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Sample records for Helium 5

  1. Acquisition system for the liquid helium L5 plant

    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. Helium pumping by argon frosting on a 4.5 K surface

    Pumping of helium gas by means of argon frosting on a bare copper surface cooled to ∼4.5 K has been investigated in one of the neutral beamlines of the DIII-D tokamak. The beamline is designed to handle high power hydrogen and deuterium beams and corresponding high gas feed rates. By prefrosting the cryo panels with argon in an actual beamline, multi-second helium gas pulses have been handled at a background gas pressure low enough for formation and transport of helium beams. Appreciable pumping of helium gas was observed even at an argon-to-helium ratio as low as 20. 16 refs., 5 figs

  3. Helium pumping by argon frosting on a 4.5 K surface

    Pumping of helium gas by means of argon frosting on a bare copper surface cooled to ∼4.5 K has been investigated in one of the neutral beamlines of the DIII-D tokamak. The beamline is designed to handle high power hydrogen and deuterium beams and corresponding high gas feed rates. By prefrosting the cryo panels with argon in an actual beamline, multisecond helium gas pulses have been handled at a background gas pressure low enough for formation and transport of helium beams. Appreciable pumping of helium gas was observed even at an argon-to-helium ratio as low as 20

  4. Helium streamer chamber with laser track registration at gas pressure up to 5 atm

    The main purpose of the paper is the investigation of optimum operation conditions of the helium streamer chamber (HSC) with laser track registration at increased pressure. The emphasis is placed on the problem of high quality of tracks with an introduction of minimum amount of admixtures in order to establish practically pure helium chamber-target. The chamber operation is studied with different methane (0.3-10%) admixtures, water vapours (up to 1% and helium pressure up to 5 atm). It is shown that in order to register with success streamer shadowgraphs in helium the following conditions should be accomplished: 1. a streamer chamber is to be carefully cleaned from various impurities; 2. water vapours (0.1-0.8%) are to be introduced into the chamber at small methane admixtures (<1%). A conclusion is drawn that the charged particle track laser registration with a HSC may be successful at helium pressure up to 5 atm with introduction into a chamber minor amounts of methane admixtures and water vapours

  5. Solar flare accelerated isotopes of hydrogen and helium. [observed by IMP-4 and IMP-5

    Anglin, J. D.; Dietrich, W. F.; Simpson, J. A.

    1973-01-01

    Measurements of solar flare hydrogen, deuterium, tritium, helium-3, and helium-4 in the energy range approximately 10 to 50 MeV per nucleon obtained with instrumentation on the IMP-4 and IMP-5 satellites are reported and studies based on these results which place several constraints on theories of solar flare particle acceleration are discussed. A brief review of previous work and the difficulties in studying the rare isotopes of hydrogen and helium is also included. Particular emphasis is placed on the fact that the information to be obtained from the solar flare products of high energy interactions is not available through either solar wind observations where both the acceleration mechanism and the coronal source of the nuclear species are different, or optical measurements of solar active regions.

  6. Kapitza conductance between Gd3Ga5O12 and superfluid helium

    The thermal conductance at the interface between Gd3Ga5O12 and superfluid helium (Kapitza conductance), is a fundamental data for magnetic cooling applications using this material. It has been observed that the heat flux over the interface can be increased by a factor of 2 when the surface is polished

  7. Commissioning report of the MuCool 5 Tesla solenoid coupled with helium refrigerator

    Geynisman, Michael; /Fermilab

    2010-05-01

    MuCool 5T solenoid was successfully cooled down and operated coupled with MTA 'Brown' refrigerator. The system performed as designed with substantial performance margin. All process alarms and interlocks, as well as ODH and fire alarms, were active and performed as designed. The cooldown of the refrigerator started from warm conditions and took 44 hours to accumulate liquid helium level and solenoid temperature below 5K. Average liquid nitrogen consumption for the refrigerator precool and solenoid shield was measured as 20 gal/hr (including boil-off). Helium losses were small (below 30 scfh). The system was stable and with sufficient margin of performance and ran stably without wet expansion engine. Quench response demonstrated proper operation of the relieving devices and pointed to necessity of improving tightness of the relieving manifolds. Boil-off test demonstrated average heat load of 3 Watts for the unpowered solenoid. The solenoid can stay up to 48 hours cold and minimally filled if the nitrogen shield is maintained. A list of improvements includes commencing into operations the second helium compressor and completion of improvements and tune-ups for system efficiency.

  8. Development efforts on helium vessel for 5 cell - 650 MHz SRF cavity at RRCAT

    The work focuses on the development of helium vessel which houses a 5 cell - 650 MHz SRF niobium cavity and serves as a helium bath to maintain the cavity at 2 K. The vessel has provision for changing the axial length of the cavity for tuning purpose by using a tuning mechanism and a large bellow. Titanium has been chosen as a material of construction of the vessel due to its coefficient of thermal expansion being close to that of niobium. Efforts have been initiated to understand the functional requirements, design requirements, acceptance criteria for design and analysis, non-destructive examination requirements, inspection and testing requirements, manufacturing technology of the titanium vessel and its integration with the SRF cavity. The welding assumes a special significance as titanium is highly reactive and ductility of the weld joint is lost in the presence of air and other impurities. A trial vessel has been conceptualised having typical sizes and geometries. The manufacturing features of vessel are based on ASME B and PV Code, Section VIII Division-1 and manufacturing of this vessel has been started at an Indian industry. Quality assurance plan for this work is developed. The paper describes the work done at RRCAT on the functional and integration requirements, overall design requirements, design methodology to achieve code conformance, manufacturing technology and QAP being used in the development of helium vessel. (author)

  9. Antiprotonic helium

    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)

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

    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.

  11. Interaction of positronium with helium atoms - the classical treatment of the 5-body collision system

    The interaction between positronium and a helium atom is studied using the 5-body classical trajectory Monte Carlo method. We present the total cross sections for the dominant channels, namely for single ionization of the target, and ionization of the projectile, resulting from pure ionization and also from electron transfer (capture or loss) processes for 1-5.7 a.u. incident velocities of the positronium atom. While the pure ionization channel is a one step, the ionization channel in combination with electron capture and loss is a two-step process. Eighteen different classical final states were distinguished. Our results were compared with the calculated data using hydrogen projectiles having the same velocities as well as with the experimental data in collisions between H and He [R.D. DuBois, A. Koever, Phys. Rev. A 40, 3605 (1989)]. We analyze the similarities and deviations for ionization of helium atoms by positronium and hydrogen projectile impact. We have shown that the projectile velocity dependent cross sections for the two major channels have very similar shapes. The agreement with the experimental results is excellent for the case of target single ionization and less satisfactory for projectile ionization. This is especially visible at high velocities. While for the case of target single ionization the absolute total cross sections are nearly the same for Ps or H projectiles for the case of projectile ionization the cross section is about two times higher for Ps than for H. This fact can be attributed to the difference between the binding energy of Ps and H

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

    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.

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

    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

  14. Helium gas-bubble formation and blistering in metallic glass Ni45Fe5Co20Cr10Mo4B16

    We report here the formation of helium gas bubbles in a nickel based metallic glass Ni45Fe5Co20Cr10Mo4B16 after 50 keV helium ion irradiations at room temperature studied by transmission electron microscopy. At higher doses bubbles eventually grow and deform the material surface plastically leading to blister formation. Critical dose for blister formation is determined . Helium gas bubble formation is associated with partial crystallisation of the glass which can be observed from selected area diffraction from the region where bubbles are formed. Microhardness measurements are also performed on the irradiated samples as a function of dose. Increase in the microhardness has been observed after a dose at which helium bubbles are formed. (author)

  15. Thermal–hydraulic system study of the HELOKA-LP helium loop using RELAP5-3D code

    Highlights: • Thermal–hydraulic system study for the HELOKA-LP using RELAP5-3D. • Validation of various experiments with corresponding simulations, and good comparison between the experiments and the simulations. • Simulation of the two most heated compartments of IFMIF HFTM in the modeled helium loop and prediction of the loop dynamic. -- Abstract: The thermal–hydraulic system analyses for the HELOKA-LP (Helium Loop Karlsruhe – Low Pressure) facility are presented. Typical operation ranges for the test section are mass flow rate between 12 and 120 g/s, inlet temperature between 10 and 250 °C and pressure level between 0.3 and 0.6 MPa. An orifice is used for the loop testing, for which different experiments are validated with appropriate simulations. Afterwards instead of the orifice, two most heated compartments of IFMIF (International Fusion Materials Irradiation Facility) HFTM (high flux test module) are simulated in HELOKA-LP. Using the system code REALP5-3D components in the loop are modeled as well as the main control strategy. With this model the loop dynamics in conditions relevant for the HFTM operation are analyzed and the thermal time constant of the compartment is estimated

  16. Patterning, Characterization and Chemical Sensing Applications of Graphene Nanoribbon Arrays Down to 5 nm Using Helium Ion Beam Lithography

    Abbas, Ahmad; Liu, Gang; Liu, Bilu; Zhang, Luyao; Liu, He; Ohlberg, Douglas; Wu, Wei; Zhou, Chongwu

    2014-03-01

    Bandgap engineering of graphene is an essential step towards employing graphene in electronic and sensing applications. Recently, graphene nanoribbons (GNRs) were used to create a bandgap in graphene and function as a semiconducting switch. Although GNRs with widths of report patterning, characterization and superior chemical sensing of ultra-narrow aligned GNR arrays down to 5 nm width using helium ion beam lithography (HIBL) for the first time. The patterned GNR arrays possess narrow and adjustable widths, high aspect ratios, and relatively high quality. Field-effect transistors were fabricated on such GNR arrays and temperature-dependent transport measurements show the thermally activated carrier transport in the GNR array structure. Furthermore, we have demonstrated exceptional NO2 gas sensitivity of the 5 nm GNR array devices down to ppb levels. The results show the potential of HIBL fabricated GNRs for the electronic and sensing applications. We would like to thank HP labs for the use of helium ion microscope. We thank Professor Kang L. Wang and Stephen B. Cronin for help with some of the experiments. We acknowledge the office of Naval Research for financial support.

  17. π-Helium-4 scattering experiment at 5GeV/c. Data processing

    The context of this work is an experiment realised at CERN, with the object to search pre-existing isobaric states in helium nucleus, by means of the study of scattering reactions of π- with simultaneous observation of recoil nucleus (3He or 3H) and forward pion. In this work, only the study of recoil detectors is done. This one, described with many details consists of a set of four wire chamber planes, two planes of semiconductors and two scintillators planes. The performances of this set of detectors are presented in regard to identification of recoil particle, energy and recoil angle measurements. A 'missing mass' analysis of the events of the experiment is done. Preliminary results of elastic and inelastic scattering are given. For elastic scattering a qualitative comparison is done with the multiple scattering Glauber formalism

  18. Measured Performance of Four New 18 kW@4.5 K Helium Refrigerators for the LHC Cryogenic System

    Gruehagen, Henning

    2005-01-01

    The cryogenic system for the Large Hadron Collider (LHC) under construction at CERN will include four new 4.5 K-helium refrigerators, to cover part of the cooling needs of the LHC at the 4.5-20 K and 50-75 K levels. Two refrigerators are delivered by Air Liquide, France, and two by Linde Kryotechnik, Switzerland. During the last three years, all four refrigerators have been installed and commissioned at four different points along the LHC. The specified requirements of the refrigerators are presented, with special focus on the capacities at the various temperature levels. The capacities of the refrigerators were measured using a dedicated test cryostat, and the measured performance for all four installations is presented, and compared to the guaranteed performance in the original proposal of the suppliers. Finally, the process design of the two supplies is compared, and their differences and similarities briefly analysed.

  19. Proposal for the award of a contract, without competitive tendering, for the upgrade of the 4.5 K helium refrigerators at LHC points 2 and 8

    2005-01-01

    This document concerns the award of a contract, without competitive tendering, for the upgrade of the 4.5 K helium refrigerators at LHC points 2 and 8. The Finance Committee is invited to agree to the negotiation of a contract, without competitive tendering, with AIR LIQUIDE (FR) for the upgrade of the 4.5 K helium refrigerators at LHC points 2 and 8 for a total amount of 1 094 280 euros (1 650 000 Swiss francs), not subject to revision. The amount in Swiss francs has been calculated using the present rate of exchange.

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

    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...

  1. Helium cryogenics

    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...

  2. A liquid helium saver

    A cryostat equipped with a 'liquid helium saver' is described. A mass flow rate M of helium gas at high pressure is injected in a counter-flow heat exchanger extending from room to liquid helium temperature. After isenthalpic expansion through a calibrated flow impedance this helium gas returns via the low pressure side of the heat exchanger. The helium boil-off of the cryostat represents a mass flow rate m, which provides additional precooling of the incoming helium gas. Two operating regimes appear possible giving nearly the same efficiency: (1) high pressure (20 to 25 atm) and minimum flow (M . L/W approximately = 1.5) which would be used in an open circuit with helium taken from a high pressure cylinder; and (2) low pressure (approximately = 3 atm), high flow (M . L/W > 10) which would be used in a closed circuit with a rubber diaphragm pumping-compressing unit; both provide a minimum theoretical boil-off factor of about 8%. Experimental results are reported. (U.K.)

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

    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.

  4. Linear series of stellar models. Pt. 5. Hydrogen-helium stars of 0.6, 0.7, 1, 1.5, 2, 3 and 5 M(solar masses)

    The linear series of models are constructed for stars of 0.6, 0.7, 1, 1.5, 2, 3, and 5 M(solar masses). Models consist of hydrogen rich envelopes (X=0.7, Y=0.27, Z=0.03) and helium cores (X=0.0, Y=0.97, Z=0.03), and they have a rectangular hydrogen profile, X(Msub(r)). The linear series are found to be of four types. For stars in the mass range 0.3< M/M(solar masses)<1.4 two different linear series can be constructed. For a star of about 0.66 M(solar masses) the two linear series may have a common bifurcation point. In some cases an analogy may be found between the evolutionary tracks and the linear series. We can identify such points as the Schoenberg-Chandrasekhar isothermal core mass limit, the core helium flash, and the minimum mass for helium burning. (author)

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

    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

  6. Proposal for the award of a contract, without competitive tendering, for the upgrade of the 4.5 K helium refrigerators at LHC points 4 and 6

    2004-01-01

    This document concerns the award of a contract, without competitive tendering, for the upgrade of the 4.5 K helium refrigerators at LHC points 4 and 6. The Finance Committee is invited to agree to the negotiation of a contract, without competitive tendering, with LINDE KRYOTECHNIK (CH) for the upgrade of the 4.5 K helium refrigerators at LHC points 4 and 6 for a total amount of 1 917 600 Swiss francs, not subject to revision, with options for additional work for leak testing and leak repairs for an additional amount not exceeding 190 000 Swiss francs, not subject to revision, and for the modification of the spare turbines and related spare parts for an additional amount of 371 400 Swiss francs, not subject to revision, bringing the total maximum amount to 2 479 000 Swiss francs, not subject to revision

  7. Helium cryopumping for fusion applications

    Large quantities of helium and hydrogen isotopes will be exhausted continuously from fusion power reactors. This paper summarizes two development programs undertaken to address vacuum pumping for this application: (i) A continuous duty cryopump for pumping helium and/or hydrogen species using charcoal sorbent and (ii) a cryopump configuration with an alternative shielding arrangement using charcoal sorbent or argon spray. A test program evaluated automatic pumping of helium, helium pumping by charcoal cryosorption and with argon spray, and cryosorption of helium/hydrogen mixtures. The continuous duty cryopump pumped helium continuously and conveniently. Helium pumping speed was 7.7 l/s/cm2 of charcoal, compared to 5.8 l/s/cm2 for the alternative pump. Helium speed using argon spray was 18% of that obtained by charcoal cryosorption in the same (W-panel) pump. During continuous duty cryopump mixture tests with helium and hydrogen copumped on charcoal, gas was released sporadically. Testing was insufficient to explain this unacceptable event

  8. Characterization of helium surface-wave plasmas at intermediate pressures (550?Torr): temperatures and density of metastable atoms in the 23s level

    A stationary surface wave discharge is studied in helium gas at intermediate pressure. By optical emission spectroscopy, rotational temperatures derived from impurities molecular bands have been studied, as well as the excitation temperature from the Boltzmann plot method of helium lines, as a function of gas pressure, absorbed power and axial position. The rotational temperature of OH molecules is supposed to be in thermal equilibrium with the plasma gas and is used for determining its temperature. The influence of the tube diameter has also been studied; it was observed that the tubes with smaller diameter lead to higher gas temperature. By optical absorption spectroscopy, the density of metastable atoms (in 23s level) has been studied as a function of the parameters. An important dependence on the gas pressure has been observed. Indeed, a one order of magnitude reduction is obtained when the pressure increases from 5 to 50?Torr. The density of metastable atoms remains constant as a function of power and almost all along the plasma column. Finally, a collisional-radiative model was used to compare the experimental to the theoretical results of the density of metastable atoms providing at the same time estimations of the density and the temperature of the electrons as well as the density of helium (atomic and molecular) ions. Results showed a good agreement when the tube diameter is large, but for smaller tubes, the agreement was obtained only for the higher gas pressures. (paper)

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

    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)

  10. Helium behaviour in nuclear glasses

    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)

  11. Exotic helium atoms

    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)

  12. Helium cooled nuclear reactors

    A closed loop coolant circuit for a helium cooled high temperature reactor is described. The circuit has a conventional purification by-pass loop including an oxidizing bed for impurities and an absorption bed for the oxidized impurities. A recycle pipe line is provided whereby a fraction of wet gas leaving the oxidizing bed is returned to the main coolant circuit. 8 claims, 5 drawing figures

  13. Labarge liquid helium plant

    New applications for helium have resulted in a significant growth in helium demand. This growth has contributed to development of larger, more efficient liquid helium production plants. The liquid helium plant at LaBarge is sized for 4,600 liters per hour of liquid helium production (dewar mass gain basis) using 2 purification/liquefaction plant trains. A liquid nitrogen forecooled refrigerator having a power consumption similar to the liquefier cycle would provide about 10,000 watts of refrigeration at liquid helium temperature. Operating experience with liquid helium production facilities has demonstrated reliable commercial operation. 1 ref., 7 fig

  14. Ionized helium afterglow study

    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

  15. Helium in inert matrix dispersion fuels

    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

  16. Orion A helium abundance

    The 22.4-GHz (H,He)66-alpha and 36.5-GHz (H,He)56-alpha radio recombination lines have been observed at several Jaffe-Pankonin positions in the central part of the Orion A source. The measured relative abundance of ionized helium increases with distance, averaging 11.6 percent at peripheral points. The observed behavior is interpreted by a blister-type model nebula, which implies that Orion A has a true He abundance of 12 percent, is moving with a radial velocity of 5 km/sec, and is expanding. 18 references

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

    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

  18. Helium retention and early stages of helium-vacancy complexes formation in low energy helium-implanted tungsten

    Lhuillier, P. E.; Belhabib, T.; Desgardin, P.; Courtois, B.; Sauvage, T.; Barthe, M. F.; Thomann, A. L.; Brault, P.; Tessier, Y.

    2013-02-01

    Tungsten has been selected as the material of the divertor of the ITER fusion reactor. In operation, tungsten will be submitted to high alpha particles bombardment. The consequence of helium implantation is a major issue for the reliability of tungsten components. The aim of the study was to investigate the behavior of helium implanted in tungsten at low energy and low flux. 320 eV Helium ions were introduced by plasma immersion at the flux of 2.5 × 1018 ion/m-2/s-1. The helium behavior was investigated by Nuclear Reaction Analysis and the evolution of the tungsten lattice by Positron Annihilation Spectroscopy (PAS). Helium-implanted tungsten exhibits a low retention rate (13.6% at 9.4 × 1019 He m-2) which decreases with the implantation fluence. The desorption of helium starts at low temperature (<400 K). SEM analysis after annealing over 973 K shows sparse pores probably due to bubbles opening at the surface. The creation of helium-filled defects in the near surface layer (0.5 to ˜20 nm) was followed by PAS. A low level of damages was introduced by 12 MeV proton irradiation, prior to He introduction and allowed to examine the influence of pre-existing defects on the helium trapping. The PAS results suggest that the early stage of the formation of helium-filled vacancy clusters does not require the presence of pre-existing vacancy and thus proceed from the trap mutation phenomenon.

  19. Helium retention and early stages of helium-vacancy complexes formation in low energy helium-implanted tungsten

    Tungsten has been selected as the material of the divertor of the ITER fusion reactor. In operation, tungsten will be submitted to high alpha particles bombardment. The consequence of helium implantation is a major issue for the reliability of tungsten components. The aim of the study was to investigate the behavior of helium implanted in tungsten at low energy and low flux. 320 eV Helium ions were introduced by plasma immersion at the flux of 2.5 1018 ion/m?2/s?1. The helium behavior was investigated by Nuclear Reaction Analysis and the evolution of the tungsten lattice by Positron Annihilation Spectroscopy (PAS). Helium-implanted tungsten exhibits a low retention rate (13.6% at 9.4 1019 He m?2) which decreases with the implantation fluence. The desorption of helium starts at low temperature (<400 K). SEM analysis after annealing over 973 K shows sparse pores probably due to bubbles opening at the surface. The creation of helium-filled defects in the near surface layer (0.5 to ?20 nm) was followed by PAS. A low level of damages was introduced by 12 MeV proton irradiation, prior to He introduction and allowed to examine the influence of pre-existing defects on the helium trapping. The PAS results suggest that the early stage of the formation of helium-filled vacancy clusters does not require the presence of pre-existing vacancy and thus proceed from the trap mutation phenomenon

  20. Electrons at helium interfaces

    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.

  1. Dynamics and helium distribution in hydrogen-helium fluid planets

    A semiquantitative analysis of the thermal and compositional history of an evolving hydrogen-helium planet such as Jupiter or Saturn is presented. First, the evolution of a homogeneous planet with no first-order phase transitions or immiscibilities is considered. Adiabatic, evolutionary models are discussed. The times taken for Jupiter and Saturn to reach their observed luminosities are about 4 x 109 and 2 x 109 years, respectively, essentially independent of formation details. The result for Saturn appears to be inconsistent with its actual age, assumed to be approx.4.5 x 109 years.Next, the effects of a first-order molecular-metallic hydrogen transition are discussed for a pure hydrogen planet: A well-defined interface between the phases persists, despite the presence of convection. The temperature is continuous at the interface and the entropy is discontinuous, the charge in entropy being equal to the latent heat of transition. Consequently, the heat content and derived ''age'' differ from the determined for a purely adiabatic model (by a factor between 1 and 2, depending on the unknown latent heat). Convection in the presense of a composition gradient is discussed, and the importance of overstable modes and diffusive-convective equilibria established. The convective transport of helium away from a localized helium source is shown to be inefficient because helium diffusivity is much less than heat diffusivity. Evolutions with helium immiscibility are discussed

  2. Comparison of experimental and theoretical electron ejection cross sections in helium by proton impact from 5 to 100 keV

    Absolute values of doubly differential cross sections are obtained for electron production in helium by 5- to 100-keV proton impact. The measured values along with earlier data at higher energies are compared with theoretical plane-wave Born-approximation functions obtained from a Hartree-Fock potential. Not only is good agreement obtained at high impact energies (above 300 keV), but fairly good agreement is found at low energies (below about 20 keV). For electrons ejected in the backward hemisphere, unexpectedly poor agreement is noted at intermediate energies where the measured cross sections dip to 50% of the calculated values in some cases. Singly differential cross sections integrated over all angles agree quite well with the theoretical calculations over all ranges of parameters studied. Singly differential cross sections integrated over all electron energies tend to be more isotropic in angle as the proton energy is decreased from 100 to 5 keV. Total cross sections for electron production are also obtained which compare reasonably well with those of Solov'ev et al. but which are higher than those of de Heer et al. It is shown that the contribution to the cross section by the mechanism of charge transfer to the continuum decreases as the impact energy decreases, contrary to the prediction of Salin's treatment

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

    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.

  4. A liquid helium irradiation facility

    A much simpler lower-powered system - a liquid helium irradiation facility - was designed to irradiate samples of electrical insulation at the temperature of liquid helium both in the UTR-300 reactor and the 60Co gamma source at SURRC. Following irradiation to the desired dose, the cryostat with the insulation sample still held cold at ∼ 5 K is removed from the nuclear radiation flux to a test area where electrical measurements are performed to investigate remanent radiation effects on certain electrical characteristics of the test specimens. (author)

  5. Metallic helium in massive planets

    Stevenson, David J.

    2008-01-01

    In this issue of PNAS, Stixrude and Jeanloz (4) show that band closure in pure helium occurs at lower pressures than previously thought, provided the effect of high temperatures is taken into account. This suggests that helium behaves as a metal, at least at the highest pressures encountered in Jupiter and perhaps over a wider range of pressures in the many, often much hotter, planets of Jupiter’s mass and larger that are now evidently common in the universe (5). The full thermodynamic and tr...

  6. Direct photoionization of excited helium

    The sensitivity of direct photoionization characteristics of the excited helium to the inclusion of the closed channels and to the choice of the structure models of the continuum and initial states in an energy region below the resonances converging to the second threshold is investigated. 37 refs.; 6 figs.; 5 tabs

  7. Ratio of helium double-to-single ionization with 100 MeV/u C5+ and C6+ projectiles

    The single and double ionization of He was examined with 100 MeV/u C5+ and C6+ ions produced in the K1200 Cyclotron at Michigan State University. The He+ and He2+ ions were recorded in coincidence with the outgoing charge-state selected projectiles using a time-of-flight recoil-ion detection. Special care was taken to assure single collision conditions and to correct for random background events. The ratio of double-to-single ionization for C6+ projectiles was found to be (0.240.05)%, in good agreement with the theoretical asymptotic limit of 0.26% for charged particle impact and previous measurements with high energy Ne10+ ions. In the case of C5+ projectiles there are two reaction channels, direct ionization (the outgoing projectile is C5+) and ionization of He accompanied by electron loss from the projectile (the outgoing projectile is C6+). For single ionization of He the ratio of the cross sections for these two processes was found to be 1.52 0.03 whereas for double ionization the ratio is 1.110.24. The ratio of outgoing charge was found to be (0.250.05)%, whereas in the case of accompanying electron loss from the projectile this ratio is (0.330.07)%

  8. Helium-3 and diffuse Helium-4 emissions prior the 2014-15 Fogo eruption, Cape Verde

    Asensio-Ramos, Mara; Padrn, Eleazar; Dionis, Samara; Sumino, Hirochika; Fernandes, Paulo; Melin, Gladys V.; Barrancos, Jos; Hernndez, Pedro A.; Rodrguez, Ftima; Silva, Snia; Prez, Nemesio M.; Padilla, Germn; Bandomo, Zuleyka; Cabral, Jeremias; Calvo, David; Pereira, Jos Manuel; Semedo, Helio

    2015-04-01

    On November 23, 2014 a new volcanic eruption started at the southwestern flank of Pico do Fogo volcano (Fogo Island, Cape Verde) after 19 years of the last eruptive event. Helium-3 emission from fumarole discharges and diffuse helium-4 degassing studies have been carried out regularly at the summit crater of Pico do Fogo since May 2007 until March 2014. The first published data on helium isotopes and diffuse helium-4 degassing from Pico do Fogo volcano is related to the field work performed on February 2010 which shows already relatively high helium-3 emission, 8.53 0.9 R/RA (being R and RA the sample and atmospheric 3He/4He isotope ratio, respectively), and diffuse helium-4 degassing rate, 4.2 0.2 kg d-1 (Dionis et al., 2015). During the eight year period 2007-2014, helium-4 emission rate was measured yearly at 50 different sampling sites selected in the surface environment of the summit crater of Pico do Fogo (0.14 km2) following the Darcy's law, and assuming that helium-4 emission is mainly governed by convection. The distribution of the sampling sites was carefully chosen to homogeneously cover the target area, allowing the computation of the total helium-4 emission by sequential Gaussian simulation (sGs). In addition, helium-3 emission was measured in the fumarole gases following the method described by Sumino et al. (2001). During the eight year period, convective helium-4 emission ranged between 1.2 and 5.7 kg d-1, and helium-3 emission between 7.73 and 8.82 R/RA. Both helium-4 and helium-3 emission showed significant increases on February 2010, suggesting a potential magma intrusion into the volcanic system of Pico do Fogo. However, the highest observed values of both parameters were observed on November, 2013 (helium-3 emission) and on March 2014 (diffuse helium-4 emission) suggesting a second magma intrusion giving rise to the volcanic eruption on November 23, 2014. As was observed in other volcanic systems (Padrn et al., 2013), helium degassing monitoring in oceanic volcanic islands could be an excellent early warning geochemical precursory signal for volcanic unrest. Dionis et al. (2015), Bull. Volcanol., in press ; Padrn et al., (2013), Geology 41 (5) 539-542.; Sumino et al., (2001), J. Mass Spectrom. Soc. Jpn. 49, 61-68.

  9. Antiprotonic Helium Atoms

    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.

  10. Cooling with Superfluid Helium

    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

  11. Helium bubble kinetics during laser welding of helium-doped stainless steel

    Helium is generated within neutron-irradiated reactor components and entrapped in the stainless steel components. The repair of the components using conventional GTA welding practices is then exceedingly difficult, because of the creation of helium bubbles and weld cracking. In this research, the behavior of helium bubbles in austenitic stainless steel weldments was investigated using stainless steel helium ion-implanted and then welded using YAG Laser apparatus. Helium ion implanting of the sample was carried out using 8MeV implantation apparatus, the sample being doped 2.45χ1019/m2 at 6MeV and then doped 1χ1019/m2 at 5MeV. Helium bubbles are present at the bond region, heat-affected zone and weld metal. An increase of weld heat input causes the growth of helium bubbles and produce toe cracks and cracks along the dendrite cell boundary in the weld metal. The helium bubble phenomena can be simulated in the weld metal and in the heat-affected zone during repair welding using helium ion implanting technique. (author)

  12. Helium retention and early stages of helium-vacancy complexes formation in low energy helium-implanted tungsten

    Lhuillier, P.E., E-mail: pierre-emile.lhuillier@mines-nancy.org [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans cedex 2 (France); Université d’Orléans, Faculté des Sciences, Avenue du Parc Floral, BP 6749, 45067 Orléans cedex 2 (France); Belhabib, T.; Desgardin, P.; Courtois, B.; Sauvage, T.; Barthe, M.F. [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans cedex 2 (France); Université d’Orléans, Faculté des Sciences, Avenue du Parc Floral, BP 6749, 45067 Orléans cedex 2 (France); Thomann, A.L.; Brault, P.; Tessier, Y. [GREMI Polytech’Orléans, 14 rue D’Issoudun, BP 6744, 45 067 Orléans cedex 2 (France)

    2013-02-15

    Tungsten has been selected as the material of the divertor of the ITER fusion reactor. In operation, tungsten will be submitted to high alpha particles bombardment. The consequence of helium implantation is a major issue for the reliability of tungsten components. The aim of the study was to investigate the behavior of helium implanted in tungsten at low energy and low flux. 320 eV Helium ions were introduced by plasma immersion at the flux of 2.5 × 10{sup 18} ion/m{sup −2}/s{sup −1}. The helium behavior was investigated by Nuclear Reaction Analysis and the evolution of the tungsten lattice by Positron Annihilation Spectroscopy (PAS). Helium-implanted tungsten exhibits a low retention rate (13.6% at 9.4 × 10{sup 19} He m{sup −2}) which decreases with the implantation fluence. The desorption of helium starts at low temperature (<400 K). SEM analysis after annealing over 973 K shows sparse pores probably due to bubbles opening at the surface. The creation of helium-filled defects in the near surface layer (0.5 to ∼20 nm) was followed by PAS. A low level of damages was introduced by 12 MeV proton irradiation, prior to He introduction and allowed to examine the influence of pre-existing defects on the helium trapping. The PAS results suggest that the early stage of the formation of helium-filled vacancy clusters does not require the presence of pre-existing vacancy and thus proceed from the trap mutation phenomenon.

  13. Metal tritides helium emission

    Over the past several years, we have been measuring the release of helium from metal tritides (primarily erbium tritide). We find that qualitatively all tritides of interest to us behave the same. When they are first formed, the helium is released at a low rate that appears to be related to the amount of surface area which has access to the outside of the material (either film or bulk). For example, erbium tritide films initially release about 0.3% of the helium generated. Most tritide films emit helium at about this rate initially. At some later time, which depends upon the amount of helium generated, the parent occluding element and the degree of tritium saturation of the dihydride phase the helium emission changes to a new mode in which it is released at approximately the rate at which it is generated (for example, we measure this value to be approx. = .31 He/Er for ErT1.9 films). If erbium ditritide is saturated beyond 1.9 T/Er, the critical helium/metal ratio decreases. For example, in bulk powders ErT2.15 reaches critical release concentration at approx. = 0.03. Moderate elevation of temperature above room temperature has little impact on the helium release rate. It appears that the process may have approx. = 2 kcal/mol activation energy. The first helium formed is well bound. As the tritide ages, the helium is found in higher energy sites. Similar but less extensive measurements on scandium, titanium, and zirconium tritides are also described. Finally, the thermal desorption of erbium tritides of various ages from 50 days to 3154 days is discussed. Significant helium is desorbed along with the tritium in all but the youngest samples during thermodesorption

  14. Helium refrigeration considerations for cryomodule design

    Ganni, V.; Knudsen, P. [Thomas Jefferson National Accelerator Facility (JLab), Newport News, VA 23606 (United States)

    2014-01-29

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

  15. Helium purification system

    The processes for helium purification including adsorption, condensing, freezing, PSA (Pressure Swing Adsorption) and membrane permeation are reviewed and the advantages and disadvantages of each process are evaluated. For an optimum system, the most appropriate processes have to be combined according to the specifications for concentrations of impurities, continuous operation time of the helium liquefier and the utility cost. (author)

  16. Helium the disappearing element

    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...

  17. Line ratio diagnostics in helium and helium seeded argon plasmas

    Boivin, R F [Department of Physics, Auburn University, Auburn, AL 36849-5311 (United States); Loch, S D [Department of Physics, Auburn University, Auburn, AL 36849-5311 (United States); Ballance, C P [Physics Department, Rollins College, White Park, FL 32789 (United States); Branscomb, D [Department of Physics, Auburn University, Auburn, AL 36849-5311 (United States); Pindzola, M S [Department of Physics, Auburn University, Auburn, AL 36849-5311 (United States)

    2007-08-15

    We investigate the potential use of line ratio diagnostics to evaluate electron temperature in either helium or helium seeded argon plasmas. Plasmas are produced in a helicon plasma source. A rf compensated Langmuir probe is used to measure both the electron temperature and plasma density while a spectrometer is used to measure He I line intensities from the plasma. For all plasma densities where the electron temperature remains at 5 {+-} 1 eV, three He line ratios are measured. Each experimental ratio is compared with the prediction of three different collisional radiative models. One of these models makes uses of recent R-matrix with pseudo-states calculations for collisional rate coefficients. A discussion related to the different observations and model predictions is presented.

  18. Peculiarities of helium bubble formation and helium behavior in vanadium alloys of different chemical composition

    The influence of alloying of vanadium by Ti and Fe on helium bubble formation, gaseous swelling and helium release peculiarities is investigated by means of transmission electron microscopy and helium thermal desorption spectrometry (HTDS). The samples were irradiated by 40 keV He+ ions up to a fluence of 5 ⋅ 1020 m−2 at 293 and 923 K. It is found that large faceted pores/bubbles are formed in pure vanadium and it has the highest gaseous swelling. Alloying by any used quantity of Ti (from 0.1 up to 10 wt.%) or Fe (from 1 up to 10 wt.%) essentially decreases the helium swelling. The effect of alloying of vanadium by Ti on the bubble sizes and the helium swelling is nonmonotonic. The density of bubbles increases significantly and their sizes and swelling grow monotonically with increasing the Fe content in vanadium. With low-temperature helium implantation, alloying of V by Ti shifts the HTDS peaks to higher temperatures and the temperatures of peaks are decreased with increasing the Fe concentration. A significant portion of the helium releases in a high-temperature area beyond the main peak temperatures in the HTDS spectra. It is assumed that this is caused by formation of helium bubbles on the surfaces of incoherent particles of secondary phases (oxides, nitrides), having high binding energies with these particles

  19. Peculiarities of helium bubble formation and helium behavior in vanadium alloys of different chemical composition

    Staltsov, M.S.; Chernov, I.I.; Kalin, B.A.; Oo, Kyi Zin; Polyansky, A.A.; Staltsova, O.S.; Aung, Kyaw Zaw [National Research Nuclear University “Moscow Engineering Physics Institute”, Moscow (Russian Federation); Chernov, V.M.; Potapenko, M.M. [A.A. Bochvar High-Technology Research Institute of Inorganic Materials, Moscow (Russian Federation)

    2015-06-15

    The influence of alloying of vanadium by Ti and Fe on helium bubble formation, gaseous swelling and helium release peculiarities is investigated by means of transmission electron microscopy and helium thermal desorption spectrometry (HTDS). The samples were irradiated by 40 keV He{sup +} ions up to a fluence of 5 ⋅ 10{sup 20} m{sup −2} at 293 and 923 K. It is found that large faceted pores/bubbles are formed in pure vanadium and it has the highest gaseous swelling. Alloying by any used quantity of Ti (from 0.1 up to 10 wt.%) or Fe (from 1 up to 10 wt.%) essentially decreases the helium swelling. The effect of alloying of vanadium by Ti on the bubble sizes and the helium swelling is nonmonotonic. The density of bubbles increases significantly and their sizes and swelling grow monotonically with increasing the Fe content in vanadium. With low-temperature helium implantation, alloying of V by Ti shifts the HTDS peaks to higher temperatures and the temperatures of peaks are decreased with increasing the Fe concentration. A significant portion of the helium releases in a high-temperature area beyond the main peak temperatures in the HTDS spectra. It is assumed that this is caused by formation of helium bubbles on the surfaces of incoherent particles of secondary phases (oxides, nitrides), having high binding energies with these particles.

  20. Studies of helium breakdown at low temperatures

    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)

  1. The diffusion of helium in bcc and hexagonal metals

    Foil specimens (2.5-85.0 ?m) of V, Fe (bcc) and Ti, Co and Mg (hcp) were homogenously implanted with helium to final concentrations between 0.001 ppm and 5 ppm. By subsequent thermal desorption measurements three regimes of different desorption behaviour were identified: 1) Free diffusion determined the helium-release as long as the mean distance between a helium atom and the surface was small compared to the mean distance between the helium atoms. For titanium a substitutional mechanismen was proposed, while in all the other metals helium diffuses by a dissociative mechanism with recapture at thermal vacancies (Mg, Co) and implantation-induced vacancies (V, Fe), respectively. 2) Free diffusion was reduced by the agglomeration of helium atoms. The amount of helium released during free diffusion depended on the thickness d and the helium-concentration c0 as 1/d ?c0. This dependence was explained by a simple agglomeration-model. 3) After the formation of helium-bubbles a small helium-release persisted. This could be explained by two different coarsening mechanismens: Bubble-migration and -coalescence (e.g. Mg) and Ostwald-ripening (e.g. Ti). (orig.)

  2. The Descending Helium Balloon

    Helseth, Lars Egil

    2014-01-01

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

  3. Noncavitating Pump For Liquid Helium

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

    1996-01-01

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

  4. The helium purification system of the HTR-10

    In order to reduce the quantity of chemical impurities in the primary coolant helium and to remove the gaseous radionuclide fission products, a helium purification system mainly composed of a copper oxide bed, a molecular sieve adsorber and a low temperature adsorber is designed for the HTR-10. One actual purification train is designed for a helium flow rate of 10.5 kg h-1, corresponding with a 5% gas change of the helium inventory in primary circuit. It is anticipated that more than 2000 h continuous purification operation will be reached between regeneration

  5. Elementary Excitations of Superfluid Helium Droplets Probed by Ion Spectroscopy.

    Zhang, Xiaohang; Drabbels, Marcel

    2014-09-18

    Electronic spectra of molecules in helium droplets reveal spectral features that are related to the elementary excitations of the superfluid helium environment. In order to determine to what extent the interaction strength of the molecule with the helium affects these excitations, the spectrum corresponding to the B?(2)A? ? X? (2)A? transition of 2,5-difluorophenol cations in helium droplets has been recorded. The vibronic resonances reveal a sharp zero-phonon line whose width is largely determined by the rotational band contour, followed by a broad structureless phonon wing at higher frequencies. The splitting between the zero-phonon line and phonon wing is approximately half of that found for neutral 2,5-difluorophenol. This difference is attributed to the increased helium density around the ion due to its strong interaction with the helium. PMID:26276319

  6. Helium mobility in advanced nuclear ceramics

    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 γ/r with γ 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)

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

    Bohlender, David A; 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 using programs described in earlier papers by Rice and others. An alternative surface abundance mapping code has been used to model the helium line variations after our Doppler imaging of certain individual helium lines produced mediocre results. We confirm the long-known existence of helium-rich and helium-poor hemispheres on a Cen and we measure a difference of more than two orders of magnitude in helium abundance from one side of the star to the other. Helium is overabundant by a factor of about 5 over much of the helium-rich hemispher...

  8. CHARACTERIZING TRITIUM WASTE USING HELIUM RATIOS

    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

  9. Helium bubbles in UO2

    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)

  10. THERMAL UNIFORMITY OF LIQUID HELIUM IN ELECTRON BUBBLE CHAMBER.

    WANG,L.; JIA,L.

    2002-07-22

    A CRYOGENIC RESEARCH APPARATUS TO MEASURE THE MOVEMENT OF ELECTRONS UNDER A HIGH ELECTRIC FIELD IN A LIQUID HELIUM BATH WAS DESIGNED AND BUILT AT THE BROOKHAVEN NATIONAL LABORATORY AND THE NEVIS LABORATORY OF COLUMBIA UNIVERSITY. THE LIQUID HELIUM CHAMBER IS A DOUBLE WALLED CYLINDRICAL CONTAINER EQUIPPED WITH 5 OPTICS WINDOWS AND 10 HIGH VOLTAGE CABLES. TO SHIELD THE LIQUID HELIUM CHAMBER AGAINST THE EXTERNAL HEAT LOADS AND TO PROVIDE THE THERMAL UNIFORMITY IN THE LIQUID HELIUM CHAMBER, THE DOUBLE WALLED JACKET WAS COOLED BY A PUMPED HELIUM BATH. THE HELIUM CHAMBER WAS BUILT INTO A COMMERICAL LN2 / LHE CRYOSTAT. THIS PAPER PRESENTS THE DESIGN AND THE NUMERICAL SIMULATION ANALYSIS ON THERMAL UNIFORMITY OF THE ELECTRON BUBBLE CHAMBER.

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

    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.

  12. Influence of helium implantation technique on molybdenum radiation hardening

    Experimental results of studying radiation hardening of helium-implanted molybdenum in the 10-5-10-2 at.% concentration range are presented. Helium implantation into the material was exercised in a cyclotron by three different methods differing by the quantity ratio of displaced atoms to helium concentration and ''hardness'' of spectra of preliminary knocked-out atoms (PKA). The degree of radiation hardening is shown to essentially depend on the technique of molybdenum cyclotron alloying, and it is not determined only by implanted helium concentration and level of vulnerability to damage but difference in PKA spectra

  13. Measurement of OH density and air-helium mixture ratio in an atmospheric-pressure helium plasma jet

    Yonemori, Seiya; Nakagawa, Yusuke; Ono, Ryo; Oda, Tetsuji

    2012-06-01

    The absolute density of OH radicals in an atmospheric-pressure helium plasma jet is measured using laser-induced fluorescence (LIF). The plasma jet is generated in room air by applying a pulsed high voltage onto a quartz tube with helium gas flow. The time-averaged OH density is 0.10 ppm near the quartz tube nozzle, decreasing away from the nozzle. OH radicals are produced from water vapour in the helium flow, which is humidified by water adsorbed on the inner surface of the helium line and the quartz tube. When helium is artificially humidified using a water bubbler, the OH density increases with humidity and reaches 2.5 ppm when the water vapour content is 200 ppm. Two-dimensional distribution of air-helium mixture ratio in the plasma jet is also measured using the decay rate of the LIF signal waveform which is determined by the quenching rate of laser-excited OH radicals.

  14. Helium transfer line installation details.

    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.

  15. Is solid helium a supersolid?

    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

  16. Cavitation in flowing superfluid helium

    Daney, D. E.

    1988-01-01

    Flowing superfluid helium cavitates much more readily than normal liquid helium, and there is a marked difference in the cavitation behavior of the two fluids as the lambda point is traversed. Examples of cavitation in a turbine meter and centrifugal pump are given, together with measurements of the cavitation strength of flowing superfluid helium. The unusual cavitation behavior of superfluid helium is attributed to its immense thermal conductivity .

  17. Onset Properties of Supersolid Helium

    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 neighboring valley. S...

  18. Helium Production and Possible Projection

    Steve Mohr; James Ward

    2014-01-01

    The future availability of helium has been raised as an issue in the literature. However, a disaggregated projection of helium production has not been attempted, presumably due to the difficult nature of accessing disaggregated historic production data to test the accuracy of this issue. This paper presents collated and estimated historic helium production statistics from 1921 to 2012 for each helium producing country in the world and by U.S. state. A high and regular growth projection of hel...

  19. Helium in Chemically Peculiar Stars

    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 temperature, gravity and he...

  20. Helium resources of the United States, 1991. Information circular/1993

    Hamak, J.E.; Gage, B.D.

    1993-01-01

    The identified helium resources of the United States are estimated at 630 Bcf. This includes 295 Bcf of demonstrated reserves, 87 Bcf of demonstrated marginal reserves, and 42 Bcf of demonstrated subeconomic resources. The identified resources include 161 Bcf of helium in inferred reserves and marginal reserves and 45 Bcf in inferred subeconomic resources. The identified helium resources contained on Federal lands are approximately 172 Bcf, including 32 Bcf in underground storage in the Cliffside Gas Field near Amarillo, Texas. In addition to the identified helium resources, undiscovered helium resources in the United States are estimated at a most likely value of 103 Bcf, with a maximum value of 259 Bcf and a minimum value of 41 Bcf. Also reported are 43 Bcf of helium in nonconventional and low helium content natural gases. Current extraction of helium in the United States occurs mostly from the Hugoton gas area in Kansas and Oklahoma and the Riley Ridge area in southwest Wyoming. Helium extracted from natural gas in the United States in 1990 was 2.5 Bcf.

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

    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 al. Phys. Rev. Let...

  2. Helium leak finding plant

    The invention concerns a helium leak finding plant with a mass spectrometer cell on the suction side of a molecular pump and a mechanical pre-pump, where a test sample or a test sensor is connected between the two pumps. The mechanical pre-pump consists of three successive stages. (orig./HP)

  3. Liquid helium level detector

    Means generally used for liquid helium level measurement are the capacitive or superconductive probes. The signal, generally electric, is collected and treated by electronic means operating at ambiant temperature; they operate the pneumatic or electric command of a control valve; the cold active element of this valve controls the necessary alimentation flow

  4. Cosmological helium production simplified

    The authors 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. The temperature difference between photons and neutrinos during the period in which neutrons and protons interconvert is also neglected. These approximations permit the expression of 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, the authors reduce the calculation of the neutron-proton ratio as a function of temperature to a simple numerical integral. They also estimate the effect of neutron decay on the helium abundance. Their result for this quantity agrees well with precise computer calculations. Their semianalytic formulas are used to determine how the predicted helium abundance varies with such parameters as the neutron lifetime, the baryon-to-photon ratio, the number of neutrino species, and a possible electron-neutrino chemical potential

  5. Cosmological helium production simplified

    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

  6. New experimental device for VHTR structural material testing and helium coolant chemistry investigation High Temperature Helium Loop in NRI ?e

    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 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, CO2, H2, H2O, O2, N2, and CH4) 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 1018 n/m2 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.

  7. Evaluation of helium cooling for fusion divertors

    The divertors of future fusion reactors will have a power throughput of several hundred megawatts. The peak heat flux on the divertor surface is estimated to be 5-15MWm-2 at an average heat flux of 2MWm-2. The divertors have a requirement of both minimum temperature (100 C) and maximum temperature. The minimum temperature is dictated by the requirement to reduce the absorption of plasma, and the maximum temperature is determined by the thermomechanical properties of the plasma facing materials. Coolants that have been considered for fusion reactors are water, liquid metals and helium. Helium cooling has been shown to be very attractive from safety and other considerations. Helium is chemically and neutronically inert and is suitable for power conversion. The challenges associated with helium cooling are (1) manifold sizes, (2) pumping power, and (3) leak prevention. In this paper the first two of the above design issues are addressed. A variety of heat transfer enhancement techniques is considered to demonstrate that the manifold sizes and the pumping power can be reduced to acceptable levels. A helium-cooled divertor module was designed and fabricated by GA for a steady-state heat flux of 10MWm-2. This module was recently (August 1993) tested at Sandia National Laboratories. At the inlet pressure of 4MPa, the module was tested at a steady-state heat flux of 10MWm-2. The pumping power required was less than 1% of the power removed. These results verified the design prediction. ((orig.))

  8. Dynamic Simulation of a Helium Liquefier

    Dynamic behavior of a helium liquefier has been studied in detail with a Cryogenic Process REal-time SimulaTor (C-PREST) at the National Institute for Fusion Science (NIFS). The C-PREST is being developed to integrate large-scale helium cryogenic plant design, operation and maintenance for optimum process establishment. As a first step of simulations of cooldown to 4.5 K with the helium liquefier model is conducted, which provides a plant-process validation platform. The helium liquefier consists of seven heat exchangers, a liquid-nitrogen (LN2) precooler, two expansion turbines and a liquid-helium (LHe) reservoir. Process simulations are fulfilled with sequence programs, which were implemented with C-PREST based on an existing liquefier operation. The interactions of a JT valve, a JT-bypass valve and a reservoir-return valve have been dynamically simulated. The paper discusses various aspects of refrigeration process simulation, including its difficulties such as a balance between complexity of the adopted models and CPU time

  9. Linear electron chains at superfluid helium surface

    The unique one-dimensional system of linear electron chains at liquid helium surface is realized experimentally for the first time. The distortion of the surface of liquid helium covering the profiled dielectric substrate, and the holding electric field confining the electrons to the bottom of the created channels, are used to realize the system. The carrier mobility in the linear electron chains is measured in the temperature range 0.5-1.8 K at holding electric fields up to 1 kV/cm. It is shown that the electron mobility depends on substrate cleanness. For clean substrates the mobility increases with decreasing temperature. The results agree with the existing theory

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

    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...

  11. Calculation of electron-helium scattering

    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

  12. The pulsating extreme helium star BD + 1303224

    Ultraviolet flux variations are reported for the pulsating extreme helium star BD + 1303224 (V652 Her). Effective temperature and angular radius variations over a cycle are determined from static plane-parallel LTE model atmospheres. When compared with radius changes derived from ground-based spectroscopy, the angular radius variations indicate radial pulsations and correspond to a distance of 1.5 +- 0.1 kpc. BD + 1303224 is thought to be a helium-burning star of 0.7 Msolar masses, which has an envelope contracting as the helium-burning core grows; it is similar to HD 144941 and these two stars may constitute a new sub-class of the hydrogen-deficient stars. (author)

  13. Helium diffusion in curium-doped borosilicate waste glass

    The isothermal release of helium from 244Cm-doped borosilicate glass has been studied as a function of time at different annealing temperatures. Helium measurements were performed using a micro gas chromatograph coupled to a furnace installed in a hot cell at ATALANTE nuclear research facility. Plane-parallel glass samples were prepared from glass discs that had been stored for 5.1 years at room temperature, accumulating around 1019 alpha decays per gram of glass, a level that will be reached in current nuclear glass packages several thousand years after disposal. The experimental helium release data were simulated using a 3D numerical model to determine the helium diffusion coefficients. The extracted diffusion coefficients follow the Arrhenius law with an activation energy of 0.61 ± 0.03 eV and a pre-exponential factor of (5.7 ± 1.6) x 10-3 cm2 s-1. The results were compared with literature data on damaged and undamaged glasses to assess the effect of glass damage on helium release. The helium release results are consistent with a thermal diffusion mechanism involving only one population of helium atoms. The helium diffusion coefficients were unaffected by the glass alpha damage.

  14. Helium diffusion in curium-doped borosilicate waste glass

    Fares, T.; Peuget, S.; Bouty, O.; Deschanels, X.; Magnin, M.; Jégou, C.

    2011-09-01

    The isothermal release of helium from 244Cm-doped borosilicate glass has been studied as a function of time at different annealing temperatures. Helium measurements were performed using a micro gas chromatograph coupled to a furnace installed in a hot cell at ATALANTE nuclear research facility. Plane-parallel glass samples were prepared from glass discs that had been stored for 5.1 years at room temperature, accumulating around 10 19 alpha decays per gram of glass, a level that will be reached in current nuclear glass packages several thousand years after disposal. The experimental helium release data were simulated using a 3D numerical model to determine the helium diffusion coefficients. The extracted diffusion coefficients follow the Arrhenius law with an activation energy of 0.61 ± 0.03 eV and a pre-exponential factor of (5.7 ± 1.6) × 10 -3 cm 2 s -1. The results were compared with literature data on damaged and undamaged glasses to assess the effect of glass damage on helium release. The helium release results are consistent with a thermal diffusion mechanism involving only one population of helium atoms. The helium diffusion coefficients were unaffected by the glass alpha damage.

  15. The Weakest Link: Bonding between Helium Atoms

    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.

  16. Neutral muonic helium(3)

    Neutral muonic helium, He++μ-e-, can be considered in two pieces. The (He++μ-)+-system is a hydrogenic ion halfway in size between an atom and a nucleus. It acts like a singly charged pseudo-nucleus to the electron surrounding it. The whole system appears like one hydrogen inside another. Neutral muonic helium can be formed in the ground state in which the coupling of the magnetic moments gives rise to a hyperfine structure (hfs). 3He++μ-e- has three spin one half particles interact without any restrictions by the Pauli exclusion principle. The level diagram of the ground state is shown. There is a large muonic hfs splitting corresponding to the He++μ- ion to be in one of the two spin states with total spin quantum number G = 0 and G = 1. To measure the atomic hfs superimposed on the G = 1 triplet state is the aim of this experiment. (Auth.)

  17. Helium accumulation in groundwater. Pt. 3

    The groundwaters of the Great Artesian Basin (Australia) have been previously shown to be accumulating in-situ production helium for groundwaters ages 100 kyr. New helium isotope measurements show that the observed in-situ production helium (3He/4He ? 1.6x10-8) is isotopically distinct from the crustal degassing helium flux (3He/4He ? 6.6x10-8). Furthermore, the crustal degassing helium isotope ratio is marginally in excess of the whole crustal production ratio (3He/4He = 3.5x10-8) and the production ratio in a variety of continental rock types. This suggests that the upper limit on volatile transport across the mantle-crust boundary beneath the (relatively) stable and 'complacent' Australian continent can be characterized by a 'conductive-diffusive' helium/heat flux ratio of 64He atoms mW-1s-1 which is two orders of magnitude less than the 'intrusive-volcanic' ratio of 2.9x1084He atoms mW-1s-1 measured at the Galapagos. These results constrain the transcrustal mantle degassing fluxes of 4He and 40Ar to be much less than the mid-ocean ridge degassing fluxes; which are much less than the degassing of 4He and 40Ar from continental crust. Thus, the degassing of the Earth's interior is dominated by magmatic processes but the dominant fluxes of 4He and 40Ar to the atosphere must come from the continental crust. (orig.)

  18. Antiprotonic helium atomcules

    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.

  19. Applications of Groundwater Helium

    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.

  20. Education in Helium Refrigeration

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics... and so on.Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity

  1. Purification of helium gas for the helium test loop

    The helium purification system of the Helium Test Loop was constructed for demonstrating test of the High Temperature Gas-cooled Reactor. The helium purification system mainly consists of molecular sieve and cryogenic charcoal bed. It can be served to purify 50 m3/h by-passing helium gas. The results of purifying tests show that more than 20000 cm3/m3 impurity content (including H2O, H2, N2, CO, CO2 CH4, O2, Ar et al) in helium can be decreased to 76 cm3/m3 which is less than the value designed for HTR-10. The test shows that the sensitivity and accuracy of impurity content analyzing and measuring in helium gas is better than 10-1 cm3/m3

  2. Cryosorption vacuum pumping of hydrogen and helium mixtures

    Cryosorption vacuum pumps continue to be the principal type of pumping systems considered for power-producing fusion reactors. In this context, a compound-pump concept is generally employed in which the helium pump is placed behind the hydrogen pump so that hydrogen will not condense on and hence block the 4.2 K helium cryosorption surface. To obtain an optimal design for such a pump, the amount of hydrogen which can reach the helium panel has been determined. Catastrophic failure of a cryosorption pump was observed in previous work when a 95% hydrogen-5% helium mixture was tested. No such failure has occurred in our studies with 4, 10, and 20% hydrogen. However, significant changes in pumping speed have been noted when only 4% hydrogen is present. Both helium and hydrogen speeds are reduced to approximately one-half to one-third of the pure compound speed. Many of the qualitative aspects of the behavior of the pump for pure helium are also observed for the hydrogen-helium mixtures. Cyclic variation in pumping speed above a helium feed rate of approx. 6 x 10-6 torr-L/s.cm2 is one such similarity; however, at the 4% hydrogen level, the period between instabilities is longer for the mixtures

  3. A reexamination of quenches in Helium 4 and Helium 3

    Karra, G.; Rivers, R. J.

    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 its narrow Ginzberg...

  4. Feasibility of lunar Helium-3 mining

    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.

  5. Helium emanometry as an indicator of deeply buried uranium deposits

    Helium emanometry has considerable potential for locating deeply buried uranium deposits. In order to determine whether near surface helium-4 anomalies are present over and in close proximity to deeply buried uranium deposits, helium measurements were carried out at three sites having known uranium ore bodies: the Red Desert in Sweetwater County, Wyoming; Copper Mountain in Fremont County, Wyoming; and Spokane Mountain in Stevens Couty, Washington. At each research site, near surface soil and soil gas (probe) samples were collected. Borehole water and soil gas (collector) samples were also taken at selected locations. The samples were analyzed at the laboratory for their helium, light hydrocarbon, and nitrogen content. In most instances it was not necessary to correct the soil gas data. In determining the quantity of helium-4 present in the soil gas samples, the practical precision was +- 50 ppb. The reproducibility of the helium-4 analyses of the water samples varied from +- 5% to +- 20%. The total error in the calculated soil helium-4 levels ranged from 5% to 10% of the value. The calculated corrected soil, water and oil gas helium-4 results were analyzed employing statistical techniques in order to separate the background and anomalous populations. The anomalous population was divided into five subsets for purposes of data presentation. The data are then presented in the form of histograms, dot maps and anomaly contour density maps.One can conclude that the results from this study confirm that near surface helium anomalies are present in the gas of the soil micropores overlying three types of uranium deposits situated in widely differing geological environments. The data obtained from the soil gas (probe) helium samples are also encouraging in that anomalies were found to be present over portions of the known extent of each of the three deposits

  6. Nucleation, solvation and boiling of helium excimer clusters

    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.

  7. A reciprocating liquid helium pump used for forced flow of supercritical helium

    The performance of a small double acting piston pump for circulating helium in a closed heat transfer loop is described. The pump was manufactured by LINDE AG, Munich, West Germany. The measured flow rate of supercritical helium was about 17 gs-1 (500 lhr-1) with a differential pressure of Δp = 0.5 x 105 Nm-2 at a working pressure of p = 6 x 105 Nm-2. At differential pressures beyond 0.5 x 105 Nm-2 the volumetric efficiency decreases. (author)

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

    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.

  9. Helium-3 from the moon

    Fusion of Helium-3 with deuterium offers and environmentally benign alternative to production of energy from fossil fuels and nuclear fission. Essentially unavailable from terrestrial sources, He-3 is potentially available from the Moon in very large amounts. This paper reports results of a study of the occurrence and distribution of helium on the Moon and lunar features that will govern helium mining and extraction

  10. Cavitation pressure in liquid helium

    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 a series of measur...

  11. Onset Properties of Supersolid Helium

    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 neighboring valley. Such jump process also naturally causes dissipation accompanying the onset of supersolidity.

  12. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    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)...

  13. Simulation of liquid helium

    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

  14. Helium removal and recycling

    Reiter, D.; Wiesen, S

    2004-01-01

    Removal of helium, the ash from the D-T-fusion reaction, from a burning plasma flame, is one of the critical issues for future thermonuclear burning plasma. Even in plasmas driven by additional heating to large Q-values this is a severe problem. Recombination of fuel and ash ions at plasma exposed surfaces, re-emission as neutral particles and subsequent pumping ("recycling") provides, at least in principle, the mechanism to flush the plasma from its ash. However, plasma surface interaction h...

  15. Reciprocating magnetic refrigerator for helium liquefaction

    We have developed a reciprocating magnetic refigerator for liquefying helium from a temperature in the 15 K region. The working material (gadolinium-gallium-garnet (GGG) single crystal, 30 mm in diameter and 40 mm in length) is placed at the end of the piston. When GGG is placed in a high-intensity magnetic field (4.5 T), its temperature rises to 15 K. The inner surface of the cylinder is cooled by an auxiliary refrigerator; the generated heat is removed through the narrow gap between GGG and cylinder (less than 50 um in the 15 K region) filled with gaseous helium. When the magnetic field in the GGG is eliminated by moving the piston, the GGG temperature falls below 4.2 K and the refrigeration occurs by condensing the helium on the GGG surface. Technical emphasis was placed on the realization of a high heat exchange rate between GGG and gaseous helium. A sufficient heat transfer rate was achieved after several component level experiments. Sources of inefficiency to the refrigeration power has been also discussed. Finally a refrigeration power of 0.95 W at 4.2 K was achieved in 0.38 Hz operation by a reciprocating magnetic refrigerator equiped with two pistons

  16. Helium abundance in the Orion A source

    The H, He 66α (22.4 GHz) and H, He 56α (36.5 GHz) recombination line observations were made at several positions of the central region of Orion A (R ∼ 3'). The observed relative helium abundance y' is found to increase with the angular distance from the nebular centre and to amount the mean value of 11.6% at the peripherycal positions. The comparison with the results of low frequency observations (H, He 109α, ν ∼ 5.0 GHz) shows that measurements towards the centre (y'=8-9%) is in agreement with the low frequency measurements of y', however y' at the peripherycal positions are higher than that at low frequency. The nebula model of a ''blister'' type is constructed to explain such behaviour. The conclusions are made that the actual helium abundance y in Orion A is ∼ 12%, the Orion Nebula expands and its radial velocity is ∼ 5 km/s

  17. High Efficiency Regenerative Helium Compressor Project

    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...

  18. Development of 18 K helium refrigeration system for CERN

    CERN. Geneva

    2004-01-01

    The Conseil Europeen pour Ia Recherche Nucleaire (CERN) placed an order for a 1.8 K helium refrigeration system with IHI for the Large Hadron Collider project in 1999. IHI formed a consortium with Linde Kryotechnik AG (Switzerland), which has long experience with helium refrigeration systems. IHI designed and manufactured cold compressors based on leading technologies and expertise for turbo machinery. The cold compressor has the highest efficiency in the world. This paper describes the 1.8 K helium refrigeration system and performance test results at CERN. (5 refs).

  19. Dynamic sparger for measuring low helium concentrations in liquid sodium

    In a novel type of LMFBR steam generator presently being developed, detection of incipient leaks is possible from the appearance of helium in the sodium coolant. A dynamic sparger to detect helium at low concentrations in sodium was designed, built, and tested. Bubble velocities, radii, and mass transfer coefficients were delineated from static mode tests. A successful automatic sodium level control system was included in the demonstration of feasibility of the overall dynamic sparger concept. In the dynamic mode the sparger could detect 0.04 ppB helium in sodium. Sparging efficiency was 0.2 to 0.5 over a workable range of operating conditions

  20. Gas-chromatographic analysis of high-purity helium using a helium detector

    The limits of gas-chromatographic detection of neon, hydrogen, argon, nitrogen, krypton, and methane in helium have been determined using a helium ionization detector under saturation current conditions. The detection limits are restricted by the gas permeability of the detector Teflon body and the injection system. The dependence of extraction of impurity gases by cryogenic adsorption enrichment on their contents and enrichment time has been examined. the relative detection limit can be lowered by preconcentration of 3 x 10-5% for neon and to 4 x 10-7 to 2 x 10-8% for other gases

  1. Helium dilution refrigeration system

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  2. Quantum cavitation in liquid helium

    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.

  3. Quantum cavitation in liquid helium

    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 pressures. Our results are compatible with recent experimental results on 4He. copyright 1996 The American Physical Society

  4. The Hall D solenoid helium refrigeration system at JLab

    Laverdure, Nathaniel A. [JLAB; Creel, Jonathan D. [JLAB; Dixon, Kelly d. [JLAB; Ganni, Venkatarao [JLAB; Martin, Floyd D. [JLAB; Norton, Robert O. [JLAB; Radovic, Sasa [JLAB

    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.

  5. Extreme ultraviolet spectroscopy of helium-hydrogen plasma

    Mills, R; Ray, P [BlackLight Power, Inc., 493 Old Trenton Road, Cranbury, NJ 08512 (United States)

    2003-07-07

    Extreme ultraviolet spectroscopy was recorded on microwave discharges of helium with 2% hydrogen. Novel emission lines were observed with energies of q . 13.6 eV, q = 1, 2, 3, 7, 9, 11, or q . 13.6 eV, q = 4, 6, 8 less 21.2 eV corresponding to inelastic scattering of these photons by helium atoms due to excitation of He (1s{sup 2}) to He (1s{sup 1}2p{sup 1}). The average hydrogen atom temperature was measured to be 180-210 eV versus {approx}3 eV for pure hydrogen. The electron temperature T{sub e} for helium-hydrogen was 30 500 {+-} 5% K compared to 7400{+-}5% K for pure helium. Known explanations for the novel series of spectral lines and extraordinary broadening were ruled out.

  6. The Application and Improvement of Helium Turbines in the EAST Cryogenic System

    The helium cryogenic system supplies supercritical helium cooling capacity at 4.5 K for the superconducting magnets in the EAST superconducting tokamak. Four low-temperature helium turbines are used in the 2 kW helium refrigeration system, and their performance and reliability are critical for the continuous operation of the tokamak. The turbines were made by the Helium Mechanics Company in Russia. The start-up process is very unstable, easily broken, and thus testing and improvements are needed. In this paper, we analyze the structure of the helium turbine, make improvements, and describe the testing process and results of the improved helium turbines. Some of the operational experiences during the start-up process and tests are also presented. (fusion engineering)

  7. Effect of heat treatment on helium trapping in vanadium alloy at high ion implantation fluence

    Helium was implanted into a V-4Ti alloy by using a 5 keV helium ion beam with a flux of 1014 He/cm2 s, and then helium retention was analyzed by a technique of thermal desorption spectroscopy (TDS). The influence of heat treatment on helium trapping was studied by pre-annealing of the samples before ion irradiation. The annealing temperature was 973, 1223 and 1373 K, respectively. Results indicated that pre-annealing treatments did not influence significantly the helium retention and release behavior in vanadium alloy on the present experimental conditions where the helium ion implantation fluence is in the region of 1017-1018 He/cm2, which shows a different tendency from the situation at a low fluence region (1013-1014 He/cm2). The reason could be due to different trap mechanisms of helium at different ion fluences

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

    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...

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

    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. Tensile behavior of helium-implanted and neutron-irradiated

    Vanadium alloys are being considered for use for first-wall and blanket structures in fusion reactors due to their high melting points and low neutron activation. The alloy reported on here, V-15 Cr-5 Ti, was prepared by the Westinghouse Advanced Reactors Division (Heat HSV-307). Since the fusion environment produces helium in all common structural alloys including vanadium, the effect of helium in irradiated alloys was investigated. In a fusion reactor spectrum, ∼ 5 at. ppm He/dpa is expected. Ideally, the helium should be produced concurrently with displacement damage. However, since this is difficult or impossible in vanadium without a source of high-energy neutrons, cyclotron implantation of helium followed by fission reactor irradiation was chosen. By this method, it was hoped to scope qualitatively the effect of helium alone and the synergistic effect of helium in conjunction with neutron irradiation. Results show that: (1) cyclotron injection of 80 at. ppm He has little effect on mechanical properties of V-15 Cr-5 Ti at 700 and 6250C and causes a factor of ∼ 2 reduction in elongation at 4000C; and (2) neutron irradiation to 24 to 32 dpa increases the strength of annealed V-15 Cr-5 Ti by a factor of ∼ 2 and decreases ductility by a factor of about 10

  11. High resolution transient and permanent spectral hole burning in Ce$^{3+}$:Y$_2$SiO$_5$ at liquid helium temperatures

    Karlsson, Jenny; Serrano, Diana; Walther, Andreas; Rippe, Lars; Kröll, Stefan; Goldner, Philippe; Ferrier, Alban

    2016-01-01

    We perform hole burning with a low drift stabilized laser within the zero phonon line of the 4f-5d transition in Ce$^{3+}$:Y$_2$SiO$_5$ at 2K. The narrowest spectral holes appear for small applied magnetic fields and are $6\\pm4$ MHz wide (FWHM). This puts an upper bound on the homogeneous linewidth of the transition to $3\\pm2$ MHz, which is close to lifetime limited. The spin level relaxation time is measured to $72\\pm21$ ms with a magnetic field of 10 mT. A slow permanent hole burning mechanism is observed. If the excitation frequency is not changed the fluorescence intensity is reduced by more than 50$\\%$ after a couple of minutes of continuous excitation. The spectral hole created by the permanent hole burning has a width in the tens of MHz range, which indicates that a trapping mechanism occurs via the 5d-state.

  12. Correlation of Helium Solubility in Liquid Nitrogen

    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.

  13. On the Formation of (Anionic) Excited Helium Dimers in Helium Droplets

    Huber, Stefan E.; Mauracher, Andreas

    2014-01-01

    Metastable atomic and molecular helium anions exhibiting high-spin quartet configurations can be produced in helium droplets via electron impact. Their lifetimes allow detection in mass spectrometric experiments. Formation of atomic helium anions comprises collision-induced excitation of ground state helium and concomitant electron capture. Yet the formation of molecular helium anions in helium droplets has been an unresolved issue. In this work, we explore the interaction of excited helium a...

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

    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)

  15. Photoionization of helium dimers

    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.)

  16. Exotic helium molecules

    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)

  17. Experimental loop for tests of helium cooled high heat flux components at 600 deg C/10 MPa helium inlet

    Helium loop is a tool for tests of divertor design options which meet the requirements for He -cooled fusion DEMO reactor. These tests include: divertor materials and joining technology selection, cooling regimes optimization, mockups thermal cycling for lifetime estimation. It is also possible to use loop in other areas of high temperature helium nuclear technology (blanket/ first wall mock-ups tests, fission helium reactors relevant experiments). Also as results of systematic mock-ups tests it is planned to create data base for validation of gas dynamic and thermal mechanic codes, used for simulation of processes in high heat flux components. Helium loop is able to test mock-ups at nominal helium inlet temperature 600 deg C and pressure 10 MPa. Possible pressure losses in mock-up are up to 0.5 MPa. First stage of such helium loop creation using tank-to-tank principle has finished at Efremov Institute in collaboration with FZK. At this stage stationery flow rate 24 g/s, which is provided by oil-free membrane compressor, was achieved. One more possible loop regime - gas pulses at 50 g/s and duration up to 120 s. Diagnostic system provides measuring more then 40 parameters such as pressure, flow rate and temperature. Mock-up heat loading is provided by e-beam of TSEFEY facility with applied power up to 60 kW at 27 keV beam energy. Results of finger like mock-ups of DEMO helium cooled divertor vertical target testing are presented. At next stage helium loop will be able to reach flow rate of 600 g/s (using helium circulating pump) that will provide heat removal from mock-ups up to 120 kW. The design solutions and R-and-D results of activity at this stage of loop creation are also presented. (author)

  18. Five second helium neutral beam injection using argon-frost cryopumping techniques

    High power helium neutral beams for the heating of tokamak discharges can now be provided for 5 s by using argon cryopumping (of the helium gas) in the beamlines. A system has now been installed to deposit a layer of argon frost on the DIII-D neutral beam cryopanels, between tokamak injection pulses. The layer serves to trap helium on the cryopanels providing sufficient pumping speed for 5 s helium beam extraction. The argon frosting hardware is now present on two of four DIII-D neutral beamlines, allowing injection of up to 6 MW of helium neutral beams per discharge, with pulse lengths of up to 5 s. The argon frosting system is described, along with experimental results demonstrating its effectiveness as a method of economically extending the capabilities of cryogenic pumping panels to allow multi-second helium neutral beam injection

  19. Electronic properties of physisorbed helium

    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.

  20. Electronic properties of physisorbed helium

    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.

  1. Defect production and accumulation under hydrogen and helium ion irradiation

    The 316L stainless steel (316L SS) is a candidate material for the first wall of a fusion reactor, which will be irradiated with 14 MeV neutrons and escaped ions. This will produce helium and hydrogen in the matrix, which come both from the transmutation production and escaped ions of the plasma. The synergistic action of high-energy cascades and helium induces important damage, such as swelling, blistering and helium embrittlement. The hydrogen combines with the radiation defects to produce dense tiny bubbles (or voids) and substitutes for gaseous impurities (such as soluted oxygen, nitrogen, sulfur and phosphorus) which react with other composites Fe, Cr, Ni and Mo to form new phases, such as Cr2O3, (CrFe)2O3, (Fe5C2)28N, (CrMo)N, (Fe2Mo)12H and (FeNi)9S8. These induce mechanical property changes. The hydrogen combined with helium and high energy cascades will induce more serious damage than that of helium alone. To exhibit the synergistic action of helium and hydrogen, the 316L SS specimens were bombarded with helium, hydrogen and mixed ion beam with energy ranging from 27 to 38 keV to a dose of 1017-8 x 1018 ions/cm2 at 573 K. The results indicate that (a) for the helium ion irradiation, the threshold dose for blistering in the energy range 27-100 keV is higher than that for the 1.0 MeV helium ion irradiation. The surface effects play an important role in the blistering. (b) When specimens bombarded with the mixed beam of helium and hydrogen ions of 27 keV reached the same helium dose (6.4 x 1017 He+/cm2), the diameter and density of bubble on surface increase at a ratio of the hydrogen to helium increase. The more hydrogen ions implanted, the easier and more serious the blister is. (c) When the kinetic energy of the mixed beam decreases in the range 10-30 keV, the action of hydrogen ions on the blistering appears more evident. It seems that the hydrogen plays an important role in bubble formation and growth. (orig.)

  2. Shock Experiments on Pre-Compressed Fluid Helium

    We summarize current methods and results for coupling laser-induced shocks into pre-compressed Helium contained in a diamond anvil cell (DAC). We are able to load helium, hydrogen, deuterium, and helium-hydrogen mixtures into a DAC and propagate a laser-generated shock into the pre-compressed sample. This technique has allowed us to measure the Hugoniot for helium at initial densities ranging from 1 to 3.5 times liquid density. We have developed and used a methodology whereby all of our measurements are referenced to crystalline quartz, which allows us to update our results as the properties of quartz are refined in the future. We also report the identification and elimination of severe electro-magnetic pulses (EMP) associated with plasma stagnation associated with ablation in a DAC.

  3. Helium embrittlement of stabilised 20%Cr 25%Ni stainless steels

    The effect of microstructure on helium embrittlement has been studied. Four 20%Cr 25%Ni austenitic alloys with additions of niobium, titanium and boron were irradiated to generate between 2.6 and 25.5 appm helium, predominantly from the boron transmutation. Post-irradiation creep tests indicated that the highest helium levels did not coincide with the greatest embrittlement, owing to a beneficial effect of untransmuted boron. The microstructural distribution of boron was varied markedly by alloying, and heat treatment. However, high levels of grain boundary boron were unimportant in determining unirradiated, and post-irradiation, creep properties. Helium bubbles caused the embrittlement; but were sometimes too small to nucleate creep cavities directly. The embrittlement by sub-critical bubbles, and the hardening by matrix bubbles, are briefly considered. (author)

  4. A pool type liquid helium cryopump

    Design and fabrication details of a pool type Liquid Helium Cryopump are described. It has got a liquid helium capacity of 5 litres and a/ pumping surface area of about 450 sq. cms. Three types of baffles having different geometries are used for radiation shield. Effect on pumping speed for argon, carbon dioxide and nitrogen gas using the baffles is determined at various pressures. The circular array baffle geometry provides the maximum pumping speed. Using circular array type baffle the maximum pumping speed for nitrogen, argon and carbon dioxide are 2700 1/s, 3600 1/s, 2550 1/s respectively at a pressure of 6.0 x 10-4 torr. The ultimate pressure obtained is 3.0 x 10-8 torr. (author)

  5. Diffusion of radiogenic helium in natural uranium oxides

    The issue of nuclear waste management - and especially spent fuel disposal - demands further research on the long-term behavior of helium and its impact on physical changes in UO2 and (U,Pu)O2 matrices subjected to self-irradiation. Helium produced by radioactive decay of the actinides concentrates in the grains or is trapped at the grain boundaries. Various scenarios can be considered, and can have a significant effect on the radionuclide source terms that will be accessible to water after the canisters have been breached. Helium production and matrix damage is generally simulated by external irradiation or with actinide-doped materials. A natural uranium oxide sample was studied to acquire data on the behavior of radiogenic helium and its diffusion under self-irradiation in spent fuel. The sample from the Pen Ar Ran deposit in the Vendee region of France dated at 320 ± 9 million of years was selected for its simple geological history, making it a suitable natural analog of spent fuel under repository conditions during the initial period in a closed system not subject to mass transfer with the surrounding environment. Helium outgassing measured by mass spectrometry to determine the He diffusion coefficients through the ore shows that: (i) a maximum of 5% (2.1% on average) of the helium produced during the last 320 Ma in this natural analog was conserved, (ii) about 33% of the residual helium is occluded in the matrix and vacancy defects (about 10-5 mol g-1) and 67% in bubbles that were analyzed by HRTEM. A similar distribution has been observed in spent fuel and in (U0.9,Pu0.1)O2. The results obtained for the natural Pen Ar Ran sample can be applied by analogy to spent fuel, especially in terms of the apparent solubility limit and the formation, characteristics and behavior of the helium bubbles

  6. Diffusion of radiogenic helium in natural uranium oxides

    Roudil, Daniele [CEA Centre de Marcoule BP 17171 30207, Bat 166, BP 17171, 30207 Bagnols sur Ceze cedex (France)], E-mail: danielle.roudil@cea.fr; Bonhoure, Jessica [Nancy-Universite, G2R, CNRS, CREGU, BP 239, 54506, Vandoeuvre-les-Nancy (France); Pik, Raphael [CRPG-UPR 2300 CNRS-Centre de Recherches Petrographiques et Geochimiques, 54506 Vandoeuvre les Nancy (France); Cuney, Michel [Nancy-Universite, G2R, CNRS, CREGU, BP 239, 54506, Vandoeuvre-les-Nancy (France); Jegou, Christophe [CEA Centre de Marcoule BP 17171 30207, Bat 166, BP 17171, 30207 Bagnols sur Ceze cedex (France); Gauthier-Lafaye, F. [Centre de Geochimie de la Surface, EOST, CNRS/ULP, 1 rue Blessig, 67083 Strasbourg (France)

    2008-08-15

    The issue of nuclear waste management - and especially spent fuel disposal - demands further research on the long-term behavior of helium and its impact on physical changes in UO{sub 2} and (U,Pu)O{sub 2} matrices subjected to self-irradiation. Helium produced by radioactive decay of the actinides concentrates in the grains or is trapped at the grain boundaries. Various scenarios can be considered, and can have a significant effect on the radionuclide source terms that will be accessible to water after the canisters have been breached. Helium production and matrix damage is generally simulated by external irradiation or with actinide-doped materials. A natural uranium oxide sample was studied to acquire data on the behavior of radiogenic helium and its diffusion under self-irradiation in spent fuel. The sample from the Pen Ar Ran deposit in the Vendee region of France dated at 320 {+-} 9 million of years was selected for its simple geological history, making it a suitable natural analog of spent fuel under repository conditions during the initial period in a closed system not subject to mass transfer with the surrounding environment. Helium outgassing measured by mass spectrometry to determine the He diffusion coefficients through the ore shows that: (i) a maximum of 5% (2.1% on average) of the helium produced during the last 320 Ma in this natural analog was conserved, (ii) about 33% of the residual helium is occluded in the matrix and vacancy defects (about 10{sup -5} mol g{sup -1}) and 67% in bubbles that were analyzed by HRTEM. A similar distribution has been observed in spent fuel and in (U{sub 0.9},Pu{sub 0.1})O{sub 2}. The results obtained for the natural Pen Ar Ran sample can be applied by analogy to spent fuel, especially in terms of the apparent solubility limit and the formation, characteristics and behavior of the helium bubbles.

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

    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)

  8. Perspectives on Lunar Helium-3

    Schmitt, Harrison H.

    1999-01-01

    Global demand for energy will likely increase by a factor of six or eight by the mid-point of the 21st Century due to a combination of population increase, new energy intensive technologies, and aspirations for improved standards of living in the less-developed world (1). Lunar helium-3 (3He), with a resource base in the Tranquillitatis titanium-rich lunar maria (2,3) of at least 10,000 tonnes (4), represents one potential energy source to meet this rapidly escalating demand. The energy equivalent value of 3He delivered to operating fusion power plants on Earth would be about 3 billion per tonne relative to today's coal which supplies most of the approximately 90 billion domestic electrical power market (5). These numbers illustrate the magnitude of the business opportunity. The results from the Lunar Prospector neutron spectrometer (6) suggests that 3He also may be concentrated at the lunar poles along with solar wind hydrogen (7). Mining, extraction, processing, and transportation of helium to Earth requires new innovations in engineering but no known new engineering concepts (1). By-products of lunar 3He extraction, largely hydrogen, oxygen, and water, have large potential markets in space and ultimately will add to the economic attractiveness of this business opportunity (5). Inertial electrostatic confinement (IEC) fusion technology appears to be the most attractive and least capital intensive approach to terrestrial fusion power plants (8). Heavy lift launch costs comprise the largest cost uncertainty facing initial business planning, however, many factors, particularly long term production contracts, promise to lower these costs into the range of 1-2000 per kilogram versus about 70,000 per kilogram fully burdened for the Apollo Saturn V rocket (1). A private enterprise approach to developing lunar 3He and terrestrial IEC fusion power would be the most expeditious means of realizing this unique opportunity (9). In spite of the large, long-term potential return on investment, access to capital markets for a lunar 3He and terrestrial fusion power business will require a near-term return on investment, based on early applications of IEC fusion technology (10).

  9. Microcellular Injection Molding Using Helium

    In comparison with conventional foaming process microcellular injection molding process has advantages such as small bubble size, the removal of sink mark, scale reliability, and weight lightening. So microcellular injection molded parts are applied to electrical product and automobile part. Conventional microcellular foaming process used carbon dioxide and nitrogen as a foaming agent. And it has been never researched and applied about microcellular injection molding process using helium. In this paper, we did a microcellular injection molding process using helium based on previous research result and made samples. From this we can certificate the possibility of microcellular continuous process using helium. Helium is lighter and faster in diffusion than carbon dioxide or nitrogen so through this technique, it can be solved the problem such as spray or labeling

  10. Implanting helium into nanocrystalline hydrogen storage alloy

    The possibility of implanting helium into LaNixAly alloy by high energy ball milling is explored. By analyzing the sample after ball milling, it is shown that Helium can be implanted into the material. Helium lies in the interfacial free volume rather than the crystal lattice. The implanted helium has high thermal stability. Quantity of Helium implanted by this method is very little

  11. Hydrogen retention properties of polycrystalline tungsten and helium irradiated tungsten

    The hydrogen retention properties of a polycrystalline tungsten and tungsten irradiated by helium ions with an energy of 5 keV were examined by using an ECR ion irradiation apparatus and a technique of thermal desorption spectroscopy, TDS. The polycrystalline tungsten was irradiated at RT with energetic hydrogen ions, with a flux of 1015 H cm-2 and an energy of 1.7 keV up to a fluence of 5 x 1018 H cm-2. Subsequently, the amount of retained hydrogen was measured by TDS. The heating temperature was increased from RT to 1000 C, and the heating rate was 50 C min-1. Below 1000 C, two distinct hydrogen desorption peaks were observed at 200 C and 400 C. The retained amount of hydrogen was observed to be five times smaller than that of graphite, but the concentration in the implantation layer was comparable with that of graphite. Also, the polycrystalline tungsten was irradiated with 5 keV helium ions up to a fluence of 1.4 x 1018 He cm-2, and then re-irradiated with 1.7 keV hydrogen ions. The amount of retained hydrogen in this later experiment was close to the value in the case without prior helium ion irradiation. However, the amount of hydrogen which desorbed around the low temperature peak, 200 C, was largely enhanced. The desorption amount at 200 C saturated for the helium fluence of more than 5 x 1017 He cm-2. The present data shows that the trapping state of hydrogen is largely changed by the helium ion irradiation. Additionally, 5 keV helium ion irradiation was conducted on a sample pre-implanted with hydrogen ions to simulate a helium ion impact desorption of hydrogen retained in tungsten. The amount of the hydrogen was reduced as much as 50%. (orig.)

  12. Indigenous development of helium liquefier

    Helium Liquefiers/refrigerators have become an essential part of future accelerator developments in India. Apart from designing, systems operating at liquid helium temperature viz. 4.2 K or lower, require additional technical skills to make them work as designed. To get insight in these intricacies, development of helium liquefier was taken up at RRCAT. An indigenous helium liquefier has been developed. 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. Initially, a liquefaction rate of 6 lit/hr was achieved. More than 150 liters of liquid helium was collected during its maiden trial itself, while operating for more than 25 hours continuously. This liquefier has at present crossed a liquefaction rate of 10 lits/hr by further tuning and reducing thermal in-leaks. Based on the experience gained in the present system and validation of design parameters under actual working conditions, a second model is being designed, which will be able to produce about 35 lit/hr of liquid helium. Further work is also being initiated to develop aluminium plate fin heat exchangers for developing helium liquefiers of larger capacity in the range of 100-200 lits/hr. Design, development and performance details of indigenous development of helium liquefier will be presented and ongoing efforts to increase the liquefaction capacity will be discussed. (author)

  13. Helium transport scaling law studies

    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

  14. Numerical study of helium solubility and helium bubble stability in mercury

    Highlights: • Helium solubility in mercury was numerically evaluated and its small value was experimentally confirmed. • Mass-diffusion dominated bubble evolution is simulated and the bubbles were shown to be stable. • The study indicates that small bubble injection into the mercury target for cavitation damage mitigation is feasible. - Abstract: Dispersing small helium bubbles in the liquid mercury target of the high-power spallation neutron sources was proposed to add compressibility to the target made of liquid mercury. The pressure rise from proton beam deposition is reduced due to added compressibility, which in turn mitigates cavitation damage to the target boundary. A gas volume fraction of ∼0.5% with a nominal bubble diameter of ∼30 μm is desired for optimal pressure pulse relaxation at the beam power of >1 MW. Initial gas injection experiments performed in the Oak Ridge National Laboratory encountered difficulty in obtaining the required volume fraction in mercury. Gas dissolution and diffusion in mercury were candidate mechanisms for this behavior. To clarify this, the solubility of helium in mercury is evaluated in this study and compared to the available experimental data. The results indicate that helium has very small solubility in mercury and that the solubility increases with system temperature. Based on the predicted solubility values, bubble size evolution due to mass diffusion is simulated numerically. Mass diffusion induced bubble size evolution does not significantly affect bubble behavior for conditions expected in high power spallation targets

  15. India's first indigenously developed helium liquefier

    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)

  16. Electron scattering from cold metastable helium

    Full text: Electron scattering experiments involving atoms or molecules in excited states are challenging as targets of this type are difficult to prepare in appreciable quantities. However, with the advent of laser cooling and trapping techniques, the possibility to do electron collision studies on such target species now exists. In our laboratory, two related, yet distinct, experiments for electron scattering from metastable helium are being undertaken. The first utilizes a magneto-optical trap (MOT) of 23S Helium atoms as the target for a grand total cross-section measurement. Results of scattering from the 23S and 23P levels of Helium will be presented in the energy range from 5-75eV. The second set of experiments is designed to determine the differential electron scattering cross-section by using the bright beam line as the source of target atom and employing a technique referred to as Metastable Atom Recoil Spectroscopy (Mars). Progress towards the collection of this data will be discussed. Copyright (2005) Australian Institute of Physics

  17. Behavior of weld defects in laser weldment of helium-doped stainless steel

    Helium is generated within neutron-irradiated reactor components and entrapped in the stainless steel components. The repair of the components using conventional GTA welding practices is exceedingly difficult by entrapped helium, because of the initiation of helium bubbles and weld cracking. In this research, the behavior of helium bubble in the austenitic stainless steel weldment was investigated by utilizing stainless steels ion-implanted with helium and then welded by YAG laser apparatus. Helium ion implanting to the sample was carried out using 8MeV implantation apparatus, and the sample was doped with 2.45 x 1019 atoms/m2 dose at 6MeV and then doped with 1 x 1019 atoms/m2 dose at 5MeV. Helium bubbles are present at the bond region, heat-affected zone and weld metal. The increase of laser power causes the growth of helium bubble, toe cracks and cracks along the dendrite cell boundary in the weld metal. The helium bubble phenomena can be reproduced in the weld metal and in the heat-affected zone during repair welding using helium ion implanting technique. (author)

  18. Effect of carbon content and helium gas environment on creep crack growth properties of Ni-26 pct Cr-17 pct W-0.5 pct Mo alloy at 1,273 K

    Nickel-base superalloys are the most promising candidate structural materials for very high temperature use, e.g., as structural components of piping and heat exchangers in high-temperature gas-cooled reactors (HTGRs) and turbine discs in advanced aircraft engines. They can maintain good creep resistance in a very high temperature range of 1,273 K or higher. Here, creep crack growth tests were conducted on Ni-26 pct Cr-17 pct W-0.5 pct Mo alloys with different carbon contents in air and in helium gas environment at 1273 K using the compact-type (CT) specimen, and the effects of carbon content and environment on creep crack growth rate are discussed. Creep crack growth rate da/dt is evaluated by the C* parameters. The da/dt is faster in higher-carbon alloys than in lower-carbon alloys in each environment. This effect of carbon content is attributed to the lower creep ductility due to the increase of fine trans-granular carbides in higher-carbon alloys. The environmental effect on the da/dt vs C* relations is scarcely observed in higher-carbon alloys. In the 0.003 pct C alloy, however, da/dt is much lower in the He gas environment than in air. Carburization is observed ahead of the crack tip in the He gas environment at 1,273 K. The intergranular carbides precipitated due to carburization have a granular configuration and are considered to prevent the grain boundary sliding in lower-carbon alloys

  19. Five second helium neutral beam injection using argon-frost cryopumping techniques

    High power helium neutral beams for the heating of tokamak discharges can now be provided for 5 s by using argon cryopumping (of the helium gas) in the beamlines. The DIII-D neutral beam system has routinely provided up to 20 MW of deuterium neutral beam heating in support of experiments on the DIII-D tokamak. Operation of neutral beams with helium has historically presented a problem in that pulse lengths have been limited to 500 ms due to reliance solely on volume pumping of the helium gas. Helium is not condensed on the cryopanels. A system has now been installed to deposit a layer of argon frost on the DIII-D neutral beam cryopanels, between tokamak injection pulses. The layer serves to trap helium on the cryopanels providing sufficient pumping speed for 5 s helium beam extraction. The argon frosting hardware is now present on two of four DIII-D neutral beamlines, allowing injection of up to 6 MW of helium neutral beams per discharge, with pulse lengths of up to 5 s. The argon frosting system is described, along with experimental results demonstrating its effectiveness as a method of economically extending the capabilities of cryogenic pumping panels to allow multi-second helium neutral beam injection

  20. Swelling and structure of vanadium-base alloys irradiated in the dynamic helium charging experiment

    Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18--31 dpa at 425--600 C in the Dynamic Helium Charging Experiment (DHCE), and the results were compared with those from a non-DHCE in which helium generation and negligible. For specimens irradiated to ∼18-31 dpa at 500--600 with a helium generation rate of 0.4--4.2 appm He/dpa, only a few helium bubbles were observed at the interface of grain matrices and some of the Ti(O,N,C) precipitates, and no microvoids or helium bubbles were observed either in grain matrices or near grain boundaries. Under these conditions, dynamically produced helium atoms seem to be trapped in the grain matrix without significant bubble nucleation or growth, and in accordance with this, density changes from DHCE and non-DHCE (negligible helium generation) were similar for comparable fluence and irradiation temperature. Only for specimens irradiated to ∼31 dpa at 425 C, when helium was generated at a rage of 0.4--0.8 appm helium/dpa, were diffuse helium bubbles observed in limited regions of grain matrices and near ∼15% of the grain boundaries in densities significantly lower than those in the extensive coalescences of helium bubbles typical of other alloys irradiated in tritium-trick experiments. Density changes of specimens irradiated at 425 C in the DHCE were significantly higher than those from non-DHCE irradiation. Microstructural evolution in V-4Cr-4Ti was similar for DHCE and non-DHCE except for helium bubble number density and distribution. As in non-DHCE, the irradiation-induced precipitation of ultrafine Ti5Si3 was observed for DHCE at >500 C but not at 425 C

  1. Increase in the work function of W/WO3 by helium plasma irradiation

    Kajita, Shin; Ohta, Akio; Ishida, Tomoya; Makihara, Katsunori; Yoshida, Tomoko; Ohno, Noriyasu

    2015-12-01

    Helium plasma irradiation to tungsten leads to formation of helium clusters, helium bubbles, and fiberform nanostructures near the surface. In this study, tungsten samples exposed to helium plasmas are analyzed by X-ray photoelectron spectroscopy in detail. The W 4f spectra and valence band spectra show chemical composition and electronic state of the surface. It was found that significant differences were not identified on the electronic state between the helium plasma irradiated and pristine samples when the degree of oxidization was the same level. From a low kinetic energy cut-off of X-ray photoelectron spectrum, the work function of the samples was measured. It was found that helium plasma irradiation increased the work function by approximately 0.5 eV when WO3/W was higher than unity. The possible mechanism to arise the difference in the work function is discussed.

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

    Verma, Kuldeep; Antia, H M; Basu, Sarbani; Mazumdar, Anwesh; Monteiro, Mario J P F G; Appourchaux, Thierry; Chaplin, William J; Garcia, Rafael A; Metcalfe, Travis S

    2014-01-01

    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 years 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 0.231 to 0.251 and that of 16 Cyg B lies in the range 0.218 to 0.266.

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

    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.

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

    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.

  5. Gas chromatographic determination of helium in neutron-irradiated beryllium oxide.

    Hibbits, J O

    1966-01-01

    A method has been developed for the determination of helium produced during neutron irradiation of beryllium oxide ((9)Be + n --> (8)Be + 2n; (8)Be --> 2(4)He). The sample is dissolved by refluxing in a sulphuric acid-phosphoric acid mixture in an argon atmosphere. After the sample has completely dissolved, the released helium is transferred to a gas sampling bulb by means of a Toepler pump. An activated charcoal trap cooled by liquid nitrogen is used to separate helium from argon. The helium is determined by gas chromatography using a 20-ft Linde 5A molecular sieve column. PMID:18959858

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

    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, α) 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

  7. COSMIC-RAY HELIUM HARDENING

    Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 1015eV, and (2) all CR spectra become hard at ?>1011eV nucleon-1. We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at ?100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with ?106 K. Our model predicts hard and concave spectra for heavier CR elements.

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

    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.

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

    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.

  10. Fermilab central helium liquefier operations

    This chapter discusses the use of liquid helium to cool the Fermilab superconducting accelerator. Liquid from the Central Helium Liquefier (CHL) is transported in a six kilometer circular transfer line and each satellite withdraws the amount required to boost its refrigeration capacity to the necessary level. Topics considered include the compressor, the heater, the control system, gas storage, liquid storage, the nitrogen reliquefier, gas purification, initial and early operation, and recent operation. The liquid helium is warmed to near ambient temperature in the satellite heat exchangers. The satellite compressors return the excess inventory to the CHL via a 20 bar gas header. This gas is injected into the high pressure supply to the cold box. Some turbine instabilities have been experienced, including the destruction of a turbine during the initial start-up

  11. Studying the structure and mechanical properties of the steel-0Kh16N15M3B irradiated with helium ions

    The effect of helium on the mechanical properties and structure of the 0Kh16N15M3B-stainless steel has been studied depending on the testing temperature, deforma,.ion rate, grain size, and helium concentration. Samples for destructive testing have been uniformly (volumetrically) saturated with helium up to 10-5 to 10-2 at. % at a cyclotΩn by irradiation with a 36 MeV helium ion beam. The helium ion-implanted material exhibits embrittlement at temperatures above 700 deg C, the embrittlement growing with the helium concentration increase

  12. Magnetically insulated helium ion diode

    Wessel, F.J.; Heidbrink, W.W.; Drum, S.; Hoang, K.; Layton, P. (Physics Department, University of California, Irvine, California 92717 (US))

    1990-01-01

    A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode (J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. {bold 63}, 1872 (1988)), but with modifications to accomodate higher voltages ({lt}1 MeV) and operation in helium. The diode is designed to yield current densities approaching 200 A/cm{sup 2} one meter downstream from the source; in our first test of the new source, a helium beam was obtained.

  13. Diffusion and retention of helium in titanium carbide

    The knowledge of helium migration in TiC is an important issue due to its possible use as fuel coating in fission reactors and as first wall material coating in fusion reactors. Helium release measurements and diffusion coefficient calculations of helium in polycrystalline TiC have been carried out in the temperature range (10001600 C) for the time period of 2 h. Polished bars of TiC were implanted with 3 MeV 3He+ ions in normal incidence at a dose of 5 1020 at./m2 at room temperature. Helium depth profile was measured at each step using the 3He(d, p0)4He nuclear reaction by varying the incident deuteron energy from 900 to 1800 keV. Effective diffusion coefficients vary from 4.20 10?18 to 2.59 10?17 m2 s?1 and activation energy values obtained are in the range 0.82.5 eV. Due to scarce availability of stoichiometric TiC, challenges in this study came from native vacancies present in the samples. The helium distribution and its release were affected by the presence of grain boundaries. He is considered to undergo two distinct populations into the sample and different values of diffusion coefficient have been determined for each population

  14. Energy loss of helium ions in zinc

    The energy loss of helium ions in zinc has been measured in the energy range from 37.5 to 1750 keV/amu using the transmission technique and the Rutherford backscattering method. In addition, calculations using the extended Friedel sum rule, the unitary convolution approximation, and the local plasma approximation have been performed. The contributions of the inner-shell and valence electrons to the total energy loss are separately evaluated. The measurements and calculations are in good agreement over an extended range of energies, and both of them yield stopping values higher than those provided by SRIM 2003

  15. Linde standard helium plant of medium capacity

    The unit is designed to deliver up to 70 l/h of liquid helium (LHe) without precooling by liquid nitrogen (LN2), up to 105 l/h with LN2 precooling, or up to 210 W cryo-refrigeration output at 4.5 K. Its principal components are an oil-flooded screw compressor, gas-bearing expansion turbines, vacuum-brazed aluminium plate-fin heat exchangers, an automatic feed gas purifier, and a process control system. Descriptions are given of the process layout, the main system components, and operation of the unit. (orig.)

  16. Primary population of antiprotonic helium states

    Révai, J.; Shevchenko, N.V.(Nuclear Physics Institute, Řež, 25068, Czech Republic)

    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.

  17. Helium retention properties of plasma facing materials

    In a fusion reactor, the continuous removal of helium from the core plasma is needed in order to sustain the ignition condition. For this purpose, it has been proposed to place helium selective pumping metals, which can trap more helium than hydrogen, in the vicinity of the divertor. In this study, the helium and hydrogen trapping properties of nickel, tungsten, molybdenum, SS 304 and Inconel 625 were examined. Namely, the dependencies of irradiation temperature on the amount of trapped helium and hydrogen were obtained by thermal desorption spectroscopy (TDS), after helium or hydrogen plasma irradiation. In those metals, nickel showed the most suitable selective pumping capability. Nickel had the helium selective pumping property above 100 C. The maximum amount of trapped helium was (2-3) x 1016 He/cm2 at an irradiation temperature of 200 C and 600 C. The optimum temperature becomes about 600 C when nickel is used for a selective pumping material. (orig.)

  18. Pierre Gorce working on a helium pump.

    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

  19. A study of the magnetic helium variable emission-line star HD 125823

    Hubrig, S; Gonzalez, F; Wolff, B; Savanov, I

    2007-01-01

    The 5.9 M_sun star HD 125823 is a striking helium variable with a period of 8.82 d, ranging in helium spectral type from He-strong B2 to He-weak B8. For the first time we present here observational evidence for the appearance of emission lines of Mn and Fe in a variable magnetic star.

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

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

    2016-01-01

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

  1. The effect of primordial hydrogen/helium fractionation on the solar neutrino flux

    Wheeler, J. C.; Cameron, A. G. W.

    1975-01-01

    If hydrogen and helium are immiscible below some critical temperature, gravitational separation could occur in the proto-sun, resulting in a nearly pure helium core and a nearly pure hydrogen shell. We have constructed solar models according to this scenario and find the neutrino flux reduced to 1.5-3 SNU.

  2. Conduction of electrons on liquid helium along channels produced by multi-layer microfabrication

    We demonstrate the conduction of free electrons along an array of microchannels of liquid helium, 30 ?m wide, 1 ?m deep and 1.5 mm long, held by surface tension between conducting ribs. No perpendicular conduction occurs until the bulk helium level rises above the channels. (orig.)

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

    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

  4. Direct current insulation breakdown characteristics of supercritical helium

    The insulation breakdown characteristics of helium around a pseudo-critical line were experimentally studied, and their correspondence with the other physical characteristics was obtained. The breakdown voltage was measured in the following ranges of parameters; temperature 4.6 - 8.8 K, pressure 2.5 - 11 atm, density 20 - 146 mg/cm3. Voltage was raised at the rate of 1 kV/sec. The tested electrodes were a stainless steel plate vs. a tangsten needle (1mm diameter, 30 deg vertical angle) or a stainless steel ball (25 mm diameter) vs. the plate. The measured D.C. breakdown voltage was plotted in relation to the helium density. The effect of the electrode polarity was also investigated. The breakdown characteristics in the regions of pseudo-liquid, pseudo-gas, and across the pseudo-critical line are discussed, based on the experimental data with the needle having negative polarity. The effects of electrode distance and temperature were also investigated. The following major findings were obtained from the present study. (1) The breakdown characteristics changed at the pseudo-critical line, (2) The breakdown voltage in the pseudo-liquid region coincided with that of liquid helium. (3) It was suggested that gas bubbles did not play an important role also in the breakdown mechanism of liquid helium, because there can not be bubbles in pseudo-liquid supercritical helium. (4) In the case of steel ball and plate electrodes, the breakdown voltage of the pseudo-liquid helium did not coincide with that of liquid helium, but a tendency of changing toward coincidence was observed when the surfaces of the electrodes were roughened. (Aoki, K.)

  5. Determination of low levels of krypton in helium by gas chromatography

    Krypton-helium mixture was used as an adsorbate for surface area measurement--. The surface area measurements depend on the accuracy with which the krypton concentration is known. Generally gas tanks supplied by Union Carbide provide a nominal value of 0.1% krypton in helium. The surface area measurements require, however, that the krypton concentraion be known to +- 0.001% or better. A standard plot of krypton volume in microliters vs the area under the curve as measured by a planimeter using the helium detector and Molecular Sieve 5A column was obtained. Results with a thermal conductivity detector using Molecular Sieve 5A and Carbon Molecular Sieve are also given. Low levels of krypton in helium can be measured with precision using either a helium or a thermal conductivity detector with Molecular Sieve 5A or Carbon Molecular Sieve columns. 2 figures, 1 table

  6. Atomic spectra in a helium bubble

    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 describing spectral perturb...

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

    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

  8. Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone

    Lowenstern, Jacob B.; Evans, William C.; Bergfeld, D.; Hunt, Andrew G.

    2014-01-01

    Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents1. The hydrothermal system at Yellowstone National Park is famous for its high helium-3/helium-4 isotope ratio, commonly cited as evidence for a deep mantle source for the Yellowstone hotspot2. However, much of the helium emitted from this region is actually radiogenic helium-4 produced within the crust by α-decay of uranium and thorium. Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Our results demonstrate the extremes in variability of crustal helium efflux on geologic timescales and imply crustal-scale open-system behaviour of helium in tectonically and magmatically active regions.

  9. Thermal annealing behaviour and defect evolution of helium in fully stabilised zirconia

    Helium implantations in fully stabilised zirconia have been performed with 30 keV ions with high doses (5.1 x 1016 and 2.6 x 1016 cm-2) and low doses (6.3 x 1015 and 1.7 x 1015 cm-2). The retained amount of helium and depth profiles have been monitored with neutron depth profiling and the damage distribution with positron beam analysis (PBA) after several annealing steps. The temperature dependent helium release was investigated by thermal helium desorption spectrometry. In the low dose samples, helium is released through diffusion as seen by a broadening of the helium distribution peak. PBA, performed with a two-layer model, shows shrinkage of the damage layer during annealing. For the high dose samples the helium peak does not broaden after annealing. Helium is retained up to high temperatures which is ascribed to bubble formation during thermal annealing. Fitting of the PBA results to a three-layer model shows that the ion implanted layer gets narrower after annealing at 600 K, up to 1000 K the S-parameter is increasing because helium is released from the bubbles, whereby vacancy clusters are left behind

  10. 21 CFR 582.1355 - Helium.

    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...

  11. Helium compounds and solidification of α particles

    Helium is not rare gas in the universe, and also not inert gas, for there are Helium com- pounds, α-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)

  12. 21 CFR 184.1355 - Helium.

    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...

  13. Helium distribution functions in tokamak plasmas

    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)

  14. Look at helium--present and future

    Garwin, L.

    1969-04-01

    Natural gas is the only commercial source of helium. All natural gas containing helium also contains nitrogen. Processors go into deep cryogenic temperatures and high pressures to liquefy the nitrogen and recover helium gas. Tabular data show the spectacular growth of helium, particularly from about 1960 on. The prime function the U.S. Government now performs is the conservation of helium. The government purchases helium in crude form and it is stored in the government reservoir at Cliffside Field near Amarillo, Tex. In addition, the government continues to operate 3 plants for the production of Grade A helium for government agencies and the commercial market. Tabular data also show a list of nongovernment plants now in operation or soon to be in operation. The extraction of helium from natural gas is described together with a flow chart for a U.S. Bureau of Mines helium plant. A typical cycle for crude helium purification is shown. The coexistence of helium and hydrocarbons in a geologic trap is regarded as a matter of coincidence. It is believed that the helium was generated at one place, the hydrocarbons at another, and both happened to migrate to the same point of accumulation.

  15. Why Helium Ends in "-Ium"

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

    2004-01-01

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

  16. Liquid helium level measurement system

    The Liquid Helium level measurement system at the PLF, Mumbai has been recently upgraded. Monitoring liquid helium levels is crucial for steady operation of superconducting Linac booster. A Superconducting wire (NbTi) based sensor (American Magnetic make) is used to measure the liquid helium level. Resistance of the sensor changes with the liquid level and the change in resistance is measured using a four wire readout. The Electronics hardware is developed around Silicon lab module C8051F020, which has a 12 bit ADC on board. The sensor is excited with 80 mA constant current and the voltage across the sensor is measured using 12 bit ADC and processed further to get resistance. The measured resistance is converted to fractional level (0 to 100 %) and can be displayed on the LCD panel of the local unit as well as on the remote PC through serial communication. Each unit is capable of reading upto four level sensors. One of the important features of this measurement system is the auto calibration with a single button for all the four level sensors. Two control stations are designed, developed and successfully installed to monitor helium levels in all eight cryostats of the Linac. (author)

  17. Cryopumping of hydrogen and helium

    Results obtained in numerous tests on small (approx. 1000 l/S) and large (approx. 105 l/S) cryopumps cooled to 4.20K by LHe or between 10 to 200K by closed-cycle helium refrigerator are summarized. Then, measurements of the compound cryopump, designed to work on Tokamaks to handle the exhaust gases from the Torus are presented

  18. Semi-Analytical Analysis of Helium Synthesis in Brane Cosmology

    Fabris, J C

    2003-01-01

    The problem of primordial nucleosynthesis of helium in brane cosmology is studied using a semi-analytical method, where the Fermi-Dirac statistic is ignored. This semi-analytical method agrees with a more complete numerical calculation with a precision of order of 10% or better. The quadratic term for the matter density is the only source considered in the modified Einstein equations predicted by the brane configuration. This hypothesis is justified a posteriori. An agreement between theoretical and observational values for the helium abundance is obtained if the fundamental mass scale in five dimensions is of the order of $M \\sim 5\\times10^3 GeV$.

  19. One-dimensional electron system over liquid helium

    Kovdrya, Yu. Z.; Nikolaenko, V. A.; Gladchenko, S. P.

    2000-07-01

    A system close to a one-dimensional (1D) electron system on superfluid helium is realized in the experiments. A profiled substrate with a small dielectric constant is used to create a set of parallel channels on the surface of liquid helium. The mobility of carriers was measured in this system in the temperature range 0.5-1.8 K. For clean substrates the electron mobility increases with decreasing temperature and reaches high values at low temperatures. The results of experiments are found to be in a good agreement with the existing theory.

  20. Helium refrigeration systems for super-conducting accelerators

    Ganni, V.

    2015-12-01

    Many of the present day accelerators are based on superconducting technology which requires 4.5-K or 2-K helium refrigeration systems. These systems utilize superconducting radio frequency (SRF) cavities and/or superconducting magnets which are packaged into vacuum vessels known as cryo-modules (CM's). Many of the present day accelerators are optimized to operate primarily at around 2-K, requiring specialized helium refrigeration systems which are cost intensive to produce and to operate. Some of the cryogenic refrigeration system design considerations for these challenging applications are discussed.

  1. Cavitation Density of Superfluid Helium-4 around 1 K

    Qu, An; Trimeche, Azer; Dupont-Roc, Jacques; Grucker, Jules; Jacquier, Philippe

    2015-01-01

    Using an optical interferomertric method, the homogeneous cavitation density of superfluid helium at $T=0.96\\,$K is measured and found to be $\\rho_{cav}=0.1338\\pm0.0002\\rm\\,g.cm^{-3}$. A well established equation of state for liquid helium at negative pressures converts this to the cavitation pressure $P_{cav}=-5.1\\pm0.1\\,$bar. This cavitation pressure is consistent with a model taking into account the presence of quantized vortices, but disagrees with previously published experimental values...

  2. A design for a pinhole scanning helium microscope

    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

  3. Trapping and release of helium in tungsten

    Lhuillier, Pierre-Emile; Belhabib, Taieb; Desgardin, Pierre; Courtois, Blandine; Sauvage, Thierry; Barthe, Marie-France; Thomann, Anne-Lise; 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...

  4. Effect of helium on tensile properties of vanadium alloys

    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.

  5. Precise measurement of helium isotopes in terrestrial gases

    Helium isotope ratios of terrestrial natural gas samples were measured using a high-precision mass spectrometer and an ultrahigh-vacuum purification line. The line is equipped with a charcoal trap held at 40K using a helium expansion refrigerating machine. To avoid interference, Ne was completely separated from He by the trap before the gas was admitted to the mass spectrometer. Ion beams of 3He and 4He were measured at the same time by a double collector system. A resolving power of about 550 at the 5% level of the peak height was attained for the complete separation of 3He ions from those of HD and H3. Precision and reproducibility of the helium isotope ratio were less than 1%, examined by repeated measurements of an air standard. Accuracy of the ratio was checked by comparing observed data with reports in the literature. (author)

  6. Mott and helium polarimetry of a spin polarized electron source

    Humphrey, I.; Ranganathaiah, C.; Robins, J.L.; Williams, J.F.; Anderson, R.A.; Macklin, W.C. (Western Australia Univ., Nedlands, WA (Australia). Dept. of Physics)

    1992-09-01

    An absolute determination of the electron spin polarization of a GaAs photoemission source was made using the method of helium polarimetry. Measurements of the source polarization were also made using a Mott spin polarization analyser. We report an electron beam polarization of (25.5[+-]1)% and an effective Sherman function of 0.26[+-]0.01 for the Mott detector at 31.8[+-]0.6 keV incident electron energy. The Sherman function is also presented for a number of incident energies between 10 keV and 37 keV. A complete set of Stoke's parameters is reported for the 3[sup 3]P-2[sup 3]S (3889 A) helium line. The characteristics of the source, Mott detector and helium polarimeter are discussed in detail. (author).

  7. Improvement of helium characteristics using argon in cylindrical ion source

    the discharge characteristics of pure helium gas were measured at different pressures in the range of 10-4 torr. in order o improve its characteristics, argon gas was added . different percentages of argon gas ,1%,2%,3%,4%,5%,10% and 20% were used at constant values of pressures . Measurements of the efficiency of the cylindrical ion source in case of adding different percentages of argon gas to pure helium gas were made . an optimum value of the output ion beam current was obtained when 2% argon gas was added to pure helium gas . an output ion beam current of 105 μA was obtained at a pressure of 7X10-4 torr inside the vacuum chamber and discharge current of 0.6 m A

  8. Kapitza resistance between liquid and solid helium

    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

  9. LRO-LAMP Observations of Lunar Exospheric Helium

    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.

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

    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)

  11. Helium solubility in imperfect ionic crystals

    In the context of the intended use of helium as a coolant in high temperature gas cooled reactors a study is undertaken into helium interaction with crystals at the stage preceding the process of helium clusters formation. Experimental and theoretical investigations of helium solubility in imperfect ionic crystals CaF2, SrF2, KBr are carried out along with the degassing kinetics in the temperature range of 500-1200 K. An analysis is made for possible mechanisms of the occurrence of observed oscillations in helium solubility at temperature variations. The solution heat for helium atoms in cation vacancies and the energy of impurity-vacancy cluster dissociation are calculated. The reason for a catastrophic increase of dissolved helium concentration with saturation pressure is discussed

  12. HeREF-2003 : Helium Refrigeration Techniques

    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 ...

  13. HeREF-2003: Helium Refrigeration Techniques

    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...

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

    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)

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

    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 ~510-9 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 (~421 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

  16. Internally-cooled cabled superconductors cooled with helium II

    Niobium-titanium superconductors maintained at sublambda temperatures provide an alternative to helium cooled niobium-3-tin superconductors operating in the 4.2 to 5 K temperature range. The subject paper examines the replacement of supercritical HeI with subcooled HeII in a slightly modified MIT-12 T test coil. Both steady-state and transient heat loads are considered

  17. Altering blood flow does not reveal differences between nitrogen and helium kinetics in brain or in skeletal miracle in sheep.

    Doolette, David J; Upton, Richard N; Grant, Cliff

    2015-03-01

    In underwater diving, decompression schedules are based on compartmental models of nitrogen and helium tissue kinetics. However, these models are not based on direct measurements of nitrogen and helium kinetics. In isoflurane-anesthetized sheep, nitrogen and helium kinetics in the hind limb (n = 5) and brain (n = 5) were determined during helium-oxygen breathing and after return to nitrogen-oxygen breathing. Nitrogen and helium concentrations in arterial, femoral vein, and sagittal sinus blood samples were determined using headspace gas chromatography, and venous blood flows were monitored continuously using ultrasonic Doppler. The experiment was repeated at different states of hind limb blood flow and cerebral blood flow. Using arterial blood gas concentrations and blood flows as input, parameters and model selection criteria of various compartmental models of hind limb and brain were estimated by fitting to the observed venous gas concentrations. In both the hind limb and brain, nitrogen and helium kinetics were best fit by models with multiexponential kinetics. In the brain, there were no differences in nitrogen and helium kinetics. Hind limb models fit separately to the two gases indicated that nitrogen kinetics were slightly faster than helium, but models with the same kinetics for both gases fit the data well. In the hind limb and brain, the blood:tissue exchange of nitrogen is similar to that of helium. On the basis of these results, it is inappropriate to assign substantially different time constants for nitrogen and helium in all compartments in decompression algorithms. PMID:25525213

  18. Helium atom scattering from surfaces

    1992-01-01

    High resolution helium atom scattering can be applied to study a number of interesting properties of solid surfaces with great sensitivity and accuracy. This book treats in detail experimental and theoretical aspects ofthis method as well as all current applications in surface science. The individual chapters - all written by experts in the field - are devoted to the investigation of surface structure, defect shapes and concentrations, the interaction potential, collective and localized surface vibrations at low energies, phase transitions and surface diffusion. Over the past decade helium atom scattering has gained widespread recognitionwithin the surface science community. Points in its favour are comprehensiveunderstanding of the scattering theory and the availability of well-tested approximation to the rigorous theory. This book will be invaluable to surface scientists wishing to make an informed judgement on the actual and potential capabilities of this technique and its results.

  19. Confined helium on Lagrange meshes

    Baye, Daniel

    2015-01-01

    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.

  20. Superfluid helium leak sealant study

    Vorreiter, J. W.

    1981-01-01

    Twenty-one leak specimens were fabricated in the ends of stainless steel and aluminum tubes. Eighteen of these tubes were coated with a copolymer material to seal the leak. The other three specimens were left uncoated and served as control specimens. All 21 tubes were cold shocked in liquid helium 50 times and then the leak rate was measured while the tubes were submerged in superfluid helium at 1.7 K. During the cold shocks two of the coated specimens were mechanically damaged and eliminated from the test program. Of the remaining 16 coated specimens one suffered a total coating failure and resulting high leak rate. Another three of the coated specimens suffered partial coating failures. The leak rates of the uncoated specimens were also measured and reported. The significance of various leak rates is discussed in view of the infrared astronomical satellite (IRAS) Dewar performance.

  1. Vanadium alloys with improved resistance to helium embrittlement

    A series of experimental vanadium alloys have been designed with small MC-type carbides in their microstructures to trap helium produced during neutron irradiation, thereby reducing helium embrittlement. The tensile properties and fabricability of the alloys were strongly influenced by the amounts of MC-forming-elements, especially carbon. Alloys with 0.05 and 0.10 wt % carbon exhibited slightly lower yield strengths at 420 to 600 degree C than vanadium alloys such as V-5Cr-5Ti, Vanstar-7, V-3Ti-1Si, and V-15Cr-5Ti. However, this characteristic may actually be an asset from the standpoint of resistance to irradiation hardening. After implantation with 300 appm 3He, both the V-Ti-C and V-Ti-Zr-C alloys exhibited less ductility losses at 600 degree C than the other vanadium alloys tested under comparable conditions. Examination of the experimental alloy microstructures by AEM showed that the small MC-type carbides did, in fact, trap helium and that they were responsible for the increased resistance to helium embrittlement of these alloys. 16 refs., 12 figs., 2 tabs

  2. Magnetically insulated helium ion diode

    A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode [J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. 63, 1872 (1988)], but with modifications to accomodate higher voltages (2 one meter downstream from the source; in our first test of the new source, a helium beam was obtained

  3. Nonsequential Double Ionization of Helium

    Watson, J.; Sanpera, A.; Burnett, K. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Lappas, D.; Knight, P. [Optics Section, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2BZ (United Kingdom)

    1997-03-01

    Electron correlation effects in strong laser fields are investigated by using a simplified two electron model to calculate the double ionization rate in helium. In our model we make a correction to the single active electron approximation by including the effect of the outer electron on the inner one through a time-dependent potential. Using this approach we are able to investigate the nonsequential double ionization observed in recent experiments. {copyright} {ital 1997} {ital The American Physical Society}

  4. Acoustic streaming in superfluid helium

    Quantitative measurements of acoustic streaming velocity in liquid helium as a function of sound intensity (up to the cavitation threshold), frequency (1, 3, and 10 MHz), and temperature (1.43 K< or =T< or =2.19 K) are reported. A transition to superfluid turbulence, several flow regions and flow fluctuations are observed. Comparison with the predictions of the second-order Khalatnikov two- fluid hydrodynamic equations indicates good functional and quantitative agreement

  5. Effect of helium on separation performance of cryogenic distillation column cascade for fusion reactor

    The effect of helium in the feed stream on separation performance of the cryogenic distillation columns was discussed in a probable case. The column cascade at Los Alamos National Laboratory was chosen in the present study. The new data for solubility of helium in liquid hydrogen isotopes was used in the present study. Column (2) is mainly affected by the presence of helium in the fuel stream. If the helium percentage in the feed stream is 1%, the column performance can be assured by increasing the condenser load: a larger inner diameter of the column; larger flow rate of the refrigerant gas; and larger heat transfer area at the condenser should be considered. If the percentage is 5%, both the column pressure and condenser load must be doubled in the steady-state operation. These results qualitatively agreed with the simulation results by Kinoshita in which the old data for solubility of helium were used. (author)

  6. Development of a process for recovery of helium from monazite sand

    The pilot plant studies made to develop a process for helium recovery from monazite and its purification are described. The steps in the developed process are : (1) liberation of helium from monazite processing plant during caustic digestion of the ore, (2) collection of the crude gas (30-50% helium) after removal of condensables and drying, (3) removal of hydrogen by catalytic combination with oxygen to form water vapour using de-oxo catalyst bed, (4) removal of oxygen and nitrogen by condensation (helium content is raised 98% in this step) and (5) passing the gas over activated charcoal cooled by liquid nitrogen. In the final step, 99.995% pure helium is obtained. Trials have shown that the process is feasible. (M.G.B.)

  7. Commissioning result of the KSTAR helium refrigeration system

    To keep the SuperConducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as Thermal Shields (TS), magnet structures, SC Bus-Lines (BL), and Current Leads (CL) must be maintained at their respective cryogenic temperatures. A Helium Refrigeration System (HRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without Liquid Nitrogen (LN2) pre-cooling has been manufactured and installed. The main components of the KSTAR Helium Refrigeration System (HRS) can be classified into the Warm Compression System (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of Cold Box (C/B) and Distribution Box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated

  8. Helium Contamination Through Polymeric Walls

    Gabal, M.; Lozano, M. P.; Oca, A.; Pina, M. P.; Sesé, J.; Rillo, C.

    The concentration of impurities in helium gas is an important parameter for a recovery andliquefaction plant. A low level of impurities is necessary to maintain an optimum liquefaction rate inany kind of liquefier. The main origin of the impurities is the air contamination that enters into the helium mainstream at some point in the recovery cycle. In this work we have: i) identifiedthe main sources forimpurities in anexperimental helium recovery plant, ii) quantified the contamination rate and iii) proposeda mitigation strategy.An analysis of the He impurities composition revealsa nitrogen/oxygenratio different to the one existing in air. This observation is in accordance with the permeability values for nitrogenand oxygen through the polymer materials used in the plant.Experimental on line measurements for oxygen content in the He mainstream with sensitivity below 1 ppm, have been performed after recirculation through metal and polymericpipelines, respectively, to validate our hypothesis. In addition, the dependence of the impurities concentration with the Heretention time in the recovery gasbag has beenevaluated. Finally some operational recommendations are given for practical applications.

  9. Trapping and release of helium in tungsten

    Lhuillier, P.E.; Belhabib, T.; Desgardin, P.; Courtois, B.; Sauvage, T. [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Universite d' Orleans, Faculte des Sciences, Avenue du Parc Floral, BP 6749, 45 067 Orleans Cedex 2 (France); Barthe, M.F., E-mail: marie-France.barthe@cnrs-orleans.fr [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orleans Cedex 2 (France); Universite d' Orleans, Faculte des Sciences, Avenue du Parc Floral, BP 6749, 45 067 Orleans Cedex 2 (France); Thomann, A.L.; Brault, P.; Tessier, Y. [GREMI Polytech' Orleans, 14 rue D' Issoudun, BP 6744, 45 067 Orleans Cedex 2 (France)

    2011-09-01

    The behavior of tungsten under irradiation and helium implantation is a major stake of the material-related 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 function of temperature by using nuclear reaction analysis. The migration propensity of helium was correlated with the release rate of helium after annealing at a given temperature. In addition, the helium trapping sites and evolution with post-implantation annealing was investigated using Doppler-Broadening Positron Annihilation Spectroscopy. It has been shown that the release, and so the migration, of helium is guided by the concentration of implantation-induced defects and the nature of the helium traps created during the implantation.

  10. Absolute calibration of TFTR helium proportional counters

    The TFTR helium proportional counters are located in the central five (5) channels of the TFTR multichannel neutron collimator. These detectors were absolutely calibrated using a 14 MeV neutron generator positioned at the horizontal midplane of the TFTR vacuum vessel. The neutron generator position was scanned in centimeter steps to determine the collimator aperture width to 14 MeV neutrons and the absolute sensitivity of each channel. Neutron profiles were measured for TFTR plasmas with time resolution between 5 msec and 50 msec depending upon count rates. The He detectors were used to measure the burnup of 1 MeV tritons in deuterium plasmas, the transport of tritium in trace tritium experiments, and the residual tritium levels in plasmas following 50:50 DT experiments

  11. Dielectric Properties of Cryogenic Gas Mixtures Containing Helium, Neon, and Hydrogen

    Graber, L.; Kim, W. J.; Cheetham, P.; Kim, C. H.; Rodrigo, H.; Pamidi, S. V.

    2015-12-01

    Past efforts of cooling high temperature superconducting (HTS) power cables by gaseous cryogens focused exclusively on helium. The limited dielectric strength of helium gas necessitated alternatives that could be used in the temperature range suitable for HTS power applications. This paper presents the benefits of gas mixtures containing helium with small concentrations of hydrogen or neon to mitigate the limited dielectric strength of pure helium gas. The expectation was that such gas mixtures could improve dielectric characteristics while maintaining the thermal, non-flammable and non-corrosive properties of pure helium gas. The AC breakdown voltage of helium gas mixtures containing 4 mol% neon or 4 mol% hydrogen respectively have been measured and compared to those of pure helium and pure neon. All measurements were performed at 77 K at gas pressure levels between 0.5 and 2.0 MPa. While the 4 mol% neon mixture did not result in any improvement over pure helium, the 4 mol% hydrogen mixture resulted in 80% higher breakdown strength. This is expected to enable higher operating voltages for gas cooled HTS power devices.

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

    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)

  13. Helium effects on microstructural change in RAFM steel under irradiation: Reaction rate theory modeling

    Reaction rate theory analysis has been conducted to investigate helium effects on the formation kinetics of interstitial type dislocation loops (I-loops) and helium bubbles in reduced-activation-ferritic/martensitic steel during irradiation, by focusing on the nucleation and growth processes of the defect clusters. The rate theory model employs the size and chemical composition dependence of thermal dissociation of point defects from defect clusters. In the calculations, the temperature and the production rate of Frenkel pairs are fixed to be T = 723 K and PV = 10−6 dpa/s, respectively. And then, only the production rate of helium atoms was changed into the following three cases: PHe = 0, 10−7 and 10−5 appm He/s. The calculation results show that helium effect on I-loop formation quite differs from that on bubble formation. As to I-loops, the loop formation hardly depends on the existence of helium, where the number density of I-loops is almost the same for the three cases of PHe. This is because helium atoms trapped in vacancies are easily emitted into the matrix due to the recombination between the vacancies and SIAs, which induces no pronounced increase or decrease of vacancies and SIAs in the matrix, leading to no remarkable impact on the I-loop nucleation. On the other hand, the bubble formation depends much on the existence of helium, in which the number density of bubbles for PHe = 10−7 and 10−5 appm He/s is much higher than that for PHe = 0. This is because helium atoms trapped in a bubble increase the vacancy binding energy, and suppress the vacancy dissociation from the bubble, resulting in a promotion of the bubble nucleation. And then, the helium effect on the promotion of bubble nucleation is very strong, even the number of helium atoms in a bubble is not so large

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

    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.

  15. Development of a Mass Flowmeter based on the Coriolis Acceleration for Liquid, Supercritical and Superfluid Helium

    De Jonge, T; Rivetti, A; Serio, L

    2002-01-01

    Beginning in the 1980's, Coriolis meters have gained generalised acceptance in liquid applications with a worldwide installed base of over 300,000 units. To meet the demands of cryogenic applications below 20 K, off-the-shelf Coriolis meters have been used, with minor design modifications and operational changes. The meters were originally calibrated on water and tested on liquid helium at 4.5 K, supercritical helium around 5 K and superfluid helium below 2 K. The meters maintain their intrinsic robustness and accuracy of better than 1% of measured value; accuracy is independent of density and temperature.

  16. On helium abundance variations in the associations and clusters of O and B stars

    The method proposed for helium abundance determination in atmospheres of O6-B2 stars is extended to the region of later B stars. As a result of this procedure more accurate N(He)/N (H) values are obtained for O-associations and young clusters considered earlier and helium abundance is determined for some new groups of hot stars. On the whole 138 stars of spectral types O6.5-B8 and luminosity classes 5-3 are investigated. The conclusion of previous works that helium abundance tends to increase with the age of stellar groups is confirmed

  17. Precipitation in low energy helium irradiated molybdenum

    The precipitation of low energy helium injected into molybdenum has been monitored by thermal helium desorption spectrometry (THDS). Precipitates nucleating at vacancies have been studied in the range from n = 1 to n = 2500 He per precipitate. The behaviour of the growing precipitates with respect to helium trapping, self-interstitial capture and emission, and helium release is discussed against the background of results of TEM work done for precipitates with n > 500 He. Evidence is found for (i) 'trap mutation' at n = 10 He, i.e. formation of bound self-interstitials around the helium filled vacancy, and (ii) emission of at least one of these 'mutation produced self-interstitials' (MPI) at n approx. 12 He. For larger precipitates (n > 20 He) the emission of single MPI is not apparent. At n = 1000 signs of helium binding to MPI-loops punched out by the precipitates are observed in the spectra. (author)

  18. Tritium-helium effects in metals

    Investigations of helium effects in metals at the Savannah River Laboratory have been carried out by introducing helium by radioactive decay of tritium. This process does not create concurrent radiation damage, such as accompanies ion implantation and (n,?) reactions. The process has its own peculiarities, however, which partially mask and interact with the helium effect of interest. The distribution and local concentration of helium and tritium, which are responsible for changes in mechanical properties and fracture mode, are controlled by the large difference in solubility and diffusivity between the two atoms and by their differing interaction energies with lattice defects, impurities, and internal boundaries. Furthermore, in all investigations with helium generated from tritium decay, some tritium and deuterium are always present. Consequently, property changes include tritium-helium interaction effects to some extent. Results of investigations with several austenitic stainless steels, Armco iron, and niobium single crystals illustrate the variety of phenomena and some of the complex interactions that can be encountered

  19. Helium diffusion in nickel at high temperatures

    Helium has been implanted at certain temperatures between 800 and 12500C into single and polycrystalline Ni-samples with implantation depths between 15 and 90 μm. Simultaneously the helium reemission from the sample is measured by a mass-spectrometer. It has been shown that the time dependence of the observed reemission rate is governed by volume diffusion of the helium. Measuring this time dependence as a function of temperature the helium diffusion constant has been determined. The He-diffusion is interpreted as a interstitial diffusion hindered by thermal vacancies. Depending on the implantation depth more or less of the implanted helium remains in the sample and forms large helium bubbles. (orig./GSCH)

  20. Helium permeability through austenitic stainless steel

    Anderl, R.A.; Nagata, P.K.

    1989-09-01

    The by-product canister for the Special Isotope Separation Project will be austenitic stainless steel. The by-product produces, among other things, helium gas from alpha particle decay. To determine whether the helium gas pressure will increase with time, the permeability of helium through austenitic stainless steel was calculated using data from the literature. It was found that stainless steel is essentially impermeable to helium at 523 K (250{degree}C), the predicted maximum canister storage temperature. Therefore, based on the estimated helium production rate and the canister volume, the helium gas pressure will increase with time up to about 0.9 atm at the end of the canister's 50-year life. 16 refs., 1 fig.

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

    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 adsorption cylinders...

  2. Impact of laparoscopy with carbon dioxide versus helium on local and systemic inflammation in an animal model of peritonitis.

    Jacobi, C A; Ordemann, J; Halle, E; Volk, H D; Mller, J M

    1999-06-01

    Increased intraperitoneal pressure and insufflation of carbon dioxide during laparoscopy may cause sepsis by promoting systemic inflammation in patients with intra-abdominal inflammatory diseases. The influence of carbon dioxide and helium during laparoscopy on bacteremia, endotoxemia, the plasma concentration of tumor necrosis factor-alpha (TNF-alpha), TNF-alpha secretion ex vivo by peripheral blood mononuclear cells (PBMCs), and intraperitoneal abscess formation was investigated in an animal model. A standardized fecal inoculum was injected intraperitoneally, and rats underwent laparoscopy with either carbon dioxide (N = 20) or helium (N = 20) or no further manipulation (control group; N = 20). Bacteremia was significantly more common 1 hour after laparoscopy with CO2 than in animals receiving helium or the control group. Furthermore, helium use led to a significant decrease of bacteremia 1 week after intervention. Fecal inoculation caused significant leukocytopenia in all groups within 1 hour after intervention, with complete recovery only in the helium-treated group (p helium-treated group, and suppression of ex vivo production recovered only in the animals undergoing laparoscopy with helium (p helium (2+/-1.5) than after CO2 laparoscopy (6.3+/-5.1) or in the control group (5.2+/-4.8). Laparoscopy with CO2 increased systemic inflammation only slightly, while helium use was associated with a significant lower incidence of bacteremia and local and systemic inflammation compared with the control group. PMID:10414552

  3. 43 CFR 16.2 - Applications for helium disposition agreements.

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Applications for helium disposition... HELIUM § 16.2 Applications for helium disposition agreements. The application for a helium disposition... Secretary to determine that the proposal will conserve helium that will otherwise be wasted, drained,...

  4. Helium isotopic abundance variation in nature

    Holden, N.E.

    1993-08-01

    The isotopic abundance of helium in nature has been reviewed. This atomic weight value is based on the value of helium in the atmosphere, which is invariant around the world and up to a distance of 100,000 feet. Helium does vary in natural gas, volcanic rocks and gases, ocean floor sediments, waters of various types and in radioactive minerals and ores due to {alpha} particle decay of radioactive nuclides.

  5. The growth of helium burning cores

    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.

  6. Capture of slow antiprotons by helium atoms

    Revai, J.; Shevchenko, N.V.(Nuclear Physics Institute, Řež, 25068, Czech Republic)

    2004-01-01

    A consistent quantum mechanical calculation of partial cross-sections leading to different final states of antiprotonic helium atom was performed. For the four-body scattering wave function, corresponding to the initial state, as well as for the antiprotonic helium wave function, appearing in the final tate, adiabatic approximations was used. Calculations were carried out for a wide range of antiprotonic helium states and incident energies of the antiproton. Obtained energy dependances of som...

  7. Energy, helium, and the future: II

    Krupka, M.C.; Hammel, E.F.

    1980-01-01

    The importance of helium as a critical resource material has been recognized specifically by the scientific community and more generally by the 1960 Congressional mandate to institute a long-range conservation program. A major study mandated by the Energy Reorganization Act of 1974 resulted in the publication in 1975 of the document, The Energy-Related Applications of Helium, ERDA-13. This document contained a comprehensive review and analysis relating to helium resources and present and future supply/demand relationships with particular emphasis upon those helium-dependent energy-related technologies projected to be implemented in the post-2000 year time period, e.g., fusion. An updated overview of the helium situation as it exists today is presented. Since publication of ERDA-13, important changes in the data base underlying that document have occurred. The data have since been reexamined, revised, and new information included. Potential supplies of helium from both conventional and unconventional natural gas resources, projected supply/demand relationships to the year 2030 based upon a given power-generation scenario, projected helium demand for specific energy-related technologies, and the supply options (national and international) available to meet that demand are discussed. An updated review will be given of the energy requirements for the extraction of helium from natural gas as they relate to the concentration of helium. A discussion is given concerning the technical and economic feasibility of several methods available both now and conceptually possible, to extract helium from helium-lean natural gas, the atmosphere, and outer space. Finally, a brief review is given of the 1980 Congressional activities with respect to the introduction and possible passage of new helium conservation legislation.

  8. Measurements on exotic atoms of helium

    Baird, S.; Batty, C. J.; Russell, F. M.; Sharman, P.; Bird, P. M.; Clough, A. S.; Parker, K. R.; Pyle, G. J.; Squier, G. T. A.

    1983-01-01

    Measurements of X-ray yields, energies and strong interaction effects have been made for muonic, pionic, kaonic, antiprotonic and sigma-helium atoms. The strong interaction measurements for kaons confirm the discrepancy previously reported between experiment and values calculated with an optical model. However, in contradiction to previous work there is good agreement between theory and experimental measurements of strong interaction effects in antiprotonic-helium. The first observation of X-rays from sigma-helium atoms is reported.

  9. Helium enrichment during convective carbon dioxide dissolution

    Larson, T.; Hesse, M. A.

    2013-12-01

    Motivated by observed variations of the CO2/He ratios in natural carbon dioxide (CO2) reservoirs, such as the Bravo Dome field in northeastern New Mexico, we have performed laboratory experiments equilibrating gas mixtures containing Helium (He) and CO2 with water, at close to ambient conditions in a closed system. The experimental design allows for continuous measurement of headspace pressure as well as timed interval measurements of the CO2/He ratios and the ?13C value of CO2 in the headspace. Results from three dissolution experiments are reported: 1) pure Helium system, 2) 98% CO2 + 2% Nitrogen system, and 3) 97% CO2 and 3% Helium. Final equilibrated experimental results are compared to theoretical results obtained using Henry's Law relationships. The evolution of the amount of dissolved CO2 computed from gas pressure and gas compositions are in good agreement with Henry's Law relationships. For example, the CO2 + N2 system was initially pressurized with pure CO2 to 1323 mbar and after six days it equilibrated to a measured headspace pressure of 596 mbar. This compares very well with a calculated equilibrium headspace pressure of 592 mbar for this system. The CO2 + He system was pressurized to 1398 mbar CO2 and after six days equilibrated to a measured headspace pressure of 397 mbar. This measured pressure is slightly higher than the predicted equilibrated headspace pressure of 341 mbar, indicating a possible leak in the system during this particular experiment. In both experiments the initial pH of the water was 9.3 and the final equilibrated pH was 5.4. The ?13C value of equilibrated headspace CO2 was within 0.25 of its starting ?13C value, demonstrating insignificant carbon isotope fractionation at low pH. Measured Helium/ CO2 ratios throughout the CO2+Helium experiment preserve a non-linear trend of increasing He/ CO2 ratios through time that correlate very well with the measured pressure drop from CO2 dissolution. This indicates that gas composition, in particular the He/ CO2-ratio, can be used to infer the amount of dissolved CO2 in the field where pressure evolution is not available. Our experiments show that the rate of dissolution is determined by convective mass transfer in the brine. Convective transport is driven by the increase of water density with increasing CO2 saturation. However, unlike previous experiments with analog systems we do not observe a constant dissolution rate. This is due to the continued drop in gas pressure that continuously reduces the equilibrium aqueous CO2 concentration and with it the driving force for convection. This feed back may significantly reduce the magnitude of solubility trapping that can be expected during geological CO2 storage.

  10. Groundwater origin and evolution from dissolved helium isotopes in the Kumamoto Plain

    Groundwater contains various types of dissolved gases, which are considered to provide information about the geoenvironment. Especially, the dissolved noble gases have been used to survey groundwater movement as natural tracers. In this study, we revealed the groundwater origins and the size and position of groundwater basins by investigating a trend of groundwater evolution deduced from the increase in dissolved helium content and change in helium isotopes ratio. The study area is a typical volcanic aquifer in Japan that was formed 105 years ago by piling up four layers of pyroclastic flow that erupted from the active volcano, Mt Aso, located on the east fringe of the Kumamoto Plain. We measured the dissolved helium content and ratio of isotopes to evaluate the origin and the mixing process of groundwater, and to distinguish the groundwater basins. Shallow groundwater in the basin was recharged by rainwater and was characterised by accumulating helium components distinguished from differences in helium isotope ratio along the flow paths in the basins. The sources of excess helium accumulated in shallow groundwater were categorized into two groups having a high 3He/4He ratio of 4.0 - 5.1x10-6 found in waters collected at hot-spas inside the caldera of Mt Aso, and one having a low of 0.8 ? 1.9x10-6 found in hot springs outside the caldera. Dissolved helium was categorized into three groups: a small amount of excess helium content with 3He/4He ratio equivalent to the dissolved atmospheric helium, high excess helium content with 3He/4He ratio up to 2x10-6, and small excess helium with high 3He/4He ratio up to 4.4x10-6. Consequently, the groundwater basin was split into four small basins by the combining characteristics of content and isotopic ratio of dissolved helium with information on the geohydrological formation, and the mixing process of groundwater was deduced from the change in the 3He/4He ratio of helium in groundwater samples, which was supplied from two helium sources with a greatly different 3He/4He ratio. (authors)

  11. Observations of cavitation in superfluid helium

    Nishigaki, Kazu; Takeda, Minoru; Inoue, Norihiko [Kobe Univ. of Mercantile Marine (Japan)

    1999-07-01

    To investigate the cavity formation and the motion of cavity in liquid helium (normal helium, He I and super helium, He II), an observation system was constructed. The system contains a cryostat for He II experiments and a high speed video system. Using this apparatus, liquid heliums were made cavitate in the vicinity of the surface of steel sphere which falls in He I or He II at high speed. the motion and the shape of cavities were successfully observed at the first time. Experimental results of negative pressures were compared with cavitation theory. (author)

  12. Observations of cavitation in superfluid helium

    To investigate the cavity formation and the motion of cavity in liquid helium (normal helium, He I and super helium, He II), an observation system was constructed. The system contains a cryostat for He II experiments and a high speed video system. Using this apparatus, liquid heliums were made cavitate in the vicinity of the surface of steel sphere which falls in He I or He II at high speed. the motion and the shape of cavities were successfully observed at the first time. Experimental results of negative pressures were compared with cavitation theory. (author)

  13. Low evaporation helium cryostat with a refrigerator

    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)

  14. Helium supply demand in future years

    Adequate helium will be available to the year 2000 AD to meet anticipated helium demands for present day applications and the development of new superconducting technologies of potential importance to the nation. It is almost certain that there will not be enough helium at acceptable financial and energy cost after the turn of the century to meet the needs of the many promising helium based technologies now under development. Serious consideration should be given to establishing priorities in development and application based upon their relative value to the country. In the first half of the next century, three ways of estimating helium demand lead to cumulative ranges of from 75 to 125 Gcf (economic study), 89 to 470 Gcf (projected national energy growth rates) and 154 to 328 Gcf (needs for new technologies). These needs contrast with estimated helium resources in natural gas after 2000 AD which may be as low as 10 or 126 Gcf depending upon how the federal helium program is managed and the nation's natural gas resources are utilized. The technological and financial return on a modest national investment in further helium storage and a rational long term helium program promises to be considerable

  15. Trapping fermionic and bosonic helium atoms

    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 i...

  16. Helium Extraction from LNG End Flash

    Kim, Donghoi

    2014-01-01

    Helium is an invaluable element as it is widely used in industry such as cryo-genics and welding due to its unique properties. However, helium shortage is expected in near future because of increasing demand and the anxiety of sup-ply. Consequently, helium production has attracted the attention of industry. The main source of He is natural gas and extracting it from LNG end-flash is considered as the most promising way of producing crude helium. Thus, many process suppliers have proposed proc...

  17. Trapping fermionic and bosonic helium atoms

    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...

  18. Helium turbo-expander with an alternator

    Study was made on a helium turbo-expander, the heart of helium refrigerator systems, in order to develop a system which satisfies the required conditions. A helium turbo-expander with externally pressurized helium gas bearings at the temperature of liquid nitrogen and an alternator as a brake have been employed. The essential difference between a helium turbo-expander and a nitrogen turbo-expander was clarified. The gas bearing lubricated with nitrogen at room temperature and the gas bearing lubricated with helium at low temperature were tested. The flow rate of helium in a helium refrigerator for a large superconducting magnet is comparatively small, therefore a helium turbine must be small, but the standard for large turbine design can be applied to such small turbine. Using the alternator as a brake, the turbo-expander was easily controllable electrically. The prototype turbo-expander was made, and the liquefaction test with it and MHD power generation test were carried out. (Kako, I.)

  19. Exposure of Pershore CR39 and Kodak LR115 films to helium ions

    Alpha particle plastic track detectors of the type Kodak LR115-II and Pershore CR39 have been exposed to helium ions of energies in the interval 1.3 to 5.5 MeV and of angle of incidence between 0 and 85 degrees. The helium ions were obtained from the 3UDH Pelletron tandem accelerator in Lund. Results of the angular and energy response of the detectors are presented and the consequences for radon detection are discussed. (author)

  20. Helium stratification in HD 145792: a new Helium strong star

    Catanzaro, G

    2007-01-01

    In this paper we report on the real nature of the star HD 145792, classified as He weak in {\\it ``The General Catalogue of Ap and Am stars''}. By means of FEROS@ESO1.52m high resolution spectroscopic data, we refined the atmospheric parameters of the star, obtaining: T$_{\\rm eff}$ = 14400 $\\pm$ 400 K, $\\log g$ = 4.06 $\\pm$ 0.08 and $\\xi$ = 0 $^{+0.6}$ km s$^{-1}$. These values resulted always lower than those derived by different authors with pure photometric approaches. Using our values we undertook an abundance analysis with the aim to derive, for the first time, the chemical pattern of the star's atmosphere. For metals a pure LTE synthesis (ATLAS9 and SYNTHE) has been used, while for helium a hybrid approach has been preferred (ATLAS9 and SYNSPEC). The principal result of our study is that HD 145792 belongs to He strong class contrary to the previous classification. Moreover, helium seems to be vertically stratified in the atmosphere, decreasing toward deepest layers. For what that concerns metals abundanc...

  1. Operational experience with the supercritical helium during the TF coils tests campaign of SST-1

    Panchal, Rohitkumar Natvarlal; Patel, Rakesh; Tank, Jignesh; Mahesuria, Gaurang; Sonara, Dashrath; Tanna, Vipul; Patel, Jayant; Srikanth, G. L. N.; Singh, Manoj; Patel, Ketan; Christian, Dikens; Garg, Atul; Bairagi, Nitn; Gupta, Manoj Kumar; Nimavat, Hiren; Shah, Pankil; Sharma, Rajiv; Pradhan, Subrata

    2012-06-01

    Under the 'SST-1 mission mandate' recently, all the sixteen Steady State Superconducting Tokamak (SST-1) Toroidal Field (TF) magnets have been successfully tested at their nominal currents of 10000 A in cold under supercritical helium (SHe) flow conditions. The TF magnets test campaign have begun in an experimental cryostat since June 2010 with the SST-1 Helium cryogenics facility, which is a 1.3 kW at 4.5 K helium refrigerator-cum-liquefier (HRL) system. The HRL provides ~300 g-s-1supercritical helium (SHe) with cold circulator (CC) as well as ~ 60 g-s-1 without cold circulator to fulfill the forced flow cooling requirements of SST- 1 magnets. In case of single TF coil tests, we can adjust HRL process parameters such that an adequate amount of required supercritical helium is available without the cold circulator. In this paper, the complete process is describing the Process Flow Diagram (PFD) of 1.3 kW at 4.5 K HRL, techniques to generate supercritical helium without using the cold-circulator and the results of the cooldown, steady state characteristics and experience of supercritical helium operations during the TF coils test campaign have been discussed.

  2. The consequences of helium production and nickel additions on microstructure development in isotopically tailored ferritic alloys

    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 60Ni which produces no helium, 59Ni which produces helium at a rate of about 10 appm He/dpa, or natural nickel which provides an intermediate level of helium due to delayed development of 59Ni. Specimens were irradiated in the HFIR at Oak Ridge, TN to 7.5 dpa at 300 and 400 C. Microstructural examinations indicated that nickel additions promote precipitation in all alloys, but the effect appears to be much stronger at 400 C than at 300 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 59Ni and natural nickel. Also, helium bubble development for high helium generation conditions appeared to be very different at 300 and 400 C. At 300 C, it appeared that high densities of bubbles formed whereas at 400 C, bubbles could not be identified, possibly because of the complexity of the microstructure, but more likely because helium accumulated at precipitate interfaces

  3. Dielectric tracking in liquid helium

    Measurements of the breakdown field of typical magnet insulators of thickness < 0.7 mm, under conditions in which the breakdown is by surface tracking across the narrow dimension, yield values which are characteristic of helium gas at the saturated vapour pressure for temperatures above the lambda point. Below the lambda point, the breakdown field rises again, but does not attain its 4.2 K value. Measurements also show that the tracking strength of a surface badly contaminated with metal particles is not appreciably less than that for a clean surface. (author)

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

    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.

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

    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

  6. Off-diagonal long-range order (ODLRO) and ground state properties of liquid helium

    An independent calculation of the condensate fraction and the ground state energy of liquid helium is given. The Froehlich ansatz for the second reduced density matrix in conjunction with the ODLORO hypothesis for liquid helium below the critical temperature is used. Froehlich's ansatz is shown to be consistent with numerical calculations of the ground state properties of liquid helium. The ground state energy was -5.100K, close to the experimental value. The condensate fraction turned out to be about 10% which is within the margin of error of recent neutron scattering experiments and agrees with other theoretical calculations

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

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

    1983-01-01

    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.

  8. Helium refrigerator maintenance and reliability at the OPAL cold neutron source

    Thiering, Russell; Taylor, David; Lu, Weijian

    2012-06-01

    Australia's first Cold Neutron Source (CNS) is a major asset to its nuclear research program. The CNS, and associated helium refrigerator, was commissioned in 2006 and is operated at the Open Pool Light Water nuclear Reactor (OPAL). The OPAL CNS operates a 20K, 5 kW Brayton cycle helium refrigerator. In this paper relevant experiences from helium refrigerator operation, maintenance and repair are presented along with the lessons learnt from a series of technical investigations. Turbine failure, due to volatile organic species, is discussed along with the related compressor oil degradation and oil separation efficiency.

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

    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

  10. Helium-heated steam reformer

    Catalyst action and the supply of high-temperature heat generating energy cause a steam reforming reaction on light hydrocarbons, which produces the reducing gas. The reactor, which permits this reaction to take place, is a steam reformer, the conventional type of which is a flame heating furnace. A heat-exchanger type steam reformer was newly developed for the National Research and Development Programme nuclear steel making project. Unlike conventional ones, this reactor is heated by high-temperature helium. A steam reforming process test plant was planned to test the performance and characteristics of this new steam reformer. Construction of the test plant was begun in 1975. It was completed at the end of May 1978. Subsequently, research and development passed on to the operating phase. The test plant has a nominal raw material treatment capacity of 100 kg/hr. The nominal quantity of heat exchanged is 310,000 Kcal/hr. The paper on the helium-heated steam reformer of this test plant is presented

  11. Helium-3 evolution from vanadium tritide

    Using methods of thermal desorption and pressure measurement in the process of tritium storage with the help of vanadium tritide a study was made in helium-3 behaviour. Investigation results showed that vanadium is a promising material for tritium storage and it can be used as a tritium generator. The latter within a reasonable period of time can generate tritium free from radiogenic helium

  12. Post-giant evolution of helium stars

    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.)

  13. Helium in the larderello geothermal fluid

    D'Amore, F.; Truesdell, A.

    1984-01-01

    A recent survey of helium concentrations in Larderello steam showed that there has been a strong decrease since earlier surveys and that the helium is concentrated in central zones of steam up-flow. The He decline and present distribution are interpreted as being due to the release of stored He produced by production-induced microfracturing. ?? 1984.

  14. Helium Speech: An Application of Standing Waves

    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…

  15. 30 CFR 256.11 - Helium.

    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...

  16. LOX Tank Helium Removal for Propellant Scavenging

    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).

  17. Properties and problems of helium stars

    Spectra atmospheric structure, individual objects, abundances, evolution of model helium stars, the (g, T(eff))-diagram, variability, and atmospheric motions are discussed. A list of 37 helium stars is presented together with galactic coordinates, proper motions, colors, radial velocities etc. (BJ)

  18. Free convection heat transfer to supercritical helium

    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)

  19. Helium-cooled high temperature reactors

    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

  20. Helium abundances and the helium isotope anomaly of sdB stars

    Geier, S; Edelmann, H; Morales-Rueda, L; Kilkenny, D; O'Donoghue, D; Marsh, T R; Copperwheat, C

    2011-01-01

    Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have been measured with high accuracy. We confirm the correlation of helium abundance with temperature and the existence of two distinct sequences in helium abundance found previously. We focused on isotopic shifts of helium lines and found helium-3 to be strongly enriched in 8 of our programme stars. Most of these stars cluster in a small temperature range between 27000 K and 31000 K very similar to the known helium-3-rich main sequence B stars, which cluster at somewhat lower temperatures. This phenomenon is most probably related to diffusion processes in the atmosphere, but poses a challenge to diffusion models.

  1. HELIUM CORE WHITE DWARFS IN CATACLYSMIC VARIABLES

    Binary evolution predicts a population of helium core (M sun) white dwarfs (WDs) that are slowly accreting hydrogen-rich material from low-mass main-sequence or brown dwarf donors with orbital periods less than 4 hr. Four binaries are presently known in the Milky Way that will reach such a mass-transferring state in a few Gyr. Despite these predictions and observations of progenitor binaries, there are still no secure cases of helium core WDs among the mass-transferring cataclysmic variables. This led us to calculate the fate of He WDs once accretion begins at a rate M-dot-10M-odot yr-1 set by angular momentum losses. We show here that the cold He core temperatures (Tc 7 K) and low M-dot thermonuclear runaway. Shara and collaborators noted that these large accumulated masses may lead to exceptionally long classical nova (CN) events. For a typical donor star of 0.2 Msun, such binaries will only yield a few hundred CNe, making these events rare among all CNe. We calculate the reheating of the accreting WD, allowing a comparison to the measured WD effective temperatures in quiescent dwarf novae and raising the possibility that WD seismology may be the best way to confirm the presence of a He WD. We also find that a very long (>1000 yr) stable burning phase occurs after the CN outburst, potentially explaining enigmatic short orbital period supersoft sources like RX J0537-7034 (Porb = 3.5 hr) and 1E 0035.4-7230 (Porb = 4.1 hr).

  2. Spectrographic detection of nitrogen impurity in helium

    A device to observe very small amount of nitrogen impurity in helium gas was developed for a liquefaction system of helium. The principle of detection is based on the optical spectroscopy of the discharge arc in the helium gas. The new detector uses 427.8 nm spectral line as the detection light source while the previous works in this type of detectors used 391.4 nm spectral line. The advantage of newly introduced spectral line is that there is no strong helium spectral line in the neighbor of the observed line. As a result, it became possible to build a simple and reliable impurity detector which can continuously observe very small amount of nitrogen in helium. (author)

  3. Global helium particle balance in LHD

    Global helium particle balance in long-pulse discharges is analyzed for the first time in the Large Helical Device (LHD) with the plasma-facing components of the first wall and the divertor tiles composed of stainless steel and carbon, respectively. During the 2-min discharge sustained by ion cyclotron resonance heating (ICRH) and electron cyclotron heating (ECH), helium is observed to be highly retained in the wall (regarded as both the first wall and the divertor tiles). Almost all (about 96%) puffed helium particles (1.3 × 1022 He) are absorbed in the wall near the end of the discharge. Even though a dynamic retention is eliminated, 56% is still absorbed. The analysis is also applied to longer pulse discharges over 40 min by ICRH and ECH, indicating that the helium wall retention is dynamically changed in time. At the initial phase of the discharge, a mechanism for adsorbing helium other than dynamical retention is invoked

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

    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)

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

    A series of alloys have been made adding various isotopes of nickel to a ferritic/martensitic steel in order to vary the production of helium during irradiation. 1.5% nickel was added to Fe-12Cr either in the form of 60Ni which produces no helium, 59Ni which produces helium at a rate of about 10 appm He/dpa, or natural nickel which provides an intermediate level of helium due to delayed development of 59Ni. Specimens were irradiated in the HFIR to 7 dpa at 300, 400, 500, and 600 C. This paper reports on microstructural differences and differences in deformation response, measured by shear punch testing, found between these specimens irradiated under identical conditions but with the different nickel isotopes. Little microstructural difference was found between specimens with 59Ni and NatNi. Helium bubble development for high helium generation conditions appeared to be very different at 300 and 400 C. At 300 C, it appeared that high densities of bubble-like features formed whereas at 400 C, only voids could be found. The addition of nickel at any isotopic balance to the Fe-12Cr base alloy significantly increased the shear yield and maximum strengths of the alloys with the strength of the alloys decreasing with increasing irradiation temperature. However, helium itself, up to 75 appm at over 7 dpa, appears to have little effect on the mechanical properties of the alloys. (orig.)

  6. Carbon Shell or Core Ignitions in White Dwarfs Accreting from Helium Stars

    Brooks, Jared; Schwab, Josiah; Paxton, Bill

    2016-01-01

    White dwarfs accreting from helium stars can stably burn at the accreted rate and avoid the challenge of mass loss associated with unstable Helium burning that is a concern for many Type Ia supernovae scenarios. We study binaries with helium stars of mass $1.25 M_\\odot\\le M_{\\rm{He}} \\le 1.8 M_\\odot$, which have lost their hydrogen rich envelopes in an earlier common envelope event and now orbit with periods ($P_{\\rm orb}$) of several hours with non-rotating $0.84$ and $1.0 M_\\odot$ C/O WDs. The helium stars fill their Roche lobes (RLs) after exhaustion of central helium and donate helium on their thermal timescales (${\\sim}10^5$yr). As shown by others, these mass transfer rates coincide with the steady helium burning range for WDs, and grow the WD core up to near the Chandrasekhar mass ($M_{\\rm Ch}$) and a core carbon ignition. We show here, however, that many of these scenarios lead to an ignition of hot carbon ashes near the outer edge of the WD and an inward going carbon flame that does not cause an explo...

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

    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.

  8. Exotic helium molecules; Molecules exotiques d'helium

    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)

  9. Helium doping of a vanadium alloy by a modified tritium trick

    The goal of this work was to develop a suitable method of doping vanadium tensile specimens with helium. With a successful method, a better simulation of fusion conditions will be attained for specimens that are irradiated in the Materials Open Test Assembly (MOTA) experiment in the Fast Flux Test Facility (FFTF). A tritium trick technique was used to implant 3He in V-15Cr-5Ti. Modifications include wrapping specimens with tantalum foil and decay hold at 4000C. Removal of undecayed tritium at 7000C may have been excessive, because large helium bubbles in the grain boundaries severely embrittled the V-15Cr-5Ti alloy. More realistic helium distributions can probably be produced by reducing the removal temperature. The technique might facilitate the study of helium embrittlement and provide a screening method for alloy development

  10. Determination of helium in beryl minerals

    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(α, η) 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)

  11. The Infrared Spectrum of the Helium Molecular Ion HELIUM-3 Positive HELIUM-4.

    Yu, Nan

    This dissertation is concerned with the first experimental observation of the vibration-rotation spectrum of the helium molecular ion, ^3He ^4He^+. The Doppler-tuned fast-beam laser-resonance technique has been used. The ions produced in an electron-impact ion source form an ion beam of a few KeV and then intersect nearly colinearly with a CO IR laser beam of fixed frequency. The velocity of the ions is scanned to tune the ions into resonance with the laser frequency. Subsequent resonance detection is realized by using charge exchange processes of the ion with a target gas. Twelve spectral lines have been measured which correspond to nine different vibration-rotation transitions of the R branch in the fundamental band of the ground state of ^3He^4He ^+. The combination of the kinematic compression of the fast-beam method and the special frequency stabilization of the CO laser render an experimental accuracy of 0.0006 cm^{-1} or 0.4 ppm. The accuracy exceeds that of the available theory by three orders of magnitude. The narrow spectral linewidth also allows partial resolution of the magnetic hyperfine structure due to helium-3. A hyperfine structure calculation has been carried out using a numerical multi-configuration self-consistent-field method. The agreement between the calculation and the observation is very satisfying.

  12. Practical data on steady state heat transport in superfluid helium at atmospheric pressure

    Experimental results covering a technically interesting range of temperatures (1.4 <= T <= Tsub(lambda)) and channel dimensions (L <= 100 cm, 0.2 <= id <= 5 mm) have been compiled into a collection of practical data on steady state heat transport in superfluid helium at atmospheric pressure. The data, given in the form of diagrams, allow all the problems of linear steady state heat transport in superfluid helium at atmospheric pressure to be solved directly. (author)

  13. Fine structure of helium-like ions and determination of the fine structure constant

    Pachucki, Krzysztof; Yerokhin, Vladimir A.

    2010-01-01

    We report a calculation of the fine structure splitting in light helium-like atoms, which accounts for all quantum electrodynamical effects up to order \\alpha^5 Ry. For the helium atom, we resolve the previously reported disagreement between theory and experiment and determine the fine structure constant with an accuracy of 31 ppb. The calculational results are extensively checked by comparison with the experimental data for different nuclear charges and by evaluation of the hydrogenic limit ...

  14. Helium blistering in Fe40Ni38Mo4B18, Fe40Ni40P14B6 and Ni45Fe5Co20Cr10Mo4B16 metallic glasses

    Radiation damage and ion implantation studies on metallic glasses are scientifically interesting to understand the nature of defects in amorphous materials. The radiation-induced structural and property changes may give information on the type of defects produced in glassy system and description of the nature of permanent disorder in the glasses. In this paper, the authors report on radiation-induced blistering and the formation of gas bubbles in three nickel-based amorphous alloys after helium implantation at room temperature. The surface topography of the irradiated targets was examined for blistering with a scanning electron microscope, and the microstructure was examined with a transmission electron microscope. The experimental procedure and the results are reported. The gas bubble formation and blistering behavior were similar in both metallic glasses and crystalline solids. First, the clear understanding of vacancy and interstitial defects in metallic glasses must be established. Then, the bubble formation and blistering in metallic glasses can be described in a similar way to that in crystalline materials. The experiment on blister formation in metallic glasses in relation to target temperature may provide information. (Kako, I.)

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

    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.

  16. Electric response in superfluid helium

    Chagovets, Tymofiy V.

    2016-05-01

    We report an experimental investigation of the electric response of superfluid helium that arises in the presence of a second sound standing wave. It was found that the signal of the electric response is observed in a narrow range of second sound excitation power. The linear dependence of the signal amplitude has been derived at low excitation power, however, above some critical power, the amplitude of the signal is considerably decreased. It was established that the rapid change of the electric response is not associated with a turbulent regime generated by the second sound wave. A model of the appearance of the electric response as a result of the oscillation of electron bubbles in the normal fluid velocity field in the second sound wave is presented. Possible explanation for the decrease of the electric response are presented.

  17. Helium two-phase instabilities

    Instabilities encountered in helium two-phase flow during the cool down of superconducting magnets and transmission lines have been experimentally investigated in 1000 mm long vertical tubes of sizes 6.35 and 2.73 mm. Density wave oscillations were measured and recorded in both adiabatic and diabatic flow conditions. Pressure drop oscillations across the test section were observed with the aid of a sensitive differential pressure transducer. The average density at the exit of the experimental test section was a function of the dielectric constant measured by a capacitance probe. The period of the observed density wave sustained oscillations (0.2 to 3 seconds) were found to be of the same order of magnitude of the fluid particles residence time in the heated section. An empirical threshold criteria for the inception of these oscillations has been developed from similarity analysis. (author)

  18. Photoionization Energies and Oscillator Strengths of Helium and Helium-Like Ions with Z = 6-8

    In the photoionization process of helium and helium-like ions with Z 6-8(C4+, N5+, O6+), resonance energies of doubly excited autoionizing 1,3P0 states converging on the n = 4 and n = 5 hydrogenic thresholds were calculated by use of the diagonalization method. We also evaluated the oscillator strengths for transitions from 1s2 (1Se) to continuum 1 skp (1P0;) state. The calculations were done with the dipole length and velocity formulas using the six-parameter Hylleraas wavefunction for the ground state. The continuum state was represented by an antisymmetrized product of hydrogenics wavefunctions with completely screened Coulomb functions, and the autoionizing states by wavefunctions constructed in the diagonalization approximation within the framework of the theory of configuration interaction.

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

    The ion beam induced nanoscale synthesis of PtCx (where x ∼ 5) using the trimethyl (methylcyclopentadienyl)platinum(IV) (MeCpPtIVMe3) 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 μs, 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. (paper)

  20. Features of metrological characteristics of helium chromatographs and estimation of their stability as applied to problems of impurities control in coolant of HTGR plants

    Two models of helium chromatographs with complete automation of analysis, which can be installed and used independently, have been developed. They are used to determine contents of hydrogen, oxygen, methane, humidity, carbon oxide and dioxide impurities in concentration range of 5x10-5-10-1 vol.% in helium coolant. Helium chromatographs are used for control of impurity content in the HTGR plant coolant. 2 refs., 3 tabs

  1. Evolution of Helium Bubbles in ODS Steel

    Due to the superior thermal creep properties and the high resistance to neutron irradiation, oxide dispersion strengthened (ODS) steels are considered as potential candidate alloys for application in advanced nuclear or fusion reactor. The accumulation of helium after neutron irradiation has a substantial influence on the mechanical properties of materials, e.g. the intergranular embrittlement via helium bubble growth at grain-boundaries at temperatures higher than 0.33Tm (Tm is the melting point of metals), the void swelling, blistering of metal surface, and the rise of the ductilebrittle transition temperature (DBTT) of bcc structure metals. Therefore, the understanding of the helium behavior in ODS steels is important prior to its application in the nuclear energy field. Although a substantial studies have been conducted to investigate the effects and micro-mechanism of helium in ODS steels, the nucleation and growth of Helium in metals is not yet fully understood. In this work, we used low energy helium ions to be implanted into a commercial ODS alloy (MA956TM) sample, and investigated the evolution of the helium bubbles with fluences at room temperature using a TEM (Transmission Electron Microscope)

  2. Evolution of Helium Bubbles in ODS Steel

    Jang, Jin Sung; Kang, Suk Hoon; Jin, Hyeong Ha; Han, Chang Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Yang, Yi Tao; Zhang, Chong Hong [Chinese Academy of Sciences, Lanzhou (China)

    2012-05-15

    Due to the superior thermal creep properties and the high resistance to neutron irradiation, oxide dispersion strengthened (ODS) steels are considered as potential candidate alloys for application in advanced nuclear or fusion reactor. The accumulation of helium after neutron irradiation has a substantial influence on the mechanical properties of materials, e.g. the intergranular embrittlement via helium bubble growth at grain-boundaries at temperatures higher than 0.33T{sub m} (T{sub m} is the melting point of metals), the void swelling, blistering of metal surface, and the rise of the ductilebrittle transition temperature (DBTT) of bcc structure metals. Therefore, the understanding of the helium behavior in ODS steels is important prior to its application in the nuclear energy field. Although a substantial studies have been conducted to investigate the effects and micro-mechanism of helium in ODS steels, the nucleation and growth of Helium in metals is not yet fully understood. In this work, we used low energy helium ions to be implanted into a commercial ODS alloy (MA956{sup TM}) sample, and investigated the evolution of the helium bubbles with fluences at room temperature using a TEM (Transmission Electron Microscope)

  3. In Beam Tests of Implanted Helium Targets

    McDonald, J E; Ahmed, M W; Blackston, M A; Delbar, T; Gai, M; Kading, T J; Parpottas, Y; Perdue, B A; Prior, R M; Rubin, D A; Spraker, M C; Yeomans, J D; Weissman, L; Weller, H R; Delbar, Th.; Conn, LNS/U; Duke, TUNL/

    2006-01-01

    Targets consisting of 3,4He implanted into thin aluminum foils (approximately 100, 200 or 600 ug/cm^2) were prepared using intense (a few uA) helium beams at low energy (approximately 20, 40 or 100 keV). Uniformity of the implantation was achieved by a beam raster across a 12 mm diameter tantalum collimator at the rates of 0.1 Hz in the vertical direction and 1 Hz in the horizontal direction. Helium implantation into the very thin (approximately 80-100 ug/cm^2) aluminum foils failed to produce useful targets (with only approximately 10% of the helium retained) due to an under estimation of the range by the code SRIM. The range of low energy helium in aluminum predicted by Northcliffe and Shilling and the NIST online tabulation are observed on the other hand to over estimate the range of low energy helium ions in aluminum. An attempt to increase the amount of helium by implanting a second deeper layer was also carried out, but it did not significantly increase the helium content beyond the blistering limit (ap...

  4. Investigation of a magnetically stabilized helium arc

    For verifying some theoretical predictions of light scattering from magnetized plasmas, a stable pulsed helium arc discharge in a magnetic field up to 5 teslas has been built. The arc has been investigated at filling pressures of 2 to 5 Torr and plasma currents between 1 and 5 kA. Plasma parameters were measured at a magnetic field of 4 teslas and a pressure of 3 Torr. At these values of the magnetic field and the filling pressure the arc is steady, approximately cylindrically symmetric up to a plasma current of 2.8 kA. Time dependence and radial distribution of the electron density and temperature have been determined from spectroscopic measurements, laser interferometry, and laser scattering. The latter two techniques were used successfully for the first time on a magnetically stabilized arc to measure the electron density and temperature in the hot core of the arc. The axial electron density is 1.2 x 1016 cm-3 and is approximately constant over the arc cross section in the high temperature region as predicted by theory. The axial temperature is 145,000 K. Thus the arc design and the plasma properties are suitable for scattering experiments. (author)

  5. SPIN PHYSICS: Magnification by superfluid helium mirror

    Full text: A 'quasi-parabolic' mirror coated with superfluid helium-4 may have advanced the recently developed art of 'atomic optics'; it should certainly increase the intensity of the Mark II ultra-cold spin-polarized atomic hydrogen jet, which should travel to Russia in 1995. The Michigan team is now building the Mark II Jet to serve as the internal polarized target for both the NEPTUN-A experiment (Michigan, MIT, IHEP-Protvino, JINRDubna) led by Alan Krisch and the NEPTUN experiment (IHEP-Protvino, JINR-Dubna, Moscow, St. Petersburg) led by Vladimir Solovianov. Both experiments will use the UNK- 1 proton accelerator now being installed at IHEP-Protvino (Serpukhov) to study various.spin effects in 400 GeV proton-proton scattering. The existing 70 GeV accelerator, U-70, will be the injector for UNK-1 which will first operate as a 400 GeV storage ring for NEPTUN and NEPTUN-A. Until the 600 GeV extracted beam programme begins a few years later, NEPTUN and NEPTUN-A will be the only experiments operating at the huge 21 km circumference accelerator. Thus the intensity of the Mark II Jet is quite important. If the jet reaches the expected thickness of 1013 polarized protons per sq cm, then the luminosity with UNK's planned 6x1014 stored protons will be 1032 cm-2 s-1. The use of ultra-cold techniques to produce high densities of spinpolarized hydrogen atoms was pioneered by atomic physics teams led by D. Kleppner (MIT), I. Silvera (Harvard), and J. Walraven (Amsterdam). Michigan's Mark-ll Jet will use a 12 Tesla superconducting solenoid and a helium-3/helium-4 dilution refrigerator operating at about 0.3 K with a cooling power of about 100 mW. The strong magnetic field gradient at the solenoid's edge will accelerate those hydrogen atoms whose magnetic moments are parallel to the field; these spinpolarized atoms should emerge as a rather monoenergetic jet because the 12 Tesla solenoid's 'magnetic acceleration' energy is about 25 times larger than the thermal energy near 0.3 Kelvin. The Michigan team first built a prototype to help maximize the intensity of the Mark II Jet. Vladimir Luppov, a Michigan visitor from JINR-Dubna, proposed using the new 'quantum reflection' technique developed by Walraven's team, which recently found that superfluid helium-4 reflected about 80% of incoming hydrogen atoms. Luppov suggested installing, at the Prototype Jet's exit aperture, a highly polished parabolic mirror coated with superfluid helium-4 to focus the emerging hydrogen atoms into a parallel beam. Unfortunately the parabolic copper mirror gave little intensity gain. The Michigan team then realized that a parabola is the correct shape only when there is no magnetic field gradient; the strong gradient of the prototype's 8 Tesla solenoid distorted the path of the emerging atoms. So they next built a 'quasi-parabolic copper mirror shaped to compensate for the field gradient of the 8 Tesla solenoid. This superfluid helium coated mirror worked much better than expected. The mirror increased the polarized hydrogen atom intensity by a factor of 7.5, measured by a small aperture compression tube detector about 80 cm downstream of the mirror. This new technique was then immediately integrated into the Mark-ll Jet's design. The mirror's focusing should allow a fairly small aperture (11 cm) superconducting sextupole to focus about half of the emerging spin-polarized hydrogen atoms; the resulting polarized proton jet of about 1013 cm-2 should give a luminosity of 1032 cm-2 s-1 when crossing the 400 GeV UNK-1 beam

  6. Present activities of the Helium Supply System for ITER HCCR TBM

    The HCCR (Helium Cooled Ceramic Reflector) is designed cooling down by the helium cooling system (HCS) with high temperature and pressure (300-500 .deg. C, 8 MPa) helium gas and its mass flow rate is 1.5 kg/s during normal operation. The scaled-down helium supply system (HeSS) had been constructed and modified to obtain thermal-hydraulics test data, operational experience and to validate the HCS design in 2011-2013. The first HeSS was constructed in 2012, however more than 2 MW of heating power is required to heat up room temperature to 300 .deg. C for normal operation helium flow condition of the HCS (=1.5 kg/s). In 2013, a recuperator was installed in the HeSS facility to reduce the required heating power from 2 MW to 150 kW and to control helium mass flow rate and the temperature more effectively, yet the circulator was able up to 0.5 kg/s of helium mass flow which is only one third of normal operation condition of HCS. In present status, a full-scale helium circulator is developing in Jinsolturbo Co. and the real-scale circulator will be installed in the HeSS facility by end of 2014. To solve the revealed problems and to make full-scale mass flow rate, the full-scale circulator is developing by Jinsolturbo Co and it will be installed in the HeSS facility by 2014

  7. Present activities of the Helium Supply System for ITER HCCR TBM

    Lee, E. H.; Kim, S. K.; Yoon, J. S.; Jin, H. G.; Lee, D. W. [Korea Atomic Energy Research Institute, Daejon (Korea, Republic of); Lee, Si Woo [Jinsol Turbo Machinery Co.,Ltd, Seoul (Korea, Republic of)

    2014-05-15

    The HCCR (Helium Cooled Ceramic Reflector) is designed cooling down by the helium cooling system (HCS) with high temperature and pressure (300-500 .deg. C, 8 MPa) helium gas and its mass flow rate is 1.5 kg/s during normal operation. The scaled-down helium supply system (HeSS) had been constructed and modified to obtain thermal-hydraulics test data, operational experience and to validate the HCS design in 2011-2013. The first HeSS was constructed in 2012, however more than 2 MW of heating power is required to heat up room temperature to 300 .deg. C for normal operation helium flow condition of the HCS (=1.5 kg/s). In 2013, a recuperator was installed in the HeSS facility to reduce the required heating power from 2 MW to 150 kW and to control helium mass flow rate and the temperature more effectively, yet the circulator was able up to 0.5 kg/s of helium mass flow which is only one third of normal operation condition of HCS. In present status, a full-scale helium circulator is developing in Jinsolturbo Co. and the real-scale circulator will be installed in the HeSS facility by end of 2014. To solve the revealed problems and to make full-scale mass flow rate, the full-scale circulator is developing by Jinsolturbo Co and it will be installed in the HeSS facility by 2014.

  8. Trapping and diffusion of helium in lunar minerals

    Harris-Kuhlman, Kimberly Renae

    1998-12-01

    The goal of the research performed in this dissertation is to improve the understanding of the trapping and diffusion of helium in lunar minerals, especially ilmenite. The Moon is the most promising source of large amounts of 3He needed for future fusion fuel, and 3He seems to be preferentially trapped in lunar ilmenite. The parabolic differential equation for diffusion was combined with solar wind data from Pioneer 10 and a description of the lunar environment to create a computational model of helium implantation and diffusion in the lunar regolith. This computational approach established an upper bound of 3 x 10-25 cm2/s for the diffusivity of He in the lunar regolidi at 400K, the maximum lunar temperature. The diffusivity of He isotopes in ilmenite, a mineral known for its helium retention capability, was measured experimentally. Samples of several terrestrial ilmenites, were analyzed using electron probe microanalysis to determine the closest analog of lunar ilmenite. The most suitable simulants were ilmenite from Quebec and New York. These samples were implanted with 4He to 1016 ions/cm2/ 3He to 1013 ions/cm2 and H from 10 14 ions/cm2 to 1017 ions/cm2 at solar-wind energies using Plasma Source Ion Implantation (PSII). Isochronal annealing with mass spectroscopy of the evolved 4He demonstrated release behavior similar to that of the Apollo 11 regoliths. Moderate fluences of H were seen to retard 3He release, while a high fluence of H had little effect. A three-dimensional computational code, ANNEAL, was developed for calculating diffusivity from the results of these annealing experiments. The helium (both 3He and 4He) diffusion in these samples is characterized by four distinct activation energies, E1 = 0.26 eV, E2 ? 0.5 eV, E3 ? 1.5 eV and E4 > 2.2 eV. These energies are characteristic of diffusion through two amorphous layers and detrapping from oxygen vacancies and constitutional vacancies, respectively. The diffusivity of 3He was seen to be at least a factor of 10 higher than the diffusivity of 4He. A diffusivity of 9 x 10-24 cm2/s at 400K was determined for diffusion of helium with activation energy of 1.4 eV. This behavior is consistent with helium trapping in oxygen vacancies.

  9. Helium: current status and future outlook

    Continuation of present activities and further developments in the application of superconductivity is crucially dependent on the continued availability of helium. Even the changes that are likely to occur due to the use of higher temperature superconductors will probably not affect the need for helium since in order to attain appropriate current carrying capacity in the new materials liquid helium temperatures may well be needed. World wide use of helium in 1988 is estimated to have been 2.3 to 2.4x109 std. cubic feet; up from 2.1x109 scf estimated for 1987. The 1989 use is expected to expand by ∼10%. On September 30, 1987 the date of the last report, 36x109 scf of helium was in the U.S. storage facility. One has to conclude that even with the estimated 10% annual increase in the use of helium ∼10 years of product is in reserve. Using the simplest model where a constant recovery of helium from natural gas accounts for a portion of the yearly use one still finds the U.S. reserve exhausted by the year 2001. The crisis can only be avoided by a less than 10% yearly growth in use or by new extraction plants recovering more helium from natural gas use. A critical review is presented covering the trends in other uses, estimation of reserve depletion and availability of new plants utilizing new sources. This includes an estimate of the onset of the crisis in availability and cost of helium. (author) 3 figs., 1 tab

  10. Kilohertz laser ablation for doping helium nanodroplets

    Mudrich, M.; Forkl, B.; Müller, S.; Dvorak, M.; Bünermann, O.; Stienkemeier, F.

    2007-10-01

    A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the nonvolatile DNA basis guanine is found to be efficient and a number of oligomers are detected.

  11. Kilohertz laser ablation for doping helium nanodroplets

    Mudrich, M; Müller, S; Dvorak, M; Buenermann, O; Stienkemeier, F

    2007-01-01

    A new setup for doping helium nanodroplets by means of laser ablation at kilohertz repetition rate is presented. The doping process is characterized and two distinct regimes of laser ablation are identified. The setup is shown to be efficient and stable enough to be used for spectroscopy, as demonstrated on beam-depletion spectra of lithium atoms attached to helium nanodroplets. For the first time, helium droplets are doped with high temperature refractory materials such as titanium and tantalum. Doping with the non-volatile DNA basis Guanine is found to be efficient and a number of oligomers are detected.

  12. Evolution of dopant-induced helium nanoplasmas

    Krishnan, S R; Fechner, L; Sharma, V; Kremer, M; Fischer, B; Camus, N; Pfeifer, T; Jha, J; Krishnamurthy, M; Schroeter, C -D; Ullrich, J; Stienkemeier, F; Moshammer, R; Fennel, Th; Mudrich, M

    2012-01-01

    Two-component nanoplasmas generated by strong-field ionization of doped helium nanodroplets are studied in a pump-probe experiment using few-cycle laser pulses in combination with molecular dynamics simulations. High yields of helium ions and a pronounced, droplet size-dependent resonance structure in the pump-probe transients reveal the evolution of the dopant-induced helium nanoplasma. The pump-probe dynamics is interpreted in terms of strong inner ionization by the pump pulse and resonant heating by the probe pulse which controls the final charge states detected via the frustration of electron-ion recombination.

  13. Proton and Helium spectra observed by RUNJOB

    Apanasenko, A. V.; Beresovksaya, V. A.; Fujii, M.; Galkin, V. I.; Hareyama, M.; Ichimura, M.; Ito, S.; Kamioka, E.; Kitami, T.; Kobayashi, T.; Kopenkin, V. V.; Kuramata, S.; Kuriyama, Y.; Lapshin, V. I.; Managadze, A. K.; Matsutani, H.; Misnikova, N. P.; Muhamedshin, R. A.; Namiki, M.; Nanjo, H.; Nazarov, S. N.; Nikolsky, S. I.; Oe, T.; Ohta, S.; Osedlo, V. I.; Oshuev, D. S.; Publichenko, P. A.; Rakobolskaya, I. V.; Roganova, T. M.; Saito, M.; Sazhina, G. P.; Semba, H.; Shabanova, Yu. N.; Shibata, T.; Sugimoto, H.; Sveshnikova, L. G.; Takahashi, K.; Tsutiya, T.; Taran, V. M.; Yajima, N.; Yamagami, T.; Yamamoto, K.; Yashin, I. V.; Zamchalova, E. A.; Zatsepin, G. T.; Zayarnaya, I. S.

    2001-08-01

    We have been carrying out 10 of long duration balloon flights with emulsion chamber for observation of cosmic- ray primaries from 1995 through 1999. We report the energy spectra of proton and helium primaries basing on 45% of observed data which have been analyzed up to now. Our results cover the energy range of 10 300 TeV for proton, and 2 50 TeV/n for helium. And one proton primary with the energy larger than 1015 eV is observed. Both of proton and helium spectra can connect to indirect measurement data smoothly.

  14. Cryogenic Thermal Studies on Terminations for Helium Gas Cooled Superconducting Cables

    Kim, Chul Han; Kim, Sung-Kyu; Graber, Lukas; Pamidi, Sastry V.

    Details of the design of terminations for testing a superconducting DC monopole cable cooled with gaseous helium are presented. The termination design includes a liquid nitrogen chamber to reduce heat influx into the helium section through current leads. Thermal studies on the assembly of the two terminations and a 1 m or 30 m cable cryostat were performed at variable mass flow rates of helium gas. Measurements of temperature profile for the test system without the superconducting cable showed temperature rise between 5 K and 20 K depending on the mass flow rate. The temperature profile across the test system was used to estimate the heat load from different components of the system. Results with and without the liquid nitrogen in current lead section were compared to estimate the savings provided by the liquid nitrogen on the head of the helium circulation system. Suggestions for improving the design to enable fully gas cooled terminations are presented.

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

    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)

  16. Helium release rates and ODH calculations from RHIC magnet cooling line failure

    A catastrophic failure of the magnet cooling lines, similar to the LHC superconducting bus failure incident, could discharge cold helium into the RHIC tunnel and cause an Oxygen Deficiency Hazard (ODH) problem. A SINDA/FLUINT(regsign) model, which simulated the 4.5K/4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the insulating vacuum volumes and discharging via the reliefs into the RHIC tunnel, had been developed. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces are included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Results, including helium discharge rates, helium inventory loss, and the resulting oxygen concentration in the RHIC tunnel area, are reported. Good agreement had been achieved when comparing the simulation results, a RHIC sector depressurization test measurement, and some simple analytical calculations.

  17. Helium release rates and ODH calculations from RHIC magnet cooling line failure

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

    2011-03-28

    A catastrophic failure of the magnet cooling lines, similar to the LHC superconducting bus failure incident, could discharge cold helium into the RHIC tunnel and cause an Oxygen Deficiency Hazard (ODH) problem. A SINDA/FLUINT{reg_sign} model, which simulated the 4.5K/4 atm helium flowing through the magnet cooling system distribution lines, then through a line break into the insulating vacuum volumes and discharging via the reliefs into the RHIC tunnel, had been developed. Arc flash energy deposition and heat load from the ambient temperature cryostat surfaces are included in the simulations. Three typical areas: the sextant arc, the Triplet/DX/D0 magnets, and the injection area, had been analyzed. Results, including helium discharge rates, helium inventory loss, and the resulting oxygen concentration in the RHIC tunnel area, are reported. Good agreement had been achieved when comparing the simulation results, a RHIC sector depressurization test measurement, and some simple analytical calculations.

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

    We have studied, with a Monte Carlo simulation code ACAT-DIFFUSE, the fluence-dependence of the amount of helium atoms retained 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 re-emission, reflection and sputtering from tungsten carbide under helium ion irradiation were derived and compared with each other. We have discussed the retention curves for incident energy of 5 keV at incident angles of 0 deg. and 80 deg. and of 500 eV at 0 deg. The energy spectra of helium atoms reflected from tungsten carbide for incident energy of 500 eV at 0 deg. and 80 deg. were compared with those from graphite and tungsten

  19. 21 CFR 868.1640 - Helium gas analyzer.

    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...

  20. Failure of choroidal melanoma to respond to helium ion therapy

    Helium ion irradiation is a promising alternative therapy for choroidal melanoma. In short-term follow-up (less than 5 years), more than 90% (18/19) of treated patients demonstrated tumor regression. Researchers had to enucleate five eyes after helium ion therapy either because of continued tumor growth (four patients) or other complications (one patient). Two melanomas continued to grow and seemed to be radioresistant. In two other tumors it retrospectively seemed that the entire lesion was not inside the radiation field. In one patient total retinal detachment and glaucoma developed; enucleation was performed because of a painful eye. Metastatic disease developed in no patients. The treatment failures emphasize that there are a number of unresolved issues regarding the use of charged-particle irradiation in the treatment of melanoma. Further studies must be performed to answer these questions and better delineate the use of these newer forms of therapy

  1. Testing electron correlation in Helium using attosecond pulses

    Ruiz, Camilo [Centro de Laseres Pulsados (CLPU), Plaza de la Merced s/n, Salamanca 37008 (Spain)

    2011-07-01

    Using a full quantum model beyond the one dimensional model, we are able to study the double correlated double ionization of Helium in several regimes. For example in the near IR, we have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a {lambda}=800 nm laser, with intensity I=4.5 x 10{sup 14} W/cm{sup 2}. We observe a finger-like structure in the correlated electron momentum distribution that can be interpreted as a signature of the microscopic dynamics in the recollision process. To study related process such as the excitation by recollision we make use of attosecond pulses to probe the dynamics of ionization. In this paper we introduce this novel technique to study the interaction that could lead increase the accuracy of the description of the correlated processes.

  2. Testing electron correlation in Helium using attosecond pulses

    Using a full quantum model beyond the one dimensional model, we are able to study the double correlated double ionization of Helium in several regimes. For example in the near IR, we have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a λ=800 nm laser, with intensity I=4.5 x 1014 W/cm2. We observe a finger-like structure in the correlated electron momentum distribution that can be interpreted as a signature of the microscopic dynamics in the recollision process. To study related process such as the excitation by recollision we make use of attosecond pulses to probe the dynamics of ionization. In this paper we introduce this novel technique to study the interaction that could lead increase the accuracy of the description of the correlated processes.

  3. Crystal structure and density of helium to 232 kbar

    Mao, H. K.; Wu, Y.; Jephcoat, A. P.; Hemley, R. J.; Bell, P. M.; Bassett, W. A.

    1988-01-01

    The properties of helium and hydrogen at high pressure are topics of great interest to the understanding of planetary interiors. These materials constitute 95 percent of the entire solar system. A technique was presented for the measurement of X-ray diffraction from single-crystals of low-Z condenses gases in a diamond-anvil cell at high pressure. The first such single-crystal X-ray diffraction measurements on solid hydrogen to 26.5 GPa were presented. The application of this technique to the problem of the crystal structure, equation of state, and phase diagram of solid helium is reported. Crucial for X-ray diffraction studies of these materials is the use of a synchrotron radiation source which provides high brillance, narrow collimation of the incident and diffracted X-ray beams to reduce the background noise, and energy-dispersive diffraction techniques with polychromatic (white) radiation, which provides high detection efficiency.

  4. Neovascular glaucoma after helium ion irradiation for uveal melanoma

    Neovascular glaucoma developed in 22 of 169 uveal melanoma patients treated with helium ion irradiation. Most patients had large melanomas; no eyes containing small melanomas developed anterior segment neovascularization. The mean onset of glaucoma was 14.1 months (range, 7-31 months). The incidence of anterior segment neovascularization increased with radiation dosage; there was an approximately three-fold increase at 80 GyE versus 60 GyE of helium ion radiation (23% vs. 8.5%) (P less than 0.05). Neovascular glaucoma occurred more commonly in larger tumors; the incidence was not affected by tumor location, presence of subretinal fluid, nor rate of tumor regression. Fifty-three percent of patients had some response with intraocular pressures of 21 mmHg or less to a combination of antiglaucoma treatments

  5. Linear electron chains on the surface of superfluid helium

    Kovdrya, Yu. Z.; Nikolaenko, V. A.; Gladchenko, S. P.; Sokolov, S. S.

    1998-11-01

    A unique one-dimensional system of linear electron chains on the liquid helium surface is realized experimentally for the first time. This system is created by using the distortion of the helium surface and covering the profiled dielectric substrate in a confining electric field holding electrons in the liquid channels being formed. The carrier mobility in linear electric chains is measured in the temperature interval 0.5-1.8K in confining fields up to 1 kV/cm. It is shown that the electron mobility depends on the purity of the substrate surface. For clean substrates, the mobility increases with decreasing temperature in the entire investigated temperature range. The results of measurements are found to be in accord with the existing theory.

  6. Genetic changes in Mammalian cells transformed by helium cells

    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.

  7. The Helium Cryogenic System for the ATLAS Experiment

    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.

  8. Genetic changes in Mammalian cells transformed by helium cells

    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/μm). 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

  9. Two-electron ejection from helium by Compton scattering

    Double ionization of the ground state of helium by Compton scattering is investigated using many-body perturbation theory. Representative calculations of cross sections differential in the scattered photon energy and angle are given to illustrate the nature of the process. Total cross sections for single ionization and double ionization of helium and the ratio of these cross sections are presented for energies from 2.5 to 20 keV. Current experimental data for the ratio due to both Compton scattering and photoionization are in reasonable agreement with the corresponding calculations presented here. However, comparisons of the present results with other calculations reveal substantial discrepancies. Possible reasons for these differences at finite energies are proposed. Our results for double ionization by Compton scattering have not reached an asymptotic limit

  10. Helium magnetic refrigerator. II. Liquefaction process and efficiency

    Magnetic refrigeration techniques are based on the utilization of the magnetocaloric effect. A change in entropy occurring as a result of a change in magnetization leads to heat-transfer processes. The magnetic refrigerator consists of two parts, including the magnetic materials and the heat-exchange system. Advantages of this type of refrigerator compared to the gas refrigerator are related to high efficiency, compactness, and high reliability. The present investigation is concerned with a new Carnot type refrigeration system which liquefies helium with the aid of Gd3Ga5O12 (GGG) as a refrigerant. Attention is given to the heat transfer between GGG and helium gas, the experimental apparatus, and the obtained experimental results. 7 references

  11. Diffusion and permeation constants of helium in various glasses

    Measurements of the diffusion and permeation constant (and hence the solubility) of helium in different types of German glass (Duran, GW, GW12, N16B, AW, and Supremax) were performed to investigate their suitability as materials for use in mass spectrometric systems for ultra low level tritium measurements on natural water samples. The measurements were conducted by the Barrer method with the helium being detected by a mass spectrometer calibrated by measurement of defined amounts of air drawn from a 0.6 litre stainless steel container. Reproducibility of the standard measurements was about 1.5%, the sensitivity of the quadrupole mass spectrometer varying by only about 4% for partial pressures of helium ranging from about 10-4 to 10-8 mbar. The diffusion constants decrease from Duran via GW12, GW, N16B, and AW to Supremax. The Bunsen solubilities are only slightly temperature dependent and the mean values range from 5.29 x 10-3 in Duran to 7.89 x 10-4 in AW glass. (author)

  12. LOCA analysis for Korean helium cooled solid breeder TBM

    One of the major ITER goals is test blanket module (TBM) program which is for the demonstration of the breeding capability that would lead to tritium self-sufficiency in a reactor and the extraction of high-grade heat suitable for electricity generation under the ITER fusion environment. While the engineering design of Korean helium cooled solid breeder (HCSB) TBM and its ancillary systems has been performed, a safety assessment on different possible accident scenarios should be carried out for the purpose of licensing. In this paper, accident analyses for several loss of coolant accident (LOCA) cases were performed in order to assess safety aspects of the TBM design using RELAP5/MOD3.2. Since the TBM forms a loop with helium cooling system (HCS) which is one of ancillary systems required for removing heat deposited in the TBM by neutron wall loading and surface heat flux from plasma, it is necessary to model the complete loop for accident analysis. In this study, the helium passage including the TBM and HCS was nodalized for each accident scenario. The TBM and HCS components were modeled as the associated heat structures provided by RELAP5 to include heat transfer across solid boundaries. Based on computational results it was found that current design of the TBM is robust from the safety point of view.

  13. The polaron state of surface electrons over helium covering structured substrate

    The conductivity of surface electrons over a liquid helium film, covering the structurized silicon substrate with a regular system of micropores, is investigated experimentally in the temperature range T = 1.5-2.7 K. It is found that the conductivity decreases sharply at T>= 2.5 K, which is supposed to be due to the formation of autolocalized polaron electron state over the helium film. To check the hypothesis for the formation of the polaron state of surface electron in the dense vapor helium, the free energy of the polaron was calculated. It is shown that the free energy minimum oc-curs when the temperature rises to a critical value corresponding to the formation of polaron and close to the temperature of the decrease of conductivity observed experimentally. The calculation predicts the dependence of the critical temperature on the parameters of the effective potential acting in the plane of the helium surface and associated with the distortion of the helium surface due to the structure of the substrate, which contributes to the appearance of a localized charge over the helium film.

  14. Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy.

    Yu, Yaowei; Hu, Jiansheng; Wan, Zhao; Wu, Jinhua; Wang, Houyin; Cao, Bin

    2016-03-01

    Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ∼0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10(-6)-5.0 × 10(-2) Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eV and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (PD2 ) and helium partial pressure (PHe) could be obtained. The result shows that deuterium partial pressure could be measured if PD2 > 10(-6) Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if PHe/PD2 > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning. PMID:27036832

  15. Theory and modelling of helium enrichment in plasma experiments with pump limiters

    Helium enrichment in the exhaust gas stream flowing from a hydrogen-helium plasma is studied using an analytical theory and Monte Carlo simulations. To provide a sensitive experimental test in a tokamak, an unusual configuration, inverted from traditional designs, is proposed for a pump limiter. The principle can be tested in other plasma devices as well. The theory suggests that for typical plasma edge conditions in a confinement device, namely, n = 1013cm-3 and T/sub i/ = T/sub e/ approx. = 5-30eV, helium enrichment in the neutral gas exhaust stream can be very high, in the range 5 to 7, relative to the helium-hydrogen ratio in the plasma. Such high enrichment factors are achieved by exploiting the difference between the ionization rates of hydrogen and helium and the negligible helium charge exchange rate at these plasma conditions. A limiter arrangement is proposed in which the natural curvature of the toroidal magnetic field is used to isolate, using the plasma itself, the point of plasma neutralization from the location of the gas exhaust. The plasma region then acts to preferentially screen the recycling hydrogen by the processes of ionization and of charge-exchange-induced losses at open boundaries. The theory and analysis suggests that an experiment can provide a sensitive test of modules used to describe the plasma edge and of atomic and surface physics data used in these models

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

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

    1988-05-01

    Effects of inhalation of cold air or helium-oxygen mixture on lung resistance (RL) were studied in anesthetized and tracheotomized rabbits under normal ambient pressure and in human volunteers under normo- and hyperbaric conditions. In artificially ventilated rabbits, an increase in RL occurred when the tracheal temperature fell to 10 degrees C. This effect was more than double with helium breathing compared to air, despite a lower respiratory heat loss by convection (Hc) with helium. In 3 normal humans, inhalation of cold air (mouth temperature = 8 degrees C) at sea level had no effect on RL value. However, with a helium-nitrogen-oxygen mixture, a weak but significant increase in RL due to cold gas breathing was measured in 1 subject at 2 ATA and in 2 individuals at 3.5 ATA. The density of inhaled gas mixture (air or He-N2-O2) was near the same in the three circumstances (1, 2, and 3.5 ATA) but Hc value increased with helium. At 8 ATA a 30-55% increase in RL occurred in the 3 divers during inhalation of cold gas (Hc was multiplied by 6 compared to air at sea level) and at 25 ATA the cold-induced bronchospasm ranged between 38 and 95% (Hc multiplied by 27). Thus, in rabbits and humans helium breathing enhanced the cold-induced increase in RL at normal or elevated ambient pressure, and this effect was interpreted as resulting from different mechanisms in the two circumstances. PMID:3388628

  17. Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy

    Yu, Yaowei; Hu, Jiansheng; Wan, Zhao; Wu, Jinhua; Wang, Houyin; Cao, Bin

    2016-03-01

    Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ˜0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10-6-5.0 × 10-2 Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eV and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (PD2) and helium partial pressure (PHe) could be obtained. The result shows that deuterium partial pressure could be measured if PD2 > 10-6 Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if PHe/PD2 > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning.

  18. Photoionization Energies and Oscillator Strengths of Helium and Helium-like Ions

    We first studied the resonant photoionization of helium-like ions, such as C4+, N5+, and O6+, and determined the wave functions, the excitation energies, and the partial and total widths of the autoionizing states of these ions lying under the n = 3 thresholds of the residual ion. For more detailed analysis of the theory, and a better comprehension of the internal dynamics of atomic resonances and electronic phenomena of correlation, we extended these calculations to other helium-like ions, under higher thresholds (n = 4 and 5) of the hydrogen ions H-, and of Li+, C4+, N5+, and O6+. We were also interested in oscillator strengths. These parameters are important for interpreting the spectra and diagnosing astrophysical and laboratory plasmas, as well as for analyzing the spectra coming from space and determining the composition and relative abundance from the various elements of the stellar and interstellar environment. We sought a better comprehension of the coupling between autoionizing and continuum states and of the phenomena of electronic correlations. We used the method of diagonalization that has been used below the n = 2 threshold of the residual ion. The results are important for astrophysicists and physicists studying matter-radiation interaction and for the invention of new laser systems. We also measured laser-induced chlorophyll fluorescence (LICF) emission spectra of the leaves of some tropical plants using a compact fiber-optic fluorosensor with a continuous-wave violet diode laser as the exciting source and an integrated digital spectrometer to analyze the state of stress of the plants

  19. Use of separating nozzles or ultra-centrifuges for obtaining helium from gas mixtures containing helium

    To obtain helium from gas mixtures containing helium, particularly from natural gas, it is proposed to match the dimensions of the separation devices for a ratio of the molecular weights to be separated of 4:1 of more, which ensures a higher separation factor and therefore a smaller number of separation stages to be connected in series. The process should make reasonably priced separation of helium possible. (orig./HP)

  20. Helium purification system for HTR-10

    Design characters and test methods of helium purification system for HTR-10 are introduced. The key equipment, the design of pipes and codes have been verified by the performance test. The test shows that the design is successful

  1. Helium Find Thaws the Cold Fusion Trail.

    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)

  2. On the helium gas leak test

    The helium gas leak test (Helium mass spectrometer testing) has a leak detection capacity of the highest level in practical leak tests and is going to be widely applied to high pressure vessels, atomic and vacuum equipments that require high tightness. To establish a standard test procedure several series of experiments were conducted and the results were investigated. The conclusions are summarized as follows: (1) The hood method is quantitatively the most reliable method. The leak rate obtained by tests using 100% helium concentration should be the basis of the other method of test. (2) The integrating method, bell jar method, and vacuum spray method can be considered quantitative when particular conditions are satisfied. (3) The sniffer method is not to be considered quantitive. (4) The leak rate of the hood, integrating, and bell jar methods is approximately proportional to the square of the helium partial pressure. (auth.)

  3. Development of charcoal sorbents for helium cryopumping

    Testing of the cryogenically cooled charcoal using fusion-compatible binders for pumping helium has shown promising results. The program demonstrated comparable or improved performance with these binders compared to the charcoal (type and size) using an epoxy binder

  4. Charged condensate and helium dwarf stars

    White dwarf stars composed of carbon, oxygen and heavier elements are expected to crystallize as they cool down below certain temperatures. Yet, simple arguments suggest that the helium white dwarf cores may not solidify, mostly because of zero-point oscillations of the helium ions that would dissolve the crystalline structure. We argue that the interior of the helium dwarfs may instead form a macroscopic quantum state in which the charged helium-4 nuclei are in a BoseEinstein condensate, while the relativistic electrons form a neutralizing degenerate Fermi liquid. We discuss the electric charge screening, and the spectrum of this substance, showing that the bosonic long-wavelength fluctuations exhibit a mass gap. Hence, there is a suppression at low temperatures of the boson contribution to the specific heatthe latter being dominated by the specific heat of the electrons near the Fermi surface. This state of matter may have observational signatures

  5. Helium-Hydrogen Recovery System Project

    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. Helium pumping with liquid ring vacuum pump

    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

  7. Vacuum-ultraviolet laser uses superfluid helium

    Zmuidzinas, J. S.

    1979-01-01

    Vacuum ultra violet laser in wavelength around 0.800 microns is produced by using optical pumping to increase lifetimes of excited metastable molecules in super fluid helium. In method, super fluid helium is pumped electronically to produce excited HE2, and then pumped by circularly polarized 0.9096 - micron radiation to aline excited HE2 molecular spins. High power ultraviolet radiation has potential applications in molecular reaction studies, power transmission in space, and biomedical research.

  8. Helium-propane as drift chamber gas

    A light gas mixture, consisting of helium and propane (0.938 : 0.062) at atmospheric pressure has been tested in a large single-volume drift chamber. Contrary to the general belief that helium cannot be used as a drift gas due to its high ionisation potential, the above mixture was found to have stable operation with spatial resolution of 260+-40 μm. (orig.)

  9. Electrons on the surface of liquid helium

    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

  10. Helium refrigeration considerations for ADS cryomodule design

    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)

  11. Helium in tungsten: a calculational approach

    Werf, Dirk Peter van der,

    1994-01-01

    In dit proefschrift wordt het gedrag van heliumatomen in het metaal wolfraam bestudeerd door middel van theoretische berekeningen en computersimulaties. Omdat helium een edelgas is, lost het slecht op in wolfraam. Als helium toch in wolfraam terecht komt, doordat het er bijvoorbeeld in geschoten wordt, gaat het er vanwege zijn hoge mobiliteit snel weer uit of wordt het gebonden aan roosterfouten. Voorbeelden van roosterfouten zijn onzuiverheidsatomen op plaatsen waar een wolfraamatoom had moe...

  12. Recovery of helium ion irradiated molybdenum

    Helium ion irradiation of molybdenum was carried out to study recovery of radiation induced defects using electrical resistivity up to 1083 K. The recovery stage at ? 463 K has been assigned to the migration of vacancies. The increase in the resistivity after stage III has been explained on the basis of helium-vacancy complex formation. Results are compared with those obtained using Positron annihilation. (author)

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

    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.

  14. The role of helium gas in medicine.

    Berganza, Carlos J; Zhang, John H

    2013-01-01

    The noble gas helium has many applications owing to its distinct physical and chemical characteristics, namely: its low density, low solubility, and high thermal conductivity. Chiefly, the abundance of studies in medicine relating to helium are concentrated in its possibility of being used as an adjunct therapy in a number of respiratory ailments such as asthma exacerbation, COPD, ARDS, croup, and bronchiolitis. Helium gas, once believed to be biologically inert, has been recently shown to be beneficial in protecting the myocardium from ischemia by various mechanisms. Though neuroprotection of brain tissue has been documented, the mechanism by which it does so has yet to be made clear. Surgeons are exploring using helium instead of carbon dioxide to insufflate the abdomen of patients undergoing laparoscopic abdominal procedures due to its superiority in preventing respiratory acidosis in patients with comorbid conditions that cause carbon dioxide retention. Newly discovered applications in Pulmonary MRI radiology and imaging of organs in very fine detail using Helium Ion Microscopy has opened exciting new possibilities for the use of helium gas in technologically advanced fields of medicine. PMID:23916029

  15. Sonic helium detectors in the Fermilab Tevatron

    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.

  16. Pulsating Helium Atmosphere White Dwarfs

    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. Microstructure characterization and optical properties of sapphire after helium ion implantation

    The (0 0 0 1) sapphire samples are irradiated with 60 keV helium ions at the fluences of 5 × 1016, 1 × 1017and 5 × 1017 ions/cm2 at room temperature. After implantation, two broad absorption bands at 320–460 and 480–700 nm are observed and their intensities increase with the increasing ion fluence. The grazing incidence X-ray diffraction results indicate that the {0 0 0 1} diffraction peaks of sapphire decrease and broaden due to the disorientation of the generated crystallites after ion irradiation. The microstructure evolution is examined by the scanning and transmission electron microscopes. The surface becomes rough because of the aggregation of helium bubbles and migration towards the surface. There is a lattice expansion up to ∼4.5% in the implanted area and the lattice distortion measured from dispersion of (1 1 0) diffraction is ∼4.6°. Such strain of crystal lattice is rather large and leads to contrast fluctuation at scale of 1–2 nm (the bubble size). The laser induced damage threshold (LIDT) is investigated to understand the effect of helium ion beam irradiation on the laser damage resistance of sapphire components and the results show that the LIDT decreases from 5.4 to 2.5 J/cm2 due to the absorptive color centers, helium bubbles and defects induced by helium ion implantation. The laser damage morphologies of samples before and after ion implantation are also presented

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

    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)

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

    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, α) 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, α) reactions has been simulated by homogeneous alpha particles implantation in cyclotron, at room temperature, in specimens of thicknesses between 5 and 50 μm 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 ΔH=1.70eV Ag:D0=10-1.2cm2/s ΔH=1.51eV Al:Do=10+0.5cm2/s ΔH=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)

  20. Helium research in support of superconducting power transmission

    Jones, M. C. [ed.

    1979-04-01

    During FY 77, research for Superconducting Power Transmission Line (SPTL) development included the following four research tasks: preparation of computer codes for the computation of cooldown by either single stream or counterstream methods; experimental verification of cooldown computations with emphasis on counterstream cooling; thermal cycling of a length of lead-sheathed model cable destined for testing in the BNL 5th Avenue facility; and evaluation of heat flow sensors as a means of non-intrusive vacuum indication for power transmission line vacuum envelopes. A series of progress reports on these four tasks are presented, with 6 appendicies on: experimental observations of flow oscillations in a high aspect ratio heated tube with supercritical helium as coolant; the results of a study of friction factors measured in the same apparatus as was used in Appendix 1; results of a numerical study of the response of SPTL current leads to overload currents; the microwave cavity pressure transducer developed at NBS for SPTL application; a correlation of heat transfer data to supercritical helium in forced convection; and a pressure regulator designed and used in controlling the pressure of cryogenic helium at supercritical pressures.

  1. Helium isotopes in fluids of the Baykal rift zone

    Polyak, B.G.; Prasolov, E.M.; Tolstikhin, I.N.; Kozlovtseva, S.V.; Kononov, V.I.; Khutorskoy, M.D. (Inst. of Geology, Moscow (Russian Federation) All-Union Petroleum Geologic Exploration Research Inst., Saint Petersburg (Russian Federation) Kola Research Center, Apatity (Russian Federation))

    1993-02-01

    The isotopic composition of helium in subterranean fluids from 34 locations in southern Siberia and northern Mongolia has been measured. The ratio [sup 3]He/[sup 4]He ranges from radiogenic ([approximately]10[sup [minus]8]) to mantle ([approximately]10[sup [minus]5]) values. For the most part, the hydrocarbon fluids of the Irkutsk amphitheater contain only radiogenic helium; this distinguishes the amphitheater from ancient platforms. In contrast, fluids from the Baykal rift zone are distinguished by the presence of helium with a mantle component; this component reaches almost 100% in thermal fluids in the Tunka basin. The ratios CH[sub 4]/[sup 3]He and (CO[sub 2] + CH[sub 4])/[sup 3]He suggest that the methane and carbon dioxide in the rift zone fluids may be partially magmatogenic; in the Irkutsk amphitheater, on the other other hand, such gases originated as a result of purely crustal processes. The [sup 3]He/[sup 4]He ratio varies along the length of the Baikal rift zone, with decreasing values correlating with decreasing heat flow, increasing thickness of crust, and decreasing dimensions of rift basins. 39 refs., 4 figs., 3 tabs.

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

    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...

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

    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

  4. Helium-neon laser improves skin repair in rabbits.

    Peccin, Maria Stella; Renno, Ana Claudia Muniz; de Oliveira, Flavia; Giusti, Paulo Ricardo; Ribeiro, Daniel Araki

    2012-12-01

    The purpose of this study was to evaluate the influence of helium-neon laser on skin injury in rabbits. For this purpose, 15 New Zealand rabbits underwent bilateral skin damage in leg. Helium-neon laser light, at a fluence of 6?J?cm2 and wavelength of 632.8?nm, was applied on the left legs (laser group). The right leg lesions (control group) served as negative control. All sections were histopathologically analyzed using HE sections. The results showed little infiltration of inflammatory cells, with proliferation of fibroblasts forming a few fibrous connective tissue after 1 week post-injury. The lesion on the 3rd week was characterized by granulation tissue, which formed from proliferated fibrous connective tissue, congested blood vessels and mild mononuclear cell infiltration. On the 5th week, it was observed that debris material surrounded by a thick layer of connective tissue and dense collage, fibroblasts cells present in the dermis covered by a thick epidermal layer represented by keratinized epithelium. Taken together, our results suggest that helium-neon laser is able to improve skin repair in rabbits at early phases of recovery. PMID:23057697

  5. Helium exhaust studies with the ALT-II pump limiter in TEXTOR

    In TEXTOR helium removal experiments with the pump-limiter ALT-1I have started. To simulate the presence of helium ash in the plasma, helium is injected into the discharge (e.g. at t=0.7 s) as a short pulse of ?t=20 ms. It is found that the He is removed from the discharge in an e-folding time of about half a second for neutral beam heated plasmas and in an e-folding time of about 1.5 s in an OH plasma. The exhaust efficiency of helium amounts to about 8% and is close to the one for deuterium. The fuelling efficiency for the injected helium is found to be in the range of 50-100%; the remaining part seems to be stored in the TEXTOR walls. An estimate of the surface density leads to a value of several times 1013 cm-2. This helium can easily be liberated in succeeding discharges and can be removed efficiently when ALT is pumping. (orig.)

  6. Cryosorption of helium on argon frost in Tokamak Fusion Test Reactor neutral beamlines

    Helium pumping on argon frost has been investigated on Tokamak Fusion Test Reactor (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 twofold 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

  7. Cryogenic infrastructure for superfluid helium testing of LHC prototype superconducting magnets

    Benda, V.; Duraffour, G.; Guiard-Marigny, A.; Lebrun, Ph.; Momal, F.; Saban, R.; Sergo, V.; Tavian, L.; Vullierme, B. [CERN, Geneva (Switzerland)

    1994-12-31

    The Large Hadron Collider (LHC) project at CERN will require about 1800 high-field superconducting magnets, operating below 1.9 K in pressurized helium II. All magnets will be reception-tested before their installation in the 26.7 km circumference ring tunnel. For this purpose, the authors have installed large-capacity cryogenic facilities, beginning to operate for tests of full-scale prototype magnets produced by European industry. Based around a 6 kW@4.5 K helium refrigerator and a 25 m{sup 3} liquid helium storage, the system includes a low-pressure, 6 to 18 g/s helium pumping unit for 1.8 K refrigeration, a set of magnet cooldown and warmup units delivering each up to 120 kW of refrigeration at precisely controlled temperature, and a network of cryogenic lines for transferring liquid nitrogen, liquid helium and cold gaseous helium. All components are controlled by embedded PLCs, connected to a general supervision system for operator interface. The authors present the system layout and describe the design and performance of the main components.

  8. Study of heat transfer in superconducting cable electrical insulation of accelerator magnet cooled by superfluid helium

    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 (ΔT∼10-5 to 10-3 K) and in Gorter-Mellink regime (ΔT>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 μ). (author)

  9. Helium release behavior on amorphous ZrV2 tritide films

    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)

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

    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

  11. Accurate measurement of atmospheric helium isotopes.

    Sano, Yuji; Tokutake, Taichi; Takahata, Naoto

    2008-04-01

    We have developed an analytical system to measure atmospheric 3He/4He ratios precisely by using a static vacuum operation mass spectrometer and an ultrahigh-vacuum purification line. After purification of the sample, helium was introduced into the mass spectrometer. Ion beams of 3He and 4He were measured at the same time by a double collector system. A resolving power of about 700 at the 5% level of the peak height was attained for the complete separation of 3He ions from those of HD and H3. Repeated analysis of a sample calibrated against a standard showed a precision of about 0.2% error margin (2sigma). This system has been applied to evaluating the 3He/4He ratio of He Standard of Japan (HESJ), and for the assessment of the atmospheric variation of latitude. The observed 3He/4He ratio of HESJ, 20.405+/-0.040Rair (2sigma) agrees well with the value of 20.408+/-0.044Rair by Lupton and Evans, but is smaller than the recommended value of 20.63+/-0.10Rair in a literature. Air samples collected from 45 to 20 degrees N in the Far East showed a slight decrease of the 3He/4He ratio with latitude. Even though the variation is attributable to an experimental artifact, it may not preclude the possibility that the anthropogenic release of crustal 4He is significant in the high-latitude region of the northern hemisphere. PMID:18403846

  12. Design considerations for very large helium refrigeration system

    Future fusion reactors will require very large cryogenic refrigerators to cool their superconducting magnet systems. The total capacity required is roughly 5 times above the largest cryogenic system presently existing. For redundancy reasons however the capacity will be provided by several parallel plants. The step from today's state of technology to future needs therefore is moderate. The paper presents a draft design of a 150 kW/4.5 K Helium refrigeration system and compares it to today's state of technology. Development needs are identified, which on one hand result from the high capacity and on the other hand are based on weaknesses of today's technology. (author)

  13. Secondary helium system piping and helium purification for the HTGR-R and NHSDR

    The purpose of this report is to present the results of recent work done by United Engineers and Constructors on high temperature pipeing and helium purification for the secondary helium systems of the Reforming Plant HTGR (HTGR-R) and the Nuclear Heat Source Demonstration Reactor

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

    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/...

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

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

    2015-12-01

    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 mol3 He yr-1 and a lower limit for the crustal flux at 1.6 10-7 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 is 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.

  16. Thermal evolution of helium in magnetron sputtered titanium films

    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

  17. Rotons, Superfluidity, and Helium Crystals

    Fritz London understood that quantum mechanics could show up at the macroscopic level, and, in 1938, he proposed that superfluidity was a consequence of Bose-Einstein condensation. However, Lev Landau never believed in London's ideas; instead, he introduced quasiparticles to explain the thermodynamics of superfluid 4He and a possible mechanism for its critical velocity. One of these quasiparticles, a crucial one, was his famous ''roton'' which he considered as an elementary vortex. At the LT0 conference (Cambridge, 1946), London criticized Landau and his ''theory based on the shaky grounds of imaginary rotons''. Despite their rather strong disagreement, Landau was awarded the London prize in 1960, six years after London's death. Today, we know that London and Landau had both found part of the truth: BEC takes place in 4He, and rotons exist.In my early experiments on quantum evaporation, I found direct evidence for the existence of rotons and for evaporation processes in which they play the role of photons in the photoelectric effect. But rotons are now considered as particular phonons which are nearly soft, due to some local order in superfluid 4He. Later we studied helium crystals which are model systems for the general study of crystal surfaces, but also exceptional systems with unique quantum properties. In our recent studies of nucleation, rotons show their importance again: by using acoustic techniques, we have extended the study of liquid 4He up to very high pressures where the liquid state is metastable, and we wish to demonstrate that the vanishing of the roton gap may destroy superfluidity and trigger an instability towards the crystalline state

  18. Rotons, Superfluidity, and Helium Crystals

    Balibar, Sébastien

    2006-09-01

    Fritz London understood that quantum mechanics could show up at the macroscopic level, and, in 1938, he proposed that superfluidity was a consequence of Bose-Einstein condensation. However, Lev Landau never believed in London's ideas; instead, he introduced quasiparticles to explain the thermodynamics of superfluid 4He and a possible mechanism for its critical velocity. One of these quasiparticles, a crucial one, was his famous "roton" which he considered as an elementary vortex. At the LT0 conference (Cambridge, 1946), London criticized Landau and his "theory based on the shaky grounds of imaginary rotons". Despite their rather strong disagreement, Landau was awarded the London prize in 1960, six years after London's death. Today, we know that London and Landau had both found part of the truth: BEC takes place in 4He, and rotons exist. In my early experiments on quantum evaporation, I found direct evidence for the existence of rotons and for evaporation processes in which they play the role of photons in the photoelectric effect. But rotons are now considered as particular phonons which are nearly soft, due to some local order in superfluid 4He. Later we studied helium crystals which are model systems for the general study of crystal surfaces, but also exceptional systems with unique quantum properties. In our recent studies of nucleation, rotons show their importance again: by using acoustic techniques, we have extended the study of liquid 4He up to very high pressures where the liquid state is metastable, and we wish to demonstrate that the vanishing of the roton gap may destroy superfluidity and trigger an instability towards the crystalline state.

  19. Interaction of helium-3 impurities with point defects and deformation fields in solid helium-4

    Interaction between defects and impurities is widely believed to be at the root of a wide range of effects which had been observed in recent years in hcp solid helium-4. In particular, several theories place special role on the dislocation network pinning by helium-3 impurities. We report quantum Monte Carlo simulations of a helium-3 impurity in crystalline helium-4. Calculations are performed with the diffusion Monte Carlo method. This is a first principles approach which allows to obtain exact ground state of many-body bosonic systems. The results show that while vacancies are attracted to the impurity, the vacancy-He3 pair is not bound at low density. Additional impurity properties are extracted by simulating it in a strained crystal. Motion in the elastic deformation field can be used to describe the long-range interaction of helium-3 with various lattice defects, especially the dislocation lines.

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

    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

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

    Lee, Injun; Hong, Sungyull; Bai, Cheolho; Shim, Jaesool [Yeungnam Univ., Gyeongsan (Korea, Republic of); Kim, Chansoo; Hong, Sungdeok; Kim, Minhwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    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.

  2. Helium Exhaust Studies in H-Mode Discharges in the DIII-D Tokamak Using an Argon-Frosted Divertor Cryopump

    The first experiments demonstrating exhaust of thermal helium in a diverted, H-mode deuterium plasma have been performed on the DIII-D tokamak. The helium, introduced via gas puffing, is observed to reach the plasma core, and then is readily removed from the plasma with a time constant of ∼10--20 energy-confinement times by an in-vessel cryopump conditioned with argon frosting. Detailed analysis of the helium profile evolution suggests that the exhaust rate is limited by the exhaust efficiency of the pump (∼5%) and not by the intrinsic helium-transport properties of the plasma

  3. Special operations in the helium system, III-4

    Special operations in the helium system are: pouring helium form the low pressure reservoir to the high pressure reservoir by compressor with membrane, measuring the percent of hydrogen-oxygen gas and percent of free deuterium by manual gas analyzer, measurement of deuterium content, adding helium into the cover gas system, adding oxygen into the helium system, control of hydrogen-oxygen gas increase rate bypassing the contact device, activating the automated analyzer of percent of hydrogen-oxygen gas in helium and activating the automated analyzer of percent of air in helium

  4. Development of new technology in helium refrigerator

    For the practical use of nuclear fusion apparatuses, the adoption of superconducting magnets is unavoidable, and as the additional effective heating method of plasma, neutral beam injection is regarded as important. For superconducting magnets and the cryopumps for NB1, helium liquefying refrigerators are required to produce extremely low temperature close to absolute zero. In Hitachi Ltd., the development of the large helium liquefying refrigerator of expansion turbine type has been advanced early, and in 1968, No.1 machine, and in 1979, No.2 machine with improved reliability and operational performance were developed. So far, four machines were delivered for the projects of nuclear fusion, accelerators and others. As the technical development, in addition to the development of expansion turbines, the development of such peripheral equipment as transfer tubes, liquid helium pumps and automatic control has been forwarded in parallel. In this paper, the new technology related to these peripheral equipment is described. The superinsulator, FRP rod type spacers and liquid nitrogen shield for transfer tubes, a centrifugal liquid helium pump with dynamic pressure gas bearings and the automatic control for a helium liquefying refrigerator using a Hitachi DSC-18 digital controller are reported. (Kako, I.)

  5. Film boiling heat transfer in liquid helium

    The experimental data on the film boiling heat transfer in liquid helium are required for investigating the stability of superconducting wires. On the other hand, liquid helium has the extremely different physical properties as compared with the liquids at normal temperature such as water. In this study, the experiments on pool boiling were carried out, using the horizontal top surface of a 20 mm diameter copper cylinder in liquid helium. For observing individual bubbles, the experiments on film boiling from a horizontal platinum wire were performed separately in liquid nitrogen and liquid helium, and photographs of floating-away bubbles were taken. The author pointed out the considerable upward shift of the boiling curve near the least heat flux point in film boiling from the one given by the Berenson's equation which has been said to agree comparatively well with the data on the film boiling of the liquids at normal temperature, and the reason was investigated. Consequently, a model for film boiling heat transfer was presented. Also one equation expressing the film boiling at low heat flux for low temperature liquids was proposed. It represents well the tendency to shift from Berenson's equation of the experimental data on film boiling at the least heat flux point for liquid helium, liquid nitrogen and water having extremely different physical properties. Some discussions are added at the end of the paper. (Wakatsuki, Y.)

  6. TRANSPARENT HELIUM IN STRIPPED ENVELOPE SUPERNOVAE

    Piro, Anthony L.; Morozova, Viktoriya S., E-mail: piro@caltech.edu [Theoretical Astrophysics, California Institute of Technology, 1200 E. California Blvd., M/C 350-17, Pasadena, CA 91125 (United States)

    2014-09-01

    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.

  7. Helium release from radioisotope heat sources

    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.

  8. Thermal analysis of a coaxial helium panel of a cryogenic vacuum pump for advanced divertor of DIII-D tokamak

    It is planned to install a 50,000 1/s cryogenic pump for particle removal in the D3-D tokamak. A critical component of this cryogenic pump will be a helium panel which has to be maintained at a liquid helium temperature. The outer surface area of the helium panel has an area of 1 m2 and consists of a 2.5 cm diameter, 10 m long tube. From design considerations, a coaxial geometry is preferable since it requires a minimum number of welds. However, the coaxial geometry also results in a counter flow heat exchanger arrangement, where the outgoing warm fluid will exchange heat with incoming cold fluid. This is of concern since the helium panel must be cooled from liquid nitrogen temperature to liquid helium temperature in less than 5 minutes for successful operation of the cryogenic pump. In order to analyze the thermal performance of the coaxial helium panel, a finite difference computer model of the geometry was prepared. The governing equations took into account axial as well as radial conduction through the tube walls. The variation of thermal properties was modeled. The results of the analysis showed that although the coaxial geometry behaves like a counter flow heat exchanger, within the operating range of the cryogenic pump a rapid cooldown of the helium panel from liquid nitrogen temperature to the operating temperature is feasible. A prototypical experiment was also performed at General Atomics (GA) which verified the concept and the analysis. 4 refs., 8 figs

  9. Cavity microstructure and kinetics during gas tungsten arc welding of helium-containing stainless steel

    It is well known that energetic neutron irradiation produces significant physical damage to crystalline solids by the displacement of atoms from their normal lattice sites. In addition, transmutation reactions generate foreign elements of which helium is known to induce intergranular embrittlement. Degradation of material properties by these processes plays a decisive role in limiting the useful life of nuclear reactor components. It is reasonable, therefore, to anticipate that the repair and replacement of degraded reactor components will be required. Such repair procedures are likely to require the use of joining processes such as gas tungsten arc (GTA) welding. Helium was implanted in type 316 stainless steel, through tritium decay, to levels of 0.18, 2.5, 27, 105, and 256 atomic parts per million (appm). Bead-on-sheet welds were then made using the GTA process. Intergranular cracking occurred in the heat-affected zones (HAZs) of specimens with helium concentrations equal to or greater than 2.5 appm. No such cracking was observed in helium-free control specimens or in specimens containing the lowest helium concentrations. In addition to the HAZ cracking, brittle, centerline cracking occurred in the fusion zone of specimens containing 105 and 256 appm helium. Transmission and scanning electron microscopy results indicated that both the HAZ cracking and centerline cracking in the fusion zone resulted from the stress-induced growth and coalescence of cavities initiated at helium bubbles on interfaces. For the HAZ case, the cavity growth rate is modeled and shown to predict the experimentally measured 1-second time lag between peak weld temperature and the onset of cracking

  10. Helium beam diagnostics for the estimation electron temperature and density in SST-1

    Supersonic helium beam Diagnostics is used to estimate edge electron density and temperature in tokamaks. Ratio of line emission intensities from neutral helium is used to estimate electron temperature and density. Temperature is estimated from the ratio of intensities (728.1 nm /706.3 nm) whereas density is estimated from ratio (668.1 nm/728.1 nm). We have designed and tested a supersonic helium beam injector for edge plasma temperature and density for SST-1 tokamak. The system consists of a supersonic injector and an imaging system. The emission is collected by the imaging system and optical fibers and an EMMCD coupled spectrograph is used to record the spectra from various spatial locations. The spatial resolution is around 5 mm. In a recent campaign in SST-1, we tried to estimate these parameters using the residual helium after the helium GDC. The spectrometer and detection system was calibrated and signal was optimized. The spectra were good enough to use these helium lines to estimate electron temperature and density with an integration time of 10 ms. The observed line ratios are compared with the line ratios obtained from CR model/Atomic Data and Analysis Structure (ADAS) to get an estimate of electron temperature and density. The estimated electron density is in the range of 5 x 1011 - 2 x 1012 cm-3 and electron temperature 30-55 eV. The obtained parameters provide reasonable estimates when compared with other diagnostics considering the diffusion and ionization of neutral helium inside the tokamak. (author)

  11. Behavior of helium gas in the LHD vacuum chamber

    In general, helium gas does not remain on vacuum chamber walls because of its small activation energy. However, outgassing of helium gas from the walls has been observed in the LHD plasma vacuum chamber with a very long time constant after helium glow discharge cleaning (GDC), and absorption of helium atoms has been observed in plasma discharge experiments using helium gas. The helium partial pressure before the daily experiments was determined only by the gas species of the last GDC. No dependence has been found between the helium partial pressure and the species of the fueling gas of the last plasma experiment fueling gas. Considering that the outgassing rate of the helium gas is almost the same each morning after He GDC, the retention of helium atoms in the wall after the GDC is almost at the same level. The concentration of helium atoms in the wall before the daily experiments is estimated. The outgassing rate after the GDC is 2x10-4 Pa m3/s and the concentration is 4.7x1016 atoms/cm2. These results are of the same order as in another experiments. During helium gas plasma experiments, about a half of the amount of the inlet gas disappears with the missing particles remaining in the wall. The stainless steel wall, which is saturated with He GDC, may still have the capacity to trap high energy helium atoms. However, the energy dependence of trapping helium atoms presently is not clear

  12. The muonic helium lamb shift experiment

    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.

  13. A rotating liquid helium transfer system

    This chapter demonstrates the successful operation of a stable transfer system suitable for fault worthy superconducting generators. A turbine type flowmeter for liquid helium has been developed and successfully operated. The transfer system was cooled to helium temperature and the transfer of liquid was initiated without any detectable pressure oscillations or surges. Transfer system losses were computed for subcooled, two-phase and superheated helium transfer and various mass flow rates up to 70 L/h. Transfer losses are shown to be a strong function of angular velocity, void fraction and mass flow rate. It is suggested that to minimize losses and oscillation a vapor separator should be used at the transfer system inlet to control void fraction in the transfer stream

  14. Extended quintessence and the primordial helium abundance

    Chen, Xuelei; Scherrer, Robert J.; Steigman, Gary

    2001-06-15

    In extended quintessence models, a scalar field which couples to the curvature scalar R provides most of the energy density of the universe. We point out that such models can also lead naturally to a decrease in the primordial abundance of helium-4, relieving the tension which currently exists between the primordial helium-4 abundance inferred from observations and the amount predicted by standard big bang nucleosynthesis corresponding to the observed deuterium abundance. Using negative power-law potentials for the quintessence field, we determine the range of model parameters which can lead to an interesting reduction in the helium-4 abundance, and we show that it overlaps with the region allowed by other constraints on extended quintessence models.

  15. Helium behaviour in nuclear waste materials

    Waste conditioning matrices like synthetic zirconolite (CaZrTi2O7) were fabricated and doped with either the short-lived alpha-emitters 238Pu or 244Cm, or with 239Pu to generate various amounts of helium and of alpha-damage. The samples were annealed in a Knudsen cell, and the helium desorption profiles interpreted in conjunction with parallel radiation damage and previous annealing behaviour studies. To understand the long term behaviour of spent nuclear fuel, UO2 samples doped with the alpha-emitters 233U, 238Pu have been investigated by transmission electron microscopy (TEM), by XRD and by thermal desorption spectroscopy. The release of helium has been explained by the recrystallization of amorphized zirconolite on one hand and partially during alpha-damage recovery in the case of the spent fuel. This study mostly highlights the correlation between restructuring of damaged materials and gas release

  16. Evolution of dopant-induced helium nanoplasmas

    Two-component nanoplasmas generated by strong-field ionization of doped helium nanodroplets are studied in a pump-probe experiment using few-cycle laser pulses in combination with molecular dynamics simulations. High yields of helium ions and a pronounced resonance structure in the pump-probe transients which is droplet size dependent reveal the evolution of the dopant-induced helium nanoplasma with an active role for He shells in the ensuing dynamics. The pump-probe dynamics is interpreted in terms of strong inner ionization by the pump pulse and resonant heating by the probe pulse which controls the final charge states detected via the frustration of electron-ion recombination. (paper)

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

    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

  18. Helium-jet ion guide for an on-line isotope separator

    A new method based on helium-jet techniques permits primary recoil ions produced in radioactive decay or in nuclear reactions to be run directly through a mass separator. Test results with a 227Ac source give promise of qualities complementary to those obtained with conventional ion sources. Thus, 69 +- 5 per cent of the recoil particles transported with pure, commercial helium are positive ions, and 66 +- 5 per cent of them are mass separated. Nearly equal efficiencies are expected for most chemical elements and compounds. The mass spectra are remarkably free from groups caused by impurities. The shortest achievable separation time is estimated to be of the order of one millisecond. (author)

  19. Helium burning in moderate-mass stars

    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 outside of it may be the most promising tool.

  20. Hydrogen and helium adsorption on potassium

    A previous quartz microbalance study of adsorption of helium on sodium indicates that the inert layer is surprisingly small. Similar experiments with hydrogen on sodium show layer by layer growth below a temperature of 7K. These results motivated the authors to extend the experiments to lower temperatures. A suitable apparatus, capable of reaching 0.45 K, while still enabling them to do in situ alkali evaporation, has been constructed. The authors will report on the results of microbalance adsorption experiments of helium and hydrogen on potassium

  1. Helium damage in austenitic stainless steels

    Helium produced by tritium decay was first shown to embrittle austenitic stainless steel at ambient temperature in tensile specimens of Nitronic-40 steel (Armco, Inc.). A long-term study was initiated to study this form of helium damage in five austenitic alloys. Results from this study have been analyzed by the J-integral technique and show a decrease in ductile fracture toughness with increasing He-3 concentration. Sustained-load cracking tests indicate that the stress intensity required to initiate and propagate a crack also decreases with increasing He-3 concentration. 9 figures, 3 tables

  2. Helium-induced reactions in astrophysics

    Helium-induced reactions play a crucial role in stellar nucleosynthesis. Carbon and oxygen are produced mainly during the helium-burning phase by the chain of reactions 8Be(α, γ + e+e-)12C(α, γ)16O. The first step, often called triple-α capture, was proposed by Hoyle to bypass the mass stability gap at 8Be. The second step gives rise to the largest uncertainty in most of the calculated stellar abundances. Later α-captures on 13C are believed to be a major source of s-process neutrons. The status of each of these important reactions is reviewed here

  3. Plastic dewar for pressurized superfluid helium

    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)

  4. Stopping Power of Solid Argon for Helium Ions

    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 theoretical description, calculated shell corrections based on the Lindhard-Scharff model are in good agreement...

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

    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)

  6. Theory of the Lamb shift in muonic helium ions

    The Lamb shift (2P1/2-2S1/2) in muonic helium ions (μ23)+, (μ2/4He)+ is calculated taking into account the contributions of the order of α3, α4, α5, and α6. Special attention is paid to corrections for the polarization of the vacuum, as well as the structure and recoil of the nucleus. Numerical values 1259.8583 meV ((μ23He)+) and 1379.1107 meV ((μ24He)+) obtained for the shifts can be considered reliable estimates when compared to the experimental data of the CREMA collaboration

  7. Liquid helium target for investigations with electron and photon beams

    A liquid helium target, designed for investigations of electro- and photodisintegration of the lightest nuclei is described. The target temperature of 1.5K is provided by pumping out of 4He vapors. 100l of gaseous 3He are used; the liquid 4He flow rate is 1l/h; the time required to put the target into operation is 8h; the time needed to change the working liquid is 2 h. The tests with the target have demonstrated its reliability and high stability of the cryogenic liquid density during a long period of irradiation by photon and high energy electron beams

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

    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)

  9. Penning collisions of laser-cooled metastable helium atoms

    Pereira Dos Santos, F.; Perales, F.; Léonard, J.; Sinatra, A.; Wang, Junmin; Saverio Pavone, F.; Rasel, E.; Unnikrishnan, C. S.; Leduc, M.

    2001-04-01

    We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state ( 23P2) and metastable state ( 23S1) populations is also investigated. From these results we infer a rather uniform rate constant Ksp = (1+/-0.4)×10-7 cm3/s.

  10. Study of the amorphization of surface silicon layers implanted by low-energy helium ions

    Lomov, A. A.; Myakon'kikh, A. V.; Oreshko, A. P.; Shemukhin, A. A.

    2016-03-01

    The structural changes in surface layers of Si(001) substrates subjected to plasma-immersion implantation by (2-5)-keV helium ions to a dose of D = 6 × 1015-5 × 1017 cm-2 have been studied by highresolution X-ray diffraction, Rutherford backscattering, and spectral ellipsometry. It is found that the joint application of these methods makes it possible to determine the density depth distribution ρ( z) in an implanted layer, its phase state, and elemental composition. Treatment of silicon substrates in helium plasma to doses of 6 × 1016 cm-2 leads to the formation of a 20- to 30-nm-thick amorphized surface layer with a density close to the silicon density. An increase in the helium dose causes the formation of an internal porous layer.

  11. Jet Pump for Liquid Helium Circulation Through the Fast Cycling Magnets of Nuclotron

    Agapov, Nikolay; Emelianov, Nikita; Mitrofanova, Julia; Nikiforov, Dmitry

    Nuclotron is the first fast cycling superconducting synchrotron intended for the acceleration of high-energy nuclei and heavy ions. Its cryogenic system includes two helium refrigerators with a total capacity of 4000 W at 4.5 K. The 251.5 m long accelerator ring consists of 144 superconducting dipole and quadruple magnets. The magnets connected in parallel are refrigerated by a two-phase flow of boiling helium. In order to increase liquid helium flow directed to the superconducting magnets, jet pumps are used. We explain theoretical and experimental results that allow one to determinate main technical specifications and optimal geometric dimensions of the jet pumps. The experience of using this device and corresponding flow diagrams are described.

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

    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.

  13. Density functional theory study on helium behavior in aluminum

    The energies of helium atoms in the interstitial, vacancy, grain boundary, and dislocation sites in aluminum lattice in the presence of large quantity of helium atoms, have been calculated with density functional theory (DFT), and the helium atom behavior has also been predicted theoretically. The results show that vacancies are the preferential sites for helium atoms inside the unit cell. But in the view of the whole lattice, grain boundaries are the most favorable sites for containing helium atoms than vacancies and dislocations. In the two interstitial sites in aluminum unit cells, helium atoms prefer to occupying the tetrahedron sites. The migration energy of interstitial helium atoms is so small that it is easy to accumulate or be trapped by vacancies, grain boundaries and dislocations through the migration for interstitial helium atoms. (authors)

  14. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 300K. The nucleation and growth of helium bubble has been simulated up to 50 helium atoms. The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve. The titanium cohesion is based on the tight binding scheme derived from the embedded atom method, and the heliumtitanium interaction is characterized by fitted potential in the form of a Lennard-Jones function. The pressure in small helium bubbles is approximately calculated. The simulation results show that the pressure will decrease with the increasing bubble size, while increase with the increasing helium atoms. An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted. (condensed matter: structure, mechanical and thermal properties)

  15. Adsorption of Helium Atoms on Two-Dimensional Substrates

    Burganova, Regina; Lysogorskiy, Yury; Nedopekin, Oleg; Tayurskii, Dmitrii

    2016-01-01

    The study of the adsorption phenomenon of helium began many decades ago with the discovery of graphite as a homogeneous substrate for the investigation of physically adsorbed monolayer films. In particular, helium monoatomic layers on graphite were found to exhibit a very rich phase diagram. In the present work we have investigated the adsorption phenomenon of helium atoms on graphene and silicene substrates by means of density functional theory with Born-Oppenheimer approximation. Helium-substrate and helium-helium interactions were considered from first principles. Vibrational properties of adsorbed monolayers have been used to explore the stability of the system. This approach reproduces results describing the stability of a helium monolayer on graphene calculated by quantum Monte Carlo (QMC) simulations for low and high coverage cases. However, for the moderate coverage value there is a discrepancy with QMC results due to the lack of helium zero point motion.

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

    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.

  17. Overview of recent studies and modifications being made to RHIC to mitigate the effects of a potential failure to the helium distribution system

    Tuozzolo, J.; Bruno, D.; DiLieto, A.; Heppner, G.; Karol, R.; Lessard,E.; Liaw, C-J; McIntyre, G; Mi, C.; Reich, J.; Sandberg, J.; Seberg, S.; Smart, L.; Tallerico, T.; Theisen, C.; Todd, R.; Zapasek R.

    2011-03-28

    In order to cool the superconducting magnets in RHIC, its helium refrigerator distributes 4.5 K helium throughout the tunnel along with helium distribution for the magnet line recoolers, the heat shield, and the associated return lines. The worse case for failure would be a release from the magnet distribution line which operates at 3.5 to 4.5 atmospheres and contains the energized magnet but with a potential energy of 70 MJoules should the insulation system fail or an electrical connection opens. Studies were done to determine release rate of the helium and the resultant reduction in O{sub 2} concentration in the RHIC tunnel and service buildings. Equipment and components were also reviewed for design and reliability and modifications were made to reduce the likelihood of failure and to reduce the volume of helium that could be released.

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

    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 τ*He=0.4s and τ*He/τE=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)

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

    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

  20. Gas porosity evolution and ion-implanted helium behavior in reactor ferritic/martensitic and austenitic steels

    The peculiarities of gas porosity formation and helium retention and release in reactor ferritic/martensitic EP-450 and EP-450-ODS and austenitic ChS-68 steels are investigated by transmission electron microscopy and helium thermal desorption spectrometry (HTDS). The samples were irradiated by 40 keV He+ ions up to a fluence of 5 · 1020 m−2 at 293 and 923 K. An nonuniform distribution of helium bubbles and high-level gas swelling in ferritic/martensitic steels were found at high-temperature helium implantation. The same irradiation conditions result in formation of uniformly distributed helium bubbles and low-level swelling in ChS-68 steel. Temperature range of helium release from EP-450-ODS steel was considerably wider in comparison to HTDS-spectra of the EP-450 steel. A considerable quantity of helium is released from ODS steel in the high-temperature range after the main peak of the HTDS-spectrum

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

    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 explained by the gr...

  2. A new helium gas recovery and purification system

    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.)

  3. Helium sources and recovery processes - with special reference to India

    Helium plays an important role in a variety of processes. Its only widely exploited source is natural gas with a helium content of 1-8%. Postulated, increased demand has stimulated interest in both novel sources and extraction techniques. Existing and new methods of helium recovery from natural gas are discussed with particular attention pair to pilot plants for helium extraction from monazite mineral and thermal springs in India. (author)

  4. The effect of boron on the development of helium induced creep embrittlement in Type 316 stainless steel

    Specimens from three casts of AISI type 316 stainless steel were irradiated at 325 K to four thermal fluence levels between 2.4 x 1018 and 0.8 x 1024 nm-2, resulting in helium contents between approx. 1.5 x 10-5 and 8 atomic parts per million (appm). Specimens were subsequently creep tested in air at 191 MPa and 900 K in shielded facilities. The threshold helium content for the onset of embrittlement was different for each cast of steel and varied between approx. 10-4 and approx. 10-2 appm. The reduction in creep rupture time and ductility at the maximum helium content of 4 to 8 appm varied between 0.05 and 0.6 of the unirradiated values and is attributed to the helium formed by the reaction of thermal neutrons with the B10 isotope. A failure model based on the growth of wedge cracks is discussed. (author)

  5. Adsorption of krypton from helium by low temperature charcoal

    Adsorption of krypton from helium by charcoal at temperatures from -1000C to -1400C was experimentally investigated to verify adsorption system design methods and to determine effects of regeneration for the Gas Purification System of the Liquid-Metal Fast Breeder Reactor. Helium with two krypton concentrations, traced by krypton-85 at 0.0044 ?Ci/cm3, was passed through a 1/2-inch diameter, three-inch long trap packed with coconut charcoal. Breakthrough curves were measured by continuously recording the activity of the effluent gas using a sampler with a krypton-85 detection limit of about 5 x 10-7 ?Ci/cm3. Experimental breakthrough curves with continuous feed for both concentrations and for superficial gas velocities of 5 to 28 cm/sec were closely fitted when the pore diffusion term was omitted from the Anzelius linear equilibrium adsorption model indicating that the adsorption process for this system was controlled by gas phase mass transport kinetics. Adsorption capacities determined in these experiments at -1400C agreed closely with published data. A discontinuity, however, was observed in the krypton adsorption coefficient between -100 and -1200C. This discontinuity may be caused by capillary condensation of krypton in the charcoal pores. Breakthrough times for pulse experiments at 400 ppM (vol.) krypton concentration were several times greater than breakthrough for continuous feed experiments at equivalent conditions. The differences in breakthrough times indicate that the adsorption isotherms are non-linear in this concentration range. Regeneration experiments showed that purging with helium at room temperature for 16 hours was inadequate, since lower breakthrough times were obtained after this treatment. Regeneration under vacuum at 1000C or 2000C for 16 hours resulted in satisfactory regeneration (i.e., no reduction in breakthrough times occurred in subsequent runs). (U.S.)

  6. Modified tritium trick technique for doping vanadium alloys with helium

    A modified tritium trick technique was used to implant three different levels of 3He in V-15Cr-5Ti (wt %) and Vanstar-7 specimens before irradiation in the Fast Flux Test Facility (FFTF). The modifications include: (1) wrapping of the specimens with tantalum foil to minimize oxygen contamination, and (2) a 4000C decay-time treatment to prevent vanadium tritide formation and to produce a 3He bubble distribution similar to that produced during elevated temperature irradiation. Preliminary results show that both modifications were successful. However, the tritium removal step at 7000C was probably too excessive, especially at higher helium levels, because large 3He bubbles formed in the grain boundaries and several embrittled the V-15Cr-5Ti alloy. Reduction of the tritium removal step to 4000C should alleviate this problem. Vanstar-7 specimens consistently absorbed about half as much tritium, and subsequently contained half as much 3He as V-15Cr-5Ti. Implanting 3He in vanadium alloys via the tritium trick offers a convenient technique to study the mechanism of helium embrittlement without irradiation and should provide a rapid screening method to help develop embrittlement-resistant vanadium alloys

  7. Existence of an Ericson regime in stretched helium

    The method of complex rotation is used to establish the existence of a regime of strongly overlapping resonances (the Ericson regime) in stretched helium, a collinear model of the helium atom. The existence of an Ericson regime in helium is conjectured and a method for proving its existence experimentally is suggested. copyright 1996 The American Physical Society

  8. Surface excitations in thin helium films on silica aerogel

    Lauter, H J; Puchkov, A V; Skomorokhov, A; Godfrin, H; Klier, J; Leiderer, P

    2002-01-01

    First measurements are reported on pure surface excitations in thin superfluid sup 4 He 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. (orig.)

  9. Observation of visible emission from the molecular helium ion in the afterglow of a dense helium Z-pinch plasma

    The authors present the results of axial and radial time resolved visible emission spectroscopy from the afterglow of a dense helium Z-pinch. These results show that the visible emissions in the pinch afterglow are dominated by line emissions from molecular helium and He II. Axial spectroscopy measurements show the occurrence of several absorption bands which cannot be identified as molecular or atomic helium nor impurities from the discharge chamber materials. The authors believe that these absorption bands are attributable to the molecular helium ion which is present in the discharge. The molecular ion has been observed by others in low pressure and temperature helium discharges directly by means of mass spectrometry and indirectly by the presence of helium atoms in the 2/sup 3/S state, (the He 2/sup 3/S state is believed to result from molecular helium ion recombination). However, the molecular helium ion has not previously been observed spectroscopically

  10. Relation between the conditions of helium ion implantation and helium void equilibrium parameters

    The conditions of helium thermodynamic equilibrium in a system of voids produced by helium ion bombardment of a metal sample are studied. As an initial equation for description of the equilibrium the Clapeyron equation was used. The equation is obtained relating basic parameters of helium voids (average diameter and density) to irradiation parameters (dose, ion energy (straggling)) and properties of the metal (surface tension coefficient, yield strength). Comparison of the calculations with experimental data on helium in nickel found in literature shows that the equation yields satisfactory resutls for the dose range 1.1016-1x1017 cm-2 and temperatures T < or approximately 1100 K. Divergence from experiment does not exceed approximately 30%

  11. Gaussian Basis Set Optimization for Excited Helium and Helium-like Ions

    Šmydke, Jan; Kaprálová-Žďánská, Petra Ruth

    Mariapfarr : Univerzity of Graz, 2012. [Central European Symposium on Theoretical Chemistry /11./. 25.09.2011-28.09.2011, Mariapfarr] Institutional support: RVO:61388955 Keywords : helium * Gaussian basis set oprimization Subject RIV: CF - Physical ; Theoretical Chemistry

  12. Resource letter SH-1: superfluid helium

    The resource letter covers the general subject of superfluid helium and treats 3He and 3He--4He mixtures as well as 4He. No effort has been made to include the fascinating experiments on either solid helium or the equally fascinating work on adsorbed helium where the helium coverage is below that necessary for superfluidity. An earlier resource letter by C. T. Lane [Am. J. Phys. 35, 367 (1967)] may be consulted for additional comments on some of the cited earlier manuscripts, but the present work is self-contained and may be used independently. Many high-quality research reports have not been cited here. Rather, the author has tried in most cases to include works particularly readable or relevant. There is a relatively heavy emphasis on experimental references. The primary reason is that these works tend to be more generally readable. No doubt some works that might have been included, have not, and for this the author takes responsibility with apology. Articles selected for incorporation in a reprint volume (to be published separately by the American Association of Physics Teachers) are marked with an asterisk(*). Following each referenced work the general level of difficulty is indicated by E, I, or A for elementary, intermediate, or advanced

  13. Tritium and helium-3 in metals

    The book surveys recent results on the behaviour of tritium and its decay product helium-3 metals. In contrast to many earlier books which discuss the properties of the stable hydrogen isotopes without mentioning tritium, this book reviews mainly the results on tritium in metals. Due to the difficulties in preparing metal tritide samples, very important quantities such as diffusivity, superconductivity, solubility, etc. have only been determined very recently. The book not only presents the measured tritium data, but also the isotopic dependency of the different physical properties by comparing H, D and T results. A chapter is devoted to helium-3 in metals. Aspects such as helium release, generation of helium bubbles, swelling, and change of the lattice parameter upon aging are discussed. The book provides the reader with up-to-date information and deep insight into the behaviour of H, D, T and He-3 in metals. Further important topics such a tritium production, its risks, handling and discharge to the environment are also addressed

  14. Conceptual design of helium experimental loop

    In a future demonstration fusion power station (DEMO), helium is envisaged as coolant for plasma facing components, such as blanket and dive,or. All these components have a very complex geometry, with many parallel cooling channels, involving a complex helium flow distribution. Test blanket modules (TBM) of this concept will under go various tests in the experimental reactor ITER. For the qualification of TBM, it is indispensable to test mock-ups in a helium loop under realistic pressure and temperature profiles, in order to validate design codes, especially regarding mass flow and heat transition processes in narrow cooling channels. Similar testing must be performed for DEMO blanket, currently under development. A Helium Experimental Loop (HELOOP) is planed to be built for TBM tests. The design parameter of temperature, pressure, flow rate is 550 degree C, 10 MPa, l kg/s respectively. In particular, HELOOP is able to: perform full-scale tests of TBM under realistic conditions; test other components of the He-cooling system in ITER; qualify the purification circuit; obtain information for the design of the ITER cooling system. The main requirements and characteristics of the HELOOP facility and a preliminary conceptual design are described in the paper. (authors)

  15. Two-photon ionization of metastable helium

    There have been relatively few investigations of multiphoton ionization from metastable helium. Of particular interest has been the work of Haberland et al. 1987 and Haberland and Oschwald 1988. In both the 1987 and 1988 papers they have described the two photon ionization of metastable helium. In each of these studies they have reported the occurrence of unexplained structure along the wings of their resonance profiles. Upon the performance of similar measurements by this study, the unexplained structure is not seen and the agreement of the experiment's measurements with the theoretical shape of the resonance curves has been good. To experimentally verify these resonance effects, the author has used a tunable dye laser in conjunction with a time of flight mass spectrometer to create and detect ions from metastable helium by two-photon absorption. The study includes the description of the laser, electron gun assembly for metastable helium creation, and the time of flight mass spectrometer. A discussion of the theory of multiphoton processes is included along with the discussion of the data, its reduction and analysis, and a comparison with theoretical prediction. This study has not only involved the acquisition of definitive atomic spectra data sets, but has also established a facility for resonant ionization spectroscopy at The American University

  16. Mixed helium-3 - helium-4 calorimeter. Very low temperature calorimetry; Calorimetre mixte a helium-3 et helium-4. Calorimetrie a tres basse temperature

    Testard, O. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1966-06-01

    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) [French] On decrit un calorimetre a double enceinte utilisant comme fluide cryogenique l'helium-4 et l'helium-3 et permettant de varier continuement la temperature de 0,35 K a 4,2 K. L'utilisation d'un regulateur thermique electrique ainsi que celle d'hydrogene, liquide permettent d'etendre cette gamme jusqu'a 30 K environ. Dans une deuxieme partie, on passe en revue les diverses methodes de mesure des chaleurs specifiques. La methode concrete utilisee dans l'appareil precedemment decrit est exposee en detail. Les difficultes inherentes a l'utilisation de gaz d'echange comme agent de contact thermique ont ete levees par la mise en oeuvre de pompes a adsorbant. (auteur)

  17. An asteroseismic signature of helium ionization

    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 $\

  18. Atmospheric helium and geomagnetic field reversals.

    Sheldon, W. R.; Kern, J. W.

    1972-01-01

    The problem of the earth's helium budget is examined in the light of recent work on the interaction of the solar wind with nonmagnetic planets. It is proposed that the dominant mode of helium (He4) loss is ion pumping by the solar wind during geomagnetic field reversals, when the earth's magnetic field is very small. The interaction of the solar wind with the earth's upper atmosphere during such a period is found to involve the formation of a bow shock. The penetration altitude of the shock-heated solar plasma is calculated to be about 700 km, and ionization rates above this level are estimated for a cascade ionization (electron avalanche) process to average 10 to the 9th power ions/sq cm/sec. The calculated ionization rates and the capacity of the solar wind to remove ionized helium (He4) from the upper atmosphere during geomagnetic dipole reversals are sufficient to yield a secular equilibrium over geologic time scales. The upward transport of helium from the lower atmosphere under these conditions is found to be adequate to sustain the proposed loss rate.

  19. Helium and Sulfur Hexafluoride in Musical Instruments

    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. Helium interaction with tungsten polycrystalline surface

    The technique is described of thermophysical experiment using Auger spectrometer for the analysis of the surface directly under the experimental conditions. The results are presented on the energy accomodation of helium on polycrystalline tungsten at different degrees of its surface purification

  1. Forbidden transitions in the helium atom

    Lach, G; Lach, Grzegorz; Pachucki, Krzysztof

    2001-01-01

    Nonrelativistically forbidden, single-photon transition rates between low lying states of the helium atom are rigorously derived within quantum electrodynamics theory. Equivalence of velocity and length gauges, including relativistic corrections is explicitly demonstrated. Numerical calculations of matrix elements are performed with the use of high precision variational wave functions and compared to former results.

  2. Messer to provide helium for LHC

    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.

  3. Messer to provide helium for LHC project

    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.

  4. Development of helium isotopic database in Japan

    We constructed “Helium Isotopic Database in Japan”, which includes isotope ratios of noble gases and chemical compositions of gas samples collected from hot springs and drinking water wells. The helium isotopes are excellent natural tracers for indicating the presence of mantle derived volatiles, because they are chemically inert and thus conserved in crustal rock-water systems. It is common knowledge that mantle degassing does not occur homogeneously over the Earth's surface. The 3He/4He ratios higher than the typical crustal values are interpreted to indicate that transfer of mantle volatiles into the crust by processes or mechanisms such as magmatic intrusion, faulting. In particular the spatial variation of helium isotope ratios could provide a valuable information to identify volcanic regions and tectonically active areas. The database was compiled geochemical data of hot spring gas etc. from 108 published papers. As a result of the data compiling, the database has 1728 helium isotopic data. A CD-ROM is attached as an appendix. (author)

  5. Electron scattering in a helium Debye plasma

    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.

  6. High-resolution Auger spectroscopy on 79 MeV Ar5+, 89 MeV Ar6+, and 136 MeV Ar7+ ions after excitation by helium

    In this thesis the atomic structure of highly excited Ar6+ and Ar7+ ions was studied. For this 79 MeV Ar5+, 89 MeV Ar6+, and 136 MeV Ar7+ ions of a heavy ion accelerator were excited by a He gas target to autoionizing states and the Auger electrons emitted in the decay were measured in highly-resolving state. The spectra were taken under an observational angle of zero degree relative to the beam axis in order to minimize the kinematical broadening of the Auger lines. (orig./HSI)

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

    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.

  8. Physiological response of rats to delivery of helium and xenon: implications for hyperpolarized noble gas imaging

    Ramirez, M. P.; Sigaloff, K. C.; Kubatina, L. V.; Donahue, M. A.; Venkatesh, A. K.; Albert, M. S.; ALbert, M. S. (Principal Investigator)

    2000-01-01

    The physiological effects of various hyperpolarized helium and xenon MRI-compatible breathing protocols were investigated in 17 Sprague-Dawley rats, by continuous monitoring of blood oxygen saturation, heart rate, EKG, temperature and endotracheal pressure. The protocols included alternating breaths of pure noble gas and oxygen, continuous breaths of pure noble gas, breath-holds of pure noble gas for varying durations, and helium breath-holds preceded by two helium rinses. Alternate-breath protocols up to 128 breaths caused a decrease in oxygen saturation level of less than 5% for either helium or xenon, whereas 16 continuous-breaths caused a 31.5% +/- 2.3% decrease in oxygen saturation for helium and a 30.7% +/- 1. 3% decrease for xenon. Breath-hold protocols up to 25 s did not cause the oxygen saturation to fall below 90% for either of the noble gases. Oxygen saturation values below 90% are considered pathological. At 30 s of breath-hold, the blood oxygen saturation dropped precipitously to 82% +/- 0.6% for helium, and to 76.5% +/- 7. 4% for xenon. Breath-holds longer than 10 s preceded by pre-rinses caused oxygen saturation to drop below 90%. These findings demonstrate the need for standardized noble gas inhalation procedures that have been carefully tested, and for continuous physiological monitoring to ensure the safety of the subject. We find short breath-hold and alternate-breath protocols to be safe procedures for use in hyperpolarized noble gas MRI experiments. Copyright 2000 John Wiley & Sons, Ltd.

  9. Modification of the Helium Supply System with a PCHE type reciprocator

    In the HCCR TBM, high pressure (8 MPa) and high temperature (300-500 .deg. C) helium gas is considered as a coolant, and therefore a helium cooling system (HCS), one of the essential auxiliary systems of the KO HCCR TBM, has been designed. The scaled-down helium supply system (HeSS, Ref. 5) was constructed in early 2012 to validate the HCS design and system design code, GAMMA. However, more than 2 MW of heating power was required to heat up a 1.5 kg/s mass flow of helium gas (for full scale HeSS) from room temperature to 300 .deg. C. In the present study, a recuperator is considered for the HeSS facility to solve the heating issues and the HeSS facility is modified. A 1/3 scaled-down helium supply system was constructed at KAERI for the development of manufacturing techniques and operational experience of the HCS of the HCCR TBM. The PCHE type recuperator was added in the HeSS to dramatically improve the energy efficiency and reduce the required electrical power of the helium pre-heater. The modified HeSS was linked with KoHLT-EB to supply high heat flux (∼0.5 MW/m2) to validate the design and manufacturing techniques for the first wall of the HCCR TBM and obtain thermal-hydraulic experimental data for verification and validation of the GAMMA code. The experiment and code validation are scheduled to start in mid-2013 with the first wall mock-up under normal ITER operation condition

  10. Production of the hydrated electron in the radiolysis of water with helium ions

    The scavenged yield of the hydrated electron has been determined in the radiolysis of water with 2-22-MeV helium ions by measuring the production of ammonia from glycylglycine. Glycylglycine concentrations were 1, 0.1, 0.01, and 0.001 M, which correspond to hydrated electron lifetimes of 3 ns to 3 μs, respectively. Differential hydrated electron yields were obtained from the observed energy dependencies, and for 1 M glycylglycine they ranged from 1.76 to 3.09 molecules/100 eV for 5-20-MeV helium ions, respectively. These values are slightly larger than the corresponding integral yields of 1.51-2.20 molecules/100 eV, respectively, but smaller than the yield of 3.81 found with fast electrons. In 0.001 M glycylglycine solutions the integral scavenged yield of the hydrated electron varies less than 1% per MeV of helium ion energy. At this concentration it was found that for 5-MeV helium ions the differential hydrated electron yield was 0.145 and the integral yield was 0.098 molecules/100 eV. These values are substantially less than the value of 2.47 molecules/100 eV found with fast electrons indicating the importance of intratrack reactions with helium ions in the nanosecond to microsecond time scale. It appears that the scavenged yields of hydrated electrons approach constant values with decreasing glycylglycine concentration for all helium ion energies studied. 34 refs., 5 figs

  11. Engineering Sensitivity Improvement of Helium Mass Spectrometer Leak Detection System by Means Global Hard Vacuum Test

    The engineering sensitivity improvement of Helium mass spectrometer leak detection using global hard vacuum test configuration has been done. The purpose of this work is to enhance the sensitivity of the current leak detection of pressurized method (sniffer method) with the sensitivity of 10-3 ∼ 10-5 std cm3/s, to the global hard vacuum test configuration method which can be achieved of up to 10-8 std cm3/s. The goal of this research and development is to obtain a Helium leak test configuration which is suitable and can be used as routine bases in the quality control tests of FPM capsule and AgInCd safety control rod products. The result is an additional instrumented vacuum tube connected with conventional Helium mass spectrometer. The pressure and temperature of the test object during the leak measurement are simulated by means of a 4.1 kW capacity heater and Helium injection to test object, respectively. The addition of auxiliary mechanical vacuum pump of 2.4 l/s pumping speed which is directly connected to the vacuum tube, will reduce 86 % of evacuation time. The reduction of the measured sensitivity due to the auxiliary mechanical vacuum pump can be overcome by shutting off the pump soon after Helium mass spectrometer reaches its operating pressure condition. (author)

  12. Design, fabrication, and testing of helium cooled high heat flux module

    General Atomics (GA) has considerable expertise in use of helium cooling due to its high temperature gas cooled reactor experience. In order to prove the feasibility of helium cooling at high heat flux levels of above 5 MW/m2, GA designed, fabricated, and tested a helium cooled module. The module was sized to have a heat flux surface of 25 mm wide and 80 mm long due to test setup limitations on maximum deposited power. The module was made from dispersion strengthened copper. The fabricated geometry was slightly different than the optimized design due to constraints of machining. The fabrication was done by electro discharge matching. The testing was carried out at the electron beam test facility of Sandia National Laboratory, Albuquerque (SNLA). It was necessary to reduce the area of heat flux deposition at higher heat flux due to limitations in the power capability of the electron beam. It is estimated that a heat transfer coefficient of about 40,000 W/m2-C was achieved during these tests. The pumping power calculated from flow rate and pressure drop measurement was about 160 W for the test with 9 MW/m2 surface heat flux, which was less than 1% of the 18 kW power removed. As a result of this effort the authors conclude that, helium cooling of high heat flux components is feasible without requiring a very large helium pressure or a large pumping power

  13. Helium irradiation effects on tritium retention and long-term tritium release properties in polycrystalline tungsten

    Nobuta, Y., E-mail: y-nobuta@eng.hokudai.ac.jp [Laboratory of Plasma Physics and Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Hatano, Y.; Matsuyama, M.; Abe, S. [Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555 (Japan); Yamauchi, Y.; Hino, T. [Laboratory of Plasma Physics and Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628 (Japan)

    2015-08-15

    DT{sup +} ion irradiation with energy of 0.5 and 1.0 keV was performed on helium pre-irradiated tungsten and the amount of retained tritium and the long-term release of retained tritium in vacuum was investigated using an IP technique and BIXS. Tritium retention and long-term tritium release were significantly influenced by helium pre-irradiation. The amount of retained tritium increased until it reached 1 × 10{sup 17} He/cm{sup 2}, and at 1 × 10{sup 18} He/cm{sup 2} it became smaller compared to 1 × 10{sup 17} He/cm{sup 2}. The amount of retained tritium in tungsten without helium pre-irradiation largely decreased after several weeks preservation in vacuum, and the long-term release rate during vacuum preservation was retarded by helium pre-irradiation. The results indicate that the long-term tritium release and the helium irradiation effect on it should be taken into account for more precise estimation of tritium retention in the long-term use of tungsten in fusion devices.

  14. Small-angle X-ray scattering measurements of helium-bubble formation in borosilicate glass

    Small-angle X-ray scattering (SAXS) measurements have been performed to study helium-bubble formation in borosilicate glass. Helium was introduced by He+ implantation over an energy range of 1 to 2 MeV to give a uniform distribution over ∝1 μm depth. The implanted dose was varied from 9 x 1013 to 2.8 x 1016 ions cm-2, corresponding to a local concentration range of 40 to 11200 atomic parts per million (a.p.p.m.) averaged over the implantation depth. The SAXS response was fit with the Percus-Yevick hard-sphere interaction potential to account for interparticle interference. The fits yield helium-bubble radii and helium-bubble volume fractions that vary from 5 to 15 Aa and from 10-3 to 10-1, respectively, as the dose increased from 9 x 1013 to 2.8 x 1016 cm-2. The SAXS data are also consistent with maximum helium solubility with respect to bubble formation between 40 and 200 a.p.p.m. in the borosilicate glass matrix. (orig.)

  15. Helium irradiation effects on tritium retention and long-term tritium release properties in polycrystalline tungsten

    DT+ ion irradiation with energy of 0.5 and 1.0 keV was performed on helium pre-irradiated tungsten and the amount of retained tritium and the long-term release of retained tritium in vacuum was investigated using an IP technique and BIXS. Tritium retention and long-term tritium release were significantly influenced by helium pre-irradiation. The amount of retained tritium increased until it reached 1 × 1017 He/cm2, and at 1 × 1018 He/cm2 it became smaller compared to 1 × 1017 He/cm2. The amount of retained tritium in tungsten without helium pre-irradiation largely decreased after several weeks preservation in vacuum, and the long-term release rate during vacuum preservation was retarded by helium pre-irradiation. The results indicate that the long-term tritium release and the helium irradiation effect on it should be taken into account for more precise estimation of tritium retention in the long-term use of tungsten in fusion devices

  16. Dynamics of thermoluminescence spectra of impurity-helium condensates containing stabilized nitrogen and oxygen atoms

    The results of investigations of thermoluminescence dynamics during destruction of neon-helium and krypton-helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton-helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra were found to increase simultaneously during destruction processes in the temperature range 1.5-15 K. Observation of the NO molecules provides clear evidence for chemical reactions in the nanoclusters comprising the sample at low temperatures. Destruction of neon-helium samples occurred in two stages. During the first stage the α-group of N atoms surrounded by Ne and N2 molecules dominated the spectra. During the second stage, the spectra contained intense bands of N and O atoms stabilized in a molecular nitrogen matrix. The unusual characteristics of the thermoluminescence spectra were observed, and their changes were explained in terms of the shell structure of impurity nanoclusters which comprised the impurity-helium condensates.

  17. Experimental determination of the effect of helium on the fracture toughness of steel

    A fundamental issue with the use of structural steels for fusion applications is the effect of helium on mechanical properties. This concern has been difficult to address due to the limited neutron energies, hence limited helium production, of the fission reactor facilities used to simulate the effects of irradiation on properties such as fracture toughness. This paper will compare results from identical pre-cracked DCT fracture toughness samples irradiated using spallation and fission neutrons at ≅60-90 deg. C. Materials studied were 304L and 316L stainless steel. The spallation neutron irradiated specimens were irradiated over a dose range up to ≅10 dpa with a helium and hydrogen-to-dpa ratio of ∼60 and 400, resp. Fracture toughness was seen to rapidly decreased from a value of ≅250 to ≅150 MPa m1/2 by the 1 dpa level. Following fission irradiation in the 1-1.5 dpa range, fracture toughness results were indistinguishable from those irradiated in the spallation neutron. The helium and hydrogen concentration for the fission neutron irradiated materials was ≅6 appm and ≅30 appm, respectively. It is concluded that, within the measurement uncertainty, increasing the helium and hydrogen concentration by more than an order of magnitude has had little influence on the fracture toughness of 304L and 316L stainless steel irradiated to similar displacement doses of a few dpa in the temperature range of 60-90 deg. C

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

    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 (Δν > 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

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

    Arkhipenko, V; Simonchik, L; Zgirouski, S; 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 temperature. At the same time the drastically reduction of concentration of the low-excited helium atoms in cathode region even at nitrogen admixture of 0.5 % is occurred.

  20. Control of two-photon double ionization of helium with intense chirped attosecond laser pulses

    Barmaki, S.; Lanteigne, P.; Laulan, S.

    2014-06-01

    We study the two-photon double-ionization process of the helium atom by solving numerically the nonrelativistic, time-dependent Schrödinger equation in its full dimensionality. We investigate with intense chirped attosecond laser pulses of 23.5-nm wavelength the two-photon absorption near and above the sequential threshold. We show how it is possible by adjusting the chirp parameter to control the electronic transitions inside the atom, thereby reinforcing or weakening the ionization process. Attosecond chirped laser pulses offer a promising way to probe and control the two-photon double ionization of helium when compared with attosecond transform-limited pulses.

  1. Binary and Recoil Collisions in Strong Field Double Ionization of Helium

    We have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a 800 nm, 4.5x1014 W/cm2 laser field. Using very high resolution coincidence techniques, we find a so-far unobserved fingerlike structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process. We identify features corresponding to the binary and recoil lobe in field-free (e,2e) collisions. This interpretation is supported by analyzing ab initio solutions of a fully correlated three-dimensional helium model

  2. Investigation of alpha particle slowing-down features in helium neutral beam fuelling experiments at JET

    The control of alpha particle densities in the core of a burning plasma and the removal of helium ash is a central topic in the design of next-step fusion devices. This paper addresses the reliability of absolute measurements, and the detectability of slowing-down alpha particles and their velocity distribution function by charge exchange recombination spectroscopy (CXRS). Experimental results at the JET tokamak are presented, where central helium fuelling and the slowing-down of alpha particles was simulated by injection of 140 keV 3He0 beams into deuterium target plasmas during low- and high-confinement periods. (author) 2 refs., 5 figs

  3. Nanometer-scale tunnel formation in metallic glass by helium ion irradiation

    We have shown that upon high fluence helium ion irradiation, metallic glass Cu50Zr45Ti5 becomes highly porous at the depth of the helium projected range. The resulting porous region is characterized by the formation of a tunnel like structure and self-linkage of nanometer size gas bubbles. Furthermore, the irradiation leads to the formation of nanometer size CuxZry crystals that are randomly distributed. The results of this study indicate that the He-filled bubbles have attractive interactions and experience considerable mobility. Movement of the bubbles is believed to be assisted by ballistic collisions.

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

    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 distinguish case BA (i...

  5. Data on trapping and re-emission of energetic hydrogen isotopes and helium in materials

    This report presents a compilation of the experimental data on trapping and re-emission of energetic hydrogen isotopes and helium in materials. A survey has been made of the literatures up to end of 1980, by dividing it into following seven sections: 1) Dose Dependence, 2) Target Material Dependence, 3) Time Dependence, 4) Target Temperature Dependence, 5) Incident Energy Dependence, 6) Damage Effects, 7) Ion-Induced Release. The experimental data for helium, however, is cited only in limited cases, because of the lack of experiments. (author)

  6. Cryogenic system with GM cryocooler for krypton, xenon separation from hydrogen-helium purge gas

    Chu, X. X.; Zhang, M. M.; Zhang, D. X.; Xu, D.; Qian, Y.; Liu, W.

    2014-01-01

    In the thorium molten salt reactor (TMSR), fission products such as krypton, xenon and tritium will be produced continuously in the process of nuclear fission reaction. A cryogenic system with a two stage GM cryocooler was designed to separate Kr, Xe, and H2 from helium purge gas. The temperatures of two stage heat exchanger condensation tanks were maintained at about 38 K and 4.5 K, respectively. The main fluid parameters of heat transfer were confirmed, and the structural heat exchanger equipment and cold box were designed. Designed concentrations after cryogenic separation of Kr, Xe and H2 in helium recycle gas are less than 1 ppb.

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

    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 JLabs 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

  8. Cryogenic system with GM cryocooler for krypton, xenon separation from hydrogen-helium purge gas

    In the thorium molten salt reactor (TMSR), fission products such as krypton, xenon and tritium will be produced continuously in the process of nuclear fission reaction. A cryogenic system with a two stage GM cryocooler was designed to separate Kr, Xe, and H2 from helium purge gas. The temperatures of two stage heat exchanger condensation tanks were maintained at about 38 K and 4.5 K, respectively. The main fluid parameters of heat transfer were confirmed, and the structural heat exchanger equipment and cold box were designed. Designed concentrations after cryogenic separation of Kr, Xe and H2 in helium recycle gas are less than 1 ppb

  9. Testing of accelerator dipoles in pressurized superfluid helium

    Two superconducting accelerator dipole magnets, with different internal construction features, have been tested in pressurized superfluid helium (1.8K, 1.2 atmosphere) as well as in regular pool boiling helium (4.4K, 1.2 atmosphere) helium. The coils of one magnet were moderately pre-stressed, and 4.2K design performance was rapidly achieved in the superfluid. The other magnet had very low coil pre-stress, reduced helium ventilation, and displayed degraded performance, even in the superfluid helium

  10. The future of helium as a natural resource

    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.

  11. The liquid helium storage system for the Large Hadron Collider.

    Benda, V; Fathallah, M; Goiffon, T; Parente, C; Perez-Duenas, E; Perret, Ph; Pirotte, O; Serio, L; Vullierme, B

    2011-01-01

    The cryogenic system of the Large Hadron Collider (LHC) under operation at CERN has a total helium inventory of 140 t. Up to 50 t can be stored in gas storage tanks. The remaining inventory will be stored in a liquid helium storage system consisting of six 15-t liquid helium tanks in 4 locations. The two liquid helium tanks of specific low heat inleak design and the required infrastructure of the first location were recently commissioned. Four additional tanks shall be operational end 2010. The paper describes the features and characteristics of the liquid helium storage system and presents the measurement of the thermal performance of the two first tanks.

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

    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).

  13. Doubly excited helium. From strong correlation to chaos

    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.)

  14. Doubly excited helium. From strong correlation to chaos

    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.)

  15. Deuteron and helium ion irradiation of ceramic coatings on Nb-1% Zr

    The surface damage to insulating barium alumino-silicate glass coatings due to irradiation by 100- and 250-keV deuterons and helium ions at room temperature and at 3000C has been studied. Blisters are observed after irradiation at room temperature with both deuterons and helium ions with energies of 100 keV and 250 keV. For deuteron irradiation a large fraction of the blisters have diameters which are approximately 3 to 5 times larger than the diameter observed with helium ions for identical irradiation conditions, but the density of blisters is nearly an order of magnitude lower. For irradiation at 3000C, no blisters are observed with either type of particle. The sharp rise in permeation rate with temperature is thought to be responsible for this behavior. The blister skin thicknesses have been measured and correlated with calculated projected-range values. (Auth.)

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

    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)

  17. Helium generation in copper by 14.8-MeV neutrons

    High purity copper foils were irradiated with 14.8-MeV neutrons from the rotating target neutron source facility at LLL. The average energy of the neutrons was 14.75 +- 0.1 MeV, and the average fluence was 7.0 x 1016 n/cm2. After irradiation each foil was heated to the melting point and the released helium was measured by a mass spectrometer of special design. Isochronal heating was carried out on several samples to establish the type and temperature of maximum release. Calculated cross sections from the literature for the (eta,α) and (eta,eta'α) nuclear reactions were used, and the predicted amount of helium was consistently about 0.5 of that actually measured. Because there is very little data on helium generation in metals irradiated with high energy neutrons, these results are important and will be related to potential CTR materials

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

    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.)

  19. Thermal desorption of deuterium from polycrystalline nickel pre-implanted with helium

    The thermal desorption technique has been used to study the trapping of deuterium atoms in high-purity polycrystalline nickel pre-implanted with helium for 1 x 1019 to 5 x 1020 ions/m2. The effect of post-implantation annealing at 703 K and 923 K on the desorption behavior was investigated. Measured values of the total amount of detrapped deuterium (QT) and helium concentration were used in a computer simulation of the desorption curve. It was found that the simulation using one or two discrete trap energies resulted in an inadequate fit between the simulated and the measured data. Both experimental and simulation results are explained using a stress-field trapping model. The effective binding energy, Ebeff, was estimated to be in the range of 0.4-0.6 eV. Deuterium charging was found to stimulate a release of helium at a relatively low temperature

  20. Effects of fueling profiles on particle transport and helium ash accumulation

    Parameteric surveys are conducted to investigate the effects of particle source profiles in the steady state of an ignited D-T tokamak plasma on the particle confinement time, the helium ash accumulation and the particle flux. The reference reactor envisaged is the INTOR-J having poloidal divertors with major axis of 5 m and minor radius of 1.2 m. The helium ash accumulation increases gradually for the helium recycling fraction R sub(α) less than about 0.8 and rapidly for R sub(α) > 0.8. It is possible to reduce considerably the required pumping speed by raising the recycling fraction to about 0.8 without an appreciable enhancement in β-value. (author)

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

    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

  2. Study of a liquid helium jet pump for circulating refrigeration systems

    A basic diagram of the refrigeration system, in which liquid helium is circulated by means of a jet pump, is described. The equations have been derived to design jet devices which operate with liquid helium. In the experimental setup with a jet pump the flow rate of liquid was 5 to 10 times larger than that of compressed gas in a direct stream of the refrigerator. After pumping the pressure was equal to (0.15-0.40) x 105 Nm-2. A circulating stream of liquid helium at supercritical pressure, due to the heat load corresponding to the refrigerator capacity, was heated to 0.15-0.25 K. The results are used to determine circulation loop parameters and main geometric dimensions of the jet pump. (author)

  3. Thermohydraulics of Quenches and Helium Recovery in the LHC Magnet Strings

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

    1997-01-01

    In preparation for the Large Hadron Collider project, a 42.5 m-long prototype superconducting magnet string, representing a half-cell of the machine lattice, has been built and operated. A series of tests was performed to assess the thermohydraulics of resistive transitions (quenches) of the superconducting magnets. These measurements provide the necessary foundation for describing the observed evolution of the helium in the cold mass and formulating a mathematical model based on energy conservation. The evolution of helium after a quench simulated with the model reproduces the observations. We then extend the simulations to a full LHC cell, and finally analyse the recovery of helium discharged from the cold mass.

  4. Krypton and helium irradiation damage in neodymium-zirconolite

    A leading candidate for the immobilisation of actinides, zirconolite's suitability as a potential ceramic host for plutonium disposition, both in storage and geological disposal, has been the subject of much research. One key aim of this study is to understand the effects of radiation damage and noble gas accommodation within the zirconolite material. To this end, a series of ex situ irradiations have been performed on polycrystalline (Ca0.8Nd0.2)Zr(Ti1.8Al0.2)O7 zirconolite samples. Zirconolite samples, doped with Nd3+ (as a Pu surrogate) on the Ca-site and charge-balanced by substituting Al3+ onto the Ti-site, were irradiated with 36Kr+ (2 MeV) ions at fluences of 1 x 1014 and 5 x 1015 cm-2 and 4He+ (200 keV) ions at fluences of 1 x 1014, 5 x 1015 and 1 x 1017 cm-2 to simulate the impact of alpha decay on the microstructure. Microstructural analysis revealed no damage present at the lower Kr+ fluence, but that the higher 36Kr+ fluence rendered the zirconolite completely amorphous. Similarly, evidence of helium accumulation was only seen at the highest 4He+ fluence (1 x 1017 cm-2). Monte Carlo simulations using the TRIM code predict the highest concentration of helium accumulating at a depth of 720 nm, in good agreement with the experimental observations.

  5. Helium-Cooled Refractory Alloys First Wall and Blanket Evaluation

    Under the APEX program the He-cooled system design task is to evaluate and recommend high power density refractory alloy first wall and blanket designs and to recommend and initiate tests to address critical issues. We completed the preliminary design of a helium-cooled, W-5Re alloy, lithium breeder design and the results are reported in this paper. Many areas of the design were assessed, including material selection, helium impurity control, and mechanical, nuclear and thermal hydraulics design, and waste disposal, tritium and safety design. System study results show that at a closed cycle gas turbine (CCGT) gross thermal efficiency of 57.5%, a superconducting coil tokamak reactor, with an aspect ratio of 4, and an output power of 2 GWe, can be projected to have a cost of electricity at 54.6 mill/kWh. Critical issues were identified and we plan to continue the design on some of the critical issues during the next phase of the APEX design study

  6. Helium-Cooled Refractory Alloys First Wall and Blanket Evaluation

    Wong, C.P.C.; Nygren, R.E.; Baxi, C.B.; Fogarty, P.; Ghoniem, N.; Khater, H.; McCarthy, K.; Merrill, B.; Nelson, B.; Reis, E.E.; Sharafat, S.; Schleicher, R.; Sze, D.K.; Ulrickson, M.; Willms, S.; Youssef, M.; Zinkel, S.

    1999-08-01

    Under the APEX program the He-cooled system design task is to evaluate and recommend high power density refractory alloy first wall and blanket designs and to recommend and initiate tests to address critical issues. We completed the preliminary design of a helium-cooled, W-5Re alloy, lithium breeder design and the results are reported in this paper. Many areas of the design were assessed, including material selection, helium impurity control, and mechanical, nuclear and thermal hydraulics design, and waste disposal, tritium and safety design. System study results show that at a closed cycle gas turbine (CCGT) gross thermal efficiency of 57.5%, a superconducting coil tokamak reactor, with an aspect ratio of 4, and an output power of 2 GWe, can be projected to have a cost of electricity at 54.6 mill/kWh. Critical issues were identified and we plan to continue the design on some of the critical issues during the next phase of the APEX design study.

  7. Electronic Structure of Helium Atom in a Quantum Dot

    Jayanta, K. Saha; Bhattacharyya, S.; T. K., Mukherjee

    2016-03-01

    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) configurations 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 due to the quantum dot. It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within a 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 width of the quantum cavity is also discussed here. TKM Gratefully Acknowledges Financial Support under Grant No. 37(3)/14/27/2014-BRNS from the Department of Atomic Energy, BRNS, Government of India. SB Acknowledges Financial Support under Grant No. PSW-160/14-15(ERO) from University Grants Commission, Government of India

  8. Electronic structure of helium atom in a quantum dot

    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...

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

    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

  10. Characterization of new a-Si:H detectors fabricated from amorphous silicon deposited at high rate by helium enhanced PECVD

    This paper is concerned with the characterization of new detectors fabricated from a-Si:H films deposited at high rates through the dilution of SiH4 in helium. Rates of up to ten times (5.5 micrometer/h) that of the standard technique are obtained, allowing for the feasible fabrication of detectors having thickness up to 100 micrometers. The electrical characteristics (depletion voltage, residual space charge density) of the helium diluted material, have been investigated and compared to that of the standard material. The response of detectors, made from both materials, to 5.5 MeV alpha particles are compared. 6 figs., 5 tabs., 13 refs

  11. Molecular dynamics study of helium bubble pressure in tungsten

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

  12. Molecular dynamics simulation of helium bubble coalescence in titanium

    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)

  13. Helium resources of the United States, 1993. Information circular/1995

    Hamak, J.E.; Driskill, D.L.

    1995-12-31

    This report uses several criteria to determine reserves, marginal reserves, and subeconomic resources, including helium content, proximity to major gas transmission lines, and size of field. Refinements in evaluating other occurrences of helium and undiscovered resources also have been made for this report. As of this report, there is 33.7 Bcf of helium stored in Bush Dome at Cliffside Gasfield. The USBM owns 31.7 Bcf, and 2.0 Bcf is owned by private companies. There is also approximately 3.8 Bcf of helium contained in the natural gas in Bush Dome. This reserve of helium and the helium on Federal lands in nondepleting fields will fulfill the USBM`s mission of supplying helium to meet all essential Government needs for several decades.

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

    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. Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

    Hu, Lin; Hammond, Karl D.; Wirth, Brian D.; Maroudas, Dimitrios

    2015-10-01

    We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (Hen, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He4 and He5 clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

  16. Dynamic imaging of the nasal cavity and the paranasal sinuses with polarized 3helium MRI

    Purpose: Reduced or blocked ventilation of the paranasal sinuses is probably the most important factor in the development of sinusitis. Recently, the use of optically polarized noble gas isotopes has attracted increasing interest for use in a variety of promising MR applications. The aim of this study was to test the feasibility of imaging and visualization ventilation of the nasal cavity and paranasal sinus in MR by inhalation of hyperpolarized 3helium. The goal was to evaluate ventilation defects of the paranasal sinuses. Volunteers and Methods: Three volunteers were enrolled in the study. 3Helium was polarized to 40 - 50% by direct optical pumping. 300 ml of 100% 3helium were administered in the left nasal vestibule through a glass tube. With a closed contralateral nasal vestibule, the Valsalva maneuver was performed twice. Using a dedicated application unit, which is also used in MR imaging of the lung, an exact amount of 3helium gas was administered at the beginning of inspiration. Measurements were carried out on a clinical 1.5 T scanner. Coronal images of the nasal cavity and paranasal sinuses were acquired using ultrafast gradient-echo pulse sequence (TR = 2 ms, TE = 0.7 ms, FA 3helium gas. The signal intensity in the left maxillary sinus was higher compared to the right one. The mean signal intensity on the left side was 526±86 and on the right side 336±102. The left and right frontal sinus and ethmoid sinus only show signal of hyperpolarized 3helium after two Valsalva maneuvers. Because of the low signal intensity of the frontal and ethmoid cells their visualization was incomplete. The signal to noise ratio was 14.1 for the left maxillary sinus, 8.9 for the right side, 6.3 for the left ethmoid sinus, 5.8 for the right side and 6.6 for the left frontal sinus and 7.8 for the right side. (orig.)

  17. Hydrogen and helium retention properties of B4C and SiC converted graphites

    The hydrogen or helium retention properties of B4C converted graphite, SiC converted graphite and isotropic graphite were examined, by the irradiation of a hydrogen or helium ion, followed by a thermal desorption spectroscopy measurement. The energy of the hydrogen or helium ion was 1.7 or 5.0 keV, respectively. For both B4C and SiC, two peaks appeared in the H2 desorption spectra. The lower temperature peaks of B4C and SiC correspond to detrappings of B-H and Si-H bonds, respectively. It is considered that the higher peak is due to detrapping of the C-H bond. The amounts of retained hydrogen at room temperature (RT), obtained from the H2 desorption spectra, were 6.71 x 1017, 1.0 x 1018 and 5.8 x 1017 H cm-2 for isotropic graphite, B4C and SiC, respectively. For the He desorption spectrum in the case of B4C, two peaks appeared at 300 and 950 C. For SiC, a sharp desorption peak was observed at 850 C, in addition to the low temperature peak at ?300 C. For graphite, the spectrum had a single peak at 300 C. When the helium fluence was increased, this peak temperature shifted to the higher temperature region. The amount of retained helium in B4C, SiC and isotropic graphite at RT were 2.7 x 1017, 4.2 x 1017 and 3.4 x 1017 He cm-2, respectively. It is seen that the trapped amount of helium is not negligibly small. (orig.)

  18. Trapping, diffusion and release of helium in single-crystal TiC observed by thermal desorption spectrometry

    Using thermal desorption spectrometry (TDS), the interaction of ion-implanted helium atoms and atomic-scale defects in titanium carbide was investigated. It is found that trapping and release of helium in off-stoichiometric single-crystal TiC0.924 can be well described by a diffusive, single activation energy (2.5 eV) process. This energy is attributed to the release of a helium atom from a carbon vacancy. The experimental spectra are in excellent agreement with results obtained from diffusion theory in the presence of sinks and sources; at low implantation energies the projected range of helium is larger than the theoretical predictions and the range straggling is found to be 67±3 A, independent of the implantation energy (0.1-3 keV). (orig.)

  19. Capillary propagation of sound and anomalous Kapitsa jump at the boundary between solid and liquid helium

    Marchenko, V.I.; Parshin, A.Y.

    1980-06-20

    It is shown that the probability of sound propagation across the quantum boundary between liquid and solid helium at T=0 is proportional to the square of the frequency. The Kapitsa jump at such a boundary depends, therefore, on the temperature according to a T/sup -5/ law.

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

    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.