressure. Two micro-plasma devices were fabricated with three layers of molybdenum metal foils with thickness of 0.1 mm separated by two sheets of mica insulation with thickness of 0.11 mm. In one device a hole with the diameter of 0.2 mm formed a cylindrical discharge cavity that passed through the entire five layers. In the second device the hole has the diameter of 0.065 mm. In both devices the inner molybdenum layer formed a wall probe, while the outer layers of molybdenum served as the hollow cathode and anode. The discharge was open into air with flow of helium gas. It is found that the wall probe I-V trace is sensitive to the presence of helium metastable atoms. The first derivative of the probe current with respect to the probe potential shows peaks revealing fast electrons at specific energies arising due to plasma chemical reactions. The devices may be applicable for developing analytical sensors for extreme environments, including high radiation and vibration levels and high temperatures. This work was performed while VID held a NRC Research Associateship Award at AFRL.

  2. Study of spatial distributions of highly ionized nonequilibrium helium plasma at atmospheric pressures

    NASA Astrophysics Data System (ADS)

    Chinnov, V. F.; Kavyrshin, D. I.; Ageev, A. G.; Korshunov, O. V.; Sargsyan, M. A.; Efimov, A. V.

    2016-11-01

    Experimental study of helium plasma in the state of quasistationary heating under atmospheric pressure was made. The plasma state is shown to fail to be described by Saha- Boltzmann approximation at high ionization levels α i = 0.5-0.9, temperatures 2.5-4.0 eV and electron concentrations about 1017 cm-3. The deviation from the equilibrium state of the plasma is caused by lack of spatial uniformity due to charged particles loss by ambipolar diffusion. In order to thoroughly study the temporal changes of plasma radiation characteristics, spectroscopic analysis was carried out with DFS-452 spectrometer and high-speed CMOS camera Andor iStar attached to its output. The system yields the spatial resolution of 30-50 μm and temporal resolution of 5-50 μs. Electron concentration ne was measured from the half-width of the local Hei spectrum line contours having dominant quadruple Stark effect with well-known constants. In order to determine the temperature of heavy particles, Doppler component of HeI line triplet at 1083 nm was studied. The temporal evolution of the following important characteristics has been determined for helium plasma during pulsed heating: current power, intensities of a number of HeI and HeII spectral lines, electron temperatures and concentrations.

  3. Electric field development in γ-mode radiofrequency atmospheric pressure glow discharge in helium

    NASA Astrophysics Data System (ADS)

    Navrátil, Zdeněk; Josepson, Raavo; Cvetanović, Nikola; Obradović, Bratislav; Dvořák, Pavel

    2016-06-01

    Time development of electric field strength during radio-frequency sheath formation was measured using Stark polarization spectroscopy in a helium γ-mode radio-frequency (RF, 13.56 MHz) atmospheric pressure glow discharge at high current density (3 A cm-2). A method of time-correlated single photon counting was applied to record the temporal development of spectral profile of He I 492.2 nm line with a sub-nanosecond temporal resolution. By fitting the measured profile of the line with a combination of pseudo-Voigt profiles for forbidden (2 1P-4 1F) and allowed (2 1P-4 1D) helium lines, instantaneous electric fields up to 32 kV cm-1 were measured in the RF sheath. The measured electric field is in agreement with the spatially averaged value of 40 kV cm-1 estimated from homogeneous charge density RF sheath model. The observed rectangular waveform of the electric field time development is attributed to increased sheath conductivity by the strong electron avalanches occurring in the γ-mode sheath at high current densities.

  4. Correlation of Helium Solubility in Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

    A correlation has been developed for the equilibrium mole fraction of soluble gaseous helium in liquid nitrogen as a function of temperature and pressure. Experimental solubility data was compiled and provided by National Institute of Standards and Technology (NIST). Data from six sources was used to develop a correlation within the range of 0.5 to 9.9 MPa and 72.0 to 119.6 K. The relative standard deviation of the correlation is 6.9 percent.

  5. Heat flow and arc efficiency at high pressures in argon and helium tungsten arcs

    SciTech Connect

    Katsaounis, A. )

    1993-09-01

    For control of welding underwater robotic systems, the arc characteristics and the heat quotation in cathode, arc column and anode (weld) were measured in GTAW with argon and helium shielding gas using the calorimetric method. The measurements were performed mainly in a pressure chamber. The pressure, the current and the arc length were varied from 0.1-6.0 MPa, 50-300 A and 2-11 mm, respectively. It was observed that the welding voltage is strongly dependent on system pressure for both shielding gases and an explicit minimum voltage/current was obtained for the argon arc characteristics at approximately 100 A. Furthermore, the field strength and the heat emission from the arc column increased exponentially with the pressure. A simple relation was developed to predict heat emission from the arc column and, consequently, for the arc efficiency. In addition, a calculation model for engineering use was derived based on the Ellenbaas-Heller equation to calculate the-heat flux from the arc to the weld (for both gases).

  6. Use of Interrupted Helium Flow in the Analysis of Vapor Samples with Flowing Atmospheric-Pressure Afterglow-Mass Spectrometry.

    PubMed

    Storey, Andrew P; Zeiri, Offer M; Ray, Steven J; Hieftje, Gary M

    2017-02-01

    The flowing atmospheric-pressure afterglow (FAPA) source was used for the mass-spectrometric analysis of vapor samples introduced between the source and mass spectrometer inlet. Through interrupted operation of the plasma-supporting helium flow, helium consumption is greatly reduced and dynamic gas behavior occurs that was characterized by schlieren imaging. Moreover, mass spectra acquired immediately after the onset of helium flow exhibit a signal spike before declining and ultimately reaching a steady level. This initial signal appears to be due to greater interaction of sample vapor with the afterglow of the source when helium flow resumes. In part, the initial spike in signal can be attributed to a pooling of analyte vapor in the absence of helium flow from the source. Time-resolved schlieren imaging of the helium flow during on and off cycles provided insight into gas-flow patterns between the FAPA source and the MS inlet that were correlated with mass-spectral data. Graphical Abstract ᅟ.

  7. Helium-Recycling Plant

    NASA Technical Reports Server (NTRS)

    Cook, Joseph

    1996-01-01

    Proposed system recovers and stores helium gas for reuse. Maintains helium at 99.99-percent purity, preventing water vapor from atmosphere or lubricating oil from pumps from contaminating gas. System takes in gas at nearly constant low back pressure near atmospheric pressure; introduces little or no back pressure into source of helium. Concept also extended to recycling of other gases.

  8. Effects of the air pressure on the wave-packet dynamics of gaseous iodine molecules at room temperature

    NASA Astrophysics Data System (ADS)

    Fan, Rongwei; He, Ping; Chen, Deying; Xia, Yuanqin; Yu, Xin; Wang, Jialing; Jiang, Yugang

    2013-02-01

    Based on ultrafast laser pulses, time-resolved resonance enhancement coherent anti-Stokes Raman scattering (RE-CARS) is applied to investigate wave-packet dynamics in gaseous iodine. The effects of air pressure on the wave-packet dynamics of iodine molecules are studied at pressures ranging from 1.5 Torr to 750 Torr. The RE-CARS signals are recorded in a gas cell filled with a mixture of about 0.3 Torr iodine in air buffer gas at room temperature. The revivals and fractional revival structures in the wave-packet signal are found to gradually disappear with rising air pressure up to 750 Torr, and the decay behaviors of the excited B-state and ground X-state become faster with increasing air pressure, which is due to the collision effects of the molecules and the growing complexity of the spectra at high pressures.

  9. Extending helium partial pressure measurement technology to JET DTE2 and ITER

    NASA Astrophysics Data System (ADS)

    Klepper, C. C.; Biewer, T. M.; Kruezi, U.; Vartanian, S.; Douai, D.; Hillis, D. L.; Marcus, C.

    2016-11-01

    The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

  10. Extending Helium Partial Pressure Measurement Technology to JET DTE2 and ITER

    SciTech Connect

    Klepper, C Christopher; Biewer, Theodore M; Douai, D.; Hillis, Donald Lee; Marcus, Chris; Kruezi, Uron

    2016-01-01

    The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE-2) and for ITER.

  11. Correlation between helium atmospheric pressure plasma jet (APPJ) variables and plasma induced DNA damage

    NASA Astrophysics Data System (ADS)

    Adhikari, Ek R.; Ptasinska, Sylwia

    2016-09-01

    A helium atmospheric pressure plasma jet (APPJ) source with a dielectric capillary and two tubular electrodes was used to induce damage in aqueous plasmid DNA. The fraction of different types of DNA damage (i.e., intact or undamaged, double strand breaks (DSBs), and single strand breaks (SSBs)) that occurred as the result of plasma irradiation was quantified through analysis of agarose gel electrophoresis images. The total DNA damage increased with an increase in both flow rate and duration of irradiation, but decreased with an increase in distance between the APPJ and sample. The average power of the plasma was calculated and the length of APPJ was measured for various flow rates and voltages applied. The possible effects of plasma power and reactive species on DNA damage are discussed.

  12. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-10-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  13. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet.

    PubMed

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T H; Kang, Tae-Hong

    2014-10-16

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

  14. Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet

    PubMed Central

    Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

    2014-01-01

    The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

  15. Measurement of O and OH radical produced by an atmospheric-pressure helium plasma jet nearby rat skin

    NASA Astrophysics Data System (ADS)

    Yonemori, Seiya; Ono, Ryo

    2013-09-01

    Atmospheric-pressure helium plasma jet is getting much attention because it enables many kinds of plasma applications including biomedical application such as sterilization and cancer treatment. In biomedical plasma applications, it is though that active species like ions and radicals play important role. Especially, OH radical and O atom is very chemically reactive that they are deemed as major factors in cancer treatment. In this study, O and OH density distribution and its temporal behavior nearby rat skin were measured to demonstrate actual application. Plasma discharge was under AC10 kVp-p, 10 kHz with 1.5 slm (standard litter per minute) of helium gas flow. OH density was around 1 ppm and O atom density was around 10 ppm at maximum. We also measured time-evolution of OH and O atom density. Both OH and O density was almost constant between discharge pulses because lifetime of active species could be prolonged in helium. And density distribution of both species varied depending on helium flow rate and water concentration on the surface; on rat skin or on the grass surface. Those results suggest the production mechanisms and provision mechanisms of O atom and OH radical by an atmospheric-pressure helium plasma jet. This work is partially supported by the Grant-in-Aid for Science Research by the Ministry of Education, Culture, Sport, Science and Technology.

  16. Hydrogen Absorption into Austenitic Stainless Steels Under High-Pressure Gaseous Hydrogen and Cathodic Charge in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Enomoto, Masato; Cheng, Lin; Mizuno, Hiroyuki; Watanabe, Yoshinori; Omura, Tomohiko; Sakai, Jun'ichi; Yokoyama, Ken'ichi; Suzuki, Hiroshi; Okuma, Ryuji

    2014-12-01

    Type 316L and Type 304 austenitic stainless steels, both deformed and non-deformed, were hydrogen charged cathodically in an aqueous solution as well as by exposure to high-pressure gaseous hydrogen in an attempt to identify suitable conditions of cathodic charge for simulating hydrogen absorption from gaseous hydrogen environments. Thermal desorption analysis (TDA) was conducted, and the amount of absorbed hydrogen and the spectrum shape were compared between the two charging methods. Simulations were performed by means of the McNabb-Foster model to analyze the spectrum shape and peak temperature, and understand the effects of deformation on the spectra. It was revealed that the spectrum shape and peak temperature were dependent directly upon the initial distribution of hydrogen within the specimen, which varied widely according to the hydrogen charge condition. Deformation also had a marked effect on the amount of absorbed hydrogen in Type 304 steel due to the strain-induced martensitic transformation.

  17. CO2-helium and CO2-neon mixtures at high pressures.

    PubMed

    Mallick, B; Ninet, S; Le Marchand, G; Munsch, P; Datchi, F

    2013-01-28

    The properties of mixtures of carbon dioxide with helium or neon have been investigated as a function of CO(2) concentration and pressure up to 30 GPa at room temperature. The binary phase diagrams of these mixtures are determined over the full range of CO(2) concentrations using visual observations and Raman scattering measurements. Both diagrams are of eutectic type, with a fluid-fluid miscibility gap for CO(2) concentrations in the range [5, 75] mol. % for He and [8, 55] mol. % for Ne, and a complete separation between the two components in the solid phase. The absence of alloys or stoichiometric compounds for these two binary systems is consistent with the Hume-Rothery rules of hard sphere mixtures. The Raman spectra and x-ray diffraction patterns of solid CO(2) embedded in He or Ne for various initial concentrations have been measured up to 30 GPa and 12 GPa, respectively. The frequencies of the Raman modes and the volume of solid phase I are identical, within error bars, to those reported for 100% CO(2) samples, thus confirming the total immiscibility of CO(2) with He and Ne in the solid phase. These results demonstrate the possibility to perform high-pressure experiments on solid CO(2) under (quasi-)hydrostatic conditions using He or Ne as pressure transmitting medium.

  18. CO2-helium and CO2-neon mixtures at high pressures

    NASA Astrophysics Data System (ADS)

    Mallick, B.; Ninet, S.; Le Marchand, G.; Munsch, P.; Datchi, F.

    2013-01-01

    The properties of mixtures of carbon dioxide with helium or neon have been investigated as a function of CO2 concentration and pressure up to 30 GPa at room temperature. The binary phase diagrams of these mixtures are determined over the full range of CO2 concentrations using visual observations and Raman scattering measurements. Both diagrams are of eutectic type, with a fluid-fluid miscibility gap for CO2 concentrations in the range [5, 75] mol. % for He and [8, 55] mol. % for Ne, and a complete separation between the two components in the solid phase. The absence of alloys or stoichiometric compounds for these two binary systems is consistent with the Hume-Rothery rules of hard sphere mixtures. The Raman spectra and x-ray diffraction patterns of solid CO2 embedded in He or Ne for various initial concentrations have been measured up to 30 GPa and 12 GPa, respectively. The frequencies of the Raman modes and the volume of solid phase I are identical, within error bars, to those reported for 100% CO2 samples, thus confirming the total immiscibility of CO2 with He and Ne in the solid phase. These results demonstrate the possibility to perform high-pressure experiments on solid CO2 under (quasi-)hydrostatic conditions using He or Ne as pressure transmitting medium.

  19. Calculation of releases of radioactive materials in gaseous and liquid effluents from pressurized water reactors (PWR-GALE Code). Revision 1

    SciTech Connect

    Chandrasekaran, T.; Lee, J.Y.; Willis, C.A.

    1985-04-01

    This report revises the original issuance of NUREG-0017, ''Calculation of Releases of Radioactive Materials in Gaseous and Liquid Effluents from Pressurized Water Reactors (PWR-GALE-Code)'' (April 1976), to incorporate more recent operating data now available as well as the results of a number of in-plant measurement programs at operating pressurized water reactors. The PWR-GALE Code is a computerized mathematical model for calculating the releases of radioactive material in gaseous and liquid effluents (i.e., the gaseous and liquid source terms). The US Nuclear Regulatory Commission uses the PWR-GALE Code to determine conformance with the requirements of Appendix I to 10 CFR Part 50.

  20. Thermophysical properties of Helium-4 from 0.8 to 1500 K with pressures to 2000 MPa

    NASA Technical Reports Server (NTRS)

    Arp, Vincent D.; Mccarty, Robert D.

    1989-01-01

    Tabular summary data of the thermophysical properties of fluid helium are given for temperatures from 0.8 to 1500 K, with pressures to 2000 MPa between 75 and 300 K, or to 100 MPa outside of this temperature band. Properties include density, specific heats, enthalpy, entropy, internal energy, sound velocity, expansivity, compressibility, thermal conductivity, and viscosity. The data are calculated from a computer program which is available from the National Institute of Standards and Technology. The computer program is based on carefully fitted state equations for both normal and superfluid helium.

  1. Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms

    SciTech Connect

    Deng, X. T.; Shi, J. J.; Kong, M. G.

    2007-04-01

    Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm{sup 2}. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.

  2. Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms

    NASA Astrophysics Data System (ADS)

    Deng, X. T.; Shi, J. J.; Kong, M. G.

    2007-04-01

    Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm2. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.

  3. Influence of dielectric materials on radial uniformity in non-equilibrium atmospheric pressure helium plasma

    NASA Astrophysics Data System (ADS)

    Oda, Akinori; Komori, Kyohei

    2015-09-01

    Non-equilibrium atmospheric pressure plasma has been utilized for various technological applications such as surface treatment, materials processing, bio-medical and bio-logical applications. For optimum control of the plasma for the above applications, numerous experimental and theoretical investigations on the plasma have been reported. Especially, controlling radial uniformity of the plasma are very important for utilizing materials processing. In this paper, an axially-symmetric three-dimensional fluid model, which is composed of the continuity equation for charged and neutral species, the Poisson equation, and the energy conservation equation for electrons, of non-equilibrium atmospheric pressure helium plasma has been developed. Then, influence of dielectric properties (e.g. relative permittivity, secondary electron emission coefficient, etc.) of dielectric materials on radial plasma uniformity (i.e. radial distributions of electron density, ion density, electric field in the plasma) was examined. This work was partly supported by KAKENHI (No. 26420247), and a ``Grant for Advanced Industrial Technology Development (No. 11B06004d)'' in 2011 from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

  4. Floating Pressure Conversion and Equipment Upgrades of Two 3.5kw, 20k, Helium Refrigerators

    NASA Technical Reports Server (NTRS)

    Homan, Jonathan; Linza, Robert; Garcia, Sam; Vargas, Gerardo; Lauterbach, John; Ganni, Venkatarao (Rao); Sidi-Yekhlef, Ahmed; Creel, Jonathan; Norton, Robert; Urbin, John; Howe, Don

    2008-01-01

    Two helium refrigerators, each rated for 3.5KW at 20K, are used at NASA s Johnson Space Center (JSC) in Building No. 32 to provide cryo-pumping within two large thermal-vacuum chambers. These refrigerators were originally commissioned in 1996. Equipment refurbishment and upgrades to the controls of these refrigerators were recently completed. This paper describes some of the mechanical and control issues that necessitated the equipment refurbishment and controls change-over. It will describe the modifications and the new process control which allows the refrigerators to take advantage of the Ganni Cycle "floating pressure" control technology. The upgrades -- the controls philosophy change-over to the floating pressure control technology and the newly refurbished equipment -- have greatly improved the performance, stability, and efficiency of these two refrigerators. The upgrades have also given the operators more information and details about the operational status of the main components (compressors, expanders etc.) of the refrigerators at all operating conditions (i.e.: at various loads in the vacuum chambers). Capabilities, configuration, and performance data pre, and post, upgrading will be presented.

  5. Influence of excitation frequency on helium metastable density in atmospheric pressure DBD

    NASA Astrophysics Data System (ADS)

    Boisvert, J.-S.; Sadeghi, N.; Margot, J.; Massines, F.

    2016-09-01

    Diffuse dielectric barrier discharges in atmospheric-pressure helium was sustained over a wide range of excitation frequencies (50 kHz to 15 MHz). Emission spectroscopy and resonant absorption and laser absorption on He(23S) metastable atoms have been used to characterize different plasma regimes, which with increasing frequency changes from a low pressure glow discharge (APGD) to Townsend-like mode (TL) and finally to a continuously sustained plasma. This later can be in Ω mode (with uniform E-field) or RF- α mode (with sheath formation). Depending on applied power, the time-averaged He(23S) density remains below 3 1016 m-3 in TL and Ω modes, can reach 7 1016 m-3 in APGD and RF- α modes and up to 4 1017 m-3 in a combination of APGD and RF- α modes (Hybrid). Time-resolved He(23S) densities show an overshoot on the ignition phase, which in RF- α mode can be attributed to a secondary source of ionization involving metastable atoms.

  6. Magnetic roller gas gate employing transonic sweep gas flow to isolate regions of differing gaseous composition or pressure

    DOEpatents

    Doehler, Joachim

    1994-12-20

    Disclosed herein is an improved gas gate for interconnecting regions of differing gaseous composition and/or pressure. The gas gate includes a narrow, elongated passageway through which substrate material is adapted to move between said regions and inlet means for introducing a flow of non-contaminating sweep gas into a central portion of said passageway. The gas gate is characterized in that the height of the passageway and the flow rate of the sweep gas therethrough provides for transonic flow of the sweep gas between the inlet means and at least one of the two interconnected regions, thereby effectively isolating one region, characterized by one composition and pressure, from another region, having a differing composition and/or pressure, by decreasing the mean-free-path length between collisions of diffusing species within the transonic flow region. The gas gate preferably includes a manifold at the juncture point where the gas inlet means and the passageway interconnect.

  7. Kinetic study on the photoabsorption process of gaseous O 2 dimol at 630 nm in a wide pressure range

    NASA Astrophysics Data System (ADS)

    Ida, Akira; Furui, Eiji; Akai, Nobuyuki; Kawai, Akio; Shibuya, Kazuhiko

    2010-03-01

    The visible light absorption of gaseous O 2 dimol at 630 nm was measured in the pressure region of 0.04-90 atm. The intensities measured at high pressures did not agree with the values extrapolated from the data obtained at low pressures. A kinetic analysis assuming the equilibrium between the dimol and free O 2 monomers was performed. All the data are well reproduced by the model using the 630 nm absorption cross-section of (5.6 ± 3.3) × 10 -24 cm 2 molecule -1 and the dissociation equilibrium constant of (6.8 ± 4.2) × 10 21 molecules cm -3. The critical distance between the O 2 molecules in the dimol is discussed on the basis of the equilibrium constant determined.

  8. Homogeneous nucleation rate measurements of 1-propanol in helium: the effect of carrier gas pressure.

    PubMed

    Brus, David; Zdímal, Vladimír; Stratmann, Frank

    2006-04-28

    Kinetics of homogeneous nucleation in supersaturated vapor of 1-propanol was studied using an upward thermal diffusion cloud chamber. Helium was used as a noncondensable carrier gas and the influence of its pressure on observed nucleation rates was investigated. The isothermal nucleation rates were determined by a photographic method that is independent on any nucleation theory. In this method, the trajectories of growing droplets are recorded using a charge coupled device camera and the distribution of local nucleation rates is determined by image analysis. The nucleation rate measurements of 1-propanol were carried out at four isotherms 260, 270, 280, and 290 K. In addition, the pressure dependence was investigated on the isotherms 290 K (50, 120, and 180 kPa) and 280 K (50 and 120 kPa). The isotherm 270 K was measured at 25 kPa and the isotherm 260 K at 20 kPa. The experiments confirm the earlier observations from several thermal diffusion chamber investigations that the homogeneous nucleation rate of 1-propanol tends to increase with decreasing total pressure in the chamber. In order to reduce the possibility that the observed phenomenon is an experimental artifact, connected with the generally used one-dimensional description of transfer processes in the chamber, a recently developed two-dimensional model of coupled heat, mass, and momentum transfer inside the chamber was used and results of both models were compared. It can be concluded that the implementation of the two-dimensional model does not explain the observed effect. Furthermore the obtained results were compared both to the predictions of the classical theory and to the results of other investigators using different experimental devices. Plotting the experimental data on the so-called Hale plot shows that our data seem to be consistent both internally and also with the data of others. Using the nucleation theorem the critical cluster sizes were obtained from the slopes of the individual isotherms

  9. Analytical model of atmospheric pressure, helium/trace gas radio-frequency capacitive Penning discharges

    NASA Astrophysics Data System (ADS)

    Lieberman, M. A.

    2015-04-01

    Atmospheric and near-atmospheric pressure, helium/trace gas radio-frequency capacitive discharges have wide applications. An analytic equilibrium solution is developed based on a homogeneous, current-driven discharge model that includes sheath and electron multiplication effects and contains two electron populations. A simplified chemistry is used with four unknown densities: hot electrons, warm electrons, positive ions and metastables. The dominant electron-ion pair production is Penning ionization, and the dominant ion losses are to the walls. The equilibrium particle balances are used to determine a single ionization balance equation for the warm electron temperature, which is solved, both approximately within the α- and γ-modes, and exactly by conventional root-finding techniques. All other discharge parameters are found, the extinction and α-γ transitions are determined, and a similarity law is given, in which the equilibrium for a short gap at high pressure can be rescaled to a longer gap at lower pressure. Within the α-mode, we find the scaling of the discharge parameters with current density, frequency, gas density and gap width. The analytic results are compared to hybrid and particle-in-cell (PIC) results for He/0.1%N2, and to hybrid results for He/0.1%H2O. For nitrogen, a full reaction set is used for the hybrid calculations and a simplified reaction set for the PIC simulations. For the chemically complex water trace gas, a set of 209 reactions among 43 species is used. The analytic results are found to be in reasonably good agreement with the more elaborate hybrid and PIC calculations.

  10. On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

    NASA Technical Reports Server (NTRS)

    Miller, Eric L.; Dudenhoefer, James E.

    1989-01-01

    In free piston Stirling engine research the integrity of both amplitude and phase of the dynamic pressure measurements is critical to the characterization of cycle dynamics and thermodynamics. It is therefore necessary to appreciate all possible sources of signal distortion when designing pressure measurement systems for this type of research. The signal distortion inherent to pressure transmission lines is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving helium-charged free piston Stirling engines. The scope and limitations of the dynamic response analysis are considered.

  11. Helium Pressure Shift of the Hyperfine Clock Transition in Hg-201(+)

    NASA Technical Reports Server (NTRS)

    Larigani, S. Taghavi; Burt, E. A.; Tjoelker, R. L.

    2010-01-01

    There are two stable odd isotopes of mercury with singly ionized hyperfine structure suitable for a microwave atomic clock: Hg-199(+) and Hg-201(+). We are investigating the viability of a trapped ion clock based on Hg-201(+) in a configuration that uses a buffer gas to increase ion loading efficiency and counter ion heating from rf trapping fields. Traditionally, either helium or neon is used as the buffer gas at approx. 10(exp -5) torr to confine mercury ions near room temperature. In addition to the buffer gas, other residual background gasses such as H2O, N2, O2, CO, CO2, and CH2 may be present in trace quantities. Collisions between trapped ions and buffer gas or background gas atoms/molecules produce a momentary shift of the ion clock transition frequency and constitute one of the largest systematic effects in this type of clock. Here we report an initial measurement of the He pressure shift in Hg-201(+) and compare this to Hg-199(+).

  12. Production and provision mechanisms of OH radical of an atmospheric-pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Yonemori, Seiya; Ono, Ryo; Oda, Tetsuji

    2012-10-01

    An atmospheric-pressure helium plasma jet is getting much attention because of its low heat load. It is known that active species such as OH radical play important role in many plasma processes, for example, in plasma medical care or in plasma sterilization. When using the plasma jet for surface treatment, it is important that the amount of OH radical provided into objectives. We measured OH density in the vicinity of the surface of objectives using laser induced fluorescence (LIF). The plasma jet was generated when AC 8 kHz, 10 kV was applied. When the plasma jet extended onto the dry glass surface, the maximum OH density was 0.2 ppm. On the other hand, the maximum OH density was 1 ppm when the plasma jet extended onto the wet surface. In addition, time-evolution of OH density between two successive voltage pulses was measured. On the edge of the plasma jet, OH density was at maximum and rapidly decreased between two pulses. Those results suggest that there are three ways of OH production; first, the dissociation of H2O included in discharge gas; secondly, the dissociation of H2O included in the ambient air; finally, the dissociation of H2O evaporates from the wet surface.

  13. Electron properties of the plume of an atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Adress, Wameedh; Nedanovska, Elena; Nersisyan, Gagik; Riley, David; Graham, William

    2013-09-01

    Atmospheric pressure plasma, APP, jets, are now attracting great interest because of their potential uses in many applications; for example surface modification and plasma medicine. These applications require an insight into their plasma chemistry, which is strongly influenced by the electron energy distribution function. Here we report the use of Thomson scattering to measure the electron properties in the plume created by a 20 kHz, 2mm diameter helium APP jet operating into the open air. A 532 nm Nd:YAG laser beam is focussed into the plasma plume. The temporally and spatially resolved spectra of light at 90° to the laser direction is detected. The spectra contain light from Thomson Scattering from electrons, along with Rayleigh and Raman scattering from atoms and molecules. These components are resolved in a manner similar to that described in ref 1. Our measurements reveal a ``ring-like'' radial distribution of both the electron density and temperature, with outer values of ~ 7×1013 cm-3 and 0.4 eV and inner values of ~ 2×1013 cm-3 and 0.1 eV respectively at 4 mm from the end of the quartz tube.

  14. Array of surface-confined glow discharges in atmospheric pressure helium: Modes and dynamics

    SciTech Connect

    Li, D.; Liu, D. X. E-mail: mglin5g@gmail.com; Nie, Q. Y.; Li, H. P.; Chen, H. L.; Kong, M. G. E-mail: mglin5g@gmail.com

    2014-05-19

    Array of atmospheric pressure surface discharges confined by a two-dimensional hexagon electrode mesh is studied for its discharge modes and temporal evolution so as to a theoretical underpinning to their growing applications in medicine, aerodynamic control, and environmental remediation. Helium plasma surface-confined by one hexagon-shaped rim electrode is shown to evolve from a Townsend mode to a normal and abnormal glow mode, and its evolution develops from the rim electrodes as six individual microdischarges merging in the middle of the hexagon mesh element. Within one hexagon element, microdischarges remain largely static with the mesh electrode being the instantaneous cathode, but move towards the hexagon center when the electrode is the instantaneous anode. On the entire array electrode surface, plasma ignition is found to beat an unspecific hexagon element and then spreads to ignite surrounding hexagon elements. The spreading of microdischarges is in the form of an expanding circle at a speed of about 3 × 10{sup 4} m/s, and their quenching starts in the location of the initial plasma ignition. Plasma modes influence how input electrical power is used to generate and accelerate electrons and as such the reaction chemistry, whereas plasma dynamics are central to understand and control plasma instabilities. The present study provides an important aspect of plasma physics of the atmospheric surface-confined discharge array and a theoretical underpinning to its future technological innovation.

  15. Numerical simulation of a direct current glow discharge in atmospheric pressure helium

    NASA Astrophysics Data System (ADS)

    Yin, Zeng-Qian; Wang, Yan; Zhang, Pan-Pan; Zhang, Qi; Li, Xue-Chen

    2016-12-01

    Characteristics of a direct current (DC) discharge in atmospheric pressure helium are numerically investigated based on a one-dimensional fluid model. The results indicate that the discharge does not reach its steady state till it takes a period of time. Moreover, the required time increases and the current density of the steady state decreases with increasing the gap width. Through analyzing the spatial distributions of the electron density, the ion density and the electric field at different discharge moments, it is found that the DC discharge starts with a Townsend regime, then transits to a glow regime. In addition, the discharge operates in a normal glow mode or an abnormal glow one under different parameters, such as the gap width, the ballast resistors, and the secondary electron emission coefficients, judged by its voltage-current characteristics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11575050 and 10805013), the Midwest Universities Comprehensive Strength Promotion Project, the Natural Science Foundation of Hebei Province, China (Grant Nos. A2016201042 and A2015201092), and the Research Foundation of Education Bureau of Hebei Province, China (Grant No. LJRC011).

  16. Liquid Hydrogen Regulated Low Pressure High Flow Pneumatic Panel AFT Arrow Analysis

    NASA Technical Reports Server (NTRS)

    Jones, Kelley, M.

    2013-01-01

    Project Definition: Design a high flow pneumatic regulation panel to be used with helium and hydrogen. The panel will have two circuits, one for gaseous helium (GHe) supplied from the GHe Movable Storage Units (MSUs) and one for gaseous hydrogen (GH2) supplied from an existing GH2 Fill Panel. The helium will supply three legs; to existing panels and on the higher pressure leg and Simulated Flight Tanks (SFTs) for the lower pressure legs. The hydrogen line will pressurize a 33,000 gallon vacuum jacketed vessel.

  17. Helium jet dispersion to atmosphere

    NASA Astrophysics Data System (ADS)

    Khan, Hasna J.

    On the event of loss of vacuum guard of superinsulated helium dewar, high rate of heat transfer into the tank occurs. The rapid boiling of liquid helium causes the burst disk to rupture at four atmospheres and consequently the helium passes to the atmosphere through vent lines. The gaseous helium forms a vertical buoyant jet as it exits the vent line into a stagnant environment. Characterization of the gaseous jet is achieved by detailed analysis of the axial and radial dependence of the flow parameters.

  18. Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Taskinoglu, Ezgi

    2012-01-01

    The simulation of high-pressure turbulent flows, where the pressure, p, is larger than the critical value, p(sub c), for the species under consideration, is relevant to a wide array of propulsion systems, e.g. gas turbine, diesel, and liquid rocket engines. Most turbulence models, however, have been developed for atmospheric-p turbulent flows. The difference between atmospheric-p and supercritical-p turbulence is that, in the former situation, the coupling between dynamics and thermodynamics is moderate to negligible, but for the latter it is very significant, and can dominate the flow characteristics. The reason for this stems from the mathematical form of the equation of state (EOS), which is the perfect-gas EOS in the former case, and the real-gas EOS in the latter case. For flows at supercritical pressure, p, the large eddy simulation (LES) equations consist of the differential conservation equations coupled with a real-gas EOS. The equations use transport properties that depend on the thermodynamic variables. Compared to previous LES models, the differential equations contain not only the subgrid scale (SGS) fluxes, but also new SGS terms, each denoted as a correction. These additional terms, typically assumed null for atmospheric pressure flows, stem from filtering the differential governing equations, and represent differences between a filtered term and the same term computed as a function of the filtered flow field. In particular, the energy equation contains a heat-flux correction (q-correction) that is the difference between the filtered divergence of the heat flux and the divergence of the heat flux computed as a function of the filtered flow field. In a previous study, there was only partial success in modeling the q-correction term, but in this innovation, success has been achieved by using a different modeling approach. This analysis, based on a temporal mixing layer Direct Numerical Simulation database, shows that the focus in modeling the q

  19. Effects of metastable species in helium and argon atmospheric pressure plasma jets (APPJs) on inactivation of periodontopathogenic bacteria

    NASA Astrophysics Data System (ADS)

    Yoon, Sung-Young; Kim, Kyoung-Hwa; Seol, Yang-Jo; Kim, Su-Jeong; Bae, Byeongjun; Huh, Sung-Ryul; Kim, Gon-Ho

    2016-05-01

    The helium and argon have been widely used as discharge gases in atmospheric pressure plasma jets (APPJs) for bacteria inactivation. The APPJs show apparent different in bullet propagation speed and bacteria inactivation rate apparently vary with discharge gas species. This work shows that these two distinctive features of APPJs can be linked through one factor, the metastable energy level. The effects of helium and argon metastable species on APPJ discharge mechanism for reactive oxygen nitrogen species (RONS) generation in APPJs are investigated by experiments and numerical estimation. The discharge mechanism is investigated by using the bullet velocity from the electric field which is obtained with laser induced fluorescence (LIF) measurement. The measured electric field also applied on the estimation of RONS generation, as electron energy source term in numerical particle reaction. The estimated RONS number is verified by comparing NO and OH densities to the inactivation rate of periodontitis bacteria. The characteristic time for bacteria inactivation of the helium-APPJ was found to be 1.63 min., which is significantly less than that of the argon-APPJ, 12.1 min. In argon-APPJ, the argon metastable preserve the energy due to the lack of the Penning ionization. Thus the surface temperature increase is significantly higher than helium-APPJ case. It implies that the metastable energy plays important role in both of APPJ bullet propagation and bacteria inactivation mechanism.

  20. Investigation of the threshold intensity versus gas pressure in the breakdown of helium by 248 nm laser radiation

    NASA Astrophysics Data System (ADS)

    Gamal, Yosr E. E.-D.; Abdellatif, Galila

    2014-10-01

    An investigation of the unexpectedly strong dependence of the threshold intensity on the gas pressure in the experimental study on the breakdown of He by short laser wavelength (Turcu et al., in Opt Commun, 134:66-68, 1997) is presented. A modified electron cascade model is applied (Evans and Gamal, in J Phys D Appl Phys, 13:1447-1458, 1980). Computations revealed reasonable agreement between the calculated thresholds and the measured ones. Moreover, the calculated electron energy distribution function and its parameters proved that multiphoton ionization of ground and excited atoms is the main source for the seed electrons, which contributes to the breakdown of helium. The effect of diffusion losses over pressures <1,000 Torr elucidated the origin of the strong dependence of the threshold intensity on the gas pressure. Collisional ionization dominates only at high pressures. No evidence for recombination losses is observed for pressures up to 3,000 Torr.

  1. Afterglow chemistry of atmospheric-pressure helium-oxygen plasmas with humid air impurity

    NASA Astrophysics Data System (ADS)

    Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

    2014-04-01

    The formation of reactive species in the afterglow of a radio-frequency-driven atmospheric-pressure plasma in a fixed helium-oxygen feed gas mixture (He+0.5%O2) with humid air impurity (a few hundred ppm) is investigated by means of an extensive global plasma chemical kinetics model. As an original objective, we explore the effects of humid air impurity on the biologically relevant reactive species in an oxygen-dependent system. After a few milliseconds in the afterglow environment, the densities of atomic oxygen (O) decreases from 1015 to 1013 cm-3 and singlet delta molecular oxygen (O2(1D)) of the order of 1015 cm-3 decreases by a factor of two, while the ozone (O3) density increases from 1014 to 1015 cm-3. Electrons and oxygen ionic species, initially of the order of 1011 cm-3, recombine much faster on the time scale of some microseconds. The formation of atomic hydrogen (H), hydroxyl radical (OH), hydroperoxyl (HO2), hydrogen peroxide (H2O2), nitric oxide (NO) and nitric acid (HNO3) resulting from the humid air impurity as well as the influence on the afterglow chemistry is clarified with particular emphasis on the formation of dominant reactive oxygen species (ROS). The model suggests that the reactive species predominantly formed in the afterglow are major ROS O2(1D) and O3 (of the order of 1015 cm-3) and rather minor hydrogen- and nitrogen-based reactive species OH, H2O2, HNO3 and NO2/NO3, of which densities are comparable to the O-atom density (of the order of 1013 cm-3). Furthermore, the model quantitatively reproduces the experimental results of independent O and O3 density measurements.

  2. Influence of voltage magnitude on the dynamic behavior of a stable helium atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Ning, Wenjun; Wang, Lijun; Wu, Chen; Jia, Shenli

    2014-08-01

    Effects of voltage magnitude on the development of a stable helium atmospheric pressure plasma jet are investigated by current measurements and high temporal-resolution streak images. Generated by a coaxial dielectric barrier discharge structure, the entire discharge can be classified into three regions: discharges in the tube gap, downstream jet, and up-streamer. The discharge morphologies of each region are analyzed. In the positive discharge phase, there are two discharges in the tube gap between the electrodes; the first one is ignited as corona and then developed into streamer corona, and the second one is similar with positive glow. The downstream jet is ignited independently from the discharge in the tube gap. Referred as "plasma bullet," the dynamic behavior of the jet can be well described as a positive streamer. Under specific applied voltage, the jet is found to be composed by double bullets in which case the jet length decreases since that less charge is carried by the first bullet. The up-streamer can be captured as long as the discharge in the tube gap is activated. Propagating with velocity of ˜4 km/s, the up-streamer can be regarded as the extension of the first discharge in the tube gap. In the negative discharge phase, the discharge is confined in the tube gap with nearly symmetrical morphology with the positive one. Besides, with the rising of voltage, the negative discharge is initially intensified and then turns weaker after surpassing certain voltage, which may provide suitable condition for the occurrence of double-bullet phenomenon.

  3. Comparison of nitrogen narcosis and helium pressure effects on striatal amino acids: a microdialysis study in rats.

    PubMed

    Vallée, Nicolas; Rostain, Jean-Claude; Boussuges, Alain; Risso, Jean-Jacques

    2009-05-01

    Exposure to nitrogen-oxygen mixture at high pressure induces narcosis, which can be considered as a first step toward general anaesthesia. Narcotic potencies of inert gases are attributed to their lipid solubility. Nitrogen narcosis induces cognitive and motor disturbances that occur from 0.3 MPa in man and from 1 MPa in rats. Neurochemical studies performed in rats up to 3 MPa have shown that nitrogen pressure decreases striatal dopamine release like argon, another inert gas, or nitrous oxide, an anaesthetic gas. Striatal dopamine release is under glutamatergic and other amino acid neurotransmission regulations. The aim of this work was to study the effects of nitrogen at 3 MPa on striatal amino acid levels and to compare to those of 3 MPa of helium which is not narcotic at this pressure, by using a new technique of microdialysis samples extraction under hyperbaric conditions, in freely moving rats. Amino acids were analysed by HPLC coupled to fluorimetric detection in order to appreciate glutamate, aspartate, glutamine and asparagine levels. Nitrogen-oxygen mixture exposure at 3 MPa decreased glutamate, glutamine and asparagine concentrations. In contrast, with helium-oxygen mixture, glutamate and aspartate levels were increased during the compression phase but not during the stay at maximal pressure. Comparison between nitrogen and helium highlighted the narcotic effects of nitrogen at pressure. As a matter of fact, nitrogen induces a reduction in glutamate and in other amino acids that could partly explain the decrease in striatal dopamine level as well as the motor and cognitive disturbances reported in nitrogen narcosis.

  4. The effects of added hydrogen on a helium atmospheric-pressure plasma jet ambient desorption/ionization source.

    PubMed

    Wright, Jonathan P; Heywood, Matthew S; Thurston, Glen K; Farnsworth, Paul B

    2013-03-01

    We present mass spectrometric data demonstrating the effect that hydrogen has on a helium-based dielectric-barrier discharge (DBD) atmospheric-pressure plasma jet used as an ambient desorption/ionization (ADI) source. The addition of 0.9 % hydrogen to the helium support gas in a 35-W plasma jet increased signals for a range of test analytes, with enhancement factors of up to 68, without proportional increases in background levels. The changes in signal levels result from a combination of changes in the desorption kinetics from the surface and increased ion production in the gas phase. The enhancement in ADI-MS performance despite the quenching of key plasma species reported in earlier studies suggests that ionization with a H2/He plasma jet is the result of an alternate mechanism involving the direct generation of ionized hydrogen.

  5. The rate of pressure rise of gaseous propylene-air explosions in spherical and cylindrical enclosures.

    PubMed

    Razus, Domnina; Movileanua, Codina; Oancea, Dumitru

    2007-01-02

    The maximum rates of pressure rise of propylene-air explosions at various initial pressures and various fuel/oxygen ratios in three closed vessels (a spherical vessel with central ignition and two cylindrical vessels with central or with top ignition) are reported. It was found that in explosions of quiescent mixtures the maximum rates of pressure rise are linear functions on total initial pressure, at constant initial temperature and fuel/oxygen ratio. The slope and intercept of found correlations are greatly influenced by vessel's volume and shape and by the position of the ignition source--factors which determine the amount of heat losses from the burned gas in a closed vessel explosion. Similar data on propylene-air inert mixtures are discussed in comparison with those referring to propylene-air, revealing the influence of nature and amount of inert additive. The deflagration index KG of centrally ignited explosions was also calculated from maximum rates of pressure rise.

  6. Helium tables.

    NASA Technical Reports Server (NTRS)

    Havill, Clinton H

    1928-01-01

    These tables are intended to provide a standard method and to facilitate the calculation of the quantity of "Standard Helium" in high pressure containers. The research data and the formulas used in the preparation of the tables were furnished by the Research Laboratory of Physical Chemistry, of the Massachusetts Institute of Technology.

  7. A theoretical and experimental study of pressure broadening of the oxygen A-band by helium

    SciTech Connect

    Grimminck, Dennis L. A. G.; Spiering, Frans R.; Janssen, Liesbeth M. C.; Avoird, Ad van der; Zande, Wim J. van der; Groenenboom, Gerrit C.

    2014-05-28

    The rotationally resolved magnetic dipole absorption spectrum of the oxygen A-band b{sup 1}Σ{sub g}{sup +}(v=0)←X{sup 3}Σ{sub g}{sup −}(v=0) perturbed by collisions with helium was studied theoretically using the impact approximation. To calculate the relaxation matrix, scattering calculations were performed on a newly computed helium-oxygen (b{sup 1}Σ{sub g}{sup +}) interaction potential as well as on a helium-oxygen (X{sup 3}Σ{sub g}{sup −}) interaction potential from the literature. The calculated integrated line cross sections and broadening coefficients are in good agreement with experimental results from the literature. Additionally, cavity ring-down experiments were performed in the wings of the spectral lines for a quantitative study of line-mixing, i.e., the redistribution of rotational line intensities by helium-oxygen collisions. It is shown that inclusion of line-mixing in the theory is required to reproduce the experimentally determined absolute absorption strengths as a function of the density of the helium gas.

  8. Noncavitating Pump For Liquid Helium

    NASA Technical Reports Server (NTRS)

    Hasenbein, Robert; Izenson, Michael; Swift, Walter; Sixsmith, Herbert

    1996-01-01

    Immersion pump features high efficiency in cryogenic service. Simple and reliable centrifugal pump transfers liquid helium with mass-transfer efficiency of 99 percent. Liquid helium drawn into pump by helical inducer, which pressurizes helium slightly to prevent cavitation when liquid enters impeller. Impeller then pressurizes liquid. Purpose of pump to transfer liquid helium from supply to receiver vessel, or to provide liquid helium flow for testing and experimentation.

  9. Impact sensitivity of materials in contact with liquid and gaseous oxygen at high pressure

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1972-01-01

    As a result of the Apollo 13 incident, increased emphasis is being placed on materials compatibility in a high pressure GOX environment. It is known that in addition to impact sensitivity of materials, approximately adiabatic compression conditions can contrive to induce materials reactivity. Test runs at high pressure using the ABMA tester indicate the following: (1) The materials used in the tests showed an inverse relationship between thickness and impact sensitivity. (2) Several materials tested exhibited greater impact sensitivity in GOX than in LOX. (3) The impact sensitivity of the materials tested in GOX, at the pressures tested, showed enhanced impact sensitivity with higher pressure. (4) The rank ordering of the materials tested in LOX up to 1000 psia is the same as the rank ordering resulting from tests in LOX at 14.7 psia.

  10. Thermodynamics of dense molecular hydrogen-helium mixtures at high pressure

    NASA Technical Reports Server (NTRS)

    Marley, Mark S.; Hubbard, William B.

    1988-01-01

    Effective intermolecular pair potentials derived from liquid hydrogen and helium shock wave experiments are presently used in Monte Carlo simulations of mixtures of hydrogen and helium, at densities of up to 1.2 g/cu cm. The model interaction Helmholtz free energy derived accurately reproduces both the Monte Carlo calculation results and the experimental data obtained for densities of up to about 0.6 g/cu cm. An equation of state is derived from the free energy expression that could be useful in interior models of such Jovian planets as Saturn.

  11. Functional evaluation of rat hearts transplanted after preservation in a high-pressure gaseous mixture of carbon monoxide and oxygen

    PubMed Central

    Hatayama, Naoyuki; Inubushi, Masayuki; Naito, Munekazu; Hirai, Shuichi; Jin, Yong-Nan; Tsuji, Atsushi B.; Seki, Kunihiro; Itoh, Masahiro; Saga, Tsuneo; Li, Xiao-Kang

    2016-01-01

    We recently succeeded in resuscitating an extracted rat heart following 24–48 hours of preservation in a high-pressure gaseous mixture of carbon monoxide (CO) and oxygen (O2). This study aimed to examine the function of rat hearts transplanted after being preserved in the high-pressure CO and O2 gas mixture. The hearts of donor rats were preserved in a chamber filled with CO and O2 under high pressure for 24 h (CO24h) or 48 h at 4 °C. For the positive control (PC) group, hearts immediately extracted from donor rats were used for transplantation. The preserved hearts were transplanted into recipient rats by heterotopic cervical heart transplantation. CO toxicity does not affect the grafts or the recipients. Light microscopy and [18F]-fluorodeoxyglucose positron emission tomography revealed that there were no significant differences in the size of the myocardial infarction or apoptosis of myocardial cells in post-transplant hearts between the PC and CO24h groups. Furthermore, at 100 days after the transplantation, the heart rate, weight and histological staining of the post-transplanted hearts did not differ significantly between the PC and CO24h groups. These results indicate that the function of rat hearts is well preserved after 24 hours of high-pressure preservation in a CO and O2 gas mixture. Therefore, high-pressure preservation in a gas mixture can be a useful method for organ preservation. PMID:27562456

  12. Use of Heated Helium to Simulate Surface Pressure Fluctuations on the Launch Abort Vehicle During Abort Motor Firing

    NASA Technical Reports Server (NTRS)

    Panda, Jayanta; James, George H.; Burnside, Nathan J.; Fong, Robert; Fogt, Vincent A.

    2011-01-01

    The solid-rocket plumes from the Abort motor of the Multi-Purpose Crew Vehicle (MPCV, also know as Orion) were simulated using hot, high pressure, Helium gas to determine the surface pressure fluctuations on the vehicle in the event of an abort. About 80 different abort situations over a wide Mach number range, (0.3< or =M< or =1.2) and vehicle attitudes (+/-15deg) were simulated inside the NASA Ames Unitary Plan, 11-Foot Transonic Wind Tunnel. For each abort case, typically two different Helium plume and wind tunnel conditions were used to bracket different flow matching critera. This unique, yet cost-effective test used a custom-built hot Helium delivery system, and a 6% scale model of a part of the MPCV, known as the Launch Abort Vehicle. The test confirmed the very high level of pressure fluctuations on the surface of the vehicle expected during an abort. In general, the fluctuations were found to be dominated by the very near-field hydrodynamic fluctuations present in the plume shear-layer. The plumes were found to grow in size for aborts occurring at higher flight Mach number and altitude conditions. This led to an increase in the extent of impingement on the vehicle surfaces; however, unlike some initial expectations, the general trend was a decrease in the level of pressure fluctuations with increasing impingement. In general, the highest levels of fluctuations were found when the outer edges of the plume shear layers grazed the vehicle surface. At non-zero vehicle attitudes the surface pressure distributions were found to become very asymmetric. The data from these wind-tunnel simulations were compared against data collected from the recent Pad Abort 1 flight test. In spite of various differences between the transient flight situation and the steady-state wind tunnel simulations, the hot-Helium data were found to replicate the PA1 data fairly reasonably. The data gathered from this one-of-a-kind wind-tunnel test fills a gap in the manned-space programs

  13. System and process for capture of acid gasses at elevated pressure from gaseous process streams

    SciTech Connect

    Heldebrant, David J.; Koech, Phillip K.; Linehan, John C.; Rainbolt, James E.; Bearden, Mark D.; Zheng, Feng

    2016-09-06

    A system, method, and material that enables the pressure-activated reversible chemical capture of acid gasses such as CO.sub.2 from gas volumes such as streams, flows or any other volume. Once the acid gas is chemically captured, the resulting product typically a zwitterionic salt, can be subjected to a reduced pressure whereupon the resulting product will release the captures acid gas and the capture material will be regenerated. The invention includes this process as well as the materials and systems for carrying out and enabling this process.

  14. Analysis of gaseous toxic industrial compounds and chemical warfare agent simulants by atmospheric pressure ionization mass spectrometry.

    PubMed

    Cotte-Rodríguez, Ismael; Justes, Dina R; Nanita, Sergio C; Noll, Robert J; Mulligan, Christopher C; Sanders, Nathaniel L; Cooks, R Graham

    2006-04-01

    The suitability of atmospheric pressure chemical ionization mass spectrometry as sensing instrumentation for the real-time monitoring of low levels of toxic compounds is assessed, especially with respect to public safety applications. Gaseous samples of nine toxic industrial compounds, NH3, H2S, Cl2, CS2, SO2, C2H4O, HBr, C6H6 and AsH3, and two chemical warfare agent simulants, dimethyl methylphosphonate (DMMP) and methyl salicylate (MeS), were studied. API-MS proves highly suited to this application, with speedy analysis times (<30 seconds), high sensitivity, high selectivity towards analytes, good precision, dynamic range and accuracy. Tandem MS methods were implemented in selected cases for improved selectivity, sensitivity, and limits of detection. Limits of detection in the parts-per-billion and parts-per-trillion range were achieved for this set of analytes. In all cases detection limits were well below the compounds' permissible exposure limits (PELs), even in the presence of added complex mixtures of alkanes. Linear responses, up to several orders of magnitude, were obtained over the concentration ranges studied (sub-ppb to ppm), with relative standard deviations less than 3%, regardless of the presence of alkane interferents. Receiver operating characteristic (ROC) curves are presented to show the performance trade-off between sensitivity, probability of correct detection, and false positive rate. A dynamic sample preparation system for the production of gas phase analyte concentrations ranging from 100 pptr to 100 ppm and capable of admixing gaseous matrix compounds and control of relative humidity and temperature is also described.

  15. Gas Temperature Determination in Argon-Helium Plasma at Atmospheric Pressure using van der Waals Broadening

    SciTech Connect

    Munoz, Jose; Yubero, Cristina; Calzada, Maria Dolores; Dimitrijevic, Milan S.

    2008-10-22

    The use of the van der Waals broadening of Ar atomic lines to determine the gas temperature in Ar-He plasmas, taking into account both argon and helium atoms as perturbers, has been analyzed. The values of the gas temperature inferred from this broadening have been compared with those obtained from the spectra of the OH molecular species in the discharge.

  16. D0 Silicon Upgrade: Gas Helium Storage Tank Pressure Vessel Engineering Note

    SciTech Connect

    Rucinski, Russ; /Fermilab

    1996-11-11

    This is to certify that Beaird Industries, Inc. has done a white metal blast per SSPC-SP5 as required per specifications on the vessel internal. Following the blast, a black light inspection was performed by Beaird Quality Control personnel to assure that all debris, grease, etc. was removed and interior was clean prior to closing vessel for helium test.

  17. Development of a High-Pressure Gaseous Burner for Calibrating Optical Diagnostic Techniques

    NASA Technical Reports Server (NTRS)

    Kojima, Jun; Nguyen, Quang-Viet

    2003-01-01

    In this work-in-progress report, we show the development of a unique high-pressure burner facility (up to 60 atm) that provides steady, reproducible premixed flames with high precision, while having the capability to use multiple fuel/oxidizer combinations. The highpressure facility has four optical access ports for applying different laser diagnostic techniques and will provide a standard reference flame for the development of a spectroscopic database in high-pressure/temperature conditions. Spontaneous Raman scattering (SRS) was the first diagnostic applied, and was used to successfully probe premixed hydrogen-air flames generated in the facility using a novel multi-jet micro-premixed array burner element. The SRS spectral data include contributions from H2, N2, O2, and H2O and were collected over a wide range of equivalence ratios ranging from 0.16 to 4.9 at an initial pressure of 10-atm via a spatially resolved point SRS measurement with a high-performance optical system. Temperatures in fuel-lean to stoichiometric conditions were determined from the ratio of the Stokes to anti-Stokes scattering of the Q-branch of N2, and those in fuel-rich conditions via the rotational temperature of H2. The SRS derived temperatures using both techniques were consistent and indicated that the flame temperature was approximately 500 K below that predicted by adiabatic equilibrium, indicating a large amount of heat-loss at the measurement zone. The integrated vibrational SRS signals show that SRS provides quantitative number density data in high-pressure H2-air flames.

  18. The Effect of Gaseous Additives on Dynamic Pressure Output and Ignition Sensitivity of Nanothermites

    NASA Astrophysics Data System (ADS)

    Puszynski, Jan; Doorenbos, Zac; Walters, Ian; Redner, Paul; Kapoor, Deepak; Swiatkiewicz, Jacek

    2011-06-01

    This contribution addresses important combustion characteristics of nanothermite systems. In this research the following nanothermites were investigated: a) Al-Bi2O3, b)Al-Fe2O3 and c)Al-Bi2O3-Fe2O3. The effect of various gasifying additives (such as nitrocellulose (NC) and cellulose acetate butyrate (CAB)) as well as reactant stoichiometry, reactant particle size and shape on processability, ignition delay time and dynamic pressure outputs at different locations in a combustion chamber will be presented. In addition, this contribution will report electrostatic and friction sensitivities of standard and modified nanothermites.

  19. Fatigue Crack Growth under High Pressure of Gaseous Hydrogen in a 15-5PH Martensitic Stainless Steel: Influence of Pressure and Loading Frequency

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Moriconi, C.; Benoit, G.; Halm, D.; Henaff, G.

    2013-03-01

    In this study, the effect of gaseous hydrogen pressure in relation with the loading frequency on the fatigue crack growth behavior of a precipitation-hardened martensitic stainless steel is investigated. It is found that increasing the hydrogen pressure from 0.09 to 9 MPa induces an enhancement of the fatigue crack growth rates. This enhancement is pronounced particularly at higher stress intensity factor amplitudes at 9 MPa. Meanwhile, decreasing the frequency from 20 to 0.2 Hz under 0.9 MPa of hydrogen reveals a significant increase in the crack growth rates that tends to join the curve obtained under 9 MPa at 20 Hz, but with a different cracking mode. However, it is shown that the degradation in fatigue crack growth behavior derives from a complex interaction between the fatigue damage and the amount of hydrogen enriching the crack tip, which is dependent on the hydrogen pressure, loading frequency, and stress intensity factor level. Scanning electron microscope (SEM) observations of the fracture surfaces are used to support the explanations proposed to account for the observed phenomena.

  20. Thermal performance of gaseous-helium-purged tank-mounted multilayer insulation system during ground-hold and space-hold thermal cycling and exposure to water vapor

    NASA Technical Reports Server (NTRS)

    Sumner, I. E.

    1978-01-01

    An experimental investigation was conducted to determine (1) the ground-hold and space-hold thermal performance of a multilayer insulation (MLI) system mounted on a spherical, liquid-hydrogen propellant tank and (2) the degradation to the space-hold thermal performance of the insulation system that resulted from both thermal cycling and exposure to moisture. The propellant tank had a diameter of 1.39 meters (4.57ft). The MLI consisted of two blankets of insulation; each blanket contained 15 double-aluminized Mylar radiation shields separated by double silk net spacers. Nineteen tests simulating basic cryogenic spacecraft thermal (environmental) conditions were conducted. These tests typically included initial helium purge, liquid-hydrogen fill and ground-hold, ascent, space-hold, and repressurization. No significant degradation of the space-hold thermal performance due to thermal cycling was noted.

  1. Pressure distributions on a 0.02-scale Space Shuttle orbiter nose at Mach 21.5 in helium

    NASA Technical Reports Server (NTRS)

    Ashby, George C., Jr.; Bernot, Peter T.; Woods, William C.

    1994-01-01

    Pressure distributions on a 0.02-scale model of the Space Shuttle orbiter forward fuselage were obtained in the 22-inch aerodynamic leg of the Langley Hypersonic Helium Tunnel Facility at a nominal free-stream Mach number of 21.5 and a ratio of specific heats of 1.67 for inclusion in the database of the Shuttle entry air data system (SEADS). The data were measured at model angles of attack of 0 deg to 50 deg in 5 deg increments for zero sideslip angle and at model sideslip angles of -5 deg to 5 deg for angles of attack equal to 5, 20, 35, and 40 deg. These data displayed trends similar to those observed in other wind tunnels at Mach 6 and 10 in air. Specifically noted is a shift in the location of the stagnation point at angles of attack above 15 deg; this effect did not, however, occur in flight. By comparison, the data obtained at Mach 6 in the Langley Hypersonic CF4 Tunnel, corresponding to a lower ratio of specific heats in the postshock region than those in helium and air, showed some reduction of the stagnation point shift at the higher angles of attack. The differences between flight and wind tunnel pressure distributions are believed due primarily to high-temperature gas chemistry effects in flight, which include lower effective specific heat ratios but which were not completely duplicated in the wind tunnels.

  2. Stabilities of filled ice II structure of hydrogen and helium hydrates at low temperatures and high pressures

    NASA Astrophysics Data System (ADS)

    Hirai, H.; Umeda, A.; Fujii, T.; Machida, S.; Shinozaki, A.; Kawamura, T.; Yamamoto, Y.; Yagi, T.

    2011-12-01

    Hydrogen hydrate is expected to be a hydrogen storage material, because it can contain relatively high hydrogen and its synthetic condition is mild comparable to industrial production. Three phases of hydrogen hydrate have been known so for. One is a clathrate hydrate sII [1], and others are filled ice II structure and filled ice Ic structure [2]. The ratio of water to hydrogen molecules for these phases are1:3, 1:6, 1:1, respectively. The clathrate sII containing only hydrogen molecules is stable only in a lower temperature region. At room temperature, above about 0.8 GPa filled ice II and above 2.5 GPa filled ice Ic are formed. The latter one survives at least up to 90 GPa [3]. However, investigations in low temperature and high pressure region have been limited. In this study, low temperature and high pressure experiments were performed by using diamond anvil cells and a helium-refrigeration cryostat in a region of 0.2 to 4.5 GPa and 130 to 300 K. X-ray diffractometry (XRD) showed a series of phase change from sII to filled ice Ic via filled ice II. For example, at 220K, sII transformed to filled ice II at approximately 0.7 GPa and further transformed to filled ice Ic structure at about 2.0 GPa. The present results experimentally confirmed the previously predicted phase boundaries. For filled ice II structure, Raman spectroscopy revealed that pressure dependency of vibration mode of guest hydrogen molecules and OH stretching mode of host water molecules changed at approximately 2.5 GPa. The XRD also showed change in axial ratio at the same pressure. These result suggested that state of filled ice II structure changed at about 2.5 GPa. Helium hydrate is known to form filled ice II structure [4], but high pressure study has not been yet fully performed. Similar experiments were carried out in a region of 0.2 to 5.0 GPa and 200 to 300 K. The results showed that the filled ice II structure did not transformed to filled ice Ic structure, but decomposed into helium

  3. Steady state boiling crisis in a helium vertically heated natural circulation loop - Part 2: Friction pressure drop lessening

    NASA Astrophysics Data System (ADS)

    Furci, H.; Baudouy, B.; Four, A.; Meuris, C.

    2016-01-01

    Experiments were conducted on a 2-m high two-phase helium natural circulation loop operating at 4.2 K and 1 atm. Two heated sections with different internal diameter (10 and 6 mm) were tested. The power applied on the heated section wall was controlled in increasing and decreasing sequences, and temperature along the section, mass flow rate and pressure drop evolutions were registered. The post-CHF regime was studied watching simultaneously the evolution of boiling crisis onset along the test section and the evolution of pressure drop and mass flow rate. A significant lessening of friction was observed simultaneous to the development of the post-CHF regime, accompanied by a mass flow rate increase, which lets suppose that the vapor film in the film boiling regime acts as a lubricant. A model was created based on this idea and on heat transfer considerations. The predictions by this model are satisfactory for the low quality post-CHF regime.

  4. High-pressure phase diagram and equation of state of solid helium from single-crystal X-ray diffraction to 23.3 GPa

    NASA Technical Reports Server (NTRS)

    Mao, H. K.; Hemley, R. J.; Jephcoat, A. P.; Finger, L. W.; Wu, Y.

    1988-01-01

    Single-crystal X-ray diffraction measurements have been performed on solid He-4 from 15.6 to 23.3 GPa at 300 K with synchrotron radiation. The diffraction patterns demonstrate that the structure of the solid is hexagonal close packed over this pressure-temperature range, contrary to both the interpretation of high-pressure optical studies and to theoretical predictions. The solid is more compressible than is indicated by equations of state calculated with recently determined helium pair potentials. The results suggest that a significant revision of current views of the phase diagram and energetics of dense solid helium is in order.

  5. The carrier gas pressure effect in a laminar flow diffusion chamber, homogeneous nucleation of n-butanol in helium.

    PubMed

    Hyvärinen, Antti-Pekka; Brus, David; Zdímal, Vladimír; Smolík, Jiri; Kulmala, Markku; Viisanen, Yrjö; Lihavainen, Heikki

    2006-06-14

    Homogeneous nucleation rate isotherms of n-butanol+helium were measured in a laminar flow diffusion chamber at total pressures ranging from 50 to 210 kPa to investigate the effect of carrier gas pressure on nucleation. Nucleation temperatures ranged from 265 to 280 K and the measured nucleation rates were between 10(2) and 10(6) cm(-3) s(-1). The measured nucleation rates decreased as a function of increasing pressure. The pressure effect was strongest at pressures below 100 kPa. This negative carrier gas effect was also temperature dependent. At nucleation temperature of 280 K and at the same saturation ratio, the maximum deviation between nucleation rates measured at 50 and 210 kPa was about three orders of magnitude. At nucleation temperature of 265 K, the effect was negligible. Qualitatively the results resemble those measured in a thermal diffusion cloud chamber. Also the slopes of the isothermal nucleation rates as a function of saturation ratio were different as a function of total pressure, 50 kPa isotherms yielded the steepest slopes, and 210 kPa isotherms the shallowest slopes. Several sources of inaccuracies were considered in the interpretation of the results: uncertainties in the transport properties, nonideal behavior of the vapor-carrier gas mixture, and shortcomings of the used mathematical model. Operation characteristics of the laminar flow diffusion chamber at both under-and over-pressure were determined to verify a correct and stable operation of the device. We conclude that a negative carrier gas pressure effect is seen in the laminar flow diffusion chamber and it cannot be totally explained with the aforementioned reasons.

  6. Influence of the excitation frequency on the density of helium metastable atoms in an atmospheric pressure dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Boisvert, J.-S.; Sadeghi, N.; Margot, J.; Massines, F.

    2017-01-01

    Diffuse dielectric barrier discharges in atmospheric-pressure helium can be sustained over a wide range of excitation frequencies (from, but not restricted, 25 kHz to 15 MHz). The aim of the present paper is to identify the specific characteristics of the discharge modes that can be sustained in this frequency range, namely, the atmospheric-pressure Townsend-like discharge (APTD-L) mode, the atmospheric-pressure glow discharge (APGD) mode, the Ω mode, the hybrid mode, and the RF-α mode. This is achieved experimentally, by measuring the density of helium metastable atoms, which are known to play a driving role on the discharge kinetics. This density is measured by means of two absorption spectroscopy methods, one using a spectral lamp and the other one using a diode laser as a light source. The first one provides the time-averaged atom densities in the singlet He(21S) and triplet He(23S) metastable states, while with the second one we access the time-resolved density of He(23S) atoms. Time-averaged measurements indicate that the He(23S) density is relatively low in the APTD-L, the Ω and the RF-α modes ( <4 ×1016 m-3 ) slightly higher in the APGD mode ( 2 -7 ×1016 m-3 ), and still higher ( >1 ×1017 m-3 ) in the hybrid mode. The hybrid mode is exclusively observed for frequencies from 0.2 to 3 MHz. However, time-resolved density measurement shows that at 1 MHz and below, the hybrid mode is not continuously sustained. Instead, the discharge oscillates between the Ω and the hybrid mode with a switching frequency about the kilohertz. This explains the significantly lower power required to sustain the plasma as compared to above 1 MHz.

  7. DC negative corona discharge in atmospheric pressure helium: transition from the corona to the ‘normal’ glow regime

    NASA Astrophysics Data System (ADS)

    Hasan, Nusair; Antao, Dion S.; Farouk, Bakhtier

    2014-06-01

    Direct current (dc) negative corona discharges in atmospheric pressure helium are simulated via detailed numerical modeling. Simulations are conducted to characterize the discharges in atmospheric helium for a pin plate electrode configuration. A self-consistent two-dimensional hybrid model is developed to simulate the discharges and the model predictions are validated with experimental measurements. The discharge model considered consists of momentum and energy conservation equations for a multi-component (electrons, ions, excited species and neutrals) gas mixture, conservation equations for each component of the mixture and state relations. A drift-diffusion approximation for the electron and the ion fluxes is used. A model for the external circuit driving the discharge is also considered and solved along with the discharge model. Many of the key features of a negative corona discharge, namely non-linear current-voltage characteristics, spatially flat cathode current density and glow-like discharge in the high current regime are displayed in the predictions. A transition to the ‘normal’ glow discharge from the corona discharge regime is also observed. The transition is identified from the calculated current-voltage characteristic curve and is characterized by the radial growth of the negative glow and the engulfment of the cathode wire.

  8. Effects of Oxygen Concentration on Pulsed Dielectric Barrier Discharge in Helium-Oxygen Mixture at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolong; Tan, Zhenyu; Pan, Jie; Chen, Xinxian

    2016-08-01

    In this work the effects of O2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions. The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He2+ and O2-, respectively, the densities of the reactive oxygen species (ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O2 concentration results in increasingly weak discharge and the time lag of the ignition. For O2 concentrations below 1.1%, the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O2 concentration and then the increase becomes weak. In particular, the total density of the reactive oxygen species reaches its maximums at the O2 concentration of about 0.5%. This characteristic further convinces the experimental observation that the O2 concentration of 0.5% is an optimal O2/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture. supported by the Fundamental Research Funds of Shandong University, China (No. 2016JC016)

  9. FAST TRACK COMMUNICATION: Contrasting characteristics of sub-microsecond pulsed atmospheric air and atmospheric pressure helium-oxygen glow discharges

    NASA Astrophysics Data System (ADS)

    Walsh, J. L.; Liu, D. X.; Iza, F.; Rong, M. Z.; Kong, M. G.

    2010-01-01

    Glow discharges in air are often considered to be the ultimate low-temperature atmospheric pressure plasmas for numerous chamber-free applications. This is due to the ubiquitous presence of air and the perceived abundance of reactive oxygen and nitrogen species in air plasmas. In this paper, sub-microsecond pulsed atmospheric air plasmas are shown to produce a low concentration of excited oxygen atoms but an abundance of excited nitrogen species, UV photons and ozone molecules. This contrasts sharply with the efficient production of excited oxygen atoms in comparable helium-oxygen discharges. Relevant reaction chemistry analysed with a global model suggests that collisional excitation of O2 by helium metastables is significantly more efficient than electron dissociative excitation of O2, electron excitation of O and ion-ion recombination. These results suggest different practical uses of the two oxygen-containing atmospheric discharges, with air plasmas being well suited for nitrogen and UV based chemistry and He-O2 plasmas for excited atomic oxygen based chemistry.

  10. Optical emission spectroscopic diagnostics of a non-thermal atmospheric pressure helium-oxygen plasma jet for biomedical applications

    NASA Astrophysics Data System (ADS)

    Thiyagarajan, Magesh; Sarani, Abdollah; Nicula, Cosmina

    2013-06-01

    In this work, we have applied optical emission spectroscopy diagnostics to investigate the characteristics of a non-thermal atmospheric pressure helium plasma jet. The discharge characteristics in the active and afterglow region of the plasma jet, that are critical for biomedical applications, have been investigated. The voltage-current characteristics of the plasma discharge were analyzed and the average plasma power was measured to be around 18 W. The effect of addition of small fractions of oxygen at 0.1%-0.5% on the plasma jet characteristics was studied. The addition of oxygen resulted in a decrease in plasma plume length due to the electronegativity property of oxygen. Atomic and molecular lines of selected reactive plasma species that are considered to be useful to induce biochemical reactions such as OH transitions A2Σ+(ν=0,1)→X2Π(Δν =0) at 308 nm and A2Σ+(ν=0,1)→X2Π(Δν =1) at 287 nm, O I transitions 3p5P→3s5S0 at 777.41 nm, and 3p3P→3s3S0 at 844.6 nm, N2(C-B) second positive system with electronic transition C3Πu→B3Πg in the range of 300-450 nm and N2+(B-X) first negative system with electronic transition B2Σu+→X2Σg+(Δν =0) at 391.4 nm have been studied. The atomic emission lines of helium were identified, including the He I transitions 3p3P0→2s3S at 388.8 nm, 3p1P0→ 2s1S at 501.6 nm, 3d3D→2p3P0 at 587.6 nm, 3d1D→2p1P0 at 667.8 nm, 3s3S1→2p3P0 at 706.5 nm, 3s1S0→2p1P0 at 728.1 nm, and Hα transition 2p-3d at 656.3 nm. Using a spectral fitting method, the OH radicals at 306-312 nm, the rotational and vibrational temperatures equivalent to gas temperatures of the discharge was measured and the effective non-equilibrium nature of the plasma jet was demonstrated. Our results show that, in the entire active plasma region, the gas temperature remains at 310 ± 25 K and 340 ± 25 K and it increases to 320 ± 25 K and 360 ± 25 K in the afterglow region of the plasma jet for pure helium and helium/oxygen (0.1%) mixture

  11. Helium permeability of different structure pyrolytic carbon coatings on graphite prepared at low temperature and atmosphere pressure

    NASA Astrophysics Data System (ADS)

    Song, Jinliang; Zhao, Yanling; Zhang, Wenting; He, Xiujie; Zhang, Dongsheng; He, Zhoutong; Gao, Yantao; Jin, Chan; Xia, Huihao; Wang, Jianqiang; Huai, Ping; Zhou, Xingtai

    2016-01-01

    Low density isotropic pyrolytic carbon (IPyC) and high density anisotropic pyrolytic carbon (APyC) coatings have been prepared at low temperature and atmosphere pressure. Helium gas permeabilities of nuclear graphite coated with IPyC and APyC of different thickness are studied using a vacuum apparatus. Both the permeation rates of the treated graphite gradually decrease with the increasing thickness of the coatings. The IPyC and APyC coatings can reduce the gas permeability coefficient of the samples by three and five orders of magnitude, respectively. The permeability difference is related to the microscopic structure, i.e., pores, as confirmed by scanning electron microscopy, mercury injection and X-ray tomography experiments. The changes of the permeability owing to heat cycles are observed to be negligible.

  12. Gaseous diffusion system

    DOEpatents

    Garrett, George A.; Shacter, John

    1978-01-01

    1. A gaseous diffusion system comprising a plurality of diffusers connected in cascade to form a series of stages, each of said diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof.

  13. Experimental study of forced convection heat transfer during upward and downward flow of helium at high pressure and high temperature

    SciTech Connect

    Francisco Valentin; Narbeh Artoun; Masahiro Kawaji; Donald M. McEligot

    2015-08-01

    Fundamental high pressure/high temperature forced convection experiments have been conducted in support of the development of a Very High Temperature Reactor (VHTR) with a prismatic core. The experiments utilize a high temperature/high pressure gas flow test facility constructed for forced convection and natural circulation experiments. The test section has a single 16.8 mm ID flow channel in a 2.7 m long, 108 mm OD graphite column with four 2.3kW electric heater rods placed symmetrically around the flow channel. This experimental study presents the role of buoyancy forces in enhancing or reducing convection heat transfer for helium at high pressures up to 70 bar and high temperatures up to 873 degrees K. Wall temperatures have been compared among 10 cases covering the inlet Re numbers ranging from 500 to 3,000. Downward flows display higher and lower wall temperatures in the upstream and downstream regions, respectively, than the upward flow cases due to the influence of buoyancy forces. In the entrance region, convection heat transfer is reduced due to buoyancy leading to higher wall temperatures, while in the downstream region, buoyancyinduced mixing causes higher convection heat transfer and lower wall temperatures. However, their influences are reduced as the Reynolds number increases. This experimental study is of specific interest to VHTR design and validation of safety analysis codes.

  14. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Lie, Zener Sukra; Khumaeni, Ali; Kurihara, Kazuyoshi; Kurniawan, Koo Hendrik; Lee, Yong Inn; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H--He and F--He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  15. Excitation Mechanism of H, He, C, and F Atoms in Metal-Assisted Atmospheric Helium Gas Plasma Induced by Transversely Excited Atmospheric-Pressure CO2 Laser Bombardment

    NASA Astrophysics Data System (ADS)

    Sukra Lie, Zener; Khumaeni, Ali; Kurihara, Kazuyoshi; Hendrik Kurniawan, Koo; Inn Lee, Yong; Fukumoto, Ken-ichi; Kagawa, Kiichiro; Niki, Hideaki

    2011-12-01

    To clarify the excitation mechanism of hydrogen in transversely excited atmospheric-pressure (TEA) CO2 laser-induced helium gas plasma, atomic emission characteristics of H, C, F, and He were studied using a Teflon sheet (thickness of 2 mm) attached to a metal subtarget. The TEA CO2 laser (750 mJ, 200 ns) was focused on the Teflon sheet in the surrounding He gas at 1 atm. Atomic emissions of H, C, F, and He occurred with a long lifetime, a narrow spectrum width, and a low-background spectrum. The correlation emission intensity curves of H-He and F-He indicated a parabolic functions. To explain the emission characteristics, we offered a model in which helium metastable atoms (He*) play an important role in the excitation processes; namely, atoms collide with helium metastable atoms (He*) to be ionized by the Penning effect, and then recombine with electrons to produce excited states, from which atomic emissions occur.

  16. Pressure - Density Isotherms of HELIUM-3 Gas Below 1.3 K.

    NASA Astrophysics Data System (ADS)

    Cameron, James Allen

    The second virial coefficient of He('3) gas and the absolute temperature of the gas were determined at five different temperatures below 1.3 K. The technique used involved measuring pressure and density simultaneously at different points along on isotherm and using the virial equation to determine the temperature and the second virial coefficient. The results are in good agreement with empirical calculations of the second virial coefficient which are based on measurements made at higher temperatures. The measurements of temperature, while only known to within (+OR-)1.5 mK, confirm the widespread belief that the T(,62) temperature scale is in error by several mK. Pressure and density were measured in-situ, using superconducting microwave cavities. These eliminate many sources of error which have in the past made measurements inaccurate below 1.5 K. The density and pressure could be related to changes in the resonant frequencies of the cavities. The frequency of one cavity, which contained the He('3) gas was proportional to the dielectric constant of the gas. The Clausius-Mossotti relationship was used to determine the density as a function of the dielectric constant. The pressure was measured using a reentrant cavity with a flexible diaphragm forming one end wall. The pressure of the gas flexed this diaphragm, changing the frequency of the cavity. A room temperature mercury manometer was used to provide a frequency vs. pressure calibration of this cavity.

  17. Polarization of the light from the 3P(1)-2S(1) transition in proton beam excited helium. Ph.D. Thesis; [target gas pressure effects

    NASA Technical Reports Server (NTRS)

    Weinhous, M. S.

    1973-01-01

    Measurements of the polarization of the light from the 3 1p-2 1s transition in proton beam excited Helium have shown both a proton beam energy and Helium target gas pressure dependence. Results for the linear polarization fraction range from +2.6% at 100 keV proton energy to -5.5% at 450 keV. The zero crossover occurs at approximately 225 keV. This is in good agreement with other experimental work in the field, but in poor agreement with theoretical predictions. Measurements at He target gas pressures as low as .01 mtorr show that the linear polarization fraction is still pressure dependent at .01 mtorr.

  18. Design and development of a helium injection system to improve external leakage detection during liquid nitrogen immersion tests

    NASA Astrophysics Data System (ADS)

    Townsend, Andrew; Mishra, Rakesh

    2016-10-01

    The testing of assemblies for use in cryogenic systems commonly includes evaluation at or near operating (therefore cryogenic) temperature. Typical assemblies include valves and pumps for use in liquid oxygen-liquid hydrogen rocket engines. One frequently specified method of cryogenic external leakage testing requires the assembly, pressurized with gaseous helium (GHe), be immersed in a bath of liquid nitrogen (LN2) and allowed to thermally stabilize. Component interfaces are then visually inspected for leakage (bubbles). Unfortunately the liquid nitrogen will be boiling under normal, bench-top, test conditions. This boiling tends to mask even significant leakage. One little known and perhaps under-utilized property of helium is the seemingly counter-intuitive thermodynamic property that when ambient temperature helium is bubbled through boiling LN2 at a temperature of -195.8 °C, the temperature of the liquid nitrogen will reduce. This paper reports on the design and testing of a novel proof-of-concept helium injection control system confirming that it is possible to reduce the temperature of an LN2 bath below boiling point through the controlled injection of ambient temperature gaseous helium and then to efficiently maintain a reduced helium flow rate to maintain a stabilized liquid temperature, enabling clear visual observation of components immersed within the LN2. Helium saturation testing is performed and injection system sizing is discussed.

  19. A high-pressure van der Waals compound in solid nitrogen-helium mixtures

    NASA Technical Reports Server (NTRS)

    Vos, W. L.; Finger, L. W.; Hemley, R. J.; Hu, J. Z.; Mao, H. K.; Schouten, J. A.

    1992-01-01

    A detailed diamond anvil-cell study using synchrotron X-ray diffraction, Raman scattering, and optical microscopy has been conducted for the He-N system, with a view to the weakly-bound van der Waals molecule interactions that can be formed in the gas phase. High pressure is found to stabilize the formation of a stoichiometric, solid van der Waals compound of He(N2)11 composition which may exemplify a novel class of compounds found at high pressures in the interiors of the outer planets and their satellites.

  20. Gaseous detonations

    SciTech Connect

    Nettleton, M.A.

    1987-01-01

    Focusing predominantly on safety problems in handling combustible gas or dust mixtures with air or oxygen, the book is a reference on gaseous detonations. Topics covered include: unidimensional models, structure of detonation fronts, and interaction of a detonation with confinement.

  1. Numerical Simulations of Pressure Spikes within a Cylindrical Launch Tube due to a Bursting Helium Flask

    DTIC Science & Technology

    2011-11-09

    objective of these tests was to determine the failure mode of the hydrogen fuel flask and the extent of fragmentation damage. The test demonstrated that...the hydrogen fuel flask and the extent of fragmentation damage. The test demonstrated that the fragmentation damage to the XFC launcher tube was...Above 50 atm pressure, the system deviates from ideal gas law behavior as shown by the red curve. This curve was obtained using the Cheetah 6.0

  2. Space and time structure of helium pulsed surface-wave discharges at intermediate pressures (5-50 Torr)

    NASA Astrophysics Data System (ADS)

    Hamdan, Ahmad; Valade, Fabrice; Margot, Joëlle; Vidal, François; Matte, Jean-Pierre

    2017-01-01

    In this paper, the ignition and development of a plasma created by pulsed surface wave discharges (PSWDs) was experimentally investigated using time-resolved imaging techniques and optical spectroscopy in helium at intermediate gas pressures between 5 and 50 Torr. We found that the ionization front moves at a few km s-1 during the ignition phase and decreases to hundreds of m s-1 after only some tens of µs. Once the plasma has reached a sufficient length, a standing wave pattern is observed in the light emission of the discharge. We attribute its formation to the reflection of the surface wave on the ionization front, which results in a pattern of nodes and antinodes. We have also determined the time and space evolution of the gas temperature. It is shown that the gas temperature increases from the room temperature value to a plateau at several hundreds of degrees over a short time (typically 100 µs). These results supports those obtained by light emission imaging and also show that the standing wave pattern does not affect the gas temperature.

  3. Dielectric barrier discharges in helium at atmospheric pressure: experiments and model in the needle-plane geometry

    NASA Astrophysics Data System (ADS)

    Radu, I.; Bartnikas, R.; Wertheimer, M. R.

    2003-06-01

    We present an experimental and numerical modelling study of dielectric barrier discharges in pure, flowing helium at atmospheric pressure, in a 3.0 mm length needle-plane gap. Ultra-high speed imaging and synchronous, real-time dual detection (optical-electrical) diagnostics have been carried out. The high-voltage electrode was a hyperboloidal steel needle with a sharp point of 40 mum radius, while the grounded electrode was covered with 1.6 mm of Al2O3. The surface of the latter was either bare (case 1) or coated with ~20 nm of semiconducting graphite (case 2) or metallic aluminium (case 3), all at floating potential. Axial [z(t)] and radial [r(t)] time-evolutions (leq2 mus) of discharge propagation across the gap were found to depend very strongly upon surface charging or conduction (cases 1-3). A two-dimensional model of the needle-plane discharge, based on coupled solution of the continuity equations for electrons, ions and excited neutral particles and of Poisson's equation, was found to agree very well with the observed [r,z](t) behaviour.

  4. Evaluation of candidate Stirling engine heater tube alloys after 3500 hours exposure to high pressure doped hydrogen or helium

    NASA Technical Reports Server (NTRS)

    Misencik, J. A.; Titran, R. H.

    1984-01-01

    The heater head tubes of current prototype automotive Stirling engines are fabricated from alloy N-155, an alloy which contains 20 percent cobalt. Because the United States imports over 90 percent of the cobalt used in this country and resource supplies could not meet the demand imposed by automotive applications of cobalt in the heater head (tubes plus cylinders and regenerator housings), it is imperative that substitute alloys free of cobalt be identified. The research described herein focused on the heater head tubes. Sixteen alloys (15 potential substitutes plus the 20 percent Co N-155 alloy) were evaluated in the form of thin wall tubing in the NASA Lewis Research Center Stirling simulator materials diesel fuel fired test rigs. Tubes filled with either hydrogen doped with 1 percent CO2 or with helium at a gas pressure of 15 MPa and a temperature of 820 C were cyclic endurance tested for times up to 3500 hr. Results showed that two iron-nickel base superalloys, CG-27 and Pyromet 901 survived the 3500 hr endurance test. The remaining alloys failed by creep-rupture at times less than 3000 hr, however, several other alloys had superior lives to N-155. Results further showed that doping the hydrogen working fluid with 1 vol % CO2 is an effective means of reducing hydrogen permeability through all the alloy tubes investigated.

  5. Wound helium pressurant tank development for 2nd stage of Ariane 4 launcher

    NASA Astrophysics Data System (ADS)

    Valy, Y.; Coquet, P.

    1990-06-01

    The manufacture of a wound pressurant tank for the second stage of the Ariane 4 launcher is described. The goal of the manufacturing process is to save 26 kg per tank resulting in an overall savings of 78 kg for the second stage. This is equivalent to an extra mass payload of about 20 kg. The technical requirements of the tank are described. Development requirements and approach are outlined. Qualification standards of the design and qualification tests are described. Tank behavior is checked using acoustic emission and ultrasonic inspection.

  6. Helium leak testing of a radioactive contaminated vessel under high pressure in a contaminated environment

    SciTech Connect

    Winter, M.E.

    1996-10-01

    At ANL-W, with the shutdown of EBR-II, R&D has evolved from advanced reactor design to the safe handling, processing, packaging, and transporting spent nuclear fuel and nuclear waste. New methods of processing spent fuel rods and transforming contaminated material into acceptable waste forms are now in development. Storage of nuclear waste is a high interest item. ANL-W is participating in research of safe storage of nuclear waste, with the WIPP (Waste Isolation Pilot Plant) site in New Mexico the repository. The vessel under test simulates gas generated by contaminated materials stored underground at the WIPP site. The test vessel is 90% filled with a mixture of contaminated material and salt brine (from WIPP site) and pressurized with N2-1% He at 2500 psia. Test acceptance criteria is leakage < 10{sup -7} cc/seconds at 2500 psia. The bell jar method is used to determine leakage rate using a mass spectrometer leak detector (MSLD). The efficient MSLD and an Al bell jar replaced a costly, time consuming pressure decay test setup. Misinterpretation of test criterion data caused lengthy delays, resulting in the development of a unique procedure. Reevaluation of the initial intent of the test criteria resulted in leak tolerances being corrected and test efficiency improved.

  7. Time evolution of nanosecond runaway discharges in air and helium at atmospheric pressure

    SciTech Connect

    Yatom, S.; Vekselman, V.; Krasik, Ya. E.

    2012-12-15

    Time- and space-resolved fast framing photography was employed to study the discharge initiated by runaway electrons in air and He gas at atmospheric pressure. Whereas in the both cases, the discharge occurs in a nanosecond time scale and its front propagates with a similar velocity along the cathode-anode gap, the later stages of the discharge differ significantly. In air, the main discharge channels develop and remain in the locations with the strongest field enhancement. In He gas, the first, diode 'gap bridging' stage, is similar to that obtained in air; however, the development of the discharge that follows is dictated by an explosive electron emission from micro-protrusions on the edge of the cathode. These results allow us to draw conclusions regarding the different conductivity of the plasma produced in He and air discharges.

  8. Diagnostics and active species formation in an atmospheric pressure helium sterilization plasma source

    NASA Astrophysics Data System (ADS)

    Simon, A.; Anghel, S. D.; Papiu, M.; Dinu, O.

    2009-01-01

    Systematic spectroscopic studies and diagnostics of an atmospheric pressure radiofrequency (13.56 MHz) He plasma is presented. The discharge is an intrinsic part of the resonant circuit of the radiofrequency oscillator and was obtained using a monoelectrode type torch, at various gas flow-rates (0.1-6.0 l/min) and power levels (0-2 W). As function of He flow-rate and power the discharge has three developing stages: point-like plasma, spherical plasma and ellipsoidal plasma. The emission spectra of the plasma were recorded and investigated as function of developing stages, flow-rates and plasma power. The most important atomic and molecular components were identified and their evolution was studied as function of He flow-rate and plasma power towards understanding basic mechanisms occurring in this type of plasma. The characteristic temperatures (vibrational Tvibr, rotational Trot and excitation Texc) and the electron number density (ne) were determined.

  9. Why Helium Ends in "-Ium"

    ERIC Educational Resources Information Center

    Jensen, William B.; Holme, Thomas; Cooper, Melanie; White, Carol

    2004-01-01

    Edward Frankland and Norman Lockyer researched upon a gaseous spectra in relation to the physical constitution of the sun and named it as "helium" (from Greek "helios" meaning "sun"). Since Lockyer apparently never formally proposed the name in print, it is not known why he chose to use a metallic end "ium".

  10. The gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide from combustion calorimetry, vapor pressure measurements, and ab initio calculations.

    PubMed

    Emel'yanenko, Vladimir N; Verevkin, Sergey P; Heintz, Andreas

    2007-04-04

    Ionic liquids are attracting growing interest as alternatives to conventional molecular solvents. Experimental values of vapor pressure, enthalpy of vaporization, and enthalpy of formation of ionic liquids are the key thermodynamic quantities, which are required for the validation and development of the molecular modeling and ab initio methods toward this new class of solvents. In this work, the molar enthalpy of formation of the liquid 1-butyl-3-methylimidazolium dicyanamide, 206.2 +/- 2.5 kJ.mol-1, was measured by means of combustion calorimetry. The molar enthalpy of vaporization of 1-butyl-3-methylimidazolium dicyanamide, 157.2 +/- 1.1 kJ.mol-1, was obtained from the temperature dependence of the vapor pressure measured using the transpiration method. The latter method has been checked with measurements of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, where data are available from the effusion technique. The first experimental determination of the gaseous enthalpy of formation of the ionic liquid 1-butyl-3-methylimidazolium dicyanamide, 363.4 +/- 2.7 kJ.mol-1, from thermochemical measurements (combustion and transpiration) is presented. Ab initio calculations of the enthalpy of formation in the gaseous phase have been performed for 1-butyl-3-methylimidazolium dicyanamide using the G3MP2 theory. Excellent agreement with experimental results has been observed. The method developed opens a new way to obtain thermodynamic properties of ionic liquids which have not been available so far.

  11. Selective fibronectin adsorption against albumin and enhanced stem cell attachment on helium atmospheric pressure glow discharge treated titanium

    NASA Astrophysics Data System (ADS)

    Han, Inho; Vagaska, Barbora; Joo Park, Bong; Lee, Mi Hee; Jin Lee, Seung; Park, Jong-Chul

    2011-06-01

    Successful tissue integration of implanted medical devices depends on appropriate initial cellular response. In this study, the effect of helium atmospheric pressure glow discharge (He-APGD) treatment of titanium on selective protein adsorption and the initial attachment processes and focal adhesion formation of osteoprogenitor cells and stem cells were examined. Titanium disks were treated in a self-designed He-APGD system. Initial attachment of MC3T3-E1 mouse pre-osteoblasts and human mesenchymal stem cells (MSCs) was evaluated by MTT assay and plasma membrane staining followed by morphometric analysis. Fibronectin adsorption was investigated by Enzyme-Linked ImmunoSorbant Assay. MSCs cell attachment to treated and non-treated titanium disks coated with different proteins was verified also in serum-free culture. Organization of actin cytoskeleton and focal adhesions was evaluated microscopically. He-APGD treatment effectively modified the titanium surfaces by creating a super-hydrophilic surface, which promoted selectively higher adsorption of fibronectin, a protein of critical importance for cell/biomaterial interaction. In two different types of cells, the He-APGD treatment enhanced the number of attaching cells as well as their attachment area. Moreover, cells had higher organization of actin cytoskeleton and focal adhesions. Faster acceptance of the material by the progenitor cells in the early phases of tissue integration after the implantation may significantly reduce the overall healing time; therefore, titanium treatment with He-APGD seems to be an effective method of surface modification of titanium for improving its tissue inductive properties.

  12. DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

    NASA Astrophysics Data System (ADS)

    Wang, Xingxing; Shashurin, Alexey

    2017-02-01

    This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

  13. Measurement of scintillation and ionization yield with high-pressure gaseous mixtures of Xe and TMA for improved neutrinoless double beta decay and dark matter searches

    NASA Astrophysics Data System (ADS)

    Nakajima, Y.; Goldschmidt, A.; Matis, H. S.; Nygren, D.; Oliveira, C.; Renner, J.

    2015-11-01

    Liquid Xe TPCs are among the most popular choices for double beta decay and WIMP dark matter searches. Gaseous Xe has intrinsic advantages when compared to Liquid Xe, specifically, tracking capability and better energy resolution for double beta decay searches. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which are expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a more easily detectable wavelength (300 nm). These features may provide better tracking and energy resolution for double-beta decay searches. They are also expected to enhance columnar recombination for nuclear recoils, which can be used for searches for WIMP dark matter with directional sensitivity. We constructed a test ionization chamber and successfully measured scintillation and ionization yields at high precision with various Xe and TMA mixtures and pressures. We observed the Penning effect and an increase in recombination with the addition of TMA. However, many undesired features for dark matter searches, such as strong suppression of the scintillation light and no sign of recombination light, were also found. This work has been carried out within the context of the NEXT collaboration.

  14. Three-electrode low pressure discharge apparatus and method for uniform ionization of gaseous media. [CO/sub 2/ laser oscillator and pulse smoother

    DOEpatents

    McLellan, E.J.

    1980-10-17

    Uniform, transverse electrical discharges are produced in gaseous media without the necessity of switching the main discharge voltage with an external device which carries the entire discharge current. A three-electrode low pressure discharge tube is charged across its anode and cathode to below breakdown voltage using a dc voltage source. An array of resistors or capacitors can be made to discharge to the wire screen anode by means of a low energy high voltage pulse circuit producing sufficient preionization in the region between the anode and cathode to initiate and control the main discharge. The invention has been demonstrated to be useful as a CO/sub 2/ laser oscillator and pulse-smoother. It can be reliably operated in the sealed-off mode.

  15. The Gaseous Explosive Reaction : the Effect of Pressure on the Rate of Propagation of the Reaction Zone and upon the Rate of Molecular Transformation

    NASA Technical Reports Server (NTRS)

    Stevens, F W

    1932-01-01

    This study of gaseous explosive reaction has brought out a number of important fundamental characteristics of the explosive reaction indicating that the basal processes of the transformation are much simpler and corresponds more closely to the general laws and principles of ordinary transformations than is usually supposed. The report calls attention to the point that the rate of molecular transformation within the zone was found in all cases to be proportional to pressure, that the transformation within the zone is the result of binary impacts. This result is of unusual interest in the case of the reaction of heavy hydrocarbon fuels and the reaction mechanism proposed by the recent kinetic theory of chain reactions.

  16. Investigation on streamers propagating into a helium jet in air at atmospheric pressure: Electrical and optical emission analysis

    NASA Astrophysics Data System (ADS)

    Gazeli, K.; Svarnas, P.; Vafeas, P.; Papadopoulos, P. K.; Gkelios, A.; Clément, F.

    2013-09-01

    The plasma produced due to streamers guided by a dielectric tube and a helium jet in atmospheric air is herein studied electrically and optically. Helium streamers are produced inside the dielectric tube of a coaxial dielectric-barrier discharge and, upon exiting the tube, they propagate into the helium jet in air. The axisymmetric velocity field of the neutral helium gas while it penetrates the air is approximated with the PISO algorithm. At the present working conditions, turbulence helium flow is avoided. The system is driven by sinusoidal high voltage of variable amplitude (0-11 kV peak-to-peak) and frequency (5-20 kHz). It is clearly shown that a prerequisite for streamer development is a continuous flow of helium, independently of the sustainment or not of the dielectric-barrier discharge. A parametric study is carried out by scanning the range of the operating parameters of the system and the optimal operational window for the longest propagation path of the streamers in air is determined. For this optimum, the streamer current impulses and the spatiotemporal progress of the streamer UV-visible emission are recorded. The streamer mean propagation velocity is as well measured. The formation of copious reactive emissive species is then considered (in terms of intensity and rotational temperatures), and their evolution along the streamer propagation path is mapped. The main claims of the present work contribute to the better understanding of the physicochemical features of similar systems that are currently applied to various interdisciplinary engineering fields, including biomedicine and material processing.

  17. Potential Danger of Pre-Pump Clamping on Negative Pressure-Associated Gaseous Microemboli Generation During Extracorporeal Life Support--An In Vitro Study.

    PubMed

    Wang, Shigang; Chin, Brian J; Gentile, Frank; Kunselman, Allen R; Palanzo, David; Ündar, Akif

    2016-01-01

    The objectives of this study were to investigate the relationship between revolution speed of a conventional centrifugal pump and negative pressure at the inlet of the pump by clamping the tubing upstream of the pump, and to verify whether negative pressure leads to gaseous microemboli (GME) production in a simulated adult extracorporeal life support (ECLS) system. The experimental circuit, including a Maquet Rotaflow centrifugal pump and a Medos Hilite 7000 LT polymethyl-pentene membrane oxygenator, was primed with packed red blood cells (hematocrit 35%). Negative pressure was created in the circuit by clamping the tubing upstream of the pump for 10 s, and then releasing the clamp. An emboli detection and classification quantifier was used to record GME volume and count at pre-oxygenator and post-oxygenator sites, and pressure and flow rate data were collected using a custom-based data acquisition system. All trials were conducted at 36°C at revolution speeds of 2000-4000 rpm (500 rpm increment). The flow rates were 1092.5-4708.4 mL/min at the revolution speeds of 2000-4000 rpm. Higher revolution speed generated higher negative pressure at the pre-pump site when clamping the tubing upstream of the pump (-108.3 ± 0.1 to -462.0 ± 0.5 mm Hg at 2000-4000 rpm). Moreover, higher negative pressure was associated with a larger number and volume of GME at pre-oxygenator site after de-clamp (GME count 10,573 ± 271 at pre-oxygenator site at 4000 rpm). The results showed that there was a potential danger of delivering GME to the patient when clamping pre-pump tubing during ECLS using a centrifugal pump. Our results warrant further clinical studies to investigate this phenomenon.

  18. Promoted combustion of nine structural metals in high-pressure gaseous oxygen - A comparison of ranking methods

    NASA Technical Reports Server (NTRS)

    Steinberg, Theodore A.; Rucker, Michelle A.; Beeson, Harold D.

    1989-01-01

    The 316, 321, 440C, and 17-4 PH stainless steels, as well as Inconel 600, Inconel 718, Waspaloy, Monel 400, and Al 2219, have been evaluated for relative nonflammability in a high-pressure oxygen environment with a view to the comparative advantages of four different flammability-ranking methods. The effects of changes in test pressure, sample diameter, promoter type, and sample configuration on ranking method results are evaluated; ranking methods employing velocity as the primary ranking criterion are limited by diameter effects, while those which use extinguishing pressure are nonselective for metals with similar flammabilities.

  19. Generation of reactive oxygen and nitrogen species and its effects on DNA damage in lung cancer cells exposed to atmospheric pressure helium/oxygen plasma jets

    NASA Astrophysics Data System (ADS)

    Chung, Tae Hun; Joh, Hea Min; Kim, Sun Ja; Choi, Ji Ye; Kang, Tae-Hong

    2016-09-01

    We investigated the effects of the operating parameters on the generation of reactive oxygen and nitrogen species (RONS) in the gas and liquid phases exposed to atmospheric pressure a pulsed-dc helium plasma jets. The densities of reactive species including OH radicals were obtained at the plasma-liquid surface and inside the plasma-treated liquids using ultraviolet absorption spectroscopy and chemical probe method. And the nitrite concentration was detected by Griess assay. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas and liquids. Exposure of plasma to cancer cells increases the cellular levels of RONS, which has been linked to apoptosis and the damage of cellular proteins, and may also indirectly cause structural damage to DNA. To identify the correlation between the production of RONS in cells and plasmas, various assay analyses were performed on plasma treated human lung cancer cells (A549) cells. In addition, the effect of additive oxygen gas on the plasma-induced oxidative stress in cancer cells was investigated. It was observed that DNA damage was significantly increased with helium/oxygen plasma compared to with pure helium plasma.

  20. Explosion bomb measurements of ethanol-air laminar gaseous flame characteristics at pressures up to 1.4 MPa

    SciTech Connect

    Bradley, D.; Lawes, M.; Mansour, M.S.

    2009-07-15

    The principal burning characteristics of a laminar flame comprise the fuel vapour pressure, the laminar burning velocity, ignition delay times, Markstein numbers for strain rate and curvature, the stretch rates for the onset of flame instabilities and of flame extinction for different mixtures. With the exception of ignition delay times, measurements of these are reported and discussed for ethanol-air mixtures. The measurements were in a spherical explosion bomb, with central ignition, in the regime of a developed stable, flame between that of an under or over-driven ignition and that of an unstable flame. Pressures ranged from 0.1 to 1.4 MPa, temperatures from 300 to 393 K, and equivalence ratios were between 0.7 and 1.5. It was important to ensure the relatively large volume of ethanol in rich mixtures at high pressures was fully evaporated. The maximum pressure for the measurements was the highest compatible with the maximum safe working pressure of the bomb. Many of the flames soon became unstable, due to Darrieus-Landau and thermo-diffusive instabilities. This effect increased with pressure and the flame wrinkling arising from the instabilities enhanced the flame speed. Both the critical Peclet number and the, more rational, associated critical Karlovitz stretch factor were evaluated at the onset of the instability. With increasing pressure, the onset of flame instability occurred earlier. The measured values of burning velocity are expressed in terms of their variations with temperature and pressure, and these are compared with those obtained by other researchers. Some comparisons are made with the corresponding properties for iso-octane-air mixtures. (author)

  1. Comparative results of autogenous ignition temperature measurements by ASTM G 72 and pressurized scanning calorimetry in gaseous oxygen

    NASA Technical Reports Server (NTRS)

    Bryan, C. J.; Lowrie, R.

    1986-01-01

    The autogenous ignition temperature of four materials was determined by ASTM (G 72) and pressurized differential scanning calorimetry at 0.68-, 3.4-, and 6.8-MPa oxygen pressure. All four materials were found to ignite at lower temperatures in the ASTM method. The four materials evaluated in this program were Neoprene, Vespel SP-21, Fluorel E-2160, and nylon 6/6.

  2. Thermodynamics of a solar mixture of molecular hydrogen and helium at high pressure. [for Jupiter atmospheric model

    NASA Technical Reports Server (NTRS)

    Slattery, W. L.; Hubbard, W. B.

    1976-01-01

    The thermodynamic properties of a model molecular hydrogen and helium mixture are calculated in the strongly interacting region of 0.005 to 0.3 per cu cm for a range of temperatures that are of interest for the envelopes of the Jovian planets. Computed adiabats fit the gravity data and boundary conditions from model atmospheres of Jupiter.

  3. Flux of OH and O radicals onto a surface by an atmospheric-pressure helium plasma jet measured by laser-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Yonemori, Seiya; Ono, Ryo

    2014-03-01

    The atmospheric-pressure helium plasma jet is of emerging interest as a cutting-edge biomedical device for cancer treatment, wound healing and sterilization. Reactive oxygen species such as OH and O radicals are considered to be major factors in the application of biological plasma. In this study, density distribution, temporal behaviour and flux of OH and O radicals on a surface are measured using laser-induced fluorescence. A helium plasma jet is generated by applying pulsed high voltage of 8 kV with 10 kHz using a quartz tube with an inner diameter of 4 mm. To evaluate the relation between the surface condition and active species production, three surfaces are used: dry, wet and rat skin. When the helium flow rate is 1.5 l min-1, radial distribution of OH density on the rat skin surface shows a maximum density of 1.2 × 1013 cm-3 at the centre of the plasma-mediated area, while O atom density shows a maximum of 1.0 × 1015 cm-3 at 2.0 mm radius from the centre of the plasma-mediated area. Their densities in the effluent of the plasma jet are almost constant during the intervals of the discharge pulses because their lifetimes are longer than the pulse interval. Their density distribution depends on the helium flow rate and the surface humidity. With these results, OH and O production mechanisms in the plasma jet and their flux onto the surface are discussed.

  4. Behavior of metallic materials between 550 and 870/sup 0/C in high-temperature gas-cooled reactor helium under pressures of 2 and 50 bar

    SciTech Connect

    Cappelaere, M.; Perrot, M.; Sannier, J.

    1984-08-01

    In order to estimate the influence of the helium pressure on the corrosion of ferritic and austenitic materials, tests were carried out under 2 absolute bar in a circuit without helium recirculation and under 50 bar in the AIDA loop. In both cases the partial pressures of impurities were 1.500, 50, 450, and 50 ..mu..atm for H/sub 2/, H/sub 2/O, CO, and CH/sub 4/, respectively. The interruption of the French high-temperature gas-cooled reactor RandD program has only produced limited results: 1. At 650/sup 0/C the behavior of 11% chromium ferritic steel HT 9, Types 304 and 316 austenitic steels, and Incoloy Alloy 800H is excellent; the oxidation rates are low and decrease with time. 2. At 750 and 870/sup 0/C, Hastelloy-X offers better resistance to external and intergranular oxidation than alloys 800H and Inconel-617. 3. At these three temperatures, the oxidation kinetics are appreciably faster under a pressure of 50 bar than under 2 bar. 4. Whereas carbon steel is subject to decarburization at 550/sup 0/C, a carburization phenomenon is observed for alloys 800H, Inconel-617, and Hastelloy-X at 750 and especially at 870/sup 0/C. 5. As for the influence of the initial surface preparation, mechanically polished specimens generally present a lower oxidation rate than those polished electrochemically.

  5. Voltage and Pressure Scaling of Streamer Dynamics in a Helium Plasma Jet With N2 CO-Flow (Postprint)

    DTIC Science & Technology

    2014-08-14

    of measurements since it allowed us to measure streamer scaling properties over a wide voltage range with- out surface flashover in our configuration...allows the formation of a non-stochastic active discharge extending beyond the anodic electrode uses a capillary dielectric tube with helium gas flow...of discharge behaves like a cath- ode directed streamer propagation. This plasma jet uses a dielectric barrier configuration with annular anode

  6. Laminar Heat-Transfer and Pressure-Distribution Studies on a Series of Reentry Nose Shapes at a Mach Number of 19.4 in Helium

    NASA Technical Reports Server (NTRS)

    Wagner, Richard D., Jr.; Pine, W. Clint; Henderson, Arthur, Jr.

    1961-01-01

    An experimental investigation has been conducted in the 2-inch helium tunnel at the Langley Research Center at a Mach number of 19.4 to determine the pressure distributions and heat-transfer characteristics of a family of reentry nose shapes. The pressure and heat-transfer-rate distributions on the nose shapes are compared with theoretical predictions to ascertain the limitations and validity of the theories at hypersonic speeds. The experimental results were found to be adequately predicted by existing theories. Two of the nose shapes were tested with variable-length flow-separation spikes. The results obtained by previous investigators of spike-nose bodies were found to prevail at the higher Mach number of the present investigation.

  7. Evaluation of Capiox FX05 oxygenator with an integrated arterial filter on trapping gaseous microemboli and pressure drop with open and closed purge line.

    PubMed

    Qiu, Feng; Peng, Sophia; Kunselman, Allen; Ündar, Akif

    2010-11-01

    Gaseous microemboli (GME) remain a challenge for cardiopulmonary bypass (CPB) because there is a positive correlation between microemboli exposure during CPB and postoperative neurological injury. Thus, minimizing the number of GME delivered to pediatric patients undergoing CPB procedures would lead to better clinical outcomes. In this study, we used a simulated CPB model to evaluate the effectiveness of capturing GME and the degree of membrane pressure drop for a new membrane oxygenator, Capiox Baby FX05 (Terumo Corporation,Tokyo, Japan), which has an integrated arterial filter with open and closed purge line.We used identical components in this study as our clinical CPB circuit. Three emboli detection and classification quantifier transducers were placed at prepump, preoxygenator, and postoxygenator sites in the circuit.Two flow probes as well as three pressure transducers were placed upstream and downstream of the oxygenator. The system was primed with human blood titrated to 30% hematocrit with Lactated Ringer’s solution.A bolus of air (1 mL) was injected in the prepump site under nonpulsatile perfusion mode at three flow rates (500,750, and 1000 mL/min) and with the purge line either open or closed. Six trials were performed for each unique set-up for a total of 36 trials.All trials were conducted at 35°C. The circuit pressure was kept constant at 100 mm Hg. Both the size and quantity of microemboli detected at postoxygenator site were recorded for 5 min postair injection. It was found that total counts of GME were significantly reduced with the purge line open when compared to keeping the purge line closed (P < 0.0001 at 1000 mL/min). At all flow rates, most of the GME were under 20 microns in size. In terms of microemboli greater than 40 microns, the counts were significantly higher with the purge line closed compared to keeping the purge line open at flow rates of 750 mL/min and 1000 mL/min (P < 0.01). At all flow rates,there is a tiny difference of less

  8. Thermal decomposition of gaseous ammonium nitrate at low pressure: kinetic modeling of product formation and heterogeneous decomposition of nitric acid.

    PubMed

    Park, J; Lin, M C

    2009-12-03

    The thermal decomposition of ammonium nitrate, NH(4)NO(3) (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH(4)NO(3) at 423 K was proposed to produce equal amounts of NH(3) and HNO(3), followed by the decomposition reaction of HNO(3), HNO(3) + M --> OH + NO(2) + M (where M = third-body and reactor surface). The absolute yields of N(2), N(2)O, H(2)O, and NH(3), which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH(3)-NO(2) (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO(3) itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO(3) in our kinetic modeling. The heterogeneous decomposition rate of HNO(3), HNO(3) + (B(2)O(3)/SiO(2)) --> OH + NO(2) + (B(2)O(3)/SiO(2)), was determined by varying its rate to match the modeled result to the measured concentrations of NH(3) and H(2)O; the rate could be represented by k(2b) = 7.91 x 10(7) exp(-12 600/T) s(-1), which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO(3) decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

  9. Thermal Decomposition of Gaseous Ammonium Nitrate at Low Pressure: Kinetic Modeling of Product Formation and Heterogeneous Decomposition of Nitric Acid

    NASA Astrophysics Data System (ADS)

    Park, J.; Lin, M. C.

    2009-10-01

    The thermal decomposition of ammonium nitrate, NH4NO3 (AN), in the gas phase has been studied at 423-56 K by pyrolysis/mass spectrometry under low-pressure conditions using a Saalfeld reactor coated with boric acid. The sublimation of NH4NO3 at 423 K was proposed to produce equal amounts of NH3 and HNO3, followed by the decomposition reaction of HNO3, HNO3 + M → OH + NO2 + M (where M = third-body and reactor surface). The absolute yields of N2, N2O, H2O, and NH3, which can be unambiguously measured and quantitatively calibrated under a constant pressure at 5-6.2 torr He are kinetically modeled using the detailed [H,N,O]-mechanism established earlier for the simulation of NH3-NO2 (Park, J.; Lin, M. C. Technologies and Combustion for a Clean Environment. Proc. 4th Int. Conf. 1997, 34-1, 1-5) and ADN decomposition reactions (Park, J.; Chakraborty, D.; Lin, M. C. Proc. Combust. Inst. 1998, 27, 2351-2357). Since the homogeneous decomposition reaction of HNO3 itself was found to be too slow to account for the consumption of reactants and the formation of products, we also introduced the heterogeneous decomposition of HNO3 in our kinetic modeling. The heterogeneous decomposition rate of HNO3, HNO3 + (B2O3/SiO2) → OH + NO2 + (B2O3/SiO2), was determined by varying its rate to match the modeled result to the measured concentrations of NH3 and H2O; the rate could be represented by k2b = 7.91 × 107 exp(-12 600/T) s-1, which appears to be consistent with those reported by Johnston and co-workers (Johnston, H. S.; Foering, L.; Tao, Y.-S.; Messerly, G. H. J. Am. Chem. Soc. 1951, 73, 2319-2321) for HNO3 decomposition on glass reactors at higher temperatures. Notably, the concentration profiles of all species measured could be satisfactorily predicted by the existing [H,N,O]-mechanism with the heterogeneous initiation process.

  10. Simulation of a non-equilibrium helium plasma bullet emerging into oxygen at high pressure (250-760 Torr) and interacting with a substrate

    NASA Astrophysics Data System (ADS)

    Yan, Wen; Economou, Demetre J.

    2016-09-01

    A two-dimensional computational study of a plasma bullet emanating from a helium gas jet in oxygen ambient at high pressure (250-760 Torr) was performed, with emphasis on the bullet interaction with a substrate. Power was applied in the form of a trapezoidal +5 kV pulse lasting 150 ns. A neutral gas transport model was employed to predict the concentration distributions of helium and oxygen in the system. These were then used in a plasma dynamics model to investigate the characteristics of the plasma bullet during its propagation and interaction with a substrate. Upon ignition, the discharge first propagated as a surface wave along the inner wall of the containing tube, and then exited the tube with a well-defined ionization front (streamer or plasma bullet). The plasma bullet evolved from a hollow (donut-shaped) feature to one where the maximum of ionization was on axis. The bullet propagated in the gap between the tube exit and the substrate with an average speed of ˜2 × 105 m/s. Upon encountering a metal substrate, the bullet formed a conductive channel to the substrate. Upon encountering a dielectric substrate, the bullet turned into an ionization wave propagating radially along the substrate surface. For a conductive substrate, the radial species fluxes to the surface peaked on the symmetry axis. For a dielectric substrate, a ring-shaped flux distribution was observed. The "footprint" of plasma-surface interaction increased either by decreasing the gap between tube exit and substrate, decreasing the relative permittivity of an insulating substrate, or decreasing pressure. As the system pressure was lowered from 760 to 250 Torr, the discharge was initiated earlier, and the plasma bullet propagation speed increased. A reverse electric field developed during the late stages of the ramp-down of the pulse, which accelerated electrons forming a brief backward discharge.

  11. Gaseous Detectors

    NASA Astrophysics Data System (ADS)

    Titov, Maxim

    Since long time, the compelling scientific goals of future high-energy physics experiments were a driving factor in the development of advanced detector technologies. A true innovation in detector instrumentation concepts came in 1968, with the development of a fully parallel readout for a large array of sensing elements - the Multi-Wire Proportional Chamber (MWPC), which earned Georges Charpak a Nobel prize in physics in 1992. Since that time radiation detection and imaging with fast gaseous detectors, capable of economically covering large detection volumes with low mass budget, have been playing an important role in many fields of physics. Advances in photolithography and microprocessing techniques in the chip industry during the past decade triggered a major transition in the field of gas detectors from wire structures to Micro-Pattern Gas Detector (MPGD) concepts, revolutionizing cell-size limitations for many gas detector applications. The high radiation resistance and excellent spatial and time resolution make them an invaluable tool to confront future detector challenges at the next generation of colliders. The design of the new micro-pattern devices appears suitable for industrial production. Novel structures where MPGDs are directly coupled to the CMOS pixel readout represent an exciting field allowing timing and charge measurements as well as precise spatial information in 3D. Originally developed for the high-energy physics, MPGD applications have expanded to nuclear physics, photon detection, astroparticle and neutrino physics, neutron detection, and medical imaging.

  12. Mechanism of bullet-to-streamer transition in water surface incident helium atmospheric pressure plasma jet (APPJ)

    NASA Astrophysics Data System (ADS)

    Yoon, Sung-Young; Kim, Gon-Ho; Kim, Su-Jeong; Bae, Byeongjun; Kim, Seong Bong; Ryu, Seungmin; Yoo, Suk Jae

    2016-09-01

    The mechanism of bullet to streamer transition of helium-APPJ bullet on the electrolyte surface was investigated. The APPJ was discharged in pin-to-ring DBD reactor system with helium gas by applying the ac-driven voltage at a frequency of 10 kHz. The water evaporation was controlled via saline temperature. The temporal- and 2-dimensional spatially- resolved plasma properties are monitored by optical diagnostics. During the APPJ bullet propagation from reactor to electrolyte surface, the transition of bullet from streamer was recognized from the high speed image, hydrogen beta emission line, and bullet propagation speed. The He metastable species density profiles from the tunable diode laser absorption spectroscopy (TDLAS) showed the metastable lost the energy near electrolyte surface. It is found that the bullet transited to streamer when the water fraction reached to 29%. This can be fascinating result to study the plasma physics liquid surface, non-fixed boundary. Acknowledgements: This work was partly supported by R&D Program of `Plasma Advanced Technology for Agriculture and Food (Plasma Farming)' through the National Fusion Research Institute of Korea (NFRI) funded by the Government fund was carried out as part.

  13. Measuring scattering lengths of gaseous samples

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Black, T. C.; Haun, R.; Pushin, D. A.; Shahi, C. B.; Weitfeldt, F. E.

    2016-03-01

    Neutron interferometry represents one of the most precise techniques for measuring the coherent scattering lengths (bc) of particular nuclear isotopes. Currently bc for helium-4 is known only to 1% relative uncertainty; a factor of ten higher than precision measurements of other light isotopes. Scattering lengths are measured using a neutron interferometer and by comparing the phase shift a neutron acquires as it passes through a gaseous sample relative to that of a neutron passing through vacuum. The density of the gas is determined by continuous monitoring of the sample's temperature and pressure. Challenges for these types of experiments include achieving the necessary long-term phase stability and accurate determination of the phase shift caused by the aluminum cell used to hold the gas; a phase shift many times greater than that of the sample. The present status on the effort to measure the n-4He scattering length at the NIST center for Neutron Research will be given. Financial support provided by the NSERC `Create' and `Discovery' programs, CERC, NIST and NSF Grant PHY-1205342.

  14. Practical protein removal using atmospheric-pressure helium plasma for densely packed gold nanoparticle arrays assembled by ferritin-based encapsulation/transport system

    NASA Astrophysics Data System (ADS)

    Hashimoto, Tatsuya; Zettsu, Nobuyuki; Zheng, Bin; Fukuta, Megumi; Yamashita, Ichiro; Uraoka, Yukiharu; Watanabe, Heiji

    2012-08-01

    We propose using atmospheric-pressure helium (AP He) plasma to efficiently remove the ferritin protein shells surrounding gold nanoparticles (GNPs). The high density GNPs assembled on a substrate by using a ferritin-based encapsulation/transport system were exposed to He radicals with a high internal energy to decompose their outer protein shells. In contrast to the conventional methods, AP-plasma treatment was found to suppress the aggregation of adjacent GNPs and produce densely packed and isolated GNP arrays. Consequently, we obtained an intense and sharp surface plasmon band from the plasma-treated GNP arrays. The clear response of their plasmonic behavior according to a refractive index of the surrounding media demonstrated that the proposed method had a significant advantage when fabricating GNP-based plasmonic devices.

  15. Electron density change of atmospheric-pressure plasmas in helium flow depending on the oxygen/nitrogen ratio of the surrounding atmosphere

    NASA Astrophysics Data System (ADS)

    Tomita, Kentaro; Urabe, Keiichiro; Shirai, Naoki; Sato, Yuta; Hassaballa, Safwat; Bolouki, Nima; Yoneda, Munehiro; Shimizu, Takahiro; Uchino, Kiichiro

    2016-06-01

    Laser Thomson scattering was applied to an atmospheric-pressure plasma produced in a helium (He) gas flow for measuring the spatial profiles of electron density (n e) and electron temperature (T e). Aside from the He core flow, the shielding gas flow of N2 or synthesized air (\\text{N}2:\\text{O}2 = 4:1) surrounding the He flow was introduced to evaluate the effect of ambient gas components on the plasma parameters, eliminating the effect of ambient humidity. The n e at the discharge center was 2.7 × 1021 m-3 for plasma generated with N2/O2 shielding gas, 50% higher than that generated with N2 shielding.

  16. Growth process of hydrogenated amorphous carbon films synthesized by atmospheric pressure plasma enhanced CVD using nitrogen and helium as a dilution gas

    NASA Astrophysics Data System (ADS)

    Mori, Takanori; Sakurai, Takachika; Sato, Taiki; Shirakura, Akira; Suzuki, Tetsuya

    2016-04-01

    Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N2) and helium (He) at various pulse frequencies. The C2H2/N2 film showed cauliflower-like-particles that grew bigger with the increase in film’s thickness. At 5 kHz, the film with a thickness of 2.7 µm and smooth surface was synthesized. On the other hand, the films synthesized from C2H2/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37 µm with a smooth surface.

  17. Effect of O2 additive on spatial uniformity of atmospheric-pressure helium plasma jet array driven by microsecond-duration pulses

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Shao, Tao; Zhou, Yixiao; Fang, Zhi; Yan, Ping; Yang, Wenjin

    2014-07-01

    Plasma jet array is a promising device for producing low-temperature plasma at atmospheric pressure. In our letter, the effect of O2 additive on spatial uniformity of one-dimensional helium plasma jet array is described. The length of the plasma jet in the middle of the array before the injection of O2 additive is less than that on the edges of the array. However, when a small amount of O2 additive is injected into the plasma jet array, the length increases and becomes approximately the same as the length of the plasma jets on the edges of the array. The improvement of spatial uniformity of the plasma jet array is due to the enhancement of the Penning ionization in the plasma jets caused by O2 additive. Too much quantity of O2 additive, however, may lead to discharge quenching in the plasma jet array.

  18. Two-dimensional numerical study of two counter-propagating helium plasma jets in air at atmospheric pressure

    SciTech Connect

    Yan, Wen; Sang, Chaofeng; Wang, Dezhen; Liu, Fucheng

    2014-06-15

    In this paper, a computational study of two counter-propagating helium plasma jets in ambient air is presented. A two-dimensional fluid model is applied to investigate the physical processes of the two plasma jets interaction (PJI) driven by equal and unequal voltages, respectively. In all studied cases, the PJI results in a decrease of both plasma bullets propagation velocity. When the two plasma jets are driven by equal voltages, they never merge but rather approach each other around the middle of the gas gap at a minimum approach distance, and the minimal distance decreases with the increase of both the applied voltages and initial electron density, but increases with the increase of the relative permittivity. When the two plasma jets are driven by unequal voltages, we observe the two plasma jets will merge at the position away from the middle of the gas gap. The effect of applied voltage difference on the PJI is also studied.

  19. Maximum Expected Wall Heat Flux and Maximum Pressure After Sudden Loss of Vacuum Insulation on the Stratospheric Observatory for Infrared Astronomy (SOFIA) Liquid Helium (LHe) Dewars

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.

    2014-01-01

    The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared observation experiments. The experiments carry sensors cooled to liquid helium (LHe) temperatures. A question arose regarding the heat input and peak pressure that would result from a sudden loss of the dewar vacuum insulation. Owing to concerns about the adequacy of dewar pressure relief in the event of a sudden loss of the dewar vacuum insulation, the SOFIA Program engaged the NASA Engineering and Safety Center (NESC). This report summarizes and assesses the experiments that have been performed to measure the heat flux into LHe dewars following a sudden vacuum insulation failure, describes the physical limits of heat input to the dewar, and provides an NESC recommendation for the wall heat flux that should be used to assess the sudden loss of vacuum insulation case. This report also assesses the methodology used by the SOFIA Program to predict the maximum pressure that would occur following a loss of vacuum event.

  20. High-pressure cryogenic seals for pressure vessels

    NASA Technical Reports Server (NTRS)

    Buggele, A. E.

    1977-01-01

    This investigation of the problems associated with reliably containing gaseous helium pressurized to 1530 bars (22 500 psi) between 4.2 K and 150 K led to the following conclusions: (1) common seal designs used in existing elevated-temperature pressure vessels are unsuitable for high-pressure cryogenic operation, (2) extrusion seal-ring materials such as Teflon, tin, and lead are not good seal materials for cryogenic high-pressure operation; and (3) several high-pressure cryogenic seal systems suitable for large-pressure vessel applications were developed; two seals required prepressurization, and one seal functioned repeatedly without any prepressurization. These designs used indium seal rings, brass or 304 stainless-steel anvil rings, and two O-rings of silicone rubber or Kel-F.

  1. Influence of gaseous hydrogen on the mechanical properties of high temperature alloys

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Tensile tests of six nickel-base and one cobalt-base alloy were conducted in 34.5 MN/sq m helium and hydrogen environments at temperatures from 297 K to 1,088 K. Mechanical properties tests of the nickel-base alloy MAR M-246 (Hf modified), in two cast conditions, were conducted in gaseous environments at temperatures from 297 K to 1,144 K and pressures from one atmosphere to 34.5 MN/sq m. The objective of this program was to obtain the mechanical properties of the various alloys proposed for use in space propulsion systems in a pure hydrogen environment at different temperatures and to compare with the mechanical properties in helium at the same conditions. All testing was conducted on solid specimens exposed to external gaseous pressure. Smooth and notched tensile properties were determined using ASTM tensile testing techniques, and creep-rupture life was determined using ASTM creep-rupture techniques. Low-cycle fatigue life was established by constant total strain and constant stress testing using smooth specimens and a closed-loop test machine.

  2. Chemistry of neutral species in the effluent of the micro atmospheric pressure plasma jet in water-helium admixture

    NASA Astrophysics Data System (ADS)

    Willems, Gert; Benedikt, Jan; von Keudell, Achim

    2016-09-01

    A thorough understanding and good control of produced neutral and charged species by cold atmospheric plasmas is essential for potential environmental and/or bio-medical applications. In this study we use the COST reference micro plasma jet (µ-APPJ), which is a radio-frequency capacitive coupled plasma source with 1 mm electrode distance, which has been operated in helium-water vapour mixture and has been studied as a potential source of hydroxyl radicals and hydrogen peroxide molecules. The water vapour concentration was up to 1.2%. Molecular Beam mass spectrometry is used as diagnostic tool. An absolute calibration of hydrogen peroxide was conducted using a double bubbler concept, because the ionization cross section for hydrogen peroxide is not available. Additionally the effluent chemistry was investigated by use of a 0D and 2D model. Absolute densities of hydrogen peroxide and hydroxyl radicals from atmospheric plasma will be presented. Their dependency on water vapour concentration in the carrier gas as well as distance to target have been investigated. The measured density is between 5E-13 cm-3 (2.4ppm) and 1.5E-14 cm-3 (7.2ppm) for both hydrogen peroxide molecules and hydroxyl radicals. The achieved results are in good agreement with other experiments.

  3. Tensile properties of V-Cr-Ti alloys after exposure in helium and low-partial-pressure oxygen environments

    SciTech Connect

    Natesan, K.; Soppet, W.K.

    1997-04-01

    A test program is in progress to evaluate the effect of oxygen at low pO{sub 2} on the tensile properties of V-(4-5)wt% Cr-(4-5)wt% Ti alloys. Some of the tensile specimens were precharged with oxygen at low pO{sub 2} at 500{degrees}C and reannealed in vacuum at 500{degrees}C in environments with various pO{sub 2} levels and subsequently tensile tested at room temperature. The preliminary results indicate that both approaches are appropriate for evaluating the effect of oxygen uptake on the tensile properties of the alloys. The data showed that in the relatively short-time tests conducted thus far, the maximum engineering stress slightly increased after oxygen exposure but the uniform and total elongation values exhibited significant decrease after exposure in oxygen-containing environments. The data for a specimen exposed to a helium environment were similar to those obtained in low pO{sub 2} environments.

  4. A study of density measurements in hypersonic helium tunnels using an electron beam fluorescence technique

    NASA Technical Reports Server (NTRS)

    Honaker, W. C.; Hunter, W. W., Jr.; Woods, W. C.

    1979-01-01

    A series of experiments have been conducted at Langley Research Center to determine the feasibility of using electron-beam fluorescence to measure the free-stream static density of gaseous helium flow over a wide range of conditions. These experiments were conducted in the Langley hypersonic helium tunnel facility and its 3-inch prototype. Measurements were made for a range of stagnation pressures and temperatures and produced free-stream number densities of 1.53 x 10 to the 23rd to 1.25 x 10 to the 24th molecules/cu m and static temperatures from 2 K to 80 K. The results showed the collision quenching cross section to be 4.4 x 10 to the -15th sq cm at 1 K and to have a weak temperature dependence of T to the 1/6. With knowledge of these two values, the free-stream number density can be measured quite accurately.

  5. High-temperature helium-loop facility

    SciTech Connect

    Tokarz, R.D.

    1981-09-01

    The high-temperature helium loop is a facility for materials testing in ultrapure helium gas at high temperatures. The closed loop system is capable of recirculating high-purity helium or helium with controlled impurities. The gas loop maximum operating conditions are as follows: 300 psi pressure, 500 lb/h flow rate, and 2100/sup 0/F temperature. The two test sections can accept samples up to 3.5 in. diameter and 5 ft long. The gas loop is fully instrumented to continuously monitor all parameters of loop operation as well as helium impurities. The loop is fully automated to operate continuously and requires only a daily servicing by a qualified operator to replenish recorder charts and helium makeup gas. Because of its versatility and high degree of parameter control, the helium loop is applicable to many types of materials research. This report describes the test apparatus, operating parameters, peripheral systems, and instrumentation system.

  6. A new pressure swing adsorption (PSA) process for recovery of tritium from the ITER solid ceramic breeder helium purge gas

    SciTech Connect

    Sood, S.K.; Fong, C.; Kalyanam, K.M. ); Kveton, O.K. ); Busigin, A. ); Ruthven, D.M. )

    1992-03-01

    This paper reports on Pressure Swing Adsorption (PSA), a well established industrial process for separating and purifying industrial gases, it is proposed for recovery of hydrogen isotopes from the ITER (International Thermonuclear Experimental Reactor) solid breeder He purge stream. The PSA process has an inherent advantage over a recently proposed Temperature Swing Adsorption (TSA) design because it allows much faster cycling (10 vs. 480 min.) and therefore has significantly (48 times) lower tritium inventory. The maximum tritium inventory for a 10 minute PSA cycle is less than 0.5 g of tritium, thus meeting an important safety goal of ITER. The PSA process is based on using molecular sieve 5A at 77 K, with pressure cycling from 1-2 MPa during the adsorption cycle, to a rough vacuum during regeneration. Experiments have been carried out to confirm the H{sub 2}/He adsorption isotherms on molecular sieve 5A, and to develop new data points at low H{sub 2} partial pressures and a temperature of 77 K. A dynamic simulation model has been developed to facilitate system design and optimization.

  7. LOX Tank Helium Removal for Propellant Scavenging

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2009-01-01

    System studies have shown a significant advantage to reusing the hydrogen and oxygen left in these tanks after landing on the Moon in fuel cells to generate power and water for surface systems. However in the current lander concepts, the helium used to pressurize the oxygen tank can substantially degrade fuel cell power and water output by covering the reacting surface with inert gas. This presentation documents an experimental investigation of methods to remove the helium pressurant while minimizing the amount of the oxygen lost. This investigation demonstrated that significant quantities of Helium (greater than 90% mole fraction) remain in the tank after draining. Although a single vent cycle reduced the helium quantity, large amounts of helium remained. Cyclic venting appeared to be more effective. Three vent cycles were sufficient to reduce the helium to small (less than 0.2%) quantities. Two vent cycles may be sufficient since once the tank has been brought up to pressure after the second vent cycle the helium concentration has been reduced to the less than 0.2% level. The re-pressurization process seemed to contribute to diluting helium. This is as expected since in order to raise the pressure liquid oxygen must be evaporated. Estimated liquid oxygen loss is on the order of 82 pounds (assuming the third vent cycle is not required).

  8. Effect of discharge polarity on the propagation of atmospheric-pressure helium plasma jets and the densities of OH, NO, and O radicals.

    PubMed

    Yonemori, Seiya; Ono, Ryo

    2015-06-01

    The atmospheric-pressure helium plasma jet is an emerging technology for plasma biomedical applications. In this paper, the authors focus on the effect of discharge polarity on propagation of the discharge and the densities of OH, NO, and O radicals. The plasma jet is applied to a glass surface placed on a grounded metal plate. Positive or negative voltage pulses with 25 μs duration, 8 kV amplitude, and 10 kpps repetition rate are used for the plasma jet. The plasma propagation is measured using a short-gated ICCD camera. The light emission intensity of the discharge generated at the rising phase of the voltage pulse is approximately equivalent for both polarities, while that generated during the falling phase is much higher for the negative discharge than the positive one. The shape of the discharge changes with the discharge polarity. The OH, NO, and O densities in the plasma jet are also measured for both polarities. It is found that the OH density is almost the same regardless the discharge polarity. Conversely, the negative discharge produces more O atoms and the positive discharge produces more NO molecules. These results indicate that the polarity of the discharge affects the densities of some reactive species produced in the plasma jet.

  9. Planar Reflection of Gaseous Detonations

    NASA Astrophysics Data System (ADS)

    Damazo, Jason Scott

    Pipes containing flammable gaseous mixtures may be subjected to internal detonation. When the detonation normally impinges on a closed end, a reflected shock wave is created to bring the flow back to rest. This study built on the work of Karnesky (2010) and examined deformation of thin-walled stainless steel tubes subjected to internal reflected gaseous detonations. A ripple pattern was observed in the tube wall for certain fill pressures, and a criterion was developed that predicted when the ripple pattern would form. A two-dimensional finite element analysis was performed using Johnson-Cook material properties; the pressure loading created by reflected gaseous detonations was accounted for with a previously developed pressure model. The residual plastic strain between experiments and computations was in good agreement. During the examination of detonation-driven deformation, discrepancies were discovered in our understanding of reflected gaseous detonation behavior. Previous models did not accurately describe the nature of the reflected shock wave, which motivated further experiments in a detonation tube with optical access. Pressure sensors and schlieren images were used to examine reflected shock behavior, and it was determined that the discrepancies were related to the reaction zone thickness extant behind the detonation front. During these experiments reflected shock bifurcation did not appear to occur, but the unfocused visualization system made certainty impossible. This prompted construction of a focused schlieren system that investigated possible shock wave-boundary layer interaction, and heat-flux gauges analyzed the boundary layer behind the detonation front. Using these data with an analytical boundary layer solution, it was determined that the strong thermal boundary layer present behind the detonation front inhibits the development of reflected shock wave bifurcation.

  10. Sensitive analysis of carbon, chromium and silicon in steel using picosecond laser induced low pressure helium plasma

    NASA Astrophysics Data System (ADS)

    Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Pardede, Marincan; Jobiliong, Eric; Hedwig, Rinda; Lie, Zener Sukra; Suyanto, Hery; Tjia, May On; Kurniawan, Koo Hendrik; Kagawa, Kiichiro

    2015-12-01

    An experimental study has been performed on the gas pressure and laser energy dependent variations of plasma emission intensities in Ar, He and N2 ambient gases induced by picosecond (ps) Nd-YAG laser irradiation on low alloy steel (JSS) samples. The study is aimed to demonstrate distinct advantage of using low pressure He ambient gas in combination with ps laser for the sensitive ppm level detection of C, Si and Cr emission lines in the UV-VIS spectral region. The much shorter pulses of ps laser are chosen for the effective ablation at much lower energy and for the benefit of reducing the undesirable long heating of the sample surface. It is found that the C I 247.8 nm, Fe I 253.5 nm, and Si I 251.4 nm emission lines induced by the ps laser at 15 mJ are readily detected with He ambient gas of 2.6 kPA, featuring generally sharp spectral signals with very low background. The following experimental results using samples with various concentrations of C, Si and Cr impurities are shown to produce for each of those elements a linear calibration line with extrapolated zero intercept, demonstrating the applicability for their quantitative analyses, with a preliminary estimated detection limits of 20 μg/g, 15 μg/g, and 5 μg/g, for C, Si, and Cr, respectively. The possibility of applying the same setup for concentration depth profiling is also demonstrated.

  11. Pressurant requirements for discharge of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank under both static and slosh conditions

    NASA Technical Reports Server (NTRS)

    Dewitt, R. L.; Mcintire, T. O.

    1974-01-01

    Pressurized expulsion tests were conducted to determine the effect of various physical parameters on the pressurant gas (methane, helium, hydrogen, and nitrogen) requirements during the expulsion of liquid methane from a 1.52-meter-(5-ft-) diameter spherical tank and to compare results with those predicted by an analytical program. Also studied were the effects on methane, helium, and hydrogen pressurant requirements of various slosh excitation frequencies and amplitudes, both with and without slosh suppressing baffles in the tank. The experimental results when using gaseous methane, helium, and hydrogen show that the predictions of the analytical program agreed well with the actual pressurant requirements for static tank expulsions. The analytical program could not be used for gaseous nitrogen expulsions because of the large quantities of nitrogen which can dissolve in liquid methane. Under slosh conditions, a pronounced increase in gaseous methane requirements was observed relative to results obtained for the static tank expulsions. Slight decreases in the helium and hydrogen requirements were noted under similar test conditions.

  12. Thermal conductivity of graphene nanoribbons in noble gaseous environments

    SciTech Connect

    Zhong, Wei-Rong Xu, Zhi-Cheng; Zheng, Dong-Qin; Ai, Bao-Quan

    2014-02-24

    We investigate the thermal conductivity of suspended graphene nanoribbons in noble gaseous environments using molecular dynamics simulations. It is reported that the thermal conductivity of perfect graphene nanoribbons decreases with the gaseous pressure. The decreasing is more obvious for the noble gas with large atomic number. However, the gaseous pressure cannot change the thermal conductivity of defective graphene nanoribbons apparently. The phonon spectra of graphene nanoribbons are also provided to give corresponding supports.

  13. Measurement of scintillation and ionization yield with high-pressure gaseous mixtures of Xe and TMA for improved neutrinoless double beta decay and dark matter searches

    NASA Astrophysics Data System (ADS)

    Nakajima, Y.; Goldschmidt, A.; Matis, H. S.; Miller, T.; Nygren, D. R.; Oliveira, C. A. B.; Renner, J.

    2016-03-01

    The gaseous Xenon(Xe) time projection chamber (TPC) is an attractive detector technique for neutrinoless double beta decay and WIMP dark matter searches. While it is less dense compared to Liquid Xe detectors, it has intrinsic advantages in tracking capability and better energy resolution. The performance of gaseous Xe can be further improved by molecular additives such as trimethylamine(TMA), which is expected to (1) cool down the ionization electrons, (2) convert Xe excitation energy to TMA ionizations through Penning transfer, and (3) produce scintillation and electroluminescence light in a more easily detectable wavelength (300 nm). In order to test the feasibility of the performance improvements with TMA, we made the first direct measurement of Penning and fluorescence transfer efficiency with gaseous mixtures of Xe and TMA. While we observed a Penning transfer efficiency up to ~35%, we found strong suppression of primary scintillation light with TMA. We also found that the primary scintillation light with Xe and TMA mixture can be well characterized by ~3% fluorescence transfer from Xe to TMA, with further suppression due to TMA self-quenching. No evidence of the scintillation light produced by recombination of TMA ions was found. This strong suppression of scintillation light makes dark matter searches quite challenging, while the possibility of improved neutrinoless double beta decay searches remains open. This work has been carried out within the context of the NEXT collaboration.

  14. Effects of particle size, helium gas pressure and microparticle dose on the plasma concentration of indomethacin after bombardment of indomethacin-loaded poly-L-lactic acid microspheres using a Helios gun system.

    PubMed

    Uchida, Masaki; Natsume, Hideshi; Kobayashi, Daisuke; Sugibayashi, Kenji; Morimoto, Yasunori

    2002-05-01

    We investigated the effects of the particle size of indomethacin-loaded poly-L-lactic acid microspheres (IDM-loaded PLA MS), the helium pressure used to accelerate the particles, and the bombardment dose of PLA MS on the plasma concentration of IDM after bombarding with IDM-loaded PLA MS of different particle size ranges, 20-38, 44-53 and 75-100 microm, the abdomen of hairless rats using the Helios gene gun system (Helios gun system). Using larger particles and a higher helium pressure, produced an increase in the plasma IDM concentration and the area under the plasma concentration-time curve (AUC) and resultant F (relative bioavailability with respect to intracutaneous injection) of IDM increased by an amount depending on the particle size and helium pressure. Although a reduction in the bombardment dose led to a decrease in C(max) and AUC, F increased on decreasing the bombardment dose. In addition, a more efficient F was obtained after bombarding with IDM-loaded PLA MS of 75-100 microm in diameter at each low dose in different sites of the abdomen compared with that after bolus bombardment with a high dose (dose equivalent). These results suggest that the bombardment injection of drug-loaded microspheres by the Helios gun system is a very useful tool for delivering a variety of drugs in powder form into the skin and systemic circulation.

  15. Properties of carbon-based structures synthesized in nuclear reactions induced by bremsstrahlung γ quanta with threshold energy of 10 MeV at helium pressure of 1.1 kbar

    NASA Astrophysics Data System (ADS)

    Didyk, A. Yu.; Wiśniewski, R.

    2016-07-01

    Helium gas with an initial pressure of about 1.1 kbar inside a high-pressure chamber (HeHPC) has been irradiated by bremsstrahlung γ quanta with a threshold energy of 10 MeV for 1.0 × 105 s produced by an electron-beam current of 22-24 μA. After opening the HeHPC, the residual pressure of helium is equal to 430 bar. Synthesized black foils with a variety of other objects are found inside the HeHPC. They are located on the inner surfaces of the reaction chamber made of high-purity copper (99.99%), the entrance the window of γ quanta made of beryllium bronze and a copper container of nuclear and chemical reaction products. Elemental analysis with the use of scanning electron microscopy and X-ray microprobe analysis has revealed that the foils contain predominantly carbon and small quantities of other elements from carbon to iron. The results are in good agreement with the cycle of investigations of the authors devoted to the γ-quanta irradiation of dense hydrogen and helium gases in the presence (absence) of metals in a reaction chamber.

  16. Measurement of plasma-generated RONS in the cancer cells exposed by atmospheric pressure helium plasma jet

    NASA Astrophysics Data System (ADS)

    Joh, Hea Min; Baek, Eun Jeong; Kim, Sun Ja; Chung, Tae Hun

    2015-09-01

    The plasma-induced reactive oxygen and nitrogen species (RONS) could result in cellular responses including DNA damages and apoptotic cell death. These chemical species, O, O2-,OH, NO, and NO2-,exhibit strong oxidative stress and/or trigger signaling pathways in biological cells. Each plasma-generated chemical species having biological implication should be identified and quantitatively measured. For quantitative measurement of RONS, this study is divided into three stages; plasma diagnostics, plasma-liquid interactions, plasma-liquid-cell interactions. First, the optical characteristics of the discharges were obtained by optical emission spectroscopy to identify various excited plasma species. And the characteristics of voltage-current waveforms, gas temperature, and plume length with varying control parameters were measured. Next, atmospheric pressure plasma jet was applied on the liquid. The estimated OH radical densities were obtained by ultraviolet absorption spectroscopy at the liquid surface. And NO2-is detected by Griess test and compared between the pure liquid and the cell-containing liquid. Finally, bio-assays were performed on plasma treated human lung cancer cells (A549). Intracellular ROS production was measured using DCF-DA. Among these RONS, productions of NO and OH within cells were measured by DAF-2DA and APF, respectively. The data are very suggestive that there is a strong correlation among the production of RONS in the plasmas, liquids, and cells.

  17. Helium recovery and purification at CHMFL

    NASA Astrophysics Data System (ADS)

    Li, J.; Meng, Q.; Ouyang, Z.; Shi, L.; Ai, X.; Chen, X.

    2017-02-01

    Currently, rising demand and declining reserves of helium have led to dramatic increases in the helium price. The High Magnetic Field Laboratory of Chinese Academy of Sciences (CHMFL) has made efforts since its foundation to increase the percentage of helium recovered. The piping network connects all the helium experimental facilities to the recovery system, and even exhaust ports of pressure relief valves and vacuum pumps are also connected. In each year, about 30,000 cubic meters helium gas is recovered. The recovery gas is purified, liquefied and supplied to the users again. This paper will provide details about the helium recovery and purification system at CHMFL, including system flowchart, components, problems and solutions.

  18. Thermodynamic properties of hydrogen-helium plasmas.

    NASA Technical Reports Server (NTRS)

    Nelson, H. F.

    1972-01-01

    Calculation of the thermodynamic properties of an atomic hydrogen-helium plasma for postulated conditions present in a stagnation shock layer of a spacecraft entering the atmosphere of Jupiter. These properties can be used to evaluate transport properties, to calculate convective heating, and to investigate nonequilibrium behavior. The calculations have been made for temperatures from 10,000 to 100,000 K, densities of 10 to the minus 7th and .00001 g cu cm, and three plasma compositions: pure hydrogen, 50% hydrogen/50% helium, and pure helium. The shock layer plasma consists of electrons, protons, atomic hydrogen, atomic helium, singly ionized helium, and doubly atomized helium. The thermodynamic properties which have been investigated are: pressure, average molecular weight, internal energy, enthalpy, entropy, specific heat, and isentropic speed of sound. A consistent model was used for the reduction of the ionization potential in the calculation of the partition functions.

  19. Dielectric Barrier Discharges in Helium at Atmospheric Pressure: Experiments and Model in the Needle-Plane Geometry

    NASA Astrophysics Data System (ADS)

    Radu, Ion; Bartnikas, Raymond; Wertheimer, Michael

    2002-10-01

    We present an experimental and theoretical modeling study of "dielectric barrier discharges" (DBD) at atmospheric pressure in a needle-plane configuration. Synchronous, Ultra High Speed Imaging (UHSI, using a Princeton Instruments PI-MAX 512RB Digital ICCD Camera System) and real-time dual detection (optical-electrical) diagnostics have been carried out in a flow of He. A phase-resolved synchronizing circuit was used to trigger the ICCD camera's shutter for durations varying from 2 ns up to 100 ms. All diagnostics, including the PI-MAX images, could be precisely synchronized and processed on a PC computer. The high voltage electrode was a steel needle with a sharp point of precisely-machined radius, while a thin (1.6 mm) ceramic (Al2O3) plate with a metallized bottom surface was used as the ground electrode. Three different situations have been studied, namely (i) the bare Al2O3, and with an ultra-thin coatings of (ii) graphite (a semiconductor) or (iii) metal, the latter two at floating potential. The purpose of these experiments was to investigate possible effects of surface charging on the discharge behavior [1]. The axial [y(t)] and radial [x(t)] time evolutions of the discharge have been measured by UHSI, plotted, and found to differ very significantly among cases (i) to (iii). In the needle-plane configuration (like in the plane-plane case), the DBD is characterized by a single pulse per half-period of the applied voltage. A two-dimensional model of the needle-plane discharge, based upon the continuity equations for electrons, ions, excited particles, and the Poisson equation, is developed; it assumes a low degree of ionization, so that the transport coefficients of the gas are uniquely determined by the local electric field [2]. In order to determine the electric field and the electrical potential in the (hyperboloidal) needle-plane geometry, the finite element method is used. We have found excellent agreement between measured and calculated [y(t)] and [x

  20. Properties of materials in high pressure hydrogen at room and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Harris, J. A., Jr.

    1972-01-01

    Experimental efforts in this program for this period. Mechanical property tests of wrought and cast nickel-base alloys and one wrought cobalt-base alloy were conducted in 34.5 MN/sq m (5000-psig) helium and hydrogen or hydrogen mixtures. Comparison of test results was made to determine degradation of properties due to the hydrogen environments. All testing was conducted on solid specimens exposed to external gaseous pressure. Specific mechanical properties determined and the testing methods used are summarized.

  1. Properties of materials in high pressure hydrogen at cryogenic, room, and elevated temperatures

    NASA Technical Reports Server (NTRS)

    Harris, J. A., Jr.; Vanwanderham, M. C.

    1973-01-01

    Various tests were conducted to determine the mechanical properties of 12 alloys that are commonly used or proposed for use in pressurized gaseous hydrogen or hydrogen containing environments. Properties determined in the hydrogen environments were compared to properties determined in a pure helium environment at the same conditions to establish environmental degradation. The specific mechanical properties tested include: high-cycle fatigue, low-cycle fatigue, fracture mechanics, creep-rupture, and tensile.

  2. Liquid Helium 3 and Solid Helium at Yale and Beyond

    NASA Astrophysics Data System (ADS)

    Lee, D. M.

    2006-03-01

    Many of the foundations of low temperature physics in the latter half of the twentieth century were built at Yale University under the leadership of Professor Cecil T. Lane who came to Yale in 1932 and Henry A. Fairbank who obtained his Ph.D. at Yale in 1944 under Lane's guidance. This discussion will mainly treat the contributions of Henry Fairbank and his students during the period between 1954 and 1963, when Henry Fairbank left Yale to become chairman of the Physics Dept. at Duke University. Following World War II small amounts of helium three became available to low temperature experimenters. Henry Fairbank’s graduate students were provided with the opportunity to investigate second sound in dilute and later concentrated mixtures of helium three in superfluid helium four. These measurements showed strong effects of the phase separation in helium 3 - helium 4 mixtures previously discovered in the laboratory of William Fairbank (a student of Lane and a brother of Henry Fairbank). As more helium three became available, studies of pure helium three were performed, including measurements of the thermal conductivity, the density and the specific heat. Early evidence for the melting curve minimum was found. The main emphasis in this work was to search for Fermi liquid behavior. Much of the later work in this area was performed by the group of John Wheatley at the University of Illinois. In studies of solid helium four at Yale, a surprising observation was made. Hitherto it had been thought that hcp was the stable phase throughout the low temperature part of the phase diagram. It was found via ultrasound experiments that a small silver of bcc solid existed at the lowest pressures. While this author was a graduate student at Yale, Henry Fairbank pointed out to him the possibility of cooling helium three via adiabatic compression from the liquid into the solid phase. (Pomeranchuk Cooling). A brief discussion is given of the use of this technique in the discovery of

  3. Assessment of Remote Sensing Technologies for Location of Hydrogen and Helium Leaks

    NASA Technical Reports Server (NTRS)

    Sellar, R. Glenn; Wang, Danli

    2000-01-01

    The objective of this initial phase of this research effort is to: 1) Evaluate remote sensing technologies for location of leaks of gaseous molecular hydrogen (H2) and gaseous helium (He) in air, for space transportation applications; and 2) Develop a diffusion model that predicts concentration of H2 or He gas as a function of leak rate and distance from the leak.

  4. Brush seal leakage performance with gaseous working fluids at static and low rotor speed conditions

    NASA Technical Reports Server (NTRS)

    Carlile, Julie A.; Hendricks, Robert C.; Yoder, Dennis A.

    1992-01-01

    The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was studied. The leakage results are included for air, helium, and carbon dioxide at several bristle/rotor interferences. Also, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were studied. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in), a fence height of 0.0635 cm (0.025 in), and 1800 bristles/cm circumference (4500 bristles/in circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison to the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approx. the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times. The air and carbon dioxide data were successfully correlated using corresponding state theory. However, the helium data followed a different curve than the air and carbon dioxide data.

  5. Brush seal leakage performance with gaseous working fluids at static and low rotor speed conditions

    NASA Technical Reports Server (NTRS)

    Carlile, Julie A.; Hendricks, Robert C.; Yoder, Dennis A.

    1992-01-01

    The leakage performance of a brush seal with gaseous working fluids at static and low rotor speed conditions was studied. The leakage results included for air, helium, and carbon dioxide at several bristle/rotor interferences. Also, the effects of packing a lubricant into the bristles and also of reversing the pressure drop across the seal were studied. Results were compared to that of an annular seal at similar operating conditions. In order to generalize the results, they were correlated using corresponding state theory. The brush seal tested had a bore diameter of 3.792 cm (1.4930 in.), a fence height of 0.0635 cm (0.025 in.), and 1800 bristles/cm circumference (4500 bristles/in. circumference). Various bristle/rotor radial interferences were achieved by using a tapered rotor. The brush seal reduced the leakage in comparison to the annular seal, up to 9.5 times. Reversing the pressure drop across the brush seal produced leakage rates approximately the same as that of the annular seal. Addition of a lubricant reduced the leakage by 2.5 times. The air and carbon dioxide data were successfully correlated using corresponding state theory. However, the helium data followed a different curve than the air and carbon dioxide data.

  6. Cryogenic helium 2 systems for space applications

    NASA Technical Reports Server (NTRS)

    Urban, E.; Katz, L.; Hendricks, J.; Karr, G.

    1978-01-01

    Two cryogenic systems are described which will provide cooling for experiments to be flown on Spacelab 2 in the early 1980's. The first system cools a scanning infrared telescope by the transfer of cold helium gas from a separate superfluid helium storage dewar. The flexible design permits the helium storage dewar and transfer assembly to be designed independent of the infrared experiment. Where possible, modified commerical apparatus is used. The second cryogenic system utilizes a specially designed superfluid dewar in which a superfluid helium experiment chamber is immersed. Each dewar system employs a porous plug as a phase separator to hold the liquid helium within the dewar and provide cold gas to a vent line. To maintain the low vapor pressure of the superfluid, each system requires nearly continuous prelaunch vacuum pump service, and each will vent to space during the Spacelab 2 flight.

  7. Special treatment reduces helium permeation of glass in vacuum systems

    NASA Technical Reports Server (NTRS)

    Bryant, P. J.; Gosselin, C. M.

    1966-01-01

    Internal surfaces of the glass component of a vacuum system are exposed to cesium in gaseous form to reduce helium permeation. The cesium gas is derived from decomposition of cesium nitrate through heating. Several minutes of exposure of the internal surfaces of the glass vessel are sufficient to complete the treatment.

  8. Helium/Carbon dioxide ratios as premonitors of volcanic activity.

    PubMed

    Thomas, D M; Naughton, J J

    1979-06-15

    The composition of the gaseous emissions of two fumaroles at the summit of Kilauea Volcano was monitored for môre than 2 years. Magma was released from the summit reservoir on three occasions during this period; prior to or during each event the ratios of helium to carbon dioxide in the fumarole gases decreased substantially from that observed during periods of quiescence.

  9. Measurements of helium 23S metastable atom density in low-pressure glow discharge plasmas by self-absorption spectroscopy of HeI 23S-23P transition

    NASA Astrophysics Data System (ADS)

    Shikama, Taiichi; Ogane, Shuhei; Ishii, Hidekazu; Iida, Yohei; Hasuo, Masahiro

    2014-08-01

    The helium 23S metastable atom densities are experimentally evaluated by self-absorption spectroscopy of the HeI 23S-23P transition spectra in two kinds of cylindrical glow discharge plasmas, which have different radii and are operated under different pressures of 300 and 20 Pa. The spectra are measured by using an interference spectroscopy system with a wavelength resolution of about 60 pm, and the relative intensities of the fine structure transitions are analyzed. It is found that the method is in principle applicable to plasmas with the pressure up to about the atmospheric pressure and electron density on the order of up to 1022 m-3. For a plasma with an absorption length of 10 mm and a spatially uniform temperature of 300 K, the method is sensitive to the metastable atom density roughly from 1016 to 1019 m-3.

  10. Gaseous leak detector

    DOEpatents

    Juravic, Jr., Frank E.

    1988-01-01

    In a short path length mass-spectrometer type of helium leak detector wherein the helium trace gas is ionized, accelerated and deflected onto a particle counter, an arrangement is provided for converting the detector to neon leak detection. The magnetic field of the deflection system is lowered so as to bring the non linear fringe area of the magnetic field across the ion path, thereby increasing the amount of deflection of the heavier neon ions.

  11. Improved gaseous leak detector

    DOEpatents

    Juravic, F.E. Jr.

    1983-10-06

    In a short path length mass-spectrometer type of helium leak detector wherein the helium trace gas is ionized, accelerated and deflected onto a particle counter, an arrangement is provided for converting the detector to neon leak detection. The magnetic field of the deflection system is lowered so as to bring the nonlinear fringe area of the magnetic field across the ion path, thereby increasing the amount of deflection of the heavier neon ions.

  12. Solid and Gaseous Fuels.

    ERIC Educational Resources Information Center

    Schultz, Hyman; And Others

    1989-01-01

    This review covers methods of sampling, analyzing, and testing coal, coke, and coal-derived solids and methods for the chemical, physical, and instrumental analyses of gaseous fuels. The review covers from October 1986, to September 1988. (MVL)

  13. Comparison between a propane-air combustion front and a helium-air simulated combustion front

    SciTech Connect

    Barraclough, S.

    1983-12-01

    Turbulent combustion experiments were performed in a right cylindrical combustion bomb using a premixed propane-air gaseous fuel. The initial conditions inside the combustion chamber were three psig and room temperature. Prior to spark firing, the turbulence intensity inside the combustion chamber was measured and could be varied over a ten fold range. The effect of initial turbulence intensity on turbulent flame propagation was investigated. Two regimes of turbulent combustion were identified, which is in agreement with a previous investigator's results. One of them, a ''transition regime'' occurs when the turbulence intensity is approximately twice the laminar flame speed. Within the transition regime, the turbulent burning speed is linearly proportional to initial turbulence intensity and independent of laminar flame speed and turbulence length scale. A high pressure helium front was injected into the combustion chamber to simulate the combustion front. Since the helium front is isothermal, hot-wire anemometry can be used to quantify the change in turbulence intensity ahead of the propagating front. The helium front was found to have different characteristics than the combustion front.

  14. Theoretical determination of the polarizability dispersion and the refractive index of helium

    NASA Astrophysics Data System (ADS)

    Puchalski, Mariusz; Piszczatowski, Konrad; Komasa, Jacek; Jeziorski, Bogumił; Szalewicz, Krzysztof

    2016-03-01

    The refractive index n of gaseous helium can be measured by optical interferometry so accurately that it can be used to establish a pressure standard which is expected to be superior to the current standard based on the height of a mercury column. The new standard requires knowledge of the dynamic polarizability of helium atom with accuracy significantly higher than obtainable in the best experiments, but possible to achieve computationally. Calculations of this quantity are presented at relativistic and quantum electrodynamics levels of theory including relativistic nuclear recoil effects. The uncertainties of the results are carefully estimated. Our recommended value of the dynamic polarizability at the He-Ne laser wavelength of 6329.908 Å, equal 1.39181197(14) a.u., has uncertainty at least two orders of magnitude smaller than that of recent measurements and is sufficiently accurate to establish a new pressure standard. Purely ab initio values of the refraction coefficient n are computed using our polarizability, literature values of magnetic susceptibility, and dielectric virial coefficients. It is shown that n -1 can be predicted by theory as a function of density and temperature with uncertainty of 1 ppm for pressures up to 3 MPa.

  15. Helium refrigeration considerations for cryomodule design

    SciTech Connect

    Ganni, V.; Knudsen, P.

    2014-01-29

    Many of the present day accelerators are based on superconducting radio frequency (SRF) cavities, packaged in cryo-modules (CM), which depend on helium refrigeration at sub-atmospheric pressures, nominally 2 K. These specialized helium refrigeration systems are quite cost intensive to produce and operate. Particularly as there is typically no work extraction below the 4.5-K supply, it is important that the exergy loss between this temperature level and the CM load temperature(s) be minimized by the process configuration choices. This paper will present, compare and discuss several possible helium distribution process arrangements to support the CM loads.

  16. Characterization and antimicrobial efficacy against E. coli of a helium/air plasma at atmospheric pressure created in a plastic package

    NASA Astrophysics Data System (ADS)

    Connolly, J.; Valdramidis, V. P.; Byrne, E.; Karatzas, K. A.; Cullen, P. J.; Keener, K. M.; Mosnier, J. P.

    2013-01-01

    A plasma source, sustained by the application of a floating high voltage (±15 kV) to parallel-plate electrodes at 50 Hz, has been achieved in a helium/air mixture at atmospheric pressure (P = 105 Pa) contained in a zip-locked plastic package placed in the electrode gap. Some of the physical and antimicrobial properties of this apparatus were established with a view to ascertain its performance as a prototype for the disinfection of fresh produce. The current-voltage (I-V) and charge-voltage (Q-V) characteristics of the system were measured as a function of gap distance d, in the range (3 × 103 ⩽ Pd ⩽ 1.0 × 104 Pa m). The electrical measurements showed this plasma source to exhibit the characteristic behaviour of a dielectric barrier discharge in the filamentary mode and its properties could be accurately interpreted by the two-capacitance in series model. The power consumed by the discharge and the reduced field strength were found to decrease quadratically from 12.0 W to 4.5 W and linearly from 140 Td to 50 Td, respectively, in the range studied. Emission spectra of the discharge were recorded on a relative intensity scale and the dominant spectral features could be assigned to strong vibrational bands in the 2+ and 1- systems of N2 and N_2^+ , respectively, with other weak signatures from the NO and OH radicals and the N+, He and O atomic species. Absolute spectral intensities were also recorded and interpreted by comparison with the non-equilibrium synthetic spectra generated by the computer code SPECAIR. At an inter-electrode gap of 0.04 m, this comparison yielded typical values for the electron, vibrational and translational (gas) temperatures of (4980 ± 100) K, (2700 ± 200) K and (300 ± 100) K, respectively and an electron density of 1.0 × 1017 m-3. A Boltzmann plot also provided a value of (3200 ± 200 K) for the vibrational temperature. The antimicrobial efficacy was assessed by studying the resistance of both Escherichia coli K12 its isogenic

  17. Analysis and Design of the NASA Langley Cryogenic Pressure Box

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Stevens, Jonathan C.; Vause, R. Frank; Winn, Peter M.; Maguire, James F.; Driscoll, Glenn C.; Blackburn, Charles L.; Mason, Brian H.

    1999-01-01

    A cryogenic pressure box was designed and fabricated for use at NASA Langley Research Center (LaRC) to subject 72 in. x 60 in. curved panels to cryogenic temperatures and biaxial tensile loads. The cryogenic pressure box is capable of testing curved panels down to -423 F (20K) with 54 psig maximum pressure on the concave side, and elevated temperatures and atmospheric pressure on the convex surface. The internal surface of the panel is cooled by high pressure helium as that is cooled to -423 F by liquid helium heat exchangers. An array of twelve independently controlled fans circulate the high pressure gaseous helium to provide uniform cooling on the panel surface. The load introduction structure, consisting of four stainless steel load plates and numerous fingers attaching the load plates to the test panel, is designed to introduce loads into the test panel that represent stresses that will he observed in the actual tank structure. The load plates are trace cooled with liquid nitrogen to reduce thermal gradients that may result in bending the load plates, and thus additional stresses in the test panel. The design of the cryogenic systems, load introduction structure, and control system are discussed in this report.

  18. Experimental Evaluation of a Subscale Gaseous Hydrogen/gaseous Oxygen Coaxial Rocket Injector

    NASA Technical Reports Server (NTRS)

    Smith, Timothy D.; Klem, Mark D.; Breisacher, Kevin J.; Farhangi, Shahram; Sutton, Robert

    2002-01-01

    The next generation reusable launch vehicle may utilize a Full-Flow Stage Combustion (FFSC) rocket engine cycle. One of the key technologies required is the development of an injector that uses gaseous oxygen and gaseous hydrogen as propellants. Gas-gas propellant injection provides an engine with increased stability margin over a range of throttle set points. This paper summarizes an injector design and testing effort that evaluated a coaxial rocket injector for use with gaseous oxygen and gaseous hydrogen propellants. A total of 19 hot-fire tests were conducted up to a chamber pressure of 1030 psia, over a range of 3.3 to 6.7 for injector element mixture ratio. Post-test condition of the hardware was also used to assess injector face cooling. Results show that high combustion performance levels could be achieved with gas-gas propellants and there were no problems with excessive face heating for the conditions tested.

  19. Experimental Evaluation of a Subscale Gaseous Hydrogen/Gaseous Oxygen Coaxial Rocket Injector

    NASA Astrophysics Data System (ADS)

    Smith, Timothy D.; Klem, Mark D.; Breisacher, Kevin J.; Farhangi, Shahram; Sutton, Robert

    2002-11-01

    The next generation reusable launch vehicle may utilize a Full-Flow Stage Combustion (FFSC) rocket engine cycle. One of the key technologies required is the development of an injector that uses gaseous oxygen and gaseous hydrogen as propellants. Gas-gas propellant injection provides an engine with increased stability margin over a range of throttle set points. This paper summarizes an injector design and testing effort that evaluated a coaxial rocket injector for use with gaseous oxygen and gaseous hydrogen propellants. A total of 19 hot-fire tests were conducted up to a chamber pressure of 1030 psia, over a range of 3.3 to 6.7 for injector element mixture ratio. Post-test condition of the hardware was also used to assess injector face cooling. Results show that high combustion performance levels could be achieved with gas-gas propellants and there were no problems with excessive face heating for the conditions tested.

  20. Gaseous hydrogen embrittlement of high strength steels

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Wei, R. P.

    1977-01-01

    The effects of temperature, hydrogen pressure, stress intensity, and yield strength on the kinetics of gaseous hydrogen assisted crack propagation in 18Ni maraging steels were investigated experimentally. It was found that crack growth rate as a function of stress intensity was characterized by an apparent threshold for crack growth, a stage where the growth rate increased sharply, and a stage where the growth rate was unchanged over a significant range of stress intensity. Cracking proceeded on load application with little or no detectable incubation period. Gaseous hydrogen embrittlement susceptibility increased with increasing yield strength.

  1. An Assessment of Helium Evolution from Helium-Saturated Propellant Depressurization in Space

    NASA Technical Reports Server (NTRS)

    Nguyen, Bich N.; Best, Frederick; Wong, Tony; Kurwitz, Cable; McConnaughey, H. (Technical Monitor)

    2001-01-01

    Helium evolution from the transfer of helium-saturated propellant in space is quantified to assess its impacts from creating two-phase gas/liquid flow from the supply tank, gas injection into the receiving tank, and liquid discharge from the receiving tank. Propellant transfer takes place between two similar tanks whose maximum storage capacity is approximately 2.55 cubic meters each. The maximum on-orbit propellants transfer capability is 9000 lbm (fuel and oxidizer). The transfer line is approximately 1.27 cm in diameter and 6096 cm in length and comprised of the fluid interconnect system (FICS), the orbiter propellant transfer system (OPTS), and the International Space Station (ISS) propulsion module (ISSPM). The propellant transfer rate begins at approximately 11 liter per minute (lpm) and subsequently drops to approximately 0.5 lpm. The tank nominal operating pressure is approximately 1827 kPa (absolute). The line pressure drops for Monomethy1hydrazine (MMH) and Nitrogen tetroxide (NTO) at 11.3 lpm are approximately 202 kPa and 302 kPa, respectively. The pressure-drop results are based on a single-phase flow. The receiving tank is required to vent from approximately 1827 kPa to a lower pressure to affect propellant transfer. These pressure-drop scenarios cause the helium-saturated propellants to release excess helium. For tank ullage venting, the maximum volumes of helium evolved at tank pressure are approximately 0.5 ft3 for MMH and 2 ft3 for NTO. In microgravity environment, due to lack of body force, the helium evolution from a liquid body acts to propel it, which influences its fluid dynamics. For propellant transfer, the volume fractions of helium evolved at line pressure are 0.1% by volume for MMH and 0.6 % by volume for NTO at 11.3 lpm. The void fraction of helium evolved varies as an approximate second order power function of flow rate.

  2. Cryogenic adsorber design in a helium refrigeration system

    NASA Astrophysics Data System (ADS)

    Hu, Zhongjun; Zhang, Ning; Li, Zhengyu; Li, Q.

    2012-06-01

    The cryogenic adsorber is specially designed to eliminate impurities in gaseous helium such as O2, and N2 which is normally difficult to remove, based on the reversible cryotrapping of impurities on an activated carbon bed. The coconut shell activated carbon is adopted because of its developed micropore structure and specific surface area. This activated carbon adsorption is mostly determined by the micropore structure, and the adsorption rate of impurities is inversely proportional to the square of the particle sizes. The active carbon absorber's maximum permissible flow velocity is 0.25 m/s. When the gas flow velocity increases, the adsorption diffusion rate of the adsorbent is reduced, because an increase in the magnitude of the velocity resulted in a reduced amount of heat transfer to a unit volume of impure gas. According to the numerical simulation of N2 adsorption dynamics, the appropriate void tower link speed and the saturated adsorption capacity are determined. Then the diameter and height of the adsorber are designed. The mass transfer length should be taken into account in the adsorber height design. The pressure decrease is also calculated. The important factors that influence the adsorber pressure decrease are the void tower speed, the adsorbed layer height, and the active carbon particle shape and size.

  3. A plan for directional dark matter sensitivity in high-pressure xenon detectors through the addition of wavelength shifting gaseous molecules

    NASA Astrophysics Data System (ADS)

    Gehman, V. M.; Goldschmidt, A.; Nygren, D.; Oliveira, C. A. B.; Renner, J.

    2013-10-01

    Xenon is an especially attractive candidate for both direct WIMP and 0νββ decay searches. Although the current trend has exploited the liquid phase, the gas phase xenon offers remarkable performance advantages for: energy resolution, topology visualization, and discrimination between electron and nuclear recoils. The NEXT-100 experiment, now under construction in the Canfranc Underground Laboratory, Spain, will operate at ~ 15 bars with 100 kg of 136Xe for the 0νββ decay search. We will describe recent results with small prototypes, indicating that NEXT-100 can provide about 0.5% FWHM energy resolution at the decay's Q value (2457.83 keV), as well as rejection of γ-rays with topological cuts. However, sensitivity goals for WIMP dark matter and 0νββ decay searches indicate the probable need for ton-scale active masses. NEXT-100 provides the springboard to reach this scale with xenon gas. We describe a scenario for performing both searches in a single, high-pressure, ton-scale xenon gas detector, without significant compromise to either. In addition, even in a single ton-scale, high-pressure xenon gas TPC, an intrinsic sensitivity to the nuclear recoil direction may exist. This plausibly offers an advance of more than two orders of magnitude relative to current low-pressure TPC concepts. We argue that, in an era of deepening fiscal austerity, such a dual-purpose detector may be possible at acceptable cost, within the time frame of interest, and deserves our collective attention.

  4. Warm Pressurant Gas Effects on the Static Bubble Point Pressure for Cryogenic LADs

    NASA Technical Reports Server (NTRS)

    Hartwig, Jason W.; McQuillen, John; Chato, Daniel J.

    2014-01-01

    This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K - 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  5. Warm Pressurant Gas Effects on the Bubble Point Pressure for Cryogenic LADs

    NASA Technical Reports Server (NTRS)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2014-01-01

    This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  6. Gaseous wire detectors

    SciTech Connect

    Va'vra, J.

    1997-08-01

    This article represents a series of three lectures describing topics needed to understand the design of typical gaseous wire detectors used in large high energy physics experiments; including the electrostatic design, drift of electrons in the electric and magnetic field, the avalanche, signal creation, limits on the position accuracy as well as some problems one encounters in practical operations.

  7. Helium damage and helium effusion in fully stabilised zirconia

    NASA Astrophysics Data System (ADS)

    Damen, P. M. G.; Matzke, Hj.; Ronchi, C.; Hiernaut, J.-P.; Wiss, T.; Fromknecht, R.; van Veen, A.; Labohm, F.

    2002-05-01

    Fully stabilised zirconia (FSZ) samples have been implanted with helium-ions of different energies (200 keV and 1 MeV) and with different fluences (1.4×10 13-1.4×10 16 He +/cm 2). Neutron depth profiling (NDP) for different annealing temperatures and effusion experiments in two different experimental systems with different thermal annealings have been performed on these samples. The samples were analysed by electron microscopy during the various annealing stages. For the low-fluence samples, the diffusion of helium is probably caused by vacancy assisted interstitial diffusion with an activation energy of 1.6 eV. In the highest fluence samples probably high pressure bubbles are formed during thermal annealing.

  8. Review of Membranes for Helium Separation and Purification.

    PubMed

    Scholes, Colin A; Ghosh, Ujjal K

    2017-02-17

    Membrane gas separation has potential for the recovery and purification of helium, because the majority of membranes have selectivity for helium. This review reports on the current state of the research and patent literature for membranes undertaking helium separation. This includes direct recovery from natural gas, as an ancillary stage in natural gas processing, as well as niche applications where helium recycling has potential. A review of the available polymeric and inorganic membranes for helium separation is provided. Commercial gas separation membranes in comparable gas industries are discussed in terms of their potential in helium separation. Also presented are the various membrane process designs patented for the recovery and purification of helium from various sources, as these demonstrate that it is viable to separate helium through currently available polymeric membranes. This review places a particular focus on those processes where membranes are combined in series with another separation technology, commonly pressure swing adsorption. These combined processes have the most potential for membranes to produce a high purity helium product. The review demonstrates that membrane gas separation is technically feasible for helium recovery and purification, though membranes are currently only applied in niche applications focused on reusing helium rather than separation from natural sources.

  9. Review of Membranes for Helium Separation and Purification

    PubMed Central

    Scholes, Colin A.; Ghosh, Ujjal K.

    2017-01-01

    Membrane gas separation has potential for the recovery and purification of helium, because the majority of membranes have selectivity for helium. This review reports on the current state of the research and patent literature for membranes undertaking helium separation. This includes direct recovery from natural gas, as an ancillary stage in natural gas processing, as well as niche applications where helium recycling has potential. A review of the available polymeric and inorganic membranes for helium separation is provided. Commercial gas separation membranes in comparable gas industries are discussed in terms of their potential in helium separation. Also presented are the various membrane process designs patented for the recovery and purification of helium from various sources, as these demonstrate that it is viable to separate helium through currently available polymeric membranes. This review places a particular focus on those processes where membranes are combined in series with another separation technology, commonly pressure swing adsorption. These combined processes have the most potential for membranes to produce a high purity helium product. The review demonstrates that membrane gas separation is technically feasible for helium recovery and purification, though membranes are currently only applied in niche applications focused on reusing helium rather than separation from natural sources. PMID:28218644

  10. Pressure cryocooling protein crystals

    DOEpatents

    Kim, Chae Un; Gruner, Sol M.

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  11. Effect of high power CO2 and Yb:YAG laser radiation on the characteristics of TIG arc in atmospherical pressure argon and helium

    NASA Astrophysics Data System (ADS)

    Wu, Shikai; Xiao, Rongshi

    2015-04-01

    The effects of laser radiation on the characteristics of the DC tungsten inert gas (TIG) arc were investigated by applying a high power slab CO2 laser and a Yb:YAG disc laser. Experiment results reveal that the arc voltage-current curve shifts downwards, the arc column expands, and the arc temperature rises while the high power CO2 laser beam vertically interacts with the TIG arc in argon. With the increase of the laser power, the voltage-current curve of the arc shifts downwards more significantly, and the closer the laser beam impingement on the arc to the cathode, the more the decrease in arc voltage. Moreover, the arc column expansion and the arc temperature rise occur mainly in the region between the laser beam incident position and the anode. However, the arc characteristics hardly change in the cases of the CO2 laser-helium arc and YAG laser-arc interactions. The reason is that the inverse Bremsstrahlung absorption coefficients are greatly different due to the different electron densities of the argon and helium arcs and the different wave lengths of CO2 and YAG lasers.

  12. Vorticity matching in superfluid helium

    NASA Astrophysics Data System (ADS)

    Samuels, David C.

    1991-12-01

    Recent experiments have rekindled interest in high Reynolds number flows using superfluid helium. In a continuing series of experiments, the flow of helium II through various devices (smooth pipes, corrugated pipes, valves, venturies, turbine flowmeters, and coanda flowmeters for example) was investigated. In all cases, the measured values (typically, mass flow rates and pressure drops) were found to be well described by classical relations for high Reynolds flows. This is unexpected since helium II consists of two interpenetrating fluids; one fluid with nonzero viscosity (the normal fluid) and one with zero viscosity (the superfluid). Only the normal fluid component should directly obey classical relations. Since the experiments listed above only measure the external behavior of the flow (i.e., pressure drops over devices), there is a great deal of room for interpretation of their results. One possible interpretation is that in turbulent flows the normal fluid and the superfluid velocity fields are somehow 'locked' together, presumably by the mutual friction force between the superfluid vortex filaments and the normal fluid. We refer to this locking together of the two fluids as 'vorticity matching.'

  13. Confined helium on Lagrange meshes.

    PubMed

    Baye, D; Dohet-Eraly, J

    2015-12-21

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than 10(-10). For larger radii up to 10, they progressively decrease to 10(-3), still improving the best literature results.

  14. GASEOUS DISPOSAL PROCESS

    DOEpatents

    Ryan, R.F.; Thomasson, F.R.; Hicks, J.H.

    1963-01-22

    A method is described of removing gaseous radioactive Xe and Kr from water containing O. The method consists in stripping the gases from the water stream by means of H flowing countercurrently to the stream. The gases are then heated in a deoxo bed to remove O. The carrier gas is next cooled and passed over a charcoal adsorbent bed maintained at a temperature of about --280 deg F to remove the Xe and Kr. (AEC)

  15. Simplified Helium Refrigerator Cycle Analysis Using the `Carnot Step'

    NASA Astrophysics Data System (ADS)

    Knudsen, P.; Ganni, V.

    2006-04-01

    An analysis of the Claude form of an idealized helium liquefier for the minimum input work reveals the `Carnot Step' for helium refrigerator cycles. As the `Carnot Step' for a multi-stage polytropic compression process consists of equal pressure ratio stages; similarly for an idealized helium liquefier the `Carnot Step' consists of equal temperature ratio stages for a given number of expansion stages. This paper presents the analytical basis and some useful equations for the preliminary examination of existing and new Claude helium refrigeration cycles.

  16. Correlation and prediction of gaseous diffusion coefficients.

    NASA Technical Reports Server (NTRS)

    Marrero, T. R.; Mason, E. A.

    1973-01-01

    A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.

  17. Investigations on thermodynamic phenomena of the active-pressurization process of a cryogenic propellant tank

    NASA Astrophysics Data System (ADS)

    Ludwig, C.; Dreyer, M. E.

    2014-09-01

    In optimizing the design and operation of a launcher’s cryogenic upper stage, the required pressurant gas mass must be accurately predicted. In order to do so, the appearing thermodynamic phenomena of the initial active-pressurization process of a cryogenic propellant tank need to be understood and assessed. On that account, ground experiments with liquid nitrogen as model propellant, pressurized with either gaseous nitrogen or gaseous helium, as well as numerical simulations were performed, and analytical approaches were applied. It was found that the thermal stratification in the liquid propellant is mostly driven by the increase in saturation temperature at the free surface during pressurization. The mode of phase change during pressurization was found to be mainly dependent on the pressurant gas type. The main mode of heat transfer appears from pressurant gas to the tank wall, through which the heat is then partly conducted into the uppermost liquid layers. After tank pressurization end, a pressure drop is observed and the decrease in vapor temperature is identified as its main driver. Moreover, a correlation is derived for the prediction of the required pressurant gas mass, based on the Jakob number and the thermal expansion Froude number, identifying pressurant gas temperature, phase change, and tank aspect ratio as the most important parameters, determining the required pressurant gas mass for cryogenic propellant tanks.

  18. Barometric pressure

    NASA Technical Reports Server (NTRS)

    Billings, C. E.

    1973-01-01

    The effects of alterations in barometric pressure on human beings are described. Human tolerances for gaseous environments and low and high barometric pressure are discussed, including effects on specific areas, such as the ear, lungs, teeth, and sinuses. Problems due to trapped gas within the body, high dynamic pressures on the body, and blasts are also considered.

  19. Sonic helium detectors in the Fermilab Tevatron

    SciTech Connect

    Bossert, R.J.; /Fermilab

    2006-01-01

    In the Fermilab Tevatron cryogenic system there are many remotely located low-pressure plate relief valves that must vent large volumes of cold helium gas when magnet quenches occur. These valves can occasionally stick open or not reseat completely, resulting in a large helium loss. As such, the need exists for a detector to monitor the relief valve's discharge area for the presence of helium. Due to the quantity needed, cost is an important factor. A unit has been developed and built for this purpose that is quite inexpensive. Its operating principle is based on the speed of sound, where two closely matched tubes operate at their acoustic resonant frequency. When helium is introduced into one of these tubes, the resulting difference in acoustic time of flight is used to trigger an alarm. At present, there are 39 of these units installed and operating in the Tevatron. They have detected many minor and major helium leaks, and have also been found useful in detecting a rise in the helium background in the enclosed refrigerator buildings. This paper covers the construction, usage and operational experience gained with these units over the last several years.

  20. Superfluid Helium Tanker (SFHT) study

    NASA Technical Reports Server (NTRS)

    Eberhardt, Ralph N.; Dominick, Sam M.; Anderson, John E.; Gille, John P.; Martin, Tim A.; Marino, John S.; Paynter, Howard L.; Traill, R. Eric; Herzl, Alfred; Gotlib, Sam

    1988-01-01

    Replenishment of superfluid helium (SFHe) offers the potential of extending the on-orbit life of observatories, satellite instruments, sensors and laboratories which operate in the 2 K temperature regime. A reference set of resupply customers was identified as representing realistic helium servicing requirements and interfaces for the first 10 years of superfluid helium tanker (SFHT) operations. These included the Space Infrared Telescope Facility (SIRTF), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (Astromag), and the Microgravity and Materials Processing Sciences Facility (MMPS)/Critical Point Phenomena Facility (CPPF). A mixed-fleet approach to SFHT utilization was considered. The tanker permits servicing from the Shuttle cargo bay, in situ when attached to the OMV and carried to the user spacecraft, and as a depot at the Space Station. A SFHT Dewar ground servicing concept was developed which uses a dedicated ground cooling heat exchanger to convert all the liquid, after initial fill as normal fluid, to superfluid for launch. This concept permits the tanker to be filled to a near full condition, and then cooled without any loss of fluid. The final load condition can be saturated superfluid with any desired ullage volume, or the tank can be totally filed and pressurized. The SFHT Dewar and helium plumbing system design has sufficient component redundancy to meet fail-operational, fail-safe requirements, and is designed structurally to meet a 50 mission life usage requirement. Technology development recommendations were made for the selected SFHT concept, and a Program Plan and cost estimate prepared for a phase C/D program spanning 72 months from initiation through first launch in 1997.

  1. Investigations of levitated helium drops

    NASA Astrophysics Data System (ADS)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  2. Low energy consumption method for separating gaseous mixtures and in particular for medium purity oxygen production

    DOEpatents

    Jujasz, Albert J.; Burkhart, James A.; Greenberg, Ralph

    1988-01-01

    A method for the separation of gaseous mixtures such as air and for producing medium purity oxygen, comprising compressing the gaseous mixture in a first compressor to about 3.9-4.1 atmospheres pressure, passing said compressed gaseous mixture in heat exchange relationship with sub-ambient temperature gaseous nitrogen, dividing the cooled, pressurized gaseous mixture into first and second streams, introducing the first stream into the high pressure chamber of a double rectification column, separating the gaseous mixture in the rectification column into a liquid oxygen-enriched stream and a gaseous nitrogen stream and supplying the gaseous nitrogen stream for cooling the compressed gaseous mixture, removing the liquid oxygen-enriched stream from the low pressure chamber of the rectification column and pumping the liquid, oxygen-enriched steam to a predetermined pressure, cooling the second stream, condensing the cooled second stream and evaporating the oxygen-enriched stream in an evaporator-condenser, delivering the condensed second stream to the high pressure chamber of the rectification column, and heating the oxygen-enriched stream and blending the oxygen-enriched stream with a compressed blend-air stream to the desired oxygen concentration.

  3. Energy Distribution of Electrons in Radiation Induced-Helium Plasmas. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Lo, R. H.

    1972-01-01

    Energy distribution of high energy electrons as they slow down and thermalize in a gaseous medium is studied. The energy distribution in the entire energy range from source energies down is studied analytically. A helium medium in which primary electrons are created by the passage of heavy-charged particles from nuclear reactions is emphasized. A radiation-induced plasma is of interest in a variety of applications, such as radiation pumped lasers and gaseous core nuclear reactors.

  4. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  5. Gaseous Fuel Injection Modeling using a Gaseous Sphere Injection Methodology

    SciTech Connect

    Hessel, R P; Aceves, S M; Flowers, D L

    2006-03-06

    The growing interest in gaseous fuels (hydrogen and natural gas) for internal combustion engines calls for the development of computer models for simulation of gaseous fuel injection, air entrainment and the ensuing combustion. This paper introduces a new method for modeling the injection and air entrainment processes for gaseous fuels. The model uses a gaseous sphere injection methodology, similar to liquid droplet in injection techniques used for liquid fuel injection. In this paper, the model concept is introduced and model results are compared with correctly- and under-expanded experimental data.

  6. GASEOUS SCINTILLATION COUNTER

    DOEpatents

    Eggler, C.; Huddleston, C.M.

    1959-04-28

    A gaseous excitation counter for detecting the presence amd measuring the energy of subatomic particles and electromagnetic radiation is described. The counter includes a gas-tight chamber filled with an elemental gas capable of producing ultra-violet excitation quanta when irradiated with subatomic particles and electromagnetic radiation. The gas has less than one in a thousand parts ultra-violet absorbing contamination. When nuclear radiation ps present the ultra-violet light produced by the gas strikes a fluorescent material within the counter, responsive to produce visible excitation quanta, and photo-sensitive counting means detect the visible emission.

  7. Blow-down analysis of helium from a cryogenic dewar

    NASA Technical Reports Server (NTRS)

    Khan, H. J.; Zhang, Q. Q.; Rhee, M.; Figueroa, O.

    1992-01-01

    NASA is currently developing Space Shuttle-based refilling of helium using superfluid helium on-orbit transfer (SHOOT). All the critical components of SHOOT need to be developed through ground-based tests. The helium dewar is one of these components. The Dewar consists of a vacuum vessel enclosing a superinsulated tank. The space between the vacuum vessel and the liquid tank is considered a common vacuum space. In the event that the vacuum is lost, the heat transfers to the dewar and the pressure inside the dewar increases rapidly, resulting in rupture of the dewar due to excessive pressure. Therefore, an emergency vent line is required for release of helium to prevent the dewar from rupturing. The study describes a numerical model for blow-down analysis in an emergency. This qualifies the design of the emergency vent line to be adequate for the assumed heat loads to the helium dewar.

  8. Blow-down analysis of helium from a cryogenic dewar

    NASA Astrophysics Data System (ADS)

    Khan, H. J.; Zhang, Q. Q.; Rhee, M.; Figueroa, O.

    NASA is currently developing Space Shuttle-based refilling of helium using superfluid helium on-orbit transfer (SHOOT). All the critical components of SHOOT need to be developed through ground-based tests. The helium dewar is one of these components. The Dewar consists of a vacuum vessel enclosing a superinsulated tank. The space between the vacuum vessel and the liquid tank is considered a common vacuum space. In the event that the vacuum is lost, the heat transfers to the dewar and the pressure inside the dewar increases rapidly, resulting in rupture of the dewar due to excessive pressure. Therefore, an emergency vent line is required for release of helium to prevent the dewar from rupturing. The study describes a numerical model for blow-down analysis in an emergency. This qualifies the design of the emergency vent line to be adequate for the assumed heat loads to the helium dewar.

  9. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

    NASA Technical Reports Server (NTRS)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2013-01-01

    This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  10. Electrostatic Precipitation in Nearly Pure Gaseous Nitrogen

    NASA Technical Reports Server (NTRS)

    Buhler, Charles; Calle, Carlos; Clements, Sid; Cox, Bobby; Ritz, Mindy

    2008-01-01

    Electrostatic precipitation was performed in a nearly pure gaseous nitrogen system as a possible remedy for black dust contaminant from high pressure 6000 psi lines at the NASA Kennedy Space Center. The results of a prototype electrostatic precipitator that was built and tested using nitrogen gas at standard atmospheric pressures is presented. High voltage pulsed waveforms are generated using a rotating spark gap system at 30 Hz. A unique dust delivery system utilizing the Venturi effect was devised that supplies a given amount of dust per unit time for testing purposes.

  11. Effect of boundary conditions on the kinetics of helium release from structural materials

    NASA Astrophysics Data System (ADS)

    Zaluzhnyi, A. G.

    2015-11-01

    Gaseous products of nuclear reactions (specifically, helium) play a significant part in altering the material properties upon irradiation. It is known that atoms of inert gases promote the generation and growth of pores in irradiated materials and affect phenomena such as swelling, high-temperature irradiation embrittlement, etc. Therefore, a study of the behavior of helium (its production, accumulation, retention, and release) within structural materials is fairly topical. In order to validate the methods of express imitation of accumulation and retention of helium within structural materials under reactor irradiation, we perform a comparative analysis of the spectra of the rate of gas release from samples of austenitic steel 0Kh16N15M3B that were saturated with helium in different ways, i.e., through irradiation in a cyclotron, a magnetic massseparation setup, the IRT-2000 reactor, the BOR-60 reactor, and using the so-called tritium trick technique. The effect of the presence of dislocations and grain boundaries on the release of helium from materials is evaluated. The results of the research conducted show that the kinetics of helium release from samples saturated with helium through the bombardment with alpha particles of different energies, which ensures the simultaneous introduction of helium and radiation defects (in wide ranges of helium concentration and radiation damage) into the material lattice, is similar to the kinetics of helium release from samples irradiated in reactors.

  12. Downhole gaseous liquid flow agitator

    SciTech Connect

    Kamilos, N.; Kennedy, D.D.; Lederhos, L.J. Jr.

    1989-03-14

    An apparatus is described for agitating and mixing of a gaseous phase and a liquid phase comprising: a first tube having non-blocking internal threads within the first tube to agitate a liquid phase adhering thereto with a gaseous phase passing therethrough, whereby a uniform gaseous phase and liquid phase mixture is formed; and a second tube connected to an end of the first tube having non-blocking internal threads of opposite handedness.

  13. Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Hunt, J. L.; Boney, L. R.

    1973-01-01

    Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

  14. Performance of Oil-Injected Scroll Compressors for Helium Refrigerators

    NASA Astrophysics Data System (ADS)

    Shiibayashi, Masao; Izunaga, Yasushi; Sado, Shintaro

    In recent years there arises growing demand of helium liquefaction refrigerators for the magnetic resonance imaging systems, magnetically levitated vehicles and other systems using superconducting magnet. From this background, a small size, scroll type of hermetic helium compressor capable of compressing helium gas to the pressure ratio of 20 in a single stage is developed. Main features of this compressor are as follows. 1) Discharge capacity can be varied from 7 to 20 Nm3/h by changing driving motor frequency from 30 to 80 Hz. 2) The overall adiabatic efficiency showed 72%∼79% under the pressure ratio range of 11∼20 at 60 Hz using oil injection cooling device.

  15. Observation of a superfluid component within solid helium.

    PubMed

    Lauter, H; Apaja, V; Kalinin, I; Kats, E; Koza, M; Krotscheck, E; Lauter, V V; Puchkov, A V

    2011-12-23

    We demonstrate by neutron scattering that a localized superfluid component exists at high pressures within solid helium in aerogel. Its existence is deduced from the observation of two sharp phonon-roton spectra which are clearly distinguishable from modes in bulk superfluid helium. These roton excitations exhibit different roton gap parameters than the roton observed in the bulk fluid at freezing pressure. One of the roton modes disappears after annealing the samples. Comparison with theoretical calculations suggests that the model that reproduces the observed data best is that of superfluid double layers within the solid and at the helium-substrate interface.

  16. Combined cold compressor/ejector helium refrigerator

    DOEpatents

    Brown, Donald P.

    1985-01-01

    A refrigeration apparatus having an ejector operatively connected with a cold compressor to form a two-stage pumping system. This pumping system is used to lower the pressure, and thereby the temperature of a bath of boiling refrigerant (helium). The apparatus as thus arranged and operated has substantially improved operating efficiency when compared to other processes or arrangements for achieving a similar low pressure.

  17. Combined cold compressor/ejector helium refrigerator

    DOEpatents

    Brown, D.P.

    1984-06-05

    A refrigeration apparatus having an ejector operatively connected with a cold compressor to form a two-stage pumping system. This pumping system is used to lower the pressure, and thereby the temperature of a bath of boiling refrigerant (helium). The apparatus as thus arranged and operated has substantially improved operating efficiency when compared to other processes or arrangements for achieving a similar low pressure.

  18. Effect of gaseous ammonia on nicotine sorption

    SciTech Connect

    Webb, A.M.; Singer, B.C.; Nazaroff, W.W.

    2002-06-01

    Nicotine is a major constituent of environmental tobacco smoke. Sorptive interactions of nicotine with indoor surfaces can substantially alter indoor concentrations. The phenomenon is poorly understood, including whether sorption is fully reversible or partially irreversible. They hypothesize that acid-base chemistry on indoor surfaces might contribute to the apparent irreversibility of nicotine sorption under some circumstances. Specifically, they suggest that nicotine may become protonated on surfaces, markedly reducing its vapor pressure. If so, subsequent exposure of the surface to gaseous ammonia, a common base, could raise the surface pH, causing deprotonation and desorption of nicotine from surfaces. A series of experiments was conducted to explore the effect of ammonia on nicotine sorption to and reemission from surfaces. The results indicate that, under some conditions, exposure to gaseous ammonia can substantially increase the rate of desorption of previously sorbed nicotine from common indoor surface materials.

  19. The Descending Helium Balloon

    ERIC Educational Resources Information Center

    Helseth, Lars Egil

    2014-01-01

    I describe a simple and fascinating experiment wherein helium leaks out of a rubber balloon, thereby causing it to descend. An estimate of the volumetric leakage rate is made by measuring its rate of descent.

  20. Gaseous trace impurity analyzer and method

    DOEpatents

    Edwards, Jr., David; Schneider, William

    1980-01-01

    Simple apparatus for analyzing trace impurities in a gas, such as helium or hydrogen, comprises means for drawing a measured volume of the gas as sample into a heated zone. A segregable portion of the zone is then chilled to condense trace impurities in the gas in the chilled portion. The gas sample is evacuated from the heated zone including the chilled portion. Finally, the chilled portion is warmed to vaporize the condensed impurities in the order of their boiling points. As the temperature of the chilled portion rises, pressure will develop in the evacuated, heated zone by the vaporization of an impurity. The temperature at which the pressure increase occurs identifies that impurity and the pressure increase attained until the vaporization of the next impurity causes a further pressure increase is a measure of the quantity of the preceding impurity.

  1. GASEOUS DISCHARGE DEVICE

    DOEpatents

    Gow, J.D.

    1961-01-10

    An extremely compact two-terminal gaseous discharge device is described that is capable of producing neutrons in copious quantities, relatively high energy ions, intense x rays, and the like. Principal novelty resides in the provision of a crossed electric-magnetic field region in the discharge envelope that traps electrons and accelerates them to very high energies to provide an intense ionizing medium adjacent the anode of the device for ionizing gas therein with extremely high efficiency. In addition, the crossed-field trapping region holds the electrons close to the anode whereby the acceleration of ions to the cathode is not materially effected by the electron sheath and the ions assume substantially the full energy of the anodecathode potential drop. (auth)

  2. Japan's research on gaseous flames

    NASA Technical Reports Server (NTRS)

    Niioka, Takashi

    1995-01-01

    Although research studies on gaseous flames in microgravity in Japan have not been one-sided, they have been limited, for the most part, to comparatively fundamental studies. At present it is only possible to achieve a microgravity field by the use of drop towers, as far as gaseous flames are concerned. Compared with experiments on droplets, including droplet arrays, which have been vigorously performed in Japan, studies on gaseous flames have just begun. Experiments on ignition of gaseous fuel, flammability limits, flame stability, effect of magnetic field on flames, and carbon formation from gaseous flames are currently being carried out in microgravity. Seven subjects related to these topics are introduced and discussed herein.

  3. BASG thermomechanical pump helium 2 transfer tests

    NASA Technical Reports Server (NTRS)

    Mills, G. L.; Newell, D. A.; Urbach, A. R.

    1990-01-01

    The purpose of the effort described was to perform experiments and calculations related to using a thermomechanical pump in the space-based resupply of the Space Infrared Telescope Facility (SIRTF) with Helium 2. Thermomechanical (fountain effect) pumps have long been suggested as a means for pumping large quantities of Helium 2. The unique properties of Helium 2 have made it useful for cooling space instruments. Several space science missions, including SIRTF, are now being planned which would benefit greatly from on-orbit resupply of Helium 2. A series of experiments were performed to demonstrate that large volumes of Helium 2 can be transferred with a thermomechanical pump at high flow rates and at high efficiency from one dewar to another through valves and lines that are similar to the plumbing arrangement that would be necessary to accomplish such a transfer on-orbit. In addition, temperature, pressure, and flow rate data taken during the tests were used to verify and refine a computer model which was developed.

  4. Method for removing acid gases from a gaseous stream

    DOEpatents

    Gorin, Everett; Zielke, Clyde W.

    1981-01-01

    In a process for hydrocracking a heavy aromatic polynuclear carbonaceous feedstock containing reactive alkaline constituents to produce liquid hydrocarbon fuels boiling below about 475.degree. C. at atmospheric pressure by contacting the feedstock with hydrogen in the presence of a molten metal halide catalyst, thereafter separating a gaseous stream containing hydrogen, at least a portion of the hydrocarbon fuels and acid gases from the molten metal halide and regenerating the molten metal halide, thereby producing a purified molten metal halide stream for recycle to the hydrocracking zone, an improvement comprising; contacting the gaseous acid gas, hydrogen and hydrocarbon fuels-containing stream with the feedstock containing reactive alkaline constituents to remove acid gases from the acid gas containing stream. Optionally at least a portion of the hydrocarbon fuels are separated from gaseous stream containing hydrogen, hydrocarbon fuels and acid gases prior to contacting the gaseous stream with the feedstock.

  5. Measurements of the total energy lost per electron-ion pair lost in low-pressure inductive argon, helium, oxygen and nitrogen discharge

    NASA Astrophysics Data System (ADS)

    Lee, Young-Kwang; Ku, Ju-Hwan; Chung, Chin-Wook

    2011-02-01

    Experimental measurements of the total energy lost per electron-ion pair lost, ɛT, were performed in a low-pressure inductive atomic gases (Ar, He) and molecular gases (O2, N2) discharge. The value of ɛT was determined from a power balance based on the electropositive global (volume-averaged) model. A floating harmonic method was employed to measure ion fluxes and electron temperatures at the discharge wall. In the pressure range 5-50 mTorr, it was found that the measured ɛT ranged from about 70 to 150 V for atomic gases, but from about 180 to 1300 V for molecular gases. This difference between atomic and molecular discharge is caused by additional collisional energy losses of molecular gases. For argon discharge, the stepwise ionization effect on ɛT was observed at relatively high pressures. For different gases, the measured ɛT was evaluated with respect to the electron temperature, and then compared with the calculation results, which were derived from collisional and kinetic energy loss. The measured ɛT and their calculations showed reasonable agreement.

  6. In situ controlled modification of the helium density in single helium-filled nanobubbles

    SciTech Connect

    David, M.-L. Pailloux, F.; Alix, K.; Mauchamp, V.; Pizzagalli, L.; Couillard, M.; Botton, G. A.

    2014-03-28

    We demonstrate that the helium density and corresponding pressure can be modified in single nano-scale bubbles embedded in semiconductors by using the electron beam of a scanning transmission electron microscope as a multifunctional probe: the measurement probe for imaging and chemical analysis and the irradiation source to modify concomitantly the pressure in a controllable way by fine tuning of the electron beam parameters. The control of the detrapping rate is achieved by varying the experimental conditions. The underlying physical mechanisms are discussed; our experimental observations suggest that the helium detrapping from bubbles could be interpreted in terms of direct ballistic collisions, leading to the ejection of the helium atoms from the bubble.

  7. Evaluation of candidate Stirling engine heater tube alloys after 3500 hours exposure to high pressure doped hydrogen or helium. Final report

    SciTech Connect

    Misencik, J.A.; Titran, R.H.

    1984-10-01

    Sixteen commercial tubing alloys were endurance tested at 820/sup 0/ C, 15 MPa in a diesel-fuel fired Stirling engine simulator materials test rig: iron-base N-155, A-286, Incoloy 800, 19-9DL, CG-27, W-545, 12RN72, 253MA, Sanicro 31H and Sanicro 32; nickel-base Inconel 601, Inconel 625, Inconel 718, Inconel 750 and Pyromet 901; and cobalt-base HS-188. The iron-nickel alloys CG-27 and Pyromet 901 exhibited superior oxidation/corrosion resistance to the diesel-fuel combustion products and surpassed the design criterias' 3500 h creep-rupture endurance life. Three other alloys, Inconel 625, W-545, and 12RN72, had creep-rupture failures after 2856, 2777, and 1598 h, respectively. Hydrogen permeability coefficients determined after 250 h of rig exposure show that Pyromet 901 had the lowest Phi value, 0.064x10/sup -6/ cm/sup 2//s MPa/sup 1///sup 2/. The next five hairpin tubes, CG-27, Inconel 601, Inconel 718(wd), Inconel 750, and 12RN72(cw) all had Phi values below 0.2x10/sup -6/ more than a decade lower than the design criteria. Based upon its measured high strength and low hydrogen permeation, CG-27 was selected for 3500 h endurance testing at 21 MPa gas pressure and 820/sup 0/C. Results of the high pressure, 21 MPa, CG-27 endurance test demonstrated that the 1.0 vol % C0/sub 2/ dopant is an effective deterrent to hydrogen permeation. The 21 MPa hydrogen gas pressure apparent permeability coefficient at 820/sup 0/C approached 0.1x10/sup -6/ cm/sup 2/sec MPa/sup 1///sup 2/ after 500 hr, the same as the 15 MPa test. Even at this higher gas pressure and comparable permeation rate, CG-27 passed the 3500 hr endurance test without creep-rupture failures. It is concluded that the CG-27 alloy, in the form of thin wall tubing is suitable for Stirling engine applications at 820/sup 0/C and gas pressures up to 21 MPa.

  8. Suprathermal electron energy spectrum and nonlocally affected plasma-wall interaction in helium/air micro-plasma at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Demidov, V. I.; Adams, S. F.; Miles, J. A.; Koepke, M. E.; Kurlyandskaya, I. P.

    2016-10-01

    Details of ground-state and excited-state neutral atoms and molecules in an atmospheric-pressure micro-discharge plasma may be obtained by plasma electron spectroscopy (PLES), based on a wall probe. The presence and transport of energetic (suprathermal) electrons, having a nonlocal origin, are responsible for electrostatic charging of the plasma boundary surfaces to potentials many times that associated with the ambient electron kinetic energy. The energy-flux distribution function is shown to be controllable for applications involving analysis of composition and processes taking place in a multiphase (plasma-gas-solid), chemically reactive, interaction region.

  9. Comparison of two electro-hydrodynamic force models for the interaction between helium jet flow and an atmospheric-pressure "plasma jet"

    NASA Astrophysics Data System (ADS)

    Logothetis, D.; Papadopoulos, P. K.; Svarnas, P.; Vafeas, P.

    2016-12-01

    In this work, two simple phenomenological models of the electro-hydrodynamic force that arises in an atmospheric-pressure "plasma jet" are presented. The models are distinguished by the different boundary conditions applied for the consideration of the plasma propagation length. The comparison is based on numerical simulations, which are combined with experimental data, in order to determine the magnitude of the electro-hydrodynamic force and assess the ability of the two models to evaluate the visible plasma length. The results reveal that the gas flow characteristics depend on the spatial range of the force action and the force magnitude, and vice versa.

  10. Helium-flow measurement using ultrasonic technique

    SciTech Connect

    Sondericker, J.H.

    1983-01-01

    While designing cryogenic instrumentation for the Colliding Beam Accelerator (CBA) helium-distribution system it became clear that accurate measurement of mass flow of helium which varied in temperature from room to sub-cooled conditions would be difficult. Conventional venturi flow meters full scale differential pressure signal would decrease by more than an order of magnitude during cooldown causing unacceptable error at operating temperature. At sub-cooled temperatures, helium would be pumped around cooling loops by an efficient, low head pressure circulating compressor. Additional pressure drop meant more pump work was necessary to compress the fluid resulting in a higher outlet temperature. The ideal mass flowmeter for this application was one which did not add pressure drop to the system, functioned over the entire temperature range, has high resolution and delivers accurate mass flow measurement data. Ultrasonic flow measurement techniques used successfully by the process industry, seemed to meet all the necessary requirements. An extensive search for a supplier of such a device found that none of the commercial stock flowmeters were adaptable to cryogenic service so the development of the instrument was undertaken by the CBA Cryogenic Control and Instrumentation Engineering Group at BNL.

  11. Pressurization System Modeling for a Generic Bimese Two- Stage-to-Orbit Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Mazurkivich, Pete; Chandler, Frank; Nguyen, Han

    2005-01-01

    A pressurization system model was developed for a generic bimese Two-Stage-to-orbit Reusable Launch Vehicle using a cross-feed system and operating with densified propellants. The model was based on the pressurization system model for a crossfeed subscale water test article and was validated with test data obtained from the test article. The model consists of the liquid oxygen and liquid hydrogen pressurization models, each made up of two submodels, Booster and Orbiter tank pressurization models. The tanks are controlled within a 0.2-psi band and pressurized on the ground with ambient helium and autogenously in flight with gaseous oxygen and gaseous hydrogen. A 15-psi pressure difference is maintained between the Booster and Orbiter tanks to ensure crossfeed check valve closure before Booster separation. The analysis uses an ascent trajectory generated for a generic bimese vehicle and a tank configuration based on the Space Shuttle External Tank. It determines the flow rates required to pressurize the tanks on the ground and in flight, and demonstrates the model's capability to analyze the pressurization system performance of a full-scale bimese vehicle with densified propellants.

  12. The Creation of Long-Lived Multielectron Bubbles in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Fang, Jieping; Tempere, J.; Silvera, Isaac F.

    2017-04-01

    Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes. MEBs in liquid helium are predicted to have dynamic instabilities for zero or positive pressures, and stability for negative pressures. We report the production of long-lived MEBs in a novel cell filled with helium at static negative pressures. MEBs were extracted from the vapor sheath of a heated filament loop embedded in the superfluid helium and were observed by high-speed photography as they rose in the helium under buoyant forces. In earlier studies we found that MEBs created in this way had large amplitude oscillations and were unstable to decay. By creating MEBs at temperatures just under the lambda point, these oscillations are rapidly damped and the MEBs relax toward a spherical shape and stability as they rise in the helium.

  13. Is solid helium a supersolid?

    SciTech Connect

    Hallock, Robert

    2015-05-15

    Recent experiments suggest that helium-4 atoms can flow through an experimental cell filled with solid helium. But that incompletely understood flow is quite different from the reported superfluid-like motion that so excited physicists a decade ago.

  14. Helium-refrigeration system

    SciTech Connect

    Specht, J.R.; Millar, B.; Sutherland, A.

    1995-08-01

    The design, procurement, and preliminary construction was completed for adding two more wet expansion engines to two helium refrigerators. These will be added in mid-year FY 1995. In addition a variable speed drive will be added to an existing helium compressor. This is part of an energy conservation upgrade project to reduce operating costs from the use of electricity and liquid nitrogen. This project involves the replacement of Joule-Thompson valves in the refrigerators with expansion engines resulting in system efficiency improvements of about 30% and improved system reliability.

  15. Helium at White Dwarf Photospheric Conditions: Preliminary Laboratory Results

    NASA Astrophysics Data System (ADS)

    Schaeuble, M.; Falcon, R. E.; Gomez, T. A.; Winget, D. E.; Montgomery, M. H.; Bailey, J. E.

    2017-03-01

    We present preliminary results of an experimental study exploring helium at photospheric conditions of white dwarf stars. These data were collected at Sandia National Laboratories' Z-machine, the largest x-ray source on earth. Our helium results could have many applications ranging from validating current DB white dwarf model atmospheres to providing accurate He pressure shifts at varying temperatures and densities. In a much broader context, these helium data can be used to guide theoretical developments in new continuum-lowering models for two-electron atoms. We also discuss future applications of our updated experimental design, which enables us to sample a greater range of densities, temperatures, and gas compositions.

  16. Cavitation in flowing superfluid helium

    NASA Technical Reports Server (NTRS)

    Daney, D. E.

    1988-01-01

    Flowing superfluid helium cavitates much more readily than normal liquid helium, and there is a marked difference in the cavitation behavior of the two fluids as the lambda point is traversed. Examples of cavitation in a turbine meter and centrifugal pump are given, together with measurements of the cavitation strength of flowing superfluid helium. The unusual cavitation behavior of superfluid helium is attributed to its immense thermal conductivity .

  17. How to make Raman-inactive helium visible in Raman spectra of tritium-helium gas mixtures

    SciTech Connect

    Schloesser, M.; Pakari, O.; Rupp, S.; Mirz, S.; Fischer, S.

    2015-03-15

    Raman spectroscopy, a powerful method for the quantitative compositional analysis of molecular gases, e.g. mixtures of hydrogen isotopologues, is not able to detect monoatomic species like helium. This deficit can be overcome by using radioluminescence emission from helium atoms induced by β-electrons from tritium decay. We present theoretical considerations and combined Raman/radioluminescence spectra. Furthermore, we discuss the linearity of the method together with validation measurements for determining the pressure dependence. Finally, we conclude how this technique can be used for samples of helium with traces of tritium, and vice versa. (authors)

  18. Transitions of an atmospheric-pressure diffuse dielectric barrier discharge in helium for frequencies increasing from kHz to MHz

    NASA Astrophysics Data System (ADS)

    Boisvert, J.-S.; Margot, J.; Massines, F.

    2017-03-01

    Recent studies have shown that tuning a dielectric barrier discharge (DBD) in the medium-frequency range (MF: from 0.3 to 3 MHz) allows a low-power and a high-power mode to be sustained. In the present article the effect of the driving frequency on a DBD is studied from the low-frequency range (LF: from 30 to 300 kHz) to the high-frequency range (HF: from 3 to 30 MHz). This is achieved using fast imaging together with electrical and spectroscopic diagnostics. At every frequency, a diffuse discharge is sustained. It is observed that at 25 kHz the discharge is an atmospheric-pressure glow discharge (APGD) while at 15 MHz the discharge behaves as a capacitive discharge in the RF-α mode. The usual LF APGD behavior is observed up to 100 kHz. Above 200 kHz, the positive column remains during the whole cycle so that the hybrid mode is sustained. At 5 MHz, the hybrid mode finally turns into the RF-α mode. In addition to the LF APGD, RF-α and hybrid modes obtained when the applied voltage is significantly higher than the ignition value, two other modes can be reached at low applied voltage. A Townsend-like mode is achieved from 50 to 100 kHz while in the medium-frequency range, the Ω mode is sustained. Moreover, only from 1.0 to 2.7 MHz there is a large hysteresis occurring when the discharge transits back and forth from the Ω to the hybrid mode. It is also found that when the frequency increases from 25 kHz to 15 MHz, the rms current increases over two orders of magnitudes while the rms voltage decreases by about 60%. The gas temperature estimated from N2 rotational spectra is always close to room temperature but the discharge is more energy efficient (in the HF range) as a lower fraction of energy turns into gas heating.

  19. Gaseous Flows in Microchannels

    NASA Astrophysics Data System (ADS)

    Graur, I. A.; Méolans, J. G.; Zeitoun, D. E.

    2005-05-01

    The objective of this study is to broaden the fundamental understanding of the emerging field of microfluidics especially in a long channel. The quasi gasdynamic (QGD) equations, originally developed on the basis of a kinetical model are used for numerical and analytical simulation. A two-dimensional analysis of the QGD equations with a first order slip velocity boundary conditions demonstrates that both compressibility and rarefied effects are present in long microchannels. Analytical solutions for the pressure and the velocity profiles are derived from the quasi gasdynamic equations by undertaking perturbation expansions according to a small parameter ɛ (the height-to-length ratio of the channel) and using the isothermal flow assumption. The deduced expression for the mass flow rate is similar to the analytical expression obtained from the Navier-Stokes equations with a second order slip boundary condition and gives results in agreement with the measurements. The effects of the rarefaction and of the compressibility on pressure distributions are analyzed. The analytical expression of the pressure predicts accurately the measured pressure distribution. The Knudsen numbers calculated at the exit of the channel and based on the channel height vary from 10-3 to 0.4. The comparisons of analytical and numerical solutions confirm the validity of the analytical approach.

  20. Producing and imaging a thin line of He*₂ molecular tracers in helium-4.

    PubMed

    Gao, J; Marakov, A; Guo, W; Pawlowski, B T; Van Sciver, S W; Ihas, G G; McKinsey, D N; Vinen, W F

    2015-09-01

    Cryogenic helium-4 has long been recognized as a useful material in fluids research. The unique properties of helium-4 in the gaseous phase and the normal liquid phase allow for the generation of turbulent flows with exceptionally high Reynolds and Rayleigh numbers. In the superfluid phase, helium-4 exhibits two-fluid hydrodynamics and possesses fascinating properties due to its quantum nature. However, studying the flows in helium-4 has been very challenging largely due to the lack of effective visualization and velocimetry techniques. In this article, we discuss the development of novel instrumentation for flow-visualization in helium based on the generation and imaging of thin lines of metastable He*₂ tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. By observing the displacement and distortion of the tracer lines in helium, quantitative information about the flow field can be extracted. We present experimental results in the study of thermal counterflow in superfluid helium that validate the concept of this technique. We also discuss anticipated future developments of this powerful visualization technique.

  1. Development of a Flexible Seal for a 60 psi Cryogenic Pressure Box

    NASA Technical Reports Server (NTRS)

    Glass, David E.

    1998-01-01

    A cryogenic pressure box test facility has been designed and fabricated for use at NASA Langley Research Center (LaRC) to subject 5 ft x 6 ft curved panels to cryogenic temperatures and biaxial tensile loads. The cryogenic pressure box is capable of testing curved panels down to -423 F (20 K) with 54 psig maximum pressure. The key challenge in the design and fabrication of the pressure box was the development of a seal that could remain flexible at -423 F and contain 60 psi gaseous helium as the pressurization gas. A C-shaped seal was developed using a Gore-tex woven fabric. Mechanical testing of the fabric at room and elevated temperature, liquid nitrogen temperature, and liquid helium temperature demonstrated the strength and creep resistance of the material over the desired operating range. A small scale cryogenic pressure box was used to test prototype seals at cryogenic temperatures up to 60 psi. Preliminary tests indicated that excessive leakage was present through the seal. As a result, an aluminized mylar liner was placed inside the Gore-tex seal to reduce leakage through the seal. The final seal configuration resulted in minimal pressure loss during seal testing.

  2. Superconducting cable cooling system by helium gas and a mixture of gas and liquid helium

    DOEpatents

    Dean, John W.

    1977-01-01

    Thermally contacting, oppositely streaming cryogenic fluid streams in the same enclosure in a closed cycle that changes from a cool high pressure helium gas to a cooler reduced pressure helium fluid comprised of a mixture of gas and boiling liquid so as to be near the same temperature but at different pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T.sub.1. By first circulating the fluid in a go leg from a refrigerator at one end of the line as a high pressure helium gas near the normal boiling temperature of helium; then circulating the gas through an expander at the other end of the line where the gas becomes a mixture of reduced pressure gas and boiling liquid at its boiling temperature; then by circulating the mixture in a return leg that is separated from but in thermal contact with the gas in the go leg and in the same enclosure therewith; and finally returning the resulting low pressure gas to the refrigerator for compression into a high pressure gas at T.sub.2 is a closed cycle, where T.sub.1 >T.sub.2, the temperature distribution is such that the line temperature is nearly constant along its length from the refrigerator to the expander due to the boiling of the liquid in the mixture. A heat exchanger between the go and return lines removes the gas from the liquid in the return leg while cooling the go leg.

  3. Helium anion formation inside helium droplets

    NASA Astrophysics Data System (ADS)

    Jabbour Al Maalouf, Elias; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed.

  4. Gas Requirements in Pressurized Transfer of Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Gluck, D. F.; Kline, J. F.

    1961-01-01

    Of late, liquid hydrogen has become a very popular fuel for space missions. It is being used in such programs as Centaur and Saturn. Furthermore, hydrogen is the ideal working fluid for nuclear powered space vehicles currently under development. In these applications, liquid hydrogen fuel is generally transferred to the combustion chamber by a combination of pumping and pressurization. The pump forces the liquid propellant from the fuel tank to the combustion chamber; gaseous pressurant holds tank pressure sufficiently high to prevent cavitation at the pump inlet and to maintain the structural rigidity of the tank. The pressurizing system, composed of pressurant, tankage, and associated hardware can be a large portion of the total vehicle weight. Pressurant weight can be reduced by introducing the pressurizing gas at temperatures substantially greater than those of liquid hydrogen. Heat and mass transfer processes thereby induced complicate gas requirements during discharge. These requirements must be known to insure proper design of the pressurizing system. The aim of this paper is to develop from basic mass and energy transfer processes a general method to predict helium and hydrogen gas usage for the pressurized transfer of liquid hydrogen. This required an analytical and experimental investigation, the results of which are described in this paper.

  5. Production of carbon monoxide-free hydrogen and helium from a high-purity source

    DOEpatents

    Golden, Timothy Christopher; Farris, Thomas Stephen

    2008-11-18

    The invention provides vacuum swing adsorption processes that produce an essentially carbon monoxide-free hydrogen or helium gas stream from, respectively, a high-purity (e.g., pipeline grade) hydrogen or helium gas stream using one or two adsorber beds. By using physical adsorbents with high heats of nitrogen adsorption, intermediate heats of carbon monoxide adsorption, and low heats of hydrogen and helium adsorption, and by using vacuum purging and high feed stream pressures (e.g., pressures of as high as around 1,000 bar), pipeline grade hydrogen or helium can purified to produce essentially carbon monoxide -free hydrogen and helium, or carbon monoxide, nitrogen, and methane-free hydrogen and helium.

  6. Helium solubility in SON68 nuclear waste glass

    SciTech Connect

    Fares, Toby; Peuget, Sylvain; Bouty, Olivier; Broudic, Veronique; Maugeri, Emilio; Bes, Rene; Jegou, Christophe; Chamssedine, Fadel; Sauvage, Thierry; Deschanels, Xavier

    2012-12-15

    Helium behavior in a sodium borosilicate glass (SON68) dedicated to the immobilization of high-level nuclear waste is examined. Two experimental approaches on nonradioactive glass specimens are implemented: pressurized helium infusion experiments and {sup 3}He ion implantation experiments. The temperature variation of helium solubility in SON68 glass was determined and analyzed with the harmonic oscillator model to determine values of the energy of interaction E(0) at the host sites (about -4000 J/mol), the vibration frequency (about 1.7 x 10{sup 11} s{sup -1}), and the density of solubility sites (2.2 x 10{sup 21} sites cm{sup -3}). The implantation experiments show that a non diffusive transport phenomenon (i.e., athermal diffusion) is involved in the material when the helium concentration exceeds 2.3 x 10{sup 21} He cm{sup -3}, and thus probably as soon as it exceeds the density of solubility sites accessible to helium in the glass. We propose that this transport mechanism could be associated with the relaxation of the stress gradient induced by the implanted helium profile, which is favored by the glass damage. Microstructural characterization by TEM and ESEM of glass specimens implanted with high helium concentrations showed a homogeneous microstructure free of bubbles, pores, or cracking at a scale of 10 nm. (authors)

  7. Pyrolysis of white birch (Betula papyrifera marsh) in nitrogen and helium up to 900 degrees C and 600 kilopascals in the presence of water vapor, zinc (II) chromite, and iron (III) oxide

    SciTech Connect

    Fong, P.; Ross, R.A.

    1980-01-01

    The thermal decomposition of white birch (Betula papyrifera) sawdust has been studied up to 900 degrees C and 600 kilopascals pressure in nitrogen and helium by thermogravimetry, gas chromatography, and scanning electron microscopy. Kinetic parameters and the gaseous products of pyrolysis have been identified. Comparative data were determined in helium/water vapor atmospheres and the effects of the solid additives iron (III) oxide, 10.2 percent, and zinc (II) chromite, 14.1 percent, studied to examine the scope of possible catalytic influences on key reaction steps in the overall decomposition. Reaction-rate measurements indicated that the pyrolysis was most likely transport-controlled and that the values of the principal kinetic parameters were unaffected by the presence of the solid additives. However, water vapor, and these solids in concert with water vapor, did appreciably influence the nature and proportions of the gaseous products formed in the decomposition. Thus, for example, iron (III) oxide increased the CH/sub 4//CO, H/sub 2//CO, and CO/sub 2//CO product ratios to significantly higher levels while zinc (II)-chromite had the reverse effect. These phenomena are discussed and explained in terms of possible catalytic influence on the water-gas shift and allied secondary reactions, which are believed to be important in determining the course of the decomposition. (Refs. 17).

  8. High energy chlorine for chlorine substitution involving Walden inversion in gaseous enantiomers

    NASA Astrophysics Data System (ADS)

    To, Kar-Chun; Rack, E. P.; Wolf, A. P.

    1981-01-01

    The reactions of 34mCl- for cl substitution in gaseous 2(S)-(+)- a and 2(R)-(-)-chloro-1-propanol are reported at various system pressures and in the presence of neon moderator and a radical scavenger. (AIP).

  9. Metal hydride differential scanning calorimetry as an approach to compositional determination of mixtures of hydrogen isotopologues and helium

    SciTech Connect

    Robinson, David B.; Luo, Weifang; Cai, Trevor Y.; Stewart, Kenneth D.

    2015-09-26

    Gaseous mixtures of diatomic hydrogen isotopologues and helium are often encountered in the nuclear energy industry and in analytical chemistry. Compositions of stored mixtures can vary due to interactions with storage and handling materials. When tritium is present, it decays to form ions and helium-3, both of which can lead to further compositional variation. Monitoring of composition is typically achieved by mass spectrometry, a method that is bulky and energy-intensive. Mass spectrometers disperse sample material through vacuum pumps, which is especially troublesome if tritium is present. Moreover, our ultimate goal is to create a compact, fast, low-power sensor that can determine composition with minimal gas consumption and waste generation, as a complement to mass spectrometry that can be instantiated more widely. We propose calorimetry of metal hydrides as an approach to this, due to the strong isotope effect on gas absorption, and demonstrate the sensitivity of measured heat flow to atomic composition of the gas. Peak shifts are discernible when mole fractions change by at least 1%. A mass flow restriction results in a unique dependence of the measurement on helium concentration. We present a mathematical model as a first step toward prediction of the peak shapes and positions. The model includes a useful method to compute estimates of phase diagrams for palladium in the presence of arbitrary mixtures of hydrogen isotopologues. As a result, we expect that this approach can be used to deduce unknown atomic compositions from measured calorimetric data over a useful range of partial pressures of each component.

  10. Metal hydride differential scanning calorimetry as an approach to compositional determination of mixtures of hydrogen isotopologues and helium

    DOE PAGES

    Robinson, David B.; Luo, Weifang; Cai, Trevor Y.; ...

    2015-09-26

    Gaseous mixtures of diatomic hydrogen isotopologues and helium are often encountered in the nuclear energy industry and in analytical chemistry. Compositions of stored mixtures can vary due to interactions with storage and handling materials. When tritium is present, it decays to form ions and helium-3, both of which can lead to further compositional variation. Monitoring of composition is typically achieved by mass spectrometry, a method that is bulky and energy-intensive. Mass spectrometers disperse sample material through vacuum pumps, which is especially troublesome if tritium is present. Moreover, our ultimate goal is to create a compact, fast, low-power sensor that canmore » determine composition with minimal gas consumption and waste generation, as a complement to mass spectrometry that can be instantiated more widely. We propose calorimetry of metal hydrides as an approach to this, due to the strong isotope effect on gas absorption, and demonstrate the sensitivity of measured heat flow to atomic composition of the gas. Peak shifts are discernible when mole fractions change by at least 1%. A mass flow restriction results in a unique dependence of the measurement on helium concentration. We present a mathematical model as a first step toward prediction of the peak shapes and positions. The model includes a useful method to compute estimates of phase diagrams for palladium in the presence of arbitrary mixtures of hydrogen isotopologues. As a result, we expect that this approach can be used to deduce unknown atomic compositions from measured calorimetric data over a useful range of partial pressures of each component.« less

  11. Auroral helium precipitation.

    NASA Technical Reports Server (NTRS)

    Axford, W. I.; Chivers, H. J. A.; Eberhardt, P.; Geiss, J.; Buehler, F.

    1972-01-01

    Application of the metal foil sampling technique, which has been used to measure helium, neon, and argon fluxes in the solar wind, to the problem of measuring the fluxes of these gases in the auroral primary radiation. Aluminum and platinum foils have been flown into two bright auroras and have been recovered. The foils have been analyzed for helium and neon isotopes with a mass spectrometer; so far only He4 has been detected. In the first flight the precipitating flux of He4 with particle energies above about 1 keV was approximately 1,000,000 per sq cm per sec, and the backscattered flux was smaller by about a factor of 10. In the second flight the aurora was less bright, and the He4 fluxes were lower by a factor of about 2. A rough analysis suggests that the mean energy of the incident particles was greater than 3 keV.

  12. Helium-cold induced hypothermia in the white rat.

    NASA Technical Reports Server (NTRS)

    Musacchia, X. J.; Jacobs, M.

    1973-01-01

    Hypothermia was induced in white rats by exposing them to low ambient temperatures (about 0 C) and a gaseous atmosphere of 80% helium and 20% oxygen (helox). Biological survival, in which revival from hypothermia to normothermia is achieved, and clinical survival, in which one or more functional attributes are monitored in the hypothermic animal until it dies, are examined. The helium-cold method appears to produce a hypothermic state in the rat quite similar to that resulting from such techniques as ice water immersion or hypercapnia + hypoxia. There is a direct relationship between body weight and percent survival. Despite the fact that they require a longer period to become hypothermic, the heavier animals are better able to survive.

  13. Evaluation of helium cooling for fusion divertors

    SciTech Connect

    Baxi, C.B.

    1993-09-01

    The divertors of future fusion reactors will have a power throughput of several hundred MW. The peak heat flux on the diverter surface is estimated to be 5 to 15 MW/m{sup 2} at an average heat flux of 2 MW/m{sup 2}. The divertors have a requirement of both minimum temperature (100{degrees}C) and maximum temperature. The minimum temperature is dictated by the requirement to reduce the absorption of plasma, and the maximum temperature is determined by the thermo-mechanical properties of the plasma facing materials. Coolants that have been considered for fusion reactors are water, liquid metals and helium. Helium cooling has been shown to be very attractive from safety and other considerations. Helium is chemically and neutronically inert and is suitable for power conversion. The challenges associated with helium cooling are: (1) Manifold sizes; (2) Pumping power; and (3) Leak prevention. In this paper the first two of the above design issues are addressed. A variety of heat transfer enhancement techniques are considered to demonstrate that the manifold sizes and the pumping power can be reduced to acceptable levels. A helium-cooled diverter module was designed and fabricated by GA for steady-state heat flux of 10 MW/m{sup 2}. This module was recently tested at Sandia National Laboratories. At an inlet pressure of 4 MPa, the module was tested at a steady-state heat flux of 10 MW/m{sup 2}. The pumping power required was less than 1% of the power removed. These results verified the design prediction.

  14. Characteristics of response factors of coaxial gaseous rocket injectors

    NASA Technical Reports Server (NTRS)

    Janardan, B. A.; Daniel, B. R.; Zinn, B. T.

    1975-01-01

    The results of an experimental investigation undertaken to determine the frequency dependence of the response factors of various gaseous propellant rocket injectors subject to axial instabilities are presented. The injector response factors were determined, using the modified impedance-tube technique, under cold-flow conditions simulating those observed in unstable rocket motors. The tested injectors included a gaseous-fuel injector element, a gaseous-oxidizer injector element and a coaxial injector with both fuel and oxidizer elements. Emphasis was given to the determination of the dependence of the injector response factor upon the open-area ratio of the injector, the length of the injector orifice, and the pressure drop across the injector orifices. The measured data are shown to be in reasonable agreement with the corresponding injector response factor data predicted by the Feiler and Heidmann model.

  15. Helium penetrates into silica glass and reduces its compressibility.

    PubMed

    Sato, Tomoko; Funamori, Nobumasa; Yagi, Takehiko

    2011-06-14

    SiO(2) glass has a network structure with a significant amount of interstitial voids. Gas solubilities in silicates are expected to become small under high pressure due to compaction of voids. Here we show anomalous behaviour of SiO(2) glass in helium. Volume measurements clarify that SiO(2) glass is much less compressible than normal when compressed in helium, and the volume in helium at 10 GPa is close to the normal volume at 2 GPa. X-ray diffraction and Raman scattering measurements suggest that voids are prevented from contracting when compressed in helium because helium penetrates into them. The estimated helium solubility is very high and is between 1.0 and 2.3 mol per mole of SiO(2) glass at 10 GPa, which shows marked contrast with previous models. These results may have implications for discussions of the Earth's evolution as well as interpretations of various high-pressure experiments, and also lead to the creation of new materials.

  16. Applications of Groundwater Helium

    USGS Publications Warehouse

    Kulongoski, Justin T.; Hilton, David R.

    2011-01-01

    Helium abundance and isotope variations have widespread application in groundwater-related studies. This stems from the inert nature of this noble gas and the fact that its two isotopes ? helium-3 and helium-4 ? have distinct origins and vary widely in different terrestrial reservoirs. These attributes allow He concentrations and 3He/4He isotope ratios to be used to recognize and quantify the influence of a number of potential contributors to the total He budget of a groundwater sample. These are atmospheric components, such as air-equilibrated and air-entrained He, as well as terrigenic components, including in situ (aquifer) He, deep crustal and/or mantle He and tritiogenic 3He. Each of these components can be exploited to reveal information on a number of topics, from groundwater chronology, through degassing of the Earth?s crust to the role of faults in the transfer of mantle-derived volatiles to the surface. In this review, we present a guide to how groundwater He is collected from aquifer systems and quantitatively measured in the laboratory. We then illustrate the approach of resolving the measured He characteristics into its component structures using assumptions of endmember compositions. This is followed by a discussion of the application of groundwater He to the types of topics mentioned above using case studies from aquifers in California and Australia. Finally, we present possible future research directions involving dissolved He in groundwater.

  17. Education in Helium Refrigeration

    NASA Astrophysics Data System (ADS)

    Gistau Baguer, G. M.

    2004-06-01

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics… and so on. Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity.

  18. Education in Helium Refrigeration

    SciTech Connect

    Gistau Baguer, G. M.

    2004-06-23

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics... and so on.Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity.

  19. Helium anion formation inside helium droplets

    NASA Astrophysics Data System (ADS)

    Maalouf, Elias Jabbour Al; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  20. The winter helium bulge revisited

    NASA Astrophysics Data System (ADS)

    Liu, Xianjing; Wang, Wenbin; Thayer, Jeffrey P.; Burns, Alan; Sutton, Eric; Solomon, Stanley C.; Qian, Liying; Lucas, Greg

    2014-10-01

    A newly implemented helium module in the National Center for Atmospheric Research-Thermosphere Ionosphere Electrodynamics general circulation model offers the first opportunity in three decades to describe helium behavior in the context of a first principles, self-consistent model and to test early theories of wintertime helium bulge formation. This study shows general agreement with the findings of Reber and Hays (1973) but articulates the definitive role of vertical advection in the bulge formation. Our findings indicate vertical advection and molecular diffusion are the dominate processes responsible for the solstice helium distribution. Horizontal winds indirectly contribute to the helium bulge formation by their divergent wind field that leads to vertical winds in order to maintain thermosphere mass continuity. As a minor gas, thermospheric helium does not contribute to mass continuity and its distribution is dictated by more local interactions and constraints.

  1. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Helium and Helium Usage Data. 52.208-8 Section 52.208-8 Federal Acquisition Regulations System FEDERAL... Provisions and Clauses 52.208-8 Required Sources for Helium and Helium Usage Data. As prescribed in 8.505, insert the following clause: Required Sources for Helium and Helium Usage Data (APR 2002) (a)...

  2. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Helium and Helium Usage Data. 52.208-8 Section 52.208-8 Federal Acquisition Regulations System FEDERAL... Provisions and Clauses 52.208-8 Required Sources for Helium and Helium Usage Data. As prescribed in 8.505, insert the following clause: Required Sources for Helium and Helium Usage Data (APR 2002) (a)...

  3. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Helium and Helium Usage Data. 52.208-8 Section 52.208-8 Federal Acquisition Regulations System FEDERAL... Provisions and Clauses 52.208-8 Required Sources for Helium and Helium Usage Data. As prescribed in 8.505, insert the following clause: Required Sources for Helium and Helium Usage Data (APR 2002) (a)...

  4. Vacancy-induced flow of solid helium

    NASA Astrophysics Data System (ADS)

    Benedek, Giorgio; Kalinin, Anton; Nieto, Pablo; Toennies, J. Peter

    2016-03-01

    The pulsed flow of solid 4He through a narrow capillary in a flow system which issues into vacuum is investigated at temperatures between 1.64 and 2.66 K and pressures between 54 and 104 bars. After each pulse three different capillary flow regimes are observed as the upstream pressure decreases: an oscillatory [mini-geyser (MG)] regime, a constant flow (CF) regime with a linearly decreasing pressure difference, and a nonresistant (NR) regime. A quantitative analysis of the three regimes suggests that the flow of solid 4He is driven by a counterflow of excess vacancies, which are injected downstream of the capillary at the solid/liquid interface near the micrometric orifice exposed to vacuum. The CF regime, where the flow velocity is found to be independent of the pressure difference, and the NR regime, where the solid flows as a Bernoulli fluid, suggest a new dynamic phase of solid helium induced by a steady influx of vacancies.

  5. Method and means for helium/hydrogen ratio measurement by alpha scattering

    NASA Technical Reports Server (NTRS)

    Whitehead, A. B.; Tombrello, T. A. (Inventor)

    1980-01-01

    An apparatus for determining helium to hydrogen ratios in a gaseous sample is presented. The sample is bombarded with alpha particles created by a self contained radioactive source and scattering products falling within a predetermined forward scattering angular range impact a detector assembly. Two detectors are mounted in tandem, the first completely blocking the second with respect to incident scattering products. Alpha particle/hydrogen or alpha particle/helium collisions are identified by whether scattering product impacts occur simultaneously in both detectors or only in the first detector. Relative magnitudes of the two pulses can be used to further discriminate against other effects such as noise and cosmic ray events.

  6. Influence of gaseous hydrogen on metals

    NASA Technical Reports Server (NTRS)

    Walter, R. J.; Chandler, W. T.

    1973-01-01

    Tensile, fracture toughness, threshold stress intensity for sustained-load crack growth, and cyclic and sustained load crack growth rate measurements were performed on a number of alloys in high-pressure hydrogen and helium environments. The results of tensile tests performed in 34.5 MN/m2 (5000 psi) hydrogen indicated that Inconel 625 was considerable embrittled at ambient temperature but was not embrittled at 144 K (-200 F). The tensile properties of AISI 321 stainless steel were slightly reduced at ambient temperature and 144 K (-200 F). The tensile properties of Ti-5Al-2.5 Sn ELI were essentially unaffected by hydrogen at 144 K (-200 F). OFHC copper was not embrittled by hydrogen at ambient temperature or at 144 K (-200 F).

  7. External tank gaseous oxygen line simulated lightning tests

    NASA Technical Reports Server (NTRS)

    Smith, H. E.; Avery, R. M.

    1976-01-01

    Tests were made to evaluate the effects of lightning strikes on the shuttle external tank gaseous oxygen pressurization line. This line, designed to conduct gaseous oxygen may also act as a lightning conductor. Questions have been raised as to the potential hazard of this line as a lightning conductor with speculation as to the damage that might occur to the pressurization line, and the adjacent thermal protective surfaces, from a lightning strike. The region of investigation was from above the cone of the launch tower lightning protection to 15.24 km (50, 000 ft) altitude. Tests were performed on samples of thin wall stainless steel tubing filled with gaseous oxygen under simulated flight conditions. No specimen malfunctions occurred when the tests were conducted according to JSC specifications. Based on the JSC specifications and the results of these tests, it is concluded that a lightning strike will not cause a malfunction of the shuttle external tank gaseous oxygen line made of the representative material tested.

  8. The use of Vacutainer tubes for collection of soil samples for helium analysis

    USGS Publications Warehouse

    Hinkle, Margaret E.; Kilburn, James E.

    1979-01-01

    Measurements of the helium concentration of soil samples collected and stored in Vacutainer-brand evacuated glass tubes show that Vacutainers are reliable containers for soil collection. Within the limits of reproducibility, helium content of soils appears to be independent of variations in soil temperature, barometric pressure, and quantity of soil moisture present in the sample.

  9. Growth rate effects on the formation of dislocation loops around deep helium bubbles in Tungsten

    DOE PAGES

    Sandoval, Luis; Perez, Danny; Uberuaga, Blas P.; ...

    2016-11-15

    Here, the growth process of spherical helium bubbles located 6 nm below a (100) surface is studied using molecular dynamics and parallel replica dynamics simulations, over growth rates from 106 to 1012 helium atoms per second. Slower growth rates lead to a release of pressure and lower helium content as compared with fast growth cases. In addition, at slower growth rates, helium bubbles are not decorated by multiple dislocation loops, as these tend to merge or emit given sufficient time. At faster rates, dislocation loops nucleate faster than they can emit, leading to a more complicated dislocation structure around themore » bubble.« less

  10. Growth rate effects on the formation of dislocation loops around deep helium bubbles in Tungsten

    SciTech Connect

    Sandoval, Luis; Perez, Danny; Uberuaga, Blas P.; Voter, Arthur Ford

    2016-11-15

    Here, the growth process of spherical helium bubbles located 6 nm below a (100) surface is studied using molecular dynamics and parallel replica dynamics simulations, over growth rates from 106 to 1012 helium atoms per second. Slower growth rates lead to a release of pressure and lower helium content as compared with fast growth cases. In addition, at slower growth rates, helium bubbles are not decorated by multiple dislocation loops, as these tend to merge or emit given sufficient time. At faster rates, dislocation loops nucleate faster than they can emit, leading to a more complicated dislocation structure around the bubble.

  11. Helium heater design for the helium direct cycle component test facility. [for gas-cooled nuclear reactor power plant

    NASA Technical Reports Server (NTRS)

    Larson, V. R.; Gunn, S. V.; Lee, J. C.

    1975-01-01

    The paper describes a helium heater to be used to conduct non-nuclear demonstration tests of the complete power conversion loop for a direct-cycle gas-cooled nuclear reactor power plant. Requirements for the heater include: heating the helium to a 1500 F temperature, operating at a 1000 psia helium pressure, providing a thermal response capability and helium volume similar to that of the nuclear reactor, and a total heater system helium pressure drop of not more than 15 psi. The unique compact heater system design proposed consists of 18 heater modules; air preheaters, compressors, and compressor drive systems; an integral control system; piping; and auxiliary equipment. The heater modules incorporate the dual-concentric-tube 'Variflux' heat exchanger design which provides a controlled heat flux along the entire length of the tube element. The heater design as proposed will meet all system requirements. The heater uses pressurized combustion (50 psia) to provide intensive heat transfer, and to minimize furnace volume and heat storage mass.

  12. Rayleigh Scattering by Helium in Stellar Atmospheres

    NASA Astrophysics Data System (ADS)

    Fišák, J.; Kubát, J.; Krtička, J.

    2017-02-01

    We study the influence of Rayleigh scattering by helium on synthetic spectra and stellar atmosphere models. Rayleigh scattering by helium is often neglected in hot star atmosphere models. This approximation is justified by the small population of helium in stars with solar composition (about 10% by number) and lower Rayleigh scattering total cross section of helium with respect to neutral hydrogen. However, for stars with large helium abundances Rayleigh scattering by helium can be a significant opacity source.

  13. Burnett Simulations of Gaseous Flows in Transition Regime

    NASA Astrophysics Data System (ADS)

    Wang, J. X.; Bao, F. B.; Lin, J. Z.

    2011-09-01

    Burnett equations with the slip boundary conditions are used to study the three-dimensional gaseous flow in slip and transition regime. The results were first compared with those of DSMC method and good agreements were achieved. The effects of inlet to outlet pressure ratios and Knudsen numbers on flow characteristics were analyzed. The compressible effect increases the pressure nonlinear distribution while the rarefied effect reduces the nonlinear trend. With the same pressure ratio and cross-section area, the flow rate decreases with the increase of aspect ratio.

  14. Helium-volume dynamics of Upper Freeport coal powder and lumps

    SciTech Connect

    Romanov, Vyacheslav; Soong, Yee

    2009-01-01

    Exposure to 7 MPa of helium at room temperature alters the texture of Upper Freeport coal in a lump form. The differences in texture and porosity between coal powder and lumps may affect the transport and interaction of fluids and coal. In this work, the information about the coal texture and micro- and meso-porosity was obtained via the BET, BJH, and Dubinin-Astakhov analyses. We further investigated the free-fluid-phase volume (free-volume) effects due to helium interaction with the powder and the lumps. During the manometric experiment, helium penetration into the dry coal matrix resulted in slow relaxation of pressure. After exposure of coal to helium, there have been no significant changes of the macroscopic dimensions observed and the relaxation process can be attributed to microscopic 'freevolume' effects. Evolution of the sorption-desorption rates indicates that exposure to helium may change the texture and apparent (helium) density of dry coal.

  15. Helium-volume dynamics of Upper Freeport coal powder and lumps

    SciTech Connect

    Romanov, V.N.; Soong, Yee

    2009-01-01

    Exposure to 7 MPa of helium at room temperature alters the texture of Upper Freeport coal in a lump form. The differences in texture and porosity between coal powder and lumps may affect the transport and interaction of fluids and coal. In this work, the information about the coal texture and micro- and meso-porosity was obtained via the BET, BJH, and Dubinin–Astakhov analyses. We further investigated the free-fluid-phase volume (free-volume) effects due to helium interaction with the powder and the lumps. During the manometric experiment, helium penetration into the dry coal matrix resulted in slow relaxation of pressure. After exposure of coal to helium, there have been no significant changes of the macroscopic dimensions observed and the relaxation process can be attributed to microscopic ‘free-volume’ effects. Evolution of the sorption–desorption rates indicates that exposure to helium may change the texture and apparent (helium) density of dry coal.

  16. Helium dilution refrigeration system

    DOEpatents

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  17. Helium dilution refrigeration system

    DOEpatents

    Roach, Patrick R.; Gray, Kenneth E.

    1988-01-01

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

  18. Gaseous fuel nuclear reactor research

    NASA Technical Reports Server (NTRS)

    Schwenk, F. C.; Thom, K.

    1975-01-01

    Gaseous-fuel nuclear reactors are described; their distinguishing feature is the use of fissile fuels in a gaseous or plasma state, thereby breaking the barrier of temperature imposed by solid-fuel elements. This property creates a reactor heat source that may be able to heat the propellant of a rocket engine to 10,000 or 20,000 K. At this temperature level, gas-core reactors would provide the breakthrough in propulsion needed to open the entire solar system to manned and unmanned spacecraft. The possibility of fuel recycling makes possible efficiencies of up to 65% and nuclear safety at reduced cost, as well as high-thrust propulsion capabilities with specific impulse up to 5000 sec.

  19. Helium diffusion in carbonates

    NASA Astrophysics Data System (ADS)

    Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  20. Recent topics on gaseous detectors

    NASA Astrophysics Data System (ADS)

    Sauli, Fabio

    2010-11-01

    Started in the late sixties by the invention of the multi-wire proportional chamber (MWPC), the development of modern gaseous detectors has continued for decades and is still blooming, with the introduction of new generations of innovative devices having superior position accuracy, time resolutions and rate capability. Motivated mostly by the requirements of high energy physics, the novel devices find however applications in many other fields, such as astrophysics and medical diagnostics.

  1. Recent work on gaseous detonations

    NASA Astrophysics Data System (ADS)

    Nettleton, M. A.

    The paper reviews recent progress in the field of gaseous detonations, with sections on shock diffraction and reflection, the transition to detonation, hybrid, spherically-imploding, and galloping and stuttering fronts, their structure, their transmission and quenching by additives, the critical energy for initiation and detonation of more unusual fuels. The final section points out areas where our understanding is still far from being complete and contains some suggestions of ways in which progress might be made.

  2. Gaseous Nitrogen Orifice Mass Flow Calculator

    NASA Technical Reports Server (NTRS)

    Ritrivi, Charles

    2013-01-01

    The Gaseous Nitrogen (GN2) Orifice Mass Flow Calculator was used to determine Space Shuttle Orbiter Water Spray Boiler (WSB) GN2 high-pressure tank source depletion rates for various leak scenarios, and the ability of the GN2 consumables to support cooling of Auxiliary Power Unit (APU) lubrication during entry. The data was used to support flight rationale concerning loss of an orbiter APU/hydraulic system and mission work-arounds. The GN2 mass flow-rate calculator standardizes a method for rapid assessment of GN2 mass flow through various orifice sizes for various discharge coefficients, delta pressures, and temperatures. The calculator utilizes a 0.9-lb (0.4 kg) GN2 source regulated to 40 psia (.276 kPa). These parameters correspond to the Space Shuttle WSB GN2 Source and Water Tank Bellows, but can be changed in the spreadsheet to accommodate any system parameters. The calculator can be used to analyze a leak source, leak rate, gas consumables depletion time, and puncture diameter that simulates the measured GN2 system pressure drop.

  3. Influence of gaseous hydrogen on the mechanical properties of incoloy 903. [gas-metal interactions/iron alloys

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Solid specimens of the alloy Inconel 903 (iron based alloy) were exposed to four gaseous environments and high temperatures. Air, pure helium, pure hydrogen, and hydrogen and water vapor combined were the gaseous environments employed, and the temperature was 1400 F. Various mechanical property tests (low cycle fatigue, creep-rupture, tensile properties) were performed on the alloy. Results indicate that the hydrogen and water vapor environment cause a sharp reduction in the mechanical properties of the alloy. Photographs of the test equipment used and the microstructure of the tested alloy are included.

  4. Test program, helium II orbital resupply coupling

    NASA Technical Reports Server (NTRS)

    Hyatt, William S.

    1991-01-01

    The full scope of this program was to have included development tests, design and production of custom test equipment and acceptance and qualification testing of prototype and protoflight coupling hardware. This program was performed by Ball Aerospace Systems Division, Boulder, Colorado until its premature termination in May 1991. Development tests were performed on cryogenic face seals and flow control devices at superfluid helium (He II) conditions. Special equipment was developed to allow quantified leak detection at large leak rates up to 8.4 x 10(exp -4) SCCS. Two major fixtures were developed and characterized: The Cryogenic Test Fixture (CTF) and the Thermal Mismatch Fixture (Glovebox). The CTF allows the coupling hardware to be filled with liquid nitrogen (LN2), liquid helium (LHe) or sub-cooled liquid helium when hardware flow control valves are either open or closed. Heat leak measurements, internal and external helium leakage measurements, cryogenic proof pressure tests and external load applications are performed in this fixture. Special reusable MLI closures were developed to provide repeatable installations in the CTF. The Thermal Mismatch Fixture allows all design configurations of coupling hardware to be engaged and disengaged while measuring applied forces and torques. Any two hardware components may be individually thermally preconditioned within the range of 117 deg K to 350 deg K prior to engage/disengage cycling. This verifies dimensional compatibility and operation when thermally mismatched. A clean, dry GN2 atmosphere is maintained in the fixture at all times. The first shipset of hardware was received, inspected and cycled at room temperature just prior to program termination.

  5. Test program, helium II orbital resupply coupling

    NASA Astrophysics Data System (ADS)

    Hyatt, William S.

    1991-12-01

    The full scope of this program was to have included development tests, design and production of custom test equipment and acceptance and qualification testing of prototype and protoflight coupling hardware. This program was performed by Ball Aerospace Systems Division, Boulder, Colorado until its premature termination in May 1991. Development tests were performed on cryogenic face seals and flow control devices at superfluid helium (He II) conditions. Special equipment was developed to allow quantified leak detection at large leak rates up to 8.4 x 10(exp -4) SCCS. Two major fixtures were developed and characterized: The Cryogenic Test Fixture (CTF) and the Thermal Mismatch Fixture (Glovebox). The CTF allows the coupling hardware to be filled with liquid nitrogen (LN2), liquid helium (LHe) or sub-cooled liquid helium when hardware flow control valves are either open or closed. Heat leak measurements, internal and external helium leakage measurements, cryogenic proof pressure tests and external load applications are performed in this fixture. Special reusable MLI closures were developed to provide repeatable installations in the CTF. The Thermal Mismatch Fixture allows all design configurations of coupling hardware to be engaged and disengaged while measuring applied forces and torques. Any two hardware components may be individually thermally preconditioned within the range of 117 deg K to 350 deg K prior to engage/disengage cycling. This verifies dimensional compatibility and operation when thermally mismatched. A clean, dry GN2 atmosphere is maintained in the fixture at all times. The first shipset of hardware was received, inspected and cycled at room temperature just prior to program termination.

  6. Simulation program for central helium liquefier

    SciTech Connect

    Kawamura, S.

    1984-02-20

    The computer program described here analyzes the performance of Fermilab Central Helium Liquefier (CHL) and predicts the values of the plant thermodynamic variables at all process points in the plant. To simulate CHL, this program is modified from the prototype program which was developed by Hitachi Ltd. a couple of years ago. This program takes care of only the steady state simulation and takes account of the change of the turbine efficiency, the pressure drops and the UA values of the heat exchangers. How to use the program is shown.

  7. Design and Use of a Large-Scale Liquid Helium Conversion System

    NASA Technical Reports Server (NTRS)

    Knudsen, P. N.

    1999-01-01

    A large-scale liquid helium (LHe) to high-pressure (HP) gas conversion system has been implemented at the John F. Kennedy Space Center (KSC). Helium is used by the Space Shuttle, Titan, Atlas, and Delta programs for prelaunch processing, during launch count-down, and for postlaunch securing. The first phase of modifications to the Compressor Converter Facility (CCF), operational in April 1998, allowed the facility to accept bulk liquid helium from tanker containers and to off-load the helium at super-critical pressures. The second phase of modifications, planned to be operational by January 2001, will implement a 227-cubic-meter (m(sup 3)) on-site liquid helium storage system. This paper describes the design and operation of the current system and discusses the design and implementation for the second phase system.

  8. Accurate Determination of the Volume of an Irregular Helium Balloon

    ERIC Educational Resources Information Center

    Blumenthal, Jack; Bradvica, Rafaela; Karl, Katherine

    2013-01-01

    In a recent paper, Zable described an experiment with a near-spherical balloon filled with impure helium. Measuring the temperature and the pressure inside and outside the balloon, the lift of the balloon, and the mass of the balloon materials, he described how to use the ideal gas laws and Archimedes' principal to compute the average molecular…

  9. Precision spectroscopy of Helium

    SciTech Connect

    Cancio, P.; Giusfredi, G.; Mazzotti, D.; De Natale, P.; De Mauro, C.; Krachmalnicoff, V.; Inguscio, M.

    2005-05-05

    Accurate Quantum-Electrodynamics (QED) tests of the simplest bound three body atomic system are performed by precise laser spectroscopic measurements in atomic Helium. In this paper, we present a review of measurements between triplet states at 1083 nm (23S-23P) and at 389 nm (23S-33P). In 4He, such data have been used to measure the fine structure of the triplet P levels and, then, to determine the fine structure constant when compared with equally accurate theoretical calculations. Moreover, the absolute frequencies of the optical transitions have been used for Lamb-shift determinations of the levels involved with unprecedented accuracy. Finally, determination of the He isotopes nuclear structure and, in particular, a measurement of the nuclear charge radius, are performed by using hyperfine structure and isotope-shift measurements.

  10. High Pressure Composite Overwrapped Pressure Vessel (COPV) Development Tests at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Ray, David M.; Greene, Nathanael J.; Revilock, Duane; Sneddon, Kirk; Anselmo, Estelle

    2008-01-01

    Development tests were conducted to evaluate the performance of 2 COPV designs at cryogenic temperatures. This allows for risk reductions for critical components for a Gaseous Helium (GHe) Pressurization Subsystem for an Advanced Propulsion System (APS) which is being proposed for NASA s Constellation project and future exploration missions. It is considered an advanced system since it uses Liquid Methane (LCH4) as the fuel and Liquid Oxygen (LO2) as the oxidizer for the propellant combination mixture. To avoid heating of the propellants to prevent boil-off, the GHe will be stored at subcooled temperatures equivalent to the LO2 temperature. Another advantage of storing GHe at cryogenic temperatures is that more mass of the pressurized GHe can be charged in to a vessel with a smaller volume, hence a smaller COPV, and this creates a significant weight savings versus gases at ambient temperatures. The major challenge of this test plan is to verify that a COPV can safely be used for spacecraft applications to store GHe at a Maximum Operating Pressure (MOP) of 4,500 psig at 140R to 160R (-320 F to -300 F). The COPVs for these tests were provided by ARDE , Inc. who developed a resin system to use at cryogenic conditions and has the capabilities to perform high pressure testing with LN2.

  11. Nuclear criticality safety aspects of gaseous uranium hexafluoride (UF{sub 6}) in the diffusion cascade

    SciTech Connect

    Huffer, J.E.

    1997-04-01

    This paper determines the nuclear safety of gaseous UF{sub 6} in the current Gaseous Diffusion Cascade and auxiliary systems. The actual plant safety system settings for pressure trip points are used to determine the maximum amount of HF moderation in the process gas, as well as the corresponding atomic number densities. These inputs are used in KENO V.a criticality safety models which are sized to the actual plant equipment. The ENO V.a calculation results confirm nuclear safety of gaseous UF{sub 6} in plant operations..

  12. Emergency relief venting of the infrared telescope liquid helium dewar

    NASA Technical Reports Server (NTRS)

    Urban, E. W.

    1980-01-01

    An analysis is made of the emergency relief venting of the liquid helium dewar of the Spacelab 2 infrared telescope experiment in the event of a massive failure of the dewar guard vacuum. Such a failure, resulting from a major accident, could cause rapid heating and pressurization of the liquid helium in the dewar and lead to relief venting through the emergency relief system. The heat input from an accident is estimated for various fluid conditions in the dewar and the relief process as it takes place through one or both of the emergency relief paths is considered. It is shown that under all reasonable circumstances the dewar will safely relieve itself, and the pressure will not exceed 85 percent of the proof pressure or 63 percent of the burst pressure.

  13. Resource Letter SH-1: Superfluid Helium.

    ERIC Educational Resources Information Center

    Hallock, Robert B.

    1982-01-01

    Provides an annotated list of books, textbooks, and films on superfluid helium. Also lists research reports/reviews arranged by category, including among others, early history, microscopic understanding, ions in helium, helium in rotation, vortices and quantization, helium films and constricted geometrics, persistence flow, and superfluid helium…

  14. Apparatus to measure liquid helium boil-off from low-loss superconducting current leads

    SciTech Connect

    Cha, Y.S.; Niemann, R.C.; Hull, J.R.

    1995-06-01

    A low-loss liquid helium dewar was constructed to measure the liquid helium boil-off rate from high-temperature superconducting current leads. The dewar has a measured background heat leakage rate of 12 mW. Equations calculating the heat leakage rate from the measured vapor mass flow rate in liquid helium boil-off experiments are derived. Parameters that affect the experiments, such as density ratio, absolute pressure, and rate of pressure variation, are discussed. This study is important as superconducting current leads may be used in superconducting magnetic energy storage systems.

  15. MLTAP. Modular Helium Reactor Plant Transient Thermal-Hydraulic Analysis

    SciTech Connect

    Chan, T.W.; Openshaw, F.L.

    1992-11-06

    MLTAP is an integrated system transient analysis code for modular helium reactor (MHR) plants with superheated steam for Rankine power cycle and/or process heat applications. It is used for normal operational transient analyses as well as design basis/accident condition analyses with forced convection reactor cooling. MLTAP calculates the time-dependent temperatures, pressures, and flow rates for helium primary coolant and steam/water secondary coolant; reactor system and steam system structural temperatures; reactor neutronic behavior; pump, compressor, and steam turbine performance; reactivity control and other plant control systems responses; reactor and plant protection systems responses.

  16. Methods of Helium Injection and Removal for Heat Transfer Augmentation

    NASA Technical Reports Server (NTRS)

    Haight, Harlan; Kegley, Jeff; Bourdreaux, Meghan

    2008-01-01

    While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives usually involve simulation of an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Cryogenic Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

  17. Methods of Helium Injection and Removal for Heat Transfer Augmentation

    NASA Technical Reports Server (NTRS)

    Kegley, Jeffrey

    2008-01-01

    While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives are to simulate an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Calibration Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

  18. Hydrogen-Helium shock Radiation tests for Saturn Entry Probes

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.

    2016-01-01

    This paper describes the measurement of shock layer radiation in Hydrogen/Helium mixtures representative of that encountered by probes entering the Saturn atmosphere. Normal shock waves are measured in Hydrogen-Helium mixtures (89:11% by volume) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 km/s. Radiance is quantified from the Vacuum Ultraviolet through Near Infrared. An induction time of several centimeters is observed where electron density and radiance remain well below equilibrium. Radiance is observed in front of the shock layer, the characteristics of which match the expected diffusion length of Hydrogen.

  19. Accurate Determination of the Volume of an Irregular Helium Balloon

    NASA Astrophysics Data System (ADS)

    Blumenthal, Jack; Bradvica, Rafaela; Karl, Katherine

    2013-02-01

    In a recent paper, Zable described an experiment with a near-spherical balloon filled with impure helium. Measuring the temperature and the pressure inside and outside the balloon, the lift of the balloon, and the mass of the balloon materials, he described how to use the ideal gas laws and Archimedes' principal to compute the average molecular mass and density of the impure helium. This experiment required that the volume of the near-spherical balloon be determined by some approach, such as measuring the girth. The accuracy of the experiment was largely determined by the balloon volume, which had a reported uncertainty of about 4%.

  20. An appraisal of techniques for administration of gaseous nitric oxide.

    PubMed

    Tibballs, J; Hochmann, M; Carter, B; Osborne, A

    1993-12-01

    Gaseous nitric oxide (NO) is a potent selective pulmonary vasodilator. When mixed with O2 for more than 10-15 minutes it forms toxic amounts of nitrogen dioxide (NO2). We describe two techniques to administer 20 parts per million (ppm) during mechanical ventilation. A technique using flows of NO and O2 at low pressure to drive a Siemens Servo 900C ventilator provided a constant inspired concentration of NO. Another technique in which NO was added to the inspiratory limb of a Siemens Servo 900C ventilator driven by high pressure oxygen provided a highly variable concentration (9-53 ppm) of inspired NO.

  1. Hydrogen and Gaseous Fuel Safety and Toxicity

    SciTech Connect

    Lee C. Cadwallader; J. Sephen Herring

    2007-06-01

    Non-traditional motor fuels are receiving increased attention and use. This paper examines the safety of three alternative gaseous fuels plus gasoline and the advantages and disadvantages of each. The gaseous fuels are hydrogen, methane (natural gas), and propane. Qualitatively, the overall risks of the four fuels should be close. Gasoline is the most toxic. For small leaks, hydrogen has the highest ignition probability and the gaseous fuels have the highest risk of a burning jet or cloud.

  2. Helium process cycle

    DOEpatents

    Ganni, Venkatarao

    2008-08-12

    A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

  3. Helium process cycle

    DOEpatents

    Ganni, Venkatarao

    2007-10-09

    A unique process cycle and apparatus design separates the consumer (cryogenic) load return flow from most of the recycle return flow of a refrigerator and/or liquefier process cycle. The refrigerator and/or liquefier process recycle return flow is recompressed by a multi-stage compressor set and the consumer load return flow is recompressed by an independent consumer load compressor set that maintains a desirable constant suction pressure using a consumer load bypass control valve and the consumer load return pressure control valve that controls the consumer load compressor's suction pressure. The discharge pressure of this consumer load compressor is thereby allowed to float at the intermediate pressure in between the first and second stage recycle compressor sets. Utilizing the unique gas management valve regulation, the unique process cycle and apparatus design in which the consumer load return flow is separate from the recycle return flow, the pressure ratios of each recycle compressor stage and all main pressures associated with the recycle return flow are allowed to vary naturally, thus providing a naturally regulated and balanced floating pressure process cycle that maintains optimal efficiency at design and off-design process cycle capacity and conditions automatically.

  4. Corrosion of metallic materials in HTR-helium environments

    NASA Astrophysics Data System (ADS)

    Graham, L. W.

    1990-04-01

    The HTR core system has been successfully developed to provide helium coolant temperatures up to 1200 K giving the potential to exploit a wide variety of commercial applications. The present paper summarises the main corrosion effects found in HTR-helium environments, especially those which could change the mechanical properties of component materials. It is shown that corrosion phenomena derive from the presence of low concentrations of the impurities H 2O, CO, CH 4 and H 2 in the helium which can produce oxidation, decarburisation and carburisation depending on the relative and absolute partial pressures of the impurities and the temperature. Major corrosion effects can be avoided by control of the environment but the large heat to heat variations in behaviour found in materials exposed to nominally protective regimes at the higher temperatures of application requires further study.

  5. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Office's Authorized List of Federal Helium Suppliers available via the Internet at http://www.nm.blm.gov..., insert the following clause: Required Sources for Helium and Helium Usage Data (APR 2002) (a)...

  6. Electron impact ionization and multiphoton ionization of doped superfluid helium droplets: A comparison.

    PubMed

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-02-28

    We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped superfluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI directly ionizes helium atoms in a droplet therefore has higher yields for bigger droplets (within a limited size range), MPI is insensitive to the helium in a droplet and is only dependent on the number of dopant molecules. The optimal timing of the ionization pulse also varies with the doping pressure, implying a velocity slip among different sized droplets. Calculations of the doping statistics and ionization probabilities qualitatively agree with the experimental data. Our results offer a word of caution in interpreting the pressure and timing dependence of superfluid helium droplets, and we also devise a scheme in achieving a high degree of doping while limiting the contribution of dopant clusters.

  7. Electron impact ionization and multiphoton ionization of doped superfluid helium droplets: A comparison

    PubMed Central

    2016-01-01

    We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped superfluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI directly ionizes helium atoms in a droplet therefore has higher yields for bigger droplets (within a limited size range), MPI is insensitive to the helium in a droplet and is only dependent on the number of dopant molecules. The optimal timing of the ionization pulse also varies with the doping pressure, implying a velocity slip among different sized droplets. Calculations of the doping statistics and ionization probabilities qualitatively agree with the experimental data. Our results offer a word of caution in interpreting the pressure and timing dependence of superfluid helium droplets, and we also devise a scheme in achieving a high degree of doping while limiting the contribution of dopant clusters. PMID:26931697

  8. Stabilization of Multi-electron Bubbles in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac F.; Fang, Jieping; Tempere, Jacques

    2014-12-01

    Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes and the difficulty to localize them. We report the observation of long- lived MEBs in a novel cell filled with superfluid helium at static negative pressures. MEBs were extracted from the electron filled vapor sheath of a heated filament loop embedded in the superfluid helium and observed by high-speed photography. MEBs are 2D electron gases on the 3D surface of hollow helium bubbles. Diameters can range from nanometers to millimeters, depending on the number of enclosed electrons. Electrons move in angular momentum states; deformations of the surface are called spherical ripplons. The attractive electron-ripplon interaction leads to an unusual form of superconductivity. If they can be compressed, Wigner crystallization and quantum melting can be observed, as well as a new phase for localization called the ripplo- polaron lattice. MEBs are unstable to tunneling discharge when pressed against a surface. Just as Bose gases are captured in a trap for study, MEBs must also be localized away from walls. We shall discuss methods of capturing them in an electromagnetic trap embedded in the liquid helium.

  9. Gaseous sodium sulfate formation in flames and flowing gas environments

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Miller, R. A.; Kohl, F. J.; Fryburg, G. C.

    1977-01-01

    Formation of Na2SO4(g) in flames and hot flowing gas systems was studied by high pressure, free-jet expansion, modulated molecular beam mass spectrometric sampling. Fuel-lean CH4-O2 flames doped with SO2, H2O and NaCl yielded the gaseous Na2SO4 molecule in residence times of less than one millisecond. Intermediate species NaSO2(g) and NaSO3(g) were also observed and measured. Composition profiles were obtained for all reaction products. Nonflame flowing gas experiments showed that Na2SO4 and NaSO3 gaseous molecules were formed at 1140 C in mixtures of O2, H2O(g), SO2 and NaCl(g). Experimental results are compared with calculated equilibrium thermodynamic predictions.

  10. Applicability of Henry's Law to helium solubility in olivine

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.

    2013-12-01

    Applicability of Henry's Law to helium solubility in olivine We have experimentally determined helium solubility in San Carlos olivine across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in olivine correlates linearly with PHe between 55 and 1680 bar. This linear relationship suggests Henry's Law is applicable to helium dissolution into olivine up to 1680 bar PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into olivine. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(×3.1)×10-12 mol g-1 bar-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2(× 2.3)×10-12 mol g-1 bar-1. Combining the presently determined helium Henry's coefficient for olivine with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within olivine that are not saturated by 1680 bar PHe or ~5×10-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos olivine to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 bar-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into olivine using an externally heated

  11. Observation of a helium ion energy threshold for retention in tungsten exposed to hydrogen/helium mixture plasma

    NASA Astrophysics Data System (ADS)

    Thompson, M.; Deslandes, A.; Morgan, T. W.; Elliman, R. G.; De Temmerman, G.; Kluth, P.; Riley, D.; Corr, C. S.

    2016-10-01

    Helium retention is measured in tungsten samples exposed to mixed H/He plasma in the Magnum-PSI linear plasma device. It is observed that there is very little He retention below helium ion impact energies of 9.0+/- 1.4 eV, indicating the existence of a potential barrier which must be overcome for implantation to occur. The helium retention in samples exposed to plasma at temperatures  >1000 K is strongly correlated with nano-bubble formation measured using grazing incidence small-angle x-ray scattering. The diameters of nano-bubbles were not found to increase with increasing helium concentration, indicating that additional helium must be accommodated by increasing the bubble concentration or an increase in bubble pressure. For some samples pre-irradiation with heavy ions of 2.0 MeV energy is investigated to simulate the effects of neutron damage. It is observed that nano-bubble sizes are comparable between samples pre-irradiated with heavy-ions, and those without heavy-ion pre-irradiation.

  12. Gaseous Absorption and Dispersion of Sound in a Resonant Cylindrical Cavity: AN Acoustic and Photoacoustic Study

    NASA Astrophysics Data System (ADS)

    Beckwith, Clyfe Gordon

    This research investigated the feasibility of accurately measuring Virial coefficients in an acoustically resonant cylindrical cavity. Gases studied were: Argon, Helium, Nitrogen, Carbon Dioxide, and Methane. Parameters considered were: resonant frequencies (f_ {rm r}- also a measure of speed of sound), quality factors (Q), and signal amplitudes. We studied the longitudinal modes smaller than 2000 Hz, at room temperature and at pressures of 200, 500, and 800 mm of Hg. The choice of the longitudinal modes was predetermined by our wish to compare acoustic and photoacoustic resonance techniques of the same mode. The acoustic excitation is limited to the longitudinal modes and is achieved by placing a loudspeaker close to one end of the cavity. Photoacoustically we excite a small concentration of molecular Iodine, mixed in with the buffer gases, by a periodically interrupted Xenon light beam. By increasing the length of the cavity we could decrease the space between the modes of frequency. Our observations focused on the behaviors that (a) f_{rm r} shifted with pressure, (b) the f_{rm r} deviated from the simple laws of harmonics, and (c) the amplitudes for the two techniques varied differently with frequency. Effect (a) is due to the fact that the gases are not "ideal", and due to the presence of boundary layers caused by thermal conduction and viscosity gradients. Effect (b) arises because of the f_{rm r}'s mode dependence, caused by the wave scattering due to imperfect geometrical symmetries. Effect (c) is governed by the coupling factors. All measurements could theoretically be justified to within instrumental error, the only noted discrepancy is the lack of a theoretical mode dependence. We conclude that it is feasible to study the accuracy of Virial coefficients of simple gases provided that the boundary layer loss effects and the mode dependent wave scattering can be quantified; in regions of high pressures and high frequencies the Virial effects dominate the

  13. Radiation damage in gallium-stabilized δ-plutonium with helium bubbles

    NASA Astrophysics Data System (ADS)

    Wu, FengChao; Wang, Pei; Liu, XiaoYi; Wu, HengAn

    2017-02-01

    To understand the role of helium on self-irradiation effects in δ-plutonium, microstructure evolutions due to α-decay events near pre-existing helium bubbles in gallium-stabilized δ-plutonium are investigated using molecular dynamics simulations. Bubble promoting effect plays a dominating role in point defects production, resulting in increasing number of point defects. When lightweight helium atoms act as media, energy transfer discrepancy and altered spatial morphology of point defects induced by mass effect are revealed. The evolution of stacking faults surrounding the disordered core is studied and their binding effect on the propagation of point defects are presented. The cascade-induced bubble coalescence, resolution and re-nucleation driven by internal pressure are obtained in the investigation on helium behaviors. The intrinsic tendency in our simulated self-irradiation with helium bubbles is significant for understanding the underlying mechanism of aging in plutonium and its alloys.

  14. Atomically resolved phase transition of fullerene cations solvated in helium droplets

    NASA Astrophysics Data System (ADS)

    Kuhn, M.; Renzler, M.; Postler, J.; Ralser, S.; Spieler, S.; Simpson, M.; Linnartz, H.; Tielens, A. G. G. M.; Cami, J.; Mauracher, A.; Wang, Y.; Alcamí, M.; Martín, F.; Beyer, M. K.; Wester, R.; Lindinger, A.; Scheier, P.

    2016-11-01

    Helium has a unique phase diagram and below 25 bar it does not form a solid even at the lowest temperatures. Electrostriction leads to the formation of a solid layer of helium around charged impurities at much lower pressures in liquid and superfluid helium. These so-called `Atkins snowballs' have been investigated for several simple ions. Here we form HenC60+ complexes with n exceeding 100 via electron ionization of helium nanodroplets doped with C60. Photofragmentation of these complexes is measured by merging a tunable narrow-bandwidth laser beam with the ions. A switch from red- to blueshift of the absorption frequency of HenC60+ on addition of He atoms at n=32 is associated with a phase transition in the attached helium layer from solid to partly liquid (melting of the Atkins snowball). Elaborate molecular dynamics simulations using a realistic force field and including quantum effects support this interpretation.

  15. Atomically resolved phase transition of fullerene cations solvated in helium droplets

    PubMed Central

    Kuhn, M.; Renzler, M.; Postler, J.; Ralser, S.; Spieler, S.; Simpson, M.; Linnartz, H; Tielens, A. G. G. M.; Cami, J.; Mauracher, A.; Wang, Y.; Alcamí, M.; Martín, F.; Beyer, M. K.; Wester, R.; Lindinger, A.; Scheier, P.

    2016-01-01

    Helium has a unique phase diagram and below 25 bar it does not form a solid even at the lowest temperatures. Electrostriction leads to the formation of a solid layer of helium around charged impurities at much lower pressures in liquid and superfluid helium. These so-called ‘Atkins snowballs' have been investigated for several simple ions. Here we form HenC60+ complexes with n exceeding 100 via electron ionization of helium nanodroplets doped with C60. Photofragmentation of these complexes is measured by merging a tunable narrow-bandwidth laser beam with the ions. A switch from red- to blueshift of the absorption frequency of HenC60+ on addition of He atoms at n=32 is associated with a phase transition in the attached helium layer from solid to partly liquid (melting of the Atkins snowball). Elaborate molecular dynamics simulations using a realistic force field and including quantum effects support this interpretation. PMID:27874002

  16. Helium-Based Soundwave Chiller: Trillium: A Helium-Based Sonic Chiller- Tons of Freezing with 0 GWP Refrigerants

    SciTech Connect

    2010-09-01

    BEETIT Project: Penn State is designing a freezer that substitutes the use of sound waves and environmentally benign refrigerant for synthetic refrigerants found in conventional freezers. Called a thermoacoustic chiller, the technology is based on the fact that the pressure oscillations in a sound wave result in temperature changes. Areas of higher pressure raise temperatures and areas of low pressure decrease temperatures. By carefully arranging a series of heat exchangers in a sound field, the chiller is able to isolate the hot and cold regions of the sound waves. Penn State’s chiller uses helium gas to replace synthetic refrigerants. Because helium does not burn, explode or combine with other chemicals, it is an environmentally-friendly alternative to other polluting refrigerants. Penn State is working to apply this technology on a large scale.

  17. Electronic structure and enthalpy of hydrogen and helium mixtures

    NASA Astrophysics Data System (ADS)

    Ross, M.; Klepeis, J. E.; Schafer, K. J.; Barbee, T. W., III

    1992-11-01

    The first local density approximation (LDA) calculations of the electronic structure, equation of state, and enthalpy of mixing were carried out for a number of different compositions of hydrogen and helium in bcc and fcc lattices. These are fully quantum mechanical, self-consistent calculations utilizing state-of-the-art methods of electron band theory, which make no assumptions regarding pressure ionization. The major approximation in the LDA method is that the exchange and correlation energy is given by a free electron functional in terms of the local electron density. The majority of previous mixture calculations start with the assumption that both hydrogen and helium are pressure-ionized so that the electronic structure is approximately that of free or weakly screened electrons in the presence of positive ions. Stevenson used a hard-sphere mixture model for the ions with an ion-ion pseudopotential to account for electron screening and predicted that a mixture containing 7% helium by number, the composition believed to be present in Jupiter and Saturn, would phase separate at a temperature of about 7000 K at 8 Mbar. Subsequent calculations carried out for the fully ionized mixture and for a mixture of screened ions (linear response theory) have all arrived at predictions similar to those of Stevenson. MacFarlane and Hubbard performed Thomas-Fermi-Dirac calculations for mixing enthalpies of hydrogen and helium in bcc and fcc lattices and predicted that phase separation would not occur at any temperature.

  18. Theoretical model of the helium zone plate microscope

    NASA Astrophysics Data System (ADS)

    Salvador Palau, Adrià; Bracco, Gianangelo; Holst, Bodil

    2017-01-01

    Neutral helium microscopy is a new technique currently under development. Its advantages are the low energy, charge neutrality, and inertness of the helium atoms, a potential large depth of field, and the fact that at thermal energies the helium atoms do not penetrate into any solid material. This opens the possibility, among others, for the creation of an instrument that can measure surface topology on the nanoscale, even on surfaces with high aspect ratios. One of the most promising designs for helium microscopy is the zone plate microscope. It consists of a supersonic expansion helium beam collimated by an aperture (skimmer) focused by a Fresnel zone plate onto a sample. The resolution is determined by the focal spot size, which depends on the size of the skimmer, the optics of the system, and the velocity spread of the beam through the chromatic aberrations of the zone plate. An important factor for the optics of the zone plate is the width of the outermost zone, corresponding to the smallest opening in the zone plate. The width of the outermost zone is fabrication limited to around 10 nm with present-day state-of-the-art technology. Due to the high ionization potential of neutral helium atoms, it is difficult to build efficient helium detectors. Therefore, it is crucial to optimize the microscope design to maximize the intensity for a given resolution and width of the outermost zone. Here we present an optimization model for the helium zone plate microscope. Assuming constant resolution and width of the outermost zone, we are able to reduce the problem to a two-variable problem (zone plate radius and object distance) and we show that for a given beam temperature and pressure, there is always a single intensity maximum. We compare our model with the highest-resolution zone plate focusing images published and show that the intensity can be increased seven times. Reducing the width of the outermost zone to 10 nm leads to an increase in intensity of more than 8000

  19. The Hydrodynamic Stability of Gaseous Cosmic Filaments

    NASA Astrophysics Data System (ADS)

    Birnboim, Yuval; Padnos, Dan; Zinger, Elad

    2016-11-01

    Virial shocks at the edges of cosmic-web structures are a clear prediction of standard structure formation theories. We derive a criterion for the stability of the post-shock gas and of the virial shock itself in spherical, filamentary, and planar infall geometries. When gas cooling is important, we find that shocks become unstable, and gas flows uninterrupted toward the center of the respective halo, filament, or sheet. For filaments, we impose this criterion on self-similar infall solutions. We find that instability is expected for filament masses between 1011 and 1013 {M}⊙ Mpc-1. Using a simplified toy model, we then show that these filaments will likely feed halos with 1010 M ⊙ ≲ M halo ≲ 1013 M ⊙ at redshift z = 3, as well as 1012 M ⊙ ≲ M halo ≲ 1015 M ⊙ at z = 0. The instability will affect the survivability of the filaments as they penetrate gaseous halos in a non-trivial way. Additionally, smaller halos accreting onto non-stable filaments will not be subject to ram pressure inside the filaments. The instreaming gas will continue toward the center and stop either once its angular momentum balances the gravitational attraction, or when its density becomes so high that it becomes self-shielded to radiation.

  20. Elements of radiative interactions in gaseous systems

    NASA Technical Reports Server (NTRS)

    Tiwari, Surendra N.

    1991-01-01

    Basic formulations, analyses, and numerical procedures are presented to study radiative interactions in gray as well as nongray gases under different physical and flow conditions. After preliminary fluid-dynamical considerations, essential governing equations for radiative transport are presented that are applicable under local and nonlocal thermodynamic equilibrium conditions. Auxiliary relations for relaxation times and spectral absorption model are also provided. For specific applications, several simple gaseous systems are analyzed. The first system considered consists of a gas bounded by two parallel plates having the same temperature. For this system, both vibrational nonequilibrium effects and radiation conduction interactions are studied. The second system consists of fully developed laminar flow and heat transfer in a parallel plate duct under the boundary condition of a uniform surface heat flux. For this system, effects of gray surface emittance are studied. With the single exception of a circular geometry, the third system is identical to the second system. Here, the influence of nongray walls is also studied, and a correlation between the parallel plates and circular tube results is presented. The particular gases selected are CO, CO2, H2O, CH4, N2O, NH3, OH, and NO. The temperature and pressure range considered are 300 to 2000 K, and 0.1 to 100 atmosphere, respectively. Illustrative results obtained for different cases are discussed and some specific conclusions are provided.

  1. Combustion characteristics of alternative gaseous fuels

    SciTech Connect

    Park, O.; Veloo, Peter S.; Liu, N.; Egolfopoulos, Fokion N.

    2011-01-01

    Fundamental flame properties of mixtures of air with hydrogen, carbon monoxide, and C{sub 1}–C{sub 4} saturated hydrocarbons were studied both experimentally and numerically. The fuel mixtures were chosen in order to simulate alternative gaseous fuels and to gain insight into potential kinetic couplings during the oxidation of fuel mixtures. The studies included the use of the counterflow configuration for the determination of laminar flame speeds, as well as extinction and ignition limits of premixed flames. The experiments were modeled using the USC Mech II kinetic model. It was determined that when hydrocarbons are added to hydrogen flames as additives, flame ignition, propagation, and extinction are affected in a counterintuitive manner. More specifically, it was found that by substituting methane by propane or n-butane in hydrogen flames, the reactivity of the mixture is reduced both under pre-ignition and vigorous burning conditions. This behavior stems from the fact that propane and n-butane produce higher amounts of methyl radicals that can readily recombine with atomic hydrogen and reduce thus the rate of the H + O{sub 2} → O + OH branching reaction. The kinetic model predicts closely the experimental data for flame propagation and extinction for various fuel mixtures and pressures, and for various amounts of carbon dioxide in the fuel blend. On the other hand, it underpredicts, in general, the ignition temperatures.

  2. COSMIC-RAY HELIUM HARDENING

    SciTech Connect

    Ohira, Yutaka; Ioka, Kunihito

    2011-03-01

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10{sup 15}eV, and (2) all CR spectra become hard at {approx}>10{sup 11}eV nucleon{sup -1}. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at {approx}100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with {approx}10{sup 6} K. Our model predicts hard and concave spectra for heavier CR elements.

  3. Process for exchanging hydrogen isotopes between gaseous hydrogen and water

    SciTech Connect

    Hindin, Saul G.; Roberts, George W.

    1980-08-12

    A process for exchanging isotopes of hydrogen, particularly tritium, between gaseous hydrogen and water is provided whereby gaseous hydrogen depeleted in tritium and liquid or gaseous water containing tritium are reacted in the presence of a metallic catalyst.

  4. Predicting helium and neon adsorption and separation on carbon nanotubes by Monte Carlo simulation.

    PubMed

    Bolboli Nojini, Zabiollah; Abbas Rafati, Amir; Majid Hashemianzadeh, Seyed; Samiee, Sepideh

    2011-04-01

    The adsorption of helium and neon mixtures on single-walled carbon nanotubes (SWCNTs) was investigated at various temperatures (subcritical and supercritical) and pressures using canonical Monte Carlo (CMC) simulation. Adsorption isotherms were obtained at different temperatures (4, 40, 77 and 130 K) and pressures ranging from 1 to 16 MPa. Separation factors and isosteric enthalpies of adsorption were also calculated. Moreover, the adsorption isotherms were obtained at constant specific temperatures (4 and 40 K) and pressures (0.2 and 1.0 MPa) as a function of the amount adsorbed. All of the adsorption isotherms for an equimolar mixture of helium and neon have a Langmuir shape, indicating that no capillary condensation occurs. Both the helium and the neon adsorption isotherms exhibit similar behavior, and slightly more of the helium and neon mixture is adsorbed on the inner surfaces of the SWCNTs than on their outer surfaces. More neon is adsorbed than helium within the specified pressure range. The data obtained show that the isosteric enthalpies for the adsorption of neon are higher than those for helium under the same conditions, which means that adsorption of neon preferentially occurs by (15, 15) SWCNTs. Furthermore, the isosteric enthalpies of adsorption of both gases decrease with increasing temperature.

  5. Defective germanene as a high-efficiency helium separation membrane: a first-principles study.

    PubMed

    Zhu, Lei; Chang, Xiao; He, Daliang; Xue, Qingzhong; Li, Xiaofang; Jin, Yakang; Zheng, Haixia; Ling, Cuicui

    2017-03-01

    Development of low energy cost membranes for separating helium from natural gas is highly desired. Using van der Waals-corrected first-principles density functional theory (DFT) calculations, we theoretically investigate the helium separation performance of divacancy-defective germanene. The 555 777 divacancy-defective germanene presents a 0.53 eV energy barrier for helium, which is slightly larger than the energy threshold value of gas molecule penetration of a membrane (0.5 eV). Thus, the 555 777 divacancy-defective germanene is difficult for helium to permeate, except under high temperature or pressure. However, the 585 divacancy-defective germanene presents a surmountable energy barrier (0.27 eV) for helium, and it shows extremely high helium selectivities relative to other studied gas molecules. Especially, the He/Ne selectivity can be as high as 1 × 10(4) at room temperature. Together with the acceptable permeance for helium, the 585 divacancy-defective germanene can be used for helium separation with remarkably good performance.

  6. Defective germanene as a high-efficiency helium separation membrane: a first-principles study

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Chang, Xiao; He, Daliang; Xue, Qingzhong; Li, Xiaofang; Jin, Yakang; Zheng, Haixia; Ling, Cuicui

    2017-03-01

    Development of low energy cost membranes for separating helium from natural gas is highly desired. Using van der Waals-corrected first-principles density functional theory (DFT) calculations, we theoretically investigate the helium separation performance of divacancy-defective germanene. The 555 777 divacancy-defective germanene presents a 0.53 eV energy barrier for helium, which is slightly larger than the energy threshold value of gas molecule penetration of a membrane (0.5 eV). Thus, the 555 777 divacancy-defective germanene is difficult for helium to permeate, except under high temperature or pressure. However, the 585 divacancy-defective germanene presents a surmountable energy barrier (0.27 eV) for helium, and it shows extremely high helium selectivities relative to other studied gas molecules. Especially, the He/Ne selectivity can be as high as 1 × 104 at room temperature. Together with the acceptable permeance for helium, the 585 divacancy-defective germanene can be used for helium separation with remarkably good performance.

  7. Diffuse Helium Emission as a Precursory Sign of Volcanic Unrest

    NASA Astrophysics Data System (ADS)

    Padron, E.; Perez, N.; Hernandez Perez, P. A.; Sumino, H.; Melian Rodriguez, G.; Barrancos, J.; Nolasco, D.; Padilla, G.; Dionis, S.; Rodriguez, F.; Hernandez, I.; Calvo, D.; Peraza, M.; Nagao, K.

    2012-12-01

    /d on November 6, several days before the occurrence of the submarine eruption. A significant decrease to 13 kg/d was estimated almost 10 days after the beginning of the eruption, followed by a sudden increase to 38 kg/d several days before the largest seismic event of the volcanic crisis (M = 4.6) occurred on November 11. High volcanic-gas pressure in a magma surrounded by a less deformed and fractured crust could be responsible for the high magmatic-helium emission rate and eventual submarine eruption during the first segment of activity, whereas the second segment causing extensive crustal deformation and fracturing resulted in a low gas pressure on the magma and relatively low magmatic-helium diffuse emission rates. The energy loss in the system from the release of volcanic gases might be responsible for the observed decrease in the seismic energy released and the absence of a second volcanic eruption. The system continued to degas for one month, producing a gradual decrease in the helium emission rate. Helium emission data shown in this report demonstrate that diffuse helium surveys is a powerful tool for volcano monitoring. The geochemical parameters presented here are extremely important for forecasting the onset of volcanic unrest and subsequent volcanic eruptions, mainly when magma migrates aseismically, i.e., silently, toward the surface.

  8. Fiber-Cavity Optomechanics with Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Flowers-Jacobs, Nathan E.; Kashkanova, Anna D.; Shkarin, Alexey B.; Hoch, Scott W.; Deutsch, Christian; Reichel, Jakob; Harris, Jack G. E.

    2014-03-01

    In a typical optomechanical device, the resonance frequency of a cavity is coupled to mechanical motion through the radiation pressure force. To date, experimental cavities have predominately coupled to a resonant mechanical mode of a solid structure, often a lithographically-defined beam or membrane. We will describe our progress towards realizing an optomechanical device in which an optical fiber-cavity couples to the acoustic modes of superfluid helium. In this system, the optical modes and the acoustic modes of the superfluid are co-located between the mirrored ends of two fiber optic cables. Changes in the density of the superfluid change the effective length of the cavity which results in a standard, linear optomechanical coupling between the 300 MHz acoustic resonances and the 200 THz optical resonances. This type of device is motivated by the self-aligning nature of the acoustic and optical modes (which eases the difficulties of operating at cryogenic temperatures) and by the low optical and mechanical losses of superfluid helium. Although we expect the mechanical quality factor to be limited by acoustic radiation into the glass fiber, we will describe a proposal to realize a dual-band Bragg mirror to confine the optical and acoustic modes more efficiently. Supported by NSF Grant #1106110, ARO Grant #W911NF-13-1-0104, and the DARPA/MTO ORCHID program through a grant from AFOSR.

  9. From Liquid Helium to Granular Materials

    NASA Astrophysics Data System (ADS)

    Behringer, Robert P.

    2016-11-01

    This article provides a brief history of work that I have either carried out with Horst Meyer, or that was connected in some way with experiences reaching back to the laboratory known as LTM for low temperature [physics] Meyer, at Duke University. It is not intended as a complete review of all relevant work, but rather to hit highlights. My work with Horst started with studies of critical phenomena in liquid helium. This system provided an extremely rich and diverse testing ground for then newly emerging theories of static and dynamic critical phenomena. A key aspect of the experimental work with Horst was high-precision measurements of temperature and pressure. The ability to measure thermal properties with exceptional precision was at the core of this work. It also provided a natural springboard for entirely different investigations of Rayleigh-Bénard convection, which had just been initiated by Guenter Ahlers. My postdoc with Guenter provided a whole new set of experiences involving convection, dynamical instabilities, and chaos, where again the special properties, measurement techniques, and creative approaches to research associated with liquid helium were critical. In fact, later, knowledge of these techniques allowed me to start a whole new research direction in granular materials, which is a primary focus of my current research.

  10. Gaseous environment-sensitive fluorescence of YAG:Ce3+ nanocrystals

    NASA Astrophysics Data System (ADS)

    Feofilov, S. P.; Arsentyev, D. V.; Kulinkin, A. B.; Gacoin, T.; Mialon, G.; Meltzer, R. S.; Dujardin, C.

    2010-03-01

    The influence of the surrounding gaseous media on optically excited fluorescence of YAG:Ce nanoparticles was studied. It was observed that the 5d→4f fluorescence of Ce3+ ions in YAG nanoparticles dramatically depends on the pressure of the gaseous media surrounding the powder samples. The observations suggest the possibility of probing the pressure at the single molecule level with nanoparticles. It is suggested that the observed effects result from gas-molecule-assisted electron transfer between the nanoparticles and from modification of the surface of the particles by adsorption of gas molecules.

  11. Rogue mantle helium and neon.

    PubMed

    Albarède, Francis

    2008-02-15

    The canonical model of helium isotope geochemistry describes the lower mantle as undegassed, but this view conflicts with evidence of recycled material in the source of ocean island basalts. Because mantle helium is efficiently extracted by magmatic activity, it cannot remain in fertile mantle rocks for long periods of time. Here, I suggest that helium with high 3He/4He ratios, as well as neon rich in the solar component, diffused early in Earth's history from low-melting-point primordial material into residual refractory "reservoir" rocks, such as dunites. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoir rocks being stretched and tapped to different extents during melting.

  12. Curious Fluid Flows: From Complex Fluid Breakup to Helium Wetting

    NASA Astrophysics Data System (ADS)

    Huisman, Fawn Mitsu

    This work encompasses three projects; pinch-off dynamics in non-Newtonian fluids; helium wetting on alkali metals; and the investigation of quartz tuning forks as cryogenic pressure transducers. Chapter 1 discusses the breakup of a non-Newtonian yield stress fluid bridge. We measured the minimum neck radius, hmin, as a function of time and fit it to a power law with exponent n 1. We then compare n1 to exponent n2, obtained from a rotational rheometer using a Herschel-Bulkley model. We confirm n1=n2 for the widest variety of non-Newtonian fluids to date. When these fluids are diluted with a Newtonian fluid n1 does not equal n2. No current models predict that behavior, identifying a new class of fluid breakup. Chapter 2 presents the first chemical potential-temperature phase diagram of helium on lithium, sodium and gold, using a novel pressure measurement system. The growth and superfluid transition of a helium film on these substrates is measured via an oscillator for isotherms (fixed temperature, varying amount of helium gas), and quenches (fixed amount of helium gas, varying temperature). The chemical potential-temperature plot is similar for gold, lithium and sodium despite the large difference in the substrate binding energies. No signs of a 2-D liquid-vapor transition were seen. Chapter 3 discusses the creation of a 32.768 kHz quartz tuning fork in situ pressure transducer. Tuning forks are used to measure pressure at room temperature, but no work addresses their potential as cryogenic pressure transducers. We mapped out the behavior of a tuning fork as a function of pressure at 298, 7.0, 2.5, 1.6, 1.0 and 0.7 K by measuring the quality factor. The fork is sensitive to pressures above 0.1 mTorr, limiting its use as a pressure gauge at 0.6 K and below. The experimental curves were compared to a theoretical Q(P, T) function that was refined using the 298 K data. At cryogenic temperatures the formula breaks down in the viscous region and becomes inaccurate. The

  13. Helium release during shale deformation: Experimental validation

    NASA Astrophysics Data System (ADS)

    Bauer, Stephen J.; Gardner, W. Payton; Heath, Jason E.

    2016-07-01

    This work describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

  14. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, R.S.; Todd, R.A.

    1985-04-09

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  15. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  16. ASRDI oxygen technology survey. Volume 8: Pressure measurement

    NASA Technical Reports Server (NTRS)

    Arvidson, J. M.; Brennan, J. A.

    1975-01-01

    Pressure transducers and their current uses with gaseous or liquid oxygen are reviewed. All transducer types such as strain gage, capacitance, potentiometric, piezoelectric, etc., are included. Topics covered include: cryogenic pressure measurement; material compatibility with gaseous and liquid oxygen; cleaning procedures; pressure tap connections; transducer types and descriptions; and calibration techniques.

  17. Design and development of a leak tight helium II valve with low thermal impact

    NASA Technical Reports Server (NTRS)

    Mills, G. L.

    1991-01-01

    The Lambda Point Experiment is a precision measurement of the specific heat of liquid helium near the lambda point phase transition, in the low gravity of the space shuttle. It requires a valve for the helium sample chamber that operates at helium II temperature, has minimal thermal disturbance to the rest of the instrument, and is leak tight to helium II. A valve meeting these and all of the other science and engineering requirements of the mission has been developed by Ball. Initially, both torque and pressure actuated valve concepts were considered; the final flight design is pressure actuated. The rational for this decision as well as the rest of the valve design are given. The paper also discusses the manufacturing and testing of the prototype and flight valves. Test data is presented and discussed.

  18. Compact bath cryostat filled with liquid helium inside an ordinary storage Dewar

    NASA Astrophysics Data System (ADS)

    Klimov, A. E.

    2001-09-01

    An economical bath cryostat for optical and galvano-magnetic measurements is described. The small overall diameter of the cryostat allows filling with liquid helium directly upon immersion into an ordinary storage Dewar vessel. As a result, it needs no more than 0.2 l of liquid helium for a single cycle of low-temperature measurements outside the storage Dewar lasting 1.5-4 h. Simplicity and low cost are other advantages of the cryostat. The basic ideas used in this device are the mobility of a helium can relative to the external body of the cryostat and the essential increase of the helium boiling point if pressure increases up to 0.5-1.5 atm over atmospheric pressure.

  19. Effect of two types of helium circulators on the performance of a subsonic nuclear powered airplane

    NASA Technical Reports Server (NTRS)

    Strack, W. C.

    1971-01-01

    Two types of helium circulators are analytically compared on the bases of their influence on airplane payload and on propulsion system variables. One type of circulator is driven by the turbofan engines with power takeoff shafting while the other, a turbocirculator, is powered by a turbine placed in the helium loop between the nuclear reactor and the helium-to-air heat exchangers inside the engines. Typical results show that the turbocirculator yields more payload for circulator efficiencies greater than 0.82. Optimum engine and heat exchanger temperatures and pressures are significantly lower in the turbocirculator case compared to the engine-driven circulator scheme.

  20. Calculation and measurement of helium generation and solid transmutations in Cu-Zn-Ni alloys

    SciTech Connect

    Greenwood, L.R.; Oliver, B.M.; Garner, F.A.; Muroga, T.

    1998-03-01

    A method was recently proposed by Garner and Greenwood that would allow the separation of the effects of solid and gaseous transmutation for Cu-Zn-Ni alloys. Pure copper produces zinc and nickel during neutron irradiation. {sup 63}Cu transmutes to {sup 64}Ni and {sup 64}Zn, in about a 2-to-1 ratio, and {sup 65}Cu transmutes to {sup 66}Zn. The {sup 64}Zn further transmutes to {sup 65}Zn which has been shown to have a high thermal neutron (n,{alpha}) cross-section. Since a three-step reaction sequence is required for natural copper, the amount of helium produced is much smaller than would be produced for the two-step, well-known {sup 58}Ni (n,{gamma}) {sup 59}Ni (n,{alpha}) reaction sequence. The addition of natural Zn and Ni to copper leads to greatly increased helium production in neutron spectra with a significant thermal component. Using a suitable Cu-Zn-Ni alloy matrix and comparative irradiation of thermal neutron-shielded and unshielded specimens, it should be possible to distinguish the separate influences of the solid and gaseous transmutants. Whereas helium generation rates have been previously measured for natural nickel and copper, they have not been measured for natural Zn or Cu-Ni-Zn alloys. The (N,{alpha}) cross section for {sup 65}Zn was inferred from helium measurements made with natural copper. By comparing helium production in Cu and Cu-Zn alloys, this cross section can be determined more accurately. In the current study, both the solid and helium transmutants were measured for Cu, Cu-5Ni, Cu-3.5Zn and Cu-5Ni-2Zn, irradiated in each of two positions in the HFIR JP-23 test. Highly accurate helium measurements were performed on these materials by isotope dilution mass spectrometry using a facility that was recently moved from Rockwell International to PNNL. It is shown that both the helium and solid transmutants for Cu-zn-Ni alloys can be calculated with reasonable certainty, allowing the development of a transmutation experiment as proposed by

  1. Incident shock-wave characteristics in air, argon, carbon dioxide, and helium in a shock tube with unheated helium driver

    NASA Technical Reports Server (NTRS)

    Miller, C. G., III; Jones, J. J.

    1975-01-01

    Incident shock-wave velocities were measured in the Langley 6-inch expansion tube, operated as a shock tube, with air, argon, carbon dioxide, and helium as test gases. Unheated helium was used as the driver gas and most data were obtained at pressures of approximately 34 and 54 MN/sq m. A range of pressure ratio across the diaphragm was obtained by varying the quiescent test-gas pressure, for a given driver pressure, from 0.0276 to 34.5 kN/sq m. Single- and double-diaphragm modes of operation were employed and diaphragms of various materials tested. Shock velocity was determined from microwave interferometer measurements, response of pressure transducers positioned along interferometer measurements, response of pressure transducers positioned along the driven section (time-of-arrival gages), and to a lesser extent, measured tube-wall pressure. Velocities obtained from these methods are compared and limitations of the methods discussed. The present results are compared with theory and the effects of diaphragm mode (single or double diaphragm), diaphragm material, heating of the driver gas upon pressurization of the driver section, diaphragm opening time, interface mixing, and two-dimensional (nonplanar) flow are discussed.

  2. Combination free electron and gaseous laser

    DOEpatents

    Brau, Charles A.; Rockwood, Stephen D.; Stein, William E.

    1980-01-01

    A multiple laser having one or more gaseous laser stages and one or more free electron stages. Each of the free electron laser stages is sequentially pumped by a microwave linear accelerator. Subsequently, the electron beam is directed through a gaseous laser, in the preferred embodiment, and in an alternative embodiment, through a microwave accelerator to lower the energy level of the electron beam to pump one or more gaseous lasers. The combination laser provides high pulse repetition frequencies, on the order of 1 kHz or greater, high power capability, high efficiency, and tunability in the synchronous production of multiple beams of coherent optical radiation.

  3. Gaseous phase coal surface modification

    SciTech Connect

    Okoh, J.M.; Pinion, J.; Thiensatit, S.

    1992-05-07

    In this report, we present an improved, feasible and potentially cost effective method of cleaning and beneficiating ultrafine coal. Increased mechanization of mining methods and the need towards depyritization, and demineralization have led to an increase in the quantity of coal fines generated in recent times. For example, the amount of {minus}100 mesh coal occurring in coal preparation plant feeds now typically varies from 5 to 25% of the total feed. Environmental constraints coupled with the greatly increased cost of coal have made it increasingly important to recover more of these fines. Our method chemically modifies the surface of such coals by a series of gaseous phase treatments employing Friedel-Crafts reactions. By using olefins (ethene, propene and butene) and hydrogen chloride catalyst at elevated temperature, the surface hydrophobicity of coal is enhanced. This increased hydrophobicity is manifest in surface phenomena which reflect conditions at the solid/liquid interphase (zeta potential) and those which reflect conditions at the solid/liquid/gas interphases (contact angle, wettability and floatability).

  4. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1977-01-01

    Calculations are presented for the thermodynamic functions and phase-separation boundaries of solid metallic hydrogen-helium alloys at temperatures between zero and 19,000 K and at pressures between 15 and 90 Mbar. Expressions for the band-structure energy of a randomly disordered alloy (including third order in the electron-ion interaction) are derived and evaluated. Short- and long-range orders are included by the quasi-chemical method, and lattice dynamics in the virtual-crystal harmonic approximation. It is concluded that at temperatures below 4000 K, there is essentially complete phase separation of hydrogen-helium alloys and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  5. Phase separation of metallic hydrogen-helium alloys

    NASA Technical Reports Server (NTRS)

    Straus, D. M.; Ashcroft, N. W.; Beck, H.

    1976-01-01

    Calculations are presented for the thermodynamic functions and phase separation boundaries of solid metallic hydrogen helium alloys at temperatures between 0 K and 19,000 K and at pressures between 15 and 90 megabars. Expressions for the band structure energy of a randomly disordered alloy (including third order in the electron ion interaction) are derived and evaluated. Short and long range order are included by the quasi-chemical method, and lattice dynamics in the virtual crystal harmonic approximation. We conclude that at temperatures below 4,000 K there is complete phase separation of hydrogen helium alloys, and that a miscibility gap remains at the highest temperatures and pressures considered. The relevance of these results to models of the deep interior of Jupiter is briefly discussed.

  6. Crystal structure and density of helium to 232 kbar

    NASA Technical Reports Server (NTRS)

    Mao, H. K.; Wu, Y.; Jephcoat, A. P.; Hemley, R. J.; Bell, P. M.; Bassett, W. A.

    1988-01-01

    The properties of helium and hydrogen at high pressure are topics of great interest to the understanding of planetary interiors. These materials constitute 95 percent of the entire solar system. A technique was presented for the measurement of X-ray diffraction from single-crystals of low-Z condenses gases in a diamond-anvil cell at high pressure. The first such single-crystal X-ray diffraction measurements on solid hydrogen to 26.5 GPa were presented. The application of this technique to the problem of the crystal structure, equation of state, and phase diagram of solid helium is reported. Crucial for X-ray diffraction studies of these materials is the use of a synchrotron radiation source which provides high brillance, narrow collimation of the incident and diffracted X-ray beams to reduce the background noise, and energy-dispersive diffraction techniques with polychromatic (white) radiation, which provides high detection efficiency.

  7. 21 CFR 184.1355 - Helium.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Helium. 184.1355 Section 184.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1355 Helium. (a) Helium (empirical formula He, CAS Reg. No. 7440-59-7) is...

  8. 21 CFR 582.1355 - Helium.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Helium. 582.1355 Section 582.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS... Helium. (a) Product. Helium. (b) Conditions of use. This substance is generally recognized as safe...

  9. 43 CFR 3100.1 - Helium.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 2 2014-10-01 2014-10-01 false Helium. 3100.1 Section 3100.1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE... Helium. The ownership of and the right to extract helium from all gas produced from lands leased...

  10. 43 CFR 3100.1 - Helium.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Helium. 3100.1 Section 3100.1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE... Helium. The ownership of and the right to extract helium from all gas produced from lands leased...

  11. 21 CFR 582.1355 - Helium.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Helium. 582.1355 Section 582.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS... Helium. (a) Product. Helium. (b) Conditions of use. This substance is generally recognized as safe...

  12. 21 CFR 184.1355 - Helium.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Helium. 184.1355 Section 184.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1355 Helium. (a) Helium (empirical formula He, CAS Reg. No. 7440-59-7) is...

  13. 21 CFR 184.1355 - Helium.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Helium. 184.1355 Section 184.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD....1355 Helium. (a) Helium (empirical formula He, CAS Reg. No. 7440-59-7) is a colorless,...

  14. 21 CFR 582.1355 - Helium.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Helium. 582.1355 Section 582.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS... Helium. (a) Product. Helium. (b) Conditions of use. This substance is generally recognized as safe...

  15. 43 CFR 3100.1 - Helium.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 2 2013-10-01 2013-10-01 false Helium. 3100.1 Section 3100.1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE... Helium. The ownership of and the right to extract helium from all gas produced from lands leased...

  16. Applying the helium ionization detector in chromatography

    NASA Technical Reports Server (NTRS)

    Gibson, E. K.; Andrawes, F. F.; Brazell, R. S.

    1981-01-01

    High noise levels and oversensitivity of helium detector make flame-ionization and thermal-conductivity detectors more suitable for chromotography. Deficiencies are eliminated by modifying helium device to operate in saturation rather than multiplication mode. Result is low background current, low noise, high stability, and high sensitivity. Detector analyzes halocarbons, hydrocarbons, hydrogen cyanide, ammonia, and inorganics without requiring expensive research-grade helium.

  17. 21 CFR 582.1355 - Helium.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Helium. 582.1355 Section 582.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS... Helium. (a) Product. Helium. (b) Conditions of use. This substance is generally recognized as safe...

  18. 21 CFR 184.1355 - Helium.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Helium. 184.1355 Section 184.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1355 Helium. (a) Helium (empirical formula He, CAS Reg. No. 7440-59-7) is...

  19. 43 CFR 3100.1 - Helium.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Helium. 3100.1 Section 3100.1 Public Lands: Interior Regulations Relating to Public Lands (Continued) BUREAU OF LAND MANAGEMENT, DEPARTMENT OF THE... Helium. The ownership of and the right to extract helium from all gas produced from lands leased...

  20. 21 CFR 582.1355 - Helium.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Helium. 582.1355 Section 582.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS... Helium. (a) Product. Helium. (b) Conditions of use. This substance is generally recognized as safe...

  1. 21 CFR 184.1355 - Helium.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Helium. 184.1355 Section 184.1355 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1355 Helium. (a) Helium (empirical formula He, CAS Reg. No. 7440-59-7) is...

  2. Simulation of the mantle and crustal Helium isotope signature in the Mediterranean Sea using a high resolution regional circulation model

    NASA Astrophysics Data System (ADS)

    Ayache, Mohamed; Dutay, Jean-claude; Jean-baptiste, Philippe

    2015-04-01

    Helium isotopes (3He, 4He) are useful tracers for investigating the deep ocean circulation and for evaluating ocean general circulation models, because helium is a stable and conservative nuclide that does not take part in any chemical or biological processes. Helium in the ocean originates from three different sources: namely, (i) gas dissolution in equilibrium with atmospheric helium, (ii) helium-3 addition by radioactive decay of tritium (called tritiugenic helium), and (iii) injection of helium-3 and helium-4 by the submarine volcanic activity which occurs mainly at plate boundaries, and also addition of helium-4 from the crust and sedimentary cover by α-decay of uranium and thorium contained in various minerals (called terrigenic helium). Here we present the first simulation of the helium isotope distribution in the whole Mediterranean Sea, using a high resolution model (NEMO-MED12). The simulation was produced by building a simple source function for helium produced by submarine volcanic degassing in the main active areas of the Mediterranean, and by crustal degassing at sea bottom, based on previous estimates of the total flux of helium into the oceans. In addition to providing constraints on the degassing flux, our work provides information on the variability of the thermohaline circulation and the ventilation of the deep waters to constrain the degree to which the NEMO-MED12 can reproduce correctly the main hydrographic features of the Mediterranean Sea circulation. This study is part of the work carried out to assess the robustness of the NEMO-MED12 model, which will be used to study the evolution of the climate and its effect on the biogeochemical cycles in the Mediterranean Sea, and to improve our ability to predict the future evolution of the Mediterranean Sea under the increasing anthropogenic pressure.

  3. Investigating Electrical Breakdown in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Bouman, Nathaniel; SNS nEDM Collaboration

    2016-09-01

    The SNS nEDM experiment at Oak Ridge National Laboratory aims to search for the electric dipole moment of the neutron (nEDM) at the 3x10-28 level. The experiment is currently in the critical component demonstration phase. The design of the experiment calls for an electric field of 75 kV/cm across the experimental cells between electrodes within a bath of liquid helium (LHe). However, the electric breakdown phenomenon in LHe is poorly understood. Experiments investigating the breakdown of LHe were carried out at Los Alamos National Laboratory using a small-scale high voltage (SSHV) test apparatus at temperatures from 1.7K to 4K. Effects of varying temperature, pressure, and electrode surface conditions on LHe breakdown were investigated. Results and their implications to the SNS nEDM experiment will be presented.

  4. Viscosity and thermal conductivity coefficients of gaseous and liquid oxygen

    NASA Technical Reports Server (NTRS)

    Hanley, H. J. M.; Mccarty, R. D.; Sengers, J. V.

    1974-01-01

    Equations and tables are presented for the viscosity and thermal conductivity coefficients of gaseous and liquid oxygen at temperatures between 80 K and 400 K for pressures up to 200 atm. and at temperatures between 80 K and 2000 K for the dilute gas. A description of the anomalous behavior of the thermal conductivity in the critical region is included. The tabulated coefficients are reliable to within about 15% except for a region in the immediate vicinity of the critical point. Some possibilities for future improvements of this reliability are discussed.

  5. Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

    1996-01-01

    A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

  6. Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

    1997-01-01

    A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

  7. Helium diffusion in the sun

    NASA Technical Reports Server (NTRS)

    Bahcall, J. N.; Pinsonneault, M. H.

    1992-01-01

    We calculate improved standard solar models using the new Livermore (OPAL) opacity tables, an accurate (exportable) nuclear energy generation routine which takes account of recent measurements and analyses, and the recent Anders-Grevesse determination of heavy element abundances. We also evaluate directly the effect of the diffusion of helium with respect to hydrogen on the calculated neutrino fluxes, on the primordial solar helium abundance, and on the depth of the convective zone. Helium diffusion increases the predicted event rates by about 0.8 SNU, or 11 percent of the total rate, in the chlorine solar neutrino experiment, by about 3.5 SNU, or 3 percent, in the gallium solar neutrino experiments, and by about 12 percent in the Kamiokande and SNO solar neutrino experiments. The best standard solar model including helium diffusion and the most accurate nuclear parameters, element abundances, and radiative opacity predicts a value of 8.0 SNU +/- 3.0 SNU for the C1-37 experiment and 132 +21/-17 SNU for the Ga - 71 experiment, where the uncertainties include 3 sigma errors for all measured input parameters.

  8. Competitive Deprotonation and Superoxide [O2 -•] Radical-Anion Adduct Formation Reactions of Carboxamides under Negative-Ion Atmospheric-Pressure Helium-Plasma Ionization (HePI) Conditions

    NASA Astrophysics Data System (ADS)

    Hassan, Isra; Pinto, Spencer; Weisbecker, Carl; Attygalle, Athula B.

    2016-03-01

    Carboxamides bearing an N-H functionality are known to undergo deprotonation under negative-ion-generating mass spectrometric conditions. Herein, we report that N-H bearing carboxamides with acidities lower than that of the hydroperoxyl radical (HO-O•) preferentially form superoxide radical-anion (O2 -•) adducts, rather than deprotonate, when they are exposed to the glow discharge of a helium-plasma ionization source. For example, the spectra of N-alkylacetamides show peaks for superoxide radical-anion (O2 -•) adducts. Conversely, more acidic amides, such as N-alkyltrifluoroacetamides, preferentially undergo deprotonation under similar experimental conditions. Upon collisional activation, the O2 -• adducts of N-alkylacetamides either lose the neutral amide or the hydroperoxyl radical (HO-O•) to generate the superoxide radical-anion ( m/z 32) or the deprotonated amide [ m/z (M - H)-], respectively. For somewhat acidic carboxamides, the association between the two entities is weak. Thus, upon mildest collisional activation, the adduct dissociates to eject the superoxide anion. Superoxide-adduct formation results are useful for structure determination purposes because carboxamides devoid of a N-H functionality undergo neither deprotonation nor adduct formation under HePI conditions.

  9. Leakage predictions for Rayleigh-step, helium-purge seals

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.

    1988-01-01

    Rayleigh-step, helium purge, annular shaft seals, studied for use in liquid oxygen turbopumps, generate a hydrodynamic force that enables the seal to follow shaft perturbations. Hence, smaller clearances can be used to reduce seal leakage. FLOWCAL, a computer code developed by Mechanical Technology Incorporated, predicts gas flow rate through an annular seal with an axial pressure gradient. Analysis of a 50-mm Rayleigh-step, helium-purge, annular seal showed the flow rate increased axial pressure gradient, downstream pressure, and eccentricity ratio. Increased inlet temperature reduced leakage. Predictions made at maximum and minimum clearances (due to centrifugal and thermal growths, machining tolerances and + or - 2 percent uncertainty in the clearance measurement) placed wide boundaries on expected flow rates. The widest boundaries were set by thermal growth conditions. Predicted flow rates for a 50-mm Rayleigh-step, helium-purge, annular seal underestimated measured flow rates by three to seven times. However, the analysis did accurately predict flow rates for choked gas flow through annular seals when compared to flow rates measured in two other independent studies.

  10. Tensile properties of ADI material in water and gaseous environments

    SciTech Connect

    Rajnovic, Dragan; Balos, Sebastian; Sidjanin, Leposava; Eric Cekic, Olivera; Grbovic Novakovic, Jasmina

    2015-03-15

    Austempered ductile iron (ADI) is an advanced type of heat treated ductile iron, having comparable mechanical properties as forged steels. However, it was found that in contact with water the mechanical properties of austempered ductile irons decrease, especially their ductility. Despite considerable scientific attention, the cause of this phenomenon remains unclear. Some authors suggested that hydrogen or small atom chemisorption causes the weakening of the surface atomic bonds. To get additional reliable data of that phenomenon, in this paper, two different types of austempered ductile irons were tensile tested in various environments, such as: argon, helium, hydrogen gas and water. It was found that only the hydrogen gas and water gave a statistically significant decrease in mechanical properties, i.e. cause embrittlement. Furthermore, the fracture surface analysis revealed that the morphology of the embrittled zone near the specimen surface shares similarities to the fatigue micro-containing striation-like lines, which indicates that the morphology of the brittle zone may be caused by cyclic local-chemisorption, micro-embrittlement and local-fracture. - Highlights: • In contact with water and other liquids the ADI suddenly exhibits embrittlement. • The embrittlement is more pronounced in water than in the gaseous hydrogen. • The hydrogen chemisorption into ADI surface causes the formation of a brittle zone. • The ADI austempered at lower temperatures (300 °C) is more resistant to embrittlement.

  11. Development of a Pressure Box to Evaluate Reusable-Launch-Vehicle Cryogenic-Tank Panels

    NASA Technical Reports Server (NTRS)

    Ambur, Damodar R.; Sikora, Joseph; Maguire, James F.; Winn, Peter M.

    1996-01-01

    A cryogenic pressure-box test machine has been designed and is being developed to test full-scale reusable launch vehicle cryogenic-tank panels. This machine is equipped with an internal pressurization system, a cryogenic cooling system, and a heating system to simulate the mechanical and thermal loading conditions that are representative of a reusable launch vehicle mission profile. The cryogenic cooling system uses liquid helium and liquid nitrogen to simulate liquid hydrogen and liquid oxygen tank internal temperatures. A quartz lamp heating system is used for heating the external surface of the test panels to simulate cryogenic-tank external surface temperatures during re-entry of the launch vehicle. The pressurization system uses gaseous helium and is designed to be controlled independently of the cooling system. The tensile loads in the axial direction of the test panel are simulated by means of hydraulic actuators and a load control system. The hoop loads in the test panel are reacted by load-calibrated turnbuckles attached to the skin and frame elements of the test panel. The load distribution in the skin and frames can be adjusted to correspond to the tank structure by using these turnbuckles. The seal between the test panel and the cryogenic pressure box is made from a reinforced Teflon material which can withstand pressures greater than 52 psig at cryogenic temperatures. Analytical results and tests on prototype test components indicate that most of the cryogenic-tank loading conditions that occur in flight can be simulated in the cryogenic pressure-box test machine.

  12. Development of a Pressure Box to Evaluate Reusable-Launch-Vehicle Cryogenic-Tank Panels

    NASA Technical Reports Server (NTRS)

    Ambur, Damodar R.; Sikora, Joseph; Maguire, James F.; Winn, Peter M.

    1996-01-01

    A cryogenic pressure-box test machine has been designed and is being developed to test full-scale reusable-launch-vehicle cryogenic-tank panels. This machine is equipped with an internal pressurization system, a cryogenic cooling system, and a heating system to simulate the mechanical and thermal loading conditions that are representative of a reusable-launch-vehicle mission profile. The cryogenic cooling system uses liquid helium and liquid nitrogen to simulate liquid hydrogen and liquid oxygen tank internal temperatures. A quartz lamp heating system is used for heating the external surface of the test panels to simulate cryogenic-tank external surface temperatures during re-entry of the launch vehicle. The pressurization system uses gaseous helium and is designed to be controlled independently of the cooling system. The tensile loads in the axial direction of the test panel are simulated by means of hydraulic actuators and a load control system. The hoop loads in the test panel are reacted by load-calibrated turnbuckles attached to the skin and frame elements of the test panel. The load distribution in the skin and frames can be adjusted to correspond to the tank structure by using these turnbuckles. The seal between the test panel and the cryogenic pressure box is made from a reinforced Teflon material which can withstand pressures greater than 52 psig at cryogenic temperatures. Analytical results and tests on prototype test components indicate that most of the cryogenic-tank loading conditions that occur in flight can be simulated in the cryogenic pressure-box test machine.

  13. Stratified charge combustion system and method for gaseous fuel internal combustion engines

    SciTech Connect

    Rhoades, W.A. Jr.

    1986-03-11

    This patent describes a stratified charge combustion system for use in a gaseous fuel internal combustion engine. This system consists of: (a) a combustion chamber; (b) an ignition; (c) a gaseous fuel injection valve assembly in communication with the combustion chamber and in spaced relationship from the ignition source with a portion of the inside surfaces extending between the fuel injection valve assembly and the ignition source. The fuel valve assembly defines an entry port for the entrance of gaseous fuel, the entry port is recessed outside of a fixed inside surface. (d) means for pressuring the gaseous fuel prior to injection; and (e) a curved transitional surface extending from the entry port toward the portion of the inside surfaces extending between the fuel injection valve assembly and the ignition source. The curved transitional surface curves away from the direction of the entry port. The curved transitional surface has a curvature for the particular direction and configuration of the entry port. The particular configuration of the portion of the inside surfaces extends between the injection valve assembly and the ignition source. The particular arrangment of the fuel injection valve assembly in the combustion chamber, and for the particular pressure of the gaseous fuel is to produce the Coanda Effect in the injected gaseous fuel flow after it passes through the entry port and follows the curved transitional surface under the Coanda Effect. As the curved transitional surface curves away from the direction of the entry port, a flow is produced of the gaseous fuel that clings to and follows the particular configuration of the inside surfaces to the ignition source.

  14. Approximating the Helium Wavefunction in Positronium-Helium Scattering

    NASA Technical Reports Server (NTRS)

    DiRienzi, Joseph; Drachman, Richard J.

    2003-01-01

    In the Kohn variational treatment of the positronium- hydrogen scattering problem the scattering wave function is approximated by an expansion in some appropriate basis set, but the target and projectile wave functions are known exactly. In the positronium-helium case, however, a difficulty immediately arises in that the wave function of the helium target atom is not known exactly, and there are several ways to deal with the associated eigenvalue in formulating the variational scattering equations to be solved. In this work we will use the Kohn variational principle in the static exchange approximation to d e t e e the zero-energy scattering length for the Ps-He system, using a suite of approximate target functions. The results we obtain will be compared with each other and with corresponding values found by other approximation techniques.

  15. Time-resolved vacuum-ultraviolet emission (λ  =  60-120 nm) from a high pressure DBD-excited helium plasma: formation mechanisms of the fast component

    NASA Astrophysics Data System (ADS)

    Carman, R. J.; Ganesan, R.; Kane, D. M.

    2016-03-01

    We report time and wavelength resolved studies of the vacuum-ultraviolet (VUV) emission from a windowless dielectric barrier discharge (DBD) in helium. Short-pulse voltage excitation is utilised to clearly resolve the fast and slow temporal components of the Hopfield continuum between λ  =  60-120 nm. Experimental results and theoretical modelling of the spectral distributions indicate that the two components of the VUV emission must originate from the same radiating molecular state—\\text{He}2\\ast≤ft({{\\text{A}}1}Σ\\text{u}+\\right) , and that two distinct pumping mechanisms populate this state. The time evolution of the fast component is found to correlate with that from the (0,0) molecular transition \\text{He}2\\ast≤ft({{\\text{E}}1}{{\\Pi}\\text{g}}-~{{\\text{A}}1}Σ\\text{u}+\\right) (λ  =  513.4 nm). Thus the \\text{He}2\\ast≤ft({{\\text{A}}1}{}Σ\\text{u}+\\right) state is initially rapidly pumped via radiative cascade from higher \\text{He}2\\ast(n=3) molecular states. In addition, the observed band emissions from the molecular \\text{He}2\\ast≤ft({{\\text{E}}1}{{\\Pi}\\text{g}}\\right) v=0 and \\text{He}2\\ast≤ft({{\\text{F}}1}Σ\\text{u}+\\right) v=0 states and the line emissions from the atomic He*(n  =  3) states all exhibit similar temporal behaviour during the discharge excitation period. Our results are consistent with the recent report of Frost et al (J. Phys. B 34 1569 2001) concerning the existence of a so-called ‘neglected channel’ to fast \\text{He}2\\ast production from He*(n  =  3) atomic state precursors.

  16. Lightweight Liquid Helium Dewar for High-Altitude Balloon Payloads

    NASA Technical Reports Server (NTRS)

    Kogut, Alan; James, Bryan; Fixsen, Dale

    2013-01-01

    Astrophysical observations at millimeter wavelengths require large (2-to-5- meter diameter) telescopes carried to altitudes above 35 km by scientific research balloons. The scientific performance is greatly enhanced if the telescope is cooled to temperatures below 10 K with no emissive windows between the telescope and the sky. Standard liquid helium bucket dewars can contain a suitable telescope for telescope diameter less than two meters. However, the mass of a dewar large enough to hold a 3-to-5-meter diameter telescope would exceed the balloon lift capacity. The solution is to separate the functions of cryogen storage and in-flight thermal isolation, utilizing the unique physical conditions at balloon altitudes. Conventional dewars are launched cold: the vacuum walls necessary for thermal isolation must also withstand the pressure gradient at sea level and are correspondingly thick and heavy. The pressure at 40 km is less than 0.3% of sea level: a dewar designed for use only at 40 km can use ultra thin walls to achieve significant reductions in mass. This innovation concerns new construction and operational techniques to produce a lightweight liquid helium bucket dewar. The dewar is intended for use on high-altitude balloon payloads. The mass is low enough to allow a large (3-to-5-meter) diameter dewar to fly at altitudes above 35 km on conventional scientific research balloons without exceeding the lift capability of the balloon. The lightweight dewar has thin (250- micron) stainless steel walls. The walls are too thin to support the pressure gradient at sea level: the dewar launches warm with the vacuum space vented continuously during ascent to eliminate any pressure gradient across the walls. A commercial 500-liter storage dewar maintains a reservoir of liquid helium within a minimal (hence low mass) volume. Once a 40-km altitude is reached, the valve venting the vacuum space of the bucket dewar is closed to seal the vacuum space. A vacuum pump then

  17. Exploding and Imaging of Electron Bubbles in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Yadav, Neha; Vadakkumbatt, Vaisakh; Maris, Humphrey J.; Ghosh, Ambarish

    2016-11-01

    An electron bubble in liquid helium-4 under the saturated vapor pressure becomes unstable and explodes if the pressure becomes more negative than -1.9 bars. In this paper, we use focused ultrasound to explode electron bubbles. We then image at 30,000 frames per second the growth and subsequent collapse of the bubbles. We find that bubbles can grow to as large as 1 mm in diameter within 2 ms after the cavitation event. We examine the relation between the maximum size of the bubble and the lifetime and find good agreement with the experimental results.

  18. Superfluid helium leak sealant study

    NASA Technical Reports Server (NTRS)

    Vorreiter, J. W.

    1981-01-01

    Twenty-one leak specimens were fabricated in the ends of stainless steel and aluminum tubes. Eighteen of these tubes were coated with a copolymer material to seal the leak. The other three specimens were left uncoated and served as control specimens. All 21 tubes were cold shocked in liquid helium 50 times and then the leak rate was measured while the tubes were submerged in superfluid helium at 1.7 K. During the cold shocks two of the coated specimens were mechanically damaged and eliminated from the test program. Of the remaining 16 coated specimens one suffered a total coating failure and resulting high leak rate. Another three of the coated specimens suffered partial coating failures. The leak rates of the uncoated specimens were also measured and reported. The significance of various leak rates is discussed in view of the infrared astronomical satellite (IRAS) Dewar performance.

  19. Effect of helium on structure and compression behavior of SiO2 glass

    PubMed Central

    Shen, Guoyin; Mei, Qiang; Prakapenka, Vitali B.; Lazor, Peter; Sinogeikin, Stanislav; Meng, Yue; Park, Changyong

    2011-01-01

    The behavior of volatiles is crucial for understanding the evolution of the Earth’s interior, hydrosphere, and atmosphere. Noble gases as neutral species can serve as probes and be used for examining gas solubility in silicate melts and structural responses to any gas inclusion. Here, we report experimental results that reveal a strong effect of helium on the intermediate range structural order of SiO2 glass and an unusually rigid behavior of the glass. The structure factor data show that the first sharp diffraction peak position of SiO2 glass in helium medium remains essentially the same under pressures up to 18.6 GPa, suggesting that helium may have entered in the voids in SiO2 glass under pressure. The dissolved helium makes the SiO2 glass much less compressible at high pressures. GeO2 glass and SiO2 glass with H2 as pressure medium do not display this effect. These observations suggest that the effect of helium on the structure and compression of SiO2 glass is unique. PMID:21444785

  20. Saturn's Helium Abundance from Cassini CIRS and RSS Data

    NASA Astrophysics Data System (ADS)

    Achterberg, Richard K.; Schinder, Paul J.; Flasar, F. Michael

    2016-10-01

    The ratio of helium to hydrogen in Saturn's atmosphere provides an important constraint on models of Saturn's formation and evolution, but has been poorly constrained by available data. Measurements combining Voyager infrared and radio data [1] gave a He/H2 mole ratio of 0.034 ± 0.024, far below the protosolar value and requiring either significant helium loss or sequestration in the interior. Prompted by discrepancies between the Voyager infrared/radio and Galileo probe measurements of helium on Jupiter, Conrath and Gautier [2] reevaluated the helium abundance on Saturn from Voyager infrared data only, obtaining a He/H2 mole ratio of 0.135 ± 0.025, inconsistent with the previous results. Because of this discrepancy, estimating Saturn's atmospheric helium abundance has been a major goal of the Cassini mission.We are estimating the He/H2 mole ratio in Saturn's atmosphere using a combination of data from the Cassini Radio Science Subsystem (RSS) and Composite InfraRed Spectrometer (CIRS). Radio occultations, in which a carrier signal is observed as Cassini passed behind Saturn as seen from antennas on Earth, give a vertical profile of atmospheric refractivity, which can be converted to temperature as a function of pressure assuming a mean molecular weight. The assumed molecular weight is adjusted until synthetic thermal infrared spectra match spectra observed by CIRS at the same latitude and time. Preliminary results from a set of eleven near-equatorial occultations taken in 2005 give He/H2 mole ratios varying between ~0.060 and 0.085.[1] Conrath, B. J., et al., 1984, Ap. J., 282:807-815[2] Conrath, B. J. and D. Gautier, 2000, Icarus, 144:124-134

  1. Detecting scintillations in liquid helium

    NASA Astrophysics Data System (ADS)

    Huffman, P. R.; McKinsey, D. N.

    2013-09-01

    We review our work in developing a tetraphenyl butadiene (TPB)-based detection system for a measurement of the neutron lifetime using magnetically confined ultracold neutrons (UCN). As part of the development of the detection system for this experiment, we studied the scintillation properties of liquid helium itself, characterized the fluorescent efficiencies of different fluors, and built and tested three detector geometries. We provide an overview of the results from these studies as well as references for additional information.

  2. Cryosorption of helium on argon frost TFTR (Tokamak Fusion Test Reactor) neutral beamlines

    SciTech Connect

    Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.; Garzotto, V.; Dudek, L.E.; Grisham, L.R.; Martin, G.D.; O'Connor, T.E.; Stevenson, T.N.; von Halle, A. . Plasma Physics Lab.)

    1989-11-01

    Helium pumping on argon frost has been investigated on TFTR neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are {approximately} 25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, > 20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a two-fold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 torr-l of helium, the beamline base pressure rose to 2{times}10{sup -5} torr from an initial value of 10{sup -8} torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 torr-l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity. 29 refs., 7 figs.

  3. The initiation and propagation of helium detonations in white dwarf envelopes

    SciTech Connect

    Shen, Ken J.; Moore, Kevin

    2014-12-10

    Detonations in helium-rich envelopes surrounding white dwarfs have garnered attention as triggers of faint thermonuclear '.Ia' supernovae and double detonation Type Ia supernovae. However, recent studies have found that the minimum size of a hotspot that can lead to a helium detonation is comparable to, or even larger than, the white dwarf's pressure scale height, casting doubt on the successful ignition of helium detonations in these systems. In this paper, we examine the previously neglected effects of C/O pollution and a full nuclear reaction network, and we consider hotspots with spatially constant pressure in addition to constant density hotspots. We find that the inclusion of these effects significantly decreases the minimum hotspot size for helium-rich detonation ignition, making detonations far more plausible during turbulent shell convection or during double white dwarf mergers. The increase in burning rate also decreases the minimum shell mass in which a helium detonation can successfully propagate and alters the composition of the shell's burning products. The ashes of these low-mass shells consist primarily of silicon, calcium, and unburned helium and metals and may explain the high-velocity spectral features observed in most Type Ia supernovae.

  4. Heat transfer resistances in the measurements of cold helium vapour temperature in a subatmospheric process line

    NASA Astrophysics Data System (ADS)

    Adamczyk, A.; Pietrowicz, S.; Fydrych, J.

    2017-02-01

    The superfluid helium technology, which is essentially used in particle accelerators, requires complex cryogenic systems that include long lines transferring cold helium vapours at a subathmospheric pressure below 50 mbar. Usually in large systems the subatmospheric pressure is generated by a set of warm and cold compressors. In consequence, the heat loads to the line and especially the helium temperature in the inlet to the cold compressors are crucial parameters. In order to measure the helium temperature the temperature sensors are usually fixed to the external surface of the process lines. However, this technique can lead to unwanted measurement errors and affect the temperature measurement dynamics mainly due to low thermal conductivity of the pipe wall material, large pipe diameters and low helium density. Assembling a temperature sensor in a well (cold finger) reaching the centerline of the flowing helium is a technique that can improve the measurement quality and dynamics (response time). The paper presents the numerical simulations of heat transfers occurring in the both measurement techniques and discusses the impacts of the heat transfer resistances on the temperature measurement dynamics.

  5. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction.

    PubMed

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-21

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  6. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction

    NASA Astrophysics Data System (ADS)

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-01

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  7. Surface modification of carbon nanohorns by helium plasma and ozone treatments

    NASA Astrophysics Data System (ADS)

    Lin, Zaw; Iijima, Toru; Selvam Karthik, Paneer; Yoshida, Mitsunobu; Hada, Masaki; Nishikawa, Takeshi; Hayashi, Yasuhiko

    2017-01-01

    In this paper, we describe the effects of helium plasma and ozone treatments on the dispersibility of carbon nanohorns (CNHs) in water. The experimental setups have been designed to efficiently generate helium plasma and ozone by dielectric barrier discharge at atmospheric pressure. After being treated with ozone, the oxygen-containing functional groups were introduced to the surface of CNHs, and are responsible for better dispersion. Helium plasma treatment was performed separately and it resulted in hydroxyl functional groups on the surface of CNHs. It was also found that the sizes of CNHs in water were smaller after ozone treatment. However, plasma-treated CNHs were bigger than ozone treated CNHs. The dispersed CNHs modified by ozone treatment were stable for more than three months without precipitation. In contrast, though helium plasma treatment introduced hydroxyl groups to the surface of CNHs, the dispersibility decreased and the flocculation of CNHs was observed in a few minutes.

  8. Real gas flow parameters for NASA Langley 22-inch Mach 20 helium tunnel

    NASA Technical Reports Server (NTRS)

    Hollis, Brian R.

    1992-01-01

    A computational procedure was developed which can be used to determine the flow properties in hypersonic helium wind tunnels in which real gas behavior is significant. In this procedure, a three-coefficient virial equation of state and the assumption of isentropic nozzle flow are employed to determine the tunnel reservoir, nozzle, throat, freestream, and post-normal shock conditions. This method was applied to a range of conditions which encompasses the operational capabilities of the LaRC 22-Inch Mach 20 Helium Tunnel. Results are presented graphically in the form of real gas correction factors which can be applied to perfect gas calculations. Important thermodynamic properties of helium are also plotted versus pressure and temperature. The computational scheme used to determine the real-helium flow parameters was incorporated into a FORTRAN code which is discussed.

  9. Microdialysis study of striatal dopaminergic dysfunctions induced by 3 MPa of nitrogen- and helium-oxygen breathing mixtures in freely moving rats.

    PubMed

    Dedieu, David; Balon, Norbert; Weiss, Michel; Risso, Jean-Jacques; Kinkead, Richard; Rostain, Jean-Claude

    2004-02-20

    Previous studies have demonstrated opposite effects of high-pressure helium and nitrogen on extracellular dopamine (DA) levels, which may reflect disturbances on the synthesis, release or metabolic mechanisms. Intrastriatal microdialysis was used to measure the precursor (tyrosine), DA and its metabolites (DOPAC, HVA) levels under nitrogen- or helium- at pressure up to 3 MPa. Under 3 MPa of helium-oxygen breathing mixtures, the extracellular concentration of tyrosine is decreased while the extracellular concentration of DA is increased. On the contrary, nitrogen-oxygen breathing mixture at the same pressure increased extracellular tyrosine concentration and decreased DA release. Under both conditions, an increment of the DOPAC and HVA levels could be noted. Our results suggest that changes in DA release and metabolism during high-pressure helium exposure reflect the effect of the pressure per se, whereas the intrinsic effects of narcotic gases, although sensitive to pressure, would be revealed by hyperbaric nitrogen exposure.

  10. Single crystal optic elements for helium atom microscopy

    NASA Astrophysics Data System (ADS)

    MacLaren, D. A.; Allison, W.; Holst, B.

    2000-07-01

    Focusing characteristics of asymmetrically bent single crystal mirrors are discussed in the context of fabricating an optic element for an helium atom microscope. We demonstrate the principle that deforming a clamped, elliptical, single crystal under electrostatic pressure can produce submicron focusing of an helium beam. We present a systematic procedure that may be used to fabricate high precision mirrors close to the Cartesian ideal of any chosen optical configuration. In particular, imaging systems with asymmetric mirror profiles are discussed. Results are independent of crystal characteristics and can be adapted to fit a range of experimental geometries. The calculations indicate that mirror-induced aberrations can be eliminated to fourth order by use of a single actuation electrode in an ideal system.

  11. Neovascular glaucoma after helium ion irradiation for uveal melanoma

    SciTech Connect

    Kim, M.K.; Char, D.H.; Castro, J.L.; Saunders, W.M.; Chen, G.T.; Stone, R.D.

    1986-02-01

    Neovascular glaucoma developed in 22 of 169 uveal melanoma patients treated with helium ion irradiation. Most patients had large melanomas; no eyes containing small melanomas developed anterior segment neovascularization. The mean onset of glaucoma was 14.1 months (range, 7-31 months). The incidence of anterior segment neovascularization increased with radiation dosage; there was an approximately three-fold increase at 80 GyE versus 60 GyE of helium ion radiation (23% vs. 8.5%) (P less than 0.05). Neovascular glaucoma occurred more commonly in larger tumors; the incidence was not affected by tumor location, presence of subretinal fluid, nor rate of tumor regression. Fifty-three percent of patients had some response with intraocular pressures of 21 mmHg or less to a combination of antiglaucoma treatments.

  12. Mechanical pumps for superfluid helium transfer in space

    NASA Technical Reports Server (NTRS)

    Izenson, M. G.; Swift, W. L.

    1988-01-01

    Two alternate mechanical pump concepts have been identified for the transfer of superfluid helium in space. Both pumps provide flow at sufficient head and have operating characteristics suitable for the Space Infrared Telescope Facility (SIRTF) refill mission. One pump operates at a relatively low speed and utilizes mechanical roller bearings, while the other operates at a higher rotational speed using either electromagnetic or tilting pad gas-dynamic bearings. The use of gas bearings requires transfer of normal helium so that the gas pressure within the pump casing is high enough to operate the bearings. The operating characteristics of both pumps are predicted, the dimensions are estimated and major technology issues are identified. The major issues for each pump design are cavitation performance and bearing development. Roller bearings require quantified reliability for operation in space while electromagnetic bearings require basic development as well as a complex control system. The low speed pump has significantly poorer hydraulic efficiency than the high speed pump.

  13. Helium Loop Cooling Channel Hydraulic Characterization

    SciTech Connect

    Olivas, Eric Richard; Morgan, Robert Vaughn; Woloshun, Keith Albert

    2015-07-02

    New methods for generating ⁹⁹Mo are being explored in an effort to eliminate proliferation issues and provide a domestic supply of ⁹⁹mTc for medical imaging. Electron accelerating technology is used by sending an electron beam through a series of ¹⁰⁰Mo targets. During this process a large amount of heat is created, which directly affects the operating temperature set for the system. In order to maintain the required temperature range, helium gas is used to serve as a cooling agent that flows through narrow channels between the target disks. Currently we are tailoring the cooling channel entrance and exits to decrease the pressure drop through the targets. Currently all hardware has be procured and manufactured to conduct flow measurements and visualization via solid particle seeder. Pressure drop will be studied as a function of mass flow and diffuser angle. The results from these experiments will help in determining target cooling geometry and validate CFD code results.

  14. 43 CFR 16.2 - Applications for helium disposition agreements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 43 Public Lands: Interior 1 2014-10-01 2014-10-01 false Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  15. 43 CFR 16.2 - Applications for helium disposition agreements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 1 2012-10-01 2011-10-01 true Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  16. 43 CFR 16.2 - Applications for helium disposition agreements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 43 Public Lands: Interior 1 2013-10-01 2013-10-01 false Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  17. 43 CFR 16.2 - Applications for helium disposition agreements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  18. 43 CFR 16.2 - Applications for helium disposition agreements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  19. Ras Laffan helium recovery unit 2

    NASA Astrophysics Data System (ADS)

    Fauve, Eric Arnaud; Grabié, Veronique; Grillot, David; Delcayre, Franck; Deschildre, Cindy

    2012-06-01

    In May 2010, Air Liquide was awarded a contract for the Engineering Procurement and Construction (Turnkey EPC) for a second helium recovery unit [RLH II] dedicated to the Ras Laffan refinery in Qatar. This unit will come in addition to the one [RLH I] delivered and commissioned by Air Liquide in 2005. It will increase the helium production of Qatar from 10% to 28% of worldwide production. RLH I and RLH II use Air Liquide Advanced Technologies helium liquefiers. With a production of 8 tons of liquid helium per day, the RLH I liquefier is the world largest, but not for long. Thanks to the newly developed turbine TC7, Air Liquide was able to propose for RLH II a single liquefier able to produce over 20 tons per day of liquid helium without liquid nitrogen pre-cooling. This liquefier using 6 Air Liquide turbines (TC series) will set a new record in the world of helium liquefaction.

  20. Gaseous insulators for high voltage electrical equipment

    DOEpatents

    Christophorou, Loucas G.; James, David R.; Pace, Marshall O.; Pai, Robert Y.

    1979-01-01

    Gaseous insulators comprise compounds having high attachment cross sections for electrons having energies in the 0-1.3 electron volt range. Multi-component gaseous insulators comprise compounds and mixtures having overall high electron attachment cross sections in the 0-1.3 electron volt range and moderating gases having high cross sections for inelastic interactions with electrons of energies 1-4 electron volts. Suitable electron attachment components include hexafluorobutyne, perfluorobutene-2, perfluorocyclobutane, perfluorodimethylcyclobutane, perfluorocyclohexene, perfluoromethylcyclohexane, hexafluorobutadiene, perfluoroheptene-1 and hexafluoroazomethane. Suitable moderating gases include N.sub.2, CO, CO.sub.2 and H.sub.2. The gaseous insulating mixture can also contain SF.sub.6, perfluoropropane and perfluorobenzene.