WorldWideScience

Sample records for Helium 5

  1. Acquisition system for the liquid helium L5 plant

    International Nuclear Information System (INIS)

    The technology of low temperature at the beginning of this century, developed for the production of oxygen nitrogen and rare gases, was the basis for setting of the cryogenic technology. Engineering and construction of cryogenic plants appear today implied in: science, research and development, space technology, nuclear power techniques. An important component in this technologies is the helium liquefier of type L5. This fully automatic cryoliquefier operates for purification, liquefaction as well as reliquefaction of helium gas evaporated in cryostat systems. A helium production plant consists mainly of cold chamber with aluminium heat exchangers, two gas-lubricated turbo-expanders, instrumentation and a programmable controller as well an oil-injected screw-compressor. Cold helium with 4.5 K is transferred through a special vacuum and super insulated line to the tank. In liquefaction mode without LN2-precooling the performance data of this plant is 5 l/hour at 4.5 K. In the paper there are presented the work of designing and developing of a performing liquid helium delivery system corresponding with the basic equipment and accessories used in a L5 type helium liquefactor. The process software of LINDE L5 installation was updated and adapted to our technical conditions from our cryogenic laboratory. Therefore the new Lab-View based programme derived from the functions command protocol, allowed a reliable control on the technological process and induced as well several determinations on the performance of the process as following: - verification of the theoretical models of the cryogenic cycle energetic dimensions; - Increasing thermodynamic performances of different components of the cryogenic cycle by remodeling the geometrical flowing zones, based on gas dynamic studies, in concordance with the thermophysical characteristics of the gas; - study of the dynamic behavior of the installation by evaluation of the transient processes. (authors)

  2. First principles assessment of helium trapping in Y2TiO5 in nano-featured ferritic alloys

    Science.gov (United States)

    Jin, Yanan; Jiang, Yong; Yang, Litong; Lan, Guoqiang; Robert Odette, G.; Yamamoto, Takuya; Shang, Jiacheng; Dang, Ying

    2014-10-01

    Nano-scale Y2Ti2O7 and Y2TiO5 oxides are the major features that provide high strength and irradiation tolerance in nano-structured ferritic alloys. Here, we employ density functional theory to study helium trapping in Y2TiO5. The results suggest that helium is more deeply trapped in Y2TiO5 compared to Y2Ti2O7. Helium occupies open channels in Y2TiO5, where it weakly chemically interacts with neighboring oxygen anions, and results in less volume expansion compared to Y2Ti2O7, reducing strains in the iron matrix. The corresponding helium mobility in these channels is very high. While its ultimate fate is to form oxide/matrix interface bubbles, transient deep trapping of helium in oxides plays a major role in the ability of NFA to manage helium distribution.

  3. Heat transfer design and performance of a helium cryostat operating at 6.5 K

    Energy Technology Data Exchange (ETDEWEB)

    Gasteyer, T.H.; Krempetz, K.J.; Lee, A.; Rucinski, R.A.; Stefanik, A.M. [Fermi National Accelerator Lab., Batavia, IL (United States)

    1994-12-31

    A liquid helium cryostat has been designed and operated for the purpose of testing visible light photon counter (VLPC) chips at 6.5 K. To achieve the desired operational characteristics for the VLPC devices their operating temperature is restricted to 6.5 K +/{minus} 0.1 K. They will be used in a scintillating fiber tracker being proposed as part of an upgrade of the D(0) detector at Fermilab. The final version of the scintillating fiber tracker will contain roughly 100,000 VLPC channels. Two cryostats with identical thermal design (a 128 channel and a 3072 channel design) have been built to perform the initial VLPC testing. The heat transfer needed to maintain the VLPC at its operating temperature occurs by conduction across an annular helium gas gap to a liquid helium reservoir. Helium boiloff is used to intercept conduction heat leak to the liquid reservoir. ANSYS finite element heat transfer analysis was utilized in the thermal design of the cryostat. The cryostat design and thermal performance (predicted and measured) are presented.

  4. Antiprotonic helium

    CERN Multimedia

    Eades, John

    2005-01-01

    An exotic atom in w hich an electron and an antiproton orbit a helium nucleus could reveal if there are any differences between matter and antimatter. The author describes this unusual mirror on the antiworld (5 pages)

  5. Helium focused ion beam fabricated plasmonic antennas with sub-5 nm gaps

    International Nuclear Information System (INIS)

    We demonstrate a reliable fabrication method to produce plasmonic dipole nanoantennas with gap values in the range of 3.5–20 nm. The method combines electron beam lithography to create gold nanorods and helium focused ion beam milling to cut the gaps. Results show a reproducibility within 1 nm. Scattering spectra of antennas show a red shift of resonance wavelengths and an increase of the intensity of resonance peaks with a decrease of the gap size, which is in agreement with finite element simulations. The measured refractive index sensitivity was about 250 nm per refractive index unit for antennas with gap values below 5 nm. (paper)

  6. Properties of V-(8-9)Cr-(5-6)Ti alloys irradiated in the dynamic helium charging experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Nowicki, L.; Smith, D.L. [Argonne National Lab., IL (United States)

    1996-10-01

    In the Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in vanadium alloy specimens by the decay of tritium during irradiation to 18-31 dpa at 425-600{degrees}C in lithium-filled capsules in the Fast Flux Test Facility. This report presents results of postirradiation tests of tensile properties and density change in V-8Cr-6Ti and V-9Cr-5Ti. Compared to tensile properties of the alloys irradiated in the non-DHCE (helium generation negligible), the effect of helium on tensile strength and ductility of V-8Cr-6Ti and V-9Cr-5Ti was insignificant after irradiation and testing at 420, 500, and 600{degrees}C. Both alloys retained a total elongation of >11 % at these temperatures. Density change was <0.48% for both alloys.

  7. Tensile and fracture properties of EBR-II-irradiated V-15Cr-5Ti containing helium

    International Nuclear Information System (INIS)

    The alloy V-15Cr-5Ti was cyclotron-implanted with 80 appm He and subsequently irradiated in the Experimental Breeder Reactor (EBR-II) to 30 displacements per atom (dpa). The same alloy was also irradiated in the 10, 20, and 30% cold-worked conditions. Irradiation temperatures ranged from 400 to 7000C. No significant effects of helium on mechanical properties were found in this temperature range although the neutron irradiation shifted the temperature of transition from cleavage to ductile fracture to about 6250C. Ten percent cold work was found to have a beneficial effect in reducing the tendency for cleavage fracture following irradiation, but high levels (20%) were observed to reduce ductility. Still higher levels (30%) improved ductility by inducing recovery during the elevated-temperature irradiation. Swelling was found to be negligible, but precipitates - titanium oxides or carbonitrides - contained substantial cavities

  8. Elevated-temperature tensile properties of V--15Cr--5Ti containing helium introduced by ion bombardment and tritium decay

    International Nuclear Information System (INIS)

    The tensile properties of V-15 wt percent Cr-5 wt percent Ti containing 25-35 appm He have been investigated from 600 to 8000C. Helium charging was accomplished by the ''tritium trick'' and both thin-sheet and cylindrical specimens were tested. Specimens containing helium showed decreases in elongation at temperatures of 7000C and above, but the cylindrical specimens with or without helium exhibited considerably greater elongations than the sheet specimens under corresponding conditions. A comparison of the tensile properties of the sheet specimens charged by the ''tritium trick'' with the properties of Cyclotron-injected sheet specimens from a previous study indicates that the Cyclotron-injected specimens exhibited greater ductility than the specimens charged by the ''tritium trick.'' The onset of gross embrittlement occurred between 700 and 7500C in both cases

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

    Science.gov (United States)

    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.

  10. Recoil and fast-particle spectrometers for the study of 5GeV pion-helium interactions

    International Nuclear Information System (INIS)

    The instrumentation of an experiment, in which the recoil as well as the fast-particle is measured, is described. The principal aim of the experiment is to search for isobar configurations in the nuclear function of helium by studying 5GeV pion-helium interactions and one pion-proton interactions. In the both first reactions the object X is a pion-nucleon system, which may have been produced on one of the bound nucleons in helium or may have existed prior to the collision. The last one gives the production amplitude from free nucleons. The final-state pions which are scattered in a narrow forward half cone, are measured in a spectrometer consisting of multiwire proportional counters (MWPC) and a magnet. The residual slow nuclei are measured and identified in a recoil spectrometer with MWPC's, solid state detectors and scintillators as the basic components. With these spectrometers the nuclear and the hadron states can be specified up to very high energies as long as the missing mass resolution is sufficient to separate the different resonances in X from each other

  11. A 6 kW at 4.5 K helium refrigerator for CERN's Cryogenic Test Station

    International Nuclear Information System (INIS)

    For purposes of testing the present LEP superconducting resonant cavities and the future LHC magnets, CERN built a test station the cryogenic power of which is presently supplied by a dedicated 6 kW at 4.5 K helium refrigerator. The thermodynamic cycle is discussed and special emphasis is put on a new cryogenic expansion turbine operating in the liquid phase. Information is given about: the cycle screw compressors' performances, the general performance of the refrigerator, the expected efficiency enhancement due to the liquid turbine, an off-design turn down operation

  12. Observation of turbulent waves in a helium plasma by optical spectroscopy, ch. 5

    International Nuclear Information System (INIS)

    From the combined Stark-Zeeman pattern of helium allowed and forbidden optical lines the frequency spectrum, the field strength and the dominant polarization of microfields were determined in a turbulent plasma. Two frequent domains of oscillations were found in a turbulent heating experiment: low-frequency oscillations with dominant polarization perpendicular to the current direction and high-frequency osillations (f approximately fsub(pe)) with random polarization. The r.m.s. field strength of the oscillations is between 2 kV/cm and 10 kV/cm. The energy density of turbulent microfields amounts to 1% of the thermal energy density. (Auth.)

  13. Interplay between pion absorption and inclusive-inelastic scattering on hydrogen and helium isotopes for 96. 5-MeV kinetic energy pions

    Energy Technology Data Exchange (ETDEWEB)

    Storm, D.W.

    1991-01-01

    Measurements of double-differential cross sections for inclusive-inelastic scattering of 96.5-MeV pions from hydrogen and helium isotopes are presented. Differential and angle-integrated cross sections are obtained. Distorted wave impulse approximation calculations are reported. The interplay between inclusive-inelastic scattering and pion absorption is discussed. 13 refs., 5 figs., 1 tab.

  14. The attractive well in the helium interaction as simplified by thermal diffusion experiments between 2 and 5K

    International Nuclear Information System (INIS)

    Knowledge of the interaction potential for two helium atoms has been extended considerably in the past several years both theoretically and experimentally. The repulsive part of the potential has been probed by scattering experiments, and short range forces have been deduced therefrom as well as from high temperature physical property data. The long-range attractive terms are generally considered to be well known. Recent work has concentrated, therefore, on the attractive well. The thermal diffusion factor ?sub(T), has been found to be particularly useful for discriminating among proposed interaction potentials becuase it exhibits a high degreee of sensitivity to the interaction provided one avoids the 'insensitive' temperature region. This is generally thought to lie in a reduced temperature range between 23He-4He at average temperatures between 2 and 5K. (Auth.)

  15. Helium cryogenics

    CERN Document Server

    Van Sciver, Steven W

    2012-01-01

    Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

  16. Does One Need a 4.5 K Screen in Cryostats of Superconducting Accelerator Devices Operating in Superfluid Helium? Lessons from the LHC

    CERN Document Server

    Lebrun, Ph; Tavian, L

    2014-01-01

    Superfluid helium is increasingly used as a coolant for superconducting devices in particle accelerators: the lower temperature enhances the performance of superconductors in high-field magnets and reduces BCS losses in RF acceleration cavities, while the excellent transport properties of superfluid helium can be put to work in efficient distributed cooling systems. The thermodynamic penalty of operating at lower temperature however requires careful management of the heat loads, achieved inter alia through proper design and construction of the cryostats. A recurrent question appears to be that of the need and practical feasibility of an additional screen cooled by normal helium at around 4.5 K surrounding the cold mass at about 2 K, in such cryostats equipped with a standard 80 K screen. We introduce the issue in terms of first principles applied to the configuration of the cryostats, discuss technical constraints and economical limitations, and illustrate the argumentation with examples taken from large proj...

  17. Metastability Exchange Optical Pumping of Helium-3 at High Pressures and 1.5 T: Comparison of two Optical Pumping Transitions

    OpenAIRE

    Abboud, Marie; Sinatra, Alice; Tastevin, Geneviève; Nacher, Pierre-Jean; Maître, Xavier

    2005-01-01

    At low magnetic field, metastability exchange optical pumping of helium-3 is known to provide high nuclear polarizations for pressures around 1 mbar. In a recent paper, we demonstrated that operating at 1.5 T can significantly improve the results of metastability exchange optical pumping at high pressures. Here, we compare the performances of two different optical pumping lines at 1.5 T, and show that either the achieved nuclear polarization or the production rate can be opt...

  18. Effect of dynamically charged helium on tensile properties of V-5Ti, V-4Cr-4Ti, and V-3Ti-1Si

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Loomis, B.A.; Nowicki, L.; Smith, D.L. [Argonne National Laboratory, Chicago, IL (United States)

    1996-04-01

    In the Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of {approx}0.4 to 4.2 appm He/dpa by the decay of tritium during irradiation to 18-31 dpa at 424-600{degrees}C in the lithium-filled DHCE capsules in the Fast Flux Test Facility. This report presents results of postirradiation tests of tensile properties of V-5Ti, V-4Cr-4Ti, V-3Ti-1Si. The effect of helium on tensile strength and ductility was insignificant after irradiation and testing at >420{degrees}C. Contrary to initial expectation, room temperature ductility of DHCE specimens was higher than that on non-DHCE specimens, whereas strength was lower, indicating that different types of hardening centers are produced during DHCE and non-DHCE irradiation. In strong contrast to results of tritium-trick experiments, in which dense coalescence of helium bubbles is produced on grain boundaries in the absence of displacement damage, no intergranular fracture was observed in any tensile specimens irradiated in the DHCE.

  19. High nuclear polarization of helium-3 at low and high pressure by metastability exchange optical pumping at 1.5 Tesla

    OpenAIRE

    Abboud, Marie; Sinatra, Alice; Maître, Xavier; Tastevin, Geneviève; Nacher, Pierre-Jean

    2003-01-01

    We perform metastability exchange optical pumping of helium-3 in a strong magnetic field of 1.5 T. The achieved nuclear polarization, from 80% at 1.33 mbar to 25% at 67 mbar, shows a substantial improvement at high pressures with respect to standard low-field optical pumping. The specific mechanisms of metastability exchange optical pumping at high field are investigated, advantages and intrinsic limitations are discussed. From a practical point of view, our results open the...

  20. Fast leak of a channel filled with helium at a pressure of 2 bars (channel H5)

    International Nuclear Information System (INIS)

    The loss of seal of a helium-filled channel opening the entire cross section of the front part leads to a fast leak. The channel fills to the upper generatrix of the leak orifice and part of the helium contained in the channel escapes into the circuit. The pressure drop in the reflector can lead to reactor and main pump shutdown. On the other hand, the Cooling Circuit Shutdown Bar circuit pumps remain in operation. This paper evaluates the consequences of an incident of this nature for the reactor and the surrounding experimental zones

  1. Disalignment rates of the neon 2p5 and 2p10 atoms due to helium atom collisions measured at temperatures between 77 and 294 K

    Science.gov (United States)

    Matsukuma, H.; Shikama, T.; Hasuo, M.

    2011-04-01

    Using a positive column of helium-neon glow discharge plasma at several temperatures between 77 and 294 K, the disalignment rates of excited neon atoms in the 2p5 and 2p10 (in Paschen notation) levels are measured by a polarization-resolved laser-induced fluorescence technique. For the 2p10 case, the disalignment rate due to radiation reabsorption is evaluated from the optical thickness of the plasma measured by a self-absorption method, and then is subtracted from the disalignment rate measured. From the slope of the obtained disalignment rate plotted against the helium atom density we determine the rate coefficients due to helium atom collisions. These rate coefficients are compared with the results of quantum multi-channel close-coupling calculations using the modified long-range potentials proposed by Bahrim and Khadilkar (2009 Phys. Rev. A 79 042715) from the original potentials of Hennecart and Masnou-Seeuws (1985 J. Phys. B: At. Mol. Phys. 18 657). Our present experiment agrees excellently with the theory for the 2p5 level at any temperatures between 77 and 294 K, and for the 2p10 state only at 294 K. Below 294 K, the experimental rate coefficients for the 2p10 state show a more rapid decrease with the decrease in temperature than the theory predicts.

  2. Small scale helium liquefaction systems

    International Nuclear Information System (INIS)

    We have developed two small-scale helium liquefaction systems that provide solutions for liquid helium usage in laboratories. These helium liquefaction systems use two-stage pulse tube cryocoolers to provide cooling at 4 K. The cold head/liquefier resides inside of the neck of a dewar. The room temperature helium gas to be liquefied enters the neck of the dewar and is efficiently pre-cooled down to 5-6 K by means of the regenerators and pulse tubes of the cold head before being liquefied. Two models of liquefaction system, LHeP12 and LHeP18, produce liquid helium from room temperature gas with the rates of >12 L/day and 18 L/day.

  3. Helium behaviour in nuclear glasses

    International Nuclear Information System (INIS)

    The present thesis focuses on the study of helium behavior in R7T7 nuclear waste glass. Helium is generated by the minor actinides alpha decays incorporated in the glass matrix. Therefore, four types of materials were used in this work. These are non radioactive R7T7 glasses saturated with helium under pressure, glasses implanted with 3He+ ions, glasses doped with curium and glasses irradiated in nuclear reactor. The study of helium solubility in saturated R7T7 glass has shown that helium atoms are inserted in the glass free volume. The results yielded a solubility of about 1016 at. cm-3 atm.-1. The incorporation limit of helium in this type of glass has been determined; its value amounted to about 2*1021 at. cm-3, corresponding to 2.5 at.%. Diffusion studies have shown that the helium migration is controlled by the single population dissolved in the glass free volume. An ideal diffusion model was used to simulate the helium release data which allowed to determine diffusion coefficients obeying to the following Arrhenius law: D = D0exp(-Ea/kBT), where D0 = 2.2*10-2 and 5.4*10-3 cm2 s-1 and Ea = 0.61 eV for the helium saturated and the curium doped glass respectively. These results reflect a thermally activated diffusion mechanism which seems to be not influenced by the glass radiation damage and helium concentrations studied in the present work (up to 8*1019 at. g-1, corresponding to 0.1 at.%). Characterizations of the macroscopic, structural and microstructural properties of glasses irradiated in nuclear reactor did not reveal any impact associated with the presence of helium at high concentrations. The observed modifications i.e. a swelling of 0.7 %, a decrease in hardness by 38 %, an increase between 8 and 34 % of the fracture toughness and a stabilization of the glass structure under irradiation, were attributed to the glass nuclear damage induced by the irradiation in reactor. Characterizations by SEM and TEM of R7T7 glasses implanted with helium at high concentrations, doped with curium and irradiated in nuclear reactor showed a homogeneous microstructure free of helium bubbles, pores or cracking. The results of the present work were used to develop a long-term diffusion model of helium in an industrial R7T7 nuclear waste glass. The model considers the thermal history, the fracturing and the alpha activity of the glass. (author)

  4. Does one need a 4.5 K screen in cryostats of superconducting accelerator devices operating in superfluid helium? lessons from the LHL

    Energy Technology Data Exchange (ETDEWEB)

    Lebrun, Philippe [DG unit, CERN, CH-1211 Geneva 23 (Switzerland); Parma, Vittorio; Tavian, Laurent [TE department, CERN, CH-1211 Geneva 23 (Switzerland)

    2014-01-29

    Superfluid helium is increasingly used as a coolant for superconducting devices in particle accelerators: the lower temperature enhances the performance of superconductors in high-field magnets and reduces BCS losses in RF acceleration cavities, while the excellent transport properties of superfluid helium can be put to work in efficient distributed cooling systems. The thermodynamic penalty of operating at lower temperature however requires careful management of the heat loads, achieved inter alia through proper design and construction of the cryostats. A recurrent question appears to be that of the need and practical feasibility of an additional screen cooled by normal helium at around 4.5 K surrounding the cold mass at about 2 K, in such cryostats equipped with a standard 80 K screen. We introduce the issue in terms of first principles applied to the configuration of the cryostats, discuss technical constraints and economical limitations, and illustrate the argumentation with examples taken from large projects confronted with this issue, i.e. CEBAF, SPL, ESS, LHC, TESLA, European X-FEL, ILC.

  5. Transient characteristic analyses of ex-vessel coolant pipe break for Chinese helium-cooled solid breeder TBM based on RELAP5 code

    International Nuclear Information System (INIS)

    Chinese helium-cooled solid breeder (CH HCSB) test blanket module (TBM) with helium cooling system and secondary cooling water system was modeled and thermal-hydraulic behavior and safety performance of the system were assessed using the RELAP5/MOD3.4 code. According to the accident sequences of ITER accident analysis specification for TBM, the transient analysis of the design basis ex-vessel coolant pipe break accident was carried out. The influences of different break locations, leak areas and plasma shutdown processes on the first wall of TBM were compared. The results indicate that it is much more danger when the pipe break occurs at the downstream side of the helium circulator compared with that at upstream side. The results also show that the accident consequence is worse in case of smaller area break than that in case of larger area break. In case of much more severe accident that the ex-vessel break leads to the break of TBM the first wall, the results reveal that the decay heat can be removed to cool down TBM by natural circulation and radiation. The first wall melting can be avoided if the method to shutdown plasma within 3 seconds in case of ex-vessel break is adopted. (authors)

  6. Exotic helium atoms

    International Nuclear Information System (INIS)

    Recent progress on the precision laser spectroscopy of antiprotonic helium atoms, as well as on the x-ray spectroscopy of kaonic helium atoms are presented. These two may appear to be unrelated topics (except for the fact that both being exotic helium atoms), but in fact a past study of kaonic helium system led to the serendipitous discovery of antiprotonic helium. Some historical background connecting these two exotic helium atoms, as well as future prospects are discussed. (author)

  7. Helium production cross section measurement by helium atoms measurement system

    International Nuclear Information System (INIS)

    Proton-induced helium production cross sections for nickel at proton energies up to 16 MeV have been measured with a helium accumulation method. A sample is a nickel sheet (chemical purity 99.98%, sizes 12x9x0.119 mm3) sandwiched between two gold foils (chemical purity 99.99%, size 12x9x0.051 mm3) which are collectors for the emitted ?-particles from the nickel surfaces. Nine nickel samples were irradiated by protons ranging from 8.8 to 17.5 MeV at Kyushu University Tandem Accelerator Laboratory. The number of helium atoms produced and accumulated in the nickel foil and two gold collectors was measured using the helium atoms measurement system. (author)

  8. Ionized helium afterglow study

    International Nuclear Information System (INIS)

    In order to take into account the characteristics of ionized helium, under relaxation conditions, in the determination of the unknown coefficients of the reaction rates and more particularly those of the recombination of H2+ ions, a method has been developed which consists in recovering, using a system of differential equations with coupled partial derivatives, the set of all the physical quantities which can at the moment be measured as a function of time in a helium after-discharge. The energy balance of the maxwellian electrons and the speed distribution function of the electrons were studied in details and calculated as a function of time and location in space. The non-maxwellian electrons were included in the calculations. Measurements were made over a large range of experimental conditions using 5 different diagnoses: UHF interferometry in the X band, UHF radiometry in the X band, mass spectrometry, optical absorption spectrometry and optical emission spectrometry. All experimental data, obtained at 293 deg K and at seven different pressures ranging from 5 to 100 Torr were perfectly reproduced by the proposed system of differential equations, with the same reaction rate coefficients and the same constants. The method developed here gives a complete solution for the helium after-discharge at room temperature over a wide range of experimental conditions. It underlines the important reactions within the ionized gas, gives the absolute value and the dependences of the electron-He2+ ion recombination coefficient and allows the determination of the elementary mechanisms causing these dependences. It also gives the coefficients and the reaction rates of all the other elementary mechanisms which, besides recombination, determine the relaxation of ionized helium

  9. Helium in inert matrix dispersion fuels

    International Nuclear Information System (INIS)

    The behaviour of helium, an important decay product in the transmutation chains of actinides, in dispersion-type inert matrix fuels is discussed. A phenomenological description of its accumulation and release in CERCER and CERMET fuel is given. A summary of recent He-implantation studies with inert matrix metal oxides (ZrO2, MgAl2O4, MgO and Al2O3) is presented. A general picture is that for high helium concentrations helium and vacancy defects form helium clusters which convert into over-pressurized bubbles. At elevated temperature helium is released from the bubbles. On some occasions thermal stable nano-cavities or nano-pores remain. On the basis of these results the consequences for helium induced swelling and helium storage in oxide matrices kept at 800-1000 deg. C will be discussed. In addition, results of He-implantation studies for metal matrices (W, Mo, Nb and V alloys) will be presented. Introduction of helium in metals at elevated temperatures leads to clustering of helium to bubbles. When operational temperatures are higher than 0.5 melting temperature, swelling and helium embrittlement might occur

  10. Standard Guide for Simulation of Helium Effects in Irradiated Metals

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1996-01-01

    1.1 This guide provides advice for conducting experiments to investigate the effects of helium on the properties of metals where the technique for introducing the helium differs in some way from the actual mechanism of introduction of helium in service. Simulation techniques considered for introducing helium shall include charged particle implantation, exposure to ?-emitting radioisotopes, and tritium decay techniques. Procedures for the analysis of helium content and helium distribution within the specimen are also recommended. 1.2 Two other methods for introducing helium into irradiated materials are not covered in this guide. They are the enhancement of helium production in nickel-bearing alloys by spectral tailoring in mixed-spectrum fission reactors, and isotopic tailoring in both fast and mixed-spectrum fission reactors. These techniques are described in Refs (1-5). Dual ion beam techniques (6) for simultaneously implanting helium and generating displacement damage are also not included here. This lat...

  11. Electrons at helium interfaces

    OpenAIRE

    Leiderer, Paul

    1984-01-01

    Two-dimensional layers of charges trapped at the boundaries between the various helium phases strongly interact with these interfaces at high electric fields. The coupling, which leads to an electrohydrodynamic instability, provides new methods for studying helium properties.

  12. Ultracold Metastable HELIUM-4 and HELIUM-3 Gases

    Science.gov (United States)

    Vassen, W.; Jeltes, T.; McNamara, J. M.; Tychkov, A. S.; Hogervorst, W.; van Leeuwen, K. A. H.; Krachmalnicoff, V.; Schellekens, M.; Perrin, A.; Chang, H.; Boiron, D.; Aspect, A.; Westbrook, C. I.

    2008-04-01

    We discuss our work to obtain a condensate containing more than 107 atoms and the first degenerate Fermi gas in a metastable state. Sympathetic cooling with Helium-4 is used to cool 106 Helium-3 atoms to a temperature T/TF < 0.5. The ultracold bosonic and fermionic gases have been used to observe the Hanbury Brown and Twiss effect for both isotopes, showing bunching for the bosons and antibunching for the fermions. A proposal for high resolution spectroscopy at 1.557 ?m, connecting both metastable states directly, is discussed at the end.

  13. Spent Nuclear Fuel (SNF) Project Cask and MCO Helium Purge System Design Review Completion Report - Project A.5 and A.6

    International Nuclear Information System (INIS)

    This report documents the results of the design verification performed on the Cask and Multiple Canister Over-pack (MCO) Helium Purge System. The helium purge system is part of the Spent Nuclear Fuel (SNF) Project Cask Loadout System (CLS) at 100K area. The design verification employed the ''Independent Review Method'' in accordance with Administrative Procedure (AP) EN-6-027-01

  14. Regimes of Helium Burning

    Energy Technology Data Exchange (ETDEWEB)

    Timmes, F. X.; Niemeyer, J. C.

    2000-07-10

    The burning regimes encountered by laminar deflagrations and Zeldovich von Neumann Doering [ZND] detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts that start with a thermonuclear runaway on the surface of a neutron star and to the thin-shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial direction encounter a transition from the distributed regime to the flamelet regime at a density of {approx}108 g cm-3. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}106 g cm-3. Self-sustained laminar deflagrations traveling in the radial direction cannot exist below this density. Similarly, the planar ZND detonation width becomes larger than the pressure scale height at {approx}107 g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. In the thin helium shell case, turbulent deflagrations traveling in the lateral or radial direction encounter the distributed regime at densities below {approx}107 g cm-3 and the flamelet regime at larger densities. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than {approx}104 g cm-3, indicating that steady state laminar deflagrations cannot form below this density. The planar ZND detonation width becomes larger than the pressure scale height at {approx}5x10{sup 4} g cm-3, suggesting that steady state, self-sustained detonations cannot come into existence in the radial direction. (c) 2000 The American Astronomical Society.

  15. A helium regenerative compressor

    International Nuclear Information System (INIS)

    This paper discusses the design and performance of a regenerative compressor that was developed primarily for use in cryogenic helium systems. The objectives for the development were to achieve acceptable efficiency in the machine using conventional motor and bearing technology while reducing the complexity of the system required to control contamination from the lubricants. A single stage compressor was built and tested. The compressor incorporates aerodynamically shaped blades on a 218 mm (8.6 inches) diameter impeller to achieve high efficiency. A gas-buffered non-contact shaft seal is used to oppose the diffusion of lubricant from the motor bearings into the cryogenic circuit. Since it is a rotating machine, the flow is continuous and steady, and the machine is very quiet. During performance testing with helium, the single stage machine has demonstrated a pressure ratio of 1.5 at a flow rate of 12 g/s with measured isothermal efficiencies in excess of 30%. This performance compares favorably with efficiencies generally achieved in oil flooded screw compressors

  16. Spent Nuclear Fuel (SNF) Project Cask and MCO Helium Purge System Design Review Completion Report Project A.5 and A.6

    Energy Technology Data Exchange (ETDEWEB)

    ARD, K.E.

    2000-04-19

    This report documents the results of the design verification performed on the Cask and Multiple Canister Over-pack (MCO) Helium Purge System. The helium purge system is part of the Spent Nuclear Fuel (SNF) Project Cask Loadout System (CLS) at 100K area. The design verification employed the ''Independent Review Method'' in accordance with Administrative Procedure (AP) EN-6-027-01.

  17. Quenching of the resonance 5s(3P1) state of krypton atoms in collisions with krypton and helium atoms

    International Nuclear Information System (INIS)

    The processes of collision quenching of the resonance 5s[3/2]1o(3P1) state of the krypton atom are studied by the absorption probe method in electron-beam-excited high-pressure He – Kr mixtures with a low content of krypton. The rate constants of plasmochemical reactions Kr* + Kr + He ? Kr*2 + He [(4.21 ± 0.42) × 10-33 cm6 s-1], Kr* + 2He ? HeKr* + He [(4.5 ± 1.2) × 10-36 cm6 s-1] and Kr* + He ? products + He [(2.21 ± 0.22) × 10-15 cm3 s-1] are measured for the first time. The rate constants of similar reactions are refined for krypton in the metastable 5s[3/2]2o (3P2) state. (laser applications and other topics in quantum electronics)

  18. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  19. Antiprotonic helium atoms

    International Nuclear Information System (INIS)

    Metastable antiprotonic helium atoms 3,4Hep bar e have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum L ? 30-40. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed. 26 refs., 3 tabs

  20. Cooling with Superfluid Helium

    CERN Document Server

    Lebrun, P

    2014-01-01

    The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics

  1. ESCAR helium refrigeration system

    International Nuclear Information System (INIS)

    The ESCAR cryogenic system, with its two distribution loops offers many advantages. The system models the kind of system that can and should be used in future accelerators. The refrigerator cold box, with its turbine expanders, and the helium screw compressor system represent a significant step in the development of reliable helium refrigeration systems. (auth)

  2. Helium the disappearing element

    CERN Document Server

    Sears, Wheeler M

    2015-01-01

    The subject of the book is helium, the element, and its use in myriad applications including MRI machines, particle accelerators, space telescopes, and of course balloons and blimps. It was at the birth of our Universe, or the Big Bang, where the majority of cosmic helium was created; and stellar helium production continues. Although helium is the second most abundant element in the Universe, it is actually quite rare here on Earth and only exists because of radioactive elements deep within the Earth. This book includes a detailed history of the discovery of helium, of the commercial industry built around it, how the helium we actually encounter is produced within the Earth, and the state of the helium industry today. The gas that most people associate with birthday party balloons is running out. “Who cares?” you might ask. Well, without helium, MRI machines could not function, rockets could not go into space, particle accelerators such as those used by CERN could not operate, fiber optic cables would not...

  3. Disalignment rates of the neon 2p{sub 5} and 2p{sub 10} atoms due to helium atom collisions measured at temperatures between 77 and 294 K

    Energy Technology Data Exchange (ETDEWEB)

    Matsukuma, H; Shikama, T; Hasuo, M, E-mail: hiraku@t04.mbox.media.kyoto-u.ac.jp [Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University, Yoshida Hon-machi, Sakyo, Kyoto, 606-8501 (Japan)

    2011-04-14

    Using a positive column of helium-neon glow discharge plasma at several temperatures between 77 and 294 K, the disalignment rates of excited neon atoms in the 2p{sub 5} and 2p{sub 10} (in Paschen notation) levels are measured by a polarization-resolved laser-induced fluorescence technique. For the 2p{sub 10} case, the disalignment rate due to radiation reabsorption is evaluated from the optical thickness of the plasma measured by a self-absorption method, and then is subtracted from the disalignment rate measured. From the slope of the obtained disalignment rate plotted against the helium atom density we determine the rate coefficients due to helium atom collisions. These rate coefficients are compared with the results of quantum multi-channel close-coupling calculations using the modified long-range potentials proposed by Bahrim and Khadilkar (2009 Phys. Rev. A 79 042715) from the original potentials of Hennecart and Masnou-Seeuws (1985 J. Phys. B: At. Mol. Phys. 18 657). Our present experiment agrees excellently with the theory for the 2p{sub 5} level at any temperatures between 77 and 294 K, and for the 2p{sub 10} state only at 294 K. Below 294 K, the experimental rate coefficients for the 2p{sub 10} state show a more rapid decrease with the decrease in temperature than the theory predicts.

  4. Studies of helium breakdown at low temperatures

    International Nuclear Information System (INIS)

    For designing cryogenic installations the breakdown strength of helium at temperatures near absolute zero has to be known. Various breakdown strengths are reported in literature concerning liquid helium. It is the objective of these studies to find an explanation for the different breakdown strengths by suitable variation of parameters. Various electrode materials commonly used in low temperature techniques with different sample preparation are used to measure breakdown strength of liquid helium in the gap range from 0.5 mm to 3 mm. A substantial influence of roughness, oxide layer and microcracks on strength is revealed. These terms are summarized and defined as 'condition of the electrode surface'. Taking this into account the various breakdown strengths can be qualitatively explained. Based on these results breakdown strength in supercritical high density helium is examined. A Paschen-curve can be given for this thermodynamical region. (orig./WL)

  5. KSTAR Helium Refrigeration System Design and Manufacturing

    International Nuclear Information System (INIS)

    The tokamak developed in the KSTAR (Korean Superconducting Tokamak Advanced Research) project makes intensive use of superconducting magnets operated at 4.5 K. The cold components of the KSTAR tokamak require forced flow of supercritical helium for magnets/structure, boiling liquid helium for current leads, and gaseous helium for thermal shields. The cryogenic system will provide stable operation and full automatic control. A three-pressure helium cycle composed of six turbines has been customised design for this project. The '' design '' operating mode results with a system composed of a 9 kW refrigerator (including safety margin) and using gas and liquid storages for mass balancing. During Shot/Standby mode, the heat loads are highly time-dependent. A thermal damper is used to smooth these variations and will allow stable operation. (author)

  6. Small size helium refrigerating systems

    International Nuclear Information System (INIS)

    Recently, for cooling the superconducting magnets used for medical nuclear magnetic resonance diagnostic system and for cooling Josephson elements, the development of the small helium refrigerating system of low vibration and maintenance free has been advanced. As the refrigerating system satisfying this requirement, a compact helium refrigerator using super-small, superhigh speed expansion turbines and diffusion joined laminate heat exchangers and a single stage screw compressor were developed. As the results of having carried out the performance test by the combination of these, the efficiency of the first turbine was 41 %, and that of the second turbine was 60 %. Besides, the refrigerating capacity was about 70 W (at 77 K) + 5 W (at 4.5 K). Thus the prospect of putting it in practical use was able to be obtained. The small helium refrigerator is composed of a compressor unit and a cold box containing two expansion turbines, five heat exchangers and Joule Thompson valves. These components are described, and the results of experiment are reported. (Kako, I.)

  7. Helium mobility in advanced nuclear ceramics

    International Nuclear Information System (INIS)

    The main goal of this work is to improve our knowledge on the mechanisms able to drive the helium behaviour in transition metal carbides and nitrides submitted to thermal annealing or ion irradiation. TiC, TiN and ZrC polycrystals were implanted with 3 MeV 3He ions at room temperature in the fluence range 2 * 1015 et 6 * 1016 cm-2. Some of them have been pre-irradiated with self-ions (14 MeV Ti or Zr). Fully controlled thermal annealing tests were subsequently carried out in the temperature range 1000 - 1600 C for two hours. The evolution of the helium depth distribution in function of implantation dose, temperature and pre-irradiation dose was measured thanks to the deuteron-induced nuclear reaction 3He(d, p0)4He between 900 keV and 1.8 MeV. The microstructure of implanted and annealed samples was investigated by transmission electron microscopy on thin foils prepared using the FIB technique. Additional characterization tools, as X-ray diffraction and Raman microspectrometry, have been also applied in order to obtain complementary information. Among the most relevant results obtained, the following have to be outlined: - double-peak helium depth profile was measured on as implanted sample for the three compounds. The first peak is located near the end of range and includes the major part of helium, a second peak located close to the surface corresponds to the helium atoms trapped by the native vacancies; - the helium retention capacity in transition metal carbides and nitrides submitted to fully controlled thermal treatments varies according to ZrC0.92 ? TiC0.96 ? TiN0.96; - whatever the investigated material, a self-ion-induced pre-damaging does not modify the initial helium profile extent. The influence of the post-implantation thermal treatment remains preponderant in any case; - the apparent diffusion coefficient of helium is in the range 4 * 10-18 - 2 * 10-17 m2 s-1 in TiC0.96 and 3.5 * 10-19 - 5.3 * 10-18 m2 s-1 in TiN0.96 between 1100 and 1600 C. The values of the corresponding thermal activation energy are in the range 1 - 2.5 eV; - surface blistering only occurs for ZrC0.92; - whatever the helium implantation dose, helium bubbles are formed near the ion end of range. Nevertheless, for as implanted samples, the bubble size remains less than the lateral resolution of TEM (? 1 nm); - when the annealing temperature increases, the average bubble size increases due to vacancy absorption while the density does not seem to vary. The activation energy corresponding to this mechanism has been evaluated around 0.40 eV; - after a high temperature thermal annealing (T ? 1500 C), the internal pressure of helium bubbles tends to reach the equilibrium value given by the classical law P = 2 ?/r with ? the surface energy and r the bubble radius; - near grain boundaries, the average helium bubble size tends to be larger and their density lower than within the grains; - when the helium implantation fluence decreases from 5 * 1016 to 2.3 * 1015 ions/cm2, helium release is quasi negligible for TiN0.96 even after a 1600 C annealing treatment. Moreover, helium was shown to diffuse on a larger range. (author)

  8. Quantum entanglement in helium

    International Nuclear Information System (INIS)

    We compute the entanglement of the ground state and several singlet and triplet excited states of the helium atom using high-quality, state-of-the-art wavefunctions. The behaviour of the entanglement of the helium eigenstates is similar to that observed in some exactly soluble two-electron systems. In particular, the amount of entanglement exhibited by the eigenstates tends to increase with energy.

  9. Cooling with Superfluid Helium

    OpenAIRE

    Lebrun, P.; Tavian, L.

    2015-01-01

    The technical properties of helium II ('superfluid' helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Ke...

  10. Mechanisms of helium embrittlement

    International Nuclear Information System (INIS)

    In fusion reactor environment, transmutation reactions occur that produce helium when neutrons from the plasma strike the containment first wall. This dissolved helium in the metal together with the neutron induced damage leads to premature, intergranular failure. In an attempt to clarify the role of helium in promoting high temperature intergranular failure, in situ tensile experiments were conducted in a high voltage electron microscope (HVEM) attached to a linear ion accelerator used at 80 keV. Two types of experiments were performed on 14-MeV neutron and helium irradiated 40-?m thick foil stainless steel specimens using a heating quantitative load elongation tensile stage between 25 and 7000C. A graph of cumulative crack length plotted against total specimen elongation exhibits a slope, S, which increases as specimen ductility (reduction of area, ROA) decreases. It was found that ROA2 x S = 0.4 for all cases studied. High temperature helium embrittlement occurs only at slow strain rates. Dislocations dragging helium bubbles to grain boundaries is commonly thought to cause the embrittlement. Specimens tensile tested under dual tensile test temperatures exhibited integranular failure at 7000C and after the tensile test was resumed at 5500C charged to a transgranular failure mode

  11. CHARACTERIZING TRITIUM WASTE USING HELIUM RATIOS

    International Nuclear Information System (INIS)

    When routine sampling revealed greatly elevated tritium levels (3.14 x 105 Bq/L [8.5-million pCi/liter]) in the groundwater near a solid waste landfill at the Hanford Site, an innovative technique was used to assess the extent of the plume. Helium-3/helium-4 ratios, relative to ambient air-in-soil gas samples, were used to identify the tritium source and initially delineate the extent of the groundwater tritium plume. This approach is a modification of a technique developed in the late 1960s to age-date deep ocean water as part of the GEOSECS ocean monitoring program. Poreda, et al. (1) and Schlosser, et al. (2) applied this modified technique to shallow aquifers. A study was also conducted to demonstrate the concept of using helium-3 as a tool to locate vadose zone sources of tritium and tracking groundwater tritium plumes at Hanford (3). Seventy sampling points were installed around the perimeter and along four transects downgradient of the burial ground. Soil gas samples were collected, analyzed for helium isotopes, and helium-3/helium-4 ratios were calculated for these 70 points. The helium ratios indicated a vadose zone source of tritium along the northern edge of the burial ground that is likely the source of tritium in the groundwater. The helium ratios also indicate the groundwater plume is traveling east-northeast from the burial ground and that no up-gradient tritium sources are affecting the burial ground. Based on the helium ratio results, six downgradient groundwater sampling locations were identified to verify the tritium plume extent and groundwater tritium concentrations. The tritium results from the initial groundwater samples confirmed that elevated helium ratios were indicative of tritium contamination in the local groundwater. The measurement of helium isotopes in soil gas provided a rapid and cost- effective technique to define the shape and extent of tritium contamination from the burial ground. Using this soil gas sampling approach, the project team was able to identify areas where elevated tritium existed in groundwater without going to the time and expense of conducting conventional groundwater characterization sampling. The savings from this characterization approach were $1.4 million

  12. High Efficiency Regenerative Helium Compressor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Helium plays several critical rolls in spacecraft propulsion. High pressure helium is commonly used to pressurize propellant fuel tanks. Helium cryocoolers can be...

  13. Asteroseismic estimate of helium abundance of 16 Cyg A, B

    Directory of Open Access Journals (Sweden)

    Verma Kuldeep

    2015-01-01

    Full Text Available The helium ionization zone in a star leaves a characteristic signature on its oscillation frequencies, which can be used to estimate the helium content in the envelope of the star. We use the oscillation frequencies of 16 Cyg A and B, obtained using 2.5 years of Kepler data, to estimate the envelope helium abundance of these stars. We find the envelope helium abundance to lie in the range 0.231–0.251 for 16 Cyg A and 0.218–0.266 for 16 Cyg B.

  14. Helium bubbles in UO2

    International Nuclear Information System (INIS)

    A certain part of helium generated in MOX fuel could form additional bubbles in fuel pellets as a result of the combination of radiation defects and high temperature. In the present study, the helium infusion treatments were conducted at high temperature with highly pressurized helium for both polycrystalline UO2 fragments and hyperstoichiometric single crystal UO2+x particles. Annealing tests for polycrystalline UO2 were followed by the helium infusion treatment to evaluate formation of helium bubble. In case of as helium-infused polycrystalline sample, it was confirmed that helium bubbles were formed after slight oxidative annealing at more than 1573K. On the other hand, the cavity observed in as-helium-infused single crystal sample grew up to form a negative crystal. Formation mechanism of helium bubble and negative crystal were discussed. (author)

  15. System Review of Safety Function Components for the Design of the Cask MCO Helium Purge System - Project A.5 and A.6

    International Nuclear Information System (INIS)

    The design of the Cask/Multiple Canister Overpack (MCO) Helium Purge System (HPS) is assessed for the appropriate designated safety function classification of its components. The purpose of this review is to determine appropriate safety function classifications for the system's components or to identify actions to be taken to reasonably assure that the system/component safety function(s) will be performed as intended. This review also includes consideration that the HPS would perform consistent with its analytical assumptions and basis in HNF-2833, Rev. 0

  16. Helium transfer line installation details.

    CERN Multimedia

    G. Perinic

    2007-01-01

    A particularity of the 32 m long four in one helium transfer line in between the cold box in USC55 and the cavern UX5 is the fact that the transfer line passes through a hole in the crane rail support beam. In order to ensure the alignment of the suspension rail in the interconnecting tunnel with the hole in the rail support as well as the connection points at both ends required precise measurements of the given geometries as well as the installation of a temporary target for the verification of the theoretical predictions.

  17. Helium solubility and bubble growth in metals under high pressure

    International Nuclear Information System (INIS)

    Helium solubility and bubble growth in metals under high pressure polycrystals and single crystals of gold were heated in helium at temperatures between 475 K and 1250 K in a pressure regime of 200 to 2700 bar to measure the solubility of helium in gold. After quenching to room temperature the helium content, measured by mass spectrometry, showed the following properties: 1) A linear dependence of the He solubility on pressure. 2) Thinning of the specimen reduces the helium content by a factor 10 to 100 but does not change the linear pressure dependence. 3) The thermal release of He from thinned polycrystals and single crystals occurs mainly in a single peak at 500 K. 4) The He concentration of the thinned single crystals was lower by a factor of 10 to 50 than that of the thinned polycrystals. 5) The He solubility in single crystals can be described by an enthalpy of solution Hsub(s)sup(f) = 0.85 +- 0.7 eV and a non-configurational entropy of Ssub(s)sup(f) between 0 k and 1 k (k: Boltzmann-constant). In order to measure the pressure dependence of helium bubble growth in nickel polycrystal Ni-foils were ?-implanted to a helium content of 130 appm. The evaluation of the size distribution of the helium bubbles after heat treatments shows 1) The helium content of the observable bubbles - assumed to be in equilibrium - equals the amount of helium implanted into the specimen. 2) The activation energy for the growth of helium bubbles is 1.25 +- 0.3 eV. The comparison of specimen which had been heated at low pressures up to 10 bar with others heated at 2500-2700 bar does not show an unequivocal pressure dependence for helium bubble growth. (orig./IHOE)

  18. Is solid helium a supersolid?

    International Nuclear Information System (INIS)

    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

  19. Helium in Chemically Peculiar Stars

    OpenAIRE

    Leone, F

    1998-01-01

    For the purpose of deriving the helium abundances in chemically peculiar stars, the importance of assuming a correct helium abundance has been investigated for determining the effective temperature and gravity of main sequence B-type stars, making full use of the present capability of reproducing their helium lines. Even if the flux distribution of main sequence B-type stars appears to depend only on the effective temperature for any helium abundance, the effective temp...

  20. Onset Properties of Supersolid Helium

    OpenAIRE

    Yu, Yongle

    2010-01-01

    Supersolid helium has a rather low transition temperature and a small critical velocity, compared with liquid helium. These properties could be explained in terms of helium's spectrum structure and quantum jumps involving large momentum transfer. A grain in the solid helium possess valleys (local minima) in its many-body dispersion curve, and an exchange of large momenta with the grain's surroundings occurs in a jump between a level in one valley and another level in the nei...

  1. 76 FR 12357 - Federal Acquisition Regulation; Information Collection; Acquisition of Helium

    Science.gov (United States)

    2011-03-07

    ... 2011-0079; Sequence 5] Federal Acquisition Regulation; Information Collection; Acquisition of Helium... concerning acquisition of helium. Public comments are particularly invited on: Whether this collection of... (202) 694-8149 or debbie.lague@gov. SUPPLEMENTARY INFORMATION: A. Purpose The Helium Act (Pub. L....

  2. Fine structure of helium and light helium-like ions

    OpenAIRE

    Pachucki, Krzysztof; Yerokhin, Vladimir A.

    2010-01-01

    Calculational results are presented for the fine-structure splitting of the 2^3P state of helium and helium-like ions with the nuclear charge Z up to 10. Theoretical predictions are in agreement with the latest experimental results for the helium fine-structure intervals as well as with the most of the experimental data available for light helium-like ions. Comparing the theoretical value of the 2^3P_0-2^3P_1 interval in helium with the experimental result [T. Zelevinsky et ...

  3. Ab initio potential energy curve for the helium atom pair and thermophysical properties of the dilute helium gas. I. Helium-helium interatomic potential

    OpenAIRE

    Vogel, Eckhard; Bich, Eckard; Hellmann, Robert

    2007-01-01

    Abstract A helium-helium interatomic potential energy curve was determined from quantum-mechanical \\textit{ab initio} calculations. Very large atom-centred basis sets including a newly developed d-aug-cc-pV8Z basis set supplemented with bond functions and \\textit{ab initio} methods up to Full CI were applied. The aug-cc-pV7Z basis set of Gdanitz (\\emph{J. Chem. Phys.}, \\textbf{113}, 5145 (2000)) was modified to be more consistent with the aug-cc-pV5Z and aug-cc-pV6Z basis set...

  4. Calculation of electron-helium scattering

    International Nuclear Information System (INIS)

    We present the Convergent Close-Coupling (CCC) theory for the calculation of electron-helium scattering. We demonstrate its applicability at a range of projectile energies of 1.5 to 500 eV to scattering from the ground state to n ?3 states. Excellent agreement with experiment is obtained with the available differential, integrated, ionization, and total cross sections, as well as with the electron-impact coherence parameters up to and including the 33 D state excitation. Comparison with other theories demonstrates that the CCC theory is the only general reliable method for the calculation of electron helium scattering. (authors). 66 refs., 2 tabs., 24 figs

  5. Dynamics, Defects and Deformation in Solid Helium

    Science.gov (United States)

    Beamish, John

    2011-03-01

    The shear modulus of solid 4 He shows remarkable softening above 100 mK, the same temperature range in which the apparent supersolid disappears in torsional oscillator experiments. We have measured helium's shear modulus and dissipation at frequencies from 0.5 to 8500 Hz. The onset temperature for softening/stiffening is broad, frequency dependent, and is accompanied by a dissipation peak - features typical of a dynamical crossover in a disordered system rather than a true phase transition. This behavior can be qualitatively explained if dislocations are mobile at high temperatures but are pinned by 3 He impurities below 100 mK. To better understand the role of dislocations, we have plastically deformed crystals by rapid thermal quenching and used pressure gradient measurements to study subsequent annealing. In our most recent experiments we have sheared solid helium mechanically and looked at the effect of large deformations on the helium's elastic properties. This work was supported by NSERC.

  6. Cosmological helium production simplified

    International Nuclear Information System (INIS)

    We present a simplified model of helium synthesis in the early universe. The purpose of the model is to explain clearly the physical ideas relevant to the cosmological helium synthesis, in a manner that does not overlay these ideas with complex computer calculations. The model closely follows the standard calculation, except that it neglects the small effect of Fermi-Dirac statistics for the leptons. We also neglect the temperature difference between photons and neutrinos during the period in which neutrons and protons interconvert. These approximations allow us to express the neutron-proton conversion rates in a closed form, which agrees to 10% accuracy or better with the exact rates. Using these analytic expressions for the rates, we reduce the calculation of the neutron-proton ratio as a function of temperature to a simple numerical integral. We also estimate the effect of neutron decay on the helium abundance. Our result for this quantity agrees well with precise computer calculations. We use our semi-analytic formulas to determine how the predicted helium abundance varies with such parameters as the neutron life-time, the baryon to photon ratio, the number of neutrino species, and a possible electron-neutrino chemical potential. 19 refs., 1 fig., 1 tab

  7. Metastable states of antiprotonic helium atoms

    International Nuclear Information System (INIS)

    We discuss the latest theoretical achievements in calculations of energy transitions in the antiprotonic helium He+p-0304; atoms. New variational calculations of the nonrelativistic energies with precision of ?10-10 a.u. and relativistic and QED corrections to the energy levels of m?5 order are presented

  8. The Weakest Link: Bonding between Helium Atoms

    Science.gov (United States)

    Lohr, Lawrence L.; Blinder, S. M.

    2007-01-01

    A highly simplified model for helium dimers that reproduces their essential features without the need for elaborate computation is presented. The He-He potential is predicted to have minimum of 10.9 K at a nuclear separation of 5.61 bohrs.

  9. Lamb shift in singly ionized helium

    International Nuclear Information System (INIS)

    The Lamb shift (n = 2) in 4He+ has been measured in a beam of metastable helium ions by means of the microwave resonance method. Our result is 14.0420(12) GHz which is in good agreement with the theoretical result based on the binding correction of Mohr, 14.0423(5) GHz

  10. Helium Background in the D0 Detector Related to the Photomultiplier Tubes

    Energy Technology Data Exchange (ETDEWEB)

    Rucinski, R.; /Fermilab

    1998-04-09

    Helium is present in the earth's atmosphere at about 5 parts per million. (ref. Technology of liquid helium, NBS monograph 111). The D-Zero detector uses helium for the cryogenic cooling of its superconducting magnet and visible light photon counter (VLPC) electronics chips. In addition, the tevatron accelerator has superconducting magnets that use helium Due to the possibility of leaks or releases of helium from these helium lines and components, the background helium level in the collision hall may exceed the natural level of 5 ppm. This engineering note will quantify the probability and level of helium background in the D-Zero detector. The photomultiplier tubes used in the D-Zero detector are sensitive to an elevated helium atmosphere. This is due to the permeation rate of helium gas through the glass tube, into the vacuum space inside. It is very important for the helium atmosphere surrounding the photomultiplier tubes is known and controlled. If the level of helium in the vacuum tube reaches a level above 5 ppm, then the photomuliplier tube may no longer work as designed. The process is an irreversible one.

  11. Helium effect on mechanical property of fusion reactor structural materials

    International Nuclear Information System (INIS)

    High-energy neutrons produced in fusion reactor core caused helium in the structural materials of fusion reactors, such as blankets. We injected alpha particles accelerated by the cyclotron to the samples of martensite steel (9Cr3WVTaB). Equivalent helium doses injected to the sample is estimated to be up to 300 ppm, which were estimated to be equivalent to helium accumulation after the 1-year reactor operation. Creep tests of the samples were made to investigate helium embrittlement. There were no appreciable changes in the relation between the stresses and the rupture time, the minimum creep rate and the applied stress. Grain boundary effect by helium was not observed in ruptured surfaces. Fatigue tests were made for SUS304 samples, which contain helium up to 150 ppm. After 0.05 Hz cyclic stress tests, it was shown that the fatigue lifetime (cycles to rupture and extension to failure) are 1/5 in 150 ppm helium samples compared with no helium samples. The experimental results suggest martensite steel is promising for structural materials of fusion reactors. (Y. Tanaka)

  12. Nucleation, solvation and boiling of helium excimer clusters

    CERN Document Server

    Luna, Luis G Mendoza; Watkins, Mark J; Bonifaci, Nelly; Aitken, Frederic; von Haeften, Klaus

    2015-01-01

    Helium excimers generated by a corona discharge were investigated in the gas and normal liquid phases of helium as a function of temperature and pressure between 3.8 and 5.0 K and 0.2 and 5.6 bar. Intense fluorescence in the visible region showed the rotationally resolved $d^3\\Sigma_u^+ \\rightarrow b^3\\Pi_g$ transition of He$_2^*$. With increasing pressure, the rotational lines merged into single features. The observed pressure dependence of linewidths, shapes and lineshifts established phases of coexistence and separation of excimer-helium mixtures, providing detailed insight into nucleation, solvation and boiling of He$_2^*$-He$_n$ clusters.

  13. Design of the Helium Purifier for IHEP-ADS Helium Purification System

    CERN Document Server

    Jianqin, Zhang; Zhuo, Zhang; Rui, Ge

    2015-01-01

    Helium Purification System is an important sub-system in the Accelerator Driven Subcritical System of the Institute of High Energy Physics(IHEP ADS). The purifier is designed to work at the temperature of 77K. The purifier will work in a flow rate of 5g/s at 20MPa in continuous operation of 12 hours. The oil and moisture are removed by coalescing filters and a dryer, while nitrogen and oxygen are condensed by a phase separator and then adsorbed in several activated carbon adsorption cylinders. After purification, the purified helium has an impurity content of less than 5ppm.

  14. Feasibility of lunar Helium-3 mining

    Science.gov (United States)

    Kleinschneider, Andreas; Van Overstraeten, Dmitry; Van der Reijnst, Roy; Van Hoorn, Niels; Lamers, Marvin; Hubert, Laurent; Dijk, Bert; Blangé, Joey; Hogeveen, Joel; De Boer, Lennaert; Noomen, Ron

    With fossil fuels running out and global energy demand increasing, the need for alternative energy sources is apparent. Nuclear fusion using Helium-3 may be a solution. Helium-3 is a rare isotope on Earth, but it is abundant on the Moon. Throughout the space community lunar Helium-3 is often cited as a major reason to return to the Moon. Despite the potential of lunar Helium-3 mining, little research has been conducted on a full end-to-end mission. This abstract presents the results of a feasibility study conducted by students from Delft University of Technology. The goal of the study was to assess whether a continuous end-to-end mission to mine Helium-3 on the Moon and return it to Earth is a viable option for the future energy market. The set requirements for the representative end-to-end mission were to provide 10% of the global energy demand in the year 2040. The mission elements have been selected with multiple trade-offs among both conservative and novel concepts. A mission architecture with multiple decoupled elements for each transportation segment (LEO, transfer, lunar surface) was found to be the best option. It was found that the most critical element is the lunar mining operation itself. To supply 10% of the global energy demand in 2040, 200 tons of Helium-3 would be required per year. The resulting regolith mining rate would be 630 tons per second, based on an optimistic concentration of 20 ppb Helium-3 in lunar regolith. Between 1,700 to 2,000 Helium-3 mining vehicles would be required, if using University of Wisconsin’s Mark III miner. The required heating power, if mining both day and night, would add up to 39 GW. The resulting power system mass for the lunar operations would be in the order of 60,000 to 200,000 tons. A fleet of three lunar ascent/descent vehicles and 22 continuous-thrust vehicles for orbit transfer would be required. The costs of the mission elements have been spread out over expected lifetimes. The resulting profits from Helium-3 fusion were calculated using a predicted minimum energy price in 2040 of 30.4 Euro/MWh. Annual costs are between 427.7 to 1,347.9 billion Euro, with annual expected profit ranging from -724.0 to 260.0 billion Euro. Due to the large scale of the mission, it has also been evaluated for providing 0.1% and 1% of the global energy demand in 2040. For 1%, the annual costs are 45.6 to 140.3 billion Euro and the expected annual profits are -78.0 to 23.1 billion Euro. For 0.1%, the annual costs are 7.7 to 20.5 billion Euro. The annual expected profits are -14.3 to -0.8 billion Euro. Feasibility has been addressed in three aspects. Technically, the mission is extremely challenging and complex. However, most required technologies exist or could be developed within a reasonable time span. From a political and legal perspective, the current international treaties hardly provide any framework for a lunar mining operation. Financially, the mission only produces a net profit in the best case, and only for medium- to large-scale operations, which require a very large initial investment. To make lunar Helium-3 usage possible, further research should concentrate on the mining operation and costs of fusion plants, as their impact by far outranks all other mission elements. Different transportation concepts may be investigated nevertheless. Many - not only technical - challenges concerning Helium-3 mining are still to be addressed. Although only a starting point for further investigations, this study shows that, despite popular claims, lunar Helium-3 is unsuitable to provide a significant percentage of the global energy demand in 2040.

  15. Antiprotonic helium atomcules

    Directory of Open Access Journals (Sweden)

    Sauge Sébastien

    2012-10-01

    Full Text Available About 3% of antiprotons ( stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of on metastable bound states in He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spectroscopy – a near-circular quasi-classical Rydberg atom with l ~ n – 1 ~ 37 or a special diatomic molecule with a negatively charged nucleus in high rotational state with J = l – the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.

  16. Applications of Groundwater Helium

    Science.gov (United States)

    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. A reexamination of quenches in Helium 4 and Helium 3

    OpenAIRE

    Karra, G.; R. J. Rivers

    1998-01-01

    In the light of recent difficulties in observing vortices in quenches of liquid helium 4 to its superfluid state we re-examine the Zurek scenario for their production. We argue that experiments in helium 4 are unlikely to produce true vortices in the numbers originally anticipated, if at all, because of the wide Ginzberg regime and the slowness of the mechanical quenches. On the other hand, the observed production of unambiguous vortices in neutron-bombarded helium 3, with i...

  18. Water-helium condensate (watergel) in liquid helium

    International Nuclear Information System (INIS)

    The water-helium condensate (watergel) is formed in He-II cooled below 1.5 K as a result of condensation of the gas flow of 4He with the water impurity at the surface of superfluid liquid. The experimental results indicate that the shape of the gel samples formed below the liquid surface depends strongly on geometry of experimental cell: from an oval iceberg in a narrow glass tube (9 mm in inner diameter) to vertically arrange clouds in a wide cell (30 mm in diameter). From our estimations it follows that the total content of water in bulk of the gel samples is less than 1020 molecules/cm3 and that their density is a few percent higher than the density of surrounding liquid only

  19. Cavitation pressure in liquid helium

    OpenAIRE

    Caupin, Frederic; Balibar, Sebastien

    2001-01-01

    Recent experiments have suggested that, at low enough temperature, the homogeneous nucleation of bubbles occurs in liquid helium near the calculated spinodal limit. This was done in pure superfluid helium 4 and in pure normal liquid helium 3. However, in such experiments, where the negative pressure is produced by focusing an acoustic wave in the bulk liquid, the local amplitude of the instantaneous pressure or density is not directly measurable. In this article, we present ...

  20. Helium ion implanted waveguide lasers

    International Nuclear Information System (INIS)

    High energy ion implantation may be used to modify the refractive index of surfaces of insulators to form optical waveguides and waveguide lasers. Bombardment with MeV helium ions normally reduces the crystalline indices at the end of the ion range. This low index region provides an optical barrier and so defines a waveguide. The method has been demonstrated in more than 30 crystalline targets. Possible factors which influence the refractive index profile are discussed. A successful approach to form waveguide lasers is to use the implantation damage method to construct a waveguide in a predoped crystal. After annealing the optical losses are reduced and planar waveguide lasers have so far been demonstrated in Nd doped YAG, YAP, LiNbO3, Gd3Ga5O12 and Bi4Ge3O12. (orig.)

  1. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Science.gov (United States)

    2010-10-01

    ... 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.

    Science.gov (United States)

    2010-10-01

    ...Sources for Helium and Helium Usage Data. 52.208-8 Section...Sources for Helium and Helium Usage Data. As prescribed in 8...Sources for Helium and Helium Usage Data (APR 2002) (a) Definitions...Suppliers available via the Internet at...

  3. Study of expansion of solid Helium-4 into vacuum

    OpenAIRE

    Käsz, Manuel

    2006-01-01

    This work gives a detailed introduction into a fully new experimental method to investigate the quantum crystal behavior of solid Helium-4. It has been found that a fascinating new effect occurs in the expansion of solid Helium-4 into a vacuum through pinhole orifices with diameters between 1 and 5 µm. It is observed that the beam flux intensity shows a periodic behavior for source conditions corresponding to the solid phase of Helium-4. The period is in the range of seconds up to minutes. It...

  4. Cosmogenic helium and neon extracted by crushing: A technique for discriminating between mantle and cosmogenic helium

    OpenAIRE

    Moreira, Manuel; Madureira, Pedro

    2005-01-01

    The helium and neon isotopic compositions of olivines coming from a 11Ma old xenolith sampled at Mt. Hampton (West Antarctica) were analyzed by crushing and heating. The 4He/3He isotopic ratio obtained by crushing varies between 1340 and 6300 (R/Ra between 115 and 539) with 4He content around 3-5 10-10 ccSTP/g confirming that cosmogenic helium can be extracted by crushing [Scarsi, 2000; Yocochi et al., 2004]. The neon also shows a clear cosmogenic origin (20Ne/22Ne down to 7.7 and 21Ne/22Ne>0...

  5. Performance of an efficient Helium Circulation System on a MEG

    International Nuclear Information System (INIS)

    We report a Helium Circulation System (HCS) that re-liquefies all the evaporating helium gas, consumes far less power and has extremely lower magnetic noise compared with conventional systems. It collects warm helium gas about 300 K, cools it to about 40K and returns it to the neck tube of the Dewar to keep it cold. It also collects helium gas just above the liquid helium surface while it is still cold, re-liquefies and returns it to the Dewar. A special transfer tube (TT) about 2 m length with 7 multi-concentric pipes was developed to allow the dual helium streams. It separates the HCS with a MEG to reduce magnetic noise. A refiner to collect the contaminating gases such as oxygen and nitrogen effectively by freezing the gases is developed. It has an electric heater to remove the frozen contamination in the form of gases into the air. A gas flow controller is also developed, which automatically control the heater to cleanup the contamination. The developed TT has very low heat inflow less than 0.1W/m to the liquid helium ensuring the efficient operation. The HCS can re-liquefy up to 35.5 1/D of liquid helium from the evaporated helium gas using two 1.5W-4.2K GM cryocoolers (SRDK-415D, Sumitomo Heavy Industries, Ltd.). It has been confirmed that the HCS could be used with the real MEG system without any noise problem for over one year. The maintenance cost (electricity charges and cryocoolers maintenance fee) of the MEG has reduced to be less than 1/10 of the previous cost.

  6. Performance of an efficient Helium Circulation System on a MEG

    Science.gov (United States)

    Takeda, T.; Okamoto, M.; Atsuda, K.; Katagiri, K.

    2009-02-01

    We report a Helium Circulation System (HCS) that re-liquefies all the evaporating helium gas, consumes far less power and has extremely lower magnetic noise compared with conventional systems. It collects warm helium gas about 300 K, cools it to about 40K and returns it to the neck tube of the Dewar to keep it cold. It also collects helium gas just above the liquid helium surface while it is still cold, re-liquefies and returns it to the Dewar. A special transfer tube (TT) about 2 m length with 7 multi-concentric pipes was developed to allow the dual helium streams. It separates the HCS with a MEG to reduce magnetic noise. A refiner to collect the contaminating gases such as oxygen and nitrogen effectively by freezing the gases is developed. It has an electric heater to remove the frozen contamination in the form of gases into the air. A gas flow controller is also developed, which automatically control the heater to cleanup the contamination. The developed TT has very low heat inflow less than 0.1W/m to the liquid helium ensuring the efficient operation. The HCS can re-liquefy up to 35.5 1/D of liquid helium from the evaporated helium gas using two 1.5W@4.2K GM cryocoolers (SRDK-415D, Sumitomo Heavy Industries, Ltd.). It has been confirmed that the HCS could be used with the real MEG system without any noise problem for over one year. The maintenance cost (electricity charges and cryocoolers maintenance fee) of the MEG has reduced to be less than 1/10 of the previous cost.

  7. Simulation of liquid helium

    International Nuclear Information System (INIS)

    The author discusses simulation methods for quantum mechanical systems at finite temperatures. Recently it has been shown that static properties of some quantum systems can be obtained by simulation in a straightforward manner using path integrals, albeit with an order of magnitude more computing effort needed than for the corresponding classical systems. Some dynamical information can be gleaned from these simulations as will be discussed below. But this is very limited - there is no quantum version of the molecular dynamics method. The path integral method is illustrated by discussing the application to liquid helium. 12 refs., 8 figs

  8. The Hall D solenoid helium refrigeration system at JLab

    Science.gov (United States)

    Laverdure, N.; Creel, J.; Dixon, K.; Ganni, V.; Martin, F.; Norton, R.; Radovic, S.

    2014-01-01

    Hall D, the new Jefferson Lab experimental facility built for the 12GeV upgrade, features a LASS 1.85 m bore solenoid magnet supported by a 4.5 K helium refrigerator system. This system consists of a CTI 2800 4.5 K refrigerator cold box, three 150 hp screw compressors, helium gas management and storage, and liquid helium and nitrogen storage for stand-alone operation. The magnet interfaces with the cryo refrigeration system through an LN2-shielded distribution box and transfer line system, both designed and fabricated by JLab. The distribution box uses a thermo siphon design to respectively cool four magnet coils and shields with liquid helium and nitrogen. We describe the salient design features of the cryo system and discuss our recent commissioning experience.

  9. CERN Technical Training 2002: Learning for the LHC! HEREF-2002 : HELIUM REFRIGERATION TECHNIQUES

    CERN Multimedia

    Davide Vitè

    2002-01-01

    Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2002 is a new course, in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2002 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2002 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (5 mornings and 2 afternoons), 21-25 October, 2002. Estimated cost: 300.- CHF Language: Bilingual English-French. The course support will be in English, the ...

  10. CERN Technical Training 2002: Learning for the LHC ! HeREF-2002 : Helium Refrigeration Techniques

    CERN Multimedia

    Davide Vitè

    2002-01-01

    Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2002 is a new course, in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2002 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2002 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (5 mornings and 2 afternoons), 21-25 October 2002. Estimated cost: 300.- CHF Language: Bilingual English-French. The course support will be in English, the...

  11. Quantum cavitation in liquid helium

    OpenAIRE

    Guilleumas, Montserrat; Barranco Gómez, Manuel; Jezek, Dora M.; Lombard, Roland J.; Pi Pericay, Martí

    1996-01-01

    Using a functional-integral approach, we have determined the temperature below which cavitation in liquid helium is driven by thermally assisted quantum tunneling. For both helium isotopes, we have obtained the crossover temperature in the whole range of allowed negative p essures. Our results are compatible with recent experimental results on 4He.

  12. Flow and Supersolidity in Helium

    Science.gov (United States)

    Day, James; Beamish, John

    2007-09-01

    Recent torsional oscillator measurements showed evidence of non-classical rotational inertia in solid helium at temperatures below 200 mK and generated a great deal of interest in a possible supersolid state. The nature and properties of such a state are still unclear, although experiments involving 3He impurities and crystal annealing may provide clues. It would be very interesting to know whether supersolids share any of the other unusual properties of superfluids: superleaks, persistent currents, second sound and quantized vortices. We have studied the response of solid helium to pressure differences, in order to look for unusual flow properties that might be associated with supersolidity. Our measurements involved both helium confined in the nanometer pores of Vycor glass and bulk solid helium, at temperatures as low as 30 mK. Near melting, solid helium flows very easily but we did not see any evidence of superflow at low temperatures. If helium does become a supersolid at low temperatures, then its response to pressure gradients must be very different from that of liquid helium. We describe these and other experiments and discuss the role that defects may play in the low temperature behavior of solid helium.

  13. Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor under IFE Conditions

    International Nuclear Information System (INIS)

    The High Average Power Laser (HAPL) program is a coordinated effort to develop Laser Inertial Fusion Energy. The implosion of the D-T target produces a spectrum of neutrons, X-rays, and charged particles, which arrive at the first wall (FW) at different times within about 2.5 ?s at a frequency of 5 to 10 Hz. Helium is one of several high-energy charged particle constituents impinging on the candidate tungsten armored low activation ferritic steel First Wall. The spread of the implanted debris and burn helium energies results in a unique space-time dependent implantation profile that spans about 10 ?m in tungsten. Co-implantation of X-rays and other ions results in spatially dependent damage profiles and rapid space-time dependent temperature spikes and gradients. The rate of helium transport and helium bubble formation will vary significantly throughout the implanted region. Furthermore, helium will also be transported via the migration of helium bubbles and non-equilibrium helium-vacancy clusters. The HEROS code was developed at UCLA to model the spatial and time-dependent helium bubble nucleation, growth, coalescence, and migration under transient damage rates and transient temperature gradients. The HEROS code is based on kinetic rate theory, which includes clustering of helium and vacancies, helium mobility, helium-vacancy cluster stability, cavity nucleation and growth and other microstructural features such as interstitial loop evolution, grain boundaries, and precipitates. The HEROS code is based on space-time discretization of reaction-diffusion type equations to account for migration of mobile species between neighboring bins as single atoms, clusters, or bubbles. HAPL chamber FW implantation conditions are used to model helium bubble evolution in the implanted tungsten. Helium recycling rate predictions are compared with experimental results of helium ion implantation experiments. (author)

  14. Correlation of Helium Solubility in Liquid Nitrogen

    Science.gov (United States)

    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.

  15. Central helium density measurements in PLT

    International Nuclear Information System (INIS)

    The central helium density in PLT has been deduced from measurements of the ratio of d-3He to d-d fusion reactions during deuterium neutral beam injection. The inward transport time for 3He puffed at the edge plasma was 10 ? 30 msec. The decay time of the central 3He density increased with electron density, varying from 0.3 sec to greater than 1.0 sec over the density range of (1 ? 5) x 1013 cm-3

  16. Neutral beam line pump with helium cryotrapping capability

    International Nuclear Information System (INIS)

    A neutral beamline cryopump has been developed that will cryocondense hydrogen and cryotrap helium either separately or simultaneously. The pump will be part of the apparatus for a direct conversion experiment to be installed on the LBL neutral beam test stand. The location of the pump between the direct converter electrodes and the neutral beam dump will maintain a sufficiently low pressure for efficient collection of the energetic beam ions. Further, the helium cryotrapping capability will permit the use of helium beams with the advantage of a single ion species in direct converter development. The specific pumping speed for hydrogen is 10.5 liters/sec/cm2 at 6 x 10-5 torr. The maximum specific pumping speed for helium (cryotrapped at an argon to helium flow ratio of 30:1) is 3.52 liters/sec/cm2 at 8 x 10-6 torr. The area of the chevron baffle is 1.5 m2 providing a maximum through put of 16 torr-liters/sec of hydrogen and 4 torr-liters/sec for helium both at 1 x 10-4 torr. The design and development details and the operational characteristics will be discussed

  17. New experimental device for VHTR structural material testing and helium coolant chemistry investigation - High Temperature Helium Loop in NRI Rez

    Energy Technology Data Exchange (ETDEWEB)

    Berka, Jan, E-mail: bej@cvrez.cz [Research Centre Rez, Ltd, Husinec-Rez 130, 25068 Rez (Czech Republic); Institute of Chemical Technology Prague, Technicka 1905, 16628 Prague 6 (Czech Republic); Matecha, Josef, E-mail: josef.matecha@ujv.cz [Nuclear Research Institute Rez plc., Husinec-Rez 130, 25068 Rez (Czech Republic); Cerny, Michal [Institute of Chemical Technology Prague, Technicka 1905, 16628 Prague 6 (Czech Republic); Viden, Ivan, E-mail: ivan.viden@vscht.cz [Institute of Chemical Technology Prague, Technicka 1905, 16628 Prague 6 (Czech Republic); Sus, Frantisek [Research Centre Rez, Ltd, Husinec-Rez 130, 25068 Rez (Czech Republic); Nuclear Research Institute Rez plc., Husinec-Rez 130, 25068 Rez (Czech Republic); Hajek, Petr [Nuclear Research Institute Rez plc., Husinec-Rez 130, 25068 Rez (Czech Republic)

    2012-10-15

    The High Temperature Helium Loop (HTHL) is an experimental device for simulation of VHTR helium coolant conditions. The purpose of the HTHL is structural materials testing and helium coolant chemistry investigation. In the HTHL pure helium will be used as working medium and its main physical parameters are 7 MPa, max. temperature in the test section 900 Degree-Sign C and flow rate 37.8 kg/h. The HTHL consists of an active channel, the helium purification system, the system of impurities dosage (e.g. CO, CO{sub 2}, H{sub 2}, H{sub 2}O, O{sub 2}, N{sub 2}, and CH{sub 4}) and the helium chemistry monitoring system (sampling and on-line analysis and determination of impurities in the helium flow). The active channel is planned to be placed into the core of the experimental reactor LVR-15 which will serve as a neutron flux source (max. 2.5 Multiplication-Sign 10{sup 18} n/m{sup 2} s for fast neutrons). The HTHL is now under construction. Some of its main parts are finished, some are still being produced (active channel internals, etc.), some should be improved to work correctly (the helium circulatory compressor); certain sub-systems are planned to be integrated to the loop (systems for the determination of moisture and other impurities in helium, etc.). The start of the HTHL operation is expected during 2011 and the integration of the active channel into the LVR-15 core during 2012.

  18. The influence of electrostatic fields on films of liquid helium

    International Nuclear Information System (INIS)

    Prompted by the recent striking experimental results reported by Babkin and Hakonen that appeared to show that liquid helium-II does not wet magnesium fluoride, the authors have examined the effects that an inhomogeneous electrostatic field has on thin films of liquid helium at temperatures below 0.5 K. Their model includes the influence of gravity, surface tension, the electric field and the van der Waals interaction between the helium and its supporting substrate. The authors show that an inhomogeneous charge on the substrate can produce effects that mimic the surface profiles between wetted and non-wetted areas. The calculations also indicate that some special precautions may be necessary when studying films of liquid or solid helium on insulators

  19. Photoionization of helium dimers

    International Nuclear Information System (INIS)

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  20. Exotic helium molecules

    International Nuclear Information System (INIS)

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range 4He2(23S1-23P0) molecule, or a 4He2(23S1-23S1) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 ± 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range 4He2(23S1-23S1) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime ? = (1.4 ± 0.3) ?s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  1. Cycle design for the ISABELLE helium refrigerator

    International Nuclear Information System (INIS)

    The superconducting magnets for the ISABELLE storage ring/accelerator are designed to be operated at 3.80K using a forced-flow supercritical helium cooling system. The ISABELLE refrigerator has been designed subject to these special requirements. The design output is 13.65 KW of refrigeration below 4.20K (for cooling the magnet and distribution system), 55 KW at 550K (to cool heat shields for the whole system) and 100 g/s of liquefaction (for magnet power leads cooling). The system incorporates a subcooler section that produces liquid helium at 5.3 atm and 2.6 K and circulates it through the loads, and a Claude-type main refrigerator section. The main refrigerator section has five stages of cooling, with four of them below liquid nitrogen temperature. Liquid nitrogen precooling is not used. With 60% isothermal compressors the efficiency of the refrigerator system will be about 26% of Carnot

  2. Measurement of helium production cross sections of iron for d-T neutrons by helium accumulation method

    Energy Technology Data Exchange (ETDEWEB)

    Takao, Yoshiyuki; Kanda, Yukinori; Nagae, Koji; Fujimoto, Toshihiro [Kyushu Univ., Fukuoka (Japan); Ikeda, Yujiro

    1997-03-01

    Helium production cross sections of Iron were measured by helium accumulation method for neutron energies from 13.5 to 14.9 MeV. Iron samples were irradiated with FNS, an intense d-T neutron source of JAERI. As the neutron energy varies according to the emission angle at the neutron source, the samples were set around the neutron source and were irradiated by neutrons of different energy depending on each sample position. The amount of helium produced in a sample was measured by Helium Atoms Measurement System at Kyushu University. The results of this work are in good agreement with other experimental data in the literature and also compared with the evaluated values in JENDL-3. (author)

  3. Electronic properties of physisorbed helium

    International Nuclear Information System (INIS)

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  4. Electronic properties of physisorbed helium

    Energy Technology Data Exchange (ETDEWEB)

    Kossler, Sarah

    2011-09-22

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  5. Low temperature uses of helium

    Science.gov (United States)

    Brown, G. V.

    1970-01-01

    Helium is used for purging and pressurizing cryogenic rocket propellants, welding, atmosphere control, leak detection, and refrigeration. It provides the lowest possible liquid-bath temperature and produces superconductivity in certain materials. Its superfluid effects are used in superconducting magnets.

  6. Helium doped hydrogen or deuterium beam as cost effective and simple tool for plasma spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Falter, H.D. E-mail: falter@iap.tuwien.ac.at; Proschek, M.; Menhart, S.; Aumayr, F.; Winter, H.P.; Ciric, D.; Dines, A.; Godden, D.; Jones, T.T.C

    2001-10-01

    Energetic neutral particles from neutral hydrogenic beam heating systems are widely used for active spectroscopic measurements of key plasma parameters in fusion experiments. Helium beams are used in dedicated diagnostic beamlines offering deeper penetration and resonant double charge exchange with alpha particles. Neutral beam systems using pure helium either require specialised helium gas pumping with a pumping speed in excess of 1000 m{sup 3}/h or are restricted to short pulses (normally less than 1 s). A doped hydrogen/helium beam combines the requirements for plasma heating and diagnostics without the need for sophisticated helium pumping. A small flow of helium gas is injected into the plasma source for the time helium particles are required. The helium current is typically 10% of the total extracted current. The reduction in heating power of the doped beam can be kept below 5%. Doped deuterium/helium beams have been successfully tested and routinely used at JET. HeI beam emission spectra obtained with a doped deuterium/helium beam offer sufficiently strong visible lines for spectroscopic applications.

  7. Looking back at superfluid helium

    OpenAIRE

    Balibar, Sebastien

    2003-01-01

    A few years after the discovery of Bose Einstein condensation in several gases, it is interesting to look back at some properties of superfluid helium. After a short historical review, I comment shortly on boiling and evaporation, then on the role of rotons and vortices in the existence of a critical velocity in superfluid helium. I finally discuss the existence of a condensate in a liquid with strong interactions, and the pressure variation of its superfluid transition temp...

  8. India's first indigenously developed helium liquefier

    International Nuclear Information System (INIS)

    We report the first indigenous development of helium liquefier at Cryo-engineering and Cryo-module Development Section at Raja Ramanna Centre for Advanced Technology, Indore. This system is based on reciprocating type expansion engine and uses cross counter flow type heat exchangers, based on high finned density copper tubes. The cyclic compressor is a four stage air cooled reciprocating type compressor. Its oil removal system is also designed and developed indigenously. Helium gas from commercial cylinders, as well as that recovered from user experiments, is used for liquefying, after passing it through a liquid nitrogen based gas purifier, made locally. First successful liquefaction in this system was achieved on August 14, 2010 at 4.35 K, 1140 mbara, approx. 2.5 psig. This was for the first time in the country using a indigenously developed system. More than 150 liters of liquid helium was collected during its maiden trial itself, while operating for more than 25 hours continuously. Details of the liquefier system and the performance of different components are presented in this paper. (author)

  9. Helium transport scaling law studies

    International Nuclear Information System (INIS)

    Impurity behavior within the tokamak fusion plasma will be a main concern for the future tokamak operation such as ITER. Thermalized alpha particles, i.e., helium ''ashes'' constitute a key impurity within the plasma core. The helium ash accumulation within the tokamak plasma not only dilutes the fusion fuel, but also enhances the radiation energy loss. Eventually, these effects can prevent the fusion ignition and degrade the fusion output power even after ignition. Great progress has been made in determining the transport coefficients D(r) and V(r) with helium puffing and simulation techniques. Obviously, those results are only valid for a specific machine under certain plasma conditions. The extrapolation to other devices still remains a problem. Physically, alpha particle transport is determined by the local plasma conditions. Therefore, the D and V should be a function of the plasma parameters. In our research, we assume that the helium transport scaling law has the form of power law. By using the experiment data from helium puffing in L-mode deuterium plasma on TFRR, the scaling laws of D and V are obtained with the least square analysis. Also, the significance of helium transport scaling law to the design is discussed

  10. Asteroseismic estimate of helium abundance of a solar analog binary system

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Kuldeep; Antia, H. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Faria, João P.; Monteiro, Mário J. P. F. G. [Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Basu, Sarbani [Astronomy Department, Yale University, P. O. Box 208101, New Haven, CT 065208101 (United States); Mazumdar, Anwesh [Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088 (India); Appourchaux, Thierry [Institut d' Astrophysique Spatiale, Université Paris XI-CNRS (UMR8617), Batiment 121, F-91405 Orsay Cedex (France); Chaplin, William J. [School of Physics and Astronomy, University of Birmingham, B15 2TT (United Kingdom); García, Rafael A. [Laboratoire AIM, CEA/DSM, CNRS, Université Paris Diderot, IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Metcalfe, Travis S. [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark)

    2014-08-01

    16 Cyg A and B are among the brightest stars observed by Kepler. What makes these stars more interesting is that they are solar analogs. 16 Cyg A and B exhibit solar-like oscillations. In this work we use oscillation frequencies obtained using 2.5 yr of Kepler data to determine the current helium abundance of these stars. For this we use the fact that the helium ionization zone leaves a signature on the oscillation frequencies and that this signature can be calibrated to determine the helium abundance of that layer. By calibrating the signature of the helium ionization zone against models of known helium abundance, the helium abundance in the envelope of 16 Cyg A is found to lie in the range of 0.231 to 0.251 and that of 16 Cyg B lies in the range of 0.218 to 0.266.

  11. Measurement of helium generated in V-B alloys irradiated in FFTF/MOTA

    International Nuclear Information System (INIS)

    V-B and V-5Cr-B alloys have been irradiated in FFTF to assess the impact of helium generation rate on microstructural evolution of vanadium-base alloys. Using this method it is somewhat difficult to separate the various effects of the original boron as well as the lithium and helium products of the 10B (n, ?) reaction. Post-irradiation measurements of helium concentrations have been completed for two sets of V-B alloys, one irradiated in-core and one below core. It appears that the boron doping technique used to produce the various alloys was reasonably successful in reaching the desired helium/dpa variations

  12. Performance of the Helium Circulation System on a Commercialized MEG

    International Nuclear Information System (INIS)

    We report the performance of a helium circulation system (HCS) mounted on a MEG (Magnetoencephalography) at Nagoya University, Japan. This instrument is the first commercialized version of an HCS. The HCS collects warm helium gas at approximately 300 K and then cools it to approximately 40 K. The gas is returned to the neck tube of a Dewar of the MEG to keep it cold. It also collects helium gas in the region just above the liquid helium surface while it is still cold, re-liquefies the gas and returns it to the Dewar. A special transfer tube (TT) of approximately 3 m length was developed to allow for dual helium streams. This tube separates the HCS using a MEG to reduce magnetic noise. A refiner was incorporated to effectively collect contaminating gases by freezing them. The refiner was equipped with an electric heater to remove the frozen contaminants as gases into the air. A gas flow controller was also developed, which automatically controlled the heater and electric valves to clean up contamination. The developed TT exhibited a very low heat inflow of less than 0.1 W/m to the liquid helium, ensuring efficient operation. The insert tube diameter, which was 1.5 in. was reduced to a standard 0.5 in. size. This dimensional change enabled the HCS to mount onto any commercialized MEG without any modifications to the MEG. The HCS can increase liquid helium in the Dewar by at least 3 liters/Day using two GM cryocoolers (SRDK-415D, Sumitomo Heavy Industries, Ltd.). The noise levels were virtually the same as before this installation.

  13. Performance of the Helium Circulation System on a Commercialized MEG

    Science.gov (United States)

    T, Takeda; M, Okamoto; T, Miyazaki; K, Katagiri

    2012-12-01

    We report the performance of a helium circulation system (HCS) mounted on a MEG (Magnetoencephalography) at Nagoya University, Japan. This instrument is the first commercialized version of an HCS. The HCS collects warm helium gas at approximately 300 K and then cools it to approximately 40 K. The gas is returned to the neck tube of a Dewar of the MEG to keep it cold. It also collects helium gas in the region just above the liquid helium surface while it is still cold, re-liquefies the gas and returns it to the Dewar. A special transfer tube (TT) of approximately 3 m length was developed to allow for dual helium streams. This tube separates the HCS using a MEG to reduce magnetic noise. A refiner was incorporated to effectively collect contaminating gases by freezing them. The refiner was equipped with an electric heater to remove the frozen contaminants as gases into the air. A gas flow controller was also developed, which automatically controlled the heater and electric valves to clean up contamination. The developed TT exhibited a very low heat inflow of less than 0.1 W/m to the liquid helium, ensuring efficient operation. The insert tube diameter, which was 1.5 in. was reduced to a standard 0.5 in. size. This dimensional change enabled the HCS to mount onto any commercialized MEG without any modifications to the MEG. The HCS can increase liquid helium in the Dewar by at least 3 liters/Day using two GM cryocoolers (SRDK-415D, Sumitomo Heavy Industries, Ltd.). The noise levels were virtually the same as before this installation.

  14. Helium generation and release in MOX fuels

    International Nuclear Information System (INIS)

    Measurement of the retained helium in MOX fuel matrices was carried out. Helium generation under irradiation was estimated by adding the released helium to the retained value. The measured helium generation agreed with the calculated one, when modified by adding ternary fission yield. Helium pressure increase in a high burn-up MOX fuel rod can reach 30% or more of the FP gas pressure. This should contribute to higher internal rod pressure. The impact of generated helium on fuel performance requires further investigation. (author)

  15. Cavity morphology in a Ni based superalloy under heavy ion irradiation with hot pre-injected helium. II

    Science.gov (United States)

    Zhang, He; Yao, Zhongwen; Daymond, Mark R.; Kirk, Marquis A.

    2014-03-01

    In the current investigation, TEM in-situ heavy ion (1 MeV Kr2+) irradiation with helium pre-injected at elevated temperature (400 °C) was conducted to simulate in-reactor neutron irradiation induced damage in CANDU spacer material Inconel X-750, in an effort to understand the effects of helium on irradiation induced cavity microstructures. Three different quantities of helium, 400 appm, 1000 appm, and 5000 appm, were pre-injected directly into TEM foils at 400 °C. The samples containing helium were then irradiated in-situ with 1 MeV Kr2+ at 400 °C to a final dose of 5.4 dpa (displacement per atom). Cavities were formed from the helium injection solely and the cavity density and size increased with increasing helium dosage. In contrast to previous heavy ion irradiations with cold pre-injected helium, heterogeneous nucleation of cavities was observed. During the ensuing heavy ion irradiation, dynamical observation showed noticeable size increase in cavities which nucleated close to the grain boundaries. A "bubble-void" transformation was observed after Kr2+ irradiation to high dose (5.4 dpa) in samples containing 1000 appm and 5000 appm helium. Cavity distribution was found to be consistent with in-reactor neutron irradiation induced cavity microstructures. This implies that the distribution of helium is greatly dependent on the injection temperature, and helium pre-injection at high temperature is preferred for simulating the migration of the transmutation produced helium.

  16. Cavity morphology in a Ni based superalloy under heavy ion irradiation with hot pre-injected helium. II

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, He; Yao, Zhongwen, E-mail: yaoz@me.queensu.ca; Daymond, Mark R. [Department of Mechanical and Materials Engineering, Queen' s University Kingston, Ontario K7L 3N6 (Canada); Kirk, Marquis A. [Material Science Division, Argonne National Laboratory Argonne, Illinois 60439 (United States)

    2014-03-14

    In the current investigation, TEM in-situ heavy ion (1?MeV Kr{sup 2+}) irradiation with helium pre-injected at elevated temperature (400?°C) was conducted to simulate in-reactor neutron irradiation induced damage in CANDU spacer material Inconel X-750, in an effort to understand the effects of helium on irradiation induced cavity microstructures. Three different quantities of helium, 400 appm, 1000 appm, and 5000 appm, were pre-injected directly into TEM foils at 400?°C. The samples containing helium were then irradiated in-situ with 1?MeV Kr{sup 2+} at 400?°C to a final dose of 5.4 dpa (displacement per atom). Cavities were formed from the helium injection solely and the cavity density and size increased with increasing helium dosage. In contrast to previous heavy ion irradiations with cold pre-injected helium, heterogeneous nucleation of cavities was observed. During the ensuing heavy ion irradiation, dynamical observation showed noticeable size increase in cavities which nucleated close to the grain boundaries. A “bubble-void” transformation was observed after Kr{sup 2+} irradiation to high dose (5.4?dpa) in samples containing 1000 appm and 5000 appm helium. Cavity distribution was found to be consistent with in-reactor neutron irradiation induced cavity microstructures. This implies that the distribution of helium is greatly dependent on the injection temperature, and helium pre-injection at high temperature is preferred for simulating the migration of the transmutation produced helium.

  17. Evolution of helium rich stars with hydrogen burning

    International Nuclear Information System (INIS)

    Evolutionary tracks of stars with an initial chemical composition X = 0.100, Y = 0.8790, Z = 0.021 are calculated for masses of 0.35 M(sun), 0.66 M(sun), 1.00 M(sun), 2.00 M(sun), and 5.00 M(sun) and with X = 0.302, Y = 0.677, Z = 0.021 for masses of 1.00 M(sun), 3.00 M(sun), and 5.00 M(sun). The evolution is followed from hydrogen burning to helium burning and to carbon burning when the occasion arises. The data of evolution are presented and compared with normal Population I-stars. The helium rich stars show higher effective temperatures, much higher luminosities and therefore shorter time scales. They are situated in regions of the HR-diagram where observed helium stars are found. (orig.)

  18. Lamb shift in muonic helium ion

    CERN Document Server

    Martynenko, A P

    2006-01-01

    The Lamb shift (2P_{1/2}-2S_{1/2}) in the muonic helium ion (mu ^4_2He)^+ is calculated with the account of contributions of orders alpha^3, alpha^4, alpha^5 and alpha^6. Special attention is given to corrections of the electron vacuum polarization, the nuclear structure and recoil effects. The obtained numerical value of the Lamb shift 1381.716 meV can be considered as a reliable estimate for the comparison with experimental data.

  19. Lamb shift in muonic helium ion

    OpenAIRE

    Martynenko, A. P.

    2006-01-01

    The Lamb shift (2P_{1/2}-2S_{1/2}) in the muonic helium ion (mu ^4_2He)^+ is calculated with the account of contributions of orders alpha^3, alpha^4, alpha^5 and alpha^6. Special attention is given to corrections of the electron vacuum polarization, the nuclear structure and recoil effects. The obtained numerical value of the Lamb shift 1379.028 meV can be considered as a reliable estimate for the comparison with experimental data.

  20. Evolution of defects in silicon carbide implanted with helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chonghong, E-mail: c.h.zhang@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Song, Yin, E-mail: songyin@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yang, Yitao, E-mail: yangyt@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhou, Chunlan; Wei, Long [Institute of High-Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Ma, Hongji [Department of Technical Physics, Peking University, Beijing 100871 (China)

    2014-05-01

    Effects of accumulation of radiation damage in silicon carbide are important concerns for the use of silicon carbide in advanced nuclear energy systems. In the present work lattice damage in silicon carbide crystal (4H type) implanted with 100 keV {sup 4}He{sup +} ions was investigated with Rutherford backscattering spectrometry in channeling geometry (RBS/c) and positron beam Doppler broadening spectrometry (PBDB). Helium implantation was performed at the specimen temperature of 510 K to avoid amorphization of the SiC crystal. Fluences of helium ions were selected to be in the range from 1 × 10{sup 16} to 3 × 10{sup 16} ions cm{sup ?2}, around the dose threshold for the formation of observable helium bubbles under transmission electron microscopes (TEM). The RBS/c measurements show distinctly different annealing behavior of displaced Si atoms at doses below or above the threshold for helium bubble formation. The RBS/c yield in the peak damage region of the specimen implanted to 3 × 10{sup 16} He-ions cm{sup ?2} shows an increase on the subsequently thermal annealing above 873 K, which is readily ascribed to the extra displacement of Si atoms due to helium bubble growth. The RBS/c yield in the specimen implanted to a lower ion fluence of 1.5 × 10{sup 16} He-ions cm{sup ?2} decreases monotonously on annealing from ambient temperatures up to 1273 K. The PBDB measurements supply evidence of clustering of vacancies at temperatures from 510 to 1173 K, and dissociation of vacancy clusters above 1273 K. The similarity of annealing behavior in PBDB profiles for helium implantation to 1 × 10{sup 16} and 3 × 10{sup 16} ions cm{sup ?2} is ascribed to the saturation of trapping of positrons in vacancy type defects in the damaged layers in the specimens helium-implanted to the two dose levels.

  1. Evolution of defects in silicon carbide implanted with helium ions

    International Nuclear Information System (INIS)

    Effects of accumulation of radiation damage in silicon carbide are important concerns for the use of silicon carbide in advanced nuclear energy systems. In the present work lattice damage in silicon carbide crystal (4H type) implanted with 100 keV 4He+ ions was investigated with Rutherford backscattering spectrometry in channeling geometry (RBS/c) and positron beam Doppler broadening spectrometry (PBDB). Helium implantation was performed at the specimen temperature of 510 K to avoid amorphization of the SiC crystal. Fluences of helium ions were selected to be in the range from 1 × 1016 to 3 × 1016 ions cm?2, around the dose threshold for the formation of observable helium bubbles under transmission electron microscopes (TEM). The RBS/c measurements show distinctly different annealing behavior of displaced Si atoms at doses below or above the threshold for helium bubble formation. The RBS/c yield in the peak damage region of the specimen implanted to 3 × 1016 He-ions cm?2 shows an increase on the subsequently thermal annealing above 873 K, which is readily ascribed to the extra displacement of Si atoms due to helium bubble growth. The RBS/c yield in the specimen implanted to a lower ion fluence of 1.5 × 1016 He-ions cm?2 decreases monotonously on annealing from ambient temperatures up to 1273 K. The PBDB measurements supply evidence of clustering of vacancies at temperatures from 510 to 1173 K, and dissociation of vacancy clusters above 1273 K. The similarity of annealing behavior in PBDB profiles for helium implantation to 1 × 1016 and 3 × 1016 ions cm?2 is ascribed to the saturation of trapping of positrons in vacancy type defects in the damaged layers in the specimens helium-implanted to the two dose levels

  2. Pierre Gorce working on a helium pump.

    CERN Multimedia

    1975-01-01

    This type of pump was designed by Mario Morpurgo, to circulate liquid helium in superconducting magnets wound with hollow conductors. M. Morpurgo, Design and construction of a pump for liquid helium, CRYIOGENICS, February 1977, p. 91

  3. Primary population of antiprotonic helium states

    OpenAIRE

    Révai, J.; Shevchenko, N. V.

    2003-01-01

    A full quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. Calculations were carried out for a wide range of antiprotonic helium states and incident (lab) energies of the antiproton.

  4. Atomic spectra in a helium bubble

    OpenAIRE

    Nakatsukasa, takashi; Yabana, Kazuhiro; Bertsch, George F.

    2002-01-01

    Density functional theory (DFT) is applied to atomic spectra under perturbations of superfluid liquid helium. The atomic DFT of helium is used to obtain the distribution of helium atoms around the impurity atom, and the electronic DFT is applied to the excitations of the atom, averaging over the ensemble of helium configurations. The shift and broadening of the D1 and D2 absorption lines are quite well reproduced by theory, suggesting that the DFT may be useful for describin...

  5. Study of the hadron-helium and helium-helium scattering at high energy

    International Nuclear Information System (INIS)

    Multiple scattering Glauber's theory is used to calculate the hadron-helium and helium-helium elastic differential cross-section. The theory is very sensitive to the 4He wave functions. We use better 4He wave functions than experimental ones. These wave functions have correct asymptotic shape. In some calculations, we take into account the spin effects and the 4He, S, S' and D states contribution. At high energy, we use inelastic corrections, to complete the differential cross-section. A study of the diffractive and coherent p-4He ? 4He-X dissociation is developed. We use Humble's amplitudes with a peripherical character and an helicity structure. The agreement with experimental results is good for 24 to 400 GeV

  6. Diffraction of an atomic helium beam

    International Nuclear Information System (INIS)

    The history, principles, and experimental set-up of the study of the diffraction of a helium beam by a crystal are recalled. The helium-surface interaction potential is explained. Surface study by helium diffraction; and the study of inelastic scattering: measurement of the scattering relation of surface phonons are considered

  7. Helium compounds and solidification of ? particles

    International Nuclear Information System (INIS)

    Helium is not rare gas in the universe, and also not inert gas, for there are Helium com- pounds, ?-Particles emitted from plutonium can be solidified based on the formation of helium compounds, then, the coefficient expansion of plutonium is negligible with such a solidification, otherwise, will be remarkable to 6.8%. (author)

  8. 21 CFR 184.1355 - Helium.

    Science.gov (United States)

    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...

  9. 21 CFR 582.1355 - Helium.

    Science.gov (United States)

    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...

  10. Helium distribution functions in tokamak plasmas

    International Nuclear Information System (INIS)

    Two different methods are used to obtain information on the helium distribution. The first method is a machine that measures the velocity distribution of neutral helium particles escaping from the plasma (NPA). The second method is charge exchange spectroscopy that measures the helium density and temperature as a function of time and place from the Doppler broadened intensity of He lines. (orig./HP)

  11. Helium measurements for the MFE-4 spectral tailoring experiment

    International Nuclear Information System (INIS)

    Measurements of helium concentration have been made on Fe-15.1Cr-34.5Ni specimens irradiated at 330, 400, 500 and 600 degree C after irradiation in ORR to displacement levels ranging from 12.6 to 13.8 dpa. The measurements compare well to previously calculated values, being 4 to 8% lower. Minor differences in helium content were also observed between specimens from capsules that were assumed to have possessed identical spectral environments. 6 refs., 1 fig., 2 tabs

  12. White Dwarfs in NGC 6791: Avoiding the Helium Flash

    OpenAIRE

    Hansen, Brad

    2005-01-01

    We propose that the anomalously bright white dwarf luminosity function observed in NGC 6791 (Bedin et al 2005) is the consequence of the formation of 0.5 Msun white dwarfs with Helium cores instead of Carbon cores. This may happen if mass loss during the ascent of the Red Giant Branch is strong enough to prevent a star from reaching the Helium flash. Such a model can explain the slower white dwarf cooling (relative to standard models) and fits naturally with scenarios advanc...

  13. Supercritical Helium Cooling of the LHC Beam Screens

    CERN Document Server

    Hatchadourian, E; Tavian, L

    1998-01-01

    The cold mass of the LHC superconducting magnets, operating in pressurised superfluid helium at 1.9 K, must be shielded from the dynamic heat loads induced by the circulating particle beams, by means of beam screens maintained at higher temperature. The beam screens are cooled between 5 and 20 K by forced flow of weakly supercritical helium, a solution which avoids two-phase flow in the long, narr ow cooling channels, but still presents a potential risk of thermohydraulic instabilities. This problem has been studied by theoretical modelling and experiments performed on a full-scale dedicated te st loop.

  14. A design for a pinhole scanning helium microscope

    International Nuclear Information System (INIS)

    We present a simplified design for a scanning helium microscope (SHeM) which utilises almost entirely off the shelf components. The SHeM produces images by detecting scattered neutral helium atoms from a surface, forming an entirely surface sensitive and non-destructive imaging technique. This particular prototype instrument avoids the complexities of existing neutral atom optics by replacing them with an aperture in the form of an ion beam milled pinhole, resulting in a resolution of around 5 microns. Using the images so far produced, an initial investigation of topological contrast has been performed

  15. PG-100 helium loop in the MR reactor

    International Nuclear Information System (INIS)

    Main systems and production equipment units of PG-100 helium loop in the MR reactor are described. Possible long-term synchronizing operation of loop and reactor as well as possibility of carrying out life-time tests of spherical fuel elements and materials are shown. Serviceability of spherical fuel elements under conditions similar to the ones of HTGR-50 operation as well as high serviceability of cleanup system accepted for HTGR are verified. Due to low radiation dose the loop is operated without limits, helium losses in the loop don't exceed 0.5%/24 h, taking account of experimental gas sampling

  16. Effect of helium on tensile properties of vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Billone, M.C.; Smith, D.L. [Argonne National Lab., IL (United States)

    1997-08-01

    Tensile properties of V-4Cr-4Ti (Heat BL-47), 3Ti-1Si (BL-45), and V-5Ti (BL-46) alloys after irradiation in a conventional irradiation experiment and in the Dynamic Helium Charging Experiment (DHCE) were reported previously. This paper presents revised tensile properties of these alloys, with a focus on the effects of dynamically generated helium of ductility and work-hardening capability at <500{degrees}C. After conventional irradiation (negligible helium generation) at {approx}427{degrees}C, a 30-kg heat of V-4Cr-4Ti (BL-47) exhibited very low uniform elongation, manifesting a strong susceptibility to loss of work-hardening capability. In contrast, a 15-kg heat of V-3Ti-1Si (BL -45) exhibited relatively high uniform elongation ({approx}4%) during conventional irradiation at {approx}427{degrees}C, showing that the heat is resistant to loss of work-hardening capability.

  17. Helium refrigeration system for BNL colliding beam accelerator

    International Nuclear Information System (INIS)

    A Helium Refrigeration System which will supply the cooling required for the Colliding Beam Accelerator at Brookhaven National Laboratory is under construction. Testing of the compressor system is scheduled for late 1983 and will be followed by refrigerator acceptance tests in 1984. The refrigerator has a design capacity of 24.8 kW at a temperature level near 4K while simultaneously producing 55 kW for heat shield loads at 55K. When completed, the helium refrigerator will be the world's largest. Twenty-five oil-injected screw compressors with an installed total of 23,250 horsepower will supply the gas required. One of the unique features of the cycle is the application of three centrifugal compressors used at liquid helium temperature to produce the low temperatures (2.5K) and high flow rates (4154 g/s) required for this service

  18. Positron helium scattering using CCA

    International Nuclear Information System (INIS)

    Calculations have been carried out to investigate e+-He scattering using close coupling method with various basis sets. The n=2 excitation cross section and positronium cross section are reported at medium energies. Two dynamically active electrons have been considered on same footing and realistic wavefunctions of helium target have been used. (author). 20 refs., 3 figs

  19. ULTRASONIC ATTENUATION IN SOLID HELIUM

    OpenAIRE

    Beamish, J

    1985-01-01

    A great deal of information about the motion of dislocations in solid helium has been obtained from ultrasonic and internal friction measurements. A brief review is given and representative data for 3He are presented, showing dislocation resonance and damping as well as pinning effects.

  20. Chromatographic method of measurement of helium concentration in underground waters for dating in hydrological questions

    International Nuclear Information System (INIS)

    Research methods which use natural environmental indicators are widely applied in hydrology. Different concentrations of indicators and their isotopic components in ground waters allow to determine the genesis of waters and are valuable source of information about the water flow dynamics. One of the significant indicator is helium. The concentration of 4He (helium) in ground water is a fine indicator in water dating in a range from a hundreds to millions of years (Aeschbach-Hertig i in., 1999; Andrews i in., 1989; Castro i in., 2000; Zuber i in., 2007). 4He is also used for dating young waters of age about 10 years (Solomon i in., 1996). Thesis consist the description of elaborated in IFJ PAN in Krakow chromatographic measurement method of helium concentration in ground waters in aim of dating. Chapter 1 contain short introduction about ground water dating and chapter 2 description of helium property and chosen applications of helium for example in technology and earthquake predictions. Helium sources in ground waters are described in chapter 3. Helium concentration in water after infiltration (originated from atmosphere) to the ground water system depends mainly on the helium concentration coming from the equilibration with the atmosphere increased by additional concentration from '' excess air ''. With the increasing resistance time of ground water during the flow, radiogenic, non-atmospheric component of helium dissolves also in water. In chapter 4 two measurement methods of helium concentration in ground waters were introduced: mass spectrometric and gas chromatographic method. Detailed description of elaborated chromatographic measurement method of helium concentration in ground water contain chapter 5. To verify developed method the concentration of helium in ground waters from the regions of Krakow and Busko Zdroj were measured. For this waters the concentrations of helium are known from the earlier mass spectrometric measurements. The results of verification are introduced in chapter 6. Described in chapter 5 chromatographic method was applied to measurements of helium concentration in ground waters from the regions of Zakopane, Raciborz and Torun. Obtained results of this measurements are shown in chapter 7. Appendixes A and B contain explanation of chromatographic system calibration and head-space method respectively. Detailed description of calculation of helium concentration in ground water using elaborated method and measurement deviations are introduced in Appendixes C and D. (author)

  1. Kapitza resistance between liquid and solid helium

    International Nuclear Information System (INIS)

    The results of a study of the Kapitza resistance (R/sub K/ between liquid and solid helium-4 are presented. In the first chapter the recent proposal by Andreev and Parshin that, because of quantum delocalization of surface defects, the boundary between liquid and solid helium-4 would be in a special state is discussed. This state may be regarded as a quantum analog of an atomically rough interface. This particular interface is able to impede the passage of phonons because it can melt or freeze without dissipation as a response to an external non-equilibrium situation, i.e., pressure waves (phonons). In the second chapter two calculations of R/sub K/ are presented. One of them, the Acoustic-Mismatch calculation, is based on a model of the interface where no melting or freezing can occur. In this model the interface behaves as classical (non-rough). The usual T-3 temperature dependence is obtained. The other calculation is based on the model of the rough interface of Andreev and Parshin. R/sub K/ has a T-5 temperature dependence at low temperatures. At high temperatures (T > 0.5K) the two theories give approximately the same result for R/sub K/. In the third and fourth chapter experimental results for the phonon transmission coefficient across the interface are presented. These measurements are consistent with the rough interface theory of the Kapitza resistance

  2. LRO-LAMP Observations of Lunar Exospheric Helium

    Science.gov (United States)

    Grava, Cesare; Retherford, Kurt D.; Hurley, Dana M.; Feldman, Paul D.; Gladstone, Randy; Greathouse, Thomas K.; Cook, Jason C.; Stern, Alan; Pryor, Wayne R.; Halekas, Jasper S.; Kaufmann, David E.

    2015-11-01

    We present results from Lunar Reconnaissance Orbiter’s (LRO) UV spectrograph LAMP (Lyman-Alpha Mapping Project) campaign to study the lunar atmosphere. Two kinds of off-nadir maneuvers (lateral rolls and pitches towards and opposite the direction of motion of LRO) were performed to search for resonantly scattering species, increasing the illuminated line-of-sight (and hence the signal from atoms resonantly scattering the solar photons) compared to previously reported LAMP “twilight observations” [Cook & Stern, 2014]. Helium was the only element distinguishable on a daily basis, and we present latitudinal profiles of its line-of-sight column density in December 2013. We compared the helium line-of-sight column densities with solar wind alpha particle fluxes measured from the ARTEMIS (Acceleration, Reconnection, Turbulence, & Electrodynamics of Moon’s Interaction with the Sun) twin spacecraft. Our data show a correlation with the solar wind alpha particle flux, confirming that the solar wind is the main source of the lunar helium, but not with a 1:1 relationship. Assuming that the lunar soil is saturated with helium atoms, our results suggest that not all of the incident alpha particles are converted to thermalized helium, allowing for a non-negligible fraction (~50 %) to escape as suprathermal helium or simply backscattered from the lunar surface. We also support the finding by Benna et al. [2015] and Hurley et al. [2015], that a non-zero contribution from endogenic helium, coming from radioactive decay of 232Th and 238U within the mantle, is present, and is estimated to be (4.5±1.2) x 106 He atoms cm-2 s-1. Finally, we compare LAMP-derived helium surface density with the one recorded by the mass spectrometer LACE (Lunar Atmospheric Composition Experiment) deployed on the lunar surface during the Apollo 17 mission, finding good agreement between the two measurements. These LRO off-nadir maneuvers allow LAMP to provide unique coverage of local solar time and latitude of the lunar exospheric helium, allowing for a better understanding of the temporal and spatial structure of the lunar exosphere.

  3. Imprints from the solar cycle on the helium atom and helium pickup ion distributions

    Directory of Open Access Journals (Sweden)

    D. Rucinski

    Full Text Available Neutral interstellar helium atoms penetrate into the solar system almost unaffected by gas–plasma interactions in the heliospheric interface region, and thus can be considered as carriers of original information on the basic parameters (like density, temperature, bulk velocity of the Very Local Interstellar Medium (VLISM. Such information can nowadays be derived from analysis of data obtained from different experimental methods: in situ measurements of He atoms (Ulysses, observations of the solar backscattered He 584 A radiation (EUVE, in situ measurements of He + pickup ions (AMPTE, Ulysses, Wind, SOHO, ACE. In view of the current coordinated international ISSI campaign devoted to the study of the helium focusing cone structure and its evolution, we analyze expected variations of neutral He density, of He + pickup fluxes and of their phase space distributions at various phases of the solar activity cycle based on a realistic time-dependent modelling of the neutral helium and He + pickup ion distributions, which reflect solar cycle-induced variations of the photoionization rate. We show that the neutral helium density values are generally anticorrelated with the solar activity phase and in extreme cases (near the downwind axis the maximum-to-minimum density ratio may even exceed factors of ~ 3 at 1 AU. We also demonstrate that in the upwind hemisphere (at 1 AU and beyond the He + fluxes are correlated with the solar cycle activity, whereas on the downwind side the maximum of the expected flux up to distances of ~ 3 AU occurs around solar minimum epoch, and only further away does the correlation with solar activity become positive. Finally, we present the response of the phase space distribution spectra of He + pickup ions (in the solar wind frame for different epochs of the solar cycle and heliocentric distances from 1 to 5 AU covering the range of Ulysses, Wind and ACE observations.

    Key words. Solar physics, astrophysics and astronomy (ultraviolet emissions – Space plasma physics (ionization processes; numerical simulation studies

  4. Trapping and release of helium in tungsten

    OpenAIRE

    Lhuillier, Pierre-Emile; Belhabib, Taieb; Desgardin, Pierre; Courtois, Blandine; Sauvage, Thierry; Barthe, Marie-France; Thomann, Anne-Lise; Brault, Pascal; Tessier, Yves

    2011-01-01

    The behavior of tungsten under irradiation and helium implantation is a major stake of the materialrelated issues of fusion reactors. In this perspective the fate of helium in tungsten was studied by mean of several characterization techniques. The aim of this study is to highlight the trapping mechanisms of helium in tungsten and their correlation with implantation-induced defects. Helium was implanted into tungsten at two different energies, 0.32 and 60 keV. The helium was studied as a func...

  5. Formation of Triplet Positron-helium Bound State by Stripping of Positronium Atoms in Collision with Ground State Helium

    Science.gov (United States)

    Drachman, Richard J.

    2006-01-01

    Formation of triplet positron-helium bound state by stripping of positronium atoms in collision with ground state helium JOSEPH DI RlENZI, College of Notre Dame of Maryland, RICHARD J. DRACHMAN, NASA/Goddard Space Flight Center - The system consisting of a positron and a helium atom in the triplet state e(+)He(S-3)(sup e) was conjectured long ago to be stable [1]. Its stability has recently been established rigorously [2], and the values of the energies of dissociation into the ground states of Ps and He(+) have also been reported [3] and [4]. We have evaluated the cross-section for this system formed by radiative attachment of a positron in triplet He state and found it to be small [5]. The mechanism of production suggested here should result in a larger cross-section (of atomic size) which we are determining using the Born approximation with simplified initial and final wave functions.

  6. Applicability of Henry's Law to helium solubility in olivine

    Science.gov (United States)

    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 pressure vessel (Brown University). The starting materials were prepared by cutting gem-quality San Carlos olivine (~Fo90) into small blocks (~4×2×1 mm) using a diamond wafering blade saw and polishing with alumina slurries and colloidal silica. Analysis was completed by laser ablation-mass spectrometry using a 193 nm excimer laser and a MAP 215-50 specifically tuned for He (Open University, UK). Laser ablation pit depth varied from 2 to 40 ?m, and no correlation between pit depth and [He] is observed after accounting for variations PHe across the different experiments. This lack of correlation indicates a close approach to equilibrium was achieved over the experimental durations. Two analyses yielded spuriously high [He] (>3 std. dev. from the population mean, n = 85), and these analyses were not used to calculate Henry's coefficients. The two spuriously high analyses, in combination with the right skew of Henry's coefficients calculated from individual data points, suggests gem-quality San Carlos olivine contains volumes with anomalously high helium solubility. The nature of these volumes is currently under investigation. However, despite their presence, helium is still highly incompatible in olivine during partial melting. [1] Lux GCA 1987 [2] Heber et al. GCA 2007 [3] Shcheka & Keppler Nature 2012 [4] Walker et al. PEPI 2009

  7. HeREF-2003: Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 Cost per participant: 500.- CHF Language: Bilingual English...

  8. HeREF-2003 : Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. ? Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 ? Cost per participant: 500.- CHF ...

  9. Mixed helium-3 - helium-4 calorimeter. Very low temperature calorimetry

    International Nuclear Information System (INIS)

    A description is given of a double-racket calorimeter using helium-4 and helium-3 as the cryogenic fluids and making it possible to vary the temperature continuously from 0.35 K to 4.2 K. By using an electric thermal regulator together with liquid hydrogen it is possible to extend this range up to about 30 K. In the second part, a review is made of the various, methods available for measuring specific heats. The method actually used in the apparatus previously described is described in detail. The difficulties arising from the use of an exchange gas for the thermal contact have been solved by the use of adsorption pumps. (author)

  10. On the abundance of primordial helium

    CERN Document Server

    Olive, Keith A; Keith A Olive; Gary Steigman

    1994-01-01

    We have used recent observations of helium-4, nitrogen and oxygen from some four dozen, low metallicity, extra-galactic HII regions to define mean N versus O, ^4He versus N and ^4He versus O relations which are extrapolated to zero metallicity to determine the primordial ^4He mass fraction Y_P. The data and various subsets of the data, selected on the basis of nitrogen and oxygen, are all consistent with Y_P = 0.232 \\pm 0.003. For the 2\\sigma (statistical) upper bound we find Y_P^{2\\sigma} \\le 0.238. Estimating a 2\\% systematic uncertainty (\\sigma _{syst} = \\pm 0.005) leads to a maximum upper bound to the primordial helium mass fraction: Y_P^{MAX} = Y_P^{2\\sigma} + \\sigma_{syst} \\le 0.243. We compare these upper bounds to Y_P with recent calculations of the predicted yield from big bang nucleosynthesis to derive upper bounds to the nucleon-to-photon ratio \\eta (\\eta_{10} \\equiv 10^{10}\\eta) and the number of equivalent light (\\lsim 10 MeV) neutrino species. For Y_P \\le 0.238 (0.243), we find \\eta_{10} \\le 2.5...

  11. Energy distribution in the plume of a helium arcjet

    Science.gov (United States)

    Welle, Richard Patrick Daniel

    1998-10-01

    Helium has been proposed as a propellant for arcjets because of its high theoretical frozen flow efficiency. Because of storage concerns, however, helium arcjets have not previously been carefully investigated. In this work, a preliminary investigation of the space storability of helium has shown that the problem is not insurmountable, justifying a detailed study of the performance of helium arcjets. Experiments were conducted using the 1 kW NASA-Lewis laboratory model arcjet. Direct performance measurements using a thrust balance demonstrated specific impulses in the 500 to 600 second range, with overall efficiencies of up to 60%. Specific impulse and efficiency were found to increase with increasing propellant flow rate and increasing cathode gap. Spectroscopic measurements in the arcjet plume were used to estimate all the significant frozen flow losses. Emission measurements of the 43D-23P and 43F-23P lines in helium were used to determine the electron number density in the plume. Typical ionization fractions were 0.2%, constituting a 6% frozen flow loss. Diode laser atomic absorption measurements on the 23S-23P0 transition were used to measure the metastable number density. The metastable fraction in the plume was typically less than 10-5, with a negligible contribution to the frozen flow loss, leaving the total frozen flow loss at about 6%. Spatially resolved Doppler broadening and Doppler shift measurements on the 23S-23P0 transition showed that thermal energy in the plume accounts for about 10% of the input power, while profile losses in the nozzle account for about 1% of the input power. Experiments with hydrogen seeding indicated that the addition of a small fraction (~1%) of hydrogen to the helium flow helped to stabilize the arcjet but had little effect on the overall efficiency of the system.

  12. Performance test of a helium refrigerator for the cryogenic hydrogen system in J-PARC

    CERN Document Server

    Tatsumoto, H; Kato, T; Ohtsu, K; Hasegawa, S; Maekawa, F; Futakawa, M

    2009-01-01

    In J-PARC, a cryogenic hydrogen system, which plays a role in providing supercritical hydrogen with a pressure of 1.5 MPa and a temperature of 20 K to three moderators, has been designed. The performance test of the helium refrigeration system that is a part of the cryogenic hydrogen system was conducted independently. The helium refrigeration system was cooled down to 18 K within 4.5 hours, and the refrigerator power of 6.45 kW at 15.6 K was confirmed. The performance test results verified that the helium refrigerator satisfied the performance requirements.

  13. Contribution to the experimental study of the polarized liquid helium-3; Contributions a l'etude experimentale de l'helium-3 liquide polarise

    Energy Technology Data Exchange (ETDEWEB)

    Villard, B

    1999-07-15

    Spin-polarized liquid helium-3 is prepared by laser optical pumping in low magnetic field and at room temperature, prior to fast liquefaction of the polarized sample. The use of a new helium-3 cryostat enabled us to obtain liquid helium-3 with polarization rates up to 25 % at well-stabilized temperatures (around 0.5 K). We could thereby study the effect of nuclear polarization on liquid-vapour equilibrium, and particularly on the saturated vapour pressure. Very sensitive capacitive gauges were developed. We estimated (to first order in M{sup 2}) the expected effects when the polarization M is suddenly destroyed. These effects were experimentally observed in helium-3/helium-4 mixtures, in pure helium-3, only a transient increase in pressure has been recorded. We then describe in a third part a preliminary experiment which aimed at determining the longitudinal relaxation time T1 in mixtures. Relaxation on the walls is efficiently reduced by a cesium coating and T1s of order 20 minutes were observed. A careful determination of the helium-3 concentration in the liquid phase was made. Finally we studied the effects of dipolar field on transverse polarisation decay in our strongly polarized samples. We observed the free precession of polarization after a NMR pulse, and analysed in detail its decay time constant as a function of different parameters. This time constant drastically varied with the tipping angle, an effect which could be linked to NMR dynamical instabilities. (author)

  14. Supersolid Phase in Helium-4

    CERN Document Server

    Tiwari, M; Tiwari, Mukesh; Datta, Animesh

    2004-01-01

    The probable observation of a supersolid helium phase was recently reported by Kim {\\it et al}. In this article, we confirm their speculation. Based on a theoretical model for solid helium-4, we show that the emergence of such a phase is inevitable. This is the first instance of Bose-Einstein condensation (BEC) in a solid. We calculate the BEC transition temperature ($T_c$) and the Landau critical velocity ($v_c$) from the model, which respectively are 215 mK and $251 \\mu \\rm{ms^{-1}}$. They are in excellent agreement with the experimental results; $T_c=$175 mK and $v_c \\leq 300 \\mu \\rm{ms^{-1}}$. We also prove that our model possesses the necessary and sufficient condition for the emergence of supersolidity. We briefly comment about similar behaviour in $^3$He.

  15. Confined helium on Lagrange meshes.

    Science.gov (United States)

    Baye, D; Dohet-Eraly, J

    2015-11-25

    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. PMID:25732054

  16. Orbital resupply of liquid helium

    Science.gov (United States)

    Kittel, P.

    1985-01-01

    The ability to resupply scientific instruments in orbit with liquid helium would greatly enhance several planned missions. These missions include the SIRTF (Space Infrared Telescope Facility), the LDR (Large Deployable Reflector), the GP-B (Gravity Probe - B), and include individual instruments on the HST (Hubble Space Telescope), and on the AXAF (Advanced X-ray Astrophysics Facility). Resupply in orbit would extend the lifetimes of these missions without the difficulties, the delays, and the costs that are associated with retrieving the system, resupplying these systems on the ground, and relaunching. This is especially true of systems, such as the LDR, that are assembled in space and thus would be difficult to return to earth. This paper presents a conceptual design of a Helium Resupply System (HERS) and a discussion of the transfer efficiency.

  17. Rapidly pulsed helium droplet source

    International Nuclear Information System (INIS)

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 104 and 106 helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  18. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  19. Few-body approach to diffraction of small helium clusters by nano structures

    International Nuclear Information System (INIS)

    We use few-body methods to investigate the diffraction of weakly bound systems by a transmission grating. For helium dimers, He2, we obtain explicit expressions for the transition amplitude in the elastic channel. Refs. 15, figs. 5 (author)

  20. The Epoch of Helium Reionization

    OpenAIRE

    Sokasian, Aaron; Abel, Tom; Hernquist, Lars. E.

    2001-01-01

    We study the reionization of Helium II by quasars using a numerical approach that combines 3D radiative transfer calculations with cosmological hydrodynamical simulations. Sources producing the ionizing radiation are selected according to an empirical quasar luminosity function and are assigned luminosities according to their intrinsic masses. We present models in which these parameters are varied and examine characteristics of the resultant reionization process that disting...

  1. The helium detector, ch. 8

    International Nuclear Information System (INIS)

    The helium detector (and also the argon detector) is the only ionization detector operating in the multiplication region of the volt-ampere characteristic. The detection mechanism and some characteristics of the HeD signal, such as background current and response are discussed. A survey of the effect of experimental conditions on the HeD signal is given and some applications are discussed, e.g. the gas chromatography of permanent gases

  2. Heat transfer in helium-1

    International Nuclear Information System (INIS)

    Experimental heat transfer coefficients for nucleate pool boiling of helium at 1 to 2 bar, critical heat fluxes qsub(max) and temperature drops ?Tsub(max) are presented. The qsub(max) and ?Tsub(max) values are theoretically interpreted in terms of a thermal model of departure from nucleate boiling. The dependences are derived for heat transfer coefficients on temperature averaged over the volume in the supercritical region up to 4.9 bar and T = 7 K. (author)

  3. Helium-cooled divertor module for fusion devices

    Science.gov (United States)

    Baxi, Chandrakant B.

    1993-11-01

    The advanced fusion machines such as TPX, NET, and ITER have to be designed to handle a heat flux of about 5 to 15 MW/m2 in the diverter region. The present conceptual designs use water cooling. However water leaks will have very serious consequences in these machines. Cooling with a gas like helium is a very attractive alternative, if the pumping power can be limited to a reasonable value. Different concepts to cool diverter by helium gas were compared. It was found that it is feasible to remove significant steady state heat flux (10 to 20 MW/m2) by using helium at a pressure of 4 MPa (580 psia) and with pumping power less than 0.5% of the power removed, by using optimized designs. From pumping power consideration, various concepts rank in the following order: offset fins (best), fins, jets, 3-D roughness, 2-D roughness, smooth tubes (worst). A module based on this study has been designed and fabricated for a steady state operation at 10 MW/m2 and was tested at the High Heat Flux facility at Sandia National Laboratory. This paper also presents some preliminary studies of helium cooled ITER diverter.

  4. Hyperfine structure of helium three

    International Nuclear Information System (INIS)

    Relativistic contributions to the hyperfine structure of Helium 3 are re-examined in order to resolve the inconsistencies in the published values. The orbit-orbit and diamagnetic screening contributions are recomputed. They are each found to contribute less than one part per million, contrary to published values. A new value is obtained for the relativistic velocity correction by comparing the hyperfine structure computed using non-relativistic Hartree-Fock wave functions with that computed using recently available relativistic Hartree-Fock wave functions. The resulting correction is 318 ppm compared with a previously published result of 327 ppm calculated perturbation theory. A review of all contributions to the hyperfine structure including nuclear structure corrections is presented. New values of the hyperfine structure splitting of Helium 3 in the 1S2S state and of the ratio of this splitting to the hyperfine structure splitting of the Helium 3 ion in the 1S and 2S states are calculated and compared with experiment. Comparison with experiment suggests that the relativistic velocity correction is 323 ppm and that the total nuclear structure correction is 185.8 ppm

  5. Design of the Helium Purifier for IHEP-ADS Helium Purification System

    OpenAIRE

    Jianqin, Zhang; Shaopeng, Li; Zhuo, Zhang; Rui, Ge

    2015-01-01

    Helium Purification System is an important sub-system in the Accelerator Driven Subcritical System of the Institute of High Energy Physics(IHEP ADS). The purifier is designed to work at the temperature of 77K. The purifier will work in a flow rate of 5g/s at 20MPa in continuous operation of 12 hours. The oil and moisture are removed by coalescing filters and a dryer, while nitrogen and oxygen are condensed by a phase separator and then adsorbed in several activated carbon ad...

  6. The growth of helium burning cores

    CERN Document Server

    Spruit, H C

    2015-01-01

    Helium burning in the convective cores of horizontal branch and `red clump' stars appears to involve a process of `ingestion' of unburnt helium into the core, the physics of which has not been identified yet. I show here that a limiting factor controlling the growth is the buoyancy of helium entering the denser C+O core. It yields a growth rate which scales directly with the convective luminosity of the core, and agrees with constraints on core size from current asteroseismology.

  7. Helium cyclotron resonance within the earth's magnetosphere

    International Nuclear Information System (INIS)

    A histogram of electromagnetic Alfven/ion cyclotron wave frequencies, sampled within the geostationary enviroment and normalized by the equatorial proton cyclotron frequency, shows a dramatic gap centered near the helium (He+) cyclotron frequency. Also, strongly cyclotron phase bunched helium ions (20--200 eV) have been observed directly within the vicinity of wave environments. These observations are interpreted as resulting from the absorption of the waves through cyclotron resonance by cool ambient populations of helium ions

  8. Critical Landau Velocity in Helium Nanodroplets

    OpenAIRE

    Brauer, Nils Benedict; Smolarek, Szymon; Loginov, Evgeniy; Matéo, David; Hernando de Castro, Alberto; Pi, Marti; Barranco, Manuel; Buma, Wybren Jan,; Drabbels, Marcel

    2013-01-01

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecu...

  9. Pulsation of high luminosity helium stars

    International Nuclear Information System (INIS)

    Preliminary calculations are made on a systematic restudy of the linear and nonlinear pulsations of helium stars allowing for more recent and higher estimates of the effective temperature and for the high carbon abundance. Linear and nonlinear models are used. Results show qualitative agreement with earlier ones, models with sufficiently large L/M have a very hot blue edge for their instability strip, very large L/M values lead to dynamically unstable models which would appear to eject mass and therefore may not be realistic models for the pulsating RCrB stars, for the sequence studied a reasonable mass could be greater than or equal to 1.5 Msub solar. 12 references

  10. Present status on helium technology of HTGR

    International Nuclear Information System (INIS)

    Helium technology on HTGR to keep integrity of the reactor structural materials over its life period, to controal chemical atmosphere in the coolant helium and to decline radioactivity in the primary system, is important affairs. Details of each systems on helijm purification, make-up and gas analysis, whick occupy important section of the technology, are surveied in the case of HTGRs and helium gas loops. Present status of the helium technology rounded off consequence of the survey is described in this paper. (author)

  11. Trapping fermionic and bosonic helium atoms

    OpenAIRE

    Stas, R. J. W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof-are cooled to a temperature around 1 mK and form the starting point of the presented studies. The studies include an investigation of cold ionizing collisions in the absence of resonant light, an...

  12. Low evaporation helium cryostat with a refrigerator

    International Nuclear Information System (INIS)

    Improvement of a helium cryostat for a superconducting magnet is reported. A small refrigerator pre-cools the magnet and removes heat load. A gas filled thermal switch cools a helium vessel and thermally insulates the vessel when the refrigerator stops. Nb3Sn wires are used in the helium vessel to avoid resistive heating. The evaporation rate of the liquid helium is 1.0 - 1.7 1/day (with external current of 28A), when a magnet (maximum field 7T in 25mm bore) is set in the cryostat. (author)

  13. Helium and tritium as tracers for physical processes in lakes

    International Nuclear Information System (INIS)

    The radioactive decay of 3H (tritium) to 3He with a half-life of 12.4 years offers an opportunity to measure the effective time of isolation of a water mass from the atmosphere. This timescale, called 3H-3He water mass age, can be used to quantify process rates in the hydrosphere. Helium on its own is an important geochemical tracer for volatiles from the interior of the earth. Helium and tritium are analysed by mass spectroscopy. In the course of this work, the experimental setup developed and described by Kipfer was continuously improved and simultaneously used for extensive lake studies. The reproducibility of helium and neon concentrations lies between 0.6 and 1%, for the 3H/3He-ratio it is below 0.5%. Routine tritium samples are measured with a precision of 2 to 3% and a detection limit of 0.5 TU, but both parameters can be lowered by an order of magnitude if larger samples are used. The measured concentrations of the two light noble gases in surface water of lakes are within 1 % of the values expected for equilibrium with the atmosphere, as given by Weiss (1971). However, the observed He/Ne ratios are more consistent with the solubility data of Top et al. (1987). It is shown how helium from other sources than tritium decay can be identified in order to calculate the tritiogenic 3He needed for the evaluation of a water mass age. The interpretation of such ages in not completely closed systems, as the deep waters in lakes, is discussed. The evolution of the water mass age is investigated with the aid of lake models of different complexity. These models serve as a basis to determine the parameters of physical processes, such as water exchange rates, vertical turbulent diffusivity, gas transfer velocity, oxygen utilization rate and helium flux from the earth. (author) figs., tabs., refs

  14. The Liquefaction of Hydrogen and Helium Using Small Coolers

    International Nuclear Information System (INIS)

    This report discusses the history of the liquefaction of hydrogen and helium using small coolers. This history dates form the 1960's when two stage GM coolers capable of reaching 7 K were used to liquefy helium and hydrogen by suing an added compressor and J-T circuit. Liquefaction using the added circuit failed to become mainstream because the J-T valve and heat exchanger clogged because of impurities in the gas being liquefied. Liquefaction using a GM cooler without an added J-T circuit proved to be difficult because the first stage was not used to pre-cool the gas coming to the second stage of the cooler. Once the gas being liquefied was pre-cooled using the cooler first stage, improvements in the liquefaction rates were noted. The advent of low temperature pulse tube cooler (down to 2.5 K) permitted one to achieve dramatic improvement is the liquefactions rates for helium. Similar but less dramatic improvements are expected for hydrogen as well. Using the PT-415 cooler, one can expect liquefaction rates of 15 to 20 liters per day for helium or hydrogen provided the heat leak into the cooler and the storage vessel is low. A hydrogen liquefier for MICE is presented at the end of this report

  15. Conceptual design of a helium heater for high temperature applications

    International Nuclear Information System (INIS)

    Highlights: •A special design of heater with two vessels is introduced for the operation at 10 MPa and 800 °C. •The additional coupling between the cold leg and the hot leg of the loop due to the heater design has an impact on the loop energy budget. •Reducing the heat transfer between the two flow channels inside the heater by means of a helium gap in the inlet nozzle is proven to be effective. -- Abstract: The Karlsruhe Advanced Technologies Helium Loop (KATHELO) has been designed for testing divertor modules as well as qualifying materials for high heat flux, high temperature (up to 800 °C) and high pressure (10 MPa) applications. The test section inlet temperature level is controlled using a process electrical heater. To cope with the extreme operating conditions, a special design of this unit has been proposed. In this paper the conceptual design of the unit will be presented and the impact of the coupling between the cold and hot helium gas on the overall efficiency of the loop will be investigated. The detailed thermal-hydraulic analysis of the feed through of the hot helium into the low temperature pressure vessel using ANSYS CFX will be presented. The impact of the design choices on the overall energy budget of the loop will be analyzed using RELAP5-3D

  16. Conceptual design of a helium heater for high temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Xue Zhou, E-mail: jin@kit.edu; Chen, Yuming; Ghidersa, Bradut-Eugen

    2014-10-15

    Highlights: •A special design of heater with two vessels is introduced for the operation at 10 MPa and 800 °C. •The additional coupling between the cold leg and the hot leg of the loop due to the heater design has an impact on the loop energy budget. •Reducing the heat transfer between the two flow channels inside the heater by means of a helium gap in the inlet nozzle is proven to be effective. -- Abstract: The Karlsruhe Advanced Technologies Helium Loop (KATHELO) has been designed for testing divertor modules as well as qualifying materials for high heat flux, high temperature (up to 800 °C) and high pressure (10 MPa) applications. The test section inlet temperature level is controlled using a process electrical heater. To cope with the extreme operating conditions, a special design of this unit has been proposed. In this paper the conceptual design of the unit will be presented and the impact of the coupling between the cold and hot helium gas on the overall efficiency of the loop will be investigated. The detailed thermal-hydraulic analysis of the feed through of the hot helium into the low temperature pressure vessel using ANSYS CFX will be presented. The impact of the design choices on the overall energy budget of the loop will be analyzed using RELAP5-3D.

  17. Suppression of runaway electron generation by massive helium injection after induced disruptions on TEXTOR

    Science.gov (United States)

    Lvovskiy, A.; Koslowski, H. R.; Zeng, L.; Zeng

    2015-10-01

    > Disruptions with runaway electron generation have been deliberately induced by injection of argon using a disruption mitigation valve. A second disruption mitigation valve has been utilised to inject varying amounts of helium after a short time delay. No generation of runaway electrons has been observed when more than a critical amount of helium has been injected no later than 5 ms after the triggering of the first valve. The required amount of helium for suppression of runaway electron generation is up to one order of magnitude lower than the critical density according to Connor & Hastie (1975) and Rosenbluth & Putvinski (1997).

  18. Ultra-cold neutron production with superfluid helium and spallation neutrons

    CERN Document Server

    Masuda, Y

    2000-01-01

    Ultra-cold neutrons (UCN) production in superfluid helium with spallation neutrons is discussed. A source is described, where superfluid helium is located in a cold moderator of deuterium at 20 K surrounded by a thermal moderator of heavy water at 300 K. A lead target is installed in the thermal moderator for neutron production via a medium energy proton induced spallation reaction. A Monte Carlo simulation showed that a UCN density of the order of 10 sup 5 n/cm sup 3 is achievable with an acceptable heat load for the helium cryostat.

  19. A small and light weight heat exchanger for on-board helium refrigerator

    Science.gov (United States)

    Koizumi, T.; Takahashi, M.; Uchida, T.; Kanazawa, Y.; Suzuki, M.

    1983-12-01

    A small and light weight heat exchanger used for small helium refrigerator has been developed by Sumitomo Heavy Industries, Ltd. This heat exchanger is a laminated metal heat exchanger which consists of perforated aluminum metal plates and glassfiber reinforced plastic separators. The size is from 100 mm to 28 mm in diameter and about 300 mm in length. The weight is from 2.5 kg to 0.6 kg. Also it can be used between room temperature and liquid helium temperature. The thermal efficiency obtained has been more than 96%. The heat exchanger has been practically used for on-board helium refrigerator in Japanese National Railways' superconducting magnetic levitated trains.

  20. Helium irradiation of alkali halides

    International Nuclear Information System (INIS)

    An investigation has been made of radiation damage in alkali halide crystals induced by heavy bombardment of 1 MeV helium ions. The channeling technique has been employed and three processes have been monitored simultaneously to explain the apparent reduction of damage at high doses. It is shown that the initial rise and fall of the back-scattered yield from different alkali halides can be related to the Pooley mechanism coupled with the aggregation of interstitials to form dislocation loops through the intermediate stage of clusters

  1. Helium bubble bursting in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Sefta, Faiza [University of California, Berkeley, California 94720 (United States); Juslin, Niklas [University of Tennessee, Knoxville, Tennessee 37996 (United States); Wirth, Brian D., E-mail: bdwirth@utk.edu [University of Tennessee, Oak Ridge National Laboratory, Knoxville, Tennessee 37996 (United States)

    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.

  2. Research and development of a helium-4 based solar neutrino detector

    Science.gov (United States)

    Lanou, R. E.; Maris, H. J.; Seidel, G. M.

    1992-06-01

    In this report we describe results of experiments to detect low energy radiation in superfluid helium. The ultimate aim of this research is to establish the feasibility of this technique for use in detecting neutrinos from the p-p and Be-7 reactions in the sun. In these experiments we have seen the first detection of 5.5 MeV (alpha) particles via evaporation from a bath of superfluid helium. An (alpha) particle excites phonons and rotons in the liquid helium, and these excitations are sufficiently energetic to evaporate helium atoms when they reach the free surface of the liquid. The evaporated atoms are detected calorimetrically by a thin wafer suspended above the liquid. The approximate overall efficiency of this process has been determined and we compare the experimental results with expectations. We have also been able to detect evaporation induced by a flux of gamma rays from a Cs-137 source. Preparations made for new experiments are also discussed.

  3. Penning ionization of alkali metals by metastable helium and neon

    International Nuclear Information System (INIS)

    The rate coefficients for Penning ionization of the alkali metals sodium, potassium, rubidium, and cesium by the 23S1 metastable state of helium and of rubidium and cesium by the 33P1 metastable state of neon were measured in a stationary afterglow using optical absorption to monitor the metastable atom population. The cross sections for these reactions were obtained under the assumption that the cross section is velocity independent for thermal velocities. The results for helium suggest that collisions in which the metastable energy is near a core-excited state of the alkali (a bound state within the continuum) are more efficient in ionizing the alkali. Since the neon metastable level lies within the core-excited spectrum of both rubidium and cesium, the neon results do not verify or refute this suggestion. For 23S1 helium, the measured rate coefficients in units of 10-exclamation] cm3s-1 are 4.5 +/- 0.9 for cesium, 12.0 +/- 2.4 for rubidium, 7.7 +/- 1.5 for potassium, and 4.5 +/- 0.9 for sodium. The corresponding cross sections in units of 10-16 cm2 are 34 +/- 7 for cesium, 93 +/- 18 for rubidium, 55 +/- 10 for potassium, and 33 +/- 6 for sodium. For 33P1 neon, the rate coefficients in units of 10-10 cm3s-1 are 1.5 +/- 0.3 for cesium and 2.8 +/- 0.6 for rubidium with cross sections in units of 10-16 cm2 of 24 +/- 5 for cesium and 43 +/- 9 for rubidium. The alkali number of density ranged up to 1012cm-3. The helium pressure was about 10 Torr and that of neon about 1 Torr

  4. Design of subcooled helium II refrigerator with helium-3 cold compressor

    International Nuclear Information System (INIS)

    This paper will study the possibility of a He II refrigerator made up of three cold compressors by making use of helium-3 characteristics. This system is compact enough to fit inside a small cold box, so it can be easily connected with an existing helium-4 refrigerator. The authors designed the compressors, calculated the He II cooling capacity, 4.4 K refrigeration load, required inventory of helium-3, and Carnot efficiency. Though helium-3 is expensive, the required inventory of helium-3 to be filled inside this He II refrigerator was calculated to be small enough to prove practicality of constructing this refrigerator

  5. The consequences of helium production on microstructural development in isotopically tailored ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S. [Pacific Northwest Lab., Richland, WA (United States)

    1996-10-01

    A series of alloys have been made adding various isotopes of nickel in order to vary the production of helium during irradiation by a two step nuclear reaction in a mixed spectrum reactor. The alloys use a base composition of Fe-12Cr with an addition of 1.5% nickel, either in the form of {sup 60}Ni which produces no helium, {sup 59}Ni which produces helium at a rate of about 10 appm He/dpa, or natural nickel ({sup Nat}Ni) which provides an intermediate level of helium due to delayed development of {sup 59}Ni. Specimens were irradiated in the HFIR at Oak Ridge, TN to {approx}7 dpa at 300 and 400{degrees}C. Microstructural examinations indicated that nickel additions promote precipitation in all alloys, but the effect appears to be much stronger at 400{degrees}C than at 300{degrees}C. There is sufficient dose by 7 dpa (and with 2 appm He) to initiate void swelling in ferritic/martensitic alloys. Little difference was found between response from {sup 59}Ni and {sup Nat}Ni. Also, helium bubble development for high helium generation conditions appeared to be very different at 300 and 400{degrees}C. At 300{degrees}C, it appeared that high densities of bubbles formed whereas at 400{degrees}C, bubbles could not be identified, possibly because of the complexity of the microstructure, but more likely because helium accumulated at precipitate interfaces.

  6. Contribution to the experimental study of the polarized liquid helium-3

    International Nuclear Information System (INIS)

    Spin-polarized liquid helium-3 is prepared by laser optical pumping in low magnetic field and at room temperature, prior to fast liquefaction of the polarized sample. The use of a new helium-3 cryostat enabled us to obtain liquid helium-3 with polarization rates up to 25 % at well-stabilized temperatures (around 0.5 K). We could thereby study the effect of nuclear polarization on liquid-vapour equilibrium, and particularly on the saturated vapour pressure. Very sensitive capacitive gauges were developed. We estimated (to first order in M2) the expected effects when the polarization M is suddenly destroyed. These effects were experimentally observed in helium-3/helium-4 mixtures, in pure helium-3, only a transient increase in pressure has been recorded. We then describe in a third part a preliminary experiment which aimed at determining the longitudinal relaxation time T1 in mixtures. Relaxation on the walls is efficiently reduced by a cesium coating and T1s of order 20 minutes were observed. A careful determination of the helium-3 concentration in the liquid phase was made. Finally we studied the effects of dipolar field on transverse polarisation decay in our strongly polarized samples. We observed the free precession of polarization after a NMR pulse, and analysed in detail its decay time constant as a function of different parameters. This time constant drastically varied with the tipping angle, an effect which could be linked to NMR dynamical instabilities. (author)

  7. Dependence of vacancy concentration on morphology of helium bubbles in oxide ceramics

    International Nuclear Information System (INIS)

    Since the formation of helium bubbles degrades swelling property and thermal conductivity of minor actinide-containing mixed oxide (MA-MOX) fuel, it is essential to understand the conditions of the bubble formation. In order to examine the dependence of vacancy concentration on morphology of helium bubbles, helium was infused into (Zr,Fe)O2-x. The oxygen vacancy concentration was controlled by addition of solute Fe3+ into ZrO2. Helium was infused by hot isostatic pressing. The helium-infused specimens were observed by field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM). In addition, X-ray fluorescence, X-ray diffraction analysis, conversion electron yield–X-ray absorption near-edge structure and FE-SEM/EDX (energy dispersive X-ray) analyses were also made to interpret the results of microstructure observations. As a result of the helium infusion treatment, numerous 0.5–10 nm bubbles were observed and its number density clearly depended on oxygen vacancy concentration. On the other hand, sizes of the helium nano-bubbles in all specimens were almost constant. (author)

  8. Helium effects on creep properties of Fe–14CrWTi ODS steel at 650 °C

    International Nuclear Information System (INIS)

    In the present paper, the effects of helium on creep properties of Fe–14CrWTi ODS steel were studied by in-beam and post He-implantation creep tests. In-situ creep was performed in an in-beam creep device under uniaxial tensile stresses from 350 to 370 MPa during homogeneous helium implantation. Helium ions of energies varying from 0 to 25 MeV were implanted at a rate of 6 × 10?3 appm/s (corresponding to a displacement dose rate of 1.5 × 10?6 dpa/s). The average temperature was controlled to 650 °C within ±2 °C. In addition, post He-implantation creep tests were conducted at 650 °C as well. Subsequently, fracture surfaces and helium bubble evolution were studied in detail by SEM and TEM observations, respectively. Preliminary creep results show that helium slightly shortens the creep life time of ODS steel at 650 °C. Fracture surfaces of reference as well as implanted specimens, show areas with various grades of deformation. Areas of highest deformation can be interpreted as necking, while areas of low deformation show in helium implanted specimens a more granular structure. The results are discussed in terms of possible embrittlement of ODS steels by helium

  9. Helium-cooled lithiuim compound suspension blanket concept for ITER

    International Nuclear Information System (INIS)

    This blanket concept uses a dilute suspension of fine solid breeder particles (Li2O, LiAlO2, or Li4SiO4) in a carrier gas (He) as the coolant and the tritium breeding stream. A small fraction of this stream is processed outside the reactor for tritium recovery. The blanket consists of a beryllium multiplier and carbon/steel reflector. A steel clad is used for all materials. A carbon reflector is employed to reduce the beryllium thickness used in the blanket for a specific tritium breeding ratio. The breeder particle size has to exceed few microns (?2 microns) to avoid sticking problems on the cold surfaces of the heat exchanger. The helium gas pressure is in the range of 2 to 3 MPa to carry the blanket and the heat exchanger loop. The solid breeder concentration in the helium stream is 1 to 5 volume percent. A high lithium-6 enrichment is used to produce a high tritium breeding ratio and to reduce the breeder concentration in the helium gas. At a lithium-6 enrichment of 90%, the local tritium breeding ratio is 2.03 based on a one-dimensional poloidal model. The total thickness of the helium stream is only 4 cm out of the 50 cm total blanket thickness. The blanket uses a 35 cm of beryllium for neutron multiplication. A simple multi-layer design is employed where the blanket sector has the helium coolant flowing in the poloidal direction. The blanket concept has several unique advantages which are very beneficial for fusion reactors including ITER. 10 refs., 2 tabs

  10. Time variations of cosmic-ray helium isotopes

    Science.gov (United States)

    Picot-Clemente, Nicolas

    2013-04-01

    The Balloon-born Experiment with Superconducting magnet Spectrometer (BESS) is a Japan-U.S. program that carried out 11 successful flights from 1993 to 2007. The BESS instrument includes various particle detectors, such as plastic scintillator hodoscopes and a central jet-type drift chamber surrounded by a superconducting solenoid magnet. Measurements provided by these detectors allow precise identification of cosmic-ray helium isotopes. The long-duration flight of the BESS-Polar I instrument, about 8.5 days over Antarctica in 2004, allows measurements of time variations of isotope fluxes for the first time. The time variation of the helium isotope flux is presented for rigidities from 1.2 GV to 2.5 GV, and the results are compared with previously reported proton data and neutron monitor data.

  11. Helium-cooled high temperature reactors

    International Nuclear Information System (INIS)

    Experience with several helium cooled reactors has been favorable, and two commercial plants are now operating. Both of these units are of the High Temperature Graphite Gas Cooled concept, one in the United States and the other in the Federal Republic of Germany. The initial helium charge for a reactor of the 1000 MW(e) size is modest, approx.15,000 kg

  12. An easy vacuum sealing under superfluid helium

    International Nuclear Information System (INIS)

    The article describes the sealing property of a vacuum sealer under cryogenic cooling, discusses the measures for improving the sealing property. Some experiments were carried out by applying the small-bore sealer under superfluid helium gas, and it has been successfully applied in the apparatus of superfluid helium under atmospheric pressure

  13. 30 CFR 256.11 - Helium.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false Helium. 256.11 Section 256.11 Mineral Resources... Helium. (a) Each lease issued or continued under these regulations shall be subject to a reservation by the United States, under section 12(f) of the Act, of the ownership of and the right to extract...

  14. LOX Tank Helium Removal for Propellant Scavenging

    Science.gov (United States)

    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).

  15. Helium Speech: An Application of Standing Waves

    Science.gov (United States)

    Wentworth, Christopher D.

    2011-01-01

    Taking a breath of helium gas and then speaking or singing to the class is a favorite demonstration for an introductory physics course, as it usually elicits appreciative laughter, which serves to energize the class session. Students will usually report that the helium speech "raises the frequency" of the voice. A more accurate description of the…

  16. Free convection heat transfer to supercritical helium

    International Nuclear Information System (INIS)

    The study of cryogenic free convective heat transfer from a sphere to supercritical helium is reported. The free convective heat transfer coefficient has been measured within the region of 4.2 to 25 K and 3 to 35 atmospheres. Measurements were made for sphere to helium temperature difference of 0.1 to 7 K. (author)

  17. Post-giant evolution of helium stars

    International Nuclear Information System (INIS)

    Extremely hydrogen deficient stars (helium stars and R Coronae Borealis variables) are considered to be remnants of double shell source stars (of the asymptotic giant branch). The evolution of stars with a condensed C/O-core and a helium envelope is followed numerically from the red giant stage to the white dwarf domain, crossing the regions of R CrB- and helium stars (so far analyzed). They have typically masses M/M(sun) = 0.7 and luminosities log L/L(sun) = 4.1. The time for crossing the helium star domain is some 103 years. The corresponding times in the R CrB-region amounts up to several 104 years. The lower limit of the death rate of helium stars is estimated to be 4 x 10-14pc-3yr-1. This value is only a factor of ten lower than the birth rate of all non-DA white dwarfs. It is therefore possible that the helium stars are the precursors of helium rich white dwarfs. As a consequence, a significant fraction of all stars which end their lives as white dwarfs should pass through the helium star phase. (orig.)

  18. Effect of mobile helium on void nucleation

    International Nuclear Information System (INIS)

    A revised model of the effect of mobile helium on void nucleation, during irradiation, is presented. Simultaneous solutions of the reaction rate equations for the steady state concentration of defects are obtained. These results are used to calculate point-defect and helium fluxes. Steady-state void nucleation rates are calculated in the temperature range 300-6000C. (B.D.)

  19. Adsorption and desorption of helium in aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Beamish, John; Herman, Tobias

    2003-05-01

    We have studied the adsorption and desorption of helium in a 95% porosity aerogel. The helium density in the aerogel was directly measured with a capacitive technique, while the pressure and bulk helium density were measured with in situ capacitive gauges. Thermal response is slow in aerogels, so we used a thin sample to minimize the time constant. The combination of high resolution and rapid equilibration allowed us to study the capillary condensation of helium, which in aerogels occurs very close to the bulk saturation pressure. We saw hysteresis between filling and emptying of the pores, even for very slow rates. The hysteresis becomes smaller as the critical temperature is approached. We discuss whether true two phase coexistence can be observed in the helium-aerogel system.

  20. The Hottest Horizontal-Branch Stars in Omega Centauri: Late Hot Flasher vs. Helium Enrichment

    Science.gov (United States)

    Moehler, S.; Dreizler, S.; Lanz, T.; Bono, G.; Sweigart, A V.; Calamida, A.; Monelli, M.; Nonino, M.

    2007-01-01

    UV observations of some massive globular clusters uncovered a significant population of very hot stars below the hot end of the horizontal branch (HB), the so-called blue hook stars. This feature might be explained either by the late hot flasher scenario here stars experience the helium flash while on the white dwarf cooling curve or by the helium-rich sub-population recently postulated to exist in some clusters. Spectroscopic analyses of blue hook stars in omega Cen and NGC 2808 support the late hot flasher scenario, but the stars contain much less helium than expected and the predicted C, N enrichment could not be verified from existing data. We want to determine effective temperatures, surface gravities and abundances of He, C, N in blue hook and canonical extreme horizontal branch (EHB) star candidates. Moderately high resolution spectra of stars at the hot end of the blue horizontal branch in the globular cluster omega Cen were analysed for atmospheric parameters (T(sub eff), log g) and abundances using LTE and Non-LTE model atmospheres. In the temperature range 30,000 K to 50,000 K we find that 37% of our stars are helium-poor (log nHe/nH less than -2), 49% have solar helium abundance within a factor of 3 (-1.5 less than or equal to log nHe/nH less than or equal to -0.5) and 14% are helium rich (log nHe/nH greater than -0.4). We also find carbon enrichment in step with helium enrichment, with a maximum carbon enrichment of 3% by mass. At least 30% of the hottest HB stars in omega Centauri show helium abundances well above the predictions from the helium enrichment scenario (Y = 0.42 corresponding to log nHe/nH approximately equal to -0.74). In addition the most helium-rich stars show strong carbon enrichment as predicted by the late hot flasher scenario. We conclude that the helium-rich HB stars in omega Cen cannot be explained solely by the helium-enrichment scenario invoked to explain the blue main sequence.

  1. Ground State Hyperfine Structure of Muonic Helium Atom

    CERN Document Server

    Krutov, A A

    2007-01-01

    The vacuum polarization and the nuclear structure corrections of orders alpha^5 and alpha^6 including the recoil effects are calculated in the hyperfine splitting of the ground state in muonic helium atom (mu e ^4_2He) by the perturbation theory. The obtained total numerical result Delta E^{hfs}=4464.539 MHz improves the previous calculations and is in the agreement with the experimental data.

  2. Compatibility of vanadium alloys with reactor-grade helium for fusion reactor applications

    International Nuclear Information System (INIS)

    Tests were conducted to determine the compatibility of vanadium alloys with reactor-grade helium and to define the helium gas chemistry requirements for fusion reactors, miniature tensile specimens of V-5Cr-5Ti. V-10Cr-5Ti, and V-12.5Cr-5 Ti were exposed in a once-through system to helium with 70 vppm-H2 (measured oxygen partial pressures of 10-12 atm) and bottle helium (measured oxygen partial pressures of -4 atm) between 500 and 700 degree C for up to 1008 h. The weight changes in the specimens were recorded. The helium-exposed specimens were tensile tested, and the effects of exposure on mechanical properties were assessed. Exposure between 500 and 700 degree C for 1008 h in He+70 vppm-H2 resulted in complete embrittlement of all the alloys in room temperature tensile tests. The fracture mode was primarily cleavage, probably caused by a hydrogen-induced shift in the ductile to brittle transition temperature (DBTT). Weight gains increased with temperature and were largest for the V-5Cr-5Ti alloy. Specimens exposed for 531 h between 500 and 700 degree C in bottle He exhibited two distinct fracture morphologies on the fracture surfaces. Brittle cleavage around the edges of specimens gave way to ductile dimpling in the center of the specimens. The brittle region around the periphery of the specimen is most likely the highest vanadium oxide. V2O5

  3. Determination of helium in beryl minerals

    International Nuclear Information System (INIS)

    In order to obtain the diffusion coefficients of helium in beryl and phenacite samples at various temperatures, helium leak rates were measured in these minerals at these temperatures. Mass spectrometry (MS) was used to obtain helium leak rates and the gas flow was plotted against time. The gas quantity determined by MS was first obtained at various temperatures until no helium leak rate was detected. After that, these samples were irradiated with fast neutrons to produce helium which was measured again. This procedure was used to estimate the experimental error. The quantity of helium produced by interaction of gamma radiation with beryl minerals was theoretically calculated from the amount of thorium-232 at the neighbourhood of the samples. The quantity of helium produced in the minerals due to uranium and thorium decay was calculated using the amount of these heavy elements, and the results were compared with the amounts determined by MS. The amount of potassium-40 was determined in order to derive the quantity of argonium-40, since some workers found argonium in excess in these minerals. The quantity of helium in the beryl samples (s) was determined in the center and in the surface of the samples in order to obtain informations about the effectiveness of the Be(?, ?) He reaction. Beryl and phenacite minerals were choosen in this research since they are opposite each other with respect to the helium contents. Both have beryllium in their compositon but beryl hold a large amount of helium while phenacite, in spite of having about three times more beryllium than beryl, do not hold the gas. (author)

  4. Helium transport and behavior of ELMy H-mode plasmas on JT-60U

    International Nuclear Information System (INIS)

    Helium (He) transport and behavior have been investigated during ELMy (edge-localized mode) H-mode using a helium beam in JT-60U. Helium transport coefficients in the ELMy H-mode plasmas (H=1.5) are found to be DA=1-2 m2/s and CV=1.0-1.5 when a neutral beam of 60 keV helium atoms is used for a source of central fuelling, and DA=1 m2/s and CV=1.0-1.5 when a short pulse He gas puff is used as peripheral fuelling. No helium accumulation is observed during ELMy H-mode. The behavior of helium in the divertor region has been studied with divertor spectroscopic measurement and compared with that in the main plasma. The He recycling flux in the divertor during ELMy H-mode is about one order of magnitude less than during L-mode with the same level of He gas fuelling. ((orig.))

  5. A comparison of neon versus helium ion beam induced deposition via Monte Carlo simulations.

    Science.gov (United States)

    Timilsina, Rajendra; Smith, Daryl A; Rack, Philip D

    2013-03-22

    The ion beam induced nanoscale synthesis of PtCx (where x ? 5) using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPt(IV)Me3) precursor is investigated by performing Monte Carlo simulations of helium and neon ions. The helium beam leads to more lateral growth relative to the neon beam because of its larger interaction volume. The lateral growth of the nanopillars is dominated by molecules deposited via secondary electrons in both the simulations. Notably, the helium pillars are dominated by SE-I electrons whereas the neon pillars are dominated by SE-II electrons. Using a low precursor residence time of 70 ?s, resulting in an equilibrium coverage of ?4%, the neon simulation has a lower deposition efficiency (3.5%) compared to that of the helium simulation (6.5%). At larger residence time (10 ms) and consequently larger equilibrium coverage (85%) the deposition efficiencies of helium and neon increased to 49% and 21%, respectively; which is dominated by increased lateral growth rates leading to broader pillars. The nanoscale growth is further studied by varying the ion beam diameter at 10 ms precursor residence time. The study shows that total SE yield decreases with increasing beam diameters for both the ion types. However, helium has the larger SE yield as compared to that of neon in both the low and high precursor residence time, and thus pillars are wider in all the simulations studied. PMID:23449368

  6. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  7. Helium gas bubble trapped in liquid helium in high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bai, H., E-mail: bai@magnet.fsu.edu; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States)

    2014-03-31

    High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32?T, 32?mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32?T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40?mm and an outer diameter of 140?mm was fabricated and tested in a resistive magnet providing a background field of 15?T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5?T at a current of 200?A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

  8. Optical Forces on Metastable Helium

    Science.gov (United States)

    Corder, Christopher Scott

    Optical forces using lasers allow precise control over the motion of atoms. The bichromatic optical force (BF) is unique in its large magnitude and velocity range, arising from the absorption and stimulated emission processes. These properties were used to transversely collimate a beam of metastable helium (He*) using the 23S - 23P transition. The collimation created a very bright beam of He*, allowing experiments of neutral atom lithography. The He* beam was used to pattern material surfaces using a resist-based lithography technique, where the pattern was determined by either mechanical or optical masks. The optical masks produced features with a separation of half the wavelength of the light used. Patterning was successfully demonstrated with both IR and UV optical masks. The etched pattern resolution was ˜ 100 nm and limited by the material surface. Further experiments were performed studying the ability of the bichromatic force to cool. The finite velocity range of the BF allows estimation of a characteristic cooling time which is independent of the excited state lifetime, only depending on the atomic mass and optical transition energy. Past experiments, including the helium collimation used for neutral atom lithography, have demonstrated that the BF can collimate and longitudinally slow atomic beams, but required long interaction times that included many spontaneous emission (SE) events. The effect of SE can be mitigated, and is predicted to not be necessary for BF cooling. Since the BF cooling time is not related to the excited state lifetime, a transition can be chosen such that the cooling time is shorter than the SE cycle time, allowing direct laser cooling on atoms and molecules that do not have cycling transitions. Experiments using the helium 2 3S-3P transition were chosen because the BF cooling time (285 ns) is on the order of the average SE cycle time (260 ns). Numerical simulations of the experimental system were run predicting compression of the atomic velocity distribution. Our experimental results demonstrate the stimulated nature of the force through many atomic recoils from the light in less than one SE cycle time. A large range of the atomic velocity distribution is accelerated and accumulates at the velocity limit of the force. This accumulation results in an increase in the velocity space density, demonstrating cooling.

  9. Simulation study on retention and reflection from tungsten carbide under high fluence of helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Ono, T.; Yamamura, Y. [Okayama University of Science, Okayama (Japan); Kawamura, T. [Chubu University, Kasugai, Aichi (Japan); Kenmotsu, T. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2000-08-01

    We have studied, by a Monte Carlo simulation code ACAT-DIFFUSE, the fluence-dependence of the amount of retained helium atoms in tungsten carbide at room temperature under helium ion bombardment. The retention behavior may be understood qualitatively in terms of irradiation-dependent diffusion coefficient assumed and range. The emission processes from tungsten carbide under helium ion irradiation derived were compared with each other. We have discussed the retention curves for incident energy of 5 keV at incident angles of 0deg and 80deg and of 500 eV at 0deg. The energy spectra of helium atoms reflected from tungsten carbide for incident energy of 500 eV at 0deg and 80deg were compared with those from graphite and tungsten. (author)

  10. Evaluation of helium impurity impacts on Spent Nuclear Fuel project processes (OCRWM)

    Energy Technology Data Exchange (ETDEWEB)

    SHERRELL, D.L.

    1999-09-21

    This document identifies the types and quantities of impurities that may be present within helium that is introduced into multi-canister overpacks (MCO)s by various SNF Project facilities, including, but not limited to the Cold Vacuum Drying (CVD) Facility (CVDF). It then evaluates possible impacts of worst case impurity inventories on MCO drying, transportation, and storage processes. Based on the evaluation results, this document: (1) concludes that the SNF Project helium procurement specification can be a factor-of-ten less restrictive than a typical vendor's standard offering (99.96% pure versus the vendor's 99.997% pure standard offering); (2) concludes that the CVDF's current 99.5% purity requirement is adequate to control the quality of the helium that is delivered to the MCO by the plant's helium distribution system; and (3) recommends specific impurity limits for both of the above cases.

  11. Helium distribution in a mantle shear zone from the Josephine Peridotite

    Science.gov (United States)

    Recanati, A.; Kurz, M. D.; Warren, J. M.; Curtice, J.

    2012-12-01

    A previous study of oceanic mylonites suggested that peridotite helium concentrations are correlated with the degree of high-temperature ductile deformation in the mantle. In order to test this result, this study combines helium measurements with characterization of the deformation state of harzburgite samples in a small (6 m width) ductile mantle shear zone from the Josephine Peridotite, Oregon, USA. All measurements were made by coupled in vacuo crushing and melting, demonstrating that most of the helium (>80%) resides within the solid phases rather than fluid or melt inclusions. The present study confirms the influence of deformation on helium contents, but only at the highest shear strain (?>20) are helium contents significantly higher. The highest helium concentration, by roughly a factor of two, is found in the center-most sample, which also has grain size reduction by a factor of ?4. Dislocations and sub-grain boundaries are present in all samples and do not correlate with helium concentrations. Mineralogy also appears to have a negligible influence in this shear zone, as modal mineralogy is relatively homogeneous, with all samples being harzburgites. These observations suggest that the increase in helium concentration is related to grain size reduction, with grain boundaries proposed as an additional storage site for helium in the mantle. The present data also characterize the isotopic composition of the Josephine Peridotite: 3He/4He=6.7±0.2 Ra (n=33, between 6.3 and 7.1 Ra). The presence of cosmogenic 3He in the matrix is indicated by the helium isotopic composition released by melting: 3He/4He=8.5±0.3 Ra (n=10; from 7.9 to 10.9). This corresponds to an exposure age of 10 Kyr, which is approximately concordant with the end of the last glacial maximum. Very little radiogenic helium is present in the samples, suggesting extremely low uranium and thorium contents ([U]melt infiltration are also important factors for understanding helium storage in the mantle.

  12. Buoyancy-Driven Natural Convection of Liquid Helium in an Electron Bubble Chamber

    International Nuclear Information System (INIS)

    A small liquid helium test chamber with 1.5 L active volume has been designed and constructed, to make the fundamental measurements of physical properties of electron bubble transports in liquid helium, aimed at developing a new cryogenic neutrino detector, using liquid helium as the detecting medium, for the detection of solar neutrinos. The test chamber is a double-walled cylindrical container equipped with five optical windows and ten high voltage cables. A LN2/LHe cryostat and a needle valve for vapor helium cooling are used to provide a 1.7?4.5 K low temperature environments for the test chamber. One of key issues for the cryogenic design and experimental sensitivity of electron bubble tracking is that of keeping a thermally uniform liquid helium bath. The external heat loads to the chamber will generate a buoyancy-induced convection of liquid helium, which will carry the electron bubbles and accelerate or decelerate their transportation and therefore must be reduced to the minimum, so that the slow motion of the electron bubbles will not be confused by this effect. This paper will present the computational simulation and analysis on thermal convection and uniformity of the test chamber

  13. Cryogenic Design and Operation of Liquid Helium in Electron Bubble Chamber

    International Nuclear Information System (INIS)

    We are developing a new cryogenic neutrino detector: electron bubble chamber, using liquid helium as the detecting medium, for the detection of low-energy neutrinos (<1 MeV), from the Sun. The program focuses in particular on the interactions of neutrinos scattering off atomic electrons in the detecting medium of liquid helium, resulting in recoil electrons which can be measured. We designed and constructed a small test chamber with 1.5L active volume to start the detector R and D, and performed experimental proofs of the operation principle. The test chamber is a stainless steel cylinder equipped with five optical windows and ten high voltage cables. To shield the liquid helium chamber against the external heat loads, the chamber is made of double-walled jacket cooled by a pumped helium bath and is built into a LN2/LHe cryostat, equipped with 80 K and 4 K radiation shields. A needle valve for vapor helium cooling was used to provide a 1.7?4.5 K low temperature environments. The paper gives an introduction to the liquid helium solar neutrino detector, presents the cryogenic design and operation of the small test chamber

  14. The Helium Cryogenic System for the ATLAS Experiment

    CERN Document Server

    Delruelle, N; Passardi, Giorgio; ten Kate, H H J

    2000-01-01

    The magnetic configuration of the ATLAS detector is generated by an inner superconducting solenoid and three air-core toroids (the barrel and two end-caps), each of them made of eight superconducting coils. Two separated helium refrigerators will be used to allow cool-down from ambient temperature and steady-state operation at 4.5 K of all the magnets having a total cold mass of about 600 tons. In comparison with the preliminary design, the helium distribution scheme and interface with the magnet sub-systems are simplified, resulting in a considerable improvement of the operational easiness and the overall reliability of the system at some expense of the operational flexibility. The paper presents the cryogenic layout and the basic principles for magnets cool-down, steady state operation and thermal recovery after a fast energy dump.

  15. Genetic changes in Mammalian cells transformed by helium cells

    Energy Technology Data Exchange (ETDEWEB)

    Durante, M.; Grossi, G. (Naples Univ. (Italy). Dipt. di Scienze Fisiche); Yang, T.C.; Roots, R. (Lawrence Berkeley Lab., CA (USA))

    1990-11-01

    Midterm Syrian Hamster embryo (SHE) cells were employed to study high LET-radiation induced tumorigenesis. Normal SHE cells (secondary passage) were irradiated with accelerated helium ions at an incident energy of 22 MeV/u (9--10 keV/{mu}m). Transformed clones were isolated after growth in soft agar of cells obtained from the foci of the initial monolayer plated postirradiation. To study the progression process of malignant transformation, the transformed clones were followed by monolayer subculturing for prolonged periods of time. Subsequently, neoplasia tests in nude mice were done. In this work, however, we have focused on karyotypic changes in the banding patterns of the chromosomes during the early part of the progressive process of cell transformation for helium ion-induced transformed cells. 26 refs., 5 figs., 2 tabs.

  16. Electrical heater for very-low pressure helium gas

    CERN Document Server

    Benda, V; Vuillierme, B

    1996-01-01

    Testing superconducting magnets for the Large Hadron Collider (LHC) in superfluid helium requires large-capacity refrigeration at 1.8K. At CERN, this is provided by a combination of a cold compressor and a set of warm vacuum pumps capable of handling up to 18g/s at 1 kPa suction pressure. The cold helium vapour, after the cold compressor, is warmed up from about 5K to ambient temperature in a 32 kW electrical heater. The device is designed to operate reliably at flow rates varying from 1 to 18g/s, inlet pressure of 1 kPa to 3 kPa, with pressure drop 100 Pa. Design and construction of the heater, completely realised at CERN, are presented, as well as measured performance. Some technological problems are discussed.

  17. 21 CFR 868.1640 - Helium gas analyzer.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Helium gas analyzer. 868.1640 Section 868.1640...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1640 Helium gas analyzer. (a) Identification. A helium gas analyzer is a device intended to measure the concentration of helium in a...

  18. Wetting Properties of Liquid Helium on Cesium

    Science.gov (United States)

    Ross, David J.

    The adsorption of helium onto cesium substrates has been examined over a range of temperatures extending from ~0.2 K to ~ 5.4 K. Both pure isotopes, ^3He and ^4He, have been used as well as mixtures with ^3He concentrations ranging from 0 to 1. Previous work has shown that ^4 He fails to wet cesium at temperatures lower than rm T_{w}~2 K, and that a line of prewetting transitions extends upward from the wetting transition on the vapor side of the bulk liquid-vapor coexistence line. The critical end point temperature of the prewetting line is ~ 2.5 K. The results presented here demonstrate that pure ^3He completely wets cesium at all temperatures. Additionally, the prewetting phase diagram has been determined for this isotope. In this case the prewetting line does not intersect the bulk liquid-vapor coexistence line as it does for ^4He. Instead it extrapolates to zero temperature on the vapor side of the bulk coexistence line. The critical end point temperature for the ^3He/cesium prewetting line is ~0.7 K. The ^3 He/cesium prewetting behavior does not exhibit any of the unusual characteristics that have been predicted by theory. The effect of ^3He impurities on the pure ^4He wetting transition has also been studied. Because of the ^3 He quasiparticle Andreev states at the ^4He liquid-vapor interface, the wetting transition becomes reentrant, with wetting at high and low temperatures and non-wetting at intermediate temperatures. The form of the T_{rm w} vs. X_3 phase diagram has been analyzed and shown to imply the existence of ^3 He quasiparticle states at the liquid-cesium interface which are similar to the Andreev states. Additionally, the adsorption of helium mixtures on cesium has been studied in the vicinity of bulk liquid phase separation. A wetting transition of the % ^4He rich liquid between the ^3 He rich liquid and the cesium substrate has been found with T_{w}~0.53 K. The surface phase transition line associated with this wetting transition is found to extend to both sides of the bulk coexistence line. On the ^3 He rich side it is prewetting line, and on the ^4He rich side it becomes a line of triple point induced dewetting transitions.

  19. Lightweight Liquid Helium Dewar for High-Altitude Balloon Payloads

    Science.gov (United States)

    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 evacuates the dewar vacuum space to provide the necessary thermal isolation. Liquid helium may then be transferred from the storage dewar into the bucket dewar to cool the telescope inside the bucket dewar. By splitting the functions of helium storage and in-flight thermal isolation, the parasitic mass associated with the dewar pressure vessel is eliminated to achieve factor-of-five or better reduction in mass. The lower mass allows flight on conventional scientific research balloons, even for telescopes 3 to 5 meters in diameter.

  20. Calculated Regenerator Performance at 4 K with HELIUM-4 and HELIUM-3

    Science.gov (United States)

    Radebaugh, Ray; Huang, Yonghua; O'Gallagher, Agnes; Gary, John

    2008-03-01

    The helium-4 working fluid in regenerative cryocoolers operating with the cold end near 4 K deviates considerably from an ideal gas. As a result, losses in the regenerator, given by the time-averaged enthalpy flux, are increased and are strong functions of the operating pressure and temperature. Helium-3, with its lower boiling point, behaves somewhat closer to an ideal gas in this low temperature range and can reduce the losses in 4 K regenerators. An analytical model is used to find the fluid properties that strongly influence the regenerator losses as well as the gross refrigeration power. The thermodynamic and transport properties of helium-3 were incorporated into the latest NIST regenerator numerical model, known as REGEN3.3, which was used to model regenerator performance with either helium-4 or helium-3. With this model we show how the use of helium-3 in place of helium-4 can improve the performance of 4 K regenerative cryocoolers. The effects of operating pressure, warm-end temperature, and frequency on regenerators with helium-4 and helium-3 are investigated and compared. The results are used to find optimum operating conditions. The frequency range investigated varies from 1 Hz to 30 Hz, with particular emphasis on higher frequencies.

  1. Helium leak testing (problems and trends)

    International Nuclear Information System (INIS)

    A simple calculation for the case of a refrigeration compressor shows how to specify the limit of acceptability in helium mass spectrometry testing. The most important techniques of leak tightness testing are outlined with their specific applications

  2. Helium cosmic ray flux measurements at Mars

    International Nuclear Information System (INIS)

    The helium energy spectrum in Martian orbit has been observed by the MARIE charged particle spectrometer aboard the 2001 Mars Odyssey spacecraft. The orbital data were taken from March 13, 2002 to October 28, 2003, at which time a very intense Solar Particle Event caused a loss of communication between the instrument and the spacecraft. The silicon detector stack in MARIE is optimized for the detection of protons and helium in the energy range below 100MeV/n, which typically includes almost all of the flux during SPEs. This also makes MARIE an efficient detector for GCR helium in the energy range of 50-150MeV/n. We will present the first fully normalized flux results from MARIE, using helium ions in this energy range

  3. Helium Find Thaws the Cold Fusion Trail.

    Science.gov (United States)

    Pennisi, E.

    1991-01-01

    Reported is a study of cold fusion in which trace amounts of helium, possible evidence of an actual fusion reaction, were found. Research methodology is detailed. The controversy over the validity of experimental results with cold fusion are reviewed. (CW)

  4. Helium Sensitivity in Oxygen Deficiency Measurement Equipment

    International Nuclear Information System (INIS)

    Most accelerators in operation today use liquid helium based superconducting technology in some capacity. Many of these facilities also use fixed and portable oxygen monitors to detect an oxygen deficient atmosphere were the helium to be accidentally released. When released, helium can expand 800 times its liquid volume. Recent helium spill tests at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) uncovered a fundamental flaw in certain types of oxygen deficiency monitoring equipment. The ensuing investigation found that the problem is endemic to a class of electrochemical oxygen sensors used throughout both the research and industrial communities. This paper describes the results of the Jefferson Lab investigation and steps taken to date to both solve the problem and inform the safety community at large

  5. Helium-Hydrogen Recovery System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Immense quantities of expensive liquefied helium are required at Stennis and Kennedy Space Centers for pre-cooling rocket engine propellant systems prior to filling...

  6. Gas turbine modeling for NPP with helium cooled reactor

    International Nuclear Information System (INIS)

    The performance analyzes of closed helium cycle for NPPs with high-temperature gas-cooled reactors was carried out. Air-turbine units and helium-turbine units were compared. Helium turbine features were particularized in comparison with conventional air turbines. Simulation results of gas turbine setting with helium as a working medium were presented. Problems concerning high economic efficiency advance of helium turbines were discussed

  7. The Helium Trimer with Soft-Core Potentials

    OpenAIRE

    Kievsky, A.; Garrido, Eduardo; Romero-Redondo, C.; BARLETTA, P.

    2011-01-01

    The helium trimer is studied using two- and three-body soft-core potentials. Realistic helium-helium potentials present an extremely strong short-range repulsion and support a single, very shallow, bound state. The description of systems with more than two helium atoms is difficult due to the very large cancellation between kinetic and potential energy. We analyze the possibility of describing the three helium system in the ultracold regime using a gaussian representation of a widely used rea...

  8. Study of helium diffusion, implanted at a cyclotron, in face-centered cubic metals: Au, Ag and Al

    International Nuclear Information System (INIS)

    Helium in metals is produced by nuclear reactions of energetic particles. In nuclear technology the interest on helium in metals is import, due to its production by (n, ?) reaction. Because helium has extremely low solubility in metals, the precipitation in the form of filled bubbles at elevated temperatures occurs, which have detrimental effects on mechanical properties and may limit the lifetime of structural components. One typical example is the high temperature embrittlement. The nucleation and growth of the bubbles strongly depends on the mobility of the helium. This work presents the study of helium diffusion in Au, Ag and Al at temperatures above room temperature. The helium created by (n, ?) reactions has been simulated by homogeneous alpha particles implantation in cyclotron, at room temperature, in specimens of thicknesses between 5 and 50 ?m and helium concentration between 10-3 to 10 ppm. After implantation, the specimens were dropped in a furnace in a UHV-chamber and the diffusion was measured by observing the He-release during linear and isothermal annealings. The occurence of free diffusion was comparing the dependence of release kinetics on helium concentration, sample thickness, time and heating rate to diffusion theory and is clearly separeted from agglomeration process. The diffusion constants of helium in Au, Ag and Al follow an Arrhenius behavior, with: Au:Do=10-1.0 cm2/s ?H=1.70eV Ag:D0=10-1.2cm2/s ?H=1.51eV Al:Do=10+0.5cm2/s ?H=1.40eV. The results are compared to self-diffusion and to the diffusion of other gases in these metals. Comparison with theoretical estimates favours the vacancy mechanism for helium diffusion in Au, Ag and Al. (author)

  9. Cosmogenic helium in a terrestrial igneous rock

    International Nuclear Information System (INIS)

    The author presents new helium isotopic measurements on samples from the Kula formation of Haleakala volcano (Hawaii) that are best explained by an in situ cosmogenic origin for a significant fraction of the 3He. Results from crushing and stepwise heating experiments, and consideration of the exposure age of the sample at the surface and the cosmic-ray fluxes strongly support this hypothesis. Although crustal cosmogenic helium has been proposed previously, this represents its first unambiguous identification in a terrestrial sample. (author)

  10. Wigner islands with electrons over helium

    OpenAIRE

    Rousseau, E; Ponarin, D.; Hristakos, L.; Varoquaux, E.; Avenel, O.; Mukharsky, Yu.

    2008-01-01

    We present here the first experimental study of Wigner islands formed by electrons floating over helium. Electrons are trapped electrostatically in a mesoscopic structure covered with a helium film, behaving as a quantum dot. By removing electrons one by one, we are able to find the addition spectrum, i.e. the energy required to add (or extract) one electron from the trap with occupation number $N$. Experimental addition spectra are compared with Monte Carlo simulations for ...

  11. Calculation of the resonant ionization of helium

    International Nuclear Information System (INIS)

    Autoionizing resonances in the compound system of an electron and a helium ion are observed in kinematically-complete ionization experiments for electrons on helium atoms. The differential cross section is calculated for comparison with these experiments in an equivalent-local form of the distorted-wave impulse approximation. Resonant scattering amplitudes are calculated by a six-state momentum-space coupled-channels method. 10 refs., 1 tab., 2 figs

  12. Helium pumping with liquid ring vacuum pump

    International Nuclear Information System (INIS)

    At first the main principles for operation and building of liquid ring pumps are remembered and an experiment is described which allowed to assess the performance data of such pumps when used to pump helium gas with oil. Although they have been designed to pump air with water the adaptation for helium is rather simple, the input power is slightly higher in the same flow and pressure conditions, but the limit of the succion pressure is lowered

  13. SUPERFLUID HELIUM: Visualization of quantized vortices

    Science.gov (United States)

    Bewley, Gregory P.; Lathrop, Daniel P.; Sreenivasan, Katepalli R.

    2006-06-01

    When liquid helium is cooled to below its phase transition at 2.172 K, vortices appear with cores that are only ångströms in diameter, about which the fluid circulates with quantized angular momentum. Here we generate small particles of solid hydrogen that can be used to image the cores of quantized vortices in their three-dimensional environment of liquid helium. This technique enables the geometry and interactions of these vortices to be observed directly.

  14. Thin helium film on a glass substrate

    OpenAIRE

    Boninsegni, Massimo

    2009-01-01

    We investigate by Monte Carlo simulations the structure, energetics and superfluid properties of thin helium-four films (up to four layers) on a glass substrate, at low temperature. The first adsorbed layer is found to be solid and "inert", i.e., atoms are localized and do not participate to quantum exchanges. Additional layers are liquid, with no clear layer separation above the second one. It is found that a single helium-three impurity resides on the outmost layer, not si...

  15. Electrons on the surface of liquid helium

    International Nuclear Information System (INIS)

    Spectroscopic techniques were used to study transitions of electrons between bound states in the potential well near a helium surface. The charge density distribution of electrons on the surface was independently obtained from electrical measurements. From the measurements, information was obtained both about the interaction of the bound state electrons with the surface of liquid helium and about local disorder in the positions of electrons on the surface

  16. Helium burning in moderate-mass stars

    OpenAIRE

    Weiss, Achim

    2011-01-01

    The evolution of low- and intermediate mass stars at the onset and during core helium burning is reviewed. Particular emphasis is laid on structural differences, which may allow to identify a star's nature and evolutionary phase in spite of the fact that it is found in a region of the Hertzsprung-Russell-Diagram objects from both mass ranges may populate. Seismic diagnostics which are sensitive to the temperature and density profile at the border of the helium core and outsi...

  17. The superfluid phases of helium 3

    International Nuclear Information System (INIS)

    This book reports on the superfluid phases of helium 3. Superfluid helium 3 is a test system for many of the most important ideas in modern theoretical physics and has, in addition, helped to shape understanding of neutron stars, anisotropic superconductors and even oxide high-Tc superconductors. The authors develop the theory of all aspects of the phases, from a brief history to up-to-date research on the subject

  18. Helium refrigeration considerations for ADS cryomodule design

    International Nuclear Information System (INIS)

    Accelerator-Driven Sub-Critical Systems and its application to utilization of Thorium for energy production are based on superconducting radio frequency (SRF) technology, which in turn depends on the helium refrigeration. The present accelerator technology operations for this application are centered on operating these SRF cavities at 2-K. This requires specialized helium refrigeration systems which are cost intensive to produce and to operate. Some of the cryogenic system design considerations for these challenging applications are discussed. (author)

  19. Cryogenic system for the Large Helical Device. The helium refrigerator/liquefier for Large Helical Device

    International Nuclear Information System (INIS)

    A large-scale helium refrigerator/liquefier has been developed to provide reliable and safe operation for the Large Helical Device (LHD). The refrigerator is required to satisfy four different types of cooling methods: forced-flow supercritical helium, a pool boiling method, two-phase helium flow and forced-flow low-temperature (40-80 K) helium gas. The forced-flow supercritical helium is widely used in modern large-scale superconducting magnets. This method requires a much more complex refrigeration system than does pool boiling because of the circulation of low-temperature helium within a very long cooling path. The overall refrigeration system is fairly complicated because of these multi-refrigeration requirements. As a matter of fact, it is not likely to find this type of refrigeration plant in the world. The helium refrigerator has a total refrigeration capacity of 5.65 kW at 4.4 K and 20.6 kW at 80 K and 650 l/h liquefaction. The refrigerator was designed to have high processing efficiency since the construction expense is much less than the operating cost. In order to achieve this, the refrigerator has two precooling cycles (300 to 80 K and 80 to 20 K) and has two turboexpanders running in parallel with different temperature levels at the cold end. To achieve a high mass flow rate in a low-temperature regime, eight screw-type compressors are operated at room temperature. There are two compressor groups, group A and group B, to reduce the overall work load. Each group consists of 1st and 2nd stage compression processes. The total mass flow rate becomes 960 g/s at 1.864 MPa. This article reviews the basic characteristics of a 10 kW class helium refrigerator/liquefier and a simple refrigeration cycle. (author)

  20. Experimental investigation and optimization of small-scale helium liquefaction with multi-cryocoolers

    Science.gov (United States)

    Xu, Dong; Gong, Linghui; Li, Laifeng; Xu, Xiangdong; Liu, Huiming; Huang, Rongjin

    2015-07-01

    Small-scale helium liquefiers using regenerative cryocoolers with cooling power up to 1.5 W at 4.2 K could be used to re-liquefy evaporated helium gas of small- and medium-sized cryogenic devices such as MEG and PPMS. A serial-parallel-path helium liquefier with a liquefaction rate of 83 Litres per day (L/d) using five 4 K G-M cryocoolers is developed, and has been applied to the Wuhan National High Magnetic Field Center (WHMFC) in China. Different from parallel-path helium liquefier, the helium gas is effectively, stepwise precooled by heat exchangers on multi-cold flanges, and thus the additional purifier and precooling coil heat exchangers on the thinner part of the cold head cylinder containing the 2nd stage displacer could be removed to simplify the construction. Through theoretical calculation and conclusive analysis, an optimum configuration is proposed and makes a reference to the design of serial-parallel-path helium liquefier with multi-cryocoolers.

  1. Helium release behavior on amorphous ZrV2 tritide films

    International Nuclear Information System (INIS)

    3He release behavior in amorphous ZrV2 tritide films was analysed systematically by thermal desorption method and static storage method. The results show that there are three helium desorption peaks with 597.3, 725.8 and I 146.6 K in the films, and the third desorption peak has the most amount of the released helium from the amorphous body. During the static storage time with 2423 d, release fraction (RF) of 3He atoms in the alloy films fluctuates within 10-5 magnitude and ascends linearly, and the release rate of the 3He atoms doesn't speed up, but can be affected seriously by storage temperature. Comparing with crystal ZrV2 tritide films, the storage helium property of amorphous ZrV2 tritide films is better. The above results also prove that the helium retention property of amorphous alloy is favorable, and it will help peoples to understand helium behavior of materials with a new point of view, and provide a new direction to research storage hydrogen materials with high helium retention. (authors)

  2. Cryosorption of helium on argon frost TFTR [Tokamak Fusion Test Reactor] neutral beamlines

    International Nuclear Information System (INIS)

    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 ? 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 2x10-5 torr from an initial value of 10-8 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. Study of heat transfer in superconducting cable electrical insulation of accelerator magnet cooled by superfluid helium

    International Nuclear Information System (INIS)

    Heat transfer studies of electrical cable insulation in superconducting winding are of major importance for stability studies in superconducting magnets. This work presents an experimental heat transfer study in superconducting cables of Large Hadron Collider dipoles cooled by superfluid helium and submitted to volume heat dissipation due to beam losses. For NbTi magnets cooled by superfluid helium the most severe heat barrier comes from the electrical insulation of the cables. Heat behaviour of a winding is approached through an experimental model in which insulation characteristics can be modified. Different tests on insulation patterns show that heat transfer is influenced by superfluid helium contained in insulation even for small volume of helium (2 % of cable volume). Electrical insulation can be considered as a composite material made of a solid matrix with a helium channels network which cannot be modelled easily. This network is characterised by another experimental apparatus which allows to study transverse and steady-state heat transfer through an elementary insulation pattern. Measurements in Landau regime (?T?10-5 to 10-3 K) and in Gorter-Mellink regime (?T>10-3 K) and using assumptions that helium thermal paths and conduction in the insulation are decoupled allow to determine an equivalent channel area (10-6 m2) and an equivalent channel diameter (25 ?). (author)

  4. Hydrogen and helium in the spectra of Type Ia supernovae

    CERN Document Server

    Lundqvist, Peter; Sollerman, Jesper; Kozma, Cecilia; Baron, E; Cox, Nick L J; Fransson, Claes; Leibundgut, Bruno; Spyromilio, Jason

    2013-01-01

    We present predictions for hydrogen and helium emission line luminosities from circumstellar matter around Type Ia supernovae (SNe Ia) using time dependent photoionization modeling. ESO/VLT optical echelle spectra of the SN Ia 2000cx were taken before and up to 70 days after maximum. We detect no hydrogen and helium lines, and place an upper limit on the mass loss rate for the putative wind of less than 1.3EE{-5} solar masses per year, assuming a speed of 10 km/s and solar abundances for the wind. In a helium-enriched case, the best line to constrain the mass loss would be He I 10,830 A. We confirm the details of interstellar Na I and Ca II absorption towards SN 2000cx as discussed by Patat et al., but also find evidence for 6613.56 A Diffuse Interstellar Band (DIB) absorption in the Milky Way. We discuss measurements of the X-ray emission from the interaction between the supernova ejecta and the wind and we re-evaluate observations of SN 1992A obtained 16 days after maximum by Schlegel & Petre. We find a...

  5. Thermal Quenching and Pressure Gradients in Solid Helium

    Science.gov (United States)

    Suhel, Abdul; Beamish, John

    2010-03-01

    Torsional oscillator measurements on solid ^4He show a frequency increase at low temperatures that suggests mass decoupling or ``non-classical rotational inertia'' (NCRI). The magnitude of the NCRI varies from about 0.02% to 20% in different oscillators, although the temperature dependence is essentially the same. The amount of mass which decouples appears to be larger when the helium is frozen and cooled rapidly. Annealing at high temperatures usually reduces the NCRI, with an accompanying drop in pressure, suggesting that defects are involved. We have built a cell to measure the temperature dependence of the pressure and the magnitude of pressure gradients in solid helium. The helium can be melted in a few seconds using a heater embedded in the crystal and can be refrozen and quenched to low temperature in about 10 seconds. From the maximum pressure differences in the cell, we infer a yield stress of order 0.1 bar for solid ^4He. The pressure gradients relax when the temperature is raised above about 0.5 K. We describe the temperature dependence of this annealing process.

  6. Helium-cooled lithium compound suspension blanket concept for ITER

    International Nuclear Information System (INIS)

    This blanket concept uses a dilute suspension of fine solid breeder particles (Li/sub 2/O, LiAlO/sub 2/, or Li/sub 4/SiO/sub 4/) in a carrier gas (He) as the coolant and the tritium breeding stream. A small fraction of this stream is processed outside the reactor for tritium recovery. The blanket consists of a beryllium multiplier and carbon/steel reflector. A steel clad is used for all materials. A carbon reflector is employed to reduce the the beryllium thickness used in the blanket for a specific tritium breeding ratio. The breeder particle size has to exceed a few microns (? 2 microns) to avoid sticking problems on the cold surfaces of the heat exchanger. The helium gas pressure is in the range of 2 - 3 MPa to carry the solid breeder particles through the blanket and the heat exchanger loop. The solid breeder concentration in the helium stream is 1 to 5 volume percent. A high lithium-6 enrichment is used to produce a high tritium breeding ratio and to reduce the breeder concentration in the helium gas. The main features, key technical issues, and design analyses of this blanket concept are summarized in this paper

  7. Lung Function Measurement with Multiple-Breath-Helium Washout System

    CERN Document Server

    Wang, Jau-Yi; Owers-Bradley, John; Mellor, Chris

    2011-01-01

    Multiple-breath-washout (MBW) measurements are regarded as a sensitive technique which can reflect the ventilation inhomogeneity of respiratory airways. Typically nitrogen is used as the tracer gas and is washed out by pure oxygen in multi-breath-nitrogen (MBNW) washout tests. In this work, instead of using nitrogen, helium is used as the tracer gas and a multiple-helium-breath-washout (MBHW) system has been developed for the lung function study. A commercial quartz tuning fork with a resonance frequency of 32768 Hz has been used for detecting the change of the respiratory gas density. The resonance frequency of the tuning fork decreases linearly with increasing density of the surrounding gas. Knowing the CO2 concentration from the infrared carbon dioxide detector, the helium concentration can be determined. Results from 12 volunteers (3 mild asthmatics, 2 smokers, 1 with asthma history, 1 with COPD history, 5 normal) have shown that mild asthmatics have higher ventilation inhomogeneity in either conducting o...

  8. Formation of Au and tetrapyridyl porphyrin complexes in superfluid helium.

    Science.gov (United States)

    Feng, Cheng; Latimer, Elspeth; Spence, Daniel; Al Hindawi, Aula M A A; Bullen, Shem; Boatwright, Adrian; Ellis, Andrew M; Yang, Shengfu

    2015-07-14

    Binary clusters containing a large organic molecule and metal atoms have been formed by the co-addition of 5,10,15,20-tetra(4-pyridyl)porphyrin (H2TPyP) molecules and gold atoms to superfluid helium nanodroplets, and the resulting complexes were then investigated by electron impact mass spectrometry. In addition to the parent ion H2TPyP yields fragments mainly from pyrrole, pyridine and methylpyridine ions because of the stability of their ring structures. When Au is co-added to the droplets the mass spectra are dominated by H2TPyP fragment ions with one or more Au atoms attached. We also show that by switching the order in which Au and H2TPyP are added to the helium droplets, different types of H2TPyP-Au complexes are clearly evident from the mass spectra. This study suggests a new route for the control over the growth of metal-organic compounds inside superfluid helium nanodroplets. PMID:26059415

  9. Separation of compressor oil from helium

    International Nuclear Information System (INIS)

    Compression of helium by an oil-sealed rorary screw compressor entrains as much as 4000 parts per million by weight of liquid and vapor oil impurities in the gas. The reduction below about 0.1 ppm for cryogenic applications is discussed. Oil seperation equipment designed for compressed air must be modified significantly to produce the desired results with helium. The main differences between air and helium filtration are described. A description of the coalescers is given with the continuous coalescing of liquid mist from air or other gas illustrated. Oil vapor in helium is discussed in terms of typical compressor oils, experimental procedure for measuring oil vapor concentration, measured volatile hydrocarbons in the lubricants, and calculated concentration of oil vapor in Helium. Liquid oil contamination in helium gas can be reduced well below 0.1 ppm by a properly designed multiple state coalescing filter system containing graded efficiency filter elements. The oil vapor problem is best attached by efficiently treating the oil to remove most of the colatiles before charging the compressor

  10. Sonic helium detectors in the Fermilab Tevatron

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Advanced helium magnetometer for space applications

    Science.gov (United States)

    Slocum, Robert E.

    1987-01-01

    The goal of this effort was demonstration of the concepts for an advanced helium magnetometer which meets the demands of future NASA earth orbiting, interplanetary, solar, and interstellar missions. The technical effort focused on optical pumping of helium with tunable solid state lasers. We were able to demonstrate the concept of a laser pumped helium magnetometer with improved accuracy, low power, and sensitivity of the order of 1 pT. A number of technical approaches were investigated for building a solid state laser tunable to the helium absorption line at 1083 nm. The laser selected was an Nd-doped LNA crystal pumped by a diode laser. Two laboratory versions of the lanthanum neodymium hexa-aluminate (LNA) laser were fabricated and used to conduct optical pumping experiments in helium and demonstrate laser pumped magnetometer concepts for both the low field vector mode and the scalar mode of operation. A digital resonance spectrometer was designed and built in order to evaluate the helium resonance signals and observe scalar magnetometer operation. The results indicate that the laser pumped sensor in the VHM mode is 45 times more sensitive than a lamp pumped sensor for identical system noise levels. A study was made of typical laser pumped resonance signals in the conventional magnetic resonance mode. The laser pumped sensor was operated as a scalar magnetometer, and it is concluded that magnetometers with 1 pT sensitivity can be achieved with the use of laser pumping and stable laser pump sources.

  12. Cosmic-Ray Proton and Helium Spectra from the First CREAM Flight

    CERN Document Server

    Yoon, Y S; Allison, P S; Bagliesi, M G; Beatty, J J; Bigongiari, G; Boyle, P J; Childers, J T; Conklin, N B; Coutu, S; DuVernois, M A; Ganel, O; Han, J H; Jeon, J A; Kim, K C; Lee, M H; Lutz, L; Maestro, P; Malinine, A; Marrocchesi, P S; Minnick, S A; Mognet, S I; Nam, S; Nutter, S; Park, I H; Park, N H; Seo, E S; Sina, R; Swordy, S; Wakely, S P; Wu, J; Yang, J; Zei, R; Zinn, S Y; 10.1088/0004-637X/728/2/122

    2011-01-01

    Cosmic-ray proton and helium spectra have been measured with the balloon-borne Cosmic Ray Energetics And Mass experiment flown for 42 days in Antarctica in the 2004-2005 austral summer season. High-energy cosmic-ray data were collected at an average altitude of ~38.5 km with an average atmospheric overburden of ~3.9 g cm$^{-2}$. Individual elements are clearly separated with a charge resolution of ~0.15 e (in charge units) and ~0.2 e for protons and helium nuclei, respectively. The measured spectra at the top of the atmosphere are represented by power laws with a spectral index of -2.66 $\\pm$ 0.02 for protons from 2.5 TeV to 250 TeV and -2.58 $\\pm$ 0.02 for helium nuclei from 630 GeV/nucleon to 63 TeV/nucleon. They are harder than previous measurements at a few tens of GeV/nucleon. The helium flux is higher than that expected from the extrapolation of the power law fitted to the lower-energy data. The relative abundance of protons to helium nuclei is 9.1 $\\pm$ 0.5 for the range from 2.5 TeV/nucleon to 63 TeV/...

  13. Simulation of the mantle and crustal helium isotope signature in the Mediterranean Sea using a high-resolution regional circulation model

    Science.gov (United States)

    Ayache, M.; Dutay, J.-C.; Jean-Baptiste, P.; Fourré, P. E.

    2015-08-01

    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 process. 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 terrigenic helium-3 and helium-4 by the submarine volcanic activity which occurs mainly at plate boundaries, and also addition of (mainly) helium-4 from the crust and sedimentary cover by ?-decay of uranium and thorium contained in various minerals. We present the first simulation of the terrigenic helium isotope distribution in the whole Mediterranean Sea, using a high-resolution model (NEMO-MED12). For this simulation we build a simple source function for terrigenic helium isotopes based on published estimates of terrestrial helium fluxes. We estimate a hydrothermal flux of 3.5 mol 3He yr-1 and a lower limit for the crustal flux at 1.6 10-7 mol 4He mol m-2 yr-1. In addition to providing constraints on helium isotope degassing fluxes in the Mediterranean, our simulations provide information on the ventilation of the deep Mediterranean waters which are useful for assessing NEMO-MED12 performance. 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.

  14. Helium and Neon in Comets

    Science.gov (United States)

    Jewitt, David

    1996-01-01

    Two comets were observed with EUVE in late 1994. Both comet Mueller and comet Borrelly are short-period comets having well established orbital elements and accurate ephemerides. Spectra of 40 ksec were taken of each. No evidence for emission lines from either Helium or Neon was detected. We calculated limits on the production rates of these atoms (relative to solar) assuming a standard isotropic outflow model, with a gas streaming speed of 1 km/s. The 3-sigma (99.7% confidence) limits (1/100,000 for He, 0.8 for Ne) are based on a conservative estimate of the noise in the EUVE spectra. They are also weakly dependent on the precise pointing and tracking of the EUVE field of view relative to the comet during the integrations. These limits are consistent with ice formation temperatures T greater than or equal to 30 K, as judged from the gas trapping experiments of Bar-Nun. For comparison, the solar abundances of these elements are He/O = 110, Ne/O = 1/16. Neither limit was as constraining as we had initially hoped, mainly because comets Mueller and Borrelly were intrinsically less active than anticipated.

  15. Advances in helium ion microscopy

    International Nuclear Information System (INIS)

    With the advent of a reliable high brightness ion source, utilizing helium (He) as the ion species, a new branch of microscopy has emerged. The promise of sub-nm focused probe sizes coupled with the unique He beam/sample interactions has led to a range of both high resolution imaging and high fidelity material modification applications. However, realizing the full potential of the He ion source is not without its challenges. Some of the difficulties are presented, along with a discussion of a systematic effort to overcome these issues. This work has resulted in the ability to routinely take images with an edge resolution of 0.35 nm or better. The nature of the He ion beam interaction with the sample makes possible numerous diverse applications, beyond the high resolution imaging already mentioned. A few of these will be highlighted, including imaging insulating samples, scanning transmission He ion microscopy, and material modification. Finally an extension of the high source brightness technology to utilizing neon (Ne) as the ion species is described. The source properties are given, along with a calculation of the expected probe size from such a Ne ion source and column.

  16. Pulsating Helium Atmosphere White Dwarfs

    Science.gov (United States)

    Provencal, Judith; Montgomery, Michael H.; Bischoff-Kim, Agnes; Shipman, Harry; Nitta, Atsuko; Whole Earth Telescope Collaboration

    2015-08-01

    The overwhelming majority of all stars currently on the main sequence as well as those from earlier generations will or have ended their stellar lives as white dwarf stars. White dwarfs are rich forensic laboratories linking the history and future evolution of our Galaxy. Their structure and atmospheric composition provide evidence of how the progenitors lived, how they evolved, and how they died. This information reveals details of processes governing the behavior of contemporary main sequence stars. Combined with their distribution in luminosity/temperature, white dwarfs strongly constrain models of galactic and cosmological evolution.GD358 is among the brightest (mv =13.7) and best studied of the pulsating white dwarfs. This helium atmoshere pulsator (DBV) has an extensive photometric database spanning 30 years, including nine multisite Whole Earth Telescope campaigns. GD358 exhibits a range of behaviors, from drastic changes in excited pulsation modes to variable multiplet splittings. We use GD358 as a template for an examination of the DBV class, combining photometric results with recent COS spectroscopy. The results present new questions concerning DB formation and evolution.

  17. Elastic properties of solid helium

    Science.gov (United States)

    Syshchenko, O.; Day, J.; Beamish, J.

    2009-04-01

    Following recent torsional oscillator measurements which appear to show the 'non-classical rotational inertia' which characterizes a supersolid, a number of experiments have searched for evidence of unusual behavior in other properties. We have developed a new technique for measuring the shear modulus of solid helium at low frequencies and small strains. In hexagonal close packed 4He, the shear modulus increases dramatically below 200 mK, the temperature range where decoupling is seen in torsional oscillators. The modulus anomaly is frequency independent, depends strongly on strain amplitude, and is very sensitive to 3He impurities. In these and other ways, the shear modulus closely mirrors the torsional oscillator behavior and it is clear that the two phenomena are closely related. We attribute the shear modulus effects to the elastic response of mobile dislocations and their pinning by 3He impurities at low temperatures. A question then arises: are the modulus increases responsible for the frequency changes seen in torsional oscillator experiments? The expected frequency shifts appear to be much too small to explain the apparent decoupling, nor can elastic effects explain the 'blocked annulus' results or the behavior in small pores. In order to clarify the relationship between the shear modulus and torsional oscillator behaviors, we have recently made modulus measurements on 3He, where no supersolid response is expected. Since dislocation motion depends on crystal structure it was important that these measurements be extended to the hexagonal close packed phase of 3He, not just the body centered cubic phase.

  18. Elastic properties of solid helium

    International Nuclear Information System (INIS)

    Following recent torsional oscillator measurements which appear to show the 'non-classical rotational inertia' which characterizes a supersolid, a number of experiments have searched for evidence of unusual behavior in other properties. We have developed a new technique for measuring the shear modulus of solid helium at low frequencies and small strains. In hexagonal close packed 4He, the shear modulus increases dramatically below 200 mK, the temperature range where decoupling is seen in torsional oscillators. The modulus anomaly is frequency independent, depends strongly on strain amplitude, and is very sensitive to 3He impurities. In these and other ways, the shear modulus closely mirrors the torsional oscillator behavior and it is clear that the two phenomena are closely related. We attribute the shear modulus effects to the elastic response of mobile dislocations and their pinning by 3He impurities at low temperatures. A question then arises: are the modulus increases responsible for the frequency changes seen in torsional oscillator experiments? The expected frequency shifts appear to be much too small to explain the apparent decoupling, nor can elastic effects explain the 'blocked annulus' results or the behavior in small pores. In order to clarify the relationship between the shear modulus and torsional oscillator behaviors, we have recently made modulus measurements on 3He, where no supersolid response is expected. Since dislocation motion depends on crystal structure it was important that these measurements be extended to the hexagonal close packed phase of 3He, not just the body centered cubic phase.

  19. Photoionization rates for helium: update

    CERN Document Server

    Sokó?, Justyna M

    2014-01-01

    The NIS He gas has been observed at a few AU to the Sun almost from the beginning of the space age. To model its flow an estimate of the loss rates due to ionization by solar extreme-ultraviolet (EUV) flux is needed. The EUV irradiance has been measured directly from mid 1990-ties, but with high temporal and spectral resolution only from 2002. Beforehand only EUV proxies are available. A new method of reconstruction of the Carrington rotation averaged photoionization rates for neutral interstellar helium (NIS He) in the ecliptic at 1 AU to the Sun before 2002 is presented. We investigate the relation between the solar rotation averaged time series of the ionization rates for NIS He at 1 AU derived from TIMED measurements of EUV irradiance and the solar 10.7 cm flux (F10.7) only. We perform a weighted iterative fit of a nonlinear model to data split into sectors. The obtained formula allows to reconstruct the solar rotation averages of photoionization rates for He between ~1947 and 2002 with an uncertainty ran...

  20. Influence of nitrogen impurities on an electron-excited helium atoms concentration in the self-sustained normal dc glow discharge at atmospheric pressure

    OpenAIRE

    Arkhipenko, Valery; Kirillov, Andrey; Simonchik, Leanid; Zgirouski, Siargey

    2004-01-01

    The influence of nitrogen impurities on the parameters of the self-sustained normal dc glow discharge at atmospheric pressure was studied. The concentrations of the low-excited helium atoms in states 2_1s, 2_1p, 2_3s and 2_3p were determined in the atmospheric pressure glow discharge in helium (99.98%He) and in helium with a nitrogen admixture. It was shown that the adding of nitrogen into helium (less 5%) leads to the increase of both interelectrode gap voltage and gas temp...

  1. Microstructural observation on helium injected and creep ruptured JPCA

    International Nuclear Information System (INIS)

    Detailed and quantitative TEM observation was performed on high temperature helium injected and creep ruptured JPCA to seek the prominent TiC distribution developed for suppression of helium embrittlement. Three different preinjection treatments were adopted for changing the TiC distribution. Considerable degradation in creep rupture strength by helium occurred in solution-annealed specimens, although there was much less effect of other treatments which included aging prior to injection. The concentration of helium at grain boundaries and the promotion of precipitation by helium during injection were responsible for the degradation. Therefore, the presence of TiC precipitates before helium introduction will help prevent degradation. On the other hand, the rupture elongation was reduced by helium after all treatments, although helium trapping by TiC precipitates in the matrix was successfully achieved. Consequently, the combined use of several methods may be necessary for further suppression of helium embrittlement. (orig.)

  2. Thermal evolution of helium in magnetron sputtered titanium films

    International Nuclear Information System (INIS)

    Helium-containing titanium films synthesized by magnetron sputtering method were investigated using thermal desorption spectrometry (TDS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Helium evolution behaviors under thermal treatment from room temperature to 1500 °C were characterized. Four peaks appeared in TDS at around 100, 420, 700, and 1250 °C were identified and attributed to helium desorption from the specimen surface, substitutional helium (helium atom in a vacancy), small HemVn clusters with different helium-to-vacancy ratios, and helium bubbles or voids, respectively. The helium evolution under thermal treatment composed of two coexisting and competing processes, where the faster process dominated in relevant temperature range, i.e. helium diffusion and release at low temperatures, and bubble or void formation at high temperatures. Three characteristic temperatures in TDS were identified in description of the phenomenon

  3. Elastic properties of solid helium

    Energy Technology Data Exchange (ETDEWEB)

    Syshchenko, O; Day, J; Beamish, J [Department of Physics, University of Alberta, Edmonton, AB, T6G 2G7 (Canada)], E-mail: beamish@phys.ualberta.ca

    2009-04-22

    Following recent torsional oscillator measurements which appear to show the 'non-classical rotational inertia' which characterizes a supersolid, a number of experiments have searched for evidence of unusual behavior in other properties. We have developed a new technique for measuring the shear modulus of solid helium at low frequencies and small strains. In hexagonal close packed {sup 4}He, the shear modulus increases dramatically below 200 mK, the temperature range where decoupling is seen in torsional oscillators. The modulus anomaly is frequency independent, depends strongly on strain amplitude, and is very sensitive to {sup 3}He impurities. In these and other ways, the shear modulus closely mirrors the torsional oscillator behavior and it is clear that the two phenomena are closely related. We attribute the shear modulus effects to the elastic response of mobile dislocations and their pinning by {sup 3}He impurities at low temperatures. A question then arises: are the modulus increases responsible for the frequency changes seen in torsional oscillator experiments? The expected frequency shifts appear to be much too small to explain the apparent decoupling, nor can elastic effects explain the 'blocked annulus' results or the behavior in small pores. In order to clarify the relationship between the shear modulus and torsional oscillator behaviors, we have recently made modulus measurements on {sup 3}He, where no supersolid response is expected. Since dislocation motion depends on crystal structure it was important that these measurements be extended to the hexagonal close packed phase of {sup 3}He, not just the body centered cubic phase.

  4. Full Scale Thermo-hydraulic Simulation of a Helium-Helium Printed Circuit Heat Exchanger

    International Nuclear Information System (INIS)

    In this paper, the thermo-hydraulic full scale simulation is performed to study the temperature distributions, thermal stress, pressure drop and outlet temperature in a Helium-Helium printed circuit heat exchanger (PCHE) in a VHTR simulate helium loop. The entire PCHE is composed of 40 stacks of rectangular shaped micro-channels for helium gas [type A] (inlet temperature, 400 .deg. C) and 40 stacks of semi-ellipse shaped micro-channels for helium [type B] (inlet temperature, 300 .deg. C). The experimental result is compared to that of computer simulation, COMSOL multi-physics software. The Helium-Helium PCHE is considered a prototype of the newly developed PCHE by Korea Atomic Energy Research Institute (KAERI). The full scale thermo-hydraulic simulation was successfully performed to obtain temperature distribution, pressure drop and thermal stress in 40 sets of flow channel stacks in a helium-helium printed circuit heat exchanger in a VHTR simulate helium loop. We obtained a quite similar temperature distribution with the 3D measured infrared temperature distribution. To our knowledge, this is the first full scale numerical study on the PCHE, which considers all microchannels, that the convection effect on the outside surfaces of the PCHE is applied. The very high-temperature reactor (VHTR) or high-temperature gas-cooled reactor(HTGR) is a fourth-generation nuclear power reactor that uses the ceramic coated fuel, TRISO, in which the fission gas does not leak even at temperatures higher than 1600 .deg. C. The VHTR necessarily requires an intermediate loop composed of a hot gas duct (HGD), an intermediate heat exchanger (IHX) and a process heat exchanger (PHE). The IHX is one of the important components of VHTR system because the IHX transfers the 950 .deg. C of high temperature massive heat to a hydrogen production plant or power conversion unit at high system pressure

  5. Development of small size Claude cycle helium refrigerator with micro turbo-expander

    International Nuclear Information System (INIS)

    In the field of small size helium refrigerators, need for a maintenance free and vibration free system is rapidly increasing, especially for the application to cryoelectronic devices such as NMR-CT and Josephson computers. To meet this need, we have been developing a Claude cycle helium refrigerator (5W at 4.5 K) with two-stage expansion micro-turbines. Other than the micro-turbines, compact size perforatedplate heat exchangers and a single-stage screw type compressor have been developed for the system. This paper describes design and test results of the major components of the system with an emphasis on the microturbine performance

  6. Helium liquefier-refrigerator and distribution system for the Large Coil Program Test Facility

    International Nuclear Information System (INIS)

    The Large Coil Program (LCP) has the objectives of obtaining and testing superconducting magnets of a size and in an environment that demonstrate feasibility of application for The Next Step (TNS). These magnets are to be in a toroidal array which may include from one to six magnets and are to be cooled by either pool boiling or forced convection of helium. The toroidal array will be housed in a large vacuum vessel measuring about 11 m in diameter and 11 m high. The magnets will be modified D-shaped coils, and will have a bore of 2.5 by 3.5 m. The program objectives require a versatile and sophisticated liquid helium supply and cryogenic distribution system to meet the test requirements. The liquid helium supply system consists of a high pressure gas storage system, a 1050-kW, two-stage compressor, a refrigerator coldbox capable of delivering helium at two thermodynamic states, and a 19,000-liter helium storage dewar with the associated piping and controls. The refrigerator built by CTI is designed to supply the experimental load with either supercritical helium at temperatures to approximately 3.5 K or as saturated liquid down to approximately 3.5 K. The compressor system is an oil-flooded rotary screw unit capable of operating to 0.5-atm suction pressure. The first and second compression stage sizes are 300 kW and 750 kW, respectively, and they may be used either independently or in tandem. The features of the refrigerator-liquefier will be described in this paper

  7. Curious Fluid Flows: From Complex Fluid Breakup to Helium Wetting

    Science.gov (United States)

    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 qualitative shape of the theory, but not its quantitative values, matches the data. The discrepancy between the experimental and theoretical Q values appears to be due to unaccounted for dissipation.

  8. TRANSPARENT HELIUM IN STRIPPED ENVELOPE SUPERNOVAE

    International Nuclear Information System (INIS)

    Using simple arguments based on photometric light curves and velocity evolution, we propose that some stripped envelope supernovae (SNe) show signs that a significant fraction of their helium is effectively transparent. The main pieces of evidence are the relatively low velocities with little velocity evolution, as are expected deep inside an exploding star, along with temperatures that are too low to ionize helium. This means that the helium should not contribute to the shaping of the main SN light curve, and thus the total helium mass may be difficult to measure from simple light curve modeling. Conversely, such modeling may be more useful for constraining the mass of the carbon/oxygen core of the SN progenitor. Other stripped envelope SNe show higher velocities and larger velocity gradients, which require an additional opacity source (perhaps the mixing of heavier elements or radioactive nickel) to prevent the helium from being transparent. We discuss ways in which similar analysis can provide insights into the differences and similarities between SNe Ib and Ic, which will lead to a better understanding of their respective formation mechanisms

  9. Synergistic effects in hydrogen-helium bubbles

    International Nuclear Information System (INIS)

    The detrimental effects of hydrogen and helium on structural materials undergoing irradiation are well documented, if not well understood. There is experimental evidence to suggest that a synergistic effect between the two elements exists, which results in increased damage when both are present. This situation is expected in the next generation of fusion and fission reactors, so a fundamental understanding of these synergistic interactions is needed to predict materials performance. We perform atomistic simulations of hydrogen and helium bubbles in body-centered cubic iron to determine the mechanism behind this effect. We first develop an interatomic potential suitable for describing the interactions between hydrogen and helium. Through analysis of the energetics and structure of these bubbles, we explain the observed synergy as a consequence of bubble growth through helium induced loop punching, aided by the presence of hydrogen, instead of as a direct interaction between hydrogen and helium. The hydrogen benefits from an increased area of free surface on which to bind. (paper)

  10. Closed-loop pulsed helium ionization detector

    International Nuclear Information System (INIS)

    In combination, a helium ionization detector and a closed-loop control system for pulsed operation of the helium ionization detector is described comprising: a helium ionization detector having an anode and cathode electrodes between which a helium carrier gas containing an ionizable component whose concentration is to be detected is introduced to be ionized to produce an ionization current therein which flows through the electrodes when a high voltage bias is applied between the electrodes; a high voltage pulser means for generating and applying selected amplitude high voltage bias pulses; a reference current generator means for generating a selected reference current corresponding to a desired average ionization current in the detector; an electrometer circuit means for generating an output signal at an output terminal that varies in inverse proportion to the change in ionization current in the detector; a switching pulse generating means responsive to the output signal of the electrometer circuit means for generating and applying the switching pulses to the high voltage pulser means at a frequency and a selected duty cycle which maintains a constant average ionization current flowing in the detector; means for sensing the amplitude of the output of the electrometer circuit means as an indication of the concentration of the ionizable component being detected by the helium ionization detector

  11. Helium release from radioisotope heat sources

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, D.E.; Early, J.W.; Starzynski, J.S.; Land, C.C.

    1984-05-01

    Diffusion of helium in /sup 238/PuO/sub 2/ fuel was characterized as a function of the heating rate and the fuel microstructure. The samples were thermally ramped in an induction furnace and the helium release rates measured with an automated mass spectrometer. The diffusion constants and activation energies were obtained from the data using a simple diffusion model. The release rates of helium were correlated with the fuel microstructure by metallographic examination of fuel samples. The release mechanism consists of four regimes, which are dependent upon the temperature. Initially, the release is controlled by movement of point defects combined with trapping along grain boundaries. This regime is followed by a process dominated by formation and growth of helium bubbles along grain boundaries. The third regime involves volume diffusion controlled by movement of oxygen vacancies. Finally, the release at the highest temperatures follows the diffusion rate of intragranular bubbles. The tendency for helium to be trapped within the grain boundaries diminishes with small grain sizes, slow thermal pulses, and older fuel.

  12. Liquid helium Dewar for one meter mirror testing

    Science.gov (United States)

    Sarver, George L., III

    1990-01-01

    The NASA Ames Research Center has developed a baseline design for a One Meter Cryogenic Optical Test Facility (OMF) incorporating a liquid helium Dewar for cryogenic optical testing of one-meter-class mirrors, principally the Space Infrared Telescope Facility (SIRTF) primary mirror. The primary requirements for the test facility are as follows: (1) the facility must be capable of interferometrically testing any mirror, positioned face-up or face-down, with a diameter less than 1.5 meters and a radius of curvature from 1.5 to 5.5 meters; (2) the facility must achieve and maintain, for 24 hours, a mirror temperature of 4 K with a maximum radiative heat load of less than 500 mW to the mirror, using stored liquid helium and liquid nitrogen; (3) the facility must include a vibration-isolated metrology structure between the test mirror and an external interferometer, and (4) the facility must be operated by two persons and a test, starting from the mounting of a mirror to the removal of a mirror, must be conducted within one week.

  13. Density decrease in vanadium-base alloys irradiated in the dynamic helium charging experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Galvin, T.M.; Smith, D.L. [Argonne National Laboratory, Chicago, IL (United States)

    1996-04-01

    Combined effects of dynamically charged helium and neutron damage on density decrease (swelling) of V-4Cr-4Ti, V-5Ti, V-3Ti-1Si, and V-8Cr-6Ti alloys have been determined after irradiation to 18-31 dpa at 425-600{degrees}C in the Dynamic helium Charging Experiment (DHCE). To ensure better accuracy in density measurement, broken pieces of tensile specimens {approx} 10 times heavier than a transmission electron microscopy (TEM) disk were used. Density increases of the four alloys irradiated in the DHCE were <0.5%. This small change seems to be consistent with the negligible number density of microcavities characterized by TEM. Most of the dynamically produced helium atoms seem to have been trapped in the grain matrix without significant cavity nucleation or growth.

  14. Accuracy of helium accumulation fluence monitor for fast reactor dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Chikara; Aoyama, Takafumi [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1998-03-01

    A helium (He) accumulation fluence monitor (HAFM) has been developed for fast reactor dosimetry. In order to evaluate the measurement accuracy of neutron fluence by the HAFM method, the HAFMs of enriched boron (B) and beryllium (Be) were irradiated in the Fast Neutron Source Reactor `YAYOI`. The number of He atoms produced in the HAFMs were measured and compared with the calculated values. As a result of this study, it was confirmed that the neutron fluence could be measured within 5 % by the HAFM method, and that met the required accuracy for fast reactor dosimetry. (author)

  15. Stopping Power of Solid Argon for Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Grauersen, O.; Hansen, Jens Leonhart; Sørensen, H.

    1981-01-01

    By means of the Rutherford-backscattering method, the stopping cross section of solid argon has been measured for 0.5–3 MeV helium ions to an accuracy of not, vert, similar3%. The results agree within the experimental accuracies with our earlier measurements for gaseous argon over the energy region studied. This proves that the gas/solid difference for argon predicted in recent stopping-power tabulations is significantly overestimated. With high-order Z1 correction terms included in the theoreti...

  16. Hyperfine Structure of S-States in Muonic Helium Ion

    OpenAIRE

    Martynenko, A. P.

    2007-01-01

    Corrections of orders alpha^5 and alpha^6 are calculated in the hyperfine splittings of 1S and 2S - energy levels in the ion of muonic helium. The electron vacuum polarization effects, the nuclear structure corrections and recoil corrections are taken into account. The obtained numerical values of the hyperfine splittings -1334.56 meV (1S state), -166.62 meV (2S state) can be considered as a reliable estimate for the comparison with the future experimental data. The hyperfin...

  17. Progress of helium refrigeration system for Wendelstein 7-X

    International Nuclear Information System (INIS)

    The helium refrigerator for the fusion experiment Wendelstein 7-X is required for cooling the superconducting coils, casings, supports and divertor cryo-vacuum pumps at 3.4 K in peak power and 3.9 K in standard operating modes. The refrigerator supplied by Linde Kryotechnik AG has an equivalent refrigeration power of 7 kW at 4.5 K. In the meantime the corresponding hardwares are installed and the commissioning is approaching towards completion. The preparations for the acceptance tests have begun. (author)

  18. The muonic helium lamb shift experiment

    International Nuclear Information System (INIS)

    Because of its high sensitivity on finite size effects of the nucleus, the measurement of the Lamb shift in exotic atoms has been on the wish-list of atomic and nuclear physics for a long time. Our previous experiment allowed to determine the proton radius with an order of magnitude higher precision compared to spectroscopic measurements of ordinary hydrogen. The successor experiment in muonic helium is currently performed at the Paul-Scherrer-Institute in Switzerland. Using a low energy muon beam line muons are stopped within low pressure helium gas, where exotic atoms are created. Here we measure the 2S-2P transition frequency of muonic helium illuminated by a pulsed TiSa-laser system pumped with a newly developed Yb-YAG thin disk laser. This measurement will ultimately improve the values of the charge radii of 3He+ and 4He+ by an order of magnitude.

  19. EFFECTS OF HELIUM PRECONDITIONING ON INTESTINAL ISCHEMIA AND REPERFUSION INJURY IN RATS.

    Science.gov (United States)

    Du, Lei; Zhang, Rongjia; Luo, Tianhang; Nie, Mingming; Bi, Jianwei

    2015-10-01

    Intestinal ischemia-reperfusion (I/R) injury can occur in clinical settings such as organ transplantation, cardiopulmonary bypass and trauma. The noble gas helium attenuates I/R injury in a number of animal organs and thus may offer a strategy for reducing I/R-induced intestinal injury in clinical settings. In the present study, we used four different helium preconditioning (HPC) profiles to investigate the potential beneficial effect of HPC on I/R-induced intestinal injury. Male Sprague-Dawley rats were pretreated with three cycles of air breathing for 5?min combined with three cycles of breathing a 70% helium:30% oxygen mixture for either 2, 5, 10, or 15?min, after which they were subjected to 60-min intestinal ischemia and 60-min reperfusion. Sixty minutes after reperfusion, the intestinal tissues of the variously treated rats were analyzed using histology, immunohistochemistry, terminal dUTP nick-end labeling staining, myeloperoxidase activity assay, Western blotting, and enzyme-linked immunosorbent assay for tumor necrosis factor ? and macrophage inflammatory protein 1?. Intestinal permeability was assayed by measuring fluorescein isothiocyanate-dextran release in blood samples. The results showed that the HPC profile consisting of three cycles of 10 or 15?min of helium breathing and three cycles of 5?min of air breathing reduced I/R-induced intestinal injury, cell apoptosis, and the inflammatory response. However, the 2- or 5-min helium breathing did not confer any protective effects. It seems that longer helium episodes should be used in HPC profiles designed to attenuate intestinal I/R injury. PMID:26052960

  20. Comparison of the yields in kaonic helium-3 and helium-4

    International Nuclear Information System (INIS)

    Full text: Kaonic helium is an exotic atom where a kaon replaces a shell electron, well suited for the study of the strong interaction at low energies. The strong interaction between the kaon and the nucleus affects the low-lying atomic states in the kaonic helium atom by causing a shift compared to its purely electromagnetic value. This shift can be measured with spectroscopic tools, which was recently performed by the SIDDHARTA experiment. Via a measurement of the X-ray transitions to the 2p level, the X-ray transitions in kaonic helium-3 and helium-4 (at different densities) were measured with a complex SDD detector system. With the data set of these measurements, the X-ray yields (i.e. the net production of characteristic X-rays) of the kaonic helium gases have been determined for the rst time. The absolute yields were obtained with inputs from a Monte Carlo simulation. Since the previous measurements on the kaonic helium X-ray transitions solely used liquid helium targets, these results give crucial information on theoretical calculations of the density dependence of the yields. The evaluation procedure and the results are going to be presented in detail. (author)

  1. Helium exhaust and forced flow effects with both-leg pumping in W-shaped divertor of JT-60U

    International Nuclear Information System (INIS)

    The W-shaped divertor of JT-60U was modified from inner-leg pumping to both-leg pumping. After the modification, the pumping rate was improved from 3% with inner-leg pumping to 5% with both-leg pumping in a divertor-closure configuration, which means both separatrixes close to the divertor slots. Efficient helium exhaust was realized in the divertor-closure configuration with both-leg pumping. A global particle confinement time of ?*He=0.4s and ?*He/?E=3 was achieved in attached ELMy H-mode plasmas. The helium exhaust efficiency with both-leg pumping was extended by 45% as compared with inner-leg pumping. By using central helium fueling with He-beam injection, the helium removal from the core plasma inside the internal transport barrier (ITB) in reversed shear plasmas in the divertor-closure configuration was investigated for the first time. The helium density profiles inside the ITB were peaked as compared with those in ELMy H-mode plasmas. In the case of low recycling divertor, it was difficult to achieve good helium exhaust capability in reversed shear plasmas with ITB. However, the helium exhaust efficiency was improved with high recycling divertor. Carbon impurity reduction was observed by the forced flow with gas puff and effective divertor pumping. (author)

  2. D0 Silicon Upgrade: Commissioning Test Results for D-Zero's Helium Refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Rucinski, Russ; /Fermilab

    1997-06-30

    The test objectives are: (1) Make liquid helium and measure refrigerator capacity; (2) Measure liquid helium dewar heat leak, transfer line heat leak, and liquid nitrogen consumption rates; (3) Operate all cryogenic transfer lines; (4) Get some running time on all components; (5) Debug mechanical components, instrumentation, DMACs user interface, tune loops, and otherwise shake out any problems; (6) Get some operating time in to get familiar with system behavior; (7) Revise and/or improve operating procedures to actual practice; and (8) Identify areas for future improvement. D-Zero's stand alone helium refrigerator (STAR) liquified helium at a rate of 114 L/hr. This is consistent with other STAR installations. Refrigeration capacity was not measured due to lack of a calibrated heat load. Measured heat leaks were within design values. The helium dewar loss was measured at 2 to 4 watts or 9% per day, the solenoid and VLPC helium transfer lines had a heat leak of about 20 watts each. The liquid nitrogen consumption rates of the mobile purifier, STAR, and LN2 subcooler were measured at 20 gph, 20 to 64 gph, and 3 gph respectively. All cryogenic transfer lines including the solenoid and visible light photon counter (VLPC) transfer lines were cooled to their cryogenic operating temperatures. This included independent cooling of nitrogen shields and liquid helium components. No major problems were observed. The system ran quite well. Many problems were identified and corrected as they came up. Areas for improvement were noted and will be implemented in the future. The instrumentation and control system operated commendably during the test. The commissioning test run was a worthwhile and successful venture.

  3. Spectral properties of endohedrally confined helium atom

    Science.gov (United States)

    Fang, Shuai-Shuai; Hao-Xue, Qiao

    2015-08-01

    Based on the B-spline basis method, the properties of the helium atom confined inside an endohedral environment, such as buckminster fullerene, are studied. In our calculations, the endohedral environment is a parabolic potential well. In this situation, the phenomenon of “mirror collapse” is exhibited for energy levels of a confined helium atom. The “giant resonance” of oscillator strength of the dipole transition emerges with the variation of depth of the confining well. The physical mechanisms of these phenomena are analyzed in this paper. Project supported by the National Natural Science Foundation of China (Grant No. 11274246.)

  4. Plastic dewar for pressurized superfluid helium

    International Nuclear Information System (INIS)

    Pressurized superfluid helium (He llsub(p)) was successfully produced in a Caudet type cryostat made from G-FRP without a nitrogen temperature shield. No superleak occurred and the efficiency of refrigeration remained constant over more than 20 cyclings between room and He llsub(p) temperatures. The plastic dewar was prepared to investigate hybrid cooling of an a.c. or pulsive superconducting magnet wound from a hollow type conductor; the inside of which is cooled by saturated superfluid helium (He llsub(s)) and the outside of which is simultaneously cooled by He llsub(p). The He llsub(s) does not circulate. (author)

  5. Helium mobility in advanced nuclear ceramics

    Science.gov (United States)

    Agarwal, S.; Trocellier, P.; Serruys, Y.; Vaubaillon, S.; Miro, S.

    2014-05-01

    The techniques of ion implantation and nuclear reaction depth profiling are used to measure helium migration parameters under thermal ageing in advanced nuclear ceramics such as TiC, ZrC and TiN. Helium release measurements and activation energy calculations have been carried out in the temperature range of 1000-1600 °C for time periods of 2 h. Activation energy values are obtained in the range 0.7-1.2 eV. Due to rare availability of stoichiometric samples, the trapping of He in native vacancies seems to affect the mobility of He. Blisters are observed only at the surface of ZrC on thermal annealing.

  6. Helium ion microscopy principles and applications

    CERN Document Server

    Joy, David C

    2013-01-01

    Helium Ion Microscopy: Principles and Applications describes the theory and discusses the practical details of why scanning microscopes using beams of light ions - such as the Helium Ion Microscope (HIM) - are destined to become the imaging tools of choice for the 21st century. Topics covered include the principles, operation, and performance of the Gaseous Field Ion Source (GFIS), and a comparison of the optics of ion and electron beam microscopes including their operating conditions, resolution, and signal-to-noise performance. The physical principles of Ion-Induced Secondary Electron (iSE)

  7. Pump performance requirement for the liquid helium orbital resupply tanker

    Science.gov (United States)

    Lee, J. H.; Ng, Y. S.

    1988-01-01

    The Liquid Helium Orbital Resupply Tanker (currently renamed to Superfluid Helium Tanker) will greatly enhance the lifetime of the space missions which require superfluid helium. The Superfluid Helium Tanker pump performance requirement is driven by the superfluid helium replenishment needs of the Space Infrared Telescope Facility (SIRTF). SIRTF is one of the space missions which will require on-orbit superfluid helium resupply in the 1990s. The Superfluid Helium Tanker will carry at least 10,000 L of superfluid helium and provide a minimum pump head of 170 torr (0 to 200 L/h) to cool SIRTF from 150 to 2 K. When the SIRTF tank starts to collect liquid, a minimum flow rate of 300 L/h with a pump head of 60 torr is required to fill the 4000-liter tank.

  8. Variational calculations of coupling of an incident helium atom to a slab of superfluid helium four

    International Nuclear Information System (INIS)

    In previous work on the interaction of single helium atoms with a slab of superfluid helium the authors found a large amplitude, dependent on the condensate fraction, for transmission with re-emission of a helium atom at the other side of the slab. Here they report a variational formulation of the problem which permits a time dependent calculation and which does not require any perturbation expansion. The variational principle involves a minimization of the expectation value of the square of the difference H-E. They will present preliminary results of a variational Monte Carlo calculation using a simple variational form for the wave function

  9. Nucleosynthesis in helium-enriched asymptotic giant branch models: Implications for Heavy Element Enrichment in ? Centauri

    Science.gov (United States)

    Karakas, Amanda; Shingles, Luke; Doherty, Carolyn Louise; Lattanzio, John; Fabiola Marino, Anna; Nataf, David

    2015-08-01

    Globular clusters are now known to harbour helium-rich stellar populations. While the stars we see today are all low mass, there were once stars of all mass ranges born in clusters with helium mass fractions up to Y ? 0.40. However, the effect of helium enrichment on the stellar evolution and nucleosynthesis of evolved intermediate-mass stars is still relatively unexplored. We calculate evolutionary sequences of intermediate-mass stars of low metallicity (M=1.7 to 6M?, Z = 0.0006 or [Fe/H] = -1.4) at primordial helium abundance (Y = 0.24) and with helium-enhanced compositions (Y = 0.30, 0.35, 0.40).We find the following: 1) The lifetime of helium-enriched stars is reduced by up to 50% compared to their helium normal counterparts, allowing for low-mass AGB stars to contribute to the chemical evolution of globular clusters; 2) The stellar yields of carbon, and heavy-elements typicallyproduced by low-mass AGB stars (e.g., Ba, La) decrease by ~50% in helium enriched models. 3) The initial mass required for carbon burning (and the transition to super AGB stars with ONe cores) at this metallicity is reduced from Mup > 6M? at Y = 0.24 to Mup = 4.5 ± 0.5M? at Y = 0.40. This will reduce the minimum mass for core collapse supernovae and increase the number of neutron stars. 4) The stellar yields of the helium-rich intermediate-mass stars with proton capture nucleosynthesis at the base of the envelope also decreases, with the most massive 6M? model with Y = 0.40 experiencing almost no third dredge-up. The one exception is the 3M? models, which produce more Ba, La, Ce, and Pb at Y = 0.40 than at Y = 0.24 due to the doubling of the number of thermal pulses.In this talk we present some highlights of our results along with a discussion of the implications for the formation of massive globular clusters.

  10. Phase diagram of second layer of helium adsorbed on graphite

    OpenAIRE

    Pierce, Marlon; Manousakis, Efstratios

    1998-01-01

    Using realistic helium-helium and helium-graphite interactions and the path integral Monte Carlo method, we are able to identify the gas, superfluid liquid, commensurate-solid, and incommensurate-solid phases, and the coexistence regions between them, for the second layer of helium on graphite. The phase boundaries and the specific heat that we determine are in good agreement with experiment. The appearance and disappearance of superfluidity with increasing coverage can be e...

  11. A new helium gas recovery and purification system

    International Nuclear Information System (INIS)

    A helium gas recovery and purification system, based on the principle of gas permeation through a membrane, is described. The system can be used for the purification of helium gas containing air as a contaminant. The apparatus, operating at ambient temperature does not need constant attention, the recovery ratio of helium gas is satisfactory and running costs are low. Gases other than helium can be processed with the apparatus. (U.K.)

  12. Surface excitations in thin helium films on silica aerogel

    OpenAIRE

    Lauter, Hans J.; Bogoyavlenskii, I. V.; Puchkov, Alexander. V. (Alexander.); Godfrin, Henri; Skomorokhov, Andrei; Klier, Jürgen; Leiderer, Paul

    2002-01-01

    First measurements are reported on pure surface excitations in thin superfluid 4He films on silica aerogel. The ripplon dispersion curve is found to be the same for helium on graphite and silica aerogel substrates. However, the layered roton line width in helium films on aerogel shows a pronounced broadening with respect to that found in helium films on graphite.

  13. Superfluid Onset and 2D phase transitions of Helium-4 on Lithium and Sodium

    Science.gov (United States)

    Velasco, Angel; Huisman, Fawn; van Cleve, Eli; Taborek, Peter

    2012-02-01

    We have fabricated lithium and sodium films on quartz crystal microbalances (QCM) using in situ low temperature pulsed laser deposition. The frequency shift and dissipation of the QCM was measured as a function of helium pressure and chemical potential and used to construct the phase diagram of helium films on these substrates. Pressure measurement techniques based on an RGA mass spectrometer, which provides accurate measurement below 10-8 Torr will be described. Lithium and sodium are predicted to be intermediate strength substrates which are strong enough to be wetted by He-4 but weak enough that solid-like layers do not form, so they are candidates for observing sub-monolayer superfluidity in direct contact with a metallic surface. Helium adsorption isotherms and quenches between 0.5K and 1.6K on both lithium and sodium indicated continuous, sub-monolayer helium film growth and superfluid onsets in sub-monolayer films. Features below 1K indicate a collision between a classical 2D liquid/vapor phase transition and the Kosterlitz-Thouless superfluid phase transition. We see no evidence for the pre-wetting step instability predicted for helium on sodium.

  14. Microwave spectroscopic study of the hyperfine structure of antiprotonic helium-3

    CERN Document Server

    Friedreich, Susanne; Caspers, Fritz; Dax, Andreas; Hayano, Ryugo S; Hori, Masaki; Horváth, Dezs?; Juhász, Bertalan; Kobayashi, Takumi; Massiczek, Oswald; Sótér, Anna; Todoroki, Koichi; Widmann, Eberhard; Zmeskal, Johann

    2013-01-01

    In this work we describe the latest results for the measurements of the hyperfine structure of antiprotonic helium-3. Two out of four measurable super-super-hyperfine SSHF transition lines of the (n,L)=(36,34) state of antiprotonic helium-3 were observed. The measured frequencies of the individual transitions are 11.12548(08) GHz and 11.15793(13) GHz, with an increased precision of about 43% and 25% respectively compared to our first measurements with antiprotonic helium-3 [S. Friedreich et al., Phys. Lett. B 700 (2011) 1--6]. They are less than 0.5 MHz higher with respect to the most recent theoretical values, still within their estimated errors. Although the experimental uncertainty for the difference of 0.03245(15) GHz between these frequencies is large as compared to that of theory, its measured value also agrees with theoretical calculations. The rates for collisions between antiprotonic helium and helium atoms have been assessed through comparison with simulations, resulting in an elastic collision rate...

  15. Helium release and microstructural changes in Er(D,T)2-x3Hex films).

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D. S. (Pacific Northwest National Laboratory, Richland, WA); Browning, James Frederick; Snow, Clark Sheldon; Banks, James Clifford; Mangan, Michael A.; Rodriguez, Mark Andrew; Brewer, Luke N.; Kotula, Paul Gabriel

    2007-12-01

    Er(D,T){sub 2-x} {sup 3}He{sub x}, erbium di-tritide, films of thicknesses 500 nm, 400 nm, 300 nm, 200 nm, and 100 nm were grown and analyzed by Transmission Electron Microscopy, X-Ray Diffraction, and Ion Beam Analysis to determine variations in film microstructure as a function of film thickness and age, due to the time-dependent build-up of {sup 3}He in the film from the radioactive decay of tritium. Several interesting features were observed: One, the amount of helium released as a function of film thickness is relatively constant. This suggests that the helium is being released only from the near surface region and that the helium is not diffusing to the surface from the bulk of the film. Two, lenticular helium bubbles are observed as a result of the radioactive decay of tritium into {sup 3}He. These bubbles grow along the [111] crystallographic direction. Three, a helium bubble free zone, or 'denuded zone' is observed near the surface. The size of this region is independent of film thickness. Four, an analysis of secondary diffraction spots in the Transmission Electron Microscopy study indicate that small erbium oxide precipitates, 5-10 nm in size, exist throughout the film. Further, all of the films had large erbium oxide inclusions, in many cases these inclusions span the depth of the film.

  16. Characterization of helium implanted Fe–Cr alloys by means of positron annihilation methods

    International Nuclear Information System (INIS)

    Doppler broadening spectroscopy and positron lifetime measurements have been used for the characterization of radiation damage and helium effects on the microstructure of the ferritic Fe–Cr alloy with 12% (wt.) chromium content. Severe displacement damage (up to 100 dpa) was introduced by the implantation of helium ions with fluence 1.25 × 1018 cm?2. The temperature during the implantation process was below 80 °C. Positron lifetime spectra obtained from slow positron beam experiments confirmed the presence of large voids in the region of the displacement peak. Further investigation by Doppler broadening spectroscopy in the conventional and slow positron beam setups revealed a strong retention of helium in this region, which contributes to the broadening of the momentum peak and at the same time it reduces the positron lifetime in radiation-induced vacancy clusters. The measured Doppler broadened profiles of the implanted materials reasonably correspond with the calculated data showing the helium effect range within 5–12 × 10?3 m0c. Both experimental techniques show empty vacancy clusters to be a dominant type of defect in the first 400 nm region, while helium filling of these defects occurs further in depth. This is in a good agreement with the results of SRIM simulation

  17. Development of an apparatus for cyclic corrosion test in simulated VHTR helium environment

    International Nuclear Information System (INIS)

    A test apparatus was designed and constructed to carry out corrosion tests in simulated VHTR environment, which allowed circulation of helium with closely controlled impurity chemistry under either isothermal or cyclic heating conditions. The principal features of the apparatus are as follows: (1) Test section are made of fused quartz. (2) Four specimens are exposed at a time, each being set in independent cell under equivalent condition. (3) Either thermal-cycled or isothermal tests can be performed. (4) Spalled oxide are recovered in the quartz tube for quantitative gravimetry and the subsequent neutron activation analysis of the constituents of corrosion products. The apparatus is connected to the helium loop with purification, impurity injection and circulation function, which was designed to supply continuously the simulated VHTR helium for material testing. The loop has supplied the helium to corrosion, creep and fatigue test apparatus for over 6 x 104 hours since 1976. The test environment contained controlled quantities of impurities, H2, H2O, CO, CO2 and CH4. Pressure and maximum flow rate of helium are 0.5kg/cm2G and 50 1/min. at outlet of the loop, respectively. Typical tests results are shown to demonstrate that quantitative measurements of the oxidation kinetics for very long test duration are readily available regardless of film spallation, and that the precise analysis of major constituents of the spalled products is also possible. (author)

  18. Rogue Mantle Helium and Neon

    Science.gov (United States)

    Albarede, F.

    2007-12-01

    The canonical view of He isotope geochemistry holds that high 3He/4He ratios in basalts fingerprints undegassed mantle sources. Hawaiian basalts with unradiogenic He with 3He/4He up to 30 RA are therefore seen as originating from parts of the mantle that is still primordial, at least much more so than MORB mantle (3He/4He ~ 8 RA). This view was strongly reinforced by the discovery of solar and even planetary Ne components in oceanic basalts and gas wells. The canonical view, however, conflicts with multiple observations on ocean islands, notably Hawaiian basalts: the correlation of {187}Os/{186}Os with ? 18O combined with the presence of unusually radiogenic Hf isotope compositions for a given Nd isotope composition and the correlation between Hf and Pb isotopes are all features strongly reminiscent of ancient subducted oceanic crust and pelagic sediments in the source of the Hawaiian plume. These conflicting observations beg the question of how Hawaiian basalts, which carry the embodiment of a primordial gas signature, at the same time can provide such strong evidence of surface material recycling. I here suggest and alternative model that uses the marble cake paradigm and Shuster et al.'s data on olivine. A solution to this conundrum lies in an analogy with oil genesis: 3He and Ne do not reside in the low-melting point peridotites in which they were originally hosted but rather migrated since early in Earth history into refractory 'reservoir' rocks. Since there can be no free gas phase percolating at pressures in excess of olivine carbonation at ~3 GPa, He must be largely redistributed by diffusion. The time scale of diffusion is the defining parameter: although over billions of years 3He diffuses across large distances, melting events are too short to efficiently strip residual refractory rocks from their high-3He/4He component. Assuming that melts begin forming over the uppermost 100 km with an upwelling rate of 10 m y-1 in plume conduits and 10 cm y-1 under mid- ocean ridges, the characteristic times of melt extraction in each of these two environments are 10,000 y and 1 My, respectively, and the maximum thickness of refractory layers contributing their He to the magmas are 10 m and 100 m, respectively. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoirs rocks being stretched to a different extent during melting. Old fragments of oceanic lithosphere, and possibly cumulates from the magma ocean, rather than primordial mantle 'nuggets', should host most of the primordial He and Ne presently observed in oceanic basalts. Helium with high 3He/4He ratios may contain a component of primordial origin, but not necessarily reflect the reservoir in which it has been residing for most of the Earth's history.

  19. An experimental study simulating the helium liquefaction process in a reciprocating magnetic refrigerator

    International Nuclear Information System (INIS)

    We have constructed a special one-shot test apparatus to investigate the properties of a reciprocating magnetic refrigerator for helium liquefaction. The liquefaction efficiency for one-shot demagnetization was only about 40% with an initial temperature of 5 K, and higher initial temperatures gave lower liquefaction efficiencies. Losses in the experiment can be classified into four causes: the thermal resistance of the film condensation heat transfer, friction, the heat flow from the holders to the refrigerant and cooling of gaseous helium above 4.2 K to 4.2 K. The last cause was the most dominant

  20. Fine structure of the 2 3P state in helium-like sulfur and chlorine

    International Nuclear Information System (INIS)

    We present precision measurements of the 1s2p (3P2 - 3P0) fine structure energies in the helium-like ions S14+ and Cl15+. The fine structures are obtained from spectroscopic measurements of the 1s2s 3S1 - 1s2p 3P0,2 transition wavelengths. These results represent the most precise experimental determinations of the helium-like J=2 - 0 intervals for Z>5. They establish the magnitude of missing higher order relativistic contributions in previous high-Z calculations of this fine structure, and they are in excellent agreement with new relativistic many-body calculations

  1. The evolution of naked helium stars with a neutron-star companion in close binary systems

    OpenAIRE

    Dewi, J.D.M.; Pols, O.R.; Savonije, G.J.; Heuvel, E. P. J. van den

    2002-01-01

    The evolution of helium stars with masses of 1.5 - 6.7 M_sun in binary systems with a 1.4 M_sun neutron-star companion is presented. Such systems are assumed to be the remnants of Be/X-ray binaries with B-star masses in the range of 8 - 20 M_sun which underwent a case B or case C mass transfer and survived the common-envelope and spiral-in process. The orbital period is chosen such that the helium star fills its Roche lobe before the ignition of carbon in the centre. We dist...

  2. Particle Detection in Superfluid Helium: R&D for Low Energy Solar Neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    Lanou, Robert E., Jr.

    2006-03-31

    This report presents a summary of the results from R&D conducted as a feasibility study in the Department of Physics of Brown University for detection of low energy solar neutrinos utilizing a superfluid helium target. The report outlines the results in several areas: 1) development of experimental facilities, 2) energy deposition by electrons and alphas in superfluid helium, 3) development of wafer and metallic magnetic calorimeters, 4) background studies, 5) coded apertures and conceptual design, 6) Detection of single electrons and 7) a simulation of expected performance of a full scale device. Recommendations for possible future work are also presented. A bibliography of published papers and unpublished doctoral theses is included.

  3. Experimental observations of flow boiling of liquid helium I in vertical channels

    International Nuclear Information System (INIS)

    Results are reported of the flow structure and pressure drop of helium 1 flowing upwards in a vertical heated circular glass tube. The experiments covered heat fluxes from 4.5 to 600 Wm-2, mass fluxes from 2 to 12 kg m-2s-1 and pressures between 1 and 1.2 atm. For the bubble flow regime the shape, size and drag coefficient of the observed bubbles are reported. Slip velocity, void fraction and pressure drop measurements are compared with generally accepted two-phase flow theories. A void fraction correlation for two-phase helium flow is proposed. (author)

  4. Application of JLab 12GeV helium refrigeration system for the FRIB accelerator at MSU

    International Nuclear Information System (INIS)

    The planned approach to have a turnkey helium refrigeration system for the MSU-FRIB accelerator system, encompassing the design, fabrication, installation and commissioning of the 4.5-K refrigerator cold box(es), cold compression system, warm compression system, gas management, oil removal and utility/ancillary systems, was found to be cost prohibitive. Following JLab’s suggestion, MSU-FRIB accelerator management made a formal request to evaluate the applicability of the recently designed 12GeV JLab cryogenic system for this application. The following paper will outline the findings and the planned approach for the FRIB helium refrigeration system

  5. Adsorption purification of helium coolant of high-temperature gas-cooled reactors of carbon dioxide

    International Nuclear Information System (INIS)

    A series experiments on adsorption purification of helium of CO2 using national adsorbent under the conditions characteristic of HTGR type reactors cleanup system is performed. The experimnts have been conducted under the dynamic mode with immobile adsorbent layer (CaA zeolite) at gas flow rates from 0,02 to 0,055 m/s in the pressure range from 0,8 to 5 MPa at the temperature of 273 and 293 K. It is shown that the adsorption grows with the decrease of gas rate, i.e. with increase of contact time with adsorbent. The helium pressure, growth noticeably whereas the temperature decrease from 293 to 273 K results in adsorption 2,6 times increase. The conclusion is drawn that it is advisable drying and purification of helium of CO2 to perform separately using different zeolites: NaA - for water. CaA - for CO2. Estimations of purification unit parameters are realized

  6. Depth-dependence recovery of helium-implanted 18 carats gold-silver alloy

    International Nuclear Information System (INIS)

    Helium diffusion in Au60Ag40 is investigated using a variable energy positron beam. The positron diffusion length of the annealed material (66 ± 1 nm) is reduced after implantation of 2.2 x 1014 He ions/cm2 at 300 keV. During isochronal annealing up to 600 K, the recovery rate of the Doppler broadening lineshape parameter S strongly depends on the distance to the helium implantation peak, indicating an increase of the defect stabilization by He atoms. In contrast, for subsequent annealing, and irrespective of the depth, a maximum in S occurs at 670 K (around 0.5 Tm) resulting from competing processes of growth and breaking up of helium bubbles. (orig.)

  7. Collision-induced polarized and depolarized Raman spectra of helium and the diatom polarizability

    International Nuclear Information System (INIS)

    The spectral distributions and absolute intensities of collision-induced Raman spectra of helium are obtained at 30 amagat, with incident beam polarizations parallel and perpendicular to the observation. These spectra can readily be separated into the polarized and the depolarized Raman continuum of the helium diatom. For comparison, spectra are also computed from wave mechanics, on the basis of Placzeck's polarizability theory. Accurate, semiempirical interaction potentials are used as input, together with ab initio computations of the helium diatom polarizability tensor components. The computed spectra of selected trace and anisotropy functions agree with the observed polarized and depolarized continua. Anisotropy functions consistent with the depolarized spectrum differ by less than 5% from the classical dipole-induced dipole (DID) values at 2.685 A separation

  8. Scintillation and charge extraction from the tracks of energetic electrons in superfluid helium-4

    CERN Document Server

    Guo, W; Cahn, S B; Nikkel, J A; Shin, Y; McKinsey, D N

    2011-01-01

    An energetic electron passing through liquid helium causes ionization along its track. The ionized electrons quickly recombine with the resulting positive ions, which leads to the production of prompt scintillation light. By applying appropriate electric fields, some of the ionized electrons can be separated from their parent ions. The fraction of the ionized electrons extracted in a given applied field depends on the separation distance between the electrons and the ions. We report the determination of the mean electron-ion separation distance for charge pairs produced along the tracks of beta particles in superfluid helium at 1.5 K by studying the quenching of the scintillation light under applied electric fields. Knowledge of this mean separation parameter will aid in the design of particle detectors that use superfluid helium as a target material.

  9. Reconciling the Galactic Bulge Turnoff Age Discrepancy with Enhanced Helium Enrichment

    CERN Document Server

    Nataf, David M

    2011-01-01

    We show that the factor $\\sim$2 discrepancy between spectroscopic and photometric age determinations of the Galactic bulge main-sequence turnoff can be naturally explained by positing an elevated helium enrichment for the bulge relative to that assumed by standard isochrones. We obtain an upper bound on the helium enrichment parameter of the bulge $({\\Delta}Y/{\\Delta}Z)_{\\rm{Bulge}} \\lesssim 5.0$ given the requirement that the spectroscopic and photometric ages be consistent and the limiting condition of instantaneous star formation. The corresponding mean age for the bulge is $t_{\\rm{Bulge}} \\approx 10$ Gyr. We discuss phenomenological evidence that the bulge may have had a chemical evolution that is distinct from the solar neighborhood in this manner, and we make several testable predictions. Should this emerging picture of the bulge as helium-enhanced hold, it will require the development of new isochrones, new model atmospheres, and modified analysis and cosmological interpretation of the integrated light...

  10. Experimental study on Paschen discharge in helium for high voltage cryogenic insulation material

    International Nuclear Information System (INIS)

    According to the requirements of ITER, all the solid superconducting insulation of current leads, magnets, cooling and measurement pipeline at high potential should withstand 80 K-300 K thermal cycles. If helium leak or pipe leak taken place, and insulation has been formed some flaws, Paschen discharge would be occur. The experimental program aimed at analyzing the low-temperature electro-physical performance of solid superconducting insulation, which was designed with different configuration such as thickness, material structure and so on. The dielectric performance of both pre-preg cryogenic insulation and the wet wrap cryogenic insulation were studied. Both of the dielectric strength of the two type insulation is in the range from 11 kV / mm to 23 kV / mm at 80 K helium condition. Besides, both of the two type insulation samples of 3 mm and 5 mm thickness can withstand 30 kV under various helium pressures at 80 K. (author)

  11. Commuting operators for the helium atom

    Science.gov (United States)

    Gottdiener, Luis

    2015-11-01

    We show that for the helium atom with electrostatic repulsion between electrons, the operators for the z component and the square of the total angular momentum commute with the Hamiltonian, and therefore quantum numbers M and L can be used to label the energy eigenstates. This fact is used but not proved in most quantum mechanics textbooks.

  12. Fuzzy pressure controller for helium bath cryostats.

    Czech Academy of Sciences Publication Activity Database

    Hanzelka, Pavel; Jura, P.

    Praha : ICARIS, 2002, s. 53 - 56. ISSN 0151-1637. [CRYOGENICS 2002. Praha (CZ), 23.04.2002-26.04.2002] R&D Projects: GA ?R GA101/00/0028; GA ?R GA102/01/1485 Institutional research plan: CEZ:AV0Z2065902 Keywords : fuzzy controller * helium cryopump * pressure controller Subject RIV: BJ - Thermodynamics

  13. Helium Flow Induced Orbit Jitter at RHIC

    CERN Document Server

    Montag, Christoph; Jia, Lin; Nicoletti, Tony; Satogata, Todd; Schmalzle, Jesse D; Tallerico, Thomas

    2005-01-01

    Horizontal beam orbit jitter at frequencies around 10 Hz has been observed at RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta qudrupole triplets around the ring, where they coincide with mechanical modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations.

  14. Messer to provide helium for LHC project

    CERN Multimedia

    2008-01-01

    Over the course of the next few years, industrial gas specialist The Messer Group, through its Swiss subsidiary Messer Schweiz AG, is to provide a 160,000kg supply of helium to the European Organisation for Nuclear Research (CERN) for the operation of the world's largest particle accelerator.

  15. Messer to provide helium for LHC

    CERN Multimedia

    2008-01-01

    Over the course of the next few years, industrial gas specialist The Messer Group, through its Swiss subsidiary Messer Schweiz AG, is to provide a 160,000kg supply of helium to the European Organisation for Nuclear Research (CERN) for the operation of the world's largest particle accelerator.

  16. HELIUM FLOW INDUCED ORBIT JITTER AT RHIC.

    Energy Technology Data Exchange (ETDEWEB)

    MONTAG, C.; HE, P.; JIA, L.; NICOLETTI, A.; SATOGATA, T.; ET AL.

    2005-05-16

    Horizontal beam orbit jitter at frequencies around 10 Hz has been observed in RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta quadrupole triplets around the ring, where they coincide with mechanical modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations.

  17. Electron scattering in a helium Debye plasma

    International Nuclear Information System (INIS)

    Graphical abstract: We present our results of the total ionization cross sections for the helium ground state. We see agreement between experiment and the no screening calculations for all projectile energies considered. To date there is no other ab initio theory that is able to achieve such agreement over the entire energy range. The D = 100 results are barely distinguishable from the no screening ones. The D = 10 results are visibly different at the lower energies, but still converge to the other two calculations at the higher energies. Highlights: ? Cross sections for electron scattering off helium in a Debye plasma are presented for excitation and ionization from the ground state. ? The Debye–Huckel potential substantially effects all levels of the helium atom except the ground state. ? Generally, a rather weak dependence of the presented cross sections was found for D = 10. - Abstract: The immense progress in the field of electron–atom scattering, where pure Coulomb potentials are involved, has been translated to collision processes in Debye plasmas. The Debye–Hückel potential is used to describe plasma Coulomb screening effects depending on the temperature and density of the plasma. We provide benchmark results of electron–helium scattering for momentum transfer cross sections, discrete excitation and ionization over a broad range of incident energies and Debye radii.

  18. Are there eta-Helium bound states?

    OpenAIRE

    Wycech, S; Green, A M; Niskanen, J. A.

    1995-01-01

    Using multiple scattering theory the scattering lengths of $\\eta$ mesons on helium nuclei are calculated and checked against final state $\\eta$ interactions from the $pd \\rightarrow \\eta ^3$He and $dd \\rightarrow \\eta ^4$He reactions. The existence of an $\\eta^4$He quasibound state is indicated.

  19. Helium and Sulfur Hexafluoride in Musical Instruments

    Science.gov (United States)

    Forinash, Kyle; Dixon, Cory L.

    2014-01-01

    The effects of inhaled helium on the human voice were investigated in a recent article in "The Physics Teacher." As mentioned in that article, demonstrations of the effect are a popular classroom activity. If the number of YouTube videos is any indication, the effects of sulfur hexafluoride on the human voice are equally popular.…

  20. Potential applications of high temperature helium

    International Nuclear Information System (INIS)

    This paper discusses the DOE MHTGR-SC program's recent activity to improve the economics of the MHTGR without sacrificing safety performance and two potential applications of high temperature helium, the MHTGR gas turbine plant and a process heat application for methanol production from coal

  1. An asteroseismic signature of helium ionization

    CERN Document Server

    Houdek, G

    2006-01-01

    We investigate the influence of the ionization of helium on the low-degree acoustic oscillation frequencies in model solar-type stars. The signature in the oscillation frequencies characterizing the ionization-induced depression of the first adiabatic exponent $\\gamma$ is a superposition of two decaying periodic functions of frequency $\

  2. Femtosecond spectroscopy on alkali-doped helium nanodroplets; Femtosekundenspektroskopie an alkalidotierten Helium-Nanotroepfchen

    Energy Technology Data Exchange (ETDEWEB)

    Claas, P.

    2006-01-15

    In the present thesis first studies on the short-time dynamics in alkali dimers and microclusters, which were bound on the surface of superfluid helium droplets, were presented. The experiments comprehended pump-probe measurements on the fs scale on the vibration dynamics on the dimers and on the fragmentation dynamics on the clusters. Generally by the studies it was shown that such extremely short slopes can also be observed on helium droplets by means of the femtosecond spectroscopy.

  3. Development of a helium cryostat for laser spectroscopy of atoms with unstable nuclei in superfluid helium

    International Nuclear Information System (INIS)

    We are developing a new nuclear laser spectroscopic technique for the study of nuclear structure that can be applied to short-lived low-yield atoms with unstable nuclei. The method utilizes superfluid helium (He II) as a trapping medium for high-energy ion beams. A liquid helium cryostat with optical windows is a key apparatus for this type of experiment. We describe the design and the performance of the cryostat which is developed for the present project

  4. Electronic structure of helium atom in a quantum dot

    CERN Document Server

    Saha, Jayanta K; Mukherjee, T K

    2015-01-01

    Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) [n = 1-6] states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns [n = 2-5] and 2pnp [n = 2-5] configuration of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential representing the quantum dot. It has been explicitly demonstrated that electronic structure properties become a sensitive function of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the wi...

  5. The liquid helium thermosyphon for the GEM Detector Magnet

    International Nuclear Information System (INIS)

    The GEM detector magnet, a horizontal solenoid 19.5 m in diameter and wound with a niobium-titanium cable in conduit, will be located with it's axis 19.5 m below grade. The conductor is wound on the inside of an aluminum bobbin which is cooled by liquid helium which flows by natural convection in a thermosyphon loop from a large storage dewar located at the ground surface. The function of the thermosyphon system is to absorb the environmental heat load as well as any internally generated heat. In the first category is included that heat which is transferred to the magnet by way of the mechanical supports, the insulation and the current leads. The internally generated heat includes the resistive heating within the normally conducting conductor splices and the inductive heating of the bobbin during current transients. Though similar systems have been employed elsewhere, there are some unique aspects to the present design. By taking advantage of the large vertical head available, the parallel heat exchanger passes within the magnet remain sub-cooled, thus insuring single phase coolant within the magnet. It is believed that this will be the first instance of such a large vertical head being used to this advantage in a helium system

  6. Spectrophotometry of extreme helium stars - Ultraviolet fluxes and effective temperatures

    Science.gov (United States)

    Heber, U.; Drilling, J. S.; Schoenberner, D.; Lynas-Gray, A. E.

    1984-01-01

    Ultraviolet flux distributions are presented for the extremely helium rich stars BD +10 deg 2179, HD 124448, LSS 3378, BD -9 deg 4395, LSE 78, HD 160641, LSIV -1 deg 2, BD 1 deg 3438, HD 168476, MV Sgr, LS IV-14 deg 109 (CD -35 deg 11760), LSII +33 deg 5 and BD +1 deg 4381 (LSIV +2 deg 13) obtained with the International Ultraviolet Explorer (IUE). Broadband photometry and a newly computed grid of line blanketed model atmospheres were used to determine accurate angular diameters and total stellar fluxes. The resultant effective temperatures are in most cases in satisfactory agreement with those based on broadband photometry and/or high resolution spectroscopy in the visible. For two objects, LSII +33 deg 5 and LSE 78, disagreement was found between the IUE observations and broadband photometry: the colors predict temperatures around 20,000 K, whereas the UV spectra indicate much lower photospheric temperatures of 14,000 to 15,000 K. The new temperature scale for extreme helium stars extends to lower effective temperatures than that of Heber and Schoenberner (1981) and covers the range from 8,500 K to 32,000 K. Previously announced in STAR as N83-24433

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

    International Nuclear Information System (INIS)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Helium measurements of pore-fluids obtained from SAFOD drillcore

    Energy Technology Data Exchange (ETDEWEB)

    Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B.M.

    2010-04-15

    {sup 4}He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk {sup 4}He diffusion coefficient of 3.5 {+-} 1.3 x 10{sup -8} cm{sup 2}s{sup -1} at 21 C, compared to previously published diffusion coefficients of 1.2 x 10{sup -18} cm{sup 2}s{sup -1} (21 C) to 3.0 x 10{sup -15} cm{sup 2}s{sup -1} (150 C) in the sands and clays. Correcting the diffusion coefficient of {sup 4}He{sub water} for matrix porosity ({approx}3%) and tortuosity ({approx}6-13) produces effective diffusion coefficients of 1 x 10{sup -8} cm{sup 2}s{sup -1} (21 C) and 1 x 10{sup -7} (120 C), effectively isolating pore fluid {sup 4}He from the {sup 4}He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 {+-} 0.4% (SD, n=4) and mudstones 3.1 {+-} 0.8% (SD, n=4).

  10. Doubly excited helium. From strong correlation to chaos

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yuhai

    2006-03-15

    In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I{sub 15}, and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I{sub 5} to I{sub 9} and I{sub 7}, respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I{sub 4} were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I{sub 4} by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

  11. Doubly excited helium. From strong correlation to chaos

    International Nuclear Information System (INIS)

    In the present dissertation, the double excitation states of helium including the autoionization decay of these states were studied experimentally and theoretically in a broad energy region, which includes the transition from strong correlation below the low single ionization thresholds (SIT) to the region of quantum chaos at energies very close to the double-ionization threshold. Two kind of experiments were performed, namely total-ion-yield measurements with the aim to observe total cross sections (TCS) and electron time-of-flight (TOF) measurements to obtain partial cross sections (PCS) as well as angular distribution parameters (ADP). Both types of measurements were performed at the third generation synchrotron radiation facility BESSY II in Berlin. The TCSs were recorded up to the SIT I15, and they were found to be in in excellent agreement with state-of-the-art complex-rotation calculations performed recently by D. Delande. These experimental and theoretical data on the TCSs were analyzed in order to study quantum chaos in doubly excited helium, and interesting signatures of quantum chaos were found. The TOF technique allowed to measure PCSs and ADPs in the energy regions from I5 to I9 and I7, respectively. These experimental data provide a critical assessment of theoretical models that can be used to explore the dynamics of strong correlation as well as quantum chaos in helium. In the theoretical part of this dissertation, the n- and l-specific PCSs and ADPs below I4 were calculated employing the R-matrix method. The present theoretical results agree well with a recent experimental study of l-specific PCSs below I4 by J.R. Harries et al. An analysis of patterns in the PCSs and ADPs on the basis of the present experimental and theoretical l-specific data allowed to improve the present understanding of autoionization decay dynamics in this two-electron atom. (orig.)

  12. Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets

    International Nuclear Information System (INIS)

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (?? > 100 cm?1) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time

  13. Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets.

    Science.gov (United States)

    Pentlehner, D; Slenczka, A

    2015-01-01

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (?? > 100 cm(-1)) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time. PMID:25573565

  14. Study on the Dynamic Performance of the Helium Turboexpander for EAST Subsystems

    Science.gov (United States)

    Chen, Shuangtao; Yang, Shanju; Fu, Bao; Zhang, Qiyong; Hou, Yu

    2015-06-01

    An increase of the cooling capacities in the liquid helium temperature area is required by Experimental Advanced Superconducting Tokamak (EAST) due to the extension of its subsystems in the near future. Limited by the heat exchangers, cryogenic pipes, and cryogenic valves, it is difficult to enlarge the present EAST helium system. 102 W@4.5 K level helium cryogenic systems are needed in view of feasibility and economy. A turboexpander is the key component of a helium cryogenic system. In this article, a hydrostatic gas lubricated cryogenic helium turboexpander for a 900 W@4.5 K cryogenic helium system was developed for the EAST updated subsystem by the Institute of Plasma Physics, Chinese Academy of Sciences and the Institute of Cryogenic and Refrigeration of Xi'an Jiaotong University. The main components, such as gas bearings, expansion wheel, shaft, and brake wheel, were briefly presented. The dynamic performance of the journal and thrust gas bearings was investigated numerically. The rotordynamic performance of the developed turboexpander was studied experimentally. The results show that the axial and radial load capacities supplied by the journal gas bearing and thrust gas bearing are enough to balance the axial force and radial force of the rotor. A 43% overspeed operation was achieved, which validated the reasonable design of the turboexpander. supported by Joint Funds of the National Natural Science Foundation of China (No. 11176023), National Natural Science Foundation of China (No. 51306135), and partially supported by the China Postdoctoral Science Foundation (No. 2013M532040) and Special Financial Grant of China Postdoctoral Science Foundation (No. 2014T70917)

  15. The future of helium as a natural resource

    CERN Document Server

    Glowacki, Bartek A; Nuttall, William J

    2012-01-01

    The book reveals the changing dynamics of the helium industry on both the supply-side and the demand-side. The helium industry has a long-term future and this important gas will have a role to play for many decades to come. Major new users of helium are expected to enter the market, especially in nuclear energy (both fission and fusion). Prices and volumes supplied and expected to rise and this will prompt greater efforts towards the development of new helium sources and helium conservation and recycling.

  16. Experiments on helium refrigerant at high speed of rotation

    International Nuclear Information System (INIS)

    Electrical machines with superconducting field windings can require helium refrigeration in a rotating system. Heat transfer measurements have been made on helium in a rotating open thermosyphon. Various heater surfaces have been used at the end of a 25 mm tube full of helium at a radial distance of 0.22 mm from the rotation axis for speeds up to 37 Hsub(z), for both boiling heat transfer in subcritical helium, and convective heat transfer in sub and supercritical helium. A larger rotor of 0.44 m radius, to rotate up to 60 Hz, has been constructed to extend the range of the experiments. (author)

  17. Calculation and measurement of helium generation and solid transmutations in Cu-Zn-Ni alloys

    International Nuclear Information System (INIS)

    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. 63Cu transmutes to 64Ni and 64Zn, in about a 2-to-1 ratio, and 65Cu transmutes to 66Zn. The 64Zn further transmutes to 65Zn which has been shown to have a high thermal neutron (n,?) 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 58Ni (n,?) 59Ni (n,?) 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,?) cross section for 65Zn 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 Garner and Greenwood

  18. Calculation and measurement of helium generation and solid transmutations in Cu-Zn-Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Greenwood, L.R.; Oliver, B.M.; Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States); Muroga, T. [National Inst. of Fusion Science, Nagoya (Japan)

    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 Garner and Greenwood.

  19. Practical-scale tests of cryogenic molecular sieve for separating low-concentration hydrogen isotopes from helium

    International Nuclear Information System (INIS)

    There are a number of cases in fusion fuel processing where low-concentration hydrogen isotopes need to be separated from helium. Usually the helium is a purge gas used to move hydrogen isotopes from one location to another. One of the most notable applications is associated with removing tritium from a solid ceramic breeder. For some designs which have been considered, helium with about 1 % protium is purged through the ceramic. The protium exchanges with tritium which has been bred in the solid. The resulting gas composed of helium (?99%), protium (?1%) and tritium (?0.01%) flows out of the blanket and, for further processing, requires separation of the hydrogen isotopes and the helium. Earlier bench-scale (about 50 cc of sieve) work at the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory examined a number of adsorbents for their suitability for separating low-concentration hydrogen (no tritium) from helium. One of the effective adsorbents was Linde 5A molecular sieve. The purpose of this paper is to report practical-scale experiments including tritium. These tests used existing cryogenic molecular sieve beds (MSB'S) which each contain about 1.6 kg of Linde 5A molecular sieve

  20. Experimental study of DEMO helium cooled divertor target mock-ups to estimate their thermal and pumping efficiencies

    International Nuclear Information System (INIS)

    The helium cooled divertor for the DEMO fusion reactor is designed for removal of surface high-heat-flux up to 15 MW/m2 during normal operation. To reduce thermal stresses in divertor plates finger-like array structure was chosen, where each tungsten finger is cooled by helium at inlet parameters of 10 MPa, 634 oC. The gas puffing facility (GPF) was developed for measurement of mock-ups performance at the reversed high heat flux, when the plasma-facing surface of finger-like mock-up was intensively cooled by water. The goals of these experiments are: (1) to compare heat removal performance for different design mock-ups and (2) to adjust computational fluids dynamics (CFD) codes for accurate simulations. Long helium pulses (?100 s duration) and sufficient capability (1-2 kg of He per pulse) facilitate attainment of the steady-state regime in experiments, when 5-15 g/s mass flow rate of helium was scanned. Results of last experimental campaign carried on in December 2004 revealed that all helium distributing cartridge options demonstrate optimistic performance (as compared to CFD simulations) and capability to transfer 10-25 MW/m2 in the helium mass flow rate (MFR) range of 5-15 g/s

  1. Life time test of a partial model of HTGR helium-helium heat exchanger

    International Nuclear Information System (INIS)

    Authors had proposed a design guide for the HTGR components and applied it to the design and construction of the 1.5 Mwt helium heat exchanger test loop for the nuclear steel making under the financial support of the Japanese Ministry of International Trade and Industry. In order to assure that the design method covers all the conceivable failure mode and has enough safety margin, a series of life time tests of partial model may be needed. For this project, three types of model tests were performed. A life time test of a partial model of the center manifold pipe and eight heat exchanger tubes were described in this report. A damage criterion with a set of material constants and a simplified method for stress-strain analysis for stub tube under three dimensional load were newly developed and used to predict the lives of each tube. The predicted lives were compared with the experimental lives and good agreement was found between the two. The life time test model was evaluated according to the proposed design guide and it was found that the guide has a safety factor of approximately 200 in life for this particular model. (author)

  2. Ab initio potential energy curve for the helium atom pair and thermophysical properties of the dilute helium gas. II. Thermophysical standard values for low-density helium

    OpenAIRE

    Vogel, Eckhard; Bich, Eckard; Hellmann, Robert

    2007-01-01

    Abstract A helium-helium interatomic potential energy curve determined from quantum-mechanical ab initio calculations and described with an analytical representation considering relativistic retardation effects (R. Hellmann, E. Bich, and E. Vogel, Mol. Phys. (submitted)) was used in the framework of the quantum-statistical mechanics and of the corresponding kinetic theory to calculate the most important thermophysical properties of helium governed by two-body and three-body interac...

  3. The installation of helium auxiliary systems in HTGR

    International Nuclear Information System (INIS)

    The inert gas Helium was chosen as reactor coolant in high temperature gas coolant reactor, therefore a set of Special and uncomplex helium auxiliary systems will be installed, the safe operation of HTR-10 can be safeguarded. It does not effect the inherent safety of HTR-10 MW if any one of all those systems were damaged during operation condition. This article introduces the design function and the system principle of all helium auxiliary systems to be installed in HTR-10. Those systems include: helium purification and its regeneration system, helium supply and storage system, pressure control and release system of primary system, dump system for helium auxiliary system and fuel handling, gaseous waste storage system, water extraction system for helium auxiliary systems and evacuation system for primary system

  4. Atomic origins of solid helium bubbles in tungsten

    International Nuclear Information System (INIS)

    Solid helium bubbles were directly observed in the helium ion implanted tungsten (W), by different transmission electron microscopy (TEM) techniques at room temperature. The diameters of these solid helium bubbles range from 1 nm to 8 nm in diameter with the mean bubble size about 3 nm. The selected area electron diffraction (SAED) and fast Fourier transform (FFT) images revealed that solid helium bubbles possess body-centered cubic (bcc) structure with a lattice constant of 0.447 nm. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images further confirmed the existence of helium bubble in tungsten. The present findings provide an atomic level view of the microstructure evolution of helium in the materials, and revealed the existence of solid helium bubbles in materials. (rapid communication)

  5. Matter-wave diffraction of quantum magical helium clusters

    International Nuclear Information System (INIS)

    The properties of large helium clusters are of great interest for nuclear many-body theoreticians because of the many close analogies between nuclei and helium clusters. Small clusters of helium atoms show a number of strange magic-like quantum properties. Helium clusters are the only clusters which are definitely liquid. This property led to the development of a newly experimental technique of inserting foreign molecules into large helium clusters, which serve as ultra-cold nano-containers. The diffraction technique of helium clusters provided the first unequivocal experimental evidence for the existence not only of the helium dimer, but also of the trimer, tetramer and larger clusters. The diffraction technique has been used to discover and identify a number of other unusual clusters like small Hem4Hen3 clusters. Experiments have shown that the observed magic numbers are not at all related to cluster stability but have a new kinetic origin. (A.C.)

  6. Flow characteristics and redesign of highly loaded helium compressors

    International Nuclear Information System (INIS)

    Starting with the peculiarity of helium, the differences in choosing the design parameters between helium compressors and air compressors are analyzed, and the characteristics in parameter selection to increase helium compressors loading are emphasized. Because the physical characteristics of helium are quite different from that of air, the flow in helium compressors is presented as low Mach number resulting in low stage pressure ratio, so generally the variation of passage size is less in helium compressors. In order to improve the stage loading and decrease the stage number, it is necessary for each stage to increase reactor. A numerical study is performed for a multistage Helium compressor to analyze the flow characteristics and the redesign is carried out in this paper. (authors)

  7. Molecular dynamics simulation of helium bubble coalescence in titanium

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed to study the helium bubble coalescence in titanium. The influence of helium bubble coalescence on the metal microstructure was analyzed. The bubble coalescences in the bulk metal and near the metal surface were compared. When helium bubbles lie in the bulk metal, a lot of defects are induced around by the bubbles coalescence and extend outward. The coalescence of helium bubbles with 1.77 nm diameter can form a dislocation loop around them. The helium bubbles after coalescence evolve from dumbbell shape toward ellipsoid shape. When helium bubbles lie near the metal surface, the defects induced by bubbles coalescence are likely to move to the top surface, and the metal around bubble tends to restore the crystal structure. The helium bubbles evolve from dumbbell shape toward hemispherical shape. (authors)

  8. Helium nano-bubble evolution in aging metal tritides.

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2004-05-01

    A continuum-scale, evolutionary model of helium (He) nano-bubble nucleation, growth and He release for aging bulk metal tritides is presented which accounts for major features of the experimental database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, is found to occur during the first few days following tritium introduction into the metal and is sensitive to the He diffusivity and pairing energy. An effective helium diffusivity of 0.3 x 10{sup -16} cm{sup 2}/s at 300 K is required to generate the average bubble density of 5x 1017 bubbles/cm3 observed by transmission electron microscopy (TEM). Early bubble growth by dislocation loop punching with a l/radius bubble pressure dependence produces good agreement with He atomic volumes and bubble pressures determined from swelling data, nuclear magnetic resonance (NMR) measurements, and hydride pressure-composition-temperature (PCT) shifts. The model predicts that later in life neighboring bubble interactions may first lower the loop punching pressure through cooperative stress effects, then raise the pressure by partial blocking of loops. It also accounts for the shape of the bubble spacing distribution obtained from NMR data. This distribution is found to remain fixed with age, justifying the separation of nucleation and growth phases, providing a sensitive test of the growth formulation, and indicating that further significant bubble nucleation does not occur throughout life. Helium generated within the escape depth of surfaces and surface-connected porosity produces the low-level early helium release. Accelerated or rapid release is modeled as inter-bubble fracture using an average ligament stress criterion. Good agreement is found between the predicted onset of fracture and the observed He-metal ratio (HeM) for rapid He release from bulk palladium tritide. An examination of how inter-bubble fracture varies over the bubble spacing distribution shows that the critical Hem will be lower for thin films or small particle material. It is concluded that control of He retention can be accomplished through control of bubble nucleation.

  9. Estimation of helium intergranular adsorption in OKh16N15M3B and OKh16N15M3BR steels

    International Nuclear Information System (INIS)

    Possibility of application of the internal friction method for evaluating intergranular adsorption of helium forming in steels in the process of reactor irradiation is shown. Neutron fluence corresponding to adsorption semisaturation of steel grain boundary with helium was determined from change of the height of internal friction grain-boundary maximum. It is shown that helium adsorption saturation of OKh16N15M3B steel grain boundaries occurs at helium concentration of ? 8.8x10-5 % in grain body at 780 deg C. Helium bond energy with grain-boundary traps constitutes 1.26 and 0.87 eV for OKh16N15M3B and OKh16N15M3BP steels, accordingly

  10. Measurement of Helium-3/Helium-4 Ratios in Soil Gas at the 618-11 Burial Ground; FINAL

    International Nuclear Information System (INIS)

    Seventy soil gas-sampling points were installed around the perimeter of the 618-11 Burial Ground, approximately 400 feet downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 3,100 feet. Soil gas samples were collected and analyzed for helium-3/helium-4 ratios from these 70 points. Helium-3/helium-4 ratios determined from the soil gas sampling points showed significant enrichments, relative to ambient air helium-3 concentrations. The highest concentrations were located along the northern perimeter of the burial ground. Helium-3/helium-4 ratios (normalized to the abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transect downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground

  11. Helium diffusion during formation of the first galaxies

    CERN Document Server

    Medvedev, P; Gilfanov, M

    2015-01-01

    We investigate the possible impact of diffusion on the abundance of helium and other primordial elements during formation of the first structures in the early Universe. We consider the primary collapse of a perturbation and subsequent accretion of matter onto the virialized halo, restricting our consideration to halos with masses considerably above the Jeans limit. We find that diffusion in the cold and nearly neutral primordial gas at the end of the Dark Ages could raise the abundance of primordial elements relative to hydrogen in the first virialized halos: helium enrichment could reach $\\delta Y_p/Y_p \\sim 10^{-4}$ in the first star-forming minihalos of $ \\sim 10^5-10^6 M_{\\odot}$. A moderate (to ~ 100 K) preheating of the primordial gas at the beginning of cosmic reionization could increase this effect to $\\delta Y_p/Y_p \\sim 3\\times 10^{-4}$ for $\\sim 10^6 M_{\\odot}$ halos. Even stronger abundance enhancements, $\\delta Y_p/Y_p$ ~ a few $10^{-3}$, may arise at much later, post-reionization epochs, z ~ 2, ...

  12. Optical breakdown of helium in Bessel laser radiation beams

    International Nuclear Information System (INIS)

    Numerical simulation is used to investigate the dynamics of formation of a helium plasma in Bessel beams, shaped by an axicon and a phase converter from a laser radiation pulse with Gaussian temporal and radial intensity profiles. The beam intensities at the breakdown threshold are determined as a function of the pulse duration for various radial field distributions in a beam characterised by Bessel functions of order m (m = 0 - 5). It is shown that in the investigated range of parameters the threshold intensity is independent of m. The temporal and spatial evolution of the resultant plasma, and the dependence of the plasma characteristics on the pulse parameters are considered. Conditions are found for the formation of tubular plasma channels in beams of orders m?1. The adopted model of the optical breakdown of helium is shown to be satisfactory because of a good agreement between the results of calculations of the moment of breakdown in a zeroth-order Bessel beam and experimental results. (interaction of laser radiation with matter. laser plasma)

  13. Helium blistering on the surface of ion-alloyed steel

    International Nuclear Information System (INIS)

    The helium blistering of the 0Kh16N15M3B austenitic stainless steel alloyed with carbon, boron, manganese, chromium and nickel was investigated experimentally. The impurities were introduced into the steel by the ion implantation method. Ions of C+, B+, N+, Cr+, Mn+, Ni+ with energies of 40 keV were implanted into the specimens under investigation at 600 deg C. In the case of Ni+ ions, the radiation dose was varied between 1017 and 5x1O18 cm-2, and the dose for the remaining ions was 1018 cm-2. After implantation, all the targets were simultaneously irradiated with He2 ions with energies of 8a keV at room temperature. The dose of irradiation by He+ ions was 1018 cm-2. Presented is the initial surface microstructure of the steel and the surface microstructure of the steel ion-alloyed with carbon, boron, chromium, manganese and nickel after irradiation by He+ ions. Using Auger-electron spectroscopy, it was found that ion implantation of steel by chromium and nickel results in several per cent increase of the corresponding element concentration in the surface layer, the concentration of the second component decreasing simultaneously. The results evidence of that the impurities, which reduce the volume of the vacancy swelling in neutron bombardment, also slow down blistering caused by the irradiation of the steel by helium ions

  14. Direct nano-patterning of graphene with helium ion beams

    International Nuclear Information System (INIS)

    Helium ion microscopy (HIM) was used for direct nano-patterning of single-layer graphene (SLG) on SiO2/Si substrates. This technique involves irradiation of the sample with accelerated helium ions (He+). Doses of 2.0?×?1016?He+?cm?2 from a 30?kV beam induced a metal-insulator transition in the SLG. The resolution of HIM patterning on SLG was investigated by fabricating nanoribbons and nanostructures. Analysis of scanning capacitance microscopy measurements revealed that the spatial resolution of HIM patterning depended on the dosage of He+ in a non-monotonic fashion. Increasing the dose from 2.0?×?1016 to 5.0?×?1016?He+?cm?2 improved the spatial resolution to several tens of nanometers. However, doses greater than 1.0?×?1017?He+?cm?2 degraded the patterning characteristics. Direct patterning using HIM is a versatile approach to graphene fabrication and can be applied to graphene-based devices

  15. Aerial Deployment and Inflation System for Mars Helium Balloons

    Science.gov (United States)

    Lachenmeler, Tim; Fairbrother, Debora; Shreves, Chris; Hall, Jeffery, L.; Kerzhanovich, Viktor V.; Pauken, Michael T.; Walsh, Gerald J.; White, Christopher V.

    2009-01-01

    A method is examined for safely deploying and inflating helium balloons for missions at Mars. The key for making it possible to deploy balloons that are light enough to be buoyant in the thin, Martian atmosphere is to mitigate the transient forces on the balloon that might tear it. A fully inflated Mars balloon has a diameter of 10 m, so it must be folded up for the trip to Mars, unfolded upon arrival, and then inflated with helium gas in the atmosphere. Safe entry into the Martian atmosphere requires the use of an aeroshell vehicle, which protects against severe heating and pressure loads associated with the hypersonic entry flight. Drag decelerates the aeroshell to supersonic speeds, then two parachutes deploy to slow the vehicle down to the needed safe speed of 25 to 35 m/s for balloon deployment. The parachute system descent dynamic pressure must be approximately 5 Pa or lower at an altitude of 4 km or more above the surface.

  16. Supercritical helium circulation pump for Japan Atomic Energy Research Institute

    International Nuclear Information System (INIS)

    IHI has carried out the development of a supercritical helium circulation system in cooperation with the Japan Atomic Energy Research Institute. In July, 1989, IHI developed a supercritical helium circulation pump which led to the successful operation of the circulation system. The performance test held at JAERI proved the mechanical stability and the highest efficiency in the world of the pump in cryogenic operation. The main specifications of the single stage centrifugal pump are given. The structure of the pump is explained. The shape of the impeller, foil type self acting gas bearings as the journal bearing and the thrust bearing, and the pump casing are described. The results of the performance test on this pump are shown. The specified pressure rise of 1.5 atm can be attained in the wide flow rate range of 100-500 g/s by changing the revolution. The adiabatic efficiency of 70 % or more was verified also in the same range of flow rate, and it was found that the efficiency reached 80 % at the highest at the specified flow rate of 350 g/s. The maximum process flow rate recorded 630 g/s. (K.I.)

  17. Effect of minor elements on corrosion behavior of Ni-Cr-W superalloys in HTGR helium

    International Nuclear Information System (INIS)

    Research and development have been carried out on the new Ni-Cr-W superalloys as a component material for HTGRs with coolant outlet temperatures of around 1000degC. The basic composition, Ni-18 to 19 mass% Cr-20 to 22 mass% W, of the experimental alloys was specified in the first step. In order to examine the effect of addition of Mn, Si, B, Y and Ti on corrosion behavior in simulated HTGR helium, corrosion tests were carried out on eight heats of Ni-18 to 19 mass% Cr-20 to 22 mass% W alloys at 950 and 1000degC. Thermal cycles were given at intervals of 100h between room temperature and the each test temperature. The cumulative period of exposure to simulated HTGR helium at the each test temperature was 1000h. Based on the results obtained the following conclusions are drawn: (1) All the Ni-Cr-W alloys tested showed better resistance to general corrosion than Hastelloy XR, and also indicated better stability of the surface oxide film and less susceptibility to intergranular oxidation than the conventional Ni-Cr-W alloys. (2) The addition of Mn and Si showed no advantage. The alloys containing Mn and Si rather showed inferior corrosion resistance in simulated HTGR helium. (3) The addition of B and Y was effective to improve corrosion resistance in simulated HTGR helium. (4) Although the addition of Ti was harmful to corrosion resistance in simulated HTGR helium, around 0.08 mass% addition of Ti did not reduce corrosion resistance in the environment. (5) A new Ni-Cr-W superalloy, which shows extremely superior corrosion resistance to conventional Ni-Cr-W superalloys in simulated HTGR helium, has been developed. (author)

  18. Thermal Performance of a Dual-Channel, Helium-Cooled, Tungsten Heat Exchanger

    International Nuclear Information System (INIS)

    Helium-cooled, refractory heat exchangers are now under consideration for first wall and divertor applications. These refractory devices take advantage of high temperature operation with large delta-Ts to effectively handle high heat fluxes. The high temperature helium can then be used in a gas turbine for high-efficiency power conversion. Over the last five years, heat removal with helium was shown to increase dramatically by using porous metal to provide a very large effective surface area for heat transfer in a small volume. Last year, the thermal performance of a bare-copper, dual-channel, helium-cooled, porous metal divertor mock-up was evaluated on the 30 kW Electron Beam Test System at Sandia National Laboratories. The module survived a maximum absorbed heat flux of 34.6 MW/m2 and reached a maximum surface temperature of 593 C for uniform power loading of 3 kW absorbed on a 2-cm2 area. An impressive 10 kW of power was absorbed on an area of 24 cm2. Recently, a similar dual-module, helium-cooled heat exchanger made almost entirely of tungsten was designed and fabricated by Thermacore, Inc. and tested at Sandia. A complete flow test of each channel was performed to determine the actual pressure drop characteristics. Each channel was equipped with delta-P transducers and platinum RTDs for independent calorimetry. One mass flow meter monitored the total flow to the heat exchanger, while a second monitored flow in only one of the channels. The thermal response of each tungsten module was obtained for heat fluxes in excess of 5 MW/m2 using 50 C helium at 4 MPa. Fatigue cycles were also performed to assess the fracture toughness of the tungsten modules. A description of the module design and new results on flow instabilities are also presented

  19. Particle and energy transport studies on TFTR and implications for helium ash in future fusion devices

    Energy Technology Data Exchange (ETDEWEB)

    Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Bell, R.E.; Grek, B.; Hulse, R.A.; Johnson, D.W.; Hill, K.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.

    1993-03-01

    Local thermal particle and energy transport studies of balanced-injection L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power have been performed on TFTR. The particle transport of He[sup 2+] and electrons following a small helium gas puff and Fe[sup 24+] induced by laser ablation has been examined and compared to the local energy transport characteristics inferred from power balance analysis. All particle perturbation diffusivities are radially hollow and are similar in magnitude and shape to the effective thermal conductivities found by power balance analysis. All particle diffusivities are 1--2 orders of magnitude larger than neoclassical values, except near the magnetic axis. A reduction in the helium diffusivity D[sub He] in the Supershot as compared to the L-mode is accompanied by a similar reduction in the effective single fluid thermal conductivity [chi]fluid. Also, the helium core convective velocity V[sub He] is found to increase in the Supershot over the L-Mode for r/a < 0.5. A quasilinear model of electrostatic drift waves has been used to calculate ratios between particle and energy fluxes in the Supershot. The measured ratios of the helium and iron particle diffusivities are in good accord with predictions, as are predicted ratios of V[sub He]/D[sub He]. Modelling indicates that the similarity in magnitude and profile shape of D[sub He] and [chi]fluid has generally favorable implications for helium ash content in a future fusion reactor. The core convection found in the Supershot increases the helium concentration on axis but does not reduce the plasma reactivity significantly.

  20. Particle and energy transport studies on TFTR and implications for helium ash in future fusion devices

    Energy Technology Data Exchange (ETDEWEB)

    Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Bell, R.E.; Grek, B.; Hulse, R.A.; Johnson, D.W.; Hill, K.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.

    1993-03-01

    Local thermal particle and energy transport studies of balanced-injection L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power have been performed on TFTR. The particle transport of He{sup 2+} and electrons following a small helium gas puff and Fe{sup 24+} induced by laser ablation has been examined and compared to the local energy transport characteristics inferred from power balance analysis. All particle perturbation diffusivities are radially hollow and are similar in magnitude and shape to the effective thermal conductivities found by power balance analysis. All particle diffusivities are 1--2 orders of magnitude larger than neoclassical values, except near the magnetic axis. A reduction in the helium diffusivity D{sub He} in the Supershot as compared to the L-mode is accompanied by a similar reduction in the effective single fluid thermal conductivity {chi}fluid. Also, the helium core convective velocity V{sub He} is found to increase in the Supershot over the L-Mode for r/a < 0.5. A quasilinear model of electrostatic drift waves has been used to calculate ratios between particle and energy fluxes in the Supershot. The measured ratios of the helium and iron particle diffusivities are in good accord with predictions, as are predicted ratios of V{sub He}/D{sub He}. Modelling indicates that the similarity in magnitude and profile shape of D{sub He} and {chi}fluid has generally favorable implications for helium ash content in a future fusion reactor. The core convection found in the Supershot increases the helium concentration on axis but does not reduce the plasma reactivity significantly.

  1. Diffraction dissociation of high energy proton on helium

    International Nuclear Information System (INIS)

    Preliminary results from a measurement of the inclusive process p + 4He ? x + 4He in the region .04 less than or equal to /t/ less than or equal to.5 (GeV/c)2 and Mx2 less than or equal to 12.GeV2 for five incident proton momenta from 46 to 400 GeV/c. In this region the differential cross section d2epsilon/dtMx2 shows a t dependence of the type e /sup b/ 1 /sup t/ + de /sup b/ 2 /sup t/ and a dominant 1/Mx2 behavior for Mx2 > 5 GeV2. The measurement was performed at Fermilab by detecting slow recoil ? -particles from helium gas jet target placed at the internal beam of the accelerator. 3 references

  2. Safety in handling helium and nitrogen

    International Nuclear Information System (INIS)

    Based upon the authors' industrial experience and practices, they have provided an overview of safety in storage, handling, and transfer of both laboratory and bulk quantities of gaseous and liquid forms of nitrogen and helium. They have addressed the properties and characteristics of both the gaseous and liquid fluids, typical storage and transport containers, transfer techniques, and the associated hazards which include low temperatures, high pressures, and asphyxiation. Methods and procedures to control and eliminate these hazards are described, as well as risk remediation through safety awareness training, personal protective equipment, area ventilation, and atmosphere monitoring. They have included as an example a recent process hazards analysis performed by Air Products on the asphyxiation hazard associated with the use of liquid helium in MRI magnet systems

  3. Shear Modulus Anomaly in Solid Helium

    Science.gov (United States)

    Beamish, John; Day, James; Syshchenko, Alexander

    2008-03-01

    The search for supersolidity was given impetus by recent experiments in which solid helium appeared to decouple from a torsional oscillator, but other phenomena which characterize superflow have not yet been observed. Both experiments and theory indicate that defects are involved in supersolidity and these should also affect the solid's mechanical behavior. We have measured the shear modulus of solid helium at extremely low frequencies and strains, using a new method, and observe anomalous stiffening at temperatures below 200 mK. It has the same dependence on temperature, measurement amplitude, ^3He impurity concentration and annealing as the torsional oscillator decoupling. This elastic behavior is explained in terms of a dislocation network which is pinned by ^3He at the lowest temperatures but becomes mobile above 100 mK. Moving dislocations appear eliminate the decoupling and disrupt possible supersolidity.

  4. Electron impact excitation of helium atoms

    International Nuclear Information System (INIS)

    Two experiments have been conducted in an apparatus which was designed and constructed to study interactions between electrons and atoms. (1) The polarisation fraction of the ultra violet radiation emitted following electron impact excitation of the n1P states of helium atoms has been deduced from measurements of the angular distribution of the photons for incident electron energies from 40eV to 300eV. (2) Angular correlations between the scattered electrons resulting from the excitation of the 21P state of helium and the photons emitted in the decay of this state have been measured using the delayed coincidence technique for an incident energy of 81.2eV. The measurements extend over the electron scattering angles from 10 deg to 130 deg. (author)

  5. Single photon double ionization of helium

    International Nuclear Information System (INIS)

    we have calculated the single photon double ionization cross section of helium using the fully correlated wave function for the ground state and partially correlated wave function for the final state. Our present theoretical investigation demonstrates that the inclusion of the full correlation in the initial as well as the final state wave function is indispensable in order to obtain reliable results in the close vicinity of the threshold. (author). 56 refs, 1 fig

  6. Studies of helium distribution in metal tritides

    International Nuclear Information System (INIS)

    The distribution of helium (3He) in LiT, TiT2, and UT3, which are regarded as representative metal tritides, was investigated using pulse nuclear magnetic resonance (NMR) techniques. Analyses of the NMR lineshapes and nuclear relaxation times indicate the 3He atoms are trapped in microscopic gas bubbles for each tritide. The effects of concentration and temperature on the 3He distributions were investigated as well

  7. From atomic helium to nuclear matter

    CERN Document Server

    Fantoni, S; Schmidt, K E

    1999-01-01

    Differences between the quasiparticle and the bare particle, as constituents of Fermi systems, mainly result from the effects of correlations. Comparative studies performed in liquid helium and indicating interesting similarities in the single particle properties of Bose and Fermi liquids will be discussed, also in connection with the theoretical and experimental quasihole strength in nuclei. A new Quantum Monte Carlo method for nuclear systems is also outlined.

  8. Helium counters for low neutron flux measurements

    OpenAIRE

    D?bicki, Z.; J?drzejczak, K.; Karczmarczyk, J.; Kasztelan, M.; Lewandowski, R.; J. Orzechowski; Szabelska, B.; Szabelski, J.; Tokarski, P.; Wibig, T.

    2011-01-01

    We present a comparison of some characteristics of helium counters for measurements of low intensity neutron flux.

    We focus on neutron flux density measurements in low background laboratories. Because of an extremely low counting rate (few events per hour or less), we have concentrated on counter parameters which are sometimes meaningless under regular conditions, i.e. background from internal alpha radioactivity, percentage of events in full energy peak, and th...

  9. The energy levels of helium atom

    International Nuclear Information System (INIS)

    In our work the nonrelativistic ionization energies of helium atom are calculated for S-, P- and D-states. The calculations are based on the variational method of 'exponential' expansion. Convergence of the numerical values of variational energies is studied by increasing the number of the basis functions N. That allows to claim that the obtained energy values have 20 significant digits, both for S states and for states of nonzero angular moment

  10. Observation of the antimatter helium-4 nucleus

    OpenAIRE

    STAR collaboration

    2011-01-01

    High-energy nuclear collisions create an energy density similar to that of the universe microseconds after the Big Bang, and in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high energy accelerator of heavy nuclei is an efficient means of producing and studying antimatter. The antimatter helium-4 nucl...

  11. Pressure-driven flow of solid helium

    OpenAIRE

    Day, James; Beamish, John

    2006-01-01

    The recent torsional oscillator results of Kim and Chan suggest a supersolid phase transition in solid 4He. We have used a piezoelectrically driven diaphragm to study the flow of solid helium through an array of capillaries. Our measurements showed no indication of low temperature flow, placing stringent restrictions on supersolid flow in response to a pressure difference. The average flow speed at low temperatures was less than 1.2x10-14 m/s, corresponding to a supersolid v...

  12. Continuous superconducting level indicator for superfluid helium

    International Nuclear Information System (INIS)

    A continuous level indicator using superconducting wire is exhibited to be feasible in superfluid state of liquid helium. By an appropriate selection of diameter of wire and transport current, the normal region propagates only in the part of the wire above liquid level owing to the difference of heat transfer between the gaseous state and the superfluid state. The liquid level is detected continuously as a terminal voltage of the wire. (author)

  13. Helium in the atmospheres of binary stars

    International Nuclear Information System (INIS)

    A uniform summary of the helium content in the atmospheres of 25 bright components of binary systems is obtained using model atmospheres. On the average the He content in binary stars is higher than normal even for components which lie near the main sequence. On the Hertzsprung--Russell diagram these components are located farther from the zero-age line on the average than stars with a normal He content

  14. Double ionization of helium by He+ projectiles

    International Nuclear Information System (INIS)

    The ratio of the cross section for double ionization to the cross section for single ionization of helium produced by 25- to 625-keV/amu He+ projectiles has been measured. The results reported here are consistently higher than the values reported by Dubois et al. Above 400 keV/amu, where charge capture is small, the ratios are about the same as those reported for He2+ projectiles

  15. Molecular dynamics simulations of cumulative helium bombardments on tungsten surfaces

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed to study the cumulative bombardments of low-energy (60–200 eV) helium atoms on tungsten surfaces. The behaviour of helium and the response of tungsten surface were investigated. The helium incident energy and tungsten temperature play important roles on the formation and growth of helium clusters. The temperature can promote the coalescence of helium clusters and increase the size of the helium clusters. The rupture of the helium clusters has also been observed. During the formation of helium clusters, the interstitial tungsten atoms are produced and evolve into bundles of <1 1 1> crowdions, which would be constrained around the helium clusters for a long time. However, they will finally move onto the top surface along the <1 1 1> direction, which results in stacking the tungsten atoms on the surface. The complex combination effects of the helium clusters and the interstitial atoms result in the growth of the surfaces. Besides, several tungsten atoms were ejected from tungsten surfaces

  16. Helium storage and control system for the PBMR

    International Nuclear Information System (INIS)

    The power conversion unit will convert the heat energy in the reactor core to electrical power. The direct-closed cycle recuperated Brayton Cycle employed for this concept consists of a primary helium cycle with helium powered turbo compressors and a power turbine. The helium is actively cooled with water before the compression stages. A recuperator is used to preheat the helium before entering the core. The start of the direct cycle is initiated by a mass flow from the helium inventory and control system via a jet pump. When the PBMR is connected to the grid, changes in power demand can be followed by changing the helium flow and pressure inside the primary loop. Small rapid adjustments can be performed without changing the helium inventory of the primary loop. The stator blade settings on the turbines and compressors are adjustable and it is possible to bypass reactor and turbine. This temporarily reduces the efficiency at which the power conversion unit is operating. Larger or long term adjustments require storage or addition of helium in order to maintain a sufficient level of efficiency in the power conversion unit. The helium will be temporarily stored in high pressure tanks. After a rise in power demand it will be injected back into the system. Some possibilities how to store the helium are presented in this paper. The change of helium inventory will cause transients in the primary helium loop in order to acquire the desired power level. At this stage, it seems that the change of helium inventory does not strongly effect the stability of the power conversion unit. (author)

  17. High-frequency electrodeless discharges in helium

    Energy Technology Data Exchange (ETDEWEB)

    Denisova, N [Institut of Theoretical and Applied Mechanics, Novosibirsk, Russia (Russian Federation); Skudra, A [Institut of Atomic Physics and Spectroscopy, University of Latvia, Raina blvd.19, Riga, Latvia (Latvia)

    2004-11-01

    Modelling of high-frequency electrodeless discharges (HFEDs) in helium is presented. The model combines calculations of electromagnetic field profiles and plasma parameters including kinetics of the excited atomic states. A method of the self-consistent numerical solution for the plasma-field system is proposed. The method takes into account a temporal hierarchy of the kinetic processes in the HFED plasma. A stationary collision-radiative model for helium plasma is developed considering the following equations: (i) the transport equations for the electrons, (ii) the electron energy balance equation, (iii) the population rate equations for balance in the excited states and (iv) the electromagnetic field equations. Discharge properties are investigated in a numerical simulation. The electron density, electron temperature and absorbed power versus gas pressure and external magnetic field amplitude are obtained. The electromagnetic field profiles demonstrate a significant role of the skin effect. The intensities of the lines 587.6 and 728.1 nm are calculated, and are found to be in good agreement with the experimental data. The developed model is used to obtain optimal operation conditions of high-frequency electrodeless helium lamps.

  18. Laser Spectroscopy of Antiprotonic Helium Atoms

    CERN Multimedia

    2002-01-01

    %PS205 %title\\\\ \\\\Following the discovery of metastable antiprotonic helium atoms ($\\overline{p}He^{+} $) at KEK in 1991, systematic studies of their properties were made at LEAR from 1991 to 1996. In the first two years the lifetime of $\\overline{p}He^{+}$ in liquid and gaseous helium at various temperatures and pressures was measured and the effect of foreign gases on the lifetime of these atoms was investigated. Effects were also discovered which gave the antiproton a 14\\% longer lifetime in $^4$He than in $^3$He, and resulted in important differences in the shape of the annihilation time spectra in the two isotopes.\\\\ \\\\Since 1993 laser spectroscopy of the metastable $\\overline{p}He^{+}$ atoms became the main focus of PS205. Transitions were stimulated between metastable and non-metastable states of the $\\overline{p}He^{+}$ atom by firing a pulsed dye laser beam into the helium target every time an identified metastable atom was present (Figure 1). If the laser frequency matched the transition energy, the...

  19. Gas turbine modular helium reactor in cogeneration

    International Nuclear Information System (INIS)

    This work carries out the thermal evaluation from the conversion of nuclear energy to electric power and process heat, through to implement an outline gas turbine modular helium reactor in cogeneration. Modeling and simulating with software Thermo flex of Thermo flow the performance parameters, based on a nuclear power plant constituted by an helium cooled reactor and helium gas turbine with three compression stages, two of inter cooling and one regeneration stage; more four heat recovery process, generating two pressure levels of overheat vapor, a pressure level of saturated vapor and one of hot water, with energetic characteristics to be able to give supply to a very wide gamma of industrial processes. Obtaining a relationship heat electricity of 0.52 and efficiency of net cogeneration of 54.28%, 70.2 MW net electric, 36.6 MW net thermal with 35% of condensed return to 30 C; for a supplied power by reactor of 196.7 MW; and with conditions in advanced gas turbine of 850 C and 7.06 Mpa, assembly in a shaft, inter cooling and heat recovery in cogeneration. (Author)

  20. 5 ??? ?? ?? ??? ????????????????? ????

    Directory of Open Access Journals (Sweden)

    Khadicha Dulatova

    2004-04-01

    Full Text Available 1-?? ?????? (??????-??????? 2000«???????????? ????????????? ?????? r. ????????»2-?? ????11? (??????-??????? 2001 «????? ? ????»?-?? ?????? (??????-??????? 2002 «?????? ?? ??????»4-?? ?????? (??????-??????? 2003 «????? ? ??????????? ? ??????»5-?? ?????? (??????-??????? 2004 «????? ?????: ???????? ? ?????????????????????? ??????? ?????? ????????

  1. Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium

    Science.gov (United States)

    Steinfeldt, R.; Sültenfuß, J.; Dengler, M.; Fischer, T.; Rhein, M.

    2015-07-01

    Oceanic upwelling velocities are too small to be measured directly. The surface disequilibrium of the 3He/4He ratio provides an indirect method to infer vertical velocities at the base of the mixed layer. Samples of helium isotopes were taken from two coastal upwelling regions, off Peru on cruise M91, and off Mauritania on 3 cruises. The helium-3 flux into the mixed layer also depends on the diapycnal mixing. Direct observations of the vertical diffusivity have been performed on all 4 cruises and are also used in this study. The resulting upwelling velocities in the coastal regions vary between 1.1 × 10-5 and 2.8 × 10-5 m s-1 for all cruises. Vertical velocities off the equator can also be inferred from the divergence of the wind driven Ekman transport. In the coastal regimes, the agreement between wind and helium derived upwelling is fairly good at least for the mean values. Further offshore, the helium derived upwelling still reaches 1 × 10-5 m s-1, whereas the wind driven upwelling from Ekman suction is smaller by at least one order of magnitude. One reason for this difference might be eddy induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium derived vertical velocities and the measured vertical diffusivities. The advective part of these fluxes makes up at least 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 g C m2 d-1 off Peru and 1.6-1.9 g C m2 d-1 off Mauritania.

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

    Science.gov (United States)

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

    2014-03-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    David, M.-L., E-mail: marie-laure.david@univ-poitiers.fr; Pailloux, F. [Institut Pprime, UPR 3346 CNRS-Université de Poitiers, SP2MI, 86962 Futuroscope-Chasseneuil cedex (France); Canadian Centre for Electron Microscopy, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Alix, K.; Mauchamp, V.; Pizzagalli, L. [Institut Pprime, UPR 3346 CNRS-Université de Poitiers, SP2MI, 86962 Futuroscope-Chasseneuil cedex (France); Couillard, M.; Botton, G. A. [Canadian Centre for Electron Microscopy, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada); Department of Materials Science and Engineering, Mc Master University, 1280 Main Street West, Hamilton, Ontario L8S 4M1 (Canada)

    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.

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

    International Nuclear Information System (INIS)

    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

  5. Backscattered helium spectroscopy in the helium ion microscope: Principles, resolution and applications

    International Nuclear Information System (INIS)

    We demonstrate the possibilities and limitations for microstructure characterization using backscattered particles from a sharply focused helium ion beam. The interaction of helium ions with matter enables the imaging, spectroscopic characterization, as well as the nanometer scale modification of samples. The contrast that is seen in helium ion microscopy (HIM) images differs from that in scanning electron microscopy (SEM) and is generally a result of the higher surface sensitivity of the method. It allows, for instance, a much better visualization of low-Z materials as a result of the small secondary electron escape depth. However, the same differences in beam interaction that give HIM an edge over other imaging techniques, also impose limitations for spectroscopic applications using backscattered particles. Here we quantify those limitations and discuss opportunities to further improve the technique

  6. Feeding helium to superconducting magnets

    CERN Multimedia

    1979-01-01

    The photo shows two of the 3 superconducting magnets (two MBS dipoles (CESAR) of 150 mm bore and 4.5 T, and one quadrupole (CASTOR) of 90 mm bore and 54 T/m) which were installed in the hall EHN1 (Annual Report 1978 p. 134) and ran until 1985. They formed a section of the beam H6 travelling from target T4 (down the bottom of the photo) towards the NA30 setup followed by the NA11 setup. The two big transversal pipelines are the quench lines of the two magnets (on the right, one quadrupole and one dipole, the other dipole lays down the photo and is not visible). The Jura side of the hall is on the right.

  7. Effects of helium on mechanical properties of Armco iron

    International Nuclear Information System (INIS)

    Helium was charged into Armco iron by the decay of dissolved tritium. The effect of helium on the mechanical properties was measured as a function of temperature. Five at. ppM helium degraded the mechanical properties at temperatures greater than 8000K. Intergranular cracks formed in both strained and unstrained portions of the specimen at a temperature of about 10000K but only in the strained portion at a temperature of about 8000K. High temperature embrittlement appears to be caused by stress-assisted growth of helium bubbles. The maximum in strength caused by dynamic strain aging at about 4700K that occurs in steels was absent in Armco iron that contained tritium and helium. The reason for this absence is not clear, but helium and tritium interacting with the carbon and nitrogen may have an influence on the strength maximum

  8. Impurity control and helium exhaust experiment in JT-60

    International Nuclear Information System (INIS)

    Impurity characteristics have been investigated in high power (20 MW) NB heated discharges of outer and lower X-point configurations with TiC coated molybdenum or graphite first walls. The light impurity concentrations and Zeff had the lowest values in the outer X-point discharges with TiC coated molybdenum first walls. In high density discharges, the heat load on the divertor plate was suppressed by radiative cooling originating from carbon and hydrogen in the divertor region. To simulate the behaviour of the helium ash in a fusion reactor, helium particles were fuelled by a 30 keV helium beam or gas puffing in NB heated hydrogen plasmas. The neutral pressures of helium and hydrogen in the divertor region were proportional to n-bare3. For the helium transport in the main plasma, the inward flow pinch of helium ions was slightly more pronounced than that of the hydrogen ions. (author). 18 refs, 3 figs, 1 tab

  9. Helium in metals and its influence on their mechanical properties

    International Nuclear Information System (INIS)

    Helium in metals is investigated for different reasons: most interesting for the materials technology is the so-called ''helium embrittlement''. This is the effect of the sometimes dramatically reduced ductility and lifetime of structural materials in advanced fission reactors induced by helium. Similar effects are expected or respectively feared in future fusion reactors or large (high flux) particle accelerators (e.g. spallation neutron sources). On the other hand the system helium-metal has also gained interest in basic physical science because of special properties (e.g. ist practically unsoluable in metals). This work reviews the present knowledge of the physical properties of the helium precipitates (so-called helium bubbles) in metals as well as the effects of them on the mechanical properties of structural metals and alloys. It should be emphasized that this work more describes the present understanding of the underlying mechanisms of the observed effects than completely lists all the work done in the field. (orig.)

  10. Experimental Validation of the LHC Helium Relief System Flow Modeling

    CERN Document Server

    Fydrych, J; Riddone, G

    2006-01-01

    In case of simultaneous resistive transitions in a whole sector of magnets in the Large Hadron Collider, the helium would be vented from the cold masses to a dedicated recovery system. During the discharge the cold helium will eventually enter a pipe at room temperature. During the first period of the flow the helium will be heated intensely due to the pipe heat capacity. To study the changes of the helium thermodynamic and flow parameters we have simulated numerically the most critical flow cases. To verify and validate numerical results, a dedicated laboratory test rig representing the helium relief system has been designed and commissioned. Both numerical and experimental results allow us to determine the distributions of the helium parameters along the pipes as well as mechanical strains and stresses.

  11. Defects and morphological changes in nanothin Cu films on polycrystalline Mo analyzed by thermal helium desorption spectrometry

    International Nuclear Information System (INIS)

    Thermal helium desorption spectrometry (THDS) has been used for the investigation of defects and thermal stability of thin Cu films (5-200 A ) deposited on a polycrystalline Mo substrate in ultrahigh vacuum. These films are metastable at room temperature. On heating, the films transform into islands, giving rise to a relatively broad peak in the helium desorption spectra. The temperature of this island formation is dependent on film thickness, being 417 K for 10 A and 1100 K for a 200 A film. The activation energy for island formation was found to be 0.3±0.1 eV for 75 A film. Grain boundaries have a strong effect on island formation. The defect concentration in the as-deposited films is ?5x10-4, for films thicker than 50 A and more for thinner films. Helium release from monovacancies was identified in the case of a 200 A film. Helium release was also seen during sublimation of the Cu film (?1350 K). Overlayer experiments were used to identify helium trapped close to the film surface. An increase of the substrate temperature during deposition resulted in a film that had already formed islands. Argon-ion assistance (250 eV) during film deposition with an ion/atom ratio of ?0.1 resulted in a significant enhancement of helium trapping in the films. The argon concentration in the films was found to be 10-3. The temperature of island formation was increased due to argon-ion assistance. The helium and argon desorption spectra are found to be similar, which is due to most of the helium becoming trapped in the defects created by the argon beam. The role of the Mo surface in affecting the defects at the film-substrate interface is investigated. The effect of variation of helium fluence and helium implantation energy is also considered. The present THDS results of Cu/poly-Mo are compared to those of Cu/Mo(100) and Cu/Mo(100) reported earlier

  12. Orientation, alignment and polarisation in electron-helium collisions

    International Nuclear Information System (INIS)

    In this thesis electron-photon coincidence experiments to study the excitation of helium by electron impact are updated. This is achieved by cross firing a well collimated and mono-energetic electron beam with a thermal helium beam and measuring the angular and/or polarisation distribution of the decay photons in coincidence with the inelastically scattered electrons. In this way target parameters are determined for the 21P, 31P, 31D and 33P states of helium. (Auth.)

  13. Stable Compound of Helium and Sodium at High Pressure

    OpenAIRE

    Dong, Xiao; Oganov, Artem R.; Goncharov, Alexander F.; Stavrou, Elissaios; Lobanov, Sergey; Saleh, Gabriele; Qian, Guang-Rui; Zhu, Qiang; Gatti, Carlo; Xiang-feng ZHOU; Prakapenka, Vitali; Konôpková, Zuzana; Wang, Hui-Tian

    2013-01-01

    Helium, on a par with neon, is the most chemically inert element in the Periodic Table. Due to its extremely stable closed-shell electronic configuration with record-high ionization potential and nearly zero electron affinity, helium is not known to form thermodynamically stable compounds (with the exception of inclusion compounds with weak van der Waals bonding). Here we report the discovery of a thermodynamically stable compound of helium and sodium, Na2He, which has a flu...

  14. A phase transition model for the helium supercooling

    OpenAIRE

    Elena, Bonetti; Michel, Fremond

    2012-01-01

    We build a predictive theory for the evolution of mixture of helium and supercooled helium at low temperature. The absolute temperature and the volume fraction of helium, which is dominant at temperature larger than the phase change temperature, are the state quantities. The predictive theory accounts for local interactions at the microscopic level, involving the gradient of $\\beta$. The nonlinear heat flux in the supercooled phase results from a Norton-Hoff potential. We pr...

  15. Doppler imaging of the helium-variable star a Cen

    OpenAIRE

    Bohlender, David A.; Rice, J B; Hechler, P.

    2010-01-01

    The helium-peculiar star a Cen exhibits line profile variations of elements such as iron, nitrogen and oxygen in addition to its well-known extreme helium variability. New high S/N, high-resolution spectra are used to perform a quantitative measurement of the abundances of the star and determine the relation of the concentrations of the heavier elements on the surface of the star to the helium concentration and the magnetic field orientation. Doppler images have been created...

  16. Precision Cutting and Patterning of Graphene with Helium Ions

    OpenAIRE

    Bell, David C.; Lemme, Max; Stern, L. A.; Williams, J. R.; Marcus, Charles Masamed

    2009-01-01

    We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on \\(Si/SiO_2\\) substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge p...

  17. Mixing, Enhanced Helium and Blue Tails in Globular Clusters

    OpenAIRE

    Caloi, V.

    2000-01-01

    We investigate the consequences of an increase in the envelope helium abundance of pre-helium flash red giants in globular clusters. Comparing predictions with the CM diagrams of a few crucial GC, one finds no evidence for a substantial increase in the surface helium content of HB members of these clusters, at least for objects in the RR Lyrae region or close to it. The possibility that the most peculiar giants belong to the asymptotic giant branch is discussed. The conseque...

  18. Interaction of phonons at superfluid helium-solid interfaces

    OpenAIRE

    Adamenko, I. N.; Nemchenko, E. K.

    2014-01-01

    A new method of obtaining the interaction Hamiltonian of phonons at superfluid helium-solid interface is proposed in the work. Equations of hydrodynamic variables are obtained in terms of second quantization if helium occupies a half-space. The contributions of all processes to the heat flux from solid to superfluid helium are calculated based on the obtained Hamiltonian. The angular distribution of phonons emitted by a solid is found in different processes. It is shown that...

  19. Experimental investigation of positron self-trapping near the vapour-liquid critical point of helium-4

    International Nuclear Information System (INIS)

    Positron self-trapping in helium near the vapour-liquid critical point is investigated using the positron annihilation lifetime technique. A 13% decrease in the slowing-down time for positrons to reach the self-trapped state is observed at te critical temperature 5.190 K relative to the slowing-down time at 5.200 K. (author)

  20. Helium, from He3 Superfluid to Alpha-spin

    Science.gov (United States)

    Hidajatullah-Widastra, Fatahillah; Hidajatullah-Maksoed, Widastra

    2015-04-01

    Accompanying helium-using of ``Two Eagles'' balloon group 2015 World record pacificballoon.com@Flight-Status.php, superfluid He3 offers a unique ``testing ground'' for rapid phase transitions. Recent experiments where a rotating superfluid He3 was locally heated well above the critical temperature by absorption of neutrons [4,5] receved vortex formation under a rapid 2nd order phase transition-I.S. Aranson, et al., Physica C, ``Vortex Matter in Superconductors at Extreme SCALES and Conditions'', v 332, n 1-4, May 2000, h 129. Further for ``alpha-spin resembles the vortex formed as a consequence of the interaction of 4 vortexes'' sought the ``it will be sufficient to calculate the energy shift with the singlet & triplet m = 0-S Gasiorowics: ``Quantum Physics'',2003, h 220 Great acknowledgements to HE. Mr. Drs. P. SWANTORO/Kompas-Gramedia Group.

  1. Measurements of neutral helium density in helicon plasmas.

    Science.gov (United States)

    Houshmandyar, Saeid; Sears, Stephanie H; Thakur, Saikat Chakraborty; Carr, Jerry; Galante, Matthew E; Scime, Earl E

    2010-10-01

    Laser-induced-fluorescence (LIF) is used to measure the density of helium atoms in a helicon plasma source. For a pump wavelength of 587.725 nm (vacuum) and laser injection along the magnetic field, the LIF signal exhibits a signal decrease at the Doppler shifted central wavelength. The drop in signal results from the finite optical depth of the plasma and the magnitude of the decrease is proportional to the density of excited state neutral atoms. Using Langmuir probe measurements of plasma density and electron temperature and a collisional-radiative model, the absolute ground state neutral density is calculated from the optical depth measurements. Optimal plasma performance, i.e., the largest neutral depletion on the axis of the system, is observed for antenna frequencies of 13.0 and 13.5 MHz and magnetic field strengths of 550-600 G. PMID:21033897

  2. Hyperfine Structure of S-States in Muonic Helium Ion

    CERN Document Server

    Martynenko, A P

    2007-01-01

    Corrections of orders alpha^5 and alpha^6 are calculated in the hyperfine splittings of 1S and 2S - energy levels in the ion of muonic helium. The electron vacuum polarization effects, the nuclear structure corrections and recoil corrections are taken into account. The obtained numerical values of the hyperfine splittings -1334.56 meV (1S state), -166.62 meV (2S state) can be considered as a reliable estimate for the comparison with the future experimental data. The hyperfine splitting interval Delta_{12}=(8 Delta E^{hfs}(2S)- Delta E^{hfs}(1S)) = 1.64 meV can be used for the check of quantum electrodynamics.

  3. Detection of ordering of electrons on liquid helium

    International Nuclear Information System (INIS)

    The ordering is observed for surface densities 1.5 108 8 cm-2 at temperatures 0.3 < T < 0.8 K by monitoring the response to a 25 MHz in plane electric field polarized parallel to its wave vector. Ordering influences this susceptibility by the shift in frequency of the plasmon modes as the electrons correlate and so self-trap into the surface deformation they impose on the helium. This experiment is sensitive to the optical mode of the coupled systems (electron and surface deformation move in antiphase), whereas the first observation of ordering by Grimes and Adams was based on the appearance of the acoustical modes (electron + deformation move in phase). Our results for the ordering temperatures can be expressed by n(c) approximately T(c)sup(1.8+-0.2), or, if one fits the results GAMMA(c)=118+-10. It seems that the optical modes establish themselves before the acoustic modes

  4. Stopping Power of Solid Argon for Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; BØttiger, JØrgen

    1981-01-01

    By means of the Rutherford-backscattering method, the stopping cross section of solid argon has been measured for 0.5–3 MeV helium ions to an accuracy of not, vert, similar3%. The results agree within the experimental accuracies with our earlier measurements for gaseous argon over the energy region studied. This proves that the gas/solid difference for argon predicted in recent stopping-power tabulations is significantly overestimated. With high-order Z1 correction terms included in the theoretical description, calculated shell corrections based on the Lindhard-Scharff model are in good agreement with the experimental results even down to energies close to 0.6 MeV.

  5. Dipole moments of molecules solvated in helium nanodroplets

    International Nuclear Information System (INIS)

    Stark spectra are reported for hydrogen cyanide and cyanoacetylene solvated in helium nanodroplets. The goal of this study is to understand the influence of the helium solvent on measurements of the permanent electric dipole moment of a molecule. We find that the dipole moments of the helium solvated molecules, calculated assuming the electric field is the same as in vacuum, are slightly smaller than the well-known gas-phase dipole moments of HCN and HCCCN. A simple elliptical cavity model quantitatively accounts for this difference, which arises from the dipole-induced polarization of the helium

  6. Development of a Polarized Helium-3 Ion Source for RHIC

    Science.gov (United States)

    Epstein, Charles; Milner, Richard; Maxwell, James; Alessi, James; Pikin, Alexander; Zelenski, Anatoli

    2012-10-01

    A polarized Helium-3 beam in RHIC would enable new, unique, high-energy QCD studies of neutron structure with existing polarized proton beams, as well as fundamental tests of the standard model in a future electron-ion collider eRHIC. An MIT-BNL collaboration is developing a polarized Helium-3 ion source for RHIC, and initial construction is underway. Helium-3 atoms will first be polarized through metastability exchange optical pumping and then transferred to the RHIC Electron Beam Ion Source (EBIS). Fully stripped Helium-3 ions would be extracted from EBIS and their polarization measured at low energies before acceleration in RHIC.

  7. Helium vs. Proton Induced Displacement Damage in Electronic Materials

    Science.gov (United States)

    Ringo, Sawnese; Barghouty, A. F.

    2010-01-01

    In this project, the specific effects of displacement damage due to the passage of protons and helium nuclei on some typical electronic materials will be evaluated and contrasted. As the electronic material absorbs the energetic proton and helium momentum, degradation of performance occurs, eventually leading to overall failure. Helium nuclei traveling at the same speed as protons are expected to impart more to the material displacement damage; due to the larger mass, and thus momentum, of helium nuclei compared to protons. Damage due to displacement of atoms in their crystalline structure can change the physical properties and hence performance of the electronic materials.

  8. Helium irradiation effects for deuterium retention in boron coating films

    International Nuclear Information System (INIS)

    TDS analyses have been performed in order to examine helium irradiation effects for deuterium retention in boron coating films prepared by PACVD. It is clarified that the deuterium retention is reduced due to the irradiation prior to deuterium. There is no correlation between the retention variations of deuterium and helium, and thus the helium occupation seems hardly to contribute to the reduction. The third peaks in the TDS spectra shift on the high temperature side with the irradiation fluence. It is presumed that helium irradiation forms certain layers by knocking on boron atoms, in which deuterium retention is partly restricted, and trapped deuterium needs higher energy for the desorption

  9. Cooling performance of helium-gas/water coolers in HENDEL

    International Nuclear Information System (INIS)

    The helium engineering demonstration loop (HENDEL) has four helium-gas/water coolers where the cooling water flows in the tubes and helium gas on the shell side. Their cooling performance was studied using the operational data from 1982 to 1991. The heat transfer of helium gas on the shell was obtained for segmental and step-up baffle type coolers. Also, the change with operation time was investigated. The cooling performance was lowered by the graphite powder released from the graphite components for several thousand hours and thereafter recovered because the graphite powder from the components was reduced and the powder in the cooler shell was blown off during the operation. (orig.)

  10. Modelling of Helium-mediated Quench Propagation in the LHC Prototype Test String-1

    CERN Document Server

    Chorowski, M; Serio, L; Van Weelderen, R

    2000-01-01

    The Large Hadron Collider (LHC) prototype test string-1, hereafter referred to as the string, is composed of three ten-meter long prototype dipole magnets and one six-meter long prototype quadrupole magnet. The magnets are immersed in a pressurized static bath of superfluid helium that is maintained at a pressure of about 1 bar and at a temperature of about 1.9 K. This helium bath constitutes one single hydraulic unit, extending along the 42.5 m of the string length. We have measured the triggering of quenches of the string magnets due to the quenching of a single dipole magnet located at the string's extremity; i.e. "quench propagation". Previously reported measurements enabled to establish that in this configuration the quench propagation is mediated by the helium and not by the inter-magnet busbar connections [1], [2]. We present a model of helium mediated quench propagation based on the qualitative conclusions of these two previous papers, and on additional information gained from a dedicated series of qu...

  11. Proton-helium elastic scattering from 45 to 400 GeV

    International Nuclear Information System (INIS)

    The elastic proton-helium differential cross section has been determined for incident laboratory energies from 45 to 400 GeV in the range 0.003 2 by means of the internal gas jet target technique. The differential cross section drops 4-5 orders of magnitude to the first dip at |t| approximately equal to 0.22 (GeV/c)2. The shrinkage in the slope of the differential cross section is found to be twice as fast as that in the proton-proton case. The slope parameter at |t| approximately equal to 0 is described by the formula b=24+1.13 ln s. The elastic proton-helium cross section is normalized to the known elastic proton-proton cross section using data taken with a helium and hydrogen mixture as a target. The proton-helium total cross section is determined from the optical theorem. The total cross section rises by 4% between 100 GeV and 400 GeV. Results are presented on the real part of the elastic scattering amplitude and on the total elastic cross section. The experimental differential cross sections are compared to Glauber model predictions

  12. Stable isotopes of helium, nitrogen and carbon in a coastal submarine hydrothermal system

    International Nuclear Information System (INIS)

    Geothermal gases from submarine and subaerial hot springs in Ensenada, Baja California Norte, Mexico, were sampled for determination of gas chemistry and helium, nitrogen and stable carbon isotope composition. The submarine hot spring gas is primarily nitrogen (56.1% by volume) and methane (43.5% by volume), whereas nearby subaerial hot spring gases are predominantly nitrogen (95-99% by volume). The N2/Ar ratios and delta15N values of the subaerial hot spring gas indicate that it is atmospheric air, depleted in oxygen and enriched in helium. The submarine hot spring gas is most probably derived from marine sediments of Cretaceous age rich in organic matter. CH4 is a major component of the gas mixture (delta13C=-44.05per mill), with only minor amounts of CO2(delta13C=-10.46per mill). The delta15N of N2 is +0.2per mill with a very high N2/Ar ratio of 160. The calculated isotopic equilibration temperature for CH4-CO2 carbon exchange at depth in the Punta Banda submarine geothermal field is approximately 2000C in agreement with other geothermometry estimates. The 3He/4He ratios of the hot spring gases range from 0.3 to 0.6 times the atmospheric ratio, indicating that helium is predominantly derived from the radioactive decay of U and Th within the continental crust. Thus, not all submarine hydrothermal systems are effective vehicles for mantle degassing of primordial helium. (orig.)

  13. Fission neutron irradiation of copper containing implanted and transmutation produced helium

    International Nuclear Information System (INIS)

    The objective of this effort is to determine the factors which control the radiation-induced evolution of microstructure in copper. High purity copper containing approximately 100 appm helium was produced in two ways. In the first, helium was implanted by cyclotron at Harwell at 323K. In the second method, helium was produced as a transmutation product in 800 MeV proton irradiation at Los Alamos, also at 323K. The distributions of helium prior to fission neutron irradiation were determined by a combination of transmission electron microscopy (TEM) and positron annihilation techniques (PAT). These specimens, together with pure copper, were then irradiated with fission neutrons in a single capsule in Fast Flux Test Facility (FFTF) at ?686± 5K to a dose level of ?48 dpa (7.7 x 1026nm-2; E > 0.1 MeV). Investigation of the void and dislocation microstructures in the three specimens by TEM showed large differences between the specimens in void size and swelling. The observed differences as well as the effect of the presence of other transmutation-produced impurity atoms in the 800 MeV proton irradiated copper will be discussed

  14. Soil-gas helium and surface-waves detection of fault zones in granitic bedrock

    Indian Academy of Sciences (India)

    G K Reddy; T Seshunarayana; Rajeev Menon; P Senthil Kumar

    2010-10-01

    Fracture and fault networks are conduits that facilitate groundwater movement in hard-rock terrains.Soil-gas helium emanometry has been utilized in Wailapally watershed,near Hyderabad in southern India,for the detection of fracture and fault zones in a granite basement terrain having a thin regolith.Based on satellite imagery and geologic mapping,three sites were selected for detailed investigation.High spatial resolution soil-gas samples were collected at every one meter at a depth of <1.5m along 100 m long pro?les (3 in number).In addition,deep shear-wave images were also obtained using the multichannel analysis of surface waves.The study clearly indicates several soil-gas helium anomalies (above 200 ppb)along the pro ?les,where the shear-wave velocity images also show many near-surface vertical low velocity zones.We thus interpret that the soil-gas helium anomalous zones and the vertical low-velocity zones are probable traces of fault/fracture zones that could be efficient natural recharge zones and potential groundwater conduits.The result obtained from this study demonstrates the efficacy of an integrated approach of soil-gas helium and the seismic methods for mapping groundwater resource zones in granite/gneiss provinces.

  15. Comparison experiments of neon and helium buffer gases cooling in trapped 199Hg+ ions linear trap

    International Nuclear Information System (INIS)

    The influences of different buffer gas, neon and helium, on 199Hg+ clock transition are compared in trapped 199Hg+linear trap. By the technique of time domain's Ramsey separated oscillatory fields, the buffer gas pressure frequency shifts of 199Hg+ clock transition are measured to be (df/dPNe)(1/f) = 1.8 × 10?8 Torr?1 for neon and (df/dPHe)(1/f) = 9.1×10?8 Torr?1 for helium. Meanwhile, the line-width of 199Hg+ clock transition spectrum with the buffer gas neon is narrower than that with helium at the same pressure. These experimental results show that neon is a more suitable buffer gas than helium in 199Hg+ ions microwave frequency standards because of the 199Hg+ clock transition is less sensitive to neon variations and the better cooling effect of neon. The optimum operating pressure for neon is found to be about 1.0×10?5 Torr in our linear ion trap system. (atomic and molecular physics)

  16. Retention and surface blistering of helium irradiated tungsten as a first wall material

    International Nuclear Information System (INIS)

    The first wall of an inertial fusion energy reactor may suffer from surface blistering and exfoliation due to helium ion irradiation and extreme temperatures. Tungsten is a candidate for the first wall material. A study of helium retention and surface blistering with regard to helium dose, temperature, pulsed implantation, and tungsten microstructure was conducted to better understand what may occur at the first wall of the reactor. Single crystal and polycrystalline tungsten samples were implanted with 1.3 MeV 3He in doses ranging from 1019 m-2 to 1022 m-2. Implanted samples were analyzed by 3He(d,p)4He nuclear reaction analysis and 3He(n,p)T neutron depth profiling techniques. Surface blistering was observed for doses greater than 1021 He/m2. For He fluences of 5 x 102 He/m2, similar retention levels in both microstructures resulted without blistering. Implantation and flash heating in cycles indicated that helium retention was mitigated with decreasing He dose per cycle

  17. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets

    Science.gov (United States)

    Chen, Lei; Zhang, Jie; Freund, William M.; Kong, Wei

    2015-07-01

    We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs+ is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs+-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 106 helium atoms when the source temperature is between 14 K and 17 K.

  18. Carburization of austenitic alloys by gaseous impurities in helium

    International Nuclear Information System (INIS)

    The carburization behavior of Alloy 800H, Inconel Alloy 617 and Hastelloy Alloy X in helium containing various amounts of H2, CO, CH4, H2O and CO2 was studied. Corrosion tests were conducted in a temperature range from 649 to 10000C (1200 to 18320F) 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 ?atm H2, 450 ?atm CO, 50 ?atm CH4 and 50 ?atm H2O for Environment A; 200 ?atm H2, 100 ?atm CO, 20 ?atm CH4, 50 ?atm H2O and 5 ?atm CO2 for Environment B; 500 ?atm H2, 50 ?atm CO, 50 ?atm CH4 and 2O for Environment C; and 500 ?atm H2, 50 ?atm CO, 50 ?atm CH4 and 1.5 ?atm H2O 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

  19. Research and development for the high-temperature helium-leak detection system (Joint research). Part 2. Development of temperature sensors using optical fibre for the HTTR

    Energy Technology Data Exchange (ETDEWEB)

    Sakaba, Nariaki; Nakazawa, Toshio; Kawasaki, Kozo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Urakami, Masao; Saisyu, Sadanori [Japan Atomic Power Co., Tokyo (Japan)

    2003-03-01

    In the second stage of the research and development for a high-temperature helium-leak detection system, the temperature sensor using optical fibres was studied. The sensor detects the helium leakage by the temperature increase surrounded optical fibre with or without heat insulator. Moreover, the applicability of high temperature equipments as the HTTR system was studied. With the sensor we detected 5.0-20.0 cm{sup 3}/s helium leakages within 60 minutes. Also it was possible to detect earlier when the leakage level is at 20.0 cm {sup 3}/s. (author)

  20. Helium sources to groundwater in active volcanic terrain, and implications for tritium-helium dating at Mount St. Helens

    International Nuclear Information System (INIS)

    Groundwater helium sources and residence times were investigated using groundwater discharging from springs surrounding Mount St. Helens in the Cascades region of the United States. Significant contributions of mantle helium were found in all samples and are attributable to interaction between groundwater and magmatic gases. Bounding calculations for residence times were made on the basis of helium isotope mixing plots and historical tritium data. (authors)

  1. Helium-3 and Helium-4 acceleration by high power laser pulses for hadron therapy

    CERN Document Server

    Bulanov, S S; Schroeder, C B; Leemans, W P; Bulanov, S V; Margarone, D; Korn, G; Haberer, T

    2015-01-01

    The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (Magnetic Vortex Acceleration and hole-boring Radiation Pressure Acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the ...

  2. 76 FR 30362 - Federal Acquisition Regulation; Submission for OMB Review; Acquisition of Helium

    Science.gov (United States)

    2011-05-25

    ...; Submission for OMB Review; Acquisition of Helium AGENCY: Department of Defense (DOD), General Services... approved information collection requirement concerning acquisition of helium. Public comments are... Collection 9000- 0113, Acquisition of Helium, by any of the following methods: Regulations.gov :...

  3. Hyperspherical adiabatic approach for the helium atom

    International Nuclear Information System (INIS)

    The nonadiabatic ground state for the helium atom is obtained with the hyperspherical adiabatic approach. Potential curves, nonadiabatic couplings, and channel functions are calculated by a numerically exact procedure based on the analytical expansion of the channel functions. The coupled radial equations are solved by standard techniques. The convergence of the procedure is investigated as nonadiabatic couplings are systematically introduced. The inclusion of 11 potential curves and channel functions gives a ground-state energy that differs from the best variational calculation by 0.1 parts per million

  4. Vortex dimples at charged helium interfaces

    International Nuclear Information System (INIS)

    The authors have investigated theoretically the profile of electrically charged helium interfaces in the presence of a superfluid vortex line perpendicular to the interface. The free surface of superfluid 3He-B as well as the interface between phase-separated 3He and 4He mixtures have been considered. The superflow-induced dimple profile around the vortex line was calculated within the linear theory assuming a weak curvature of the interface. Our results show that the depth of the dimple increases strongly with an external electric field as the critical value of the electrohydrodynamic surface instability is approached. The chances of observing these charge-enhanced dimples are also discussed

  5. Interaction of antiprotons with helium and astrophysics

    Energy Technology Data Exchange (ETDEWEB)

    Sapozhnikov, M.G.

    1985-06-01

    It has been suggested by Zel'dovich et al. that knowledge of the probability of the annihilation of antiprotons in helium can lead to limits on a number of astrophysical parameters that are closely connected with predictions of unified models of all fundamental interactions. The probability of this process was studied experimentally on the LEAR (Low Energy Antiproton Ring) facility at CERN. This made possible the first fully experimental determination of limits on the amount of antimatter in the early universe. 12 references.

  6. Fano Resonances observed in Helium Nanodroplets

    CERN Document Server

    LaForge, A C; Jabbari, G; Gokhberg, K; Kryzhevoi, N V; Krishnan, S R; Hess, M; O'Kee?e, P; Ciavardini, A; Prince, K C; Richter, R; Moshammer, R; Cederbaum, L S; Pfeifer, T; Stienkemeier, F; Mudrich, M

    2015-01-01

    Doubly-excited Rydberg states of helium (He) nanodroplets have been studied using synchrotron radiation. We observed Fano resonances related to the atomic N = 2,0 series as a function of droplet size. Although similar qualitatively to their atomic counterparts, the resonance lines are broader and exhibit a shift in energy which increases for the higher excited states. Furthermore, additional resonances are observed which are not seen in atomic systems. We discuss these features in terms of delocalized atomic states perturbed by the surrounding He atoms and compare to singly excited droplets.

  7. Pressure-driven flow of solid helium

    CERN Document Server

    Day, J; Day, James; Beamish, John

    2006-01-01

    The recent torsional oscillator results of Kim and Chan suggest a supersolid phase transition in solid 4He. We have used a piezoelectrically driven diaphragm to study the flow of solid helium through an array of capillaries. Our measurements showed no indication of low temperature flow, placing stringent restrictions on supersolid flow in response to a pressure difference. The average flow speed at low temperatures was less than 1.2x10-14 m/s, corresponding to a supersolid velocity at least 7 orders of magnitude smaller than the critical velocities inferred from the torsional oscillator measurements.

  8. Production of thorium-229 using helium nuclei

    Science.gov (United States)

    Mirzadeh, Saed (Knoxville, TN) [Knoxville, TN; Garland, Marc Alan (Knoxville, TN) [Knoxville, TN

    2010-12-14

    A method for producing .sup.229Th includes the steps of providing .sup.226Ra as a target material, and bombarding the target material with alpha particles, helium-3, or neutrons to form .sup.229Th. When neutrons are used, the neutrons preferably include an epithermal neutron flux of at least 1.times.10.sup.13 n s.sup.-1cm.sup.-2. .sup.228Ra can also be bombarded with thermal and/or energetic neutrons to result in a neutron capture reaction to form .sup.229Th. Using .sup.230Th as a target material, .sup.229Th can be formed using neutron, gamma ray, proton or deuteron bombardment.

  9. Stability of the Helium-Antiproton System

    Science.gov (United States)

    Drachman, Richard J.

    2006-01-01

    In the course of their Born-Oppenheimer calculations of this system Todd and Armour noted that the lowest-lying state closely resembles the hydrogen negative ion, since the antiproton lies very close to the helium nucleus and shields one unit of nuclear charge. In the present paper this observation will be taken seriously to produce a variationally correct estimate of the total energy of this system, along with a similar estimate of the energy of the once-ionized system. The nonadiabatic effect of exactly treating the reduced masses improves the results.

  10. Pressure-Driven Flow of Solid Helium

    Science.gov (United States)

    Day, James; Beamish, John

    2006-03-01

    The recent torsional oscillator results of Kim and Chan show an anomalous mass decoupling, interpreted by the authors as a supersolid phase transition, in solid He4. We have used a piezoelectrically driven diaphragm to study the flow of solid helium through an array of capillaries. Our measurements showed no indication of low temperature flow, placing stringent restrictions on supersolid flow in response to a pressure difference. The average flow speed at low temperatures was less than 1.2×10-14m/s, corresponding to a supersolid velocity at least 7 orders of magnitude smaller than the critical velocities inferred from the torsional oscillator measurements.

  11. Attosecond Quantum-Beat Spectroscopy in Helium

    CERN Document Server

    Shivaram, Niranjan; Timmers, Henry; Sandhu, Arvinder

    2015-01-01

    The evolution of electron wavepackets determines the course of many physical and chemical phenomena and attosecond spectroscopy aims to measure and control such dynamics in real-time. Here, we investigate radial electron wavepacket motion in Helium by using an XUV attosecond pulse train to prepare a coherent superposition of excited states and a delayed femtosecond IR pulse to ionize them. Quantum beat signals observed in the high resolution photoelectron spectrogram allow us to follow the field-free evolution of the bound electron wavepacket and determine the time-dependent ionization dynamics of the low-lying 2p state.

  12. Leak testing using helium leak detector

    International Nuclear Information System (INIS)

    Most of the equipment used in the industry and particularly in the nuclear activity need to be, vacuum or pressure tight, for operative and safety requirements. These devices have to satisfy particular regulations in order to be qualified by means of operating licences. One of the most efficient system to ensure leaktightnes is using a helium leak detector with a mass spectrometer. In this paper we show the equipment and the devices employed in fuel rods fabrication for CAREM project, and some typical material defects. Operating system and the sensitivity of this method is also described. (author)

  13. Modular Helium Reactor (MHR) for oil sands extraction

    International Nuclear Information System (INIS)

    Oil sands extraction is a very important industry for Canada, which continues to grow. It has been estimated that Athabasca region in northern Alberta has at least 1.6 trillion barrels of oil contained in oil sands, while the world liquid oil reserves are estimated as less than 1.0 trillion barrels. Strip mining can access only about 10% of the oil sand reserves, thus accessing most reserves involves in-situ technologies such as Steam Assisted Gravity Draining (SAGD). However, the SAGD process requires large amounts of high-temperature, high-pressure steam, which is currently being produced by burning natural gas. High-temperature nuclear reactors such as Modular Helium Reactor (MHR) present an alternative viable source of this steam, which can avoid the consumption of large amounts of natural gas and eliminate CO2 emissions. MHR technology has been under development in the US since the middle 1950s. It is the only nuclear technology demonstrated so far which is capable of achieving coolant outlet temperatures in the range of 700 - 1000oC. Several gas-cooled reactor plants have been built and operated to-date worldwide. The Modular Helium Reactor (MHR) has improved safety features, such as passive cooling. Coated fuel particles, annular core geometry with prismatic graphite elements used for the core structure material and as a moderator, along with helium as a coolant, distinguish the MHR from other gas cooled reactors and provide for its unique high-temperature and passive safety capabilities. Modularity is another important feature of the MHR. The 350 MW(t) MHR has been developed for electricity generation using a steam cycle, and has a net plant efficiency of 38.4%. One reactor module is capable of producing about 13,000 tons of steam per day. Such a reactor plant is therefore directly applicable to the oil sands extraction using the SAGD process. In this paper we present a flow diagram of a reactor plant co-producing electricity and steam for the SAGD process, with the use of a steam-to-steam re-boiler. With a steam-to-oil ratio as 2.5, one 350 MW(t) MHR unit provides steam and power for a 30,000 barrels per day oil sands extraction plant. Depending on the project, oil sands extraction plant may be required to expand over time. Such an expansion will be enabled by providing additional MHR units, thus taking advantage of MHR modularity.

  14. Study on control method of natural circulation by injection of helium gas

    International Nuclear Information System (INIS)

    This study is to investigate a control method of natural circulation of air by injection of helium gas. A depressurization accident is one of the design-basis accidents of a very high temperature reactor (VHTR). When the primary pipe rupture accident occurs in the VHTR, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Finally, it seems to be probable that the natural circulation flow of air in the reactor pressure vessel produce continuously. In order to predict or analyze the air ingress phenomena during the depressurization accident of the VHTR, therefore, it is important to develop the method for prevention of air ingress during the accident. The experiment has been carried out regarding natural circulation using a circular tube consisting of a reverse U-shaped type. The vertical channel consists of the one side heated tube and the other side cooled tube. The experimental procedure is as follows. Firstly, the apparatus is filled with air and one vertical tube is heated. Then, natural circulation of air will be produced in the channel. After the steady state is established, a very small amount of helium gas injects from the top of the channel. The velocity, temperature of gas, and temperature of the tube wall are measured during the experiment. The analysis also has been carried out regarding natural circulation. The results were obtained as follows. The temperature difference between the vertical pipes was 50–130 K, and a small amount of helium gas injected to the channel. The volume of injected helium gas is about 3.5–10% of the total volume of the channel. When the temperature difference between the vertical tubes was kept at 52 K, the velocity of natural circulation flow became about 0.12 m/s. During a steady state, a small amount of helium gas injected into the channel. Then, the flow velocity of natural circulation suddenly decreased. The volume of injected helium gas is about 3% of the total volume of the channel. The velocity became around zero. After 1500 s elapsed, the natural circulation suddenly produced again. The experimental and analytical results show that the natural circulation flow of air can be controlled by injecting of helium gas

  15. Diffusion of helium in carbonates: Effects of mineral structure and composition

    Science.gov (United States)

    Cherniak, D. J.; Amidon, W.; Hobbs, D.; Watson, E. B.

    2015-09-01

    Diffusion of helium has been characterized in four carbonates: calcite, dolomite, magnesite, and aragonite. Cleaved or oriented and polished slabs of carbonate minerals were implanted with 100 keV or 3 MeV 3He at doses of 5 × 10153He/cm2 and 1 × 10163He/cm2, respectively, and annealed in 1-atm furnaces. 3He distributions following diffusion experiments were measured with nuclear reaction analysis using the reaction 3He(d,p)4He. Our results show that He diffusion in calcite is the fastest among the carbonates studied, with diffusivities progressively slower in magnesite, dolomite and aragonite. In the case of the isomorphic trigonal carbonates (calcite, dolomite, magnesite), these observations are broadly consistent with predictions based on lattice characteristics such as unit cell size and inter-atomic apertures, with diffusivities faster in more open carbonate structures. Dolomite is an exception to this trend, suggesting that its unique ordered R3 crystal structure may play a role in slowing helium diffusion. Diffusion is anisotropic in all of the trigonal carbonates, and is typically slowest for diffusion along the c direction, and faster for diffusion normal to c and in directions normal to cleavage surfaces. The patterns of diffusional anisotropy are predicted to first order by the size of limiting inter-atomic apertures along any given crystallographic direction, providing additional support to the concept of modeling crystal lattices as "molecular sieves" with regard to diffusion of helium. When the effects of anisotropy and diffusion domain size are considered, our results are in reasonable agreement with previous results from bulk degassing of natural samples. Modeling of helium diffusive loss shows that calcite and magnesite are unlikely to be retentive of helium on the Earth's surface for typical grain sizes and time/temperature conditions. Dolomite and aragonite may be retentive under cooler conditions, but because helium retention is strongly dependent on diffusion domain size, general predictions are difficult given the structural complexities of natural samples. Our axis-specific diffusion measurements across a range of carbonate compositions, evaluated through direct profiling, offer important constraints for modeling helium mobility in carbonates, and for understanding the influence of the complexities of carbonate structures on He outgassing patterns.

  16. Molecular dynamics simulation of cascade-induced ballistic helium resolutioning from bubbles in iron

    International Nuclear Information System (INIS)

    Molecular dynamics simulations have been used to assess the ability of atomic displacement cascades to eject helium from small bubbles in iron. This study of the ballistic resolutioning mechanism employed a recently-developed Fe–He interatomic potential in concert with an iron potential developed by Ackland and co-workers. The primary variables examined were: irradiation temperature (100 and 600 K), cascade energy (5 and 20 keV), bubble radius (0.5 and 1.0 nm), and He-to-vacancy ratio in the bubble (0.25, 0.5 and 1.0). Systematic trends were observed for each of these variables. For example, ballistic resolutioning leads to a greater number of helium atoms being displaced from larger bubbles and from bubbles that have a higher He/vacancy ratio (bubble pressure). He resolutioning was reduced at 600 K relative to 100 K, and for 20 keV cascades relative to 5 keV cascades. Overall, the results indicate a modest level of He removal by ballistic resolutioning. The results may be particularly relevant to fusion irradiation conditions which produces high levels of helium by transmutation. They can be used to provide initial guidance in selection of a “resolution parameter” that can be employed in kinetic models to predict the bubble size distribution that evolves under irradiation

  17. Positron momentum calculation of defects in ?-Fe and Fe-Cr containing hydrogen and helium

    International Nuclear Information System (INIS)

    Lattice defects that contain hydrogen and helium in Fe and Fe-Cr have been studied by positron model calculations using Density Functional Theory (DFT) in its Local Density Approximation (LDA) implementation. It was found that the value of positron lifetime for perfect Fe lattice is 101.6 ps. and for mono vacancy is 176.6 ps. which a close to the experimental values. The calculated values of Positron Life-Time (PLT) for Fe-2.5% wt Cr is 104.7 ps., for Fe-5% wt Cr is 127.6 ps., for Fe-8% wt Cr is 128.9 ps. and for Fe-9% Cr is 128.2 ps. A correlation between the positron lifetime and H and He atom concentration has been established. The model calculations for PLT and Coincidence-Doppler-Broadening (CDB) for Fe-Cr containing vacations in the presence of different numbers of hydrogen and helium atoms will be presented.

  18. (e,2e) triple differential cross section for ionization-excitation of helium

    International Nuclear Information System (INIS)

    Simultaneous ionization and excitation of helium by electron impact is considered in an improved second Born approximation. The wave function of the low energy ejected electron is obtained in the field of residual He+ ion in 2s-state. The calculation has been done for the process e- + He->e- + He+(2s)+e- in the coplanar asymmetric geometry with Hartree-Fock wave function of Byron and Joachain for the helium ground state and the results are compared with the absolute experimental data at ? 5.5keV incident energy. Our results are found to increase the ratio of the recoil peak to binary peak intensity by about 30% over the first Born results and thus to bring it closer to the experimental data. (author). 19 refs., 3 figs

  19. Analysis of Photoassociation in Ultracold Metastable Helium

    CERN Document Server

    Cocks, Daniel G

    2009-01-01

    Photoassociation of spin-polarized metastable helium to the three lowest rovibrational levels of the J=1, $0_u^+$ state asymptoting to 2$s {}^{3}$S$_{1}+2p {}^{3}$P$_{0}$ is studied using a second-order perturbative treatment of the line shifts valid for low laser intensities, and two variants of a non-perturbative close-coupled treatment, one based upon dressed states of the matter plus laser system, and the other on a modified radiative coupling which vanishes asymptotically, thus simulating experimental conditions. These non-perturbative treatments are valid for arbitrary laser intensities and yield the complete photoassociation resonance profile. Both variants give nearly identical results for the line shifts and widths of the resonances and show that their dependence upon laser intensity is very close to linear and quadratic respectively for the two lowest levels. The resonance profiles are superimposed upon a significant background loss, a feature for this metastable helium system not present in studies...

  20. Ionoluminescence in the helium ion microscope.

    Science.gov (United States)

    Boden, Stuart A; Franklin, Thomas M W; Scipioni, Larry; Bagnall, Darren M; Rutt, Harvey N

    2012-12-01

    Ionoluminescence (IL) is the emission of light from a material due to excitation by an ion beam. In this work, a helium ion microscope (HIM) has been used in conjunction with a luminescence detection system to characterize IL from materials in an analogous way to how cathodoluminescence (CL) is characterized in a scanning electron microscope (SEM). A survey of the helium ion beam induced IL characteristics, including images and spectra, of a variety of materials known to exhibit CL in an SEM is presented. Direct band-gap semiconductors that luminesce strongly in the SEM are found not do so in the HIM, possibly due to defect-related nonradiative pathways created by the ion beam. Other materials do, however, exhibit IL, including a cerium-doped garnet sample, quantum dots, and rare-earth doped LaPO4 nanocrystals. These emissions are a result of transitions between f electron states or transitions across size dependent band gaps. In all these samples, IL is found to decay with exposure to the beam, fitting well to double exponential functions. In an exploration of the potential of this technique for biological tagging applications, imaging with the IL emitted by rare-earth doped LaPO4 nanocrystals, simultaneously with secondary electron imaging, is demonstrated at a range of magnifications. PMID:23237545

  1. Modeling Two-Charge State Helium Plasmas

    Science.gov (United States)

    Emmert, Gilbert; Santarius, John

    2012-10-01

    A computational model for the flow of energetic helium ions and atoms through a background neutral helium gas is being developed. The essence of the method is to consider atomic reactions as creating a new source of ions or neutrals if the energy or charge state of the resulting particle is changed. A set of conservation equations in a two-dimensional (position -- energy) phase space is formulated. Atomic reactions that lead to ions being born with zero kinetic energy are modeled with a 1-D Volterra integral equation [1] that can quickly be solved numerically by finite differences. Atomic reactions leading to ions being born with finite kinetic energy are formulated as source terms in the position-energy phase space. The conservation equations are solved iteratively using the solution to the Volterra equation as a starting point. The current work focuses on multiple-pass, 1-D ion flow through neutral gas in a nearly transparent anode and cathode pair in planar, cylindrical, and spherical geometry for application to ^3He-^3He and D-^3He inertial electrostatic experiments.[4pt] [1] G.A. Emmert and J.F. Santarius, ``Atomic and Molecular Effects on Spherically Convergent Ion Flow I: Single Atomic Species,'' Phys. Plasmas 17, 013502 (2010)

  2. Thermal instabilities in an helium II channel

    International Nuclear Information System (INIS)

    Cooling of superconductors by helium II is proving to be a very useful technique which has been studied for a few years by several groups. The advantage of He II is the enhanced thermal stability of the conductor due to the superfluid properties and consequently the greater heat fluxes which can be transfered from the solid to the coolant. So far, most studies of the stationary and transient thermal properties of cooling channels have been performed in experimental configurations where the heat flux is uniform. In a previous paper, the different stationary heat flow regimes were described for a channel filled with saturated helium II and with a non-uniform heat flux due to the experimental configuration. It was shown that above a certain value of the heat flux Q0 the value of Q greatly increases with a very little increase in average temperature, and in this regime the temperature oscillates by a few mK. It appears that an additional heat transfer process is present in parallel with the classical Gorter-Mellink (G.M.) process. This paper is a more detailed experimental study of these temperature fluctuations and an interpretation is given in terms of local nucleation in the fluid

  3. The primordial helium abundance from updated emissivities

    International Nuclear Information System (INIS)

    Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Yp. The He I emissivities are the foundation of the model of the H II region's emission. Porter, Ferland, Storey, and Detisch (2012) have recently published updated He I emissivities based on improved photoionization cross-sections. We incorporate these new atomic data and update our recent Markov Chain Monte Carlo analysis of the dataset published by Izotov, Thuan, and Stasi'nska (2007). As before, cuts are made to promote quality and reliability, and only solutions which fit the data within 95% confidence level are used to determine the primordial He abundance. The previously qualifying dataset is almost entirely retained and with strong concordance between the physical parameters. Overall, an upward bias from the new emissivities leads to a decrease in Yp. In addition, we find a general trend to larger uncertainties in individual objects (due to changes in the emissivities) and an increased variance (due to additional objects included). From a regression to zero metallicity, we determine Yp = 0.2465 ± 0.0097, in good agreement with the BBN result, Yp = 0.2485 ± 0.0002, based on the Planck determination of the baryon density. In the future, a better understanding of why a large fraction of spectra are not well fit by the model will be crucial to achieving an increase in the precision of the primordial helium abundance determination

  4. Helium effects on tritium storage materials

    International Nuclear Information System (INIS)

    For ten years French Tritium laboratories have been using metal hydride storage beds with LaNi4Mn for process gas (HDT mixture) absorption, desorption and for both short and long term storage. This material has been chosen because of its low equilibrium pressure and of its ability to retain decay helium 3 in its lattice. Aging effects on the thermodynamic behavior of LaNi4Mn have been investigated. Aging, due to formation of helium 3 in the lattice, decreases the desorption isotherm plateau pressure and shifts the ? phase to the higher stoichiometries. Life time of the two kinds of tritium (and isotopes) storage vessels managed in the laboratory depends on these aging changes. The Tritium Long Term Storage (namely STLT) and the hydride storage vessel (namely FSH 400) are based on LaNi4Mn even though they are not used for the same applications. STLT contains LaNi4Mn in an aluminum vessel and is designed for long term pure tritium storage. The FSH 400 is composed of LaNi4Mn included within a stainless steel container. This design is aimed at storing low tritium content mixtures (less than 3% of tritium) and for supplying processes with HDT gas. Life time of the STLT can reach 12 years. Life time of the FSH 400 varies from 1.2 years to more than 25 years depending on the application. (authors)

  5. Neutrons on a surface of liquid helium

    CERN Document Server

    Grigoriev, P D; Ziman, T; Grigoriev, A D

    2015-01-01

    We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyse the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time constant of these UCNs at 0.7 K is found to exceed one hour, and rapidly increasing with decreasing temperature. Such low scattering rates should enable high-precision measurements of the scheme of discrete energy levels, thus providing improved access to short-range gravity. The system might also be useful for neutron beta-decay experiments. We also sketch new ex...

  6. Charged complexes at the surface of liquid helium

    OpenAIRE

    Dyugaev, A. M.; Grigoriev, P. D.; Wyder, P.

    2002-01-01

    Charged clusters in liquid helium in an external electric field form a two-dimensional system below the helium surface. This 2D system undergoes a phase transition from a liquid to a Wigner crystal at rather high temperatures. Contrary to the electron Wigner crystal, the Wigner lattice of charged clusters can be detected directly.

  7. Nuclear polarizability of helium isotopes in atomic transitions

    OpenAIRE

    Pachucki, K.; Moro, A. M.

    2006-01-01

    We estimate the nuclear polarizability correction to atomic transition frequencies in various helium isotopes. This effect is non-negligible for high precision tests of quantum electrodynamics or accurate determination of the nuclear charge radius from spectroscopic measurements in helium atoms and ions. In particular, it amounts to $28(3)$ kHz for 1S-2S transition in 4He+.

  8. Variability in the extreme helium star LSS 5121

    OpenAIRE

    Woolf, V. M.; Cuadrado, R. Aznar; G. Pandey; Jeffery, C. Simon

    2001-01-01

    We report a photometric and spectroscopic study of the hot extreme helium star LSS 5121. We found photometric variability, but no period was evident in its periodogram. This is consistent with the previous proposal, based on spectral line variations, that LSS 5121 is a non-radial pulsator similar to other hot extreme helium stars.

  9. Sound velocity in helium-filled porous Vycor glass

    Energy Technology Data Exchange (ETDEWEB)

    Beamish, J.R.; Hikata, A.; Elbaum, C.

    1983-05-01

    The velocity of longitudinal and transverse sound in helium-filled porous Vycor glass was measured and analyzed with the use of the Biot theory of sound propagation in fluid-filled porous media. From transverse wave velocities, the superfluid fraction was determined and, from longitudinal velocities, the elastic properties of the helium were determined.

  10. Design and tests of liquid helium rotating cryostat

    International Nuclear Information System (INIS)

    The design and performance testing results of an experimental apparatus, built to test the mechanical and cryogenic properties of a liquid helium rotating cryostat up to 3000 rpm, are reported. The key points studied were the behaviour of the insulation seals, the rotating seals, the thermal shield, the liquid helium supply and vapour recovery. Continuous information was obtained using a telemetry technique. (author)

  11. Study of a microwave discharge in argon/helium mixtures

    International Nuclear Information System (INIS)

    A discharge created by a surface wave in Argon-Helium mixture is studied. First, the helium influence on plasma parameters has been studied (electron density, electric field, effective collision frequency, etc...), then, on excitation processes in the discharge. Relations between plasma lines, electron density and electric field have been established

  12. Helium leak and chemical impurities control technology in HTTR

    International Nuclear Information System (INIS)

    Japan Atomic Energy Agency (JAEA) has designed and developed high-temperature gas-cooled reactor (HTGR) hydrogen cogeneration system named gas turbine high-temperature reactor (GTHTR300C) as a commercial HTGR. Helium gas is used as the primary coolant in HTGR. Helium gas is easy to leak, and the primary helium leakage should be controlled tightly from the viewpoint of preventing the release of radioactive materials to the environment. Moreover from the viewpoint of preventing the oxidization of graphite and metallic material, the helium coolant chemistry should be controlled tightly. The primary helium leakage and the helium coolant chemistry during the operation is the major factor in the HTGR for commercialization of HTGR system. This paper shows the design concept and the obtained operational experience on the primary helium leakage control and primary helium impurity control in the high-temperature engineering test reactor (HTTR) of JAEA. Moreover, the future plan to obtain operational experience of these controls for commercialization of HTGR system is shown. (author)

  13. Helium isotopes in ferromanganese crusts from the central Pacific Ocean

    Science.gov (United States)

    Basu, S.; Stuart, F.M.; Klemm, V.; Korschinek, G.; Knie, K.; Hein, J.R.

    2006-01-01

    Helium isotopes have been measured in samples of two ferromanganese crusts (VA13/2 and CD29-2) from the central Pacific Ocean. With the exception of the deepest part of crust CD29-2 the data can be explained by a mixture of implanted solar- and galactic cosmic ray-produced (GCR) He, in extraterrestrial grains, and radiogenic He in wind-borne continental dust grains. 4He concentrations are invariant and require retention of less than 12% of the in situ He produced since crust formation. Loss has occurred by recoil and diffusion. High 4He in CD29-2 samples older than 42 Ma are correlated with phosphatization and can be explained by retention of up to 12% of the in situ-produced 4He. 3He/4He of VA13/2 samples varies from 18.5 to 1852 Ra due almost entirely to variation in the extraterrestrial He contribution. The highest 3He/4He is comparable to the highest values measured in interplanetary dust particles (IDPs) and micrometeorites (MMs). Helium concentrations are orders of magnitude lower than in oceanic sediments reflecting the low trapping efficiency for in-falling terrestrial and extraterrestrial grains of Fe-Mn crusts. The extraterrestrial 3He concentration of the crusts rules out whole, undegassed 4–40 ?m diameter IDPs as the host. Instead it requires that the extraterrestrial He inventory is carried by numerous particles with significantly lower He concentrations, and occasional high concentration GCR-He-bearing particles.

  14. Tests of Macroscopic Wave Function Theories of Helium II

    Science.gov (United States)

    Moulthrop, Andrew Alfred

    Two experiments are presented. One is an attempt to observe the Josephson effect in superfluid helium using a toroidal volume of helium mounted on a high Q torsional oscillator. The other is a search for an external gauge field associated with the He II order parameter. The Josephson effect was searched for by looking for a dependence of the pendulum resonance frequency on pendulum amplitude. The Josephson junctions are formed by packing naturally porous powder (crushed Vycor glass and zeolites) into the torus. These substances have natural pores of the order of 10 angstroms in diameter, which is much smaller than the man-made orifices used in previous experiments. Smaller pores are better for maintaining the phase coherence necessary to the Josephson effect. We failed to detect the Josephson effect. Analysis shows that this result was probably due to the powder geometry employed. The powder particle pores may form Josephson junctions, but the bulk fluid paths around the particles short out any phase differences. Theorists often assume that He II obeys a set of equations formally identical to the Landau-Ginzberg equations of superconductivity, yet without any term corresponding to the electromagnetic vector potential. Proposals have, however, appeared in the literature that He II should have its own vector potential. Usually this potential is assumed to be confined to the fluid, but our second experiment tests for the possibility that it could extend outside the fluid into the vacuum. This experiment tests for a coupling between two disjoint He II persistent current rings caused by this vector potential. Specifically we tested to see if inducing a current in one ring would cause a current to flow in another, nearby ring. We saw no coupling, so we can set a limit on this proposed gauge field, that its dimensionless coupling constant must be less than 3 x 10('-5) times the coupling constant in electromagnetism.

  15. Creep properties of Hastelloy X in a carburizing helium environment

    International Nuclear Information System (INIS)

    In this work, we investigate the environmental effect on the creep behavior of Hastelloy X at 9000C in helium and air. Since helium coolant in HTGR is expected to be carburizing and very weakly oxidizing for most metals, testings were focused on the effect of carburizing and slight oxidation. Carburization decreases secondary creep strain rate and delays tertiary creep initiation. On the other hand, the crack growth rate on the specimen surface is enhanced due to very weak oxidation in helium, therefore the tertiary creep strain rate becomes larger than that in air. The rupture time of Hastelloy X was shorter in helium when compared with in air. Stress versus rupture time curves for both environments do not deviate with each other during up to 5000 hours test, and a ratio of rupture stress in helium to that in air was about 0.9

  16. Helium diffusion in olivine based on first principles calculations

    Science.gov (United States)

    Wang, Kai; Brodholt, John; Lu, Xiancai

    2015-05-01

    As a key trace element involved in mantle evolution, the transport properties of helium in the mantle are important for understanding the thermal and chemical evolution of the Earth. However, the mobility of helium in the mantle is still unclear due to the scarcity of measured diffusion data from minerals under mantle conditions. In this study, we used first principles calculations based on density functional theory to calculate the absolute diffusion coefficients of the helium in olivine. Using the climbing images nudged elastic band method, we defined the diffusion pathways, the activation energies (Ea), and the prefactors. Our results demonstrate that the diffusion of helium has moderate anisotropy. The directionally dependent diffusion of helium in olivine can be written in Arrhenius form as follows.

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

    Science.gov (United States)

    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.

  18. Evaluation of helium gas release behavior in FBR fuel

    International Nuclear Information System (INIS)

    Internal rod pressure of a FBR fuel pin is one of the important factors which restrict the lifetime of a fuel pin, because fission gases (krypton, xenon and helium) are released from fuel pellets to increase internal rod pressure with increasing burn-up. Due to their relatively higher fission yield, the release behavior of krypton and xenon have already been studied well. However, there are few studies on helium release behavior. It is supposed that substantial amount of helium gas is produced in high burn-up (?150 GWd/t) MOX fuels and the fuels containing minor actinides. Therefore we established the quantitative measurement method of helium gas released from FBR fuels, and the helium gas release behavior was evaluated. (J.P.N.)

  19. Pressurized helium II-cooled magnet test facility

    International Nuclear Information System (INIS)

    A facility for testing superconducting magnets in a pressurized bath of helium II has been constructed and operated. The cryostat accepts magnets up to 0.32 m diameter and 1.32 m length with current to 3000 A. In initial tests, the volume of helium II surrounding the superconducting magnet was 90 liters. Minimum temperature reached was 1.7 K at which point the pumping system was throttled to maintain steady temperature. Helium II reservoir temperatures were easily controlled as long as the temperature upstream of the JT valve remained above T lambda; at lower temperatures control became difficult. Positive control of the temperature difference between the liquid and cold sink by means of an internal heat source appears necessary to avoid this problem. The epoxy-sealed vessel closures, with which we have had considerable experience with normal helium vacuum, also worked well in the helium II/vacuum environment

  20. Cosmic Ray Helium Intensities over the Solar Cycle from ACE

    Science.gov (United States)

    DeNolfo, G. A.; Yanasak, N. E.; Binns, W. R.; Cohen, C. M. S.; Cummings, A. C.; Davis, A. J.; George, J. S.; Hink. P. L.; Israel, M. H.; Lave, K.; Leske, R. A.; Mewaldt, R. A.; Moskalenko, I. V.; Ogliore, R.; Stone, E. C.; Von Rosenvinge, T. T.; Wiedenback, M. E.

    2007-01-01

    Observations of cosmic-ray helium energy spectra provide important constraints on cosmic ray origin and propagation. However, helium intensities measured at Earth are affected by solar modulation, especially below several GeV/nucleon. Observations of helium intensities over a solar cycle are important for understanding how solar modulation affects galactic cosmic ray intensities and for separating the contributions of anomalous and galactic cosmic rays. The Cosmic Ray Isotope Spectrometer (CRIS) on ACE has been measuring cosmic ray isotopes, including helium, since 1997 with high statistical precision. We present helium elemental intensities between approx. 10 to approx. 100 MeV/nucleon from the Solar Isotope Spectrometer (SIS) and CRIS observations over a solar cycle and compare these results with the observations from other satellite and balloon-borne instruments, and with GCR transport and solar modulation models.

  1. Localized helium excitations in 4He_N-benzene clusters

    CERN Document Server

    Huang, P; Huang, Patrick

    2003-01-01

    We compute ground and excited state properties of small helium clusters 4He_N containing a single benzene impurity molecule. Ground-state structures and energies are obtained for N=1,2,3,14 from importance-sampled, rigid-body diffusion Monte Carlo (DMC). Excited state energies due to helium vibrational motion near the molecule surface are evaluated using the projection operator, imaginary time spectral evolution (POITSE) method. We find excitation energies of up to ~23 K above the ground state. These states all possess vibrational character of helium atoms in a highly anisotropic potential due to the aromatic molecule, and can be categorized in terms of localized and collective vibrational modes. These results appear to provide precursors for a transition from localized to collective helium excitations at molecular nanosubstrates of increasing size. We discuss the implications of these results for analysis of anomalous spectral features in recent spectroscopic studies of large aromatic molecules in helium clu...

  2. Double photoionization of helium with synchrotron x-rays: Proceedings

    International Nuclear Information System (INIS)

    This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database

  3. Double photoionization of helium with synchrotron x-rays: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    1994-01-01

    This report contains papers on the following topics: Overview and comparison of photoionization with charged particle impact; The ratio of double to single ionization of helium: the relationship of photon and bare charged particle impact ionization; Double photoionization of helium at high energies; Compton scattering of photons from electrons bound in light elements; Electron ionization and the Compton effect in double ionization of helium; Elimination of two atomic electrons by a single energy photon; Double photoionization of helium at intermediate energies; Double Photoionization: Gauge Dependence, Coulomb Explosion; Single and Double Ionization by high energy photon impact; The effect of Compton Scattering on the double to single ionization ratio in helium; and Double ionization of He by photoionization and Compton scattering. These papers have been cataloged separately for the database.

  4. Estimations of atomic nucleus ionization cross sections for hydrogen and helium atoms

    International Nuclear Information System (INIS)

    Approximation formulae for cross sections of hydrogen ionization and one- and two-multiple helium ionization by fast nuclei are obtained within the frames of the impact parameter method and approximation of independent electrons. Cross section of hydrogen ionization with C+6 nuclei at nuclei energies from 0.1 to 5.0 MeV/nucleon are calculated. In case of single-electron ionization the given approximation results in good agreement with the experiment

  5. A study of formation of iron nanoparticles in aluminium matrix with helium pores.

    Czech Academy of Sciences Publication Activity Database

    Kichanov, S.E.; Kozlenko, D. P.; Belushkin, A.V.; Reutov, V.F.; Samoilenko, S.O.; Jirák, Zden?k; Savenko, B. N.; Bulavin, L. A.; Zubavichus, Y.V.

    2012-01-01

    Ro?. 351, ?. 1 (2012), "012013-1"-"012013-5". ISSN 1742-6588. [International Workshop on SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor - Devoted to the 75th anniversary of Yu M Ostanevich's Birth /2./. Dubna, 27.05.2011-30.05.2011] Institutional research plan: CEZ:AV0Z10100521 Keywords : iron nanoparticles * aluminium matrix * helium pores Subject RIV: BM - Solid Matter Physics ; Magnetism

  6. Liquid-helium-cooled far-infrared grating spectrometer for a balloon-borne infrared telescope

    International Nuclear Information System (INIS)

    A liquid-helium-cooled far-infrared grating spectrometer has been developed for a 50-cm balloon-borne infrared telescope. The spectral coverage is from 50 to 110 microns, with the spectral resolution of 0.5 to 0.35 micron. The diaphragm aperture is 2 arc min in diameter when attached to the telescope. This spectrometer was used in two balloon observations made in March 1985 and in August 1986 in Australia. 8 references

  7. Using Uncertainty Principle to Find the Ground-State Energy of the Helium and a Helium-like Hookean Atom

    Science.gov (United States)

    Harbola, Varun

    2011-01-01

    In this paper, we accurately estimate the ground-state energy and the atomic radius of the helium atom and a helium-like Hookean atom by employing the uncertainty principle in conjunction with the variational approach. We show that with the use of the uncertainty principle, electrons are found to be spread over a radial region, giving an electron…

  8. Scaling of triple differential cross-sections for asymmetric $(e, 2e)$ process on helium isoelectronic ions by fast electrons

    Indian Academy of Sciences (India)

    M. K. Srivastava

    2005-01-01

    A simple scaling law is obtained for asymmetric $(e, 2e)$ process on helium isoelectronic ions by fast electrons. It is based on treating the targets as having one active electron moving in the effective Coulomb field of the atomic core with an effective charge $Z' = Z ? 5/8$. This effective charge is also used in the description of the scattered and ejected electrons. The model has been tested against other available $(e, 2e)$ results on helium in asymmetric geometry. The scaling law is found to work reasonably well for fast incident electrons and becomes increasingly accurate as target increases.

  9. Implications of the new globular-cluster metal-abundance scale for the helium abundance in the galactic halo

    International Nuclear Information System (INIS)

    Adopting the new abundance scale for globular clusters (Cohen; Pilachowski, Sneden, and Canterna), we point out a difficulty in fitting main sequences of 47 Tucanae and other well-studied globular clusters, like M3, M5, and M13. In order to circumvent this problem, a substantial difference in helium abundance must be invoked. Such differences can also cause the very faint turnoff mangitudes found recently by Alcaino and Liller for NGC 6397 and by Cannon for ? Centauri, without the need to assign excessive ages to these clusters. We discuss other consequences of this helium-abundance variation

  10. Performance of an efficient 6 kW helium refrigerator for the LEP 200 project at CERN

    International Nuclear Information System (INIS)

    CERN has installed helium refrigeration plants for the LEP 200 project in 1991 with an equivalent refrigeration capacity of 6 kW at 4.5 K. The cold boxes of the plants were specified to be installed in the LEP tunnel and were therefore limited regarding their physical size. The LINDE helium refrigeration plant combines an extremely compact construction with a remarkably good cycle efficiency. It was in part achieved by arranging 3 expansion turbines in the temperature region below 20 K, one of which expands to roughly saturated liquid. The paper describes the system, the results of performance measurements, and the experience obtained during more than one year of operation

  11. RBE of 650-MeV helium ions at different depths for chromosome aberrations in Allium cepa

    International Nuclear Information System (INIS)

    Induction of chromosome aberrations in Allium cepa onion roots has been used as biological criterion in order to determine the RBE of 650-MeV helium ions as a function of depth. These experiments were carried out at the synchrotron Saturne at Saclay (France). The Bragg peak of the helium ion beam was spread out, over a depth of about 5 cm, by means of a 'ridge filter'. RBE of the 650-MeV helium ions was determined at the beginning (13 cm in depth), middle (15 cm) and end (17 cm) of the spread-out Bragg peak using as reference radiation quality the initial plateau (2 cm in depth). (orig./MG)

  12. Two-photon laser spectroscopy of antiprotonic helium atoms, and the antiproton-to-electron mass ratio

    International Nuclear Information System (INIS)

    Some two-photon transitions in antiprotonic helium atoms at the deep UV wavelengths ? = 139.8–197.0 nm were recently studied by laser spectroscopy. The thermal Doppler broadening of the observed antiprotonic resonances were reduced by exciting the atoms with two counterpropagating laser beams of wavelengths ? = 265–417 nm. The resulting narrow spectral lines allowed the measurement of three transition frequencies in antiprotonic helium-3 and helium-4 isotopes with fractional precisions of 2.3–5 parts in 109. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). We briefly review these experimental results that were presented in Ref. [1

  13. Implementation of heavy-ion elastic recoil detection analysis at JANNUS-Saclay for quantitative helium depth profiling

    Science.gov (United States)

    Loussouarn, T.; Beck, L.; Trocellier, P.; Brimbal, D.; Leprêtre, F.; Bordas, E.; Vaubaillon, S.; Serruys, Y.; Lefaix-Jeuland, H.

    2015-10-01

    Quantitative depth profiling measurements of implanted light elements is an important issue for electronics and nuclear applications. Conventional elastic recoil detection analysis (ERDA) has been improved by using heavy ions as incident particles for quantitatively profiling helium in materials. A new system has been implemented on the triple beam irradiation platform JANNUS at Saclay devoted to carry out HI-ERDA measurements. This device is dedicated to helium depth profiling using a 15 MeV 16O5+ incident ion beam. Capabilities of the technique (quantitative analysis, resolution and limit of detection) were tested on samples of known composition. For the first time, 4He depth profiles in pure ?-iron, as-implanted and annealed, are obtained. HI-ERDA measurements have shown that helium release in pure ?-iron can be described by a succession of two steps, the first having a slow kinetics below 700 °C and the second with a fast kinetics above 700 °C.

  14. Helium processing for deuterium/helium burns in ITER's physics phase

    International Nuclear Information System (INIS)

    The requirements for vacuum pumping and fuel processing for deuterium/helium (D/3He) burns in the physics operating phase for the International Thermonuclear Experimental Reactor (ITER) were assessed. These burns are expected to have low fusion power (100 MW), short burn times (?30 s), limited operation (2000 shots), and a fractional burn ?0.3%. For the physics phase, the fuel processing system will include several units to separate deuterium and helium (activated charcoal bed, SAES getter and a Pd/Ag diffuser), as well as an isotopic separation system to separate 3He and 4He. The needed vacuum system's cryosorption surface area may be as large as 10 m2 if the burn time is ?200 s, the fractional burn is 100 MW. 8 refs., 1 fig., 4 tabs

  15. Antiproton–to–electron mass ratio determined by two-photon laser spectroscopy of antiprotonic helium atoms

    Directory of Open Access Journals (Sweden)

    Sótér A.

    2014-03-01

    Full Text Available The ASACUSA collaboration of CERN has recently carried out two-photon laser spectroscopy of antiprotonic helium atoms. Three transition frequencies were determined with fractional precisions of 2.3–5 parts in 109. By comparing the results with three-body QED calculations, the antiproton-to-electron mass ratio was determined as 1836.1526736(23.

  16. Heat transfer in cryogenic helium gas by turbulent Rayleigh-Bénard convection in a cylindrical cell of aspect ratio 1.

    Czech Academy of Sciences Publication Activity Database

    Urban, Pavel; Hanzelka, Pavel; Musilová, V?ra; Králík, Tomáš; La Mantia, M.; Srnka, Aleš; Skrbek, L.

    2014-01-01

    Ro?. 16, ?. 5 (2014), 053042: 1-40. ISSN 1367-2630 R&D Projects: GA ?R GPP203/12/P897 Institutional support: RVO:68081731 Keywords : Rayleigh-Bénard convection * heat transfer efficiency * cryogenic helium Subject RIV: BK - Fluid Dynamics Impact factor: 3.558, year: 2014

  17. A turbo-alternator expander in supercritical helium for the liquefaction of helium

    International Nuclear Information System (INIS)

    The author describes in the present note the construction and the first results of a turbo-alternator completely immersed in supercritical helium and used as expander in replacement of the Joule-Thomson screen on a refrigerator of nominal 400 W at 4.4 K. The obtained isentropic yield is 37% while the net gain on the performances of the refrigerator reaches 23%. (HSI)

  18. Helium-3/helium-4 ratios in soil gas as an indicator of tritium contamination near the 618-11 burial ground, Hanford site, Washington

    International Nuclear Information System (INIS)

    Pacific Northwest National Laboratory sampled and analyzed soil gas for helium-3 and helium-4 concentrations from the vicinity of the 618-11 burial ground. Helium-3, the first daughter product from tritium decay, was used to investigate the source and extent of tritium contamination in the area. Seventy soil-gas sampling points were installed around the perimeter of the 618-11 burial ground, approximately 122 meters downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 946 meters. Soil-gas samples were collected, analyzed for helium isotopes, and helium-3/helium-4 ratios were calculated from these 70 points. Helium-3/helium-4 ratios determined from the sampling points showed significant enrichments compared to ambient air helium-3/helium-4 ratios. The highest helium-3/helium-4 ratios were located along the north perimeter of the burial ground. Helium-3/ helium-4 ratios (normalized to their abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transects downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground. This vadose zone source is likely the source of tritium in the groundwater. The helium-3/helium-4 ratios also suggest the groundwater plume is traveling eastnortheast from the burial ground, and the highest groundwater tritium value may be to the north of well 699-13-3A. Finally, there appears to be no significant upgradient sources of tritium affecting the burial ground since all the upgradient helium-3/helium-4 ratios equal the air background level of 1.0. Based on the helium-3/helium-4 results from the soil-gas survey, six downgradient sampling locations were identified to verify the tritium groundwater plume locations and tritium groundwater concentrations. The results of the measurement of helium isotopes in soil gas provided a rapid and cost-effective technique to define the shape and extent of tritium contamination from the 618-11 burial ground

  19. High Voltage Test Apparatus for a Neutron EDM Experiment and Lower Limit on the Dielectric Strength of Liquid Helium at Large Volumes

    CERN Document Server

    Long, J C; Boissevain, J G; Clark, D J; Cooper, M D; Gómez, J J; Lamoreaux, S K; Mischke, R E; Penttila, S I

    2006-01-01

    A new search for a permanent electric dipole moment (EDM) of the neutron is underway using ultracold neutrons produced and held in a bath of superfluid helium. Attaining the target sensitivity requires maintaining an electric field of several tens of kilovolts per centimeter across the experimental cell, which is nominally 7.5 cm wide and will contain about 4 liters of superfluid. The electrical properties of liquid helium are expected to be sufficient to meet the design goals, but little is known about these properties for volumes and electrode spacings appropriate to the EDM experiment. Furthermore, direct application of the necessary voltages from an external source to the experimental test cell is impractical. An apparatus to amplify voltages in the liquid helium environment and to test the electrical properties of the liquid for large volumes and electrode spacings has been constructed. The device consists of a large-area parallel plate capacitor immersed in a 200 liter liquid helium dewar. Preliminary r...

  20. 15 years experience with helium ion radiotherapy for uveal melanoma

    International Nuclear Information System (INIS)

    Purpose/Objective: In this study we review our long term experience with helium ion therapy in treating uveal melanoma. Materials and Methods: At UCSF-LBL, 347 patients with uveal melanoma were treated with helium ions from December 1978 - May 1992. A non randomized dose searching study was undertaken beginning with 80 GyE in 5 fractions and subsequently lowered through several levels to 48 GyE in 4 fractions. The treatment period ranged from 3 to 15 days, with a mean of 7 days. The various dose groups were similar in tumor characteristics and size. Results: An overall local control rate of 96% has been achieved, with no dose response being seen at 80, 70, 60 or 50 GyE in 5 fxs. At the lowest dose level of 48 GyE in 4 fxs, the local control rate fell to 87%. Fifteen patients (4%) had local failure in the eye requiring enucleation (12 pts), laser (1 pt) or reirradiation (2 pts). The time of appearance of local failures ranges from 4 to 64 months with most occurring within 2 years. Eight of the 15 patients with local failure are dead of distant metastases. Of the 347 patients, 308 had (20(200)) vision or better in the affected eye prior to treatment. Of these, 125 (41%) have retained at least(20(200)) vision in the treated eye. Patients with tumors greater than 5 mm in ultrasound height or close to the optic nerve or fovea have a reduced chance of retaining useful vision. The total enucleation rate is 15%, 1% for local failure and 14% because of complications of the helium RT, mostly secondary to severe glaucoma. Of the 347 patients, 230 are still alive. The median follow up is 75 months, range 3-206 months. Kaplan-Maier (K-M) survival for all 347 patients was 80% at 5 years, 77% at 10 years and 68% at 15 years post treatment. Results for patients whose tumor involves the ciliary body is much worse with a 15 year K-M survival of 42%, whereas patients not having ciliary involvement have a 15 year K-M survival of 75%. The K-M survival in patients with local failure in the eye is 37% at 10 years. Conclusions: Local control and retention of the eye is excellent. Complications of therapy reduce vision and eye preservation. 23% of patients eventually manifested distant metastases, within 6 to 145 months, mean of 42 months, median of 36 months. The etiology for the late appearance of distant metastases is unknown but does not appear to be caused by late local recurrences. The risk is highest for patients with tumors greater then 6 mm in ultrasound height (33%), anterior tumors involving the ciliary body (47%) and those with local failure (53%). Adjuvant therapy is needed for patients at high risk for metastases

  1. Helium and Sulfur Hexafluoride in Musical Instruments

    Science.gov (United States)

    Forinash, Kyle; Dixon, Cory L.

    2014-11-01

    The effects of inhaled helium on the human voice were investigated in a recent article in The Physics Teacher.1 As mentioned in that article, demonstrations of the effect are a popular classroom activity. If the number of YouTube videos is any indication, the effects of sulfur hexafluoride on the human voice are equally popular. However, there appears to be little information available on the effects of either of these gases on musical instruments.2 We describe here the results of a student project that involved measuring the frequency shifts in an organ pipe, a trumpet, and a trombone as the result of filling the instruments with these two gases. The project was one of several possible end-of-semester projects required in an elective science of sound course for non-science majors.

  2. The liquid helium system of ATLAS

    International Nuclear Information System (INIS)

    Starting in 1978 with one small refrigerator and distribution line, the LHe system of ATLAS has gradually grown into a complex network, as required by several enlargements of the superconducting linac. The cryogenic system now comprises 3 refrigerators, 11 helium compressors, /approximately/340 ft. of coaxial LHe transfer line, 3 1000-l dewars, and /approximately/76 LHe valves that deliver steady-state flowing LHe to 16 beam-line cryostats. In normal operation, the 3 refrigerators are linked so as to provide cooling where needed. LHe heat exchangers in distribution lines play an important role. This paper discusses design features of the system, including the logic of the controls that permit the coupled refrigerators to operate stably in the presence of large and sudden changes in heat load. 8 refs., 3 figs

  3. Frequency metrology in quantum degenerate helium

    Directory of Open Access Journals (Sweden)

    Vassen Wim

    2013-08-01

    Full Text Available We have measured the absolute frequency of the 1557-nm doubly forbidden transition between the two metastable states of helium, 2?3S1 (lifetime 8000?s and 2?1S0 (lifetime 20?ms, with 1?kHz precision. With an Einstein coefficient of 10?7?s?1 this is one of weakest optical transitions ever measured. The measurement was performed in a Bose-Einstein condensate of 4He* as well as in a Degenerate Fermi Gas of 3He*, trapped in a crossed dipole trap. From the isotope shift we deduced the nuclear charge radius difference between the ?-particle and the helion. Our value differs by 4? with a very recent result obtained on the 2?3S ? 2?3P transition.

  4. Maximum practical efficiency of helium temperature refrigerators

    International Nuclear Information System (INIS)

    An ideal refrigerator using a perfect gas working fluid is defined which gives the efficiency of a refrigerator as a function of compressor and expander efficiency, heat exchanger temperature difference, and heat exchanger pressure drop. Although not suited to detailed hardware design, this approach clearly relates the overall cycle efficiency to component efficiencies. In contrast, computer studies of specific cycles using real fluid properties are usually such that the details tend to overshadow major trends. The results of the study show that in an efficient cycle the major losses are in the compressor and the cold end expansion device. For current compressor and expander efficiencies the maximum practical helium temperature refrigerator efficiency is about 37% of Carnot. (author)

  5. The gas turbine-modular helium reactor

    International Nuclear Information System (INIS)

    Full text: The Gas Turbine-Modular Helium Reactor (GT-MHR) is an advanced gas-cooled reactor currently under development in a joint United States-Russian Federation program to provide capacity for disposition of surplus weapons plutonium. A uranium-fueled option for commercial deployment is also being scheduled, which would apply the R and D performed in Russia. The GT-MHR module couples a gas-cooled modular helium reactor (MHR) with a high efficiency modular Brayton cycle gas turbine (GT) energy conversion system. The reactor and power conversion systems are located in a below grade concrete silo that provides protection against sabotage. The GT-MHR is designed to provide unparalleled safety, high thermal efficiency and environmental advantages at a competitive electricity generation cost. The overall level of safety is achieved through a combination of inherent safety characteristics and design selections consisting of: helium coolant, which is single phase, inert, and has no reactivity effects; graphite core, which provides high heat capacity and slow thermal response, and structural stability at very high temperatures; refractory coated particle fuel, which allows extremely high burnup and retains fission products at temperatures much higher than normal operation; negative temperature coefficient of reactivity, which inherently shuts down the core above normal operating temperatures; and an annular, 600 MWt low power density core in an uninsulated steel reactor vessel surrounded by a reactor cavity cooling system. Use of the Brayton cycle helium gas turbine in the GT-MHR provides electric generating capacity at a net plant efficiency of about 48%, a level that can be obtained by no other nuclear reactor technology. Relative to water reactor plants, the high plant efficiency reduces power generation costs, thermal discharge to the environment is reduced by 50%, and actinide production is reduced by about 60% per unit electricity produced. The MHR refractory coated particle fuel, identified as TRISO coated particle fuel, consists of a spherical kernel of fissile or fertile material, as appropriate for the application, encapsulated in multiple coating layers. The multiple coating layers form a miniature, highly corrosion resistant pressure vessel and an essentially impermeable barrier to the release of gaseous and metallic fission products. The overall diameter of standard TRISO-coated particles varies from about 650 microns to about 850 microns. TRISO coated particles are mixed with a carbonaceous matrix and formed into cylindrical fuel compacts, approximately 13 mm in diameter and 51 mm long. The fuel compacts are loaded into fuel channels in hexagonal graphite fuel elements, 793 mm long by 360 mm across flats. One hundred and two columns of the hexagonal fuel elements are stacked 10 elements high to form an annular core. The GT-MHR has two active, diverse heat removal systems, the power conversion system and a shutdown cooling system that can be used for the removal of decay heat. In the event that neither of these active systems is available, an independent passive means is provided for the removal of core decay heat. This is the reactor cavity cooling system (RCCS) surrounding the reactor vessel. Even if the RCCS is assumed to fail, passive heat conduction from the core, thermal radiation from the vessel, and conduction into the silo walls and surrounding earth is sufficient to maintain peak core temperatures to below the design limit. The refractory coatings of spent fuel provide both its long-term interim storage and permanent geologic disposal, and retain their integrity for hundreds of thousands of years. The GT-MHR spent fuel has very high proliferation resistance because the quantity of fissile material (plutonium and uranium) per spent fuel element is low, the plutonium isotopic composition is unattractive and there is neither a developed process nor capability anywhere in the world for separating the residual fissionable material from GT-MHR spent fuel. A comparison of the GT-MHR nth-of-a-kind plant leveliz

  6. Generic evolution of deuterium and helium-3

    CERN Document Server

    Steigman, G; Steigman, Gary; Tosi, Monica

    1995-01-01

    The primordial abundances of deuterium and of helium-3, produced during big bang nucleosynthesis, depend sensitively on the baryon density. Thus, the observed abundances of D and \\he may provide useful ``baryometers'' provided the evolution from primordial to present (or, presolar nebula) abundances is understood. Inevitably, the derivation of primordial from observed abundances requires the intervention of a model for galactic evolution and, so, the inferred primordial abundances are, necessarily, model dependent. Here, an analytic framework for the evolution of D and \\he is presented which is ``generic'' in the sense that it should describe the results of any specific galactic evolution model. The ``effective \\he survival fraction'', \\Gamma _3, is the one free parameter which is model specific. Solar system and interstellar data are used to infer upper and lower bounds to the primordial deuterium mass fraction (X_{2P}) as a function of \\Gamma _3 and, these bounds are used to constrain the present baryon-to-...

  7. Correlation holes for the helium dimer.

    Science.gov (United States)

    Piris, M; Lopez, X; Ugalde, J M

    2008-04-01

    We have investigated the radial electron pair probability distributions (REPPDs) of the helium dimer within the Piris natural orbital functional (PNOF) theory. The analytical formulas to evaluate intracule densities, Fermi, Coulomb, and total correlation holes using our reconstruction functional PNOF-2 [J. Chem. Phys. 126, 214103 (2007)] are derived. The Löwdin's Coulomb holes from PNOF-2 and full configuration interaction calculations are analyzed showing a very similar behavior. New definitions of the Coulomb and Fermi holes based on the cumulant expansion of the two-particle reduced density matrix are presented. The holes are defined in terms of the exact one-particle reduced density matrix and the two-particle cumulant without any reference to the Hartree-Fock state. Through these definitions, we analyze separately the contribution of each component to the total REPPD at several values of the internuclear distance. A straight connection between the Coulomb hole and dispersion interactions is observed. PMID:18397048

  8. Harmonic oscillator model for the helium atom

    CERN Document Server

    Carlsen, Martin

    2015-01-01

    A harmonic oscillator model in four dimensions is presented for the helium atom to estimate the distance to the inner and outer electron from the nucleus, the angle between electrons and the energy levels. The method is algebraic and is not based on the choice of correct trial wave function. Three harmonic oscillators and thus three quantum numbers are sufficient to describe the two-electron system. We derive a simple formula for the energy in the general case and in the special case of the Wannier Ridge. For a set of quantum numbers the distance to the electrons and the angle between the electrons are uniquely determined as the intersection between three surfaces. We show that the excited states converge either towards ionization thresholds or towards extreme parallel or antiparallel states and provide an estimate of the ground state energy.

  9. Photoionization of helium dimers; Photoionisation von Heliumdimeren

    Energy Technology Data Exchange (ETDEWEB)

    Havermeier, Tilo

    2010-06-09

    The helium dimer is one of the most weakly bound systems in the universe. This makes it an interesting quantum mechanical object for investigation. These Van der Waals Clusters can be produced in an expansion of a cryogenic gas jet through a small nozzle into vacuum. In the present experiment we examine the interaction of He dimers with synchrotron radiation at an energy range from 64 to 78 eV. We observed different pathways leading to single ionization of both He atoms of the dimer compound. This two close standing ions begin now to dissociate in cause of their coulomb potential. All charged fragments were detected in coincidence with a COLTRIMS system. Especially Interatomic Coulombic Decay (ICD) and the two step process (TS1) were clearly identified. Furthermore a distribution of the internuclear distance was obtained from the measured Kinetic Energy Release (KER). (orig.)

  10. Photoionizaton of Pure and Doped Helium Nanodroplets

    CERN Document Server

    Mudrich, M

    2014-01-01

    Helium nanodroplets, commonly regarded as the "nearly ideal spectroscopic matrix", are being actively studied for more than two decades now. While they mostly serve as cold, weakly perturbing and transparent medium for high-resolution spectroscopy of embedded molecules, their intrinsic quantum properties such as microscopic superfluidity still are subject-matter of current research. This article reviews recent work on pure and doped He nanodroplets using PI spectroscopy, an approach which has greatly advanced in the past years. While the notion of the ideal spectroscopic matrix mostly no longer holds in this context, photoionization techniques provide detailed insights into the photo-physical properties of pure and doped He nanodroplets and their relaxation dynamics following electronic excitation. Exploiting nowadays available high laser fields, even highly ionized states of matter on the nanoscale can be formed. Our particular focus lies on recent experimental progress including fs time-resolved spectroscop...

  11. An Update of the Primordial Helium Abundance

    Science.gov (United States)

    Peimbert, Antonio; Peimbert, Manuel; Luridiana, Valentina

    2015-08-01

    Three of the best determinations of the primordial helium abundance (Yp) are those obtained from low metallicity HII regions by Aver, Olive, Porter, & Skillman (2013); Izotov, Thuan, & Guseva (2014); and Peimbert, Peimbert, & Luridiana (2007). In this poster we update the Yp determination by Peimbert et al. taking into account, among other aspects, recent advances in the determination of the He atomic physical parameters, the temperature structure, the collisional effects of high temperatures on the Balmer lines, as well as the effect of H and He bound-bound absorption.We compare our results with those of Aver et al. and Izotov et al. and point out possible explanations for the differences among the three determinations. We also compare our results with those obtained with the Plank satellite considering recent measurements of the neutron mean life; this comparison has implications on the determination of the number of light neutrino families.

  12. Helium Loop Cooling Channel Hydraulic Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Olivas, Eric Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Morgan, Robert Vaughn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Woloshun, Keith Albert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-07-02

    New methods for generating ??Mo are being explored in an effort to eliminate proliferation issues and provide a domestic supply of ??mTc for medical imaging. Electron accelerating technology is used by sending an electron beam through a series of ¹??Mo 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.

  13. Observation of the antimatter helium-4 nucleus.

    Science.gov (United States)

    2011-05-19

    High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang; in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus (4He), also known as the anti-? (?), consists of two antiprotons and two antineutrons (baryon number B = -4). It has not been observed previously, although the ?-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level. Antimatter nuclei with B?antimatter nuclei and a benchmark for possible future observations of 4He in cosmic radiation. PMID:21516103

  14. Positronium and Electron Scattering on Helium

    Science.gov (United States)

    DiRienzi, Joseph

    2011-01-01

    A recent work [1] establishes experimentally that Positronium scattering by atoms of various elements is surprisingly close in total cross-section to that of an isolated electron of the same velocity. In this work we will look at the scattering of Ps on Helium and compare it to a determination of the scattering of an e- with the same element. For both the Ps scattering and the e- scattering on He, we assume the symmetrization of the e- with the closed shell He electrons is the dominant interaction. A local effective potential employed in [2] and [3] is used to model the electron exchange and cross- sections are determined for a set of partial waves. For the Ps scattering we include as a secondary effect the Van der Waals interaction. For single e- scattering of He, we also employ a short range Coulomb potential and dispersion as contributing effects. Results of the cross-sections determined in each case are then compared

  15. GCFR main helium circulator and electric drive

    International Nuclear Information System (INIS)

    One of the major objectives of the helium circulators for the gas-cooled fast breeder reactor (GCFR) is to achieve the highest possible operational reliability. This is no simple task considering the plant system integration requirements, auxiliary support systems, all possible transient requirements, and resulting complexity in supplying the driving power, primary coolant flow control, and lubrication and sealing. Therefore, the design of the circulator itself is highly dependent on the type of prime mover selected to drive the circulator, e.g., series turbine, parallel turbine, or electric motor. The circulator main drive has evolved from the series steam turbine drive into the variable-speed, synchronous electric motor drive mounted externally to the reactor and controlled by thyristor variable frequency controller. This design is a result of 18 months of joint effort by General Atomic Company and Westinghouse Electric Corporation

  16. Transport of Aluminum impurities in Helium Plasma

    Science.gov (United States)

    Hajjar, Rima; Hollmann, Eric; Krasheninnikov, Sergei; Doerner, Russell

    2013-10-01

    Impurity radiation losses at the edge of fusion devices are crucial for establishing detached divertor regimes in ITER and future tokamak reactors, despite the problem they cause in reducing plasma efficiency. Complex parallel and cross-field impurity transport suggest a rather fluid description when treating edge dynamics, leading somehow to marginal simulation results of the impurity transport problem. A kinetic description accounting for impurity/plasma collisions should be used instead, generating more details on the collision dynamics, while the relatively high mass difference between colliding particles leads to major simplifications in the physics of the problem. Modeling of Aluminum injection and entrainment into steady-state Helium plasma is presented. Multiple ionization and radial losses are included and numerical results are then compared to experimental data obtained from PISCES machine. Impurity radiation losses at the edge of fusion devices are crucial for establishing detached divertor regimes in ITER and future tokamak reactors, despite the problem they cause in reducing plasma efficiency. Complex parallel and cross-field impurity transport suggest a rather fluid description when treating edge dynamics, leading somehow to marginal simulation results of the impurity transport problem. A kinetic description accounting for impurity/plasma collisions should be used instead, generating more details on the collision dynamics, while the relatively high mass difference between colliding particles leads to major simplifications in the physics of the problem. Modeling of Aluminum injection and entrainment into steady-state Helium plasma is presented. Multiple ionization and radial losses are included and numerical results are then compared to experimental data obtained from PISCES machine. Work was supported in part by the DOE Grant DE-FG02-04ER54739 at UCSD.

  17. Liquid Oxygen Thermodynamic Vent System Testing with Helium Pressurization

    Science.gov (United States)

    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 ullage, and combined use of the axial jet and spray hoops. A submerged liquid pump and compact heat exchanger located inside the test tank were used with all the mixer configurations. The initial series without helium and the final series with liquid nitrogen both used the axial jet mixer. The axial jet configuration successfully demonstrated the ability to control tank pressure; but in the normal-gravity environment, the temperature in the upper tank region (ullage and unwetted wall) was not controlled. The spray hoops and axial jet combination also successfully demonstrated pressure control as well as temperature control of the entire tank and contents. The spray-hoops-only configuration was not expected to be a reliable means of tank mixing because there was no direct means to produce liquid circulation. However, surprisingly good results also were obtained with the sprayhoops- only configuration (i.e., performance metrics such as cycle-averaged vent flowrate were similar to those obtained with the other configurations). A simple thermodynamic model was developed that correctly predicted the TVS behavior (temperature rise or pressure drop per TVS cycle) when helium was present in the ullage. The model predictions were correlated over a range of input parameters. The correlations show that temperature rise or pressure drop per cycle was proportional to both helium mole fraction and tank heat input. The response also depended on the tank fill fraction: the temperature rise or pressure drop (per TVS cycle) increased as the ullage volume decreased.

  18. Creep rupture properties of helium implanted ?'' precipitation strengthened alloy

    International Nuclear Information System (INIS)

    Creep rupture tests were carried out on a ?''-Ni3Nb precipitation strengthened alloy (Alloy 7818) after helium implantation (10 at. ppm) at high temperatures in order to clarify the effect of helium on mechanical properties and results were compared to those of SUS 316 stainless steel, a core component material of a presently operating fast breeder reactor. Significant degradation of creep rupture strength and elongation by helium occurred in both alloys. However, suppression of degradation was discerned in long-term tests on Alloy 7818 while the variation of the degradation with time to rupture in SUS 316 followed a usual manner, i.e. increasing with increasing rupture time. SEM fractography showed that helium extensively introduced intergranular brittle failure on the ruptured surfaces of both alloys. The microstructure examination by TEM revealed that in the case of Alloy 7818 the Laves phase in the matrix, which became predominant after long time creep as a result of transformation from ?'', acted as a trapping site of helium. This observation implies that the abundant attendance of this phase may reduce the flux of helium from grain interiors to grain boundaries and consequently may cause suppression of mechanical property degradation by helium observed in this alloy. (author)

  19. Development and performance evaluation of external helium purifier

    International Nuclear Information System (INIS)

    Helium purification system is vital for removing gaseous and oil aerosol/oil vapour impurities in helium which can freeze and damage ultra high-speed turbo-expanders and choke fine passages of cryogenic heat exchangers or fine filters of helium refrigerators/ liquefiers. An external helium purifier is designed and fabricated for purification of 10 Nm3/hr flow of impure helium with maximum N2 impurity of 1%. It consists of an evacuated super-insulated cold box, a helical coil heat exchanger with tube in tube type configuration, an LN2 bath and a charcoal adsorber maintained at LN2 temperatures. The main features of the purifier are its compactness, low LN2 consumption, ease and simplicity of charcoal regeneration. Performance evaluation of the purifier is carried out by observing the impurities (N2 moisture and hydrocarbons) in the purified helium gas at its exit. Total LN2 consumption and effectiveness of heat exchanger used for recovery of cold of outgoing helium are also evaluated. (author)

  20. Helium isotopes, tectonics and heat flow in the Northern Caucasus

    Science.gov (United States)

    Polyak, B. G.; Tolstikhin, I. N.; Kamensky, I. L.; Yakovlev, L. E.; Cheshko, A. L.; Marty, B.

    2000-06-01

    109 new measurements of 3He/ 4He ? R in subsurface fluids of the Northern Caucasus coupled with the data obtained previously allow regional regularities in the distribution of helium isotopic composition to be examined. Cis-Caucasian foredeeps show the lowest radiogenic R-values. The average Rav-value is slightly higher in gases of the Scythian plate beyond the Stavropol arch. Within the arch, elevated R = (1.6-4.5) × 10 -7 indicates an input of mantle-derived helium. This input is even more evident to the south of Starvropol arch, in the Caucasian Mineral Water area, where the ?8 Ma old laccolithes occur and R-values approach (5-11) × 10 -7. The highest R-values, up to (0.7-0.9) × 10 -5, are observed further to the south, in the central segment of the Greater Caucasus, where recent volcanism is manifested. Enhanced R-values do not correlate with the crustal thickness but reflect degassing of magmatic reservoirs including those yet unknown. According to the recent Sr-Nd-O data, the young volcanic rocks are of mantle affinity but they are contaminated by a crustal component. The average Rav-values in fluids and 87Sr/ 86Sr ratios in host magmatic rocks show an inverse correlation suggesting mixing of crustal and mantle materials. R-values vary inversely with apatite fission-track ages of crystalline basement rocks. The ages increase westward of the Elbrus volcano, most likely recording the thermal degradation of the Greater Caucasus since the pre-Cainozoic magmatic activity. A direct correlation between Rav-values and background conductive heat flow densities implies that discharge of the mantle melts into the crust is the common cause of the geochemical, geochronological and geothermal regularities observed. Elevated R-values are generally observed in CO 2-bearing fluids, low values are typical of CH 4 gases, a few N 2-rich gases display highly variable R. Relationships between the major gas constituents and noble gas isotopes are discussed. Fractionation, loss, and gain of these species are considered as the processes controlling the compositions of underground fluids.