WorldWideScience

Sample records for Helium 5

  1. Acquisition system for the liquid helium L5 plant

    International Nuclear Information System (INIS)

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

    International Nuclear Information System (INIS)

    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

    International Nuclear Information System (INIS)

    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 isotopes on the Pacific-Antarctic ridge (52.5°–41.5°S)

    OpenAIRE

    Moreira Manuel, A.; Dosso, Laure; Ondre?as, He?le?ne

    2008-01-01

    The first isotopic data and concentrations of helium are reported for the Pacific-Antarctic ridge between 52.5 degrees S and 41.5 degrees S. The He-4/He-3 ratio is extremely homogeneous over more than 1200 km, with a mean ratio of 99,275 (R/Ra = 7.29) and a standard deviation of 2719 (0.19), which is the lowest dispersion observed for the global mid oceanic ridge system. Moreover, the Menard T. F. is a frontier between two mantles with slightly different helium isotopic ratios (96,595 +/- 152...

  5. Effect of helium on the deformation mode for Ti-7.5Al alloy

    International Nuclear Information System (INIS)

    The effect of helium on the mechanical properties of Ti-7.5Al alloy was investigated at 873 K on the specimens injected with helium to the concentration CHe of 5, 18 and 30 appm by using a cyclotron. Helium had a small effect on the yield stress but a large one on the elongation; the elongation decreased at first with increasing CHe in the region of CHe less than 18 appm and increased again for larger CHe. Correspondingly, the deformation mode changed with the helium concentration. The deformation of uninjected specimens proceeded by the dislocation slip and two twin systems, that is, (1012) and (1121). The latter twin system disappeared in the 18 appm helium-injected specimen. Both deformation twins disappeared in the 30 appm specimen, the microstructure of which exhibited the uniform cellular structure of dislocations. (orig.)

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

    Science.gov (United States)

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

    2014-10-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  9. Penetration Characteristics of Air, Carbon Dioxide and Helium Transverse Sonic Jets in Mach 5 Cross Flow

    Directory of Open Access Journals (Sweden)

    Erinc Erdem

    2014-12-01

    Full Text Available An experimental investigation of sonic air, CO2 and Helium transverse jets in Mach 5 cross flow was carried out over a flat plate. The jet to freestream momentum flux ratio, J, was kept the same for all gases. The unsteady flow topology was examined using high speed schlieren visualisation and PIV. Schlieren visualisation provided information regarding oscillating jet shear layer structures and bow shock, Mach disc and barrel shocks. Two-component PIV measurements at the centreline, provided information regarding jet penetration trajectories. Barrel shocks and Mach disc forming the jet boundary were visualised/quantified also jet penetration boundaries were determined. Even though J is kept the same for all gases, the penetration patterns were found to be remarkably different both at the nearfield and the farfield. Air and CO2 jet resulted similar nearfield and farfield penetration pattern whereas Helium jet spread minimal in the nearfield.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    International Nuclear Information System (INIS)

    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) (author)

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-10-01

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

  14. Thermal-hydraulic system study of a high pressure, high temperature helium loop using RELAP5-3D code

    International Nuclear Information System (INIS)

    Highlights: ? A thermal-hydraulic system analysis for a high pressure, high temperature helium loop has been investigated. ? The loop belongs to the Helium Loop Karlsruhe (HELOKA) facility, which contains the European Helium Cooled Pebble Beds Test Blanket Module (HCPB TBM) as the test module. ? The loop including all components has been modeled using the system code REALP5-3D, and the main control strategy has been implemented as well. ? With this model, the loop dynamics in conditions relevant for blanket module operation have been demonstrated. - Abstract: The thermal-hydraulic system analysis for the Helium Loop Karlsruhe (HELOKA) facility, a high pressure, high temperature experimental helium loop having the European Helium Cooled Pebble Beds Test Blanket Module (HCPB TBM) as the test module, was investigated. Using the system code REALP5-3D, all components in the loop are modeled as well as the main control strategy. With this model, the loop dynamics in conditions relevant for blanket module operation are simulated and analyzed.

  15. Swelling of CLAM steel irradiated by electron/helium to 17.5 dpa with 10 appm He/dpa

    International Nuclear Information System (INIS)

    To investigate irradiation/helium effects on microstructure of China Low Activation Martensitic (CLAM) steel, single beam (e-) and dual-beam (e-/He+) irradiation to 17.5 dpa with 10 appm He/dpa at 400 deg. C and 450 deg. C on CLAM steel was carried out with high voltage electron microscope HVEM. Evolution of microstructure was in situ observed during irradiation and annealing procedure. Preliminary results showed that size and density of voids and helium bubbles increased with irradiation dose. And swellings of voids and bubbles are ?0.5% and 1-1.5%, respectively after irradiation.

  16. Helium localisation in tritides

    International Nuclear Information System (INIS)

    Study of titanium and LaNi5 type alloys tritides lattice parameters evolution revealed that helium created by tritium decay remains in interstitial sites up to a limit material dependant concentration. Beyond this one exceeding helium precipites in voids

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

    International Nuclear Information System (INIS)

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

  18. Compression effects in helium-like atoms (Z=1,...,5) constrained by hard spherical walls

    International Nuclear Information System (INIS)

    Ground and lowest triplet S state energies and other properties are obtained for confined helium-like atoms {Z=1,...} spherically enclosed by impenetrable boxes of varying size. Wave functions are variationally optimized within generalized Hylleraas bases fulfilling appropriate boundary conditions. For all systems, enhanced confinement leads to increased total energies and singlet-triplet energy splittings

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  1. Helium purifiers

    International Nuclear Information System (INIS)

    An automatic purifier, working in conjunction with a standard range of Turbocool helium liquefiers is described. For the larger helium user, an automatic purifier is described, which reclaims helium gas of any purity and makes it suitable for recharging grade A or grade X cylinders at 150-200 bar. (author)

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

    CERN Document Server

    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.

  3. Chromosome aberrations induced in human lymphocytes by 8.7 MeV protons and 23.5 MeV helium-3 ions

    International Nuclear Information System (INIS)

    This paper describes the irradiation of thin samples of blood with 8.7 MeV protons and 23.5 MeV helium-3 ions in the track segment mode. Chromosome aberrations in human lymphocytes have been scored. The relationship between dicentric yield and dose in Gy was Y = 0.044 D + 0.058 D2 for protons and Y = 0.394 D for helium ions. These results are compared with data from other laboratories using protons and an attempt is made to reconcile differences. An unexpected observation was that the ratio of the linear coefficients for helium ions and protons was about 9 whereas the ratio of the l.e.t. values was 4.5. This disagrees with current theory which predicts that the linear coefficients should be proportional to l.e.t. Possible sources of error in our experiments are discussed but do not adequately account for the discrepancies. (author)

  4. A proposal for a 0.5 K, atmospheric pressure liquid helium cooling system for a polarized proton target

    International Nuclear Information System (INIS)

    The great heat removal capability of pressurized superfluid helium has led in recent years to its use as a coolant in fusion and accelerator magnets where the operating temperature is 2 K. The low temperature liquid region is pressurized via a liquid filled channel which communicates with a saturated liquid near one atmosphere pressure and 4.2 K. A recent proposal extends this technique down to 0.5 K for the cooling of a polarized proton/deuteron target. This experiment involves the scattering of longitudinally polarized electrons off polarized protons in an irradiated ammonia target and polarized deuterons in a deuterated ammonia target. The intense heating of the target by the electron beam and polarizing microwave radiation of the 20 cm/sup 3/ porous target necessitates a departure from the relatively mature technology of direct cooling by pool or forced convection boiling

  5. Helium purification

    Energy Technology Data Exchange (ETDEWEB)

    Nikitina, I.E.; Ben' yaminovich, O.A.

    1978-03-01

    Results are given for a tentative technical-economic comparison of the operations of fine helium purification equipment that operates on the following principles: nitrogen condensation at high pressure; preliminary liquid methane washing of the helium concentrate, and isothermic short-cyclic adsorption. 3 figures, 2 tables.

  6. Single-electron detachment cross sections for 5--50-keV H- ions incident on helium, neon, and argon atoms

    International Nuclear Information System (INIS)

    Absolute measurements of the total single-electron detachment (SED) cross sections ?-10 for 3--50-keV H- ions incident on helium atoms and for 5--50-keV H- ions incident on neon and argon atoms are reported in this paper. The present SED cross sections for helium and neon targets are of similar magnitude but have a different energy dependence. By contrast, the SED cross sections for argon targets are significantly larger than either of the other two target species reported in this paper. Comparisons are made with the previous measurements and calculations in the literature

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

    CERN Document Server

    Abboud, M; Maitre, X; Tastevin, G; Nacher, P J; Abboud, Marie; Sinatra, Alice; Maitre, Xavier; Tastevin, Genevieve; Nacher, Pierre-Jean

    2003-01-01

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

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

    CERN Document Server

    Lebrun, Ph; Tavian, L

    2014-01-01

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

  9. Helium cryogenics

    CERN Document Server

    Van Sciver, Steven W

    2012-01-01

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

  10. Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2. [for atmospheric processes modeling

    Science.gov (United States)

    Newman, J. H.; Smith, K. A.; Stebbings, R. F.; Chen, Y. S.

    1985-01-01

    This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

  11. Patterning, characterization, and chemical sensing applications of graphene nanoribbon arrays down to 5 nm using helium ion beam lithography.

    Science.gov (United States)

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

    2014-02-25

    Bandgap engineering of graphene is an essential step toward 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 nm have been achieved, problems like GNR alignment, width control, uniformity, high aspect ratios, and edge roughness must be resolved in order to introduce GNRs as a robust alternative technology. Here we report patterning, characterization, and superior chemical sensing of ultranarrow 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 parts per billion (ppb) levels. The results show the potential of HIBL fabricated GNRs for the electronic and sensing applications. PMID:24467172

  12. RELAP5 and CATHARE2 benchmarking assessment on two LOFA transients conducted in HE-FUS3 helium facility

    International Nuclear Information System (INIS)

    The qualification of numerical tools for the transient and safety analysis of High Temperature Gas Reactors (HTGR) is essential to demonstrate the fulfillment of the GEN IV safety requirements. The availability of experimental data from the ENEA HE-FUS3 facility (Brasimone (Italy)) has given the opportunity to organize a benchmark exercise to assess the capability of a number of transient analysis code to describe the T/H behavior of a helium cooled loop both in steady state and transients conditions. The paper presents the results obtained in the post-test analysis of experimental LOFA transients with two of the most widely used system codes: RELAP5 Mod3.3 applied by ENEA-ANSALDO and CATHARE 2 V2.5 applied by CEA-IRSN. The analysis of these results on the basis of a code-to-data comparison and a code-to-code benchmark allows to verify that both codes are able to qualitatively reproduce the gas system thermal-hydraulics and dynamics, as well as to provide recommendations on gas cooled system modeling for the development of consistent numerical models for the HTGR accident analysis. Moreover, highlighting the weakness in some aspects of the present modeling approach, it is possible to suggest the needs of the future code developments. (authors)

  13. Helium liquefaction using cryorefrigerators

    Science.gov (United States)

    Forth, Hans-Joachim

    1986-12-01

    A two-stage Gifford-McMahon refrigerator with a Joule-Thomson (J-T) stage connected in series, was extended to a small helium liquefier. The plant can operate automatically. Helium is liquefied within the J-T cycle, directly after the J-T valve, into a 3l tank. This liquid He is used for the indirect cooling of an externally accessible sample chamber, either by using helium contact gas, or by means of liquid He condensed from an external helium gas source. The second design is meant for laboratory applications. The liquid helium tank is not incorporated in the J-T cycle, but thermally connected to the J-T stage of the refrigerator. The He gas from an external source is then condensed into the 2l tank. The liquid helium is accessible via a top-loading sample tube. The refrigerating capacity of both devices is 2W at 4.5K. The cleaning procedures for the He gas to be condensed into the tanks, and the production of temperatures below 4.2K in the He bath are described.

  14. Hot HB Stars in Globular Clusters: Physical Parameters and Consequences for Theory. 5; Radiative Levitation Versus Helium Mixing

    Science.gov (United States)

    Moehler, S.; Sweigart, A. V.; Landsman, W. B.; Heber, U.

    2000-01-01

    Atmospheric parameters (T(sub eff), log g), masses and helium abundances are derived for 42 hot horizontal branch (HB) stars in the globular cluster NGC6752. For 19 stars we derive magnesium and iron abundances as well and find that iron is enriched by a factor of 50 on average with respect to the cluster abundance whereas the magnesium abundances are consistent with the cluster abundance. Radiation pressure may levitate heavy elements like iron to the surface of the star in a diffusive process. Taking into account the enrichment of heavy elements in our spectroscopic analyses we find that high iron abundances can explain part, but not all, of the problem of anomalously low gravities along the blue HB. The blue HB stars cooler than about 15,100 K and the sdB stars (T(sub eff) greater than or = 20,000 K) agree well with canonical theory when analysed with metal-rich ([M/H] = +0.5) model atmospheres, but the stars in between these two groups remain offset towards lower gravities and masses. Deep Mixing in the red giant progenitor phase is discussed as another mechanism that may influence the position of the blue HB stars in the (T(sub eff), log g)-plane but not their masses.

  15. Effect of oxygen and water vapor containing in helium on the structure and properties of zirconium - 2.5 Nb alloy welded joints

    International Nuclear Information System (INIS)

    The effect of oxygen and water vapors containing in helium on the structure, phase composition and properties of welded joints of zirconium-2.5% Nb alloy executed by tungsten electrode in a chamber is considered. It is stated that content of oxygen and water vapors in helium should not exceed 1x10-2%. The strength of weld metal increases from 750 to 870 MPa after welding in the mixture of helium with 1x10-1...3% O2. Impact strength of the joint decreases at room temperature from 68 to 11 J/cm2 with the increase of oxygen content up to 10%. Interaction of zirconium with oxygen the concentration of which is 1x10-2... 3% results in formation of solid solutions and zirconium dioxide. The latter covers the joint surface in the form of a film. With further increase of oxygen content in helium ZrO2 precipitates in the body and on the grain boundaries. Interaction of the alloy with water vapors at their 1x10-4...1x10-1% concentration does not essentially affect the mechanical properties and structure of welded joints though hydrogen content in the metal increases from 6x10 to 11x10-4% and the surface of the joint is covered by the film

  16. Helium photoelectron satellites: Low-energy behavior of the n = 3--5 lines

    International Nuclear Information System (INIS)

    Photoelectron satellite branching ratios and asymmetry parameters have been measured for photoionization of atomic He to He+(n), where n = 3--5, at a few photon energies near the satellite thresholds. The n = 3 and n = 4 satellite branching ratios relative to the n = 1 main-line cross section exhibit behavior similar to that previously observed for the He+(n = 2) satellite. The asymmetry parameter ? shows progressively more negative values as n increases, supporting a prediction by Greene [Phys. Rev. Lett. 44, 869 (1980)] for the threshold behavior of the He satellites

  17. Helium behaviour in expanded boundary divertor discharges

    International Nuclear Information System (INIS)

    Helium was injected into expanded boundary divertor discharges in Doublet III to evaluate the helium exhaust and enrichment capabilities of the divertor. Helium was found to enter the main body of the plasma readily, achieving a concentration similar to that without the divertor At a helium concentration in the main plasma of 5% of anti nsub(e), helium pressure of 5x10-5 torr was observed in the pumping duct with no enrichment of helium relative to atomic hydrogen, while at higher densities helium pressure decreased and significant de-enrichmen was observed. Simplified calculations of the relative penetration depth of neutral hydrogen and helium are consistent with these results. (author)

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Lebrun, Philippe; Parma, Vittorio; Tavian, Laurent

    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 projects confronted with this issue, i.e. CEBAF, SPL, ESS, LHC, TESLA, European X-FEL, ILC.

  1. Characterization of helium surface-wave plasmas at intermediate pressures (5–50?Torr): temperatures and density of metastable atoms in the 23s level

    Science.gov (United States)

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

    2015-01-01

    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.

  2. Helium properties important for experiments

    International Nuclear Information System (INIS)

    The typical helium property at a temperature lower than 2.17 K is a drop in viscosity. Superfluid helium features extra high thermal conductivity. Variations are given of the vapour pressure above liquid helium in a range of 0.01 to 1,000 torr with temperatures in a range of 0 to 3.5 K. The coefficient of heat transfer between the cryogenic liquid and the heat transfer surface grows from 300 to 15,000 Wm-2K-1. A single-phase flow may only be considered for the supercritical state helium. Helium density and thus also the intensity of cooling is significantly higher than for vapour of the same temperature under normal pressure. (J.B.)

  3. Small scale helium liquefaction systems

    Science.gov (United States)

    Wang, Chao

    2009-02-01

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

  4. Differential cross sections for ejection of electrons and dissociative ionisation cross sections for 5-20 keV H2+ and H3+ impacts on helium

    International Nuclear Information System (INIS)

    The absolute electron-production cross sections for 5-20 keV H2+ and 5-20 keV H3+ impacts on helium, differential in angle and energy of the ejected electrons, have been measured for electron energies of 2-50 eV at ejection angles of 300, 600, 900 and 1200. The dissociative ionisation cross sections are derived from the present differential cross sections for electron production and compared with the results of direct measurement by Guidini (C.R. Acad. Sci., Paris 253: 829 (1961)). (author)

  5. ISABELLE forced circulation cooling system: proposed method of producing and distributing helium refrigerant for 4.5 K superconducting magnets

    International Nuclear Information System (INIS)

    A report is given of the refrigeration system proposed for ISABELLE. The system features a single refrigerator of about 25 kW capacity. The refrigerant helium is supplied to the 960 ISABELLE Magnets at a pressure of 15 atm and a temperature of 2.80K. The return to the refrigerator is at 14.3 atm and a 6.20K. As many as 60 magnets will be cooled in series. The steady-state design temperature for the warmest magnet is 4.30K. This temperature will rise to 4.50K during the acceleration cycle

  6. Helium cooled nuclear reactors

    International Nuclear Information System (INIS)

    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

  7. Liquid hydrogen target cooled by circulating helium

    International Nuclear Information System (INIS)

    Structure and characteristics of a liquid hydrogen target, where hydrogen is liquefied with liquid helium flow using evaporation heat of liquid helium and vapour cold, are described. Good thermal insulation of liquid helium supply line permits to remove out of the target the most volumetric and heavy component - helium tank - and to supply liquid helium along spreaded pipeline from the Dewar helium flask. It results in considerable reduction of dimensions and weight, the structure simplification and work facilitation with the target. The target having a working volume of 400 mm length and 60 mm diameter was tested. Vacuum casing of the working volume was made of foam plastic, heat flow to the working volume is equal to 1.5 W. Achieving mode of operation including structure cooling and hydrogen liquefaction took approximately 3 h, liquid helium flow rate for liquefaction of 1 l hydrogen is 2.7 l. Liquid helium flow rate in the mode of operation was equal to 0.7 l/h, i.e. target operation period without adding liquid helium to the Dewar flask is 4-5 days. The target described is notable for simplicity in fabrication, reliability in operation and is very suitable for using in experiment as compared to existing targets with hydrogen liquefaction with liquid helium. Unit structure of the target enables to easily change its configuration relative to problems of concrete physical experiment

  8. Non-relativistic contributions in order $\\alpha^5m_\\mu c^2$ to the Lamb shift in muonic hydrogen, deuterium and helium ion

    CERN Document Server

    Karshenboim, S G; Korzinin, E Yu; Shelyuto, V A

    2010-01-01

    Contributions to the energy levels in light muonic atoms and, in particular, to the Lamb shift fall into a few well-distinguished classes. The related diagrams are calculated using different approaches. In particular, there is a specific kind of non-relativistic contributions. Here we consider such corrections to the Lamb shift in order $\\alpha^5m_\\mu$. These contributions are due to free vacuum polarization loops as well as to various effects of light-by-light scattering. The closed loop in the related diagrams is an electronic one, which allows a non-relativistic consideration of the muon. Both kinds of contributions have been known for a while, however, the results obtained up to date are only partial ones. We complete a calculation of the $\\alpha^5m_\\mu$ contributions for muonic hydrogen. The results are also adjusted for muonic deuterium and muonic helium ion.

  9. Nonrelativistic contributions of order ?5m?c2 to the Lamb shift in muonic hydrogen and deuterium, and in the muonic helium ion

    International Nuclear Information System (INIS)

    Contributions to the energy levels in light muonic atoms and, in particular, to the Lamb shift fall into a few well-distinguished classes. The related diagrams are calculated using different approaches. In particular, there is a specific type of nonrelativistic (NR) contribution. Here, we consider such corrections to the Lamb shift of order ?5m?. These contributions are due to free vacuum-polarization loops as well as to various effects of light-by-light scattering. The closed loop in the related diagrams is an electronic one, which allows an NR consideration of the muon. Both types of contributions have been known for some time, however, the results obtained to date are only partial results. We complete a calculation of the ?5m? contributions for muonic hydrogen. The results are also adjusted for muonic deuterium atom and helium ion.

  10. Ionized helium afterglow study

    International Nuclear Information System (INIS)

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

  11. Labarge liquid helium plant

    International Nuclear Information System (INIS)

    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

  12. Simulative supercritical helium force flow cooled system

    International Nuclear Information System (INIS)

    The simulative supercritical helium system designed for testing of CICC (cable-in-conduit conductor) sub-cable and joint is composed of high pressure He gas tank, pressure regulator, mass flow controller, liquid nitrogen pre-cooler, counter flow heat exchanger, liquid helium bath cooling heat exchanger etc. The system testing has been completed; it can provide 0-0.15 g/s, 6 bar, 4.5 K supercritical helium for sub-cable and joint test

  13. Helium in inert matrix dispersion fuels

    International Nuclear Information System (INIS)

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

  14. Orion A helium abundance

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

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

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1996-01-01

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

  17. Thermal-hydraulic system study of the helium cooled pebble bed (HCPB) test blanket module (TBM) for ITER using system code RELAP5

    International Nuclear Information System (INIS)

    The HCPB concept has been a European DEMO reference concept for nearly one decade. Detailed thermal-hydraulic study on the control behavior of the whole system is one of the important parts of this development. The thermal-hydraulic effect of the TBM-combined cooling circuit during a cyclic operation in ITER has been studied using the system code RELAP5. The RELAP5 is based on an one-dimensional, transient two-fluid model for the flow of a two-phase steam-water mixture that can contain noncondensable components like Helium. The RELAP5-models are modified to take the cyclic operation of the circulator, heat exchanger, bypass, valves etc in to account. A sequence of operational phases is investigated, starting from the cold state through the heating phase that brings the system to a stand-by condition, followed by typical power cycles applied in ITER. The results show that the implemented control mechanisms keep the inlet temperature to the TBM and the total mass flow rate at the required values through all phases. (authors)

  18. Thermal-Hydraulic System Study of the Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM) for ITER Using System Code RELAP5

    Science.gov (United States)

    Jin, Xuezhou; R, Meyder

    2005-04-01

    The HCPB concept has been a European DEMO reference concept for nearly one decade. Detailed thermal-hydraulic study on the control behavior of the whole system is one of the important parts of this development. The thermal-hydraulic effect of the TBM-combined cooling circuit during a cyclic operation in ITER has been studied using the system code RELAP5. The RELAP5 is based on an one-dimensional, transient two-fluid model for the flow of a two-phase steam-water mixture that can contain noncondensable components like Helium. The RELAP5-models are modified to take the cyclic operation of the circulator, heat exchanger, bypass, valves etc in to account. A sequence of operational phases is investigated, starting from the cold state through the heating phase that brings the system to a stand-by condition, followed by typical power cycles applied in ITER. The results show that the implemented control mechanisms keep the inlet temperature to the TBM and the total mass flow rate at the required values through all phases.

  19. Determining neon microconcentration in helium during laser excitation of 2p/sup 5/3s. -->. 2p/sup 5/3p neon transition in high-frequency discharge

    Energy Technology Data Exchange (ETDEWEB)

    Bol' shakov, A.A.; Oshemkov, S.V.; Petrov, A.A.

    1983-11-01

    The problem of lowering the detectability threshold of gases in a mixture during spectral analysis is considered, one method using a stronger signal from a dye laser and thus add to the population at the upper level of the analytical line from the most populated lower excited state. In the transillumination mode the populations at these two levels of the active transition tend to become equal, differing only statistically, while the fluorescence signal reaches its maximum and ceases to depend on the spectral density of the pumping power. In a feasibility study this method of improving the sensitivity of spectral gas analysis was applied to determination of the neon microconcentration in helium in a high-frequency discharge. The latter was produced in the quartz tube of 1 500 W - 1.5 MHz VG-5 generator. Fluorescence was excited by means of a dye laser (cresyl-violet solution in butanol) tunable over the 570-610 nm range of wavelengths and pumped by second-harmonic emission from an LTIPCh-5 YAG-laser operating in the periodic-pulse mode at 12.5 and 25 Hz repetition rates. The active transition for laser excitation was the 2p/sup 5/3s(/sup 3/P/sub 2//sup 0/) ..-->.. 2p/sup 5/3p(/sup 3/P/sub 1/) neon transition (wavelength lambda = 588.2 nm), its lower level being the most populated one. A specimen of helium was admitted to a preevacuated discharge tube under a pressure of 1.7 kPa. After ignition of the discharge, fluorescence signals were measured repeatedly over a certain period of time (160 s) and recorded at the 616.4 nm line of the high-probability /sup 3/P/sub 1/ ..-->.. /sup 3/P/sub 0//sup 0/ transition. After calibration of the measured pressure dependence of the fluorescence signal intensity and extrapolation to the noise level according to the 3sigma-criterion, to account for the insufficient purity of helium, the results indicate that the neon detectability threshold can be lowered by this method from 5.10/sup -2/ vol.% to 1 x 10/sup -6/ vol.%.

  20. Mobility of ? particles in helium

    International Nuclear Information System (INIS)

    The mobility of ? particles in helium gas is calculated using the zeroth-order Viehland-Mason theory with interaction potentials recently computed by Cohen and Bardsley. The results show a dependence on field strength similar to the measurements of Johnsen and Biondi but are lower in magnitude by about 5%

  1. A helium liquefier using three 4 k pulse tube cryocoolers

    Science.gov (United States)

    Wang, Chao; Oviedo, Abner

    2012-06-01

    We have developed a helium liquefier which can be used for recondensing/reliquefying helium vapor in a helium cryostat or liquefying helium gas in a storage dewar. The helium liquefier employs three 4 K pulse tube cryocoolers, Cryomech model PT415. Each PT415 has remote motor/rotary valve assembly to minimize vibration, providing ? 1.5W at 4.2K. The liquefier can liquefy room temperature helium gas with a liquefaction rate of 62 Liter/day. When installing it in the cryostat, it can recondense and reliquefy helium vapor with a rate of 78 L/day. The liquefier will be installed in a gravitational wave detector in Brazil to recondense/reliquefy the helium boil off from the cryostat.

  2. Helium in the Universe.

    Science.gov (United States)

    Tayler, R. J.

    1995-02-01

    The element helium was discovered on Earth in March 1895, although its existence had been suggested much earlier by J.N. Lockyer after unidentified spectral lines had been observed in a solar eclipse in 1868. Helium plays a major role in astronomy and cosmology. As a radioactive decay product, it helped to establish the great age of the Earth. Nuclear reactions, producing helium from hydrogen, power most stars and nuclear reactions involving helium are important in late stages of stellar evolution. All stars and gas clouds appear to contain substantial amounts of helium and this observation, together with the discovery and properties of the cosmic microwave radiation, is one of the two factors leading to the current popularity of the hot big-bang cosmological theory. Because helium is such a strongly bound nucleus, a single secure identification of a star or a gas cloud devoid of helium would cause great difficulties for the theory.

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

    Energy Technology Data Exchange (ETDEWEB)

    ARD, K.E.

    2000-04-19

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

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

    Science.gov (United States)

    Zayarnyi, D. A.; L'dov, A. Yu; Kholin, I. V.

    2014-11-01

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

  5. Partial photoionization cross sections and photoelectron angular distributions for double excitations up to the N=5 threshold in helium

    International Nuclear Information System (INIS)

    Partial photoionization cross sections ?n and photoelectron angular distributions ?n were measured for all possible final ionic states He+(n) in the region of the double excitations N(K,T)A up to the N=5 threshold. At a photon energy bandpass of 12 meV below the thresholds N=3,4, and 5, this level of differentiation offers the most critical assessment of the dynamics of the two-electron excitations to date. The experimental data are very well described by the most advanced theoretical calculations. Weaker double-excitation series with K=N-4 are clearly visible in the ?n data, and even previously unobserved extremely weak series members with A=-1 can be discerned, showing the high sensitivity of the angular resolved measurements. The shapes of the resonance-induced variations of ?n or ?n in the double excitations below a given threshold N change radically depending on the final ionic state n but display striking similarities when comparing the satellite states with n=N-1 and n=N-2 below each threshold N. These systematic patterns may indicate a general rule for the underlying two-electron dynamics. copyright 1996 The American Physical Society

  6. Quenching of krypton atoms in the metastable 5s (3P2) state in collisions with krypton and helium atoms

    Science.gov (United States)

    Zayarnyi, D. A.; L'dov, A. Yu; Kholin, I. V.

    2013-08-01

    We have used the absorption probe method to study the processes of collisional quenching of the metastable 5s [3/2]o2(3P2) state of the krypton atom in electron-beam-excited high-pressure He - Kr mixtures with a low content of krypton. The rate constants of plasma-chemical reactions Kr* + Kr + He ? Kr*2+He [(2.88 +/- 0.29) × 10-33 cm6 s-1], Kr* + 2He ? HeKr* + He [(4.6 +/- 1.3) × 10-36 cm6 s-1] and Kr* + He ? products + He [(1.51 +/- 0.15) × 10-15 cm3 s-1] are measured for the first time. The rate constants of similar reactions in the Ar - Kr mixture are refined.

  7. Inclusive inelastic scattering of 96.5-MeV ?+ and ?- by the hydrogen and helium isotopes

    International Nuclear Information System (INIS)

    Spectra, angular distributions, and integrated cross sections for inclusive inelastic scattering of 96.5-MeV ?+ and ?- from 2H, 3He, and 4He are presented. The measurements were made using a high-pressure gas cell, which permits an accurate determination of relative cross sections for all targets. The data are compared with distorted-wave impulse-approximation calculations and with a modified plane-wave impulse-approximation calculation. In addition, by combining the total inelastic cross sections from this work with estimates of single-charge-exchange cross sections and with published values and reasonable estimates of the other ?+ cross sections at the same energy, values for total reaction and pion absorption cross sections are obtained for all the targets. The dependence of these cross sections on Z, N, nuclear density, and nuclear binding energy is discussed in terms of a simple model

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

    International Nuclear Information System (INIS)

    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 2.45?1019/m2 at 6MeV and then doped 1?1019/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)

  9. Behavior of helium bubble in helium-doped stainless steel weldment for nuclear power plant

    International Nuclear Information System (INIS)

    The behavior of helium bubble in helium-doped austenitic stainless steel weldment was investigated using scanning electron microscopy, transmission electron microscopy and numerical calculation technique. The stainless steel was helium ion-implanted and welded by YAG laser apparatus. Helium ion implanting to the sample was carried out using 8 MeV implantation apparatus. The sample was doped 1.0x1019 atoms/m2 at 5 MeV and then doped 2.45x1019 atoms/m2 at 6 MeV. The region where helium bubbles formed in the heat-affected zone increased with increasing laser power. For low laser power, the helium concentration was above 10 appm in the weld metal and many large helium bubbles larger than 3 ?m in diameter were observed at the bond region. The volume of weld metal increased and the size of helium bubble decreased with increasing laser power respectively. Number of fine helium bubbles below 0.1 ?m in diameter were observed along the dendrite cell boundary in the weld metal. The increases of laser power and travel speed led to the initiation of cracking at the dendrite cell boundary in the weld metal, even at 2.9 appmHe. (author)

  10. Jet impurity results in helium plasmas

    Science.gov (United States)

    Behringer, K.; Denne, B.; Morgan, P. D.; Stamp, M. F.; Forrest, M. J.

    1989-04-01

    During JET operation in 3He and 4He, a higher density limit is observed than in deuterium, density control is easier and radiation losses are lower during ICRH. Also, there are lasting beneficial effects on subsequent D discharges. Impurity behaviour, particle confinement and residual deuterium content of these plasmas have been studied by visible and VUV spectroscopy. It has been found that He and D influxes are comparable in similar helium and deuterium discharges, respectively, i.e. ? He ? 0.5? D. Release of deuterium, but not helium, from carbon surfaces leads to higher deuterium fractions in ICRH helium plasmas and is responsible for a higher density and radiation increase in deuterium. Impurity diffusion coefficients and confinement times are the same in helium and deuterium plasmas. Nickel concentrations are higher in helium as expected from the higher sputtering yield. Oxygen is almost absent in pure helium discharges and is well correlated with the residual deuterium flux, suggesting a chemical production mechanism. Subsequent to longer periods of helium operation, a lasting reduction of oxygen has also been observed in deuterium plasmas. Carbon concentrations in both helium and deuterium show the signature of physical sputtering, i.e. they increase with I p and decreases with n e. While carbon production and densities in helium can be explained by the theoretical sputtering yields, the situation in deuterium is more complicated owing to the presence of oxygen. The low oxygen levels and the trend of falling carbon concentrations with increasing n e are the reason for the high density limits of helium plasmas.

  11. Helium diffusion in carbonates

    Science.gov (United States)

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

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion directions and the maximum interstitial apertures in each 'slice' in the structure are identified. Preliminary results show that observed differences in diffusivities are consistent with the size of the smallest maximum aperture along each diffusion direction. In calcite, the smallest maximum apertures are ~0.92 and ~0.66 angstroms for cleavage-normal and c-axis parallel directions respectively. In dolomite, the smallest maximum aperture is ~0.78 angstroms for the cleavage normal direction. Work is in progress on characterizing helium diffusion for other orientations in dolomite, and in other carbonates, including aragonite and magnesite, and in implementing these diffusion findings in the interpretation and modeling of bulk volume diffusion in heterogeneous calcite crystals common in many geologic applications. Copeland et al. (2007) GCA 71, 4488-4511 Cherniak and Watson, (2011) Chem. Geo. 288, 149-161

  12. Cooling with Superfluid Helium

    CERN Document Server

    Lebrun, P

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Formation of dianions in helium nanodroplets.

    Science.gov (United States)

    Mauracher, Andreas; Daxner, Matthias; Huber, Stefan E; Postler, Johannes; Renzler, Michael; Denifl, Stephan; Scheier, Paul; Ellis, Andrew M

    2014-12-01

    The formation of dianions in helium nanodroplets is reported for the first time. The fullerene cluster dianions (C60)n(2-) and (C70)n(2-) were observed by mass spectrometry for n?5 when helium droplets containing the appropriate fullerene were subjected to electron impact at approximately 22?eV. A new mechanism for dianion formation is described, which involves a two-electron transfer from the metastable He(-) ion. As well as the prospect of studying other dianions at low temperature using helium nanodroplets, this work opens up the possibility of a wider investigation of the chemistry of He(-), a new electron-donating reagent. PMID:25296629

  15. Metal tritides helium emission

    Energy Technology Data Exchange (ETDEWEB)

    Beavis, L.C.

    1980-02-01

    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 ErT/sub 1/./sub 9/ films). If erbium ditritide is saturated beyond 1.9 T/Er, the critical helium/metal ratio decreases. For example, in bulk powders ErT/sub 2/./sub 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.

  16. Metal tritides helium emission

    International Nuclear Information System (INIS)

    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

  17. Anti-irradiation performance against helium bombardment in bulk metallic glass (Cu47Zr45Al8)98.5Y1.5

    International Nuclear Information System (INIS)

    Highlights: ? This paper used He2+ ion-irradiated metallic glass (Cu47Zr45Al8)98.5Y1.5 and the W metal with the energy of 500 keV. ? There was no significant irradiation damage phenomenon on the surface of metallic glass at different irradiation fluences. ? For irradiated W, the peeling, delamination and flaking appeared numerously at fluences of 1 × 1018 and 2 × 1018 ions/cm2. ? The resistance to He2+ irradiation of metallic glass (Cu47Zr45Al8)98.5Y1.5 was superior to the one in W metal. -- Abstract: In order to compare the resistance to He2+ ion induced irradiation between metallic glass and polycrystal W metal, this paper used different fluences of He2+ ion-irradiated metallic glass (Cu47Zr45Al8)98.5Y1.5 and polycrystal W with an energy of 500 keV. The SRIM simulation calculation results showed that the range (1.19 ?m) of He2+ in metallic glass was greater than the one (0.76 ?m) in polycrystal W. The SEM analysis showed that there was no significant irradiation damage phenomenon on the surface of metallic glass, and there was only a damage layer 1.45 ?m away from the surface when the fluence reached 2 × 1018 ions/cm2. For W, there were surface peeling, flaking and other surface damages at a fluence of 1 × 1018 ions/cm2; when the fluence increased to 2 × 1018 ions/cm2, multilayer detachment phenomenon appeared. The surface root mean square roughness of metallic glass (Cu47Zr45Al8)98.5Y1.5 first increased and then decreased with the increase of fluence. The surface reflectivity of (Cu47Zr45Al8)98.5Y1.5 decreased with the increase of fluence. Through detection by XRD, it was found that (Cu47Zr45Al8)98.5Y1.5 always maintained amorphous phase after different fluences of radiation. The resistance to He2+ irradiation of metallic glass (Cu47Zr45Al8)98.5Y1.5 was superior to the one in polycrystal W

  18. Anti-irradiation performance against helium bombardment in bulk metallic glass (Cu47Zr45Al8)98.5Y1.5

    Science.gov (United States)

    Mei, Xianxiu; Wang, Bin; Dong, Chuang; Gong, Faquan; Wang, Younian; Wang, Zhiguang

    2013-07-01

    In order to compare the resistance to He2+ ion induced irradiation between metallic glass and polycrystal W metal, this paper used different fluences of He2+ ion-irradiated metallic glass (Cu47Zr45Al8)98.5Y1.5 and polycrystal W with an energy of 500 keV. The SRIM simulation calculation results showed that the range (1.19 ?m) of He2+ in metallic glass was greater than the one (0.76 ?m) in polycrystal W. The SEM analysis showed that there was no significant irradiation damage phenomenon on the surface of metallic glass, and there was only a damage layer 1.45 ?m away from the surface when the fluence reached 2 × 1018 ions/cm2. For W, there were surface peeling, flaking and other surface damages at a fluence of 1 × 1018 ions/cm2; when the fluence increased to 2 × 1018 ions/cm2, multilayer detachment phenomenon appeared. The surface root mean square roughness of metallic glass (Cu47Zr45Al8)98.5Y1.5 first increased and then decreased with the increase of fluence. The surface reflectivity of (Cu47Zr45Al8)98.5Y1.5 decreased with the increase of fluence. Through detection by XRD, it was found that (Cu47Zr45Al8)98.5Y1.5 always maintained amorphous phase after different fluences of radiation. The resistance to He2+ irradiation of metallic glass (Cu47Zr45Al8)98.5Y1.5 was superior to the one in polycrystal W.

  19. Fermilab's Central Helium Liquefier capacity upgrade

    International Nuclear Information System (INIS)

    Fermilab's Tevatron Superconducting Accelerator has begun operations of colliding beams of protons and antiprotons at 980 GeV. This has been accomplished by lowering the operating temperature of the Tevatron magnet system from 4.5K to 3.6K using cold compressors on the two-phase portion of the system. The heat of compression by the cold compressors produces a greater liquid helium demand from the Central Helium Liquefier (CHL). Various upgrades have been completed or are in progress to provide sufficient capacity and redundancy for the liquid helium supply. The maximum allowable pressure of the helium system has been raised from 1.31 MPa to 1.65 MPa, thus providing a measured 18% liquefaction capacity increase for same compressors flow. One of four reciprocating helium compressors has been modified for four-stage operations, thus providing 33% increased capacity and more reliable operations. Together with capacity control of individual compressors, the available choice of operation of two 3-stage and two 4-stage compressors will provide the flexibility to operate the Central Helium Liquefier system at the most economical power consumption relative to the liquid helium demand by the accelerator cryogenic system

  20. Fermilab's Central Helium Liquefier capacity upgrade

    Science.gov (United States)

    Geynisman, M. G.; Makara, J. N.

    2002-05-01

    Fermilab's Tevatron Superconducting Accelerator has begun operations of colliding beams of protons and antiprotons at 980 GeV. This has been accomplished by lowering the operating temperature of the Tevatron magnet system from 4.5K to 3.6K using cold compressors on the two-phase portion of the system. The heat of compression by the cold compressors produces a greater liquid helium demand from the Central Helium Liquefier (CHL). Various upgrades have been completed or are in progress to provide sufficient capacity and redundancy for the liquid helium supply. The maximum allowable pressure of the helium system has been raised from 1.31 MPa to 1.65 MPa, thus providing a measured 18% liquefaction capacity increase for same compressors flow. One of four reciprocating helium compressors has been modified for four-stage operations, thus providing 33% increased capacity and more reliable operations. Together with capacity control of individual compressors, the available choice of operation of two 3-stage and two 4-stage compressors will provide the flexibility to operate the Central Helium Liquefier system at the most economical power consumption relative to the liquid helium demand by the accelerator cryogenic system.

  1. In beam tests of implanted helium targets

    International Nuclear Information System (INIS)

    Targets of 3,4He implanted into thin aluminum foils (approximately 100, 200 or 600 ?g/cm2) were prepared using intense helium beams at low energy (20, 40 or 100 keV). Uniformity was achieved by a beam raster across a tantalum collimator at the rates of 0.1 Hz (vertical) and 1 Hz (horizontal). Helium implantation into the very thin (80-100 ?g/cm2) aluminum foils failed to produce useful targets due to an under estimation of the range by SRIM code. The range in aluminum predicted by Northcliffe and Shilling and the NIST online tabulation, on the other hand, over estimate this range. An attempt to implant a second layer was also carried out, but did not significantly increase the helium content beyond the blistering limit. Rutherford Back Scattering of 1.0 and 2.5 MeV proton beams and recoil helium from 15.0 MeV oxygen beams were used to study the helium content and profile. The helium content and profile were very stable even after a prolonged bombardment (two days) with moderately intense beams of 16O or 4He. Helium implanted into thin foils is a good choice, for example, for a measurement of the 3He(?,?)7Be reaction and the associated S34 astrophysical cross section factor (S-factor)

  2. Helium purification system

    International Nuclear Information System (INIS)

    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)

  3. ESCAR helium refrigeration system

    International Nuclear Information System (INIS)

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

  4. Helium dilution refrigerator

    International Nuclear Information System (INIS)

    A new system of continuous heat exchange for a helium dilution refrigerator is proposed. The 3He effluent tube is concurrent with the affluent mixed helium tube in a vertical downward direction. Heat exchange efficiency is enhanced by placing in series a number of elements with an enlarged surface area

  5. 48 CFR 52.208-8 - Required Sources for Helium and Helium Usage Data.

    Science.gov (United States)

    2010-10-01

    ... false Required Sources for Helium and Helium Usage Data. 52.208-8...208-8 Required Sources for Helium and Helium Usage Data. As prescribed...clause: Required Sources for Helium and Helium Usage Data (APR 2002)...

  6. Portable optical helium cryostat with cold windows for ir investigations

    International Nuclear Information System (INIS)

    The design and fabrication details of a portable optical helium cryostat with cold windows are given. The capacity of the helium volume is 1.4 litres allowing a ten hour run at 4.2 K. At a temperature of 1.6 K, achieved by helium pumping, the operating time is 7 to 7.5 hours. The cryostat, 450 mm high and 150 mm diameter, weighs about 5 kg. (U.K.)

  7. Solid helium, a superfluid?

    International Nuclear Information System (INIS)

    At very low temperature, liquid helium becomes superfluid, meaning that it can flow practically without any friction. But what about solid helium? A recent experiment carried out at the Ecole Normale Superieure of Paris (France) has given amazing results: in some conditions some matter can flow through helium without friction. This article makes a synthesis of the experiments carried out on solid helium since the end of the 1960's and which have tried to explain this 'super-solidity' effect. The recent results indicate that the super-solidity of solid helium is linked to its disorder and probably localized at the grain joints, but is not a fundamental property of its crystalline state. (J.S.)

  8. Intense pulsed helium droplet beams

    OpenAIRE

    Slipchenko, Mikhail N.; Kuma, Susumu; Momose, Takamasa; Vilesov, Andrey F.

    2002-01-01

    Pulsed (30 - 100 microseconds) nozzle beams have been used to generate helium droplets ( = 10^4-10^5). The dependence of the beam intensity and the mean droplet size on the source stagnation pressure and temperature are studied via mass spectroscopy and laser induced fluorescence of embedded phthalocyanine molecules. In comparison to a cw beam the pulsed source for the same pressure and temperature has a factor of 100 higher flux and the droplet sizes are an order of a magni...

  9. Intense pulsed helium droplet beams

    CERN Document Server

    Slipchenko, M N; Momose, T; Vilesov, A F; Slipchenko, Mikhail N.; Kuma, Susumu; Momose, Takamasa; Vilesov, Andrey F.

    2002-01-01

    Pulsed (30 - 100 microseconds) nozzle beams have been used to generate helium droplets ( = 10^4-10^5). The dependence of the beam intensity and the mean droplet size on the source stagnation pressure and temperature are studied via mass spectroscopy and laser induced fluorescence of embedded phthalocyanine molecules. In comparison to a cw beam the pulsed source for the same pressure and temperature has a factor of 100 higher flux and the droplet sizes are an order of a magnitude larger.

  10. Co-pumping of deuterium-helium and tritium-helium mixtures at TSTA

    International Nuclear Information System (INIS)

    Future fusion experimental devices and power reactors will pump continuously large amounts of helium, and deuterium and tritium (DT). DT to helium ratios greater than 10:1 are projected. Cryopumps are the logical choice to pump gases in the 100 cubic meter per second range. Compound cryopumps, although complex, have been indicated as the preferred method: these pumps will separately pump helium and DT and will provide to the fuel clean-up system relatively helium free DT gas. Recent study however, shows that helium can be proceeded in the fuel cleanup system, negating the need for separate regeneration. A test program undertaken at Los Alamos evaluated the capability of co-pumping the fusion exhaust gases on a liquid helium cooled surface of activated carbon (coconut charcoal). A compound cryopump installed in the VAC system of the Tritium Systems Test Assembly was used as the test article. In the test program, co-pumping of helium and deuterium and helium-3 and tritium was undertaken. Test results show that co-pumping is practical and that compound pumps may not be required for fusion applications. 5 refs., 7 figs

  11. Studies of helium breakdown at low temperatures

    International Nuclear Information System (INIS)

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

  12. Dynamic model of helium turbine cycle system

    International Nuclear Information System (INIS)

    The one-dimension flow and heat transfer models are built to simulate the components of helium turbine system, including the helium turbine model, compressor model, heat exchanger model, valve model, pipe model and shaft velocity model. The transient simulation code is established in MATLAB. The accident of loss of load and the transient of decreasing heat transfer capacity of the main heat exchanger by 5% are simulated, and important parameters like helium flow rate, temperature, shaft velocity, power rate and compressor surge margin are analyzed. The calculated results agree with the analyzed results. This shows that the present model can be used to simulate the dynamic process of helium turbine closed-cycle system. (authors)

  13. Spectral measurements along the path of N ions impinged into dense helium gas (400 Torr and 5.2 K). II. Excimer reactions dependent on stopping power and large emission yields near the termination of the track

    International Nuclear Information System (INIS)

    Emission spectra and their decay were measured along the path of 4 MeV/amu N ions impinged into dense helium gas near 5.2 K and 420 Torr. Specific scintillation, dL/dX, and scintillation efficiency, dL/dE, for each emission band were measured separately on total, fast initial-rise (-1 cm2: Some of the emissions increased abruptly as the stopping power exceeded this value, while the other emissions decreased or their rates of increase were suppressed. This bend point corresponds to the starting point of a rapidly decreasing yield of delta rays. The result shows that helium has a good scintillation response to high-density excitation occurring at the termination of tracks of N ions, in contrast to usual scintillators, where scintillation decreases abruptly with decreasing delta-ray yield. The large yields of emissions at high-density excitation are explained by the direct excitation, induced emission, and cyclic regeneration of excimers by bimolecular reactions between the nonradiative metastable state, a3, in addition to a very low probability of quenching in helium. Furthermore, it is shown that the present results support the tentative assignment made in part I of this report that theent made in part I of this report that the new triplet bands centered at 4587 A result from an excimer--dimer

  14. Tables of thermodynamic properties of helium magnet coolant: 41 Isobars in the range 1--5 atm and 3--5 K calculated from the equations of state of McCarty

    International Nuclear Information System (INIS)

    The most complete treatment of the thermodynamic properties of helium at the present time is the monograph by McCarty: ''Thermodynamic Properties of Helium 4 from 2 to 1500 K at Pressures to 108 Pa,'' Robert D. McCarty, Journal of Physical and Chemical Reference Data, Vol. 2, page 923--1040 (1973). In this work the complete range of data on helium is examined and the P-V-T surface is described by an equation of state consisting of three functions P(?,T) covering different regions together with rules for making the transition from one region to another

  15. The diffusion of helium in bcc and hexagonal metals

    International Nuclear Information System (INIS)

    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.)

  16. Small size helium refrigerating systems

    International Nuclear Information System (INIS)

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

  17. Helium in Chemically Peculiar Stars

    CERN Document Server

    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 helium abundance have to be determined simultaneously by matching the Balmer line profiles. New MULTI NLTE calculations, performed adopting ATLAS9 model atmospheres and updated helium atomic parameters, reproduce most of the observed equivalent widths of neutral helium lines for main sequence B-type stars and they make us confident of the possibility to correctly derive the helium abundance in chemically peculiar stars. An application of previous methods to the helium rich star HD 37017 shows that helium could be stratified...

  18. Core helium flash

    International Nuclear Information System (INIS)

    The role of convection in the core helium flash is simulated by two-dimensional eddies interacting with the thermonuclear runaway. These eddies are followed by the explicit solution of the 2D conservation laws with a 2D finite difference hydrodynamics code. Thus, no phenomenological theory of convection such as the local mixing length theory is required. The core helium flash is violent, producing a deflagration wave. This differs from the detonation wave (and subsequent disruption of the entire star) produced in previous spherically symmetric violent core helium flashes as the second dimension provides a degree of relief which allows the expansion wave to decouple itself from the burning front. Our results predict that a considerable amount of helium in the core will be burned before the horizontal branch is reached and that some envelope mass loss is likely

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

    CERN Document Server

    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...

  20. Regimes Of Helium Burning

    OpenAIRE

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

    2000-01-01

    The burning regimes encountered by laminar deflagrations and ZND detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts which start with a thermonuclear runaway on the surface of a neutron star, and the thin shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial directions enc...

  1. Superfluidity of Helium-3

    OpenAIRE

    Ma, Tian; Wang, Shouhong

    2008-01-01

    This article presents a phenomenological dynamic phase transition theory -- modeling and analysis -- for liquid helium-3. We derived two new models, for liquid helium-3 with or without applied field, by introducing three wave functions and using a unified dynamical Ginzburg-Landau model. The analysis of these new models leads to predictions of existence of 1) a unstable region, 2) a new phase C in a narrow region, and 3) switch points of transition types on the coexistence c...

  2. On some helium metallization parameters

    International Nuclear Information System (INIS)

    A density minimum of 5 g/cm3, at which the insulator-metal phase transition in helium can take place, has been calculated. The corresponding temperature of this transition of about 9000 K has been estimated. For this purpose, the effective pair ion-to-ion interaction and the electrical resistivity in liquid helium in a vicinity of the transition point into the metallic state are studied in the framework of a nearly free electron model. As a small parameter of the theory, the ratio between, on the one hand, the energy of interaction between conduction electrons and a singly ionized helium atom and, on the other hand, the Fermi energy of electrons was used. The interaction between electrons is taken into account in the framework of the diffraction model of metal, i.e. considering the screening of the electron-to-ion interaction. The exchange interaction and correlations between conduction electrons are taken into account in the local field approximation.

  3. V445 Puppis -- Helium nova on a massive white dwarf

    CERN Document Server

    Kato, M; Kato, Mariko; Hachisu, Izumi

    2003-01-01

    The 2000 outburst of V445 Puppis shows unique properties, such as absence of hydrogen, enrichment of helium and carbon, slow development of the light curve with a small amplitude that does not resemble any classical novae. This object has been suggested to be the first example of helium novae. We calculate theoretical light curves of helium novae and reproduce the observational light curve of V445 Pup. Modeling indicates a very massive white dwarf (WD), more massive than 1.3 Msun. The companion star is possibly either a helium star or a helium-rich main-sequence star. We estimate the ignition mass as several times 10^{-5} Msun, the corresponding helium accretion rate as several times 10^{-7} Msun yr^{-1}, and the recurrence period as several tens of years. These values suggest that the WD is growing in mass and ends up either a Type Ia supernova or an accretion induced collapse to a neutron star.

  4. Helium flooded cryopump with increased hydrogen and helium entrainment factor

    International Nuclear Information System (INIS)

    Superhigh-vacuum helium condensation-sorption pump with H2 and H entrainment factors 1.7 and 3.1 times respectively exceeding those in the known design cryopumps with the same diameters of casings and connecting flange flow sections is described. The N2 pumping-out rate is 6m3/s, the H2 one is 21 m3/s, the H2 pumping-out rate constitutes 12m3/s, the casing diameter is 0.5, the height - 0.8m, mass-35 kg. The pump is fabricated of titanium and aluminium

  5. Helium transfer line installation details.

    CERN Multimedia

    G. Perinic

    2007-01-01

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

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

    International Nuclear Information System (INIS)

    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. Dynamic Simulation of a Helium Liquefier

    International Nuclear Information System (INIS)

    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

  8. Dynamic Simulation of a Helium Liquefier

    Science.gov (United States)

    Maekawa, R.; Ooba, K.; Nobutoki, M.; Mito, T.

    2004-06-01

    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. Calculation of electron-helium scattering

    Energy Technology Data Exchange (ETDEWEB)

    Fursa, D.V.; Bray, I.

    1994-11-01

    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 3{sup 3} 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.

  10. Superfluid helium as a dark matter detector

    International Nuclear Information System (INIS)

    The properties of liquid helium-four at temperatures in the vicinity of 100 mK suggest that it might be a suitable medium from which to construct a detector for certain types of dark matter. Among these properties are freedom from contaminants producing background and a high multiplicity of carriers (rotons) produced in energy deposition. It is suggested that there are processes available in helium which may permit discrimination between recoil nuclei and electrons of equal energy deposit. 19 refs., 5 figs

  11. Helium Neon Laser

    Science.gov (United States)

    Zollman, Dean

    This resource, part of the Spectroscopy Lab Suite, illustrates the physics of a Helium-Neon Laser. Students can create energy levels for both the He and Ne atoms. The basic processes for light emission, including collisions and level transitions, are shown. The atomic energy levels and the pumping energy can be adjusted to achieve an output spectrum similar to the measured physical spectrum.

  12. Broken symmetry makes helium

    CERN Multimedia

    Gray, P L

    2003-01-01

    "The subatomic pion particle breaks the charge symmetry rule that governs both fusion and decay. In experiments performed at the Indiana University Cyclotron Laboratory, physicists forced heavy hydrogen (1 proton + 1 neutron) to fuse into helium in a controlled, measurable environment" (1 paragraph).

  13. Helium leak finding plant

    International Nuclear Information System (INIS)

    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)

  14. Cosmological helium production simplified

    International Nuclear Information System (INIS)

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

  15. The pulsating extreme helium star BD + 1303224

    International Nuclear Information System (INIS)

    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)

  16. Nuclear-physical method for helium determination

    International Nuclear Information System (INIS)

    Nuclear-physical method of helium determination, based on irradiation of investigated sample by 16O ions and recording of energy spectra of helium recoil nuclei, which can be used to acquire quantitative data on helium impurity distribution over the thickness of films of arbitrary composition, is developed. To improve determination sensitivity and to increase the depth of the layer analyzed irradiation is conducted with successive increase in ion beam energy with the pitch 300-500 keV in the rang of 12-50 MeV, and recoil nuclei are recorded in the range of angles 0±5 deg. It is shown that sensitivity and depth of analysis using the method suggested are higher than for the methods of the Rutherford back scattering and the method of recoil nuclei using 12 MeV 14N ion beam

  17. Laser Spectroscopic Measurement of Helium Isotope Ratios

    CERN Document Server

    Wang, L B; Holt, R J; Lu, Z T; O'Connor, T P; Sano, Y; Sturchio, N C

    2003-01-01

    A sensitive laser spectroscopic method has been applied to the quantitative determination of the isotope ratio of helium at the level of 3He/4He = 10^-7 - 10^-5. The resonant absorption of 1083 nm laser light by the metastable 3He atoms in a discharge cell was measured with the frequency modulation saturation spectroscopy technique while the abundance of 4He was measured by a direct absorption technique. The results on three different samples extracted from the atmosphere and commercial helium gas were in good agreement with values obtained with mass spectrometry. The achieved 3-sigma detection limit of 3He in helium is 4 x 10^-9. This demonstration required a 200 micro-L STP sample of He. The sensitivity can be further improved, and the required sample size reduced, by several orders of magnitude with the addition of cavity enhanced spectroscopy.

  18. a Helium Re-Liquefier for Recovering and Liquefying Helium Vapor from Cryostat

    Science.gov (United States)

    Wang, C.

    2010-04-01

    We have developed a helium re-liquefier to provide a solution for recovering and liquefying helium vapor from open-loop helium cryostats. The helium re-liquefier is designed to retrofit into the cryostat and form a closed helium loop for the system. The re-liquefier employs a 4 K pulse tube cryocooler, model PT410, which simultaneously provides 39 W at 45 K and 1.0 W at 4.1 K on the 1st and 2nd stages respectively with a power input of 7.5 kW. The reliquefier can operate in two modes: reliquefying 100% room temperature helium vapor or recondensing and reliquefying two streams of 4.2 K and room temperature vapor at the same time. The reliquefier has a liquefaction rate of 14.2 L/day for the room temperature gas. It has a condensation capacity of recondensing and re-liquefying up to 29 L/day.

  19. Helium diffusion in curium-doped borosilicate waste glass

    International Nuclear Information System (INIS)

    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.

  20. Helium diffusion in curium-doped borosilicate waste glass

    Science.gov (United States)

    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.

  1. Helium diffusion in curium-doped borosilicate waste glass

    Energy Technology Data Exchange (ETDEWEB)

    Fares, T., E-mail: toby.fares@cea.fr [CEA Marcoule, DEN/DTCD/SECM, 30207 Bagnols-sur-Ceze Cedex (France); Peuget, S.; Bouty, O. [CEA Marcoule, DEN/DTCD/SECM, 30207 Bagnols-sur-Ceze Cedex (France); Deschanels, X. [Institut de Chimie Separative de Marcoule, 30207 Bagnols-sur-Ceze Cedex (France); Magnin, M.; Jegou, C. [CEA Marcoule, DEN/DTCD/SECM, 30207 Bagnols-sur-Ceze Cedex (France)

    2011-09-01

    The isothermal release of helium from {sup 244}Cm-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{sup 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) x 10{sup -3} cm{sup 2} s{sup -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.

  2. Metastable states of antiprotonic helium atoms

    International Nuclear Information System (INIS)

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

  3. Elastic scattering of positrons by helium atom

    International Nuclear Information System (INIS)

    Distorted wave method has been employed to calculate differential cross sections for elastic scattering of positrons by helium atom. A suitable form of polarization potential has been used which includes the effects of short-range and long-range correlations. The agreement between the present results and corresponding theoretical predictions and experimental results in the literature are fair. (author). 5 refs., 1 fig

  4. Mobility of. cap alpha. particles in helium

    Energy Technology Data Exchange (ETDEWEB)

    Wadehra, J.M.; Cohen, J.S.; Bardsley, J.N.

    1978-09-01

    The mobility of ..cap alpha.. particles in helium gas is calculated using the zeroth-order Viehland-Mason theory with interaction potentials recently computed by Cohen and Bardsley. The results show a dependence on field strength similar to the measurements of Johnsen and Biondi but are lower in magnitude by about 5%.

  5. Partial Molar Volume of Helium Dissolved in Hydrogen

    Science.gov (United States)

    Smith, Madeline; Pettersen, M. S.

    2009-03-01

    We have determined the partial molar volume v ^' of helium dissolved in hydrogen, by analyzing existing data on the concentrations of the liquid and the coexisting vapor phase at high pressures. The partial molar volume can be found from the chemical potential of the helium in solution (v ^' =?2/ p |T,X2, where ?2 is the chemical potential of the helium in solution, and X2 its concentration), and the chemical potential can be determined from pressure and the concentration of the vapor phase, after applying virial corrections. Both v ^' and the virial terms lead to corrections to Henry's law. Over the range studied (0-50 bar and 15.5-29 K), we find that the partial molar volume of helium is equal to the molar volume of pure hydrogen, within a few percent. The results are relevant to recent experiment on the wetting of cesium by helium/hydrogen solutions, and may also have astrophysical applications.

  6. Helium cooling systems for large superconducting physics detector magnets

    International Nuclear Information System (INIS)

    The large superconducting detector magnets used for high energy physics experiments are virtually all indirectly cooled. In general, these detector magnets are not cryogenically stabilized. Therefore, there are a number of choices for cooling large indirectly cooled detector magnets. These choices include; 1) forced two-phase helium cooling driven by the helium refrigerator J-T circuit, 2) forced two-phase helium cooling driven by a helium pump, and 3) a perculation gravity feed cooling system which uses liquid helium from a large storage dewar. The choices for the cooling of a large detector magnet are illustrated by applying these concepts to a 4.2 meter diameter 0.5 tesla thin superconducting solenoid for an experiment at the Relativistic Heavy Ion Collider (RHIC). (Author)

  7. Small Helium Liquefiers Using 4 K Pulse Tube Cryocoolers

    Science.gov (United States)

    Wang, C.

    2006-04-01

    Two small helium liquefiers using 4 K pulse tube cryocooler have been developed and commercialized at Cryomech, Inc. Model PT405 and PT410 pulse tube cryocoolers used for the liquefiers have cooling capacities of 0.5 W and 1.0 W at 4.2 K respectively. One distinctive advantage of the pulse tube liquefiers is efficient precooling of helium gas to be liquefied with the 1st stage heat exchanger and the 2nd stage regenerator of the cold head. The liquefier with the PT405 liquefies helium from room temperature at a rate of 7.2 Liter/day for 4.6 kW power input. The liquefier with the PT410 has a liquefaction rate of 14.0 liter/day for 8.0 kW power input. The helium liquefiers have been used for a few challenging applications to liquefy and re-condense helium.

  8. Surface flashover in supercritical helium

    International Nuclear Information System (INIS)

    The surface flashover voltage of spacer-type specimens was measured in supercritical helium. The measurement was performed at 4.3 - 7.0 K, and the pressure of 0.8 MPa. The cylindrical spacer-type epoxy specimens filled with silica were used for the measurement of the flashover voltage. The major findings obtained were as follows: (1) Assuming that the flashover voltage is proportional to the n-th power of spacer length, the values of n were 0.92 for direct current, and 0.8 for the standard impulse, respectively. (2) The time lag up to the flashover due to the standard impulse was less than 5 us in most of the cases, (3) When projected electrodes were put in the spacers to lower the electric field between the spacers, gas and the electrodes sufficiently, surface flashover did not occur until the electric field at the center of the spacers became the breakdown voltage of the supercritical helium. (4) When a very small (0.3 mm) projection was made at the contact point of the electrode with the spacer, the surface flashover voltage became significantly low, if the electrode was of negative polarity. Whereas, the change of the flashover voltage was not observed if the polarity was positive. (Aoki, K.)

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

    International Nuclear Information System (INIS)

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

  10. Helium Transfer System for the Superconducting Devices at NSRRC

    Science.gov (United States)

    Li, H. C.; Hsiao, F. Z.; Chang, S. H.; Chiou, W. S.

    2006-04-01

    A helium cryogenic plant with a maximum cooling power of 450 W at 4.5K was installed at the end of the year 2003. This plant has provide the cooling power for the test of one superconducting cavity and the commission of one superconducting magnet for nine months. In November 2004, we installed one helium transfer system in NSRRC's storage ring to fulfill the cooling requirement for the operation of one superconducting cavity and two superconducting magnets. This helium transfer system consists of a switch valve box and the nitrogen-shielding multi-channel transfer lines. The averaged heat leak to the helium process line (including the straight section, the joint, the elbow, the coupling) at liquid helium temperature is specified to be less than 0.1 W/m at 4.2K; the total heat leak of the switching valve box to helium process lines is less than 16 W at 4.2K. In this paper we present the function, design parameters and test result of the helium transfer system. Commissioning results of both the cavity and the magnets using this helium transfer system will be shown as well.

  11. Analysis of decomposition of impurity-helium solid phase

    Science.gov (United States)

    Boltnev, R. E.; Gordon, E. B.; Krushinskaya, I. N.; Martynenko, M. V.; Pelmenev, A. A.; Popov, E. A.; Khmelenko, V. V.; Shestakov, A. F.

    1997-07-01

    The elemental composition of the impurity-helium solid phase (IHSP) grown by injecting of a gas jet containing Ne, Ar, Kr, and Xe atoms and N2 molecules into superfluid HeII is studied. The measured stoichiometric ratios S=NHe/NIm are much larger than the values predicted by the model of frozen together monolayer helium clusters. The theoretical possibility of freezing together of two-layered clusters is justified in the continual model of the helium subsystem of IHSP which fills the space between rigid impurity centers. Regularities of decomposition of "dry" samples (extracted from liquid helium) are analyzed in the temperature range 1.5-12 K under pressures from 10 to 500 torr. Two stages of sample decomposition are discovered: a slow stage accompanied by cooling and a rapid stage accompanied by heat release. These results suggest the presence of two types of helium in IHSP, viz., weakly bound and strongly bound helium which can be attributed respectively to the second and first coordination spheres of helium formed around heavy impurity particles. A tendency to elevation of the thermal stability of impurity-helium (IH) samples upon an increase in the mass of impurity center has been observed. An increase in the helium vapor pressure above the samples also increases their stability. It is found that the decomposition of IH samples containing nitrogen atoms in the temperature range 3-4.5 K is accompanied with luminescence induced by recombination of atoms. This indicates the possibility of a wide range of chemical reactions in solidified helium.

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

    International Nuclear Information System (INIS)

    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 ?p = 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)

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

    CERN Document Server

    Jianqin, Zhang; Zhuo, Zhang; Rui, Ge

    2015-01-01

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

  14. Compressibility of solid helium

    International Nuclear Information System (INIS)

    The compressibility of solid helium (3He and 4He) in the hcp and fcc phases has been studied by the path-integral Monte Carlo method. Simulations were carried out in both canonical (NVT) and isothermal-isobaric (NPT) ensembles at temperatures between 10 and 300 K, showing consistent results in both ensembles. For pressures between 4 and 10 GPa, the bulk modulus B is found to decrease by about 10%, when the temperature increases from the low-temperature limit to the melting temperature. The isotopic effect on the bulk modulus of helium crystals has been quantified for a wide range of parameters. At 25 K and pressures on the order of 1 GPa, the relative difference between 3He and 4He amounts to about 2%. The thermal expansion has also been quantified from results obtained in both NPT and NVT simulations

  15. Feasibility of lunar Helium-3 mining

    Science.gov (United States)

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

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

  16. Experimental study on helium cryogenic ejector

    International Nuclear Information System (INIS)

    The helium cryogenic ejector intended for thermal regulation of objects at temperatures below 4.2 deg K is elaborated and tested. Geometric dimensions of the ejector have been determined with the following initial data, consumption of compressed helium 27.8 gr/sec, input temperature 6.1 deg K, input pressure 24.5 bar, output pressure 1.32 bar, load 30 w. The paper presents a diagram of the test bench, geometric dimensions and characteristics of the ejector operating together with a helium refrigerator - liquefier. As a result of the experimental studies dependences of helium vapour temperatures upon the load at the same temperature have been obtained along with a value of the hydraulic resistance of the suction duct as well as an optimal distance between the nozzle and mixing chamber. It has been proved that the nozzle should be placed inside the mixing chamber for 2.5 mm 2.38 deg K has been obtained at a load of 30 w. At a no-load operation a temperature of 2.0 deg K has been obtained

  17. Antiprotonic helium atomcules

    Directory of Open Access Journals (Sweden)

    Sauge Sébastien

    2012-10-01

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

  18. Education in Helium Refrigeration

    International Nuclear Information System (INIS)

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

  19. Reduction of helium ash by selective helium pumping

    International Nuclear Information System (INIS)

    The concept of the reduction of the helium ash concentration in a fusion plasma, based on selective pumping of helium ions, is discussed. Where this procedure is employed together with the pumping of a divertor, the helium ash concentration may be considerably reduced. Thus, this method might be helpful to sustain the burning plasma state or the ignition condition. The pumping condition required for the selective pumping metal is also discussed. ((orig.))

  20. Surface electrons of helium films

    International Nuclear Information System (INIS)

    Theoretical calculations of some properties of two-dimensional electrons on a liquid helium film adsorbed on a solid substrate are reviewed. We describe the spectrum of electron bound states on bulk helium as well on helium films. The correlational properties, such as the structure factor and correlation energy, are determined as functions of the film thickness for different types of substrates in the framework of a Generalized Random-Phase Approximation. The collective excitations of this system are also described. The results for electrons on the surface of thin films and bulk helium are easily obtained. we examine the electron interaction with the excitations of the liquid helium surface resulting in a new polaron state, which was observed very recently. The ground state energy and the effective mass of this polaron are determined by using the path-integral formalism and unitary-transformation method. Recent speculations about the phase diagram of electrons on the helium film are also discussed. (Author)

  1. Use of helium in uranium exploration, Grants district

    International Nuclear Information System (INIS)

    The continuous generation of inert helium gas from uranium and its daughter products provides a potentially useful means for remote detection of uranium deposits. The practicality of conducting helium surveys in the atmosphere, soil gas, and ground water to explore for buried uranium deposits has been tested in the Grants district and in the Powder River Basin of Wyoming. No detectable helium anomalies related to buried or surface uranium deposits were found in the atmosphere. However, reproducible helium-in-soil-gas anomalies were detected spatially related to uranium deposits buried from 50 to 800 ft deep. Diurnal and atmospheric effects can cause helium content variations (noise) in soil gas that are as great as the anomalies observed from instantaneous soil-gas samples. Cumulative soil-gas helium analyses, such as those obtained from collecting undisturbed soil samples and degassing them in the laboratory, may reveal anomalies from 5 to 100 percent above background. Ground water samples from the Grants district, New Mexico, and the Powder River Basin, Wyoming, have distinctly anomalous helium values spatially related to buried uranium deposits. In the southern Powder River Basin, helium values 20 to 200 percent above background occur 2 to 18 mile down the ground-water flow path from known uranium roll-front deposits. In the Grants district, helium contents 40 to 700 percent above background levels are present in ground waters from the host sandstone in the viciniters from the host sandstone in the vicinity of uranium deposits and from aquifers up to 3,000 ft stratigraphically above the deep uranium deposits. The use of helium in soil and ground-water surveys, along with uranium and radon analyses of the same materials, is strongly recommended is expensive, deep, uranium-exploration programs such as those being conducted in the Grants district

  2. K-shell x-ray production cross-sections in carbon, oxygen, fluorine, sodium, magnesium, and aluminum by 0.5 to 8.0 MeV protons, helium, and lithium ions

    International Nuclear Information System (INIS)

    X-ray production cross sections are reported for elements with K-shell x-ray energies between 277 eV (C) and 1487 eV (Al). These data are reported for incident ions in the energy range 0.5 to 8.0 MeV. These measurements were performed using the 3 MV tandem accelerator at the University of North Texas Ion Beam Modification and Analysis Laboratory. The x-ray measurements were made with a windowless Si(Li) detector that was calibrated for efficiency by comparing bremsstrahlung spectra from electron bombardment of aluminum, silver, and gold with theoretically determined bremsstrahlung spectral distributions. The experimental results of the x-ray cross sections are compared to the predictions of both the first Born and the ECPSSR ionization the theories using single-hole fluorescence yields; each of which is composed of two parts; the direct ionization (DI) of the target electron to the continuum and the capture (EC) of the target electron to the projectile. The first Born theory describes DI by the Plane-Wave-Born-Approximation (PWBA) and EC by the Oppenheimer-Brinkman-Kramers treatment of Nikolaev (OBKN). The ECPSSR theory accounts for the energy loss (E) and Coulomb deflection (C) of the projectile as well as for the perturbed stationary states (PSS) and the relativistic nature (R) of inner shell electrons. The ECPSSR and first Born theoretical predictions are, in close agreement with each other and both generally, fit the proton data quite well. For incident helium andn data quite well. For incident helium and lithium ions, most of the measurement results compare quite favorably with the ECPSSR theory

  3. Helium-3 from the moon

    International Nuclear Information System (INIS)

    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

  4. Isolating electrons on superfluid helium

    Science.gov (United States)

    Takita, Maika; Lyon, S. A.

    2014-12-01

    Electrons floating on the surface of superfluid helium have been suggested as promising mobile spin quantum bits (qubits). Transferring electrons extremely efficiently in a narrow channel structure with underlying gates has been demonstrated, showing no transfer error while clocking 109 pixels in a 3-phase charge coupled device (CCD). While on average, one electron per channel was clocked, it is desirable to reliably obtain a single electron per channel. We have designed an electron turnstile consisting of a narrow (0.8?m) channel and narrow underlying gates (0.5?m) operating across seventy-eight parallel channels. Initially, we find that more than one electron can be held above the small gates. Underlying gates in the turnstile region allow us to repeatedly split these electron packets. Results show a plateau in the electron signal as a function of the applied gate voltages, indicating quantization of the number of electrons per pixel, simultaneously across the seventy-eight parallel channels.

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

    International Nuclear Information System (INIS)

    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

  6. Estimation of helium in gas mixture using helium leak detector

    International Nuclear Information System (INIS)

    A method is described for using helium leak detector for determining the helium content in gas mixtures. Details of various attachments for sample handling and other modifications needed are outlined. Sources of error and the respective corrections are indicated. Procedure for the analysis of samples in percentage, ppm and sub ppm has been standardised. Precision of analysis for these concentrations is mentioned. (auth.)

  7. Kinetics helium evolution from steel OKh16N15M3B irradiated with helium ions

    International Nuclear Information System (INIS)

    Investigated is gas evolution from the samples of stainless 0Kh16N15M3B steel irradiated by helium ions with an energy of 800 keV up to the doses 5x1016 - 1.2x1018 cm-2 at 50 deg C. Gas evolution and change of the surface structure has been comupon heating the samples with constant pared with analogous processes rate from 50 to 1300 deg C. Some stages have been observed on gas evolution curves. The results obtained show that the character of helium thermodesorption depends on the implantation dose. If at doses of 16 cm-2 the helium evolution proceeds along one channel only, then the number of thermodesorption channels increases up to five with increasing the dose. The measured values of activation energy and the data on a change in the sample surface structure make it possible to judge on the mechanisms of gas evolution along each of channels

  8. 21 CFR 184.1355 - Helium.

    Science.gov (United States)

    2010-04-01

    ...2010-04-01 2009-04-01 true Helium. 184.1355 Section 184...Affirmed as GRAS § 184.1355 Helium. (a) Helium (empirical formula He...produced by the liquefaction and purification of natural gas. (b)...

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

    International Nuclear Information System (INIS)

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

  10. Supersolid transition of helium-4

    Science.gov (United States)

    Kim, Eunseong

    The first experimental observation of supersolid 4He is presented for both bulk solid helium and solid 4He confined in porous media. Non-Classical Rotational Inertia (NCRI), direct evidence of the existence of a supersolid, is detected by the reduction in the resonant period of the torsional oscillator. For bulk solid 4He torsional oscillator measurements have been performed in the temperature range of 0.02K to 2K, for pressures between 26 bars and 66 bars. Below 0.23K, non-classical rotational inertia is detected by a sharp drop in the resonant period of the torsional oscillator, indicating entry into a supersolid phase. The temperature dependence of the supersolid fraction exhibits a universal behavior of an exponential-like rise with decreasing temperature and then a saturation in the low temperature limit. This temperature dependence is distinct from BEC in other systems such as superfluid liquid helium and dilute atomic gases. For all pressures a very strong dependence of non-classical rotational inertia on the oscillation speed is observed. The scatter in the supersolid fraction, varying between 0.7% and 1%, makes it difficult to conclude if there is any trend of the supersolid fraction with increasing pressure. Solid 4He confined in porous Vycor glass has been studied between 0.03K and 2K, for pressures ranging from 40 to 65 bars. NCRI is detected below 0.175K for all samples that we have studied. The fractional NCRI at low temperature ranges from 0.2% to 0.5%. The presence of disordered porous media does not alter the supersolid transition. The fractional NCRI of solid 4He confined in Vycor glass resembles that of bulk solid 4 He, exhibiting strong oscillation speed dependence as well as an universal temperature dependence. For solid mixtures with very dilute concentration of 3He reveals a very intriguing behavior. The addition of 3He not only broadens the transition but also enhances the transition temperature as opposed to the effect of 3He in the superfluid helium.

  11. The Hall D solenoid helium refrigeration system at JLab

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Science.gov (United States)

    Fu, Bao; Zhang, Qiyong; Zhu, Ping; Cheng, Anyi

    2014-05-01

    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.

  13. Behavior of helium gas atoms and bubbles in low activation 9Cr martensitic steels

    International Nuclear Information System (INIS)

    The behavior of helium-gas release from helium-implanted 9Cr martensitic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V were investigated. Cold-worked AISI 316 austenitic stainless steel was also investigated as a reference which was susceptible helium embrittlement at high temperature. A helium release peak was observed at the moment of rupture in all the specimens. The total quantity of helium released from these 9Cr steels was in the same range but smaller than that of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement. ((orig.))

  14. The influence of preimplanted helium on the microstructure of neutron irradiated vanadium

    International Nuclear Information System (INIS)

    The influence of preimplanted helium on the microstructure of 99.9% pure vanadium and a dilute vanadium alloy V-1% Cr-0.1% Ti, neutron irradiated at 813 K to 4.5 x 1025 n.m-2 (E > 0.1 MeV), has been investigated. The helium content ranged up to 1000 at. ppm. Helium was found to depress the concentration and volume fraction of the cavities in vanadium and to increase their size. The effect was observed to be independent of the amount of implanted helium. For the alloy preimplantation with helium had the opposite effect, i.e. smaller cavities and a higher concentration. The volume fraction of the cavities in the alloy, which was considerably smaller than for vanadium, was not clearly influenced by the helium. The size and concentration of the cavities in the alloy also did not appear to depend on the amount of implanted helium. (orig.)

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

    CERN Multimedia

    Davide Vitè

    2002-01-01

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

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

    CERN Multimedia

    Davide Vitè

    2002-01-01

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

  17. Helium exhaust studies in the DIII-D tokamak

    International Nuclear Information System (INIS)

    Significant exhaust of thermal helium in a diverted, H-mode deuterium plasma has been demonstrated for the first time on the DIII-D tokamak using an in-vessel cryopump conditioned with an argon frost. 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 similar 8-15 energy confinement times. Detailed analysis of the helium profile evolution indicates that the exhaust rate is limited by the exhaust efficiency of the pump ( similar 5%) and not by the intrinsic helium transport properties of the plasma. Additional studies focusing on the recycling properties of helium relative to deuterium in the divertor region indicate some dependence of the helium concentration in the divertor pumping plenum on the divertor outer strike-point (OSP) position in Ohmic discharges. However, the helium concentration in the plenum appears to have little dependence on OSP position in beam-heated, ELMing H-mode discharges. ((orig.))

  18. Helium exhaust studies in the DIII-D tokamak

    International Nuclear Information System (INIS)

    Significant exhaust of thermal helium in a diverted, H-mode deuterium plasma has been demonstrated for the first time on the DIII-D tokamak using an in-vessel cryopump conditioned with an argon frost. 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 ?8-15 energy confinement times. Detailed analysis of the helium profile evolution indicates 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. Additional studies focusing on the recycling properties of helium relative to deuterium in the divertor region indicate some dependence of the helium concentration in the divertor pumping plenum on the divertor outer strike-point (OSP) position in Ohmic discharges. However, the helium concentration in the plenum appears to have little dependence on OSP position in beam-heated, ELMing H-mode discharges

  19. Ultralow temperature helium compressor for Japan Atomic Energy Research Institute

    International Nuclear Information System (INIS)

    Ishikawajima Harima Heavy Industries Co., Ltd. started the development of an ultralow temperature helium compressor for helium liquefaction in 1984 jointly with Japan Atomic Energy Research Institute, and has delivered the first practical machine to the Superconductive Magnet Laboratory of JAERI. For a large superconductive magnet to be used in the stable state for a fusion reactor, conventional superconductive materials (NbTi, NbTi3Sn, etc.) must be used, being cooled forcibly with supercritical helium. The supercritical helium which is compressed above the critical pressure of 228 kPa has a stable cooling effect since the thermal conductivity does not change due to the evaporation of liquid helium. In order to maintain the temperature of the supercritical helium below 4 K before it enters a magnet, a heat exchanger is used. The compressor that IHI has developed has the ability to reduce the vapor pressure of liquid helium from atmospheric pressure to 50.7 kPa, and can attain the temperature of 3.5 K. The specification of this single stage centrifugal compressor is: mass flow rate 25 - 64 g/s, speed 80,000 rpm, adiabatic efficiency 62 - 69 %. The structure and the performance are reported. (K.I.)

  20. Evaluation of helium cooling for fusion divertors

    International Nuclear Information System (INIS)

    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 rr required was less than 1% of the power removed. These results verified the design prediction. ((orig.))

  1. Evaluation of helium cooling for fusion divertors

    Science.gov (United States)

    Baxi, C. B.

    1993-09-01

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

  2. Evaluation of helium cooling for fusion divertors

    International Nuclear Information System (INIS)

    The divertors of future fusion reactors will have a power throughput of several hundred MW. The peak heat flux on the diverter surface is estimated to be 5 to 15 MW/m2 at an average heat flux of 2 MW/m2. The divertors have a requirement of both minimum temperature (100 degrees C) and maximum temperature. The minimum temperature is dictated by the requirement to reduce the absorption of plasma, and the maximum temperature is determined by the thermo-mechanical properties of the plasma facing materials. Coolants that have been considered for fusion reactors are water, liquid metals and helium. Helium cooling has been shown to be very attractive from safety and other considerations. Helium is chemically and neutronically inert and is suitable for power conversion. The challenges associated with helium cooling are: (1) Manifold sizes; (2) Pumping power; and (3) Leak prevention. In this paper the first two of the above design issues are addressed. A variety of heat transfer enhancement techniques are considered to demonstrate that the manifold sizes and the pumping power can be reduced to acceptable levels. A helium-cooled diverter module was designed and fabricated by GA for steady-state heat flux of 10 MW/m2. This module was recently tested at Sandia National Laboratories. At an inlet pressure of 4 MPa, the module was tested at a steady-state heat flux of 10 MW/m2. The pumping power required was less than 1% of the power removed. These results verified the design prediction

  3. Regimes Of Helium Burning

    CERN Document Server

    Timmes, F X

    2000-01-01

    The burning regimes encountered by laminar deflagrations and ZND detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts which start with a thermonuclear runaway on the surface of a neutron star, and the thin shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial directions encounter a transition from the distributed regime to the flamlet regime at a density of 10^8 g cm^{-3}. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than 10^6 g cm^{-3}. Self-sustained laminar deflagrations travelling in the radial direction cannot exist below this density. Similarily, the planar ZND detonation width becomes larger than the pressure scale height at 10^7 g cm^{-3}, suggesting that a steady-state, self-sustained detonations cannot come into exista...

  4. Neon-helium refrigerator

    International Nuclear Information System (INIS)

    To construct economical facilities of preliminary cooling a neon-helium refrigerator is designed and produced in Which a generator gas (helium) is successively cooled at three temperature levels - 78 K, 64 K and 28 K. The first two levels are ensUred by liquid nitrogen, and the third one by a throttle neon refrigerator of 400 W cooling capacity at the 28 K level, at the 45 m3/h neon compressor capacity. The rig trials of the refrigerator were carried out. Its real cooling capacity was 270 W while working with a compressor at the 31 m3/h capacity. This fact is in good agreement with the calculations taking into account that the practical neon compressor capacity is less than the calculated one. The refrigerator efficiency depending on the cooling object temperature is calculated. The optimal cooling conditions are determined from the power point of view. The dynamics of object cooling is considered. It is shown that when utilizing multi-stage cooling of cryogenic objects it is necessary to determine optimal temperatures of transition from one cooling stage to another, that permits to minimize expenditure of energy during cooling process

  5. Helium liquefying plants in France

    International Nuclear Information System (INIS)

    The main types of helium liquefiers encountered are described and then the French installations are listed and detailed. The problems encountered in different parts of the installations (liquefier, recovery system, purifying, ...) during the last few years are discussed. In a final section about the economics of liquefaction, the cost of liquefying helium and nitrogen is compared with the cost of purchasing these liquids commercially

  6. Determining carbon dioxide in helium by adsorption accumulation

    International Nuclear Information System (INIS)

    A combined isotopic, chromatographic, and spectral method has been developed for determining CO2 in helium by the use of adsorption accumulation and chromatography at reduced pressures. The lower limit to the measurable contents is 5 x 10-6 mol%. The method does not require the use of reference specimens. The scope for reducing abundant isotope content is related to increased accuracy in the spectroscopic determination of CO2 isotope compositions and increasing the volume of helium used

  7. Helium in near Earth orbit

    CERN Document Server

    Alcaraz, J; Ambrosi, G; Anderhub, H; Ao, L; Arefev, A; Azzarello, P; Babucci, E; Baldini, L; Basile, M; Barancourt, D; Barão, F; Barbier, G; Barreira, G; Battiston, R; Becker, R; Becker, U; Bellagamba, L; Béné, P; Berdugo, J; Berges, P; Bertucci, B; Biland, A; Bizzaglia, S; Blasko, S; Bölla, G; Boschini, M; Bourquin, Maurice; Brocco, L; Bruni, G; Buénerd, M; Burger, J D; Burger, W J; Cai, X D; Camps, C; Cannarsa, P; Capell, M; Casadei, D; Casaus, J; Castellini, G; Cecchi, C; Chang, Y H; Chen, H F; Chen, H S; Chen, Z G; Chernoplekov, N A; Tzi Hong Chiueh; Chuang, Y L; Cindolo, F; Commichau, V; Contin, A; Cristinziani, M; Da Cunha, J P; Dai, T S; Deus, J D; Dinu, N; Djambazov, L; D'Antone, I; Dong, Z R; Emonet, P; Engelberg, J; Eppling, F J; Eronen, T; Esposito, G; Extermann, Pierre; Favier, Jean; Fiandrini, E; Fisher, P H; Flügge, G; Fouque, N; Galaktionov, Yu; Gervasi, M; Giusti, P; Grandi, D; Grimm, O; Gu, W Q; Hangarter, K; Hasan, A; Hermel, V; Hofer, H; Huang, M A; Hungerford, W; Ionica, M; Ionica, R; Jongmanns, M; Karlamaa, K; Karpinski, W; Kenney, G; Kenny, J; Kim, W; Klimentov, A; Kossakowski, R; Koutsenko, V F; Kräber, M H; Laborie, G; Laitinen, T; Lamanna, G; Laurenti, G; Lebedev, A; Lee, S C; Levi, G; Levchenko, P M; Liu, C L; Liu Hong Tao; Lopes, I; Lu, G; Lü, Y S; Lübelsmeyer, K; Luckey, D; Lustermann, W; Maña, C; Margotti, A; Mayet, F; McNeil, R R; Meillon, B; Menichelli, M; Mihul, A; Mourão, A M; Mujunen, A; Palmonari, F; Papi, A; Park, I H; Pauluzzi, M; Pauss, Felicitas; Perrin, E; Pesci, A; Pevsner, A; Pimenta, M; Plyaskin, V; Pozhidaev, V; Pohl, M; Postolache, V; Produit, N; Rancoita, P G; Rapin, D; Raupach, F; Ren, D; Ren, Z; Ribordy, M; Richeux, J P; Riihonen, E; Ritakari, J; Röser, U; Roissin, C; Sagdeev, R; Sartorelli, G; Schultz von Dratzig, A; Schwering, G; Scolieri, G; Seo, E S; Shoutko, V; Shoumilov, E; Siedling, R; Son, D; Song, T; Steuer, M; Sun, G S; Suter, H; Tang, X W; Ting, Samuel C C; Ting, S M; Tornikoski, M; Torsti, J; Trümper, J E; Ulbricht, J; Urpo, S; Usoskin, I; Valtonen, E; Van den Hirtz, J; Velcea, F; Velikhov, E P; Verlaat, B; Vetlitskii, I; Vezzu, F; Vialle, J P; Viertel, Gert M; Vitè, Davide F; Von Gunten, H P; Waldmeier-Wicki, S; Wallraff, W; Wang, B C; Wang, J Z; Wang, Y H; Wiik, K; Williams, C; Wu, S X; Xia, P C; Yan, J L; Yan Lu Guang; Yang, C G; Yang, M; Ye Shu Wei; Yeh, P; Xu, Z Z; Zhang, H Y; Zhang, Z P; Zhao, D X; Zhu, G Y; Zhu, W Z; Zhuang, H L; Zichichi, A; Zimmermann, B; Zuccon, P

    2000-01-01

    The helium spectrum from 0.1 to 100 GeV/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV/nucleon the flux was measured to be (6.3+or-0.9)*10/sup -3/ (m/sup 2/ sec sr)/sup -1/ and more than ninety percent of the helium was determined to be /sup 3/He (at the 90% CL). Tracing helium from the second spectrum shows that about half of the /sup 3/He travel for an extended period of time in the geomagnetic field and that they originate from restricted geographic regions similar to protons and positrons. (22 refs).

  8. Ultrasensitive leak testing: helium accumulation

    International Nuclear Information System (INIS)

    An investigation was carried out to develop a technique for detecting leak rates of less than 1 x 10-11 atm cm3/sec in order to measure the helium leak rate of radioisotopic heat sources. These heat sources consist of 238PuO2 triply sealed in welded containers under a helium atmosphere. A static accumulation method was developed to perform leakage measurements in the range of 10-10 to 10-13 atm cm3/sec since commercially available heliium leak detectors cannot measure dynamic helium leak rates of less than about 10-10 atm cm3/sec. It has been experimentally determined that the accumulation system can measure helium leakages in the range of 10-10 to 10-13 atm cm3/sec. Random system errors of +-10 percent were found which are well within the limits of accuracy of +-20 percent given for the calibrated helium leak rate standards

  9. Laser Spectroscopic Measurement of Helium Isotope Ratios

    OpenAIRE

    Wang, L. -b; Mueller, P.; Holt, R. J.; Lu, Z. -t; O Connor, T. P.; Sano, Y.; Sturchio, N. C.

    2003-01-01

    A sensitive laser spectroscopic method has been applied to the quantitative determination of the isotope ratio of helium at the level of 3He/4He = 10^-7 - 10^-5. The resonant absorption of 1083 nm laser light by the metastable 3He atoms in a discharge cell was measured with the frequency modulation saturation spectroscopy technique while the abundance of 4He was measured by a direct absorption technique. The results on three different samples extracted from the atmosphere an...

  10. Correlation of Helium Solubility in Liquid Nitrogen

    Science.gov (United States)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

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

  11. Safety analysis of a supercritical helium dewar

    International Nuclear Information System (INIS)

    A proposed supercritical helium dewar is to be maintained at about 5 K and 0.317 MPa. In case of a postulated catastrophic event when the outer vacuum vessel is damaged, air will leak into the vacuum insulation space. Present analysis verifies that the fill and vent lines can accommodate the increased flow of vent gas to keep pressure inside the dewar below the design limit

  12. Effect of radiation damage in thermal desorption of helium from the ferritic-martensitic steel EP-450

    International Nuclear Information System (INIS)

    The results of the study of helium thermal desorption from polycrystalline samples of steel EP-450 implanted helium ions with energy of 12 keV to doses (5 - 10 1016 cm-2 are given. The effect of precreated damage to the spectra of helium is considered. A comparison of temperature intervals of helium desorption from the ferriticmartensitic steel EP-450, nickel and iron are conducted.

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

    International Nuclear Information System (INIS)

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, J.C.; Kellman, D.H.; Hong, R.; Kim, J.; Laughon, G.M.

    1995-10-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-10-15

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

  16. 3He NMR studies on helium-pyrrole, helium-indole, and helium-carbazole systems: a new tool for following chemistry of heterocyclic compounds.

    Science.gov (United States)

    Radula-Janik, Klaudia; Kupka, Teobald

    2015-02-01

    The (3)He nuclear magnetic shieldings were calculated for free helium atom and He-pyrrole, He-indole, and He-carbazole complexes. Several levels of theory, including Hartree-Fock (HF), Second-order Møller-Plesset Perturbation Theory (MP2), and Density Functional Theory (DFT) (VSXC, M062X, APFD, BHandHLYP, and mPW1PW91), combined with polarization-consistent pcS-2 and aug-pcS-2 basis sets were employed. Gauge-including atomic orbital (GIAO) calculated (3)He nuclear magnetic shieldings reproduced accurately previously reported theoretical values for helium gas. (3)He nuclear magnetic shieldings and energy changes as result of single helium atom approaching to the five-membered ring of pyrrole, indole, and carbazole were tested. It was observed that (3)He NMR parameters of single helium atom, calculated at various levels of theory (HF, MP2, and DFT) are sensitive to the presence of heteroatomic rings. The helium atom was insensitive to the studied molecules at distances above 5?Å. Our results, obtained with BHandHLYP method, predicted fairly accurately the He-pyrrole plane separation of 3.15?Å (close to 3.24?Å, calculated by MP2) and yielded a sizable (3)He NMR chemical shift (about -1.5?ppm). The changes of calculated nucleus-independent chemical shifts (NICS) with the distance above the rings showed a very similar pattern to helium-3 NMR chemical shift. The ring currents above the five-membered rings were seen by helium magnetic probe to about 5?Å above the ring planes verified by the calculated NICS index. PMID:25228253

  17. Shock Experiments on Pre-Compressed Fluid Helium

    International Nuclear Information System (INIS)

    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.

  18. Cooling of small SMES system with forced flow supercritical helium

    Science.gov (United States)

    Schöttler, R. M.

    Technische Universität München (Lehrstuhl für Elektrische Maschinen) is currently constructing a small superconducting magnetic energy storage (SMES) system. Six coils, forming a torus, store 1.4 MJ of energy at 1360 A maximum current. Simulations show that the fastest charge/discharge cycle time that can be realized is 1.5 s. The coils are cooled indirectly by supercritical helium in a closed forced flow circuit. To obtain low cable temperatures even at high superconductor losses the helium is recooled with intermediate heat exchangers by boil-off from two pools of liquid helium. This paper discusses the plant's capability in different load cycles with respect to the refrigeration capacity, where the superconductor losses and the coil and helium temperatures are calculated. In addition, the pressure rise in the cooling tube during coil quench is investigated.

  19. Thermal conductivity of the helium-argon system

    International Nuclear Information System (INIS)

    A semiempirical relation for the thermal conductivity of helium--argon gas mixtures is suggested. The analyses used in support of the proposed conductivity relations are based on low-temperature (T 0C) thermal conductivity data for helium, argon and helium--argon mixtures. The report is a compilation of available data and theories, and does not contain any new experimental results. With the approach presented here, one should be able to predict thermal conductivities of helium--argon mixtures to within 5% of their true values for temperatures up to 1200 K. The recommended equations are best estimates and should be treated as such. A definite need exists for experimental data to verify or modify the recommendation

  20. Effects of trapping and detrapping of helium on void nucleation

    International Nuclear Information System (INIS)

    A model of steady-state void nucleation in the presence of mobile helium has recently been developed. The model is based on a reaction-rate formulation of nucleation theory and includes vacancy, interstitial, and gas capture; vacancy emission; and gas emission by three mechanisms--thermal detrapping, radiation displacement, and interstitial knockout of helium from voids ''filled'' with gas. The free (interstitial) helium concentration, the free-vacancy concentration, and nucleation rates are calculated as functions of the displacement rate, temperature, and substitutional (trapped) helium concentration. The void-nucleation rate in nickel is found to be significantly enhanced by the gas for displacement rates in the reactor range (n = 10-5 s-1) at temperatures above approx.5000C

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

    Science.gov (United States)

    Yu, Jinnan; Zhao, Xinjie; Zhang, Wen; Yang, Wen; Chu, Fengmin

    1997-11-01

    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 Cr 2O 3, (CrFe) 2O 3, (Fe 5C 2)28N, (CrMo)N, (Fe 2Mo)12H and (FeNi) 9S 8. 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 10 17-8 × 10 18 ions/cm 2 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 × 10 17 He +/cm 2), 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.

  2. Precision spectroscopy of Helium

    International Nuclear Information System (INIS)

    Accurate Quantum-Electrodynamics (QED) tests of the simplest bound three body atomic system are performed by precise laser spectroscopic measurements in atomic Helium. In this paper, we present a review of measurements between triplet states at 1083 nm (23S-23P) and at 389 nm (23S-33P). In 4He, such data have been used to measure the fine structure of the triplet P levels and, then, to determine the fine structure constant when compared with equally accurate theoretical calculations. Moreover, the absolute frequencies of the optical transitions have been used for Lamb-shift determinations of the levels involved with unprecedented accuracy. Finally, determination of the He isotopes nuclear structure and, in particular, a measurement of the nuclear charge radius, are performed by using hyperfine structure and isotope-shift measurements

  3. Pion productions by proton and Helium-3 on Au197 target at beam energies of 2.8, 5, 10 and 16.587 GeV/nucleon

    CERN Document Server

    Yong, Gao-Chan; Xu, Hu-Shan; Zuo, Wei

    2011-01-01

    Based on a Relativistic Boltzmann-Uehling- Uhlenbeck transport model, proton and $^{3}$He induced reactions on $^{197}$Au target at beam energies of 2.8, 5, 10 and 16.587 GeV/nucleon are studied. It is found that compared with proton induced reaction, $^{3}$He induced reaction gives a large cross section of pion production, about 5 times larger than proton induced reaction. And more importantly, pion production from $^{3}$He induced reaction is more inclined to low-angle emission. Neutrino production via positively charged pion is also discussed accordingly.

  4. Exotic helium molecules

    International Nuclear Information System (INIS)

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

  5. Elastic scattering of electrons in helium

    International Nuclear Information System (INIS)

    Differential elastic cross section measurements are reported for electron scattering in helium at incident electron energies of 7.5, 10.0, 12.5, 15.0 and 17.5 eV and at scattering angles of 20-1300. The measurements were made using a new type of electron spectrometer employing co-axial cones to analyse the electrons. A phaseshift analysis is applied to the data and the results are compared with recent theoretical and experimental work. Total elastic and momentum transfer cross section values are also derived from the present measurements and compared with recent measurements and calculations. (author)

  6. A helium cryostat for dielectric measurements

    International Nuclear Information System (INIS)

    The paper describes the design of a continuous-flow helium cryostat for the study of the dynamical behaviour of bound and free ionic charge carriers in the temperature range from 3.5 to 450 K. Samples up to 10 x 10 x 5 mm can be investigated. The background current amounts to 5 x 10-17 A or lower. For illustration the thermally stimulated depolarisation current (TSDC) spectrum of a Lasub(1-x)Basub(x)Fsub(3-x) (x=0.0126) single crystal obtained with this cryostat is presented. (author)

  7. Cycle design for the ISABELLE helium refrigerator

    International Nuclear Information System (INIS)

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

  8. Electron-helium scattering in Debye plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor [ARC Centre for Antimatter-Matter Studies, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia); Janev, R. K. [Macedonian Academy of Sciences and Arts, P.O. Box 428, 1000 Skopje (Macedonia, The Former Yugoslav Republic of)

    2011-11-15

    Electron-helium scattering in weakly coupled hot-dense (Debye) plasma has been investigated using the convergent close-coupling method. The Yukawa-type Debye-Hueckel potential has been used to describe plasma Coulomb screening effects. Benchmark results are presented for momentum transfer cross sections, excitation, ionization, and total cross sections for scattering from the ground and metastable states of helium. Calculations cover the entire energy range up to 1000 eV for the no screening case and various Debye lengths (5-100 a{sub 0}). We find that as the screening interaction increases, the excitation and total cross sections decrease, while the total ionization cross sections increase.

  9. The History and Morphology of Helium Reionization

    CERN Document Server

    Furlanetto, Steven

    2007-01-01

    A variety of observations now indicate that intergalactic helium was fully ionized by z~3. The most recent measurements of the high-redshift quasar luminosity function imply that these sources had produced ~2.5 ionizing photons per helium atom by that time, consistent with a picture in which the known quasar population drives HeII reionization. Here we describe the distribution of ionized and neutral helium gas during this era. Because the sources were rare and bright (with the photon budget dominated by quasars with luminosities L>L_\\star), random fluctuations in the quasar population determined the morphology of ionized gas when the global ionized fraction x_i was small, with the typical radius R_c of a HeIII bubble ~15-20 comoving Mpc. Only when x_i>0.5 did the large-scale clustering of the quasars drive the characteristic size of ionized regions above this value. Still later, when x_i>0.75, most ionizing photons were consumed by dense, recombining systems before they reached the edge of their source's ion...

  10. Laser spectroscopy of antiprotonic helium

    CERN Document Server

    Hori, M

    2005-01-01

    When antiprotons (i.e. the antimatter counterpart of protons) are stopped in helium gas, 97% of them annihilate within picoseconds by reacting with the helium nuclei; a 3% fraction, however, survive with an anomalously long lifetime of several microseconds. This longevity is due to the formation of antiprotonic helium, which is a three-body Rydberg atom composed of an antiproton, electron, and helium nucleus. The ASACUSA experimental collaboration has recently synthesized large numbers of these atoms using CERN's Antiproton Decelerator facility, and measured the atom's transition frequencies to 60 parts per billion by laser spectroscopy. By comparing the experimental results with recent three-body QED calculations and the known antiproton cyclotron frequency, we were able to show that the antiproton mass and charge are the same as the corresponding proton values to a precision of 10 parts per billion. Ongoing and future series of experiments will further improve the experimental precision by using chirp-compe...

  11. Microcellular Injection Molding Using Helium

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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 ?m 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

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

    International Nuclear Information System (INIS)

    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)

  14. Electron Conductivity on Helium Films

    OpenAIRE

    Klier, Ju?rgen; Doicescu, Irena; Leiderer, Paul; Shikin, Valeri

    2008-01-01

    Electrons on liquid helium films form a two-dimensional (2D) array with a wide range of electron density. This system is also very interesting for applications in restricted geometry. The conductivity ? of the electron arrays, however, strongly depends on the thickness d of the helium films adsorbed above solid substrates. This behaviour of ? is discussed in detail for a randomly rough substrate. It turns out that for the dependence of the conductivity ?(d) there exist three regions of hel...

  15. India's first indigenously developed helium liquefier

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  18. Studies of Spin-Liquid and Analog to Helium-4 Melting Curve in a 3D Frustrated Magnet: Gd3Ga5O12

    Science.gov (United States)

    Tsui, Y. K.

    2000-03-01

    Gadolinium gallium garnet, Gd_3Ga_5O_12 (GGG) has an extraordinary low temperature phase diagram [1,2]. Although the Curie-Weiss temperature of GGG is ~ -2 K, GGG shows no long range order down to T ~ 0.4 K. At low temperatures, GGG has a spin glass phase at low fields (AFM) state at fields of between 0.7 and 1.3 T, and, at intermediate fields, an apparent spin-liquid state without long range order. We have characterized the thermodynamic properties of the intermediate field (IF) state through heat capacity, thermal conductivity, and magnetocaloric measurements [3]. Our results show a sharp high-field phase boundary of the thermal irreversibility of the spin glass phase of GGG implying that the IF phase is distinct from the spin glass. The lower field boundary of the AFM phase is shown to have distinct minimum at T ~ 0.2 K, in analogy to the minimum in the melting curve of ^4He. The existence of such a minimum is confirmed by measurements of the latent heat of the transition below that temperature and is consistent with our heat capacity data. Currently we are measuring the dc magnetization (M) of GGG. Our preliminary data confirm the clear boundary between the spin glass and the IF states. M also shows indications of the reentrance of the IF phase. [1] P. Schiffer et al., Phys. Rev. Lett. 73, 2500 (1994). [2] P. Schiffer et al., Phys. Rev. Lett. 74, 2379 (1995). [3] Y.K. Tsui et al., Phys. Rev. Lett. 82, 3532 (1999).

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

    CERN Document Server

    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.

  20. Influence of the nitrogen helium mixture ratio on parameters of a self-sustained normal dc atmospheric pressure glow discharge

    Science.gov (United States)

    Arkhipenko, V. I.; Kirillov, A. A.; Simonchik, L. V.; Zgirouski, S. M.

    2005-11-01

    The influence of nitrogen additions to helium flow on the non-equilibrium plasma parameters and the discharge onset voltage of the self-sustained normal dc glow discharge at atmospheric pressure is studied. The concentrations of the low-excited helium atoms in states 21S, 21P, 23S and 23P are determined in glow discharge in helium (99.98%He) and in helium with a nitrogen admixture using the absorption spectroscopy technique. It is shown that the addition of a small amount of nitrogen into helium (less than 5%) leads to the increase of both interelectrode gap voltage and gas temperature. The drastic reduction of concentration of the low-excited helium atoms (n = 2) in the cathode region even at a nitrogen admixture of 0.5% occurs due to their quenching by the nitrogen excited species. At the same time, concentrations of higher excited helium atoms (n = 3) are essentially unchanged.

  1. The interaction potential of a symmetric helium trimer

    International Nuclear Information System (INIS)

    The interaction potential of three helium atoms in symmetric linear configurations is calculated under the Born--Oppenheimer approximation using an ''exact'' Green's function quantum Monte Carlo method. The results are compared with those of ''exact'' quantum Monte Carlo calculations for the helium dimer and the Axilrod--Teller triple-dipole energy expression. For nearest neighbor separations of 5.6 bohrs, the equilibrium distance for a helium dimer, the corresponding trimer energy is -21.5±1.9 K, compared to -22.3±0.2 K, calculated for pairwise additive behavior. For all internuclear separations in the neighborhood of the van der Waals well (?5.6 bohrs), the nonadditive contribution is found to be very small

  2. Thermal desorption of helium from graphite irradiated by He+ ions

    International Nuclear Information System (INIS)

    Thermal desorption of helium from graphite irradiated with 20 keV He+ ions and surface erosion caused by ion irradiation have been studied. After He+ ion irradiation, localized protrusions and uniform domed surface uplifting were observed on isotropic graphite irradiation doses of 5.0x1017 ions/cm2 and 5.0x1018 ions/cm2, respectively. The peak temperatures in thermal desorption curves have a tendency to rise with irradiation dose, and become constant at about 3300C for irradiation doses above 5.0x1017 ions/cm2. Thermal desorption of helium considerably depends on the structure of graphite samples studied here. Glassy carbon and graphitized paper (PAPYEX) retained only 22% and 12% of the helium retention of isotropic graphite, respectively. (orig.)

  3. Helium at elevated pressures: Quantum liquid with non-static shear rigidity

    Science.gov (United States)

    Bolmatov, D.; Brazhkin, V. V.; Trachenko, K.

    2013-03-01

    The properties of liquid helium have always been a fascinating subject to scientists. The phonon theory of liquids, taking into account liquid non-static shear rigidity, is employed here for studying internal energy and heat capacity of compressed liquid 4He. We demonstrate the good agreement of calculated and experimental heat capacity of liquid helium at elevated pressures and supercritical temperatures. Unexpectedly, helium remains a quantum liquid at elevated pressures for a wide range of temperature supporting both longitudinal and transverse-like phonon excitations. We have found that in the very wide pressure range of 5 MPa-500 MPa, liquid helium near melting temperature is both solid-like and quantum.

  4. Influence of simultaneous helium and hydrogen implantation on structure and properties of aluminium

    International Nuclear Information System (INIS)

    Structure and gas evolution in polycrystal aluminium simultaneously irradiated by 1 keV helium and hydrogen ions at 435 K are studied. Helium and hydrogen high content in the near-the-surface layers and intensive gas penetration into the bulk of the metal are detected. Kinetics of gas evolution from irradiated aluminium shows that helium and hydrogen remain captured up to high temperatures (0.5-0.6)Tsub(melt). Oversaturation of the matrix volume with helium and hydrogen results in gas pocket formation in the bulk and blisters on aluminium surface

  5. Thermal integration of processes to recover helium

    Energy Technology Data Exchange (ETDEWEB)

    Pahade, R.F.; Maloney, J.J.; Fisher, T.F. (Union Carbide Corp., Linde Div., Tonawanda, NY (US))

    1988-01-01

    New applications for helium have resulted in significant growth in helium demand in recent years. The primary source of helium in the USA is natural gas reservoirs. Typically natural gas reservoirs that contain helium also contain nitrogen. The presence of nitrogen requires that the heating value of the gas be upgraded using nitrogen rejection units (NRU). Thermal integration of the NRU process with the helium recovery process is described. Further integration of NRU and helium recovery process to produce cold helium gas suitable for use as a feed to a helium liquefier is also described. A key aspect of the integrated process is the use of refrigeration from the NRU to reduce power requirements, and capital cost for the helium recovery process.

  6. 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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

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

  8. Helium superfluidity. Shapes and vorticities of superfluid helium nanodroplets.

    Science.gov (United States)

    Gomez, Luis F; Ferguson, Ken R; Cryan, James P; Bacellar, Camila; Tanyag, Rico Mayro P; Jones, Curtis; Schorb, Sebastian; Anielski, Denis; Belkacem, Ali; Bernando, Charles; Boll, Rebecca; Bozek, John; Carron, Sebastian; Chen, Gang; Delmas, Tjark; Englert, Lars; Epp, Sascha W; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Hexemer, Alexander; Huth, Martin; Kwok, Justin; Leone, Stephen R; Ma, Jonathan H S; Maia, Filipe R N C; Malmerberg, Erik; Marchesini, Stefano; Neumark, Daniel M; Poon, Billy; Prell, James; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Seifrid, Martin; Siefermann, Katrin R; Sturm, Felix P; Swiggers, Michele; Ullrich, Joachim; Weise, Fabian; Zwart, Petrus; Bostedt, Christoph; Gessner, Oliver; Vilesov, Andrey F

    2014-08-22

    Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets. PMID:25146284

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-14

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

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

    International Nuclear Information System (INIS)

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

  11. Helium localization around the microscopic impurities embedded to liquid helium

    International Nuclear Information System (INIS)

    The structure and properties of the environment round the impurity atoms (Im) embedded in liquid helium are considered. It is shown that there are two qualitatively different types of structure of the He atom layer next to Im - attraction and repulsion structures. For the center attraction structure (strong Im-He interaction) the Im-He separation is longer than the equilibrium one for the pair Im-He potential, and the density and localization of He atoms are higher than in the bulk. It this case the He atom content in the layer, n, is almost independent of applied pressure. In the repulsion structure realized for alkaline metal atoms the Im-He separation is shorter than the equilibrium one and the density is lower than in the helium bulk. At T approx 1 K occupied are several states with different n and their energies differ only by approx 0.1 K, an increase in pressure resulting in a considerable reduction of n. The optical and EPR spectra of the atoms embedded to liquid and solid helium are interpreted on the basis of the analysis carried out. A simple model is proposed to evaluate the helium surroundings characteristics from the experimental pressure dependences of atomic line shifts in the absorption and emission spectra. The attraction structures in 3He - 4He mixtures are suggested to be highly enriched by 4He atoms which the repulsion structures - by 3He atoms. a possibility for existence of phase transitions in helium existence of phase transitions in helium shells surrounding impurity atoms is considered

  12. Analysis of flow instability of supercritical helium in curved tubing

    International Nuclear Information System (INIS)

    Flow instability of supercritical helium in curved stainless steel tubing is studied to obtain engineering data applicable to forced cooled superconducting magnets. The tubing is wound in a ten turn coil of 100 mm in radius, the length and inner diameter of the tubing are 3 m and 2.88 mm respectively. The supercritical helium studied is at a temperature from 5 to 11 K, the pressure is 0.5 to 1.2 MPa and the mass flow rate from 0.3 to 0.7 g/s. The results obtained from the experiments are: (1) Wall temperature along the cooling channel under pulsive thermal input is strongly dependent on flow velocity, heat flux, and heating time. (2) Inverse flow has been observed under heat flux high enough for the helium to reach the pseudo-critical line. (3) A linear relation between the energy per oscillation period and the helium pressure has been derived under a DC thermal input to flowing supercritical helium

  13. Long flexible transfer lines for gaseous and liquid helium

    International Nuclear Information System (INIS)

    Screened flexible four-fold coaxial transfer lines for gaseous and liquid helium with lengths of 5 to 50 m have been successfully built and tested. The lines for gaseous helium have to supply and return a mass flow of 5 to 10g s-1 at temperatures ranging between 350 and 20 K for cooldown or warmup of superconducting magnets. The lines for liquid helium have to supply up to 100 lh-1 for final cooldown or up to 25 lh-1 for normal operation of superconducting magnets. The hydrodynamic and thermal performance characteristics of the lines have been measured. The results are encouraging and the use of these lines for superconducting magnets in high energy accelerators can be envisaged. (author)

  14. Fast production of Bose-Einstein condensates of metastable Helium

    CERN Document Server

    Bouton, Q; Hoendervanger, A L; Nogrette, F; Aspect, A; Westbrook, C I; Clément, D

    2015-01-01

    We report on the Bose-Einstein condensation of metastable Helium-4 atoms using a hybrid approach, consisting of a magnetic quadrupole and a crossed optical dipole trap. In our setup we cross the phase transition with 2x10^6 atoms, and we obtain pure condensates of 5x10^5 atoms in the optical trap. This novel approach to cooling Helium-4 provides enhanced cycle stability, large optical access to the atoms and results in production of a condensate every 6 seconds - a factor 3 faster than the state-of-the-art. This speed-up will dramatically reduce the data acquisition time needed for the measurement of many particle correlations, made possible by the ability of metastable Helium to be detected individually.

  15. Evolution of helium rich stars with hydrogen burning

    International Nuclear Information System (INIS)

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

  16. Is the Sun helium-deficient

    International Nuclear Information System (INIS)

    The recent observations of solar 5-min oscillations of low degree agree approximately with the predictions of a standard solar model with normal abundances of helium and heavy elements. Much of the apparent discrepancy noticed when the observations were first announced was a result of having neglected the influence of the Sun's atmosphere in the normal mode analysis of the theoretical models. The standard solar models discussed here are not in perfect agreement with observation, but it seems that major modifications will not be necessary to remove the remaining small discrepancies. (author)

  17. Lamb shift in muonic helium ion

    CERN Document Server

    Martynenko, A P

    2006-01-01

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

  18. Cryogenic turbomachines for helium refrigeration system

    International Nuclear Information System (INIS)

    A helium refrigeration system is indispensable for large superconducting magnets used in large-scale particle accelerators, nuclear fusion reactors, superconducting generators, etc. Cryogenic turbomachines in the refrigeration system are key components upon deciding on reliability and performance. This paper describes its role in the system, construction, and performance of 3.5 K/80 K cold compressor, SHE circulation pump, and SHE turbine that have been developed by IHI. Each machine has superior characteristics that is perfectly oil-free and also has a unique heat insulation device, achieving a remarkable performance. Now IHI's cryogenic turbomachines hold a top position in the world for the field of cryogenic application. (author)

  19. Linde standard helium plant of medium capacity

    International Nuclear Information System (INIS)

    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.)

  20. Fermilab central helium liquefier operations

    International Nuclear Information System (INIS)

    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

  1. THE EFFECTS OF CURVATURE AND EXPANSION ON HELIUM DETONATIONS ON WHITE DWARF SURFACES

    International Nuclear Information System (INIS)

    Accreted helium layers on white dwarfs have been highlighted for many decades as a possible site for a detonation triggered by a thermonuclear runaway. In this paper, we find the minimum helium layer thickness that will sustain a steady laterally propagating detonation and show that it depends on the density and composition of the helium layer, specifically 12C and 16O. Detonations in these thin helium layers have speeds slower than the Chapman-Jouget (CJ) speed from complete helium burning, vCJ = 1.5 × 109 cm s–1. Though gravitationally unbound, the ashes still have unburned helium (?80% in the thinnest cases) and only reach up to heavy elements such as 40Ca, 44Ti, 48Cr, and 52Fe. It is rare for these thin shells to generate large amounts of 56Ni. We also find a new set of solutions that can propagate in even thinner helium layers when 16O is present at a minimum mass fraction of ?0.07. Driven by energy release from ? captures on 16O and subsequent elements, these slow detonations only create ashes up to 28Si in the outer detonated He shell. We close by discussing how the unbound helium burning ashes may create faint and fast 'Ia' supernovae as well as events with virtually no radioactivity, and speculate on how the slower helium detonation velocities impact the off-center ignition of a carbon detonation that could cause a Type Ia supernova in the double detonation scenario

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

    International Nuclear Information System (INIS)

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

  3. Direct current insulation breakdown characteristics of supercritical helium

    International Nuclear Information System (INIS)

    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 he 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.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-01

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

  5. Energy Levels of Helium Nucleus

    Directory of Open Access Journals (Sweden)

    Cvavb Chandra Raju

    2013-04-01

    Full Text Available The Helium-4 nucleus is more similar to the Hydrogen atom of atomic physics. In the case of hydrogen atom, there are many energy levels which were experimentally seen and theoretically explained using non-relativistic quantum mechanics. In this note, we use a central potential to derive the energy levels of Helium-4 nucleus. The ground state and the first few energy levels agree pretty well with experiment. The same potential can be used with nuclei like Oxygen-17 and many more nuclei.

  6. Helium migration in borogermanate glasses

    International Nuclear Information System (INIS)

    Helium permeation, diffusion, and solubility were measured in a series of B2O3--GeO2 glasses. All three parameters exhibit negative deviations from additivity at all compositions. Since intermediate glasses in this series also always have a lower free volume than would be predicted from additivity, it is postulated that the deviations observed in the helium mobility and solubility are primarily due to an increase in the compactness of the glass network. This conclusion is consistent with the results of several other recent studies of gas mobility in glass

  7. Helium retention properties of plasma facing materials

    Science.gov (United States)

    Yanagihara, H.; Yamauchi, Y.; Hino, T.; Hirohata, Y.; Yamashina, T.

    1997-02-01

    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) × 10 16He/ 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.

  8. Molecular helium on the surface of liquid helium

    International Nuclear Information System (INIS)

    Energetic electrons impinging on the surface of liquid helium produce a population of metastable helium molecules in the bulk liquid directly beneath and adjacent to the surface. This thesis describes a study of the transient behavior of these molecules as they interact with the liquid surface and the vapor. An experiment is presented in which a high-energy electron beam is directed at the liquid helium surface. The beam impact creates numerous by-products in the vapor and in the liquid. These consist of ions and electronically excited helium atoms and molecules. All of these with the exception of the metastable triplet molecule He2/sup */ = He2(a3?/sub u/+) relax almost immediately to the atomic ground state. Because of this, after the electron beam is turned off, one is left with a population of He2/sup */ in the liquid/vapor system. This is treated as three molecular systems with molecules populating the bulk liquid, the vapor, and the surface. A theoretical treatment of the behavior of these three systems and the interactions between them is presented. Coefficients for diffusion and bilinear (collisional) annihilation are calculated; also rates of evaporation, condensation, and tunneling of molecules through the liquid surface are estimated for comparison with the experimental data

  9. Fermilab Central Helium Liquefier system upgrade

    International Nuclear Information System (INIS)

    A significant upgrade to the Fermilab Central Helium Liquefier (CHL) facility's 4000 liters/hour helium system has been made to support the Laboratory's Tevatron superconducting accelerator. The upgrade includes a second helium liquefier with a rated capacity of 5400 liters/hour, a fourth reciprocating compressor rated at 750 grams/second, and an improved cryogenic distribution system including liquid helium dewars and pumps. The system design and operating experience to date are discussed

  10. Elastic scattering of metastable helium from helium, a molecular beam study of the helium excimer potentials

    International Nuclear Information System (INIS)

    The long range parts of the A 1?+sub(u) and C 1?+sub(g) helium excimer potentials have been studied in a crossed atomic beam experiment. The experimental details have been described earlier in detail. Helium atoms of a supersonic beam of variable kinetic energy (16 - 250 meV) and very good velocity resolution (1 to 8 %) is excited by coaxial electron impact to the two metastable states (1s2s, 21S and 23S). The singlet state can be quenched optically. This beam is crossed at a right angle with a beam of ground state He atoms, and the angular distribution of the excited helium (He*) atoms is measured. (Auth.)

  11. A helium atom measurement system using for the helium accumulation method in neutron dosimetry

    International Nuclear Information System (INIS)

    In the helium accumulation method for neutron dosimetry, it is applied that the number of helium atoms produced through (n,x?) reaction is proportional to neutron fluence in fast neutron irradiation fields. Besides, activities measuring in the activation method saturate to the value depending on their half-lives. A helium atom measurement system for detecting of helium atoms accumulated in neutron-irradiated samples has been constructed and tested. The samples are vaporized in a furnace to release helium contained in them. The number of helium atoms is measured with a quadrupole mass spectrometer calibrated by a standard helium gas supply which is consist of a known-volume vessel, a pressure gauge and a thermometer. It has been proposed in this work that helium-ion implanted aluminum disks are applied to calibrate the helium atom measurement system. This method has succeeded to obtain results agreed with the standard helium gas supply system. (author)

  12. Some aspects of the HERA helium refrigerator

    International Nuclear Information System (INIS)

    Large-scale helium refrigerators are needed for experimental setups in high energy physics and controlled nuclear fusion. They are used to cool superconducting magnets and cavities as well as panels for large-scale cryopumping. The refrigerators can take advantage of the same components as developed for the bulk helium liquefiers in connection with the separation of helium from natural gas

  13. Helium line detections from ELDWIM at 1.4 GHz

    CERN Document Server

    Baddi, Raju

    2012-01-01

    Helium line observations towards 11 Galactic positions using Westerbork Synthesis Radio Telescope(WSRT) have been reported. These observations were made towards nearby positions where already hydrogen lines were detected at sufficiently high intensity($\\geq$50mK) at 1.4 GHz. This approach gave a fair chance for the detection of helium line as well, keeping in mind the relative abundance(10%) of helium with respect to hydrogen. Care was also taken to avoid the presence of HII regions along the line of sight so that the line emission originates from the extended diffuse low density ionized component, ELDWIM of the Galaxy. The observations have resulted in the detection of helium line towards 5 positions out of 11 with signal to noise ratio(snr) $>$ 4$\\sigma$. An attempt has been made to associate detection/non-detection of helium line to the presence of surrounding HII regions. A weighting scheme that accounts for nearby($<$ 500pc) HII regions, their distances and other factors produces favourable results. I...

  14. Helium partial pressure measurement in a deuterium environment

    International Nuclear Information System (INIS)

    To study the removal of helium ash in present day, medium sized tokamaks, experiments with deuterium plasmas and helium puffs are conducted. Because D2 and He have almost the same mass, a spectroscopic method had been developed at TEXTOR where the He partial pressure in the exhaust line was measured by exciting the neutral gas in a Penning gauge and observing the characteristic emission lines of helium and deuterium. This method was limited to low pressures and concentrations because broad spectral lines from the deuterium molecules superimpose the He lines. By using a spectrometer and an intensified charge coupled device camera instead of optical filters and photomultipliers, it is now possible to record the interesting part of the spectrum with a time resolution of 20 ms. By subtracting the molecular spectrum of deuterium, helium concentrations from 2% on can be detected over about three orders of magnitude in pressure down to 2x10-6 mbar. He and D2 pressures are measured simultaneously. By another method the 58 nm resonance line of helium is observed and the crosstalk of the deuterium gas could be eliminated. Pressure measurements as low as 5x10-8 mbar and 1% He concentration are possible. A detection system utilizing a vacuum ultraviolet monochromator in combination with a channeltron has been tested. copyright 1996 American Institute of Physics

  15. On the size of ions solvated in helium clusters.

    Science.gov (United States)

    Ferreira da Silva, Filipe; Waldburger, Philipp; Jaksch, Stefan; Mauracher, Andreas; Denifl, Stephan; Echt, Olof; Märk, Tilmann D; Scheier, Paul

    2009-07-20

    Helium nanodroplets are doped with SF(6), C(4)F(8), CCl(4), C(6)H(5)Br, CH(3)I, and I(2). Upon interaction with free electrons a variety of positively and negatively charged cluster ions X(+/-)He(n) are observed where X(+/-) = F(+/-), Cl(+/-), Br(+/-), I(+), I(2) (+), or CH(3)I(+). The yield of these ions versus cluster size n drops at characteristic sizes n(s) that range from n(s) = 10.2+/-0.6 for F(+) to n(s) = 22.2+/-0.2 for Br(-). n(s) values for halide anions are about 70% larger than for the corresponding cations. The steps in the ion yield suggest closure of the first solvation shell. We propose a simple classical model to estimate ionic radii from n(s). Assuming the helium density in the first solvation shell equals the helium bulk density one finds that radii of halide anions in helium are nearly twice as large as in alkali halide crystals, indicating the formation of an anion bubble due to the repulsive forces that derive from the exchange interaction. In spite of the simplicity of our model, anion radii derived from it agree within approximately 10% with values derived from the mobility of halide anions in superfluid bulk helium, and with values computed by quantum Monte Carlo methods for X(-)He(n) cluster anions. PMID:19533729

  16. Temperature Bias and the Primordial Helium Abundance Determination

    OpenAIRE

    Peimbert, Antonio; Peimbert, Manuel; Luridiana, Valentina

    2001-01-01

    We study the effect that the temperature structure has on the determination of the primordial helium abundance, Yp. We provide an equation linking T(OIII), the temperature derived from the [OIII] lines, and T(HeII), the temperature of the He I lines, both for HII regions with O++ only and for HII regions where a fraction of O+ is present. By means of T(HeII), which is always smaller than T(OIII), we derive the helium abundances of 5 objects with low and very low metallicity ...

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

    CERN Document Server

    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 $M \\sim 5\\times10^3 GeV$.

  18. A design for a pinhole scanning helium microscope

    Science.gov (United States)

    Barr, M.; Fahy, A.; Jardine, A.; Ellis, J.; Ward, D.; MacLaren, D. A.; Allison, W.; Dastoor, P. C.

    2014-12-01

    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.

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

    International Nuclear Information System (INIS)

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

  20. A compact quadrupole ion filter for helium detection

    International Nuclear Information System (INIS)

    A compact quadrupole ion filter was conceived and constructed for optimum performance at the mass four region of the mass spectra. It was primarely designed for geological applications in the measurements of helium of soil-gases. The whole ion filter structure is 15 cm long by 3.5 cm diameter, including ion source and collecting plate. The sensitivity to helium is of the order of 10-2 A.torr-1 measured at a total pressure of 6x10-6 torr and resolution 6. The system can be easily adapted to work as a dynamic residual gas analyser for other purposes. (Author)

  1. Specific heat of solid helium

    Science.gov (United States)

    Lin, Xi; Clark, Anthony; Kim, Eunseong; Chan, Moses

    2006-03-01

    Recently superflow in solid ^4He was found below 200mK via a torsional oscillator technique^1. While there were a number of measurements on the specific heat of solid helium carried out down to 100mK, there is no evidence of a heat capacity signature related to the onset of the supersolid phase^2. A serious experimental challenge is discerning the small specific heat of solid helium from that of the metallic cells which are typically used to confine the solid. We have recently begun a new measurement of the heat capacity of solid helium contained in a silicon cell. The heat capacity of the silicon cell below 300mK is always less than that of the solid helium sample. Results of the measurement will be presented. This work is supported by NSF under grant number 0207071. [1] E. Kim and M. H. W. Chan, Nature 427, 225 (2004); E. Kim and M. H. W. Chan, Science 305, 1941 (2004); E. Kim and M. H. W. Chan, J. Low Temp. Phys. 138, 859 (2005). [2] S. H. Castles and E. D. Adams, J. Low Temp. Phys. 19, 397 (1975); B. H'ebral et al., Phonons in Condensed Matter, edited by H. J. Maris (Plenum, New York, 1980), pg. 169; A. C. Clark and M. H. W. Chan, J. Low Temp. Phys. 138, 853 (2005).

  2. Transferring superfluid helium in space

    International Nuclear Information System (INIS)

    A preliminary concept of a system for resupplying superfluid helium in space has been developed at NASA Ames Research Center. Such a system would greatly enhance several planned scientific missions. These include the Space Infrared Telescope Facility (SIRTF), Large Deployable Reflector (LDR), Gravity Probe-B (GP-B), Hubble Space Telescope (HST), and Advanced X-ray Astrophysics Facility (AXAF). Resupplying helium in orbit would extend the lifetime for each of these missions without the difficulties, delays, and costs associated with retrieving the system, resupplying on the ground, and relaunching. This is especially true of systems such as the LDR that are assembled in space. A simple thermodynamic model of a transfer system is presented and discussed. The different thermodynamic regimes that can be expected in the transfer line are also discussed. The relations between these regimes are used to evaluate the relative efficiencies of different transfer techniques that could be used with the transfer system. The efficient transfer of liquid helium requires a low heat leak into the transfer line, particularly at point sources such as the coupling. It is also shown that the proper selection of supply tank temperature is critical during helium resupply

  3. Liquid helium fluid dynamics studies

    International Nuclear Information System (INIS)

    The present report describes the work carried out under the sponsorship of the Division of High Energy Physics. The report is divided into sections according to the original grant proposal (hydrodynamic studies of single phase helium; two phase flow studies; component development studies; and new research areas). Following the text is a listing of publications which have resulted from work under the grant

  4. Effect of helium on tensile properties of vanadium alloys

    International Nuclear Information System (INIS)

    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 ?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 (?4%) during conventional irradiation at ?427 degrees C, showing that the heat is resistant to loss of work-hardening capability

  5. Characterizing uniform discharge in atmospheric helium by numerical modelling

    International Nuclear Information System (INIS)

    One-dimensional fluid model of dielectric barrier discharge (DBD) in helium at atmospheric pressure was established and the discharge was numerically simulated. It was found that not only the spatial distributions of the internal parameters such as the electric field, the electron density and ion density are similar to those in a low-pressure glow discharge, but also the visually apparent attribute (light emission) is exactly the same as the observable feature of a low-pressure glow discharge. This confirms that the uniform DBD in atmospheric helium is a glow type discharge. The fact that the thickness of the cathode fall layer is about 0.5 mm, much longer than that of a normal glow discharge in helium at atmospheric pressure, indicates the discharge being a sub-normal glow discharge close to normal one. The multipulse phenomenon was reproduced in the simulation and a much less complicated explanation for this phenomenon was given. (fluids, plasmas and electric discharges)

  6. Study of the Helium Enrichment in Globular Clusters

    CERN Document Server

    Valcarce, A A R

    2009-01-01

    Globular clusters (GCs) are spheroidal concentrations typically containing of the order of 10^5 to 10^6, predominantly old, stars. Historically, they have been considered as the closest counterparts of the idealized concept of "simple stellar populations." However, some recent observations suggest than, at least in some GCs, some stars are present that have been formed with material processed by a previous generation of stars. In this sense, it has also been suggested that such material might be enriched in helium, and that blue horizontal branch stars in some GCs should accordingly be the natural progeny of such helium-enhanced stars. In this contribution we show that, at least in the case of M3 (NGC 5272), the suggested level of helium enrichment is not supported by the available, high-precision observations.

  7. Helium refrigeration system for BNL colliding beam accelerator

    International Nuclear Information System (INIS)

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

  8. Precise measurement of helium isotopes in terrestrial gases

    International Nuclear Information System (INIS)

    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)

  9. Effect of helium on tensile properties of vanadium alloys

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

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

    International Nuclear Information System (INIS)

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

  11. Neutron studies of liquid and solid helium

    International Nuclear Information System (INIS)

    The progress made during 5/1/86--4/31/87 under contract No. F902- 34ER45082 is reported. The validity of the Impulse Approximation (IA) to the dynamic form factor, S(Q,?), has been investigated using realistic models of solid helium. The calculations suggest that the IA can be used to obtain the momentum distribution, n(p), within 1% at Q ? 30 Angstrom -1, if S(Q,?) is first symmetrized about the recoil frequency, ?R. For solid helium under pressure (e.g. 5 kbar) a Q approx-gt 50 Angstrom -1 is required. The S(Q,?) in liquid 3He and 4He in the wave vector transfer range 3 ? Q ? 10 Angstrom -1 has been evaluated, beginning from the pair potential. The general shape and width of S(Q,?) obtained agrees well with existing experiment. The width of S(Q,?) is found to oscillate as a function of Q in 4He but not in 3He. The dynamics of atoms adsorbed in solid layers on surfaces has been studied using self-consistent methods

  12. Free laminar convection of helium at supercritical state variables

    International Nuclear Information System (INIS)

    The results of investigation of free laminar convection of supercritical helium in a sufficiently wide temperature and pressure range at two forms of boundary conditions Tc=const and qsub(c)=const are presented. The results of heat transfer calculation are generalized by means of a compratively simple empirical equations. Systematic calculations under the boundary condition Tsub(c)=const have been performed for helium under pressures of 0.245, 0.294 and 0.587 MPa, Tsub(infinity)=4-12 K and ?T=Tsub(c)-Tsub(infinity)=0.1-16 K. The investigation for the case qsub(c)=const is carried out for helium at p=0.245 MPa, qsub(c)=5x102-5x103 W/m2, Tsub(infinity)=4-6 K. The generalized equation describes calculation data on heat transfer and helium with maximum error not exceeding 8.5%. The Tsub(c) calculation error does not exceed 15%. The recommended method is efficient, by labour input is equivalent to 4-5 iterations and possesses acceptable accuracy

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

    Directory of Open Access Journals (Sweden)

    D. Rucinski

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

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

  14. A crossed-beam time-of-flight study of metastable helium in collisions with helium, neon and argon

    International Nuclear Information System (INIS)

    Absolute velocity-resolved total integral cross sections have been measured for collisions of helium singlet (21S0) and triplet (23S1) metastable (He*) atoms with ground-state helium, neon, and argon atoms in the thermal velocity range of 1.0-3.5x105 cms-1. Additional measurements on the He*-Ne system with a large input aperture at the detector to suppress the sensitivity of the apparatus to elastic scattering failed to show the previously predicted sharply rising velocity structure in the inelastic excitation transfer cross sections. (author)

  15. Crossed-beam time-of-flight study of metastable helium in collisions with helium, neon, and argon

    International Nuclear Information System (INIS)

    Absolute total integral velocity-resolved cross sections have been measured for collisions of helium singlet (21S0) and triplet (23S1) metastables with ground-state helium, neon, and argon in the thermal velocity range of 1.0 to 3.5 x 105 cm/sec. Additional measurements on the He+-Ne system with a large input acceptance angle at the detector failed to show previously predicted sharply-rising velocity structure in the inelastic transfer cross sections. The measurements were taken with a crossed-beam time-of-flight apparatus

  16. Trapping and release of helium in tungsten

    OpenAIRE

    Lhuillier, Pierre-emile; Belhabib, Taieb; Desgardin, Pierre; Courtois, Blandine; Sauvage, Thierry; Barthe, Marie-france; Thomann, Anne-lise; Brault, Pascal; Tessier, Yves

    2011-01-01

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

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

    Science.gov (United States)

    Drachman, Richard J.

    2006-01-01

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

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

    Science.gov (United States)

    Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.

    2013-12-01

    Applicability of Henry's Law to helium solubility in olivine We have experimentally determined helium solubility in San Carlos olivine across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in olivine correlates linearly with PHe between 55 and 1680 bar. This linear relationship suggests Henry's Law is applicable to helium dissolution into olivine up to 1680 bar PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into olivine. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(×3.1)×10-12 mol g-1 bar-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2(× 2.3)×10-12 mol g-1 bar-1. Combining the presently determined helium Henry's coefficient for olivine with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within olivine that are not saturated by 1680 bar PHe or ~5×10-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos olivine to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 bar-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into olivine using an externally heated pressure vessel (Brown University). The starting materials were prepared by cutting gem-quality San Carlos olivine (~Fo90) into small blocks (~4×2×1 mm) using a diamond wafering blade saw and polishing with alumina slurries and colloidal silica. Analysis was completed by laser ablation-mass spectrometry using a 193 nm excimer laser and a MAP 215-50 specifically tuned for He (Open University, UK). Laser ablation pit depth varied from 2 to 40 ?m, and no correlation between pit depth and [He] is observed after accounting for variations PHe across the different experiments. This lack of correlation indicates a close approach to equilibrium was achieved over the experimental durations. Two analyses yielded spuriously high [He] (>3 std. dev. from the population mean, n = 85), and these analyses were not used to calculate Henry's coefficients. The two spuriously high analyses, in combination with the right skew of Henry's coefficients calculated from individual data points, suggests gem-quality San Carlos olivine contains volumes with anomalously high helium solubility. The nature of these volumes is currently under investigation. However, despite their presence, helium is still highly incompatible in olivine during partial melting. [1] Lux GCA 1987 [2] Heber et al. GCA 2007 [3] Shcheka & Keppler Nature 2012 [4] Walker et al. PEPI 2009

  19. HeREF-2003 : Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

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

  20. HeREF-2003: Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

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

  1. Diffusion and retention of helium in graphite and silicon carbide

    International Nuclear Information System (INIS)

    ?-particles of constant energies (5-28 MeV) and current densities from 0.8 to 40 x 1014 He/(m2s) were implanted to doses of typically 1017 m-2 at temperatures up to 1100 K into high purity pyrolytic graphite and silicon carbide. Helium release during and after implantation was monitored by mass spectrometry. Helium release from graphite during implantation strongly depends on specimen orientation and is highest for specimens implanted parallel to the basal plane. The corresponding diffusion coefficients are D[m2/s] = 5 x 10-5exp(- 1.17/kT) for 750 ? T [K] ? 1050. Helium release from SiC during implantation decreases strongly with increasing implantation depth. The diffusion coefficients are given by D [m2/s]=1.1 x 10-6exp(- 1.14/kT) for 800 ? T [K] ? 1050. In both materials a fraction of the implanted helium, which increases with increasing implantation depth and decreases with temperature, is retained and desorbs slowly. (orig.)

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

    International Nuclear Information System (INIS)

    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.)

  3. Anomalous effects of helium head pressure carbon dioxide in supercritical fluid chromatography and extraction.

    Science.gov (United States)

    Parcher, Jon F; Xiong, Yuan

    2003-01-31

    Helium head pressure carbon dioxide cylinders are commonly used to facilitate the delivery of liquid CO2 to supercritical fluid extraction and chromatographic pumps. It is usually tacitly assumed that the helium used to increase the delivery pressure of the CO2 cylinders is completely insoluble in liquid CO2 and thus remains isolated in the head space of the delivery cylinder. This assumption is invalid because up to 5 mol% helium can be entrained in the liquid CO2 delivered from helium head pressure cylinders. Significantly, contamination of liquid CO2 with even small amounts of helium can cause many unforeseen and usually deleterious effects in supercritical fluid chromatography and extraction schemes. The observed anomalies include decreased density of the fluid phase, irreproducible extraction and retention, ghost peaks, and even phase separation within the column or extraction vessel. PMID:12585330

  4. Helium behaviour in Fe-base materials: thermal desorption and nuclear reaction analyses

    International Nuclear Information System (INIS)

    Polycrystalline Fe 99.95 and 99.5 samples were implanted with helium at 8 keV and 3 MeV. Thermal Desorption Spectroscopy (TDS) and Nuclear Reaction Analysis (NRA) provided a complementary set of techniques to characterize helium-materials interactions within two different implantation depths, respectively close to the surface and in the bulk. Using TDS, it was possible to get information about the nature and the states of the structures where helium was trapped in radiation damaged Fe specimens. Activation energies for every trapping site (mono-vacancies, clusters) have been determined from conventional reaction model. The effect of interstitial carbon was also discussed, and compared with previous ab-initio studies. Moreover, the helium bulk diffusion constants in radiation damaged structures could be derived from non destructive 3He depth profiling. Preliminary observations highlighted that a few part of He remained trapped while helium bubbles migrated in the bulk. (authors)

  5. Commissioning result of the KSTAR helium refrigeration system

    International Nuclear Information System (INIS)

    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 thehe appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated

  6. Commissioning result of the KSTAR helium refrigeration system

    Energy Technology Data Exchange (ETDEWEB)

    Park, Dong Seong; Chang, Hyun Sik; Joo, Jae Joon [National Fusion Research Institute, Daejeon (Korea, Republic of)] (and others)

    2008-10-15

    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 (LN{sub 2}) 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.

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

    CERN Document Server

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

    2009-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Villard, B

    1999-07-15

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

  9. Mg impurity in helium droplets.

    Science.gov (United States)

    Navarro, J; Mateo, D; Barranco, M; Sarsa, A

    2012-02-01

    Within the diffusion Monte Carlo approach, we have determined the structure of isotopically pure and mixed helium droplets doped with one magnesium atom. For pure (4)He clusters, our results confirm those of Mella et al. [J. Chem. Phys. 123, 054328 (2005)] that the impurity experiences a transition from a surface to a bulk location as the number of helium atoms in the droplet increases. Contrarily, for pure (3)He clusters Mg resides in the bulk of the droplet due to the smaller surface tension of this isotope. Results for mixed droplets are presented. We have also obtained the absorption spectrum of Mg around the 3s3p?(1)P(1) ? 3s(2)?(1)S(0) transition. PMID:22320736

  10. Mg impurity in helium droplets

    CERN Document Server

    Navarro, J; Barranco, M; Sarsa, A

    2011-01-01

    Within the diffusion Monte Carlo approach, we have determined the structure of isotopically pure and mixed helium droplets doped with one magnesium atom. For pure 4He clusters, our results confirm those of M. Mella et al. [J. Chem. Phys. 123, 054328 (2005)] that the impurity experiences a transition from a surface to a bulk location as the number of helium atoms in the droplet increases. Contrarily, for pure 3He clusters Mg resides in the bulk of the droplet due to the smaller surface tension of this isotope. Results for mixed droplets are presented. We have also obtained the absorption spectrum of Mg around the 3s3p 1P_1 <-- 3s2 1S_0 transition.

  11. Helium atom scattering from surfaces

    CERN Document Server

    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.

  12. Instability of supercritical helium flow

    International Nuclear Information System (INIS)

    The instability of supercritical helium flow is investigated experimentally, Three types of instability are observed and their mechanisms are revealed. A type of instability is considered to be a Helmholtz one, caused by the acoustic resonance in the outlet pipe from the cryostat outlet to the flow control valve, The other two types are found to be the density wave instabilities caused by the density wave resonance, one in the entire system and another in the heated section. (author)

  13. Magnetically insulated helium ion diode

    International Nuclear Information System (INIS)

    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

  14. Detecting scintillations in liquid helium

    International Nuclear Information System (INIS)

    We review our work in developing a tetraphenyl butadiene (TPB)-based detection system for a measurement of the neutron lifetime using magnetically confined ultracold neutrons (UCN). As part of the development of the detection system for this experiment, we studied the scintillation properties of liquid helium itself, characterized the fluorescent efficiencies of different fluors, and built and tested three detector geometries. We provide an overview of the results from these studies as well as references for additional information

  15. Diffuse Helium Emission as a Precursory Sign of Volcanic Unrest

    Science.gov (United States)

    Padron, E.; Perez, N.; Hernandez Perez, P. A.; Sumino, H.; Melian Rodriguez, G.; Barrancos, J.; Nolasco, D.; Padilla, G.; Dionis, S.; Rodriguez, F.; Hernandez, I.; Calvo, D.; Peraza, M.; Nagao, K.

    2012-12-01

    Since July 16, 2011, an anomalous seismicity at El Hierro island, the youngest and smallest of the Canary Islands, was recorded by IGN seismic network. After the occurrence of more than 10,000 seismic events, volcanic tremor was recorded since 05:15 of the October 10, by all of the seismic stations on the island, with highest amplitudes recorded in the southernmost station. During the afternoon of October 12 a large light-green coloured area was observed in the sea to the souht of La Restinga village (at the southernmost part of El Hierro island), suggesting the existence of a submarine eruption. Since October 12, frequent episodes of, turbulent gas emission and foaming, and the appearance of steamy lava fragments has been observed on the sea surface. As part of the volcanic surveillance of the island, the Instituto Volcanologico de Canarias (INVOLCAN) geochemical monitoring program is carrying out diffuse helium surveys on the surface environment of El Hierro (soil atmosphere). This nobel gas has been investigated because it has been considered an almost ideal geochemical indicator because it is chemically inert, physically stable, nonbiogenic, sparingly soluble in water under ambient conditions and almost non-adsorbable. At each survey, 600 sampling sites covering the whole island and following an homogeneous distribution are selected for helium measurements in the soil gases, The helium concentration gradients with respect to its value on air (5.24 ppm) allow us to estimate a pure diffusive emission rate of helium throughout the island. The first survey was carried out on the summer of 2003, when the island was on a quiescence period. At this survey, the amount of helium released by the volcanic system of El Hierro was estimated in 6 kg/d. Since the beginning of the seismic unrest, 13 helium emission surveys have been carried out. The helium emission rate has shown an excellent agreement with the evolution of the volcanic crisis of the island, reaching 30 kg/d on November 6, several days before the occurrence of the submarine eruption. A significant decrease to 13 kg/d was estimated almost 10 days after the beginning of the eruption, followed by a sudden increase to 38 kg/d several days before the largest seismic event of the volcanic crisis (M = 4.6) occurred on November 11. High volcanic-gas pressure in a magma surrounded by a less deformed and fractured crust could be responsible for the high magmatic-helium emission rate and eventual submarine eruption during the first segment of activity, whereas the second segment causing extensive crustal deformation and fracturing resulted in a low gas pressure on the magma and relatively low magmatic-helium diffuse emission rates. The energy loss in the system from the release of volcanic gases might be responsible for the observed decrease in the seismic energy released and the absence of a second volcanic eruption. The system continued to degas for one month, producing a gradual decrease in the helium emission rate. Helium emission data shown in this report demonstrate that diffuse helium surveys is a powerful tool for volcano monitoring. The geochemical parameters presented here are extremely important for forecasting the onset of volcanic unrest and subsequent volcanic eruptions, mainly when magma migrates aseismically, i.e., silently, toward the surface.

  16. Trapping and release of helium in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Trapping and release of helium in tungsten

    International Nuclear Information System (INIS)

    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.

  18. The local interstellar helium density

    Science.gov (United States)

    Freeman, J.; Paresce, F.; Bowyer, S.; Lampton, M.; Stern, R.; Margon, B.

    1977-01-01

    During the Apollo-Soyuz Test Project, an extreme-ultraviolet telescope observed the region of the sky from which the interstellar medium approaches the sun. The instrument had a tin filter whose bandpass included the 584-A line of neutral helium. The observations set an upper bound for the number density of neutral helium in the local interstellar medium of 0.004 + or - 0.0022 per cu cm, which is significantly lower than previously reported. The stated error is dominated by the present uncertainty in the solar 584-A flux, which is taken to be approximately 200 million photons/sq cm per sec at earth's orbit. The result is not consistent with previous resonant-scattering Ly-alpha observations of interstellar hydrogen passing through the solar system, which generally yield a hydrogen number density of about 0.1 per cu cm, unless interstellar helium is locally depleted below its cosmic abundance. The result is consistent with cosmic abundances if the much lower average hydrogen densities inferred from recent column-density measurements to nearby hot stars are in fact representative of the immediate solar neighborhood.

  19. Vorticity matching in superfluid helium

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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)

  1. Radiolysis of cyclooctane with ?-rays and helium ions

    International Nuclear Information System (INIS)

    Iodine scavenging techniques have been used to examine the role of the cyclooctyl radical in the radiolysis of cyclooctane with ?-rays and with 5-20-MeV helium ions. In ?-radiolysis about 70% of the total yield of 6.6 cyclooctyl radicals/100 eV are scavenged with 10-4 M iodine, which agrees well with other studies on cycloalkanes that show most of the radicals produced in these systems react in the bulk medium at times longer than 1 ?s. However, it is found that 2.5 radicals/100 eV (38%) are produced by H atom precursors as compared to a value of 1.5 cyclohexyl radicals/100 eV (25%) in cyclohexane. With 10-MeV helium ions (average LET of 106 eV/nm), only 8% of the cyclooctyl radicals survive longer than a few microseconds due to the increased initial radical concentration in the helium ion track. The yield of the cross-bridged product bicyclo[3.3.0]octane (pentalane) was found to be independent of iodine concentration up to 0.03 M with both types of radiation. However, the pentalane yield found with 10-MeV helium ions was only one-third of that found in ?-radiolysis. The most likely reason for this result is the decreased yield of singlet-state formation due to the enhanced probability of cross combination reactions of electron-cation pairs in the high-density region of the helium ion track. 29 refs., 4 figs., 1 tab

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

    International Nuclear Information System (INIS)

    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)

  3. Influence of the nitrogen-helium mixture ratio on parameters of a self-sustained normal dc atmospheric pressure glow discharge

    International Nuclear Information System (INIS)

    The influence of nitrogen additions to helium flow on the non-equilibrium plasma parameters and the discharge onset voltage of the self-sustained normal dc glow discharge at atmospheric pressure is studied. The concentrations of the low-excited helium atoms in states 21S, 21P, 23S and 23P are determined in glow discharge in helium (99.98%He) and in helium with a nitrogen admixture using the absorption spectroscopy technique. It is shown that the addition of a small amount of nitrogen into helium (less than 5%) leads to the increase of both interelectrode gap voltage and gas temperature. The drastic reduction of concentration of the low-excited helium atoms (n 2) in the cathode region even at a nitrogen admixture of 0.5% occurs due to their quenching by the nitrogen excited species. At the same time, concentrations of higher excited helium atoms (n = 3) are essentially unchanged

  4. High voltage heavy current leads for liquid helium cryostats

    International Nuclear Information System (INIS)

    Properties of insulation for high voltage cryoelectric equipment are considered. The results of investigations into surface dielectric strength under cryogenic conditions of bushing models made of monolithic teflon are discussed. New designs for heavy current leads for liquid helium cryostats, based on the obtained results, have been suggested and built. The current leads were tested at 80 and 100 kV with 5.5 kA current and the results are presented. (author)

  5. Thermodynamic properties of hydrogen-helium plasmas.

    Science.gov (United States)

    Nelson, H. F.

    1972-01-01

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

  6. Helium damage in metal-tritium systems

    International Nuclear Information System (INIS)

    The time evolution of Debye-Scherrer lines was investigated in metal-tritium-helium systems by neutron-scattering techniques. Polycrystalline samples of TaTx, YTx, and ScTx were measured over a period of three years. The results show that helium damage is governed by the behavior of self-interstitial atoms and dislocation loops created by helium clustering and bubble formation. The self-interstitials and loops induce a lattice expansion in the early stages of helium formation. For higher helium concentrations the self-interstitials and loops produced are completely incorporated into an evolving dislocation network. In hexagonal rare-earth systems a preferential condensation of loops into a dislocation network lying in basal planes is observed. Additional small-angle-scattering experiments show that platelike helium cavities are formed in the hexagonal systems

  7. Ras Laffan helium recovery unit 2

    Science.gov (United States)

    Fauve, Eric Arnaud; Grabié, Veronique; Grillot, David; Delcayre, Franck; Deschildre, Cindy

    2012-06-01

    In May 2010, Air Liquide was awarded a contract for the Engineering Procurement and Construction (Turnkey EPC) for a second helium recovery unit [RLH II] dedicated to the Ras Laffan refinery in Qatar. This unit will come in addition to the one [RLH I] delivered and commissioned by Air Liquide in 2005. It will increase the helium production of Qatar from 10% to 28% of worldwide production. RLH I and RLH II use Air Liquide Advanced Technologies helium liquefiers. With a production of 8 tons of liquid helium per day, the RLH I liquefier is the world largest, but not for long. Thanks to the newly developed turbine TC7, Air Liquide was able to propose for RLH II a single liquefier able to produce over 20 tons per day of liquid helium without liquid nitrogen pre-cooling. This liquefier using 6 Air Liquide turbines (TC series) will set a new record in the world of helium liquefaction.

  8. Equilibrium models for luminous helium stars

    International Nuclear Information System (INIS)

    Equilibrium models for helium stars have been calculated in order to obtain mass-luminosity relations and to estimate the rate of the evolutionary change of the effective temperature. A luminous helium star is assumed to consist of a degenerate carbon-oxygen or oxygen-neon-magnesium core, a helium burning shell and a helium envelope. The envelope mass, which is obtained as the eigenvalue of the model for a given luminosity, is smaller for the larger core mass and for the higher effective temperature. The estimated rate of the evolutionary change of the effective temperature is found to be consistent with the observed period change of a pulsating R Coronae Borealis star, RY Sgr, if the core mass is greater than about 0.7 solar masses. A better constraint on the mass of the helium stars may be obtained if the period change of a hotter pulsating helium star is detected. (author)

  9. Electron capture into excited states of helium by helium-ion impact on helium

    International Nuclear Information System (INIS)

    Cross sections for electron capture into each excited state of He up to 4 1,3D by He+ impact on He in the energy range 100--10 000 keV have been calculated by means of the first Born approximation (Bates's version). A Gaussian technique previously developed for evaluating two-center integrals occurring in the Born amplitude has been used. One-parameter, variational wave functions are derived for each excited state of helium up to 4 1,3D. Some of the excited 1S cross sections are found to be affected by almost a factor of 2 by the choice of 1 1S helium wave function and orthogonality of the excited state 1S functions to this function. The observed departure of the ratio of triplet to singlet cross sections from the statistical weight of three is related partly to the interference between a one-electron process of capture into an excited state of helium and a two-electron process of capture into the ground state with the original He+ electron excited, and is related partly to the difference between the variational singlet and triplet excited one-electron wave functions. At energies of about 100 keV, agreement with available experimental results is generally good; however, for the 3 1P, 4 1P, and 4 1D states, the disagreement exceeds the estimated experimental uncertainty

  10. High-density metastable helium atoms produced by Penning-type discharges

    International Nuclear Information System (INIS)

    A high density of metastable helium atoms has been created using a Penning-type discharge. Experimental data indicate that the metastable density increases with the increase in the helium gas pressures in the range from 0.1 mTorr to 0.5 Torr. The highest metastable density of 3.5x1016 m-3 is observed at a steady-state gas pressure of 0.5 Torr. The relationships between the densities of the metastable helium atoms and the plasma discharge current are also obtained. Based on the results obtained using a spectral absorption technique and a theoretical collisional-radiative model, the data of the helium plasma spectroscopic emissions have been used in diagnosing plasma electron density and electron temperature. The results suggest the possibility of generating high-density metastable atoms with a high discharge current

  11. High-density metastable helium atoms produced by Penning-type discharges

    Energy Technology Data Exchange (ETDEWEB)

    Feng, P X [Physics Department, East China University, Shanghai 200051 (China); Andruczyk, D [School of Physics, University of Sydney, NSW 2006 (Australia); James, B W [School of Physics, University of Sydney, NSW 2006 (Australia); Takiyama, K [Graduate School of Engineering, Hiroshima University, Hiroshima 739-8527 (Japan); Namba, S [Graduate School of Engineering, Hiroshima University, Hiroshima 739-8527 (Japan); Oda, T [Faculty of Engineering, Hiroshima Kokusai Gakuin University, Hiroshima 739-0321 (Japan)

    2003-05-01

    A high density of metastable helium atoms has been created using a Penning-type discharge. Experimental data indicate that the metastable density increases with the increase in the helium gas pressures in the range from 0.1 mTorr to 0.5 Torr. The highest metastable density of 3.5x10{sup 16} m{sup -3} is observed at a steady-state gas pressure of 0.5 Torr. The relationships between the densities of the metastable helium atoms and the plasma discharge current are also obtained. Based on the results obtained using a spectral absorption technique and a theoretical collisional-radiative model, the data of the helium plasma spectroscopic emissions have been used in diagnosing plasma electron density and electron temperature. The results suggest the possibility of generating high-density metastable atoms with a high discharge current.

  12. High-density metastable helium atoms produced by Penning-type discharges

    Science.gov (United States)

    Feng, P. X.; Andruczyk, D.; James, B. W.; Takiyama, K.; Namba, S.; Oda, T.

    2003-05-01

    A high density of metastable helium atoms has been created using a Penning-type discharge. Experimental data indicate that the metastable density increases with the increase in the helium gas pressures in the range from 0.1 mTorr to 0.5 Torr. The highest metastable density of 3.5×1016 m-3 is observed at a steady-state gas pressure of 0.5 Torr. The relationships between the densities of the metastable helium atoms and the plasma discharge current are also obtained. Based on the results obtained using a spectral absorption technique and a theoretical collisional-radiative model, the data of the helium plasma spectroscopic emissions have been used in diagnosing plasma electron density and electron temperature. The results suggest the possibility of generating high-density metastable atoms with a high discharge current.

  13. Capture of slow antiprotons by helium atoms

    CERN Document Server

    Révai, J

    2005-01-01

    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 some cross sections show a rich low energy structure.

  14. Transparent Helium in Stripped Envelope Supernovae

    OpenAIRE

    Piro, Anthony L.; Morozova, Viktoriya S.

    2014-01-01

    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 sha...

  15. Helium cyclotron resonance within the earth's magnetosphere

    International Nuclear Information System (INIS)

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

  16. Helium isotopic abundance variation in nature

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Helium thermal desorption and retention properties of V-4Cr-4Ti alloy used for first wall of breeding blanket

    International Nuclear Information System (INIS)

    Helium irradiation experiments of V-4Cr-4Ti alloy with various surface treatments were conducted in an electron cyclotron resonance (ECR) ion irradiation apparatus. After helium ion irradiation at room temperature, the helium thermal desorption and retention properties were examined by thermal desorption spectroscopy (TDS). Ion energy of helium beam was 5 keV. Three groups of desorption peaks appeared at around 500, 850 and 1200 K in the TDS spectrum. After helium ion irradiation at ion fluence of 1 x 1021 He/m2, the retained helium desorbed mainly at around 1200 K and all of the implanted helium atoms were retained. With increasing fluence up to 5 x 1021 He/m2, the amount of helium desorbed at 500 K increased. For the polished samples with annealing at various temperatures, the desorption peak observed at around 500 K shifted to higher temperature region. Smallest retained amount of helium was observed in the V-alloy with polishing followed by annealing at 1373 K

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

    Science.gov (United States)

    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.

  19. Reduction of helium ash in fusion plasma by selective helium pumping

    International Nuclear Information System (INIS)

    The concept for reduction of helium ash concentration in a fusion plasma, based on the selective pumping for helium ions, is described. In a case that this scheme is employed together with the pumping of divertor, the helium ash concentration can be considerably reduced. Thus, this method is helpful to sustain the burning plasma state or the ignition condition. The pumping condition required for the selective helium pumping metal is also discussed. (author)

  20. Low evaporation helium cryostat with a refrigerator

    International Nuclear Information System (INIS)

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

  1. Cryogenic turbomachines for helium refrigeration system

    Energy Technology Data Exchange (ETDEWEB)

    Asakura, Hiroshi; Yoshinaga, Seiichiro; Ishizawa, Takehiko [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Saji, Nobuyoshi

    2000-09-01

    A helium refrigeration system is indispensable for large superconducting magnets used in large-scale particle accelerators, nuclear fusion reactors, superconducting generators, etc. Cryogenic turbomachines in the refrigeration system are key components upon deciding on reliability and performance. This paper describes its role in the system, construction, and performance of 3.5 K/80 K cold compressor, SHE circulation pump, and SHE turbine that have been developed by IHI. Each machine has superior characteristics that is perfectly oil-free and also has a unique heat insulation device, achieving a remarkable performance. Now IHI's cryogenic turbomachines hold a top position in the world for the field of cryogenic application. (author)

  2. Pulsation of high luminosity helium stars

    International Nuclear Information System (INIS)

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

  3. Nonanalytic hydrodynamic dispersion relations in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, T.R.

    1984-04-01

    Hydrodynamic dispersion relations in superfluid helium II are calculated by means of mode-coupling theory. It is shown that the six hydrodynamic frequencies depend on the wave number k, for small k, as z/sub ..cap alpha../(k) = minus-or-plusic/sub ..cap alpha../k-a/sub ..cap alpha../k/sup 2/-b/sub ..cap alpha../k /sup 5/2/, where ..cap alpha.. denotes the particular hydrodynamic mode. Furthermore, the complex number b/sub ..cap alpha../ is explicitly calculated, and it is shown that the effective k-dependent speed of first sound exhibits anomalous dispersion. The experimental consequences of this are also discussed.

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

    International Nuclear Information System (INIS)

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

  5. Helium distribution system for the Large Coil Test Facility (LCTF)

    International Nuclear Information System (INIS)

    The helium distribution system of the Large Coil Test Facility is designed to establish and maintain the thermal environment of the toroidal array of superconducting magnets throughout the initial test and evaluation period of the test program. The refrigeration and liquefaction requirements for the LCTF will be discussed including both the usual cooldown, lead cooling, thermal conduction and radiation and joule heating losses, and the unusual losses due to simulated nuclear heating, magnetic coupling losses due to the transient fields of the driving magnets, and pumping losses due to fluid resistance and pump inefficiency. The flow system is designed with separate cooldown and steady-state flow systems, and to simultaneously circulate helium understeady-state conditions through coils cooled by boiling liquid or supercritical helium at approximately 4.0 K and >2.5-atm pressure. Separate helium storage dewars are utilized for vapor cooling of the current leads to the magnets with the effluent gas being stored after compression in high pressure storage tanks. The flow diagram will be presented in simplified form to show the salient features of the cryogenic system

  6. A liquid helium cryogenic system design for the GEM magnet

    International Nuclear Information System (INIS)

    The Superconducting Super Collider (SSC) Gammas, Electrons, Muons (GEM) magnet is a large superconducting solenoid with a total mass of 1.05 x 106 kg and a stored energy of 2.5 GJ. A cryogenic system to cool and to maintain the GEM magnet to liquid helium temperature is described. The system is designed to operate effectively under a variety of operating conditions, including cooldown/warm-up, steady state operations, and quench. Primary cooling during steady-state operation is based on natural circulation thermosiphon flow through cooling tubes in the solenoid support bobbin. Additional cooling loops are included for lead and joint cooling and conductor stabilization. A helium refrigerator/liquefier rated at 2 kW and 20 g/s will be specified to meet the refrigeration requirements. Cooldown of the magnet from 300 K to liquid nitrogen temperatures is accomplished using a counterflow helium-to-liquid-nitrogen heat exchanger independent of the helium refrigerator. The system incorporates provisions for maintenance access during accelerator beam operation

  7. A precision measurement of the hyperfine structure of antiprotonic helium

    International Nuclear Information System (INIS)

    Full text: Antiprotonic helium (pHe) is a neutral three body system consisting of one electron, one helium nucleus, and one antiproton (He++ e- + p). When an antiproton approaches a helium atom, at an energy of the order of the helium ionization energy, it can, simultaneously, eject one of the two ground state electrons and become captured. 97 % of the captured antiprotons annihilate within nanoseconds with one of the nucleons in the nucleus but 3 % occupy metastable states with lifetimes of the order of ? 3 %. Due to its long life time this unique particle provides an ideal subject to test three-body Quantum Electrodynamic (QED) calculations. A hyperfine structure (HFS) is caused by the coupling of the electron spin with the antiproton orbital angular momentum. This HFS can be measured using a laser-microwave- laser resonance technique, where a population asymmetry is induced through laser depopulation of one of the HF substates. A population transfer between the substates is induced with a microwave resonant pulse. Then a second laser is used to measure the transferred population. A comparison between the measured transition frequencies and three-body QED calculations can be used to determine the spin magnetic moment of the antiproton. Such a matter anti-matter comparison yields a test of CPT invariance. Over the last couple of years a factor of 5 improvement to the precision has been achieved. This talk shall describe the experiment and prelk shall describe the experiment and preliminary experimental data from the 2008 beam time. (author)

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

    International Nuclear Information System (INIS)

    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

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

    CERN Document Server

    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...

  10. Helium bubble bursting in tungsten

    International Nuclear Information System (INIS)

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

  11. 21 CFR 868.1640 - Helium gas analyzer.

    Science.gov (United States)

    2010-04-01

    ...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 gas mixture during pulmonary function...

  12. Evaluation of enhanced frame-dragging in the vicinity of a rotating niobium superconductor, liquid helium and a helium superfluid

    Science.gov (United States)

    Tajmar, M.

    2011-12-01

    To explain a reported Cooper-pair mass anomaly in niobium it has been predicted that rotating superconductors or superfluids might produce large non-classical frame-dragging fields. Anomalous gyroscope signals close to the measurement resolution in the proximity of rotating superconductors or liquid helium have also been reported while trying to investigate this theoretical concept. Based on lessons from various setups, we succeeded in building an experimental facility that allowed us to rotate a niobium superconductor, liquid helium, superfluid helium and low temperature matter with high accelerations at high speed exceeding all previous efforts. A military-grade SRS-1000 gyroscope at close proximity in different locations was used to measure any anomalous frame-dragging-like fields. No such anomalies were found within three times the noise level of our setup (± 5 × 10 - 8 rad s - 1). Measurements with an electric motor at speeds up to 5000 rpm enabled us to set low boundaries for any coupling or frame-dragging-like effect outside of a rotating niobium superconductor or liquid helium to 4 × 10 - 11 and for superfluids to 3 × 10 - 10. Due to the high speeds used, these results are up to two orders of magnitude below any previous result.

  13. Evaluation of enhanced frame-dragging in the vicinity of a rotating niobium superconductor, liquid helium and a helium superfluid

    International Nuclear Information System (INIS)

    To explain a reported Cooper-pair mass anomaly in niobium it has been predicted that rotating superconductors or superfluids might produce large non-classical frame-dragging fields. Anomalous gyroscope signals close to the measurement resolution in the proximity of rotating superconductors or liquid helium have also been reported while trying to investigate this theoretical concept. Based on lessons from various setups, we succeeded in building an experimental facility that allowed us to rotate a niobium superconductor, liquid helium, superfluid helium and low temperature matter with high accelerations at high speed exceeding all previous efforts. A military-grade SRS-1000 gyroscope at close proximity in different locations was used to measure any anomalous frame-dragging-like fields. No such anomalies were found within three times the noise level of our setup (± 5 × 10?8 rad s?1). Measurements with an electric motor at speeds up to 5000 rpm enabled us to set low boundaries for any coupling or frame-dragging-like effect outside of a rotating niobium superconductor or liquid helium to 4 × 10?11 and for superfluids to 3 × 10?10. Due to the high speeds used, these results are up to two orders of magnitude below any previous result.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-10-01

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

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

    Science.gov (United States)

    Chen, J.; Jung, P.; Rebac, T.; Duval, F.; Sauvage, T.; de Carlan, Y.; Barthe, M. F.

    2014-10-01

    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.

  16. Creep rupture strengths of several nickel-base superalloys in impure helium

    International Nuclear Information System (INIS)

    In order to estimate long-term creep rupture strengths of candidate alloys for the intermediate heat exchanger of very high temperature gas cooled reactors, creep rupture tests in impure helium have been conducted for three newly developed nickel-base alloys as well as for Inconnel 617. The results are discussed in comparison with those in air. The 16%Cr-20%W-30%Co-Ni alloy and the 23%Cr-18%W-Ni alloy, both solid solution strengthened type, indicate almost the same short-term creep rupture strengths in helium as those in air. Long-term creep rupture strengths of these alloys in helium, however, seem to be higher than those in air because crack growth is caused only by mechanical stress in helium, whereas it is accelerated by oxidation following nitriding in air. Inconel 617 indicates significantly lower creep rupture strength in helium than that in air. One of the causes is the difference in the crack growth mechanism but there must be a more significant cause which remains unknown at present. The precipitation hardened 18%Cr-4%Mo-6%W-10%Co-2%Al-2.5%Ti-Ni alloy gives a slightly lower short-term creep rupture strength in helium than that in air, but the long-term creep rupture strength in helium seems to be higher than that in air. (auth.)

  17. Properties of vanadium-base alloys irradiated in the dynamic helium charging experiment

    International Nuclear Information System (INIS)

    One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of ? 0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18--31 dpa at 425--600 C in Li-filled capsules in a sodium-cooled fast reactor. This paper presents results of postirradiation examination and tests of microstructure and mechanical properties of V-5Ti, V-3Ti-1Si, V-8Cr-6Ti, and V-4Cr-4Ti (the latter alloy has been identified as the most promising candidate vanadium alloy). Effects of helium on tensile strength and ductility were insignificant after irradiation and testing at > 420 C. However, postirradiation ductilities at -150 C in DHCE specimens. Predominantly brittle-cleavage fracture morphologies were observed only at -196 C in some specimens that were irradiated to 31 dpa at 425 C during the DHCE. For the helium generation rates in this experiment (? 0.4--4.2 appm He/dpa), grain-boundary coalescence of helium microcavities was negligible and intergranular fracture was not observed

  18. The Effects of Curvature and Expansion on Helium Detonations on White Dwarf Surfaces

    CERN Document Server

    Moore, Kevin; Bildsten, Lars

    2013-01-01

    Accreted helium layers on white dwarfs have been highlighted for many decades as a possible site for a detonation triggered by a thermonuclear runaway. In this paper, we find the minimum helium layer thickness that will sustain a steady laterally propagating detonation and show that it depends on the density and composition of the helium layer, specifically C12 and O16. Detonations in these thin helium layers have speeds slower than the Chapman-Jouget (CJ) speed from complete helium burning, v_cj=1.5e9 cm/s. Though gravitationally unbound, the ashes still have unburned helium (~ 80% in the thinnest cases) and only reach up to heavy elements such as Ca40, Ti44, Cr48, and Fe52. It is rare for these thin shells to generate large amounts of Ni56. We also find a new set of solutions that can propagate in even thinner helium layers when O16 is present at a minimum mass fraction of ~0.07. Driven by energy release from alpha captures on O16 and subsequent elements, these slow detonations only create ashes up to Si28 ...

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

    International Nuclear Information System (INIS)

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

  20. Helium irradiation effects in single crystals of MgAl2O4

    International Nuclear Information System (INIS)

    Magnesium aluminate spinel, (MgAl2O4), is a promising material as a uranium free matrix for the transmutation of americium. Fission products and ?-particles are produced during the transmutation. The impact of ?-particles is simulated by 30 keV 3He ion implantations at room temperature (RT) with the doses 6.2, 16, 20 and 53x1015 cm-2. In another set of experiments a single crystal MgAl2O4 (1 0 0) sample is irradiated with ?-particles (4.5 MeV) from a 241Am source at RT to a dose of 1.3x1012 cm-2. Helium release from the implanted samples was studied by thermal desorption spectrometry (TDS). The numerical analysis of the experimental thermal desorption results of ?-implanted samples to a very low helium concentration (0.0288 appm in the irradiation zone of 12.4 ?m) show that helium release is dominated by helium interstitial diffusion with an activation energy of 1.8 eV. In the case of high dose implantation to 1.74 at.% in the implantation zone approximately of 100 nm, helium is released from He-vacancy clusters with the activation energy of 2.35 eV. The evolution of the helium concentration profile in the temperature range from RT to 1483 K is monitored by neutron depth profiling (NDP). It confirms that the release of helium is governed by dissociation from vacancy clusters

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

    International Nuclear Information System (INIS)

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

  2. Simultaneous irradiation effects of hydrogen and helium ions on tungsten

    International Nuclear Information System (INIS)

    Full text of publication follows: Helium is an intrinsic impurity in fusion plasmas produced by the fusion reaction between deuteron and triton. However, its effects on hydrogen isotope behavior such as retention and permeation in armor materials have not been studied in detail. In this paper, we present the results on tungsten blistering by hydrogen, helium and carbon mixed ion beam irradiation, for the first time. Since tungsten blistering is resulted from hydrogen diffusion over the ion range and trapping in tungsten, this result gave important information on helium effects on hydrogen isotope behavior. Samples used for this study is sintered and hot-rolled tungsten plates (purity of 99.99%) with the thickness of 1 mm. Surface was mirror polished to the roughness of ?0.01 ?m. Ion irradiation was done by an ion beam device HiFIT, which has a capability to control small amount of impurities such as helium and carbon with the resolution of about 0.1%. Ion energy was 1 keV with the main hydrogen molecular ion component of H3+ (?60%). Hydrogen flux was ?2 x 1020 m-2 s-1, which almost matched the ion flux to first walls. Carbon was always included with the concentration of about 0.8%. Carbon ion irradiation resulted in W and C mixed layer, which made surface conditions for all samples similar. It was found that small amount of He significantly affected blister formation of tungsten. Hydrogen and carbon mixed ingsten. Hydrogen and carbon mixed ion irradiation to the fluence of 7.5 x 1024 m-2 at 453 K, 653 K, and 753 K all resulted in blistering. However, only 0.1% of He in the ion beam can reduce the number of blisters. Especially in the higher temperature cases (653 K and 753 K), blister formation was completely suppressed. We also made the reduced flux experiments without helium in 0.7 x 1020 m-2 s-1 (about 1/3 of the above condition, irradiation fluence was also reduced to about 1/3), which also caused blistering. Therefore, the addition of 0.1% helium reduced effective hydrogen flux into the bulk by more than a factor of three. The helium bubble formation could result in reduction of effective diffusion of hydrogen into the bulk. (authors)

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

    International Nuclear Information System (INIS)

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

  4. Bichromatic Slowing of Metastable Helium

    CERN Document Server

    Chieda, M A

    2012-01-01

    We examine two approaches for significantly extending the velocity range of the optical bichromatic force (BCF), to make it useful for laser deceleration of atomic and molecular beams. First, we present experimental results and calculations for BCF deceleration of metastable helium using very large BCF detunings, and discuss the limitations of this approach. We consider in detail the constraints, both inherent and practical, that set the usable upper limit of the BCF. We then show that a more promising approach is to utilize a BCF profile with a relatively small velocity range in conjunction with chirped Doppler shifts, to keep the force resonant with the atoms as they are slowed. In an initial experimental test of this chirped BCF method, helium atoms are slowed by $\\sim 370$ m/s using a BCF profile with a velocity width of $\\lesssim 125$ m/s. Straightforward scaling of the present results indicates that a decelerator for He* capable of loading a magneto-optical trap (MOT) can yield a brightness comparable t...

  5. Helium-heated steam reformer

    International Nuclear Information System (INIS)

    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

  6. Free convection heat transfer to supercritical helium

    International Nuclear Information System (INIS)

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

  7. Nuclear fusion and the helium supply problem

    International Nuclear Information System (INIS)

    Highlights: ? Fusion power plants will require helium as cryogenic medium and as coolant. ? High losses are expected: for a power plant like DEMO ? 2 t p.a. ? The same power plant is expected to produce only ?0.6 t p.a. ? Global helium resources are finite: fusion will therefore exacerbate an already difficult situation. ? The “back-stop” technology will be the extraction helium of helium from the atmosphere. -- Abstract: The natural resources required for the operation of fusion power plants are – with the possible exception of the neutron multiplier beryllium – readily available. On the other hand, the supply of helium, which is required as cryogenic medium and coolant, may be a problem due to losses during operation and decommissioning. Helium is a rare element obtained as a by-product in the extraction of natural gas. The danger exists that the natural gas will be used up without the helium being conserved. We estimate the helium demand for a global 30% base-load contribution of fusion to electricity supply and also calculate the amount produced by the power plants themselves

  8. Power for the Fermilab Tevatron helium liquefier

    International Nuclear Information System (INIS)

    A description is given of the electrical power installation for the central helium liquefaction plant at Fermilab. The system includes three 4000 horsepower motors for the helium and nitrogen compressors, complete with the necessary motor starting and auxiliary equipment. Details are given also on the associated interlocking and monitoring equipment

  9. Post-giant evolution of helium stars

    International Nuclear Information System (INIS)

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

  10. Helium impurity interactions in vanadium and niobium

    International Nuclear Information System (INIS)

    Thermal helium desorption spectrometry (THDS) has been employed to study the nucleation and growth of helium defect agglomerates in niobium and vanadium. An important difference from other body-centered-cubic metals was the temperature at which helium was released from monovacancy type defects. In Mo and W the release takes place at 0.40Tm (Tm=melting temperature) but in V and Nb at 0.25Tm. This and other observations led to the conclusion that in nearly all interactions of helium with radiation-induced defects, impurities, mainly oxygen, are involved. Impurity levels of 20-30 appm are sufficient to completely suppress the type of helium behaviour that was found in Mo and W. Oxygen decorates the helium-vacancy complexes and makes the helium desorption temperature lower, but stabilizes the small defect complexes up to a temperature of about 700 K; beyond this temperature, nucleation of defect clusters is considerably reduced. Oxygen decoration has been observed to reduce the sink strength of the defects for helium trapping. ((orig.))

  11. ACOUSTIC SIGNATURES OF THE HELIUM CORE FLASH

    International Nuclear Information System (INIS)

    All evolved stars with masses M ?? undergo an initiating off-center helium core flash in their Mc ? 0.48 M? He core as they ascend the red giant branch (RGB). This off-center flash is the first of a few successive helium shell subflashes that remove the core electron degeneracy over 2 Myr, converting the object into a He-burning star. Though characterized by Thomas over 40 years ago, this core flash phase has yet to be observationally probed. Using the Modules for Experiments in Stellar Astrophysics (MESA) code, we show that red giant asteroseismology enabled by space-based photometry (i.e., Kepler and CoRoT) can probe these stars during the flash. The rapid (?5 yr) contraction of the red giant envelope after the initiating flash dramatically improves the coupling of the p-modes to the core g-modes, making the detection of l = 1 mixed modes possible for these 2 Myr. This duration implies that 1 in 35 stars near the red clump in the H-R diagram will be in their core flash phase. During this time, the star has a g-mode period spacing of ?Pg ? 70-100 s, lower than the ?Pg ? 250 s of He-burning stars in the red clump, but higher than the RGB stars at the same luminosity. This places them in an underpopulated part of the large frequency spacing (??) versus ?Pg diagram that should ease their identification among the thousands of observed red giants..

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

    CERN Document Server

    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.

  13. Isotopic-chromatographic-spectral determination of carbon dioxide in helium using adsorption preconcentration

    International Nuclear Information System (INIS)

    A combined chromatographic-spectro-isotopic method has been developed for determination of CO2 in helium using absorption accumulation and chromatography at low pressure. Down to 5x10-6 mole % CO2 can be determined. The method does not require reference samples based on test gases. The possibility to determine lower CO2 contents is connected with a better reliability of spectroscopic determination of CO2 isotopic composition and with an increase of a helium sample to be analysed

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

    OpenAIRE

    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...

  15. Study of blisters formed due to helium ion bombardment on stainless steel

    International Nuclear Information System (INIS)

    Sheets of stainless steel were bombarded by helium ions using 2 MeV 4He+ ion beam in a Van-de-Graaff machine. Dose of irradiation varied between 1.0x1018 and 5.6x1018 ions/cm2. Helium gas blisters and exfoliations thus formed were examined by scanning electron microscope. The results of annealing studies on these blisters and exfoliations are reported. (auth.)

  16. Collisional radiative model of a helium capillary glow discharge including atomic collisions

    OpenAIRE

    Gousset, G.; Boulmer-leborgne, C.

    1984-01-01

    A new collisional radiative model of helium capillary glow discharge has been developed that incorporates the l changing atomic collisions, the associative ionization and the n changing atomic collisions (for the states n ? 8). This model is used to determine the electron temperature of low density plasmas. The range of validity of the model is 0.3 ? PHe (torr) ? 5 for the helium pressure, 109 ? ne (cm -3) ? 2 × 101^3 for the electron density, 1 ? ? (mm) ? 16 for the discharg...

  17. Effect of temperature on the pressure dependence of helium solubility in vitreous silica

    International Nuclear Information System (INIS)

    Helium solubility in vitreous silica was measured from 100 to 1350 atm at 5, 25, 50, and 80 0C. The results can be described by the Langmuir adsorption isotherm at each temperature. The temperature dependence of the high-pressure helium solubility in this gas-glass system can be described either by the van't Hoff equation or by a statistical thermodynamical model

  18. The proton and helium rigidity spectra from 10 to 50 GV

    International Nuclear Information System (INIS)

    A magnet spectrometer flown from Palestine, Texas (September 15, 1976) has produced measurements on 1.5x105 protons and 2x104 helium nuclei covering the rigidity range 10-50 GV. In this interval, the proton spectrum has been fitted to a power law with a spectral index of 2.51 +- 0.03. Similarly, the helium nuclei rigidity spectrum can be represented as a power law with an index of 2.61 +- 0.03. (author)

  19. Adsorption and desorption of helium in aerogels

    International Nuclear Information System (INIS)

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

  20. Impurity condensation in liquid and solid helium

    Science.gov (United States)

    Gordon, E. B.

    2004-10-01

    It is shown from an analysis of x-ray structural and IR spectroscopic studies that when impurity particles are introduced into liquid or solid helium, the clusters formed in the cold part of a gas jet have a pronounced spatial separation of impurities with different volatility. In particular, in the condensation of partially dissociated diatomic molecules the atoms are highly concentrated near and on the surface of the clusters. Segregation of this kind is preserved in the condensate in liquid helium, which consists of clusters stuck together into a porous structure; in solid helium clusters are isolated. The presence of high concentrations of atoms in the surface layer at the boundary with condensed helium explains the specifics of condensate behavior observed by methods of optical spectroscopy, ESR, and thermometry. An experimental strategy is developed for detecting the formation of an impurity-helium solid.

  1. Improvement of helium sampling system in HTTR

    International Nuclear Information System (INIS)

    Graphite structures are used as the HTTR core internals. Graphite structures have high heat resistant property but strength degrades easily by oxidization. To prevent the oxidization of graphite structures, impurity concentrations in the helium coolant are controlled strictly. The helium sampling system is installed to measure the impurity concentrations in the helium coolant. Seal-oil leakage occurred at the rod seal mechanism of gas compressor in helium sampling system. The reasons are degradation of the seal material and contaminant abrasion powder of the grand-packing. Thus, the material of the seal material was changed and contaminant was decreased. A long term operation became possible by these countermeasures. Moreover, reliable data can be obtained and efficient impurity control is enabled due to renewal of data acquisition control computer of gas chromatograph mass spectrometer and improvement of liquid nitrogen trap. This report describes the improvement items of the helium sampling system. (author)

  2. Spectrographic detection of nitrogen impurity in helium

    International Nuclear Information System (INIS)

    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. Cryogenic helium 2 systems for space applications

    Science.gov (United States)

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

    1978-01-01

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

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

    Science.gov (United States)

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

    2007-01-01

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

  5. Ground State Hyperfine Structure of Muonic Helium Atom

    CERN Document Server

    Krutov, A A

    2007-01-01

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

  6. Natural convection in helium turbulent flow under supercritical conditions

    International Nuclear Information System (INIS)

    Results of calculation of natural convection in helium turbulent flow conducted by finite-differential methods are presented. Calculation and experimental data on heat-transfer coefficient were correlated. Calculations were conducted for 0.245-0.587 MPa pressure, 4.49-8.4 K temperature, 102-5x103 W/m heat fluxes and 109-2x1013 Reley number. Correlation showed good agreement of calculation and experimental data

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

    International Nuclear Information System (INIS)

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

  8. THE EFFECTS OF CURVATURE AND EXPANSION ON HELIUM DETONATIONS ON WHITE DWARF SURFACES

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Kevin; Bildsten, Lars [Department of Physics, University of California, Santa Barbara, CA (United States); Townsley, Dean M. [Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL (United States)

    2013-10-20

    Accreted helium layers on white dwarfs have been highlighted for many decades as a possible site for a detonation triggered by a thermonuclear runaway. In this paper, we find the minimum helium layer thickness that will sustain a steady laterally propagating detonation and show that it depends on the density and composition of the helium layer, specifically {sup 12}C and {sup 16}O. Detonations in these thin helium layers have speeds slower than the Chapman-Jouget (CJ) speed from complete helium burning, v{sub CJ} = 1.5 × 10{sup 9} cm s{sup –1}. Though gravitationally unbound, the ashes still have unburned helium (?80% in the thinnest cases) and only reach up to heavy elements such as {sup 40}Ca, {sup 44}Ti, {sup 48}Cr, and {sup 52}Fe. It is rare for these thin shells to generate large amounts of {sup 56}Ni. We also find a new set of solutions that can propagate in even thinner helium layers when {sup 16}O is present at a minimum mass fraction of ?0.07. Driven by energy release from ? captures on {sup 16}O and subsequent elements, these slow detonations only create ashes up to {sup 28}Si in the outer detonated He shell. We close by discussing how the unbound helium burning ashes may create faint and fast 'Ia' supernovae as well as events with virtually no radioactivity, and speculate on how the slower helium detonation velocities impact the off-center ignition of a carbon detonation that could cause a Type Ia supernova in the double detonation scenario.

  9. Determination of helium in beryl minerals

    International Nuclear Information System (INIS)

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

  10. A nuclear physical method for determining helium in surface layers of materials

    International Nuclear Information System (INIS)

    The method of recoil nuclei, which permits to obtain data on integral content, differential distribution, and in crystal structures - on location in lattice of helium impUrity atoms without sample destruction, has been considered. The method is based on impurity nuclei recording, which are knocked off the sample layer analyzed as a result of elastic cocollisions with accelerated ions. When heavy ions are used the method of recoil nuclei permits to determine helium impurities with the concentration above 5x1012 atom/cm2. The thickness of the layer analyzed can reach 1 ?m at the resolution approximately 40 nm. Determination of helium impurity implanted with the energy up to 200 keV is possible. Results of helium determination in the alloy Ti-Al-V made using a cyclotron with the energy of nitrogen accelerated ions 16 MeV are presented. The bunch current in the chamber constituted 0.05 ?A. To record recoil nuclei a silicon surface-barrier detector with the resolution 40 keV is used. A good separation of peaks corresponding to recoil nuclei of hydrogen and helium adsorbed on the surface sample, which are implanted with the energy 30 keV and dose 5X1017 and 1x1016 atom/cm2, is observed. Residual concentration of helium constitutes 2.45x1016 atom/cm2 for the introduced dose 5x1017 atom/cm2

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

    International Nuclear Information System (INIS)

    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 ?s, resulting in an equilibrium coverage of ?4%, the neon simulation has a lower deposition efficiency (3.5%) compared to that of the helium simulation (6.5%). At larger residence time (10 ms) and consequently larger equilibrium coverage (85%) the deposition efficiencies of helium and neon increased to 49% and 21%, respectively; which is dominated by increased lateral growth rates leading to broader pillars. The nanoscale growth is further studied by varying the ion beam diameter at 10 ms precursor residence time. The study shows that total SE yield decreases with increasing beam diameters for both the ion types. However, helium has the larger SE yield as compared to that of neon in both the low and high precursor residence time, and thus pillars are wider in all the simulations studied. (paper)d. (paper)

  12. Probing helium nano-bubble formation in tungsten with grazing incidence small angle x-ray scattering

    Science.gov (United States)

    Thompson, M.; Kluth, P.; Doerner, R. P.; Kirby, N.; Corr, C.

    2015-04-01

    Helium nano-bubble formation in plasma facing materials has emerged as a major concern for the next-step fusion experiment ITER, where helium plasmas will be used during the tokamak's start-up phase. Here, we demonstrate that grazing incidence small-angle x-ray scattering is a powerful technique for the analysis of helium nano-bubble formation in tungsten. We measured helium bubbles with sizes between 1.5–2.5 nm in tungsten exposed to helium plasma at 700 °C, where a smaller number of larger bubbles were also observed. Depth distributions can be estimated by taking successive measurements across a range of x-ray incidence angles. Compared with traditional approaches in the field, such as transmission electron microscopy, this technique provides information across a much larger volume with high statistical precision, whilst also being non-destructive.

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

    Science.gov (United States)

    Bai, H.; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W.

    2014-03-01

    High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32 T, 32 mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T2/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32 T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40 mm and an outer diameter of 140 mm was fabricated and tested in a resistive magnet providing a background field of 15 T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5 T at a current of 200 A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-31

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

  15. Reduction of cardiac cell death after helium postconditioning in rats: transcriptional analysis of cell death and survival pathways.

    Science.gov (United States)

    Oei, Gezina T M L; Heger, Michal; Van Golen, Rowan F; Alles, Lindy K; Flick, Moritz; Van Der Wal, Allard C; Van Gulik, Thomas M; Hollmann, Markus W; Preckel, Benedikt; Weber, Nina C

    2014-08-26

    Helium, a noble gas, has been safely used in humans. In animal models of regional myocardial ischemia/reperfusion it was shown that helium conditioning reduces infarct size. Currently it is not known how helium exerts its cytoprotective effects and which cell death/survival pathways are affected. The objective of this study was therefore to investigate the cell protective effects of helium postconditioning by PCR array analysis of genes involved in necrosis, apoptosis, and autophagy. Male rats were subjected to 25 min of ischemia and 5, 15, or 30 min of reperfusion. Semiquantitative histological analysis revealed that 15 min of helium postconditioning reduced the extent of ischemia/reperfusion-induced cell damage. This effect was not observed after 5 and 30 min of helium postconditioning. Analysis of the differential expression of genes showed that 15 min of helium postconditioning mainly caused upregulation of genes involved in autophagy and inhibition of apoptosis versus ischemia/reperfusion alone. The results suggest that the cytoprotective effects of helium inhalation may be caused by a switch from pro-cell death signaling to activation of cell survival mechanisms, which appears to affect a wide range of pathways. PMID:25171109

  16. Comparison of the measured X-ray yields of kaonic helium-3 and helium-4

    International Nuclear Information System (INIS)

    Kaonic helium is an exotic atom where a Kaon replaces a shell electron, well suited for the study of the strong interaction at low energies. The strong interaction between the kaon and the nucleus affects the low-lying atomic states in the kaonic helium atom by causing a shift compared to its electromagnetic value. This shift can be measured with spectroscopic tools, which was performed recently by two experiments. In particular, the SIDDHARTA experiment at LNF (Italy) investigated the strong interaction shift via the measurement of the X-ray transitions to the 2p level in kaonic helium-3 and kaonic helium-4. The E17 experiment at J-PARC (Japan), planned for 2012, measures a possible difference between the shifts in kaonic helium-3 and helium-4. For this purpose, so-called “silicon drift detectors” are used which have been optimized for the requirements of the experiment. Due to geometrical limits of the E17setup, the properties of these detectors have been investigated in a similar setup. Their energy and time resolutions have been studied as a function of the detector temperature and compared to theoretical models of the electron mobility in silicon. Furthermore, the yields (i.e. the transition rates) of the kaonic helium X-ray transitions to the 2p level were determined within this thesis. Therefore, the SIDDHARTA data were analysed, where the X-ray transitions in gaseous kaonic helium-3 and helium-4 were measured with a complex SDD detector system. The absolute yields were obtained with inputs from a Monte Carlo simulation. Since the previous measurements on the kaonic helium X-ray transitions solely used liquid kaonic helium, these results give crucial information on theoretical calculations of the density dependence of the yields. Additionally, the determination of the yields in gaseous kaonic helium-3 and helium-4 allows an estimation of the prospective X-ray detection efficiencies in E17. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    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. Determination of electron temperature in a Penning discharge by the helium line ratio method

    Science.gov (United States)

    Richardson, R. W.

    1975-01-01

    The helium spectral line intensity ratio technique utilizes the difference in electron energy dependences of the ground state electron impact excitation cross sections of the singlet and triplet series of neutral helium and the excited states of helium ions to determine the electron temperatures in a toroidal steady-state Penning discharge operating in helium. By varying the Penning discharge anode voltage and background pressure over a range of 2.5 to 28 kV and 0.00005 to 0.0001 torr, respectively, it was possible to make a comparison of the electron temperature as measured from various possible line ratios over a wide range of temperatures (10 to 100+ eV) under reproducible steady-state conditions.

  19. Implementation of two-phase tritium models for helium bubbles in HCLL breeding blanket modules

    Energy Technology Data Exchange (ETDEWEB)

    Fradera, J., E-mail: jordi.fradera@upc.edu [Department of Physics and Nuclear Engineering, Tech. Univ. of Catalonia (UPC) GREENER-GET-T4F, Av. Diagonal 647, 08028 Barcelona (Spain); UPC, Department of Physics and Nuclear Engineering (DFEN), ETSEIB, Av. Diagonal 647, 08028 Barcelona (Spain); Sedano, L. [Breeding Blanket Technologies Unit, Av. Complutense 22, 28040 EURATOM-CIEMAT Fusion Association, Madrid (Spain); Mas de les Valls, E. [UPC, Department of Physics and Nuclear Engineering (DFEN), ETSEIB, Av. Diagonal 647, 08028 Barcelona (Spain); Department of Heat Engines, Tech. Univ. of Catalonia (UPC) GREENER-GET-T4F, Av. Diagonal 647, 08028 Barcelona (Spain); Batet, L. [Department of Physics and Nuclear Engineering, Tech. Univ. of Catalonia (UPC) GREENER-GET-T4F, Av. Diagonal 647, 08028 Barcelona (Spain); UPC, Department of Physics and Nuclear Engineering (DFEN), ETSEIB, Av. Diagonal 647, 08028 Barcelona (Spain)

    2011-10-01

    Tritium self-sufficiency requirement of future DT fusion reactors involves large helium production rates in the breeding blankets; this might impact on the conceptual design of diverse fusion power reactor units, such as Liquid Metal (LM) blankets. Low solubility, long residence-times and high production rates create the conditions for Helium nucleation, which could mean effective T sinks in LM channels. A model for helium nano-bubble formation and tritium conjugate transport phenomena in liquid Pb17.5Li and EUROFER is proposed. In a first approximation, it has been considered that He bubbles can be represented as a passive scalar. The nucleation model is based on the classical theory and includes a simplified bubble growth model. The model captures the interaction of tritium with bubbles and tritium diffusion through walls. Results show the influence of helium cavitation on tritium inventory and the importance of simulating the system walls instead of imposing fixed boundary conditions.

  20. Implementation of two-phase tritium models for helium bubbles in HCLL breeding blanket modules

    International Nuclear Information System (INIS)

    Tritium self-sufficiency requirement of future DT fusion reactors involves large helium production rates in the breeding blankets; this might impact on the conceptual design of diverse fusion power reactor units, such as Liquid Metal (LM) blankets. Low solubility, long residence-times and high production rates create the conditions for Helium nucleation, which could mean effective T sinks in LM channels. A model for helium nano-bubble formation and tritium conjugate transport phenomena in liquid Pb17.5Li and EUROFER is proposed. In a first approximation, it has been considered that He bubbles can be represented as a passive scalar. The nucleation model is based on the classical theory and includes a simplified bubble growth model. The model captures the interaction of tritium with bubbles and tritium diffusion through walls. Results show the influence of helium cavitation on tritium inventory and the importance of simulating the system walls instead of imposing fixed boundary conditions.

  1. Helium hammer in superfluid transfer

    International Nuclear Information System (INIS)

    Large transient pressure pulses, referred to as a helium hammer, which occurred in the transfer line of the main cryogenic tank during the development tests of the Infrared Astronomical Satellite, launched on January 25, 1983, are analyzed, and the measures taken to prevent a failure described. The modifications include an installation of a 2.3-liter surge tank upstream, and a back-up relief valve downstream, of a burst disk. The surge tank is designed to attenuate a 0.33-MPa pressure pulse at the inlet down to 0.092 MPa at the outlet. A mechanism of the pulse generation is suggested, which involves flashing and rapid recondensation of the small amount of liquid entering the warm section of a transition to room temperature

  2. Superfluid helium physics and applications

    CERN Document Server

    Vinen, W F; CERN. Geneva

    1999-01-01

    The behaviour of liquid helium is dominated by quantum effects, which give rise to superfluidity at low temperatures. An account will be given of the observed properties of the superfluid phase of liquid 4He, and of the way in which these properties can be described by a two-fluid model, supplemented by the requirement that motion of the superfluid component be irrotational with a hydrodynamic circulation that is quantized in units of h/m4. The existence of superfluidity and the quantization of circulation will be related to the presence of a Bose condensate. The description of excited states of the liquid in terms of weakly interacting thermal excitations (phonons and rotons will be discussed, and the relation between these excitations and the normal-fluid component will be explained. The existence and role of quantized vortex lines in the superfluid component will be discribed. A brief account will be included of topics of current research interest.

  3. Group representations and superfluid helium

    International Nuclear Information System (INIS)

    The spectrum of states of superfluid helium-4 is described by the representation theory of groups. Starting from the symmetry group, describing the fluctuations of Bose-Einstein condensed states of zero momentum, the excited states by non-compact groups are described. This contains complete information about the system including degeneracy, energy levels etc. This leads to the possibility of classifying all realistic interactions. As this formalism is equivalent to the Hamiltonian formalism, this description restricts the ambiguous framework of the quantum-mechanical description where interaction or parameters can be varied arbitrarily. With all possible groups and representations, all the excited states can, in principle, be described. The paper is mainly concerned with the phonon spectrum and the roton-like and vortex excitations are also taken into consideration. (author)

  4. Helium hammer in superfluid transfer

    Science.gov (United States)

    Tward, E.; Mason, P. V.

    1984-01-01

    Large transient pressure pulses, referred to as a helium hammer, which occurred in the transfer line of the main cryogenic tank during the development tests of the Infrared Astronomical Satellite, launched on January 25, 1983, are analyzed, and the measures taken to prevent a failure described. The modifications include an installation of a 2.3-liter surge tank upstream, and a back-up relief valve downstream, of a burst disk. The surge tank is designed to attenuate a 0.33-MPa pressure pulse at the inlet down to 0.092 MPa at the outlet. A mechanism of the pulse generation is suggested, which involves flashing and rapid recondensation of the small amount of liquid entering the warm section of a transition to room temperature.

  5. The tensile strength of helium II

    International Nuclear Information System (INIS)

    The study of the negative pressure required to produce cavitation in liquid helium (i.e. the tensile strength of helium) has been of continuing interest for two reasons. Since all other elements have freezing temperatures of 14 K or higher, helium can be prepared free of gaseous impurities which can serve as centers for heterogeneous nucleation of bubbles which will reduce the tensile strength of the liquid. Secondly, helium remains a liquid even down to the absolute zero of temperature. Consequently, it has been considered that at sufficiently low temperatures there is the possibility that the rate of nucleation of bubbles is dominated by quantum tunneling. In this thesis, the authors reexamined the theory of homogeneous nucleation and made an estimate of the equation of state for negative pressure in helium. He found that the earlier theories were incorrect in that they took no account of the equation of state of liquid helium in the negative pressure regime. The tensile strength of helium at T = 0 K should be around -9 bars instead of -17 bars predicted by the standard theory

  6. In Beam Tests of Implanted Helium Targets

    CERN Document Server

    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...

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

    International Nuclear Information System (INIS)

    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.

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

    International Nuclear Information System (INIS)

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

  9. Helium: current status and future outlook

    International Nuclear Information System (INIS)

    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 figs., 1 tab

  10. Electrical heater for very-low pressure helium gas

    CERN Document Server

    Benda, V; Vuillierme, B

    1996-01-01

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

  11. Thermal behaviour of helium in silicon carbide: Influence of microstructure

    International Nuclear Information System (INIS)

    We have studied the microstructure dependence of He bubble formation in silicon carbide. Helium accumulation in SiC was performed by 500 keV 3He implantation at room temperature with a fluence of 5 * 1015 cm-2. Depth concentration profiles have been investigated in 6H-SiC single crystals and alpha-SiC polycrystals by NRA spectrometry. Cross-sectional TEM samples have been imaged to study bubble formation. After annealing at 1300 C, results clearly demonstrate an influence of grain boundaries on He retention yield in ?-SiC polycrystals while helium is totally released from single crystals. Polycrystals also display the formation of intragranular over pressurized bubbles while no bubbles are observed in single crystals. Interpretations are proposed on the basis of the nature of He traps. (authors)

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

    International Nuclear Information System (INIS)

    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

  13. Erosion of the non metallic materials under helium irradiation

    International Nuclear Information System (INIS)

    The character of processes occurring on helium ion implantation in silicon carbide-based materials and silicon single crystals the properties of which had been rather extensivvely studied providing for a ready interpretation and comparison of results was investigated using a comparative approach. The irradiation with helium ions was made using a linear accelerator in the energy range from 50 to 175 keV at dozes from 0.01 kl/cm2 to 6.5 kl/cm2 and temperatures from 120 to 600 deg C. It is stated that the main surface erosion mechanism in brittle materials irradiated with low-soluble gas ions is represented by spalling resulting in high effective erosion coefficient values. The erosion coefficient values have been found to decrease at high irradiation dozes. The dependence of erosion character on the structure of initial crystals has been studied

  14. Genetic changes in Mammalian cells transformed by helium cells

    International Nuclear Information System (INIS)

    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/?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

  15. Crystal structure and density of helium to 232 kbar

    International Nuclear Information System (INIS)

    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

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

    Science.gov (United States)

    Naitou, Y.; Iijima, T.; Ogawa, S.

    2015-01-01

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

  17. Magnetized microdischarge plasmas in low pressure argon and helium

    International Nuclear Information System (INIS)

    Magnetized microdischarge plasmas have been generated in low pressure argon and helium environments with planar electrodes and a non-uniform magnetic field configuration that can cause closed ExB electron drift. The electrode gap was 1 or 3 mm and the operating gas pressures were 0.5-55 Torr for argon or 1-100 Torr for helium. The breakdown voltage is found to be low with the use of a magnetic field at lower pressures as a result of the effective magnetization of electrons. The current-voltage relation at low pressures departs from the well-known current-voltage scaling that holds in the absence of a magnetic field. The magnetized microdischarge system for argon with copper electrodes exhibits a transition from positive to negative resistance when the operating pressure is decreased to below 10 Torr

  18. Genetic changes in Mammalian cells transformed by helium cells

    Energy Technology Data Exchange (ETDEWEB)

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

    1990-11-01

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

  19. Positron scattering in helium: Virtual-positronium resonances

    Energy Technology Data Exchange (ETDEWEB)

    Karwasz, G.P. [Facolta d' Ingegneria, Universita di Trento, 38050 Povo (Tunisia) (Italy)]. E-mail: karwasz@chemie.fu-berlin.de; Pliszka, D. [Instytut Fizyki, Pomorska Akademia Pedagogiczna, 76200 Slupsk (Poland); Zecca, A. [Dipartimento di Fisica, Universita di Trento, 38050 Povo (TN) (Italy); Brusa, R.S. [Dipartimento di Fisica, Universita di Trento, 38050 Povo (TN) (Italy)

    2005-11-15

    Total cross sections for positron scattering in helium and argon were measured at 0.5-25 eV with a new spectrometer from Trento University, with a good angular resolution (3.1 x 10{sup -4} sr). Data in argon fall in-between earlier measurements; those for He agree well with the previous above the positronium formation thresholds but are up to 50% higher at low energies. Data for He show four resonant-like structures, one at the positronium threshold formation (17.8 eV) predicted by Van Reeth and Humberston [J. Phys. B 32 (1999) L103], another at about 6.8 eV and two very prominent centred at 1.6 eV and 2.2 eV. Following Gribakin and King [J. Phys. B 27 (1994) 2639] the two latter could be signs of virtual-positronium formation in helium.

  20. Positron scattering in helium: Virtual-positronium resonances

    International Nuclear Information System (INIS)

    Total cross sections for positron scattering in helium and argon were measured at 0.5-25 eV with a new spectrometer from Trento University, with a good angular resolution (3.1 x 10-4 sr). Data in argon fall in-between earlier measurements; those for He agree well with the previous above the positronium formation thresholds but are up to 50% higher at low energies. Data for He show four resonant-like structures, one at the positronium threshold formation (17.8 eV) predicted by Van Reeth and Humberston [J. Phys. B 32 (1999) L103], another at about 6.8 eV and two very prominent centred at 1.6 eV and 2.2 eV. Following Gribakin and King [J. Phys. B 27 (1994) 2639] the two latter could be signs of virtual-positronium formation in helium

  1. LOCA analysis for Korean helium cooled solid breeder TBM

    International Nuclear Information System (INIS)

    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.

  2. Four-body conversion of atomic helium ions

    International Nuclear Information System (INIS)

    The conversion of atomic helium ions into molecular ions was studied in pure helium and in helium-neon mixtures containing between 0.1 at. % and 50 at. % neon. The experiments showed that the termolecular conversion reaction, He++2He ? He2++He, is augmented by the four-body conversion reaction He++3He ? products, where the products could include either He2+ or He3+ ions. Conversion rate coefficients of (5.7 +- 0.8) x 10-32 cm6 sec-1 and (2.6 +- 0.4) x 10-49 cm9 sec-1 were found for the termolecular and four-body conversion reactions, respectively. In addition, rate coefficients for the following Ne+ conversion reactions were measured: Ne++He+He ? (HeNe)++He, (2.3 +- 0.1) x 10-32 cm6 sec-1; Ne++He+Ne ? (HeNe)++Ne or Ne2++He, (8.0 +- 0.8) x 10-32 cm6 sec-1; and Ne++Ne+Ne ? Ne2++Ne, (5.1 +- 0.3) x 10-32 cm6 sec-1. All rate coefficients are at a gas temperature of 295 K

  3. Molecular dynamics simulations of the diffusion and coalescence of helium in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.L. [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Department of Physics, Guangxi University, Nanning 530004 (China); Wang, J. [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Hou, Q., E-mail: qhou@scu.edu.cn [Key Lab for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064 (China); Deng, A.H. [Department of Physics, Sichuan University, Chengdu 610064 (China)

    2014-03-15

    Molecular dynamics (MD) simulations are performed on the diffusion and coalescence of helium in tungsten. A new method for determining the effective capture radii (ECRs) and the dissociation energies of helium-related defects is proposed in this work. It is observed that the ECR of an interstitial helium atom trapping helium interstitials (denoted as He–He{sub n}, n = 1–3) decreases with increasing temperature, except for He–He{sub 2} at T < 400 K. The traditional view that the ECR is approximately equal to the lattice constant, which has been widely used in kinetic Monte Carlo (KMC) and rate theory (RT) models, is only valid in some cases. However, the ECR between an interstitial helium atom and a substitutional helium atom (denoted as He–HeV) always approximates the third nearest-neighbor tetrahedral positions of the HeV. The diffusion coefficients D{sub n} for helium clusters are also investigated. He{sub 2} migrates more quickly than a single He atom does at T < 400 K, whereas the diffusion path of He{sub 2} changes at higher temperatures. Another counterintuitive observation is that D{sub 5} > D{sub 3} > D{sub 4} at T < 500 K, which can be attributed to the disordered structure of He{sub 5}. The Arrhenius relation describes the diffusion of He{sub n} well in the temperature range from 300 K to 550 K, whereas the diffusion is not a standard thermally activated process at higher temperatures. Taken together, these results help elucidate the initial stage of helium bubble formation in tungsten as well as the requirements of long-term evolution methods such as KMC or RT models.

  4. Adiabatic hyperspherical study of the helium trimer

    International Nuclear Information System (INIS)

    The adiabatic hyperspherical method is used to investigate the spectrum of the helium trimer and to explore effects on the spectrum of varying the helium masses as well as the interaction strength. When a realistic helium dimer potential is adopted, only two isotopic combinations are observed to have three-body bound states: 4He3 and 4He23He. By artificially adjusting the dimer potential, we also determine the range of interaction strengths for which halo states can result. The existence of Efimov states for both physical and unphysical systems is also examined. copyright 1996 American Institute of Physics

  5. Helium migration in lithium aluminosilicate glasses

    International Nuclear Information System (INIS)

    Helium permeation, diffusion, and solubility have been measured for a number of lithium silicate and aluminosilicate glasses. Helium mobility in the lithium silicate glasses is controlled by the two-phase morphology of these glasses. Addition of as little as 2 mol% alumina strongly suppresses the tendency toward phase separation, i.e., yields homogeneous glasses. The compositional dependence of helium mobility in these glasses indicates that a major change in the glass structure occurs when the alumina-to-lithia ratio exceeds unity. Comparison of these results to those for analogous sodium aluminosilicates indicates that lithium has a greater effect than sodium on the free volume of the glass

  6. Helium flux from a sedimentary basin

    International Nuclear Information System (INIS)

    The tritium-3He ages of groundwaters collected from the Saijo Basin in Japan were measured. The ages vary between 11.7 and 16.3 years. The 4He flux of >3x104 atoms/cm2 s is calculated by the 4He concentrations and ages. In addition the helium flux of 8.3x105 atoms/cm2 s is calculated at the Higashi-Niigata gas field in Japan. The above two estimates are consistent with the continental helium flux reported in the literature, suggesting that helium flux on the Earth's crust is uniform

  7. Magnesium cluster film synthesis by helium nanodroplets.

    Science.gov (United States)

    Emery, Samuel B; Rider, Keith B; Little, Brian K; Schrand, Amanda M; Lindsay, C Michael

    2013-08-01

    Atomic and molecular clusters are a unique class of substances with properties that differ greatly from those of the bulk or single atoms due to changes in surface to volume ratio and finite size effects. Here, we demonstrate the ability to create cluster matter films using helium droplet mediated cluster assembly and deposition, a recently developed methodology that condenses atoms or molecules within liquid helium droplets and then gently deposits them onto a surface. In this work, we examine magnesium nanocluster films, which exhibit growth behavior comparable to low-energy cluster beam methods, and demonstrate physical properties and morphology dependent on helium droplet size. PMID:23927262

  8. Evolution of dopant-induced helium nanoplasmas

    CERN Document Server

    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.

  9. Kilohertz laser ablation for doping helium nanodroplets

    CERN Document Server

    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.

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

    International Nuclear Information System (INIS)

    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 continact 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

  11. KMC simulation of helium bubble formation in alpha-Fe

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xun; Zhang, Xitong [State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Xue, Jianming, E-mail: jmxue@pku.edu.cn [State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Li, Weisen [State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)

    2013-07-15

    We use Kinetic Monte Carlo (KMC) method to investigate the evolution of Helium-Vacancy clusters under different conditions with emphasizing the influence of system temperature. Our simulation results indicate that when initial helium concentration increases, the size and amount of the Helium-Vacancy cluster will increase dramatically. The Helium-Vacancy cluster will become larger accompanied with a decrease in its amount as the temperature increases. The results also indicate that irradiating He-contained sample produces less helium bubbles compared with other conditions, adding helium during irradiating the sample or adding helium atoms after the sample have been irradiated.

  12. KMC simulation of helium bubble formation in alpha-Fe

    International Nuclear Information System (INIS)

    We use Kinetic Monte Carlo (KMC) method to investigate the evolution of Helium-Vacancy clusters under different conditions with emphasizing the influence of system temperature. Our simulation results indicate that when initial helium concentration increases, the size and amount of the Helium-Vacancy cluster will increase dramatically. The Helium-Vacancy cluster will become larger accompanied with a decrease in its amount as the temperature increases. The results also indicate that irradiating He-contained sample produces less helium bubbles compared with other conditions, adding helium during irradiating the sample or adding helium atoms after the sample have been irradiated

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

    Science.gov (United States)

    Kogut, Alan; James, Bryan; Fixsen, Dale

    2013-01-01

    Astrophysical observations at millimeter wavelengths require large (2-to-5- meter diameter) telescopes carried to altitudes above 35 km by scientific research balloons. The scientific performance is greatly enhanced if the telescope is cooled to temperatures below 10 K with no emissive windows between the telescope and the sky. Standard liquid helium bucket dewars can contain a suitable telescope for telescope diameter less than two meters. However, the mass of a dewar large enough to hold a 3-to-5-meter diameter telescope would exceed the balloon lift capacity. The solution is to separate the functions of cryogen storage and in-flight thermal isolation, utilizing the unique physical conditions at balloon altitudes. Conventional dewars are launched cold: the vacuum walls necessary for thermal isolation must also withstand the pressure gradient at sea level and are correspondingly thick and heavy. The pressure at 40 km is less than 0.3% of sea level: a dewar designed for use only at 40 km can use ultra thin walls to achieve significant reductions in mass. This innovation concerns new construction and operational techniques to produce a lightweight liquid helium bucket dewar. The dewar is intended for use on high-altitude balloon payloads. The mass is low enough to allow a large (3-to-5-meter) diameter dewar to fly at altitudes above 35 km on conventional scientific research balloons without exceeding the lift capability of the balloon. The lightweight dewar has thin (250- micron) stainless steel walls. The walls are too thin to support the pressure gradient at sea level: the dewar launches warm with the vacuum space vented continuously during ascent to eliminate any pressure gradient across the walls. A commercial 500-liter storage dewar maintains a reservoir of liquid helium within a minimal (hence low mass) volume. Once a 40-km altitude is reached, the valve venting the vacuum space of the bucket dewar is closed to seal the vacuum space. A vacuum pump then evacuates the dewar vacuum space to provide the necessary thermal isolation. Liquid helium may then be transferred from the storage dewar into the bucket dewar to cool the telescope inside the bucket dewar. By splitting the functions of helium storage and in-flight thermal isolation, the parasitic mass associated with the dewar pressure vessel is eliminated to achieve factor-of-five or better reduction in mass. The lower mass allows flight on conventional scientific research balloons, even for telescopes 3 to 5 meters in diameter.

  14. Optical and electron spin resonance studies of xenon-nitrogen-helium condensates containing nitrogen and oxygen atoms.

    Science.gov (United States)

    Boltnev, Roman E; Bykhalo, Igor B; Krushinskaya, Irina N; Pelmenev, Alexander A; Khmelenko, Vladimir V; Mao, Shun; Meraki, Adil; Wilde, Scott C; McColgan, Patrick T; Lee, David M

    2015-03-19

    We present the first observations of excimer XeO* molecules in molecular nitrogen films surrounding xenon cores of nanoclusters. Multishell nanoclusters form upon the fast cooling of a helium jet containing small admixtures of nitrogen and xenon by cold helium vapor (T = 1.5 K). Such nanoclusters injected into superfluid helium aggregate into porous impurity-helium condensates. Passage of helium gas with admixtures through a radio frequency discharge allows the storage of high densities of radicals stabilized in impurity-helium condensates. Intense recombination of the radicals occurs during destruction of such condensates and generates excited species observable because of optical emission. Rich spectra of xenon-oxygen complexes have been detected upon destruction of xenon-nitrogen-helium condensates. A xenon environment quenches metastable N((2)D) atoms but has a much weaker effect on the luminescence of N((2)P) atoms. Electron spin resonance spectra of N((4)S) atoms trapped in xenon-nitrogen-helium condensates have been studied. High local concentrations of nitrogen atoms (up to 10(21) cm(-3)) stabilized in xenon-nitrogen nanoclusters have been revealed. PMID:25353614

  15. The formation of helium bubbles in 316L SS irradiated with helium ions at different temperatures

    International Nuclear Information System (INIS)

    Specimens of 20% cold worked 316L SS were irradiated with 2.5 MeV 4He+ at room temperature, 500 and 600 C separately. The bubble structures in bulk were investigated in a transmission electron microscope with cross sectional technique. As the irradiation temperature is raised from room temperature to 500 C, the bubbles grow slowly. When the irradiated temperature is varied from 500 to 600 C, the bubbles grow very fast. This means there is a turning point of bubbles evolution between 500 and 600 C. At the same temperature, the bubble size and density tend to saturation with the increasing of helium atom concentration and displacement per atom (dpa). ((orig.))

  16. Inelastic scattering of electrons by helium

    International Nuclear Information System (INIS)

    Measurements of the angular distribution and total cross section for all inelastic processes in the scattering of intermediate and high energy electrons by helium atoms are analyzed using the first Born approximation. (orig.)

  17. Rotational superfluidity in small helium droplets.

    Science.gov (United States)

    Mateo, David; Gonzalez, Frisly; Eloranta, Jussi

    2015-03-19

    The first minimum appearing in molecular rotational constants as a function of helium droplet size has been previously associated with the onset of superfluidity in these finite systems. We investigate this relationship by bosonic density functional theory calculations of classical molecular rotors (OCS, N2O, CO, and HCN) interacting with the surrounding helium. The calculated rotational constants are in fair agreement with the existing experimental data, demonstrating the applicability of the theoretical model. Inspection of the spatial evolution of the global phase and density shows the increase in the rotational constant after the first minimum correlates with continuous coverage of the molecule by helium and the appearance of angular phase coherence rather than completion of the first solvent shell. We assign the observed phenomenon to quantum phase transition between a localized state and one-dimensional superfluid, which represents the onset of rotational superfluidity in small helium droplets. PMID:25099743

  18. Weir flow meter for saturated liquid helium

    International Nuclear Information System (INIS)

    This paper presents the design and test results of a weir used to measure the flow rate of saturated liquid helium in a two phase helium flow stream. The flow meter requires the presence of saturated vapor to measure the liquid flow rate but does not measure the vapor flow rate. The weir, located at a high point in the flow path, acts as a dam and creates a reservoir of liquid behind it. Liquid helium drains through a notch in the weir. The liquid helium level behind the weir is measured to determine the flow rate. The level increases with flow rate. The unmeasured vapor passes over the top of the weir and mixes with the liquid downstream of the weir. A weir was installed on the outlet of a string of superconducting magnets

  19. The helium detector - theory and practice

    International Nuclear Information System (INIS)

    In many fields, e.g., air pollution measurements or purity control of gases the determination of small concentrations of inorganic compounds is necessary. In these cases the use of helium detectors for the detection of such compounds down to the ppb-region is required, but is involves some difficulties. These difficulties consist in the theoretical description of the processes which cause the response, in the occurrence of negative peaks of O2, N2, H2 and Ar under use of ultra-pure helium as carrier gas, and in the experimental problem of the absolute gas-tightness of all parts of the gas chromatographic arrangement including the helium detector. Theoretical and experimental works performed by the authors in the last years provided an optimization of the geometry and function of the helium detector and made it possible to use this detector for routine analysis of inorganic trace compounds. These results are discussed. (author)

  20. Simple derivation of helium Lamb shift

    International Nuclear Information System (INIS)

    A simple derivation of Lamb shift in the two-electron helium atom, in the spirit of nonrelativistic quantum electrodynamics, is presented. Moreover, a complete expression for the leading recoil correction is derived for the first time. (author)

  1. Development of charcoal sorbents for helium cryopumping

    International Nuclear Information System (INIS)

    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

  2. Helium release from type 304 stainless steel

    International Nuclear Information System (INIS)

    Helium in very low concentration (less than 1 atomic ppB) has been introduced into type 304 stainless steel by radioactive decay of dissolved tritium. Release of this helium during subsequent annealing was monitored with a high sensitivity mass spectrometric gas analyzer. With isochronal annealing, helium is released in two temperature ranges, one near 3000C and the other between 8000C and the melting point. The latter release is interpreted as attributable to helium gas bubbles. The release near 3000C was studied isothermally between 150 and 3000C and is analyzed in terms of two stages of exponential decay. The fast and slow release stages have relaxation times near 102 and 103 s, respectively, and the fast release accounts for roughly 85 percent of the total release at low temperature. From an analysis of the temperature dependence of the release rate, it is concluded that volume diffusion is the controlling mechanism for the outgassing

  3. Helium migration in alkali germanate glasses

    International Nuclear Information System (INIS)

    Helium permeability, diffusivity, and solubility have been measured for sodium, potassium, rubidium, and cesium germanate glasses, and for one series of sodium-potassium germanate glasses. In each case, the helium permeability and diffusivity exhibit minima in the property-composition curves. These minima shift to greater alkali oxide content and increase in magnitude in the order Cs, Rb, K, Na-K, Na. These minima result from corresponding maxima in activation energy for helium migration. Helium solubilities do not exhibit similar minima, but rather decrease monotonically with increasing alkali oxide content. These results appear to be related to free-volume changes in the glasses as a function of composition. The inability of the current structural model for these glasses to explain the results of the present study raises questions regarding the validity of that model

  4. Leak tests with helium leak indicators

    International Nuclear Information System (INIS)

    In this work a short overview is given of the different leakage search methods and the main functions (main current, inverse current) of modern helium leak indicators as well as several example for application are presented. (orig./HP)

  5. Photoelectron Spectroscopy of Doped Helium Nanodroplets

    Science.gov (United States)

    Loginov, Evgeny; Drabbels, Marcel

    2010-06-01

    The photoionization of aromatic molecules (aniline, phenol, and toluene) in helium droplets was studied with photoelectron spectroscopy. The photoelectron spectra resemble closely those of gas phase molecules except for the droplet size dependent shift. This shift is caused by the lowering of the ionization threshold upon solvation and can be readily estimated. The individual peaks in photoelectron spectra are broadened, which is thought to partially reflect the rearrangement of helium upon ion solvation. The droplet size and kinetic energy dependences of the peak broadening towards lower energy may be attributed to the relaxation of the photoelectrons as they pass through a helium droplet. ZEKE spectroscopy of surface-doped helium droplets will be discussed.

  6. Primordial helium abundance determination from metal-poor galaxies

    International Nuclear Information System (INIS)

    The advantages of measuring the helium abundance in metal-poor emission-line galaxies are emphasized. Recent results are reviewed and seem to converge to a primordial helium abundance Yp = 0.24 + or - 0.01. There is little evidence so far for a relation between the helium abundance and the oxygen abundance whereas nitrogen seems to correlate better with the observed helium. Uncertainties are discussed as well as prospects for future improvements in the helium abundance determination. 20 references

  7. The helium trimer with soft-core potentials

    OpenAIRE

    Kievsky, A.; Garrido, Eduardo; Romero-redondo, C.; Barletta, P.

    2011-01-01

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

  8. Gas turbine modeling for NPP with helium cooled reactor

    International Nuclear Information System (INIS)

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

  9. Helium pumping with liquid ring vacuum pump

    International Nuclear Information System (INIS)

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

  10. Explosive helium burst in thermal spring emanations

    Energy Technology Data Exchange (ETDEWEB)

    Das, Nisith K. [Variable Energy Cyclotron Center, 1/AF Bidhannagar, Kolkata 700064 (India)]. E-mail: nkdas@veccal.ernet.in; Bhandari, Rakesh K. [Variable Energy Cyclotron Center, 1/AF Bidhannagar, Kolkata 700064 (India); Ghose, Debasis [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sen, Prasanta [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)]. E-mail: psen@anp.saha.ernet.in; Sinha, Bikash [Variable Energy Cyclotron Center, 1/AF Bidhannagar, Kolkata 700064 (India); Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2006-01-01

    An observation has been made of an explosive helium burst showing an anomalous concentration of helium of {approx}61.6 vol% compared to the {approx}1.4 vol% normally present in the thermal spring gas emanations at Bakreswar, West Bengal. This elevated level, along with deuterium {approx}1.7 vol%, has been observed for the first time in a gas chromatograph. Attempts have been made to correlate the observations, as a precursory signal, with some recent major tectonic disturbances.

  11. Helium burning in moderate-mass stars

    OpenAIRE

    Weiss, Achim

    2011-01-01

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

  12. Electrons on the surface of liquid helium

    International Nuclear Information System (INIS)

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

  13. Effects of helium impurities on superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Selle, J.E.

    1977-07-01

    A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    Helium pumping on argon frost has been investigated on TFTR neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are ? 25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, > 20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a two-fold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 torr-l of helium, the beamline base pressure rose to 2x10-5 torr from an initial value of 10-8 torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 torr-l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity. 29 refs., 7 figs

  16. Helium generation in fusion reactor materials. Technical progress report, October 1976--March 1977

    International Nuclear Information System (INIS)

    The immediate objectives of this program are to measure the spectrum-integrated helium generation rates and cross sections of several materials in the available high intensity neutron sources, and to develop neutron dosimetry procedures using some of these materials. This requires further development of foil activation dosimetry techniques, since the cross section measurements require a detailed characterization of each neutron environment. The neutron facilities presently used in this program include accelerators producing d-T and d-Be reactions and high flux mixed-spectrum fission reactors. Most of the work reported here has focused on neutron spectra from the d-T reaction. A description is given of the preliminary analysis of wire rings included in the irradiation capsule for helium accumulation fluence dosimetry. The results show non-uniformities in the neutron fluence distribution characterizing this irradiation, and point out the value of helium accumulation fluence dosimetry for characterizing high energy (approximately 5 to 30 MeV) neutron fields. The helium accumulation fluence data are being used to adjust the neutron fluence map for calculation of final helium generation cross sections from the other RTNS-irradiated pure element specimens. Most of the specimens irradiated in the RTNS-I experiment have been analyzed for helium, and preliminary results are presented

  17. THE GREEN BANK TELESCOPE H II REGION DISCOVERY SURVEY. IV. HELIUM AND CARBON RECOMBINATION LINES

    Energy Technology Data Exchange (ETDEWEB)

    Wenger, Trey V.; Bania, T. M. [Astronomy Department, 725 Commonwealth Avenue, Boston University, Boston, MA 02215 (United States); Balser, Dana S. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903-2475 (United States); Anderson, L. D. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

    2013-02-10

    The Green Bank Telescope H II Region Discovery Survey (GBT HRDS) found hundreds of previously unknown Galactic regions of massive star formation by detecting hydrogen radio recombination line (RRL) emission from candidate H II region targets. Since the HRDS nebulae lie at large distances from the Sun, they are located in previously unprobed zones of the Galactic disk. Here, we derive the properties of helium and carbon RRL emission from HRDS nebulae. Our target sample is the subset of the HRDS that has visible helium or carbon RRLs. This criterion gives a total of 84 velocity components (14% of the HRDS) with helium emission and 52 (9%) with carbon emission. For our highest quality sources, the average {sup 4}He{sup +}/H{sup +} abundance ratio by number, (y {sup +}), is 0.068 {+-} 0.023(1{sigma}). This is the same ratio as that measured for the sample of previously known Galactic H II regions. Nebulae without detected helium emission give robust y {sup +} upper limits. There are 5 RRL emission components with y {sup +} less than 0.04 and another 12 with upper limits below this value. These H II regions must have either a very low {sup 4}He abundance or contain a significant amount of neutral helium. The HRDS has 20 nebulae with carbon RRL emission but no helium emission at its sensitivity level. There is no correlation between the carbon RRL parameters and the 8 {mu}m mid-infrared morphology of these nebulae.

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

    International Nuclear Information System (INIS)

    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 at sign 4.5 K helium refrigerator and a 25 m3 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

  19. Cryopumping of deuterium hydrogen and helium mixtures on smooth 4.2 K surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Chou, T. S.; Halama, H. J.

    1977-01-01

    The large quantities of deuterium and hydrogen to be pumped in a fusion reactor and its subsystems favor cryopumping over other pumping methods. Cryogen consumption and the operating pressure will not only depend on the gas to be pumped, but also on the amount of helium gas present in the system. In fact, residual helium pressure between pulses will determine the power dissipation of the pump, and hence, influence the choice of cryocondensation or cryosorption. In this paper we will present the results of our studies on (1) cryotrapping of helium in thick D/sub 2/ and H/sub 2/ films and hydrogen in D/sub 2/ films at 4.2 K; (2) diffusion of He and H/sub 2/ from D/sub 2/ films; (3) steady-state liquid helium consumption; (4) liquid helium consumption as a function of D/sub 2/ and H/sub 2/ fluxes being pumped; (5) liquid helium consumption as a function of He partial pressure in the system. Finally, these measurements will suggest maximum permissible He to D/sub 2/ and He to H/sub 2/ ratios in a cryocondensation pump.

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

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

  2. THE GREEN BANK TELESCOPE H II REGION DISCOVERY SURVEY. IV. HELIUM AND CARBON RECOMBINATION LINES

    International Nuclear Information System (INIS)

    The Green Bank Telescope H II Region Discovery Survey (GBT HRDS) found hundreds of previously unknown Galactic regions of massive star formation by detecting hydrogen radio recombination line (RRL) emission from candidate H II region targets. Since the HRDS nebulae lie at large distances from the Sun, they are located in previously unprobed zones of the Galactic disk. Here, we derive the properties of helium and carbon RRL emission from HRDS nebulae. Our target sample is the subset of the HRDS that has visible helium or carbon RRLs. This criterion gives a total of 84 velocity components (14% of the HRDS) with helium emission and 52 (9%) with carbon emission. For our highest quality sources, the average 4He+/H+ abundance ratio by number, (y +), is 0.068 ± 0.023(1?). This is the same ratio as that measured for the sample of previously known Galactic H II regions. Nebulae without detected helium emission give robust y + upper limits. There are 5 RRL emission components with y + less than 0.04 and another 12 with upper limits below this value. These H II regions must have either a very low 4He abundance or contain a significant amount of neutral helium. The HRDS has 20 nebulae with carbon RRL emission but no helium emission at its sensitivity level. There is no correlation between the carbon RRL parameters and the 8 ?m mid-infrared morphology of these nebulae.ulae.

  3. Tritium-helium effects in metals

    Energy Technology Data Exchange (ETDEWEB)

    Caskey, G.R. Jr.

    1985-01-01

    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,..cap alpha..) 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.

  4. Separation of compressor oil from helium

    International Nuclear Information System (INIS)

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

  5. Primordially produced helium-4 in the presence of neutrino oscillations

    International Nuclear Information System (INIS)

    The production of helium-4 during the cosmological nucleosynthesis in the presence of active-sterile neutrino oscillations, ?e??s, efficient after decoupling of electron neutrino, is analyzed. All known oscillation effects on primordial nucleosynthesis, namely: increase of the effective degrees of freedom during nucleosynthesis, neutrino spectrum distortion, depletion of electron neutrino number density and generation of neutrino-antineutrino asymmetry, are precisely taken into account. Primordially produced 4He abundance is calculated, in a self-consistent study of the kinetics of the nucleons and the oscillating neutrinos, for the full range of parameters of the oscillation model with small mass differences: ?m2?10-7 eV2. A considerable relative increase of helium-4, up to 14% for non-resonant oscillations and up to 32% for resonant ones is registered for a certain interval of oscillations parameters values. Combined iso-helium contours ?Yp/Yp= 3%, 5%, 7% for resonant and non-resonant oscillations are presented. Cosmological constraints on oscillation parameters and on the sterile solar neutrino solutions are discussed. (author)

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

    CERN Document Server

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

    2013-01-01

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

  7. Reliability study of sheathed thermocouples in helium environment

    International Nuclear Information System (INIS)

    The reliability of the sheathed thermocouples used for the temperature instrumentation for the high temperature helium gas loop, HENDEL, was examined in the range from 1000 to 1200 deg C. The test was carried out in pure helium for 1000 hours at the longest in the state of contact with graphite. When Hastelloy X or Inconel 600 was used as the sheath material, the adhesion with graphite was observed at 1200 deg C, but it was prevented by the plasma spraying of Al2O3 or ZrO2 on the surface. The thermocouple wires of platinum group reacted with insulator MgO. This phenomenon was especially intensive when the sheath material was tantalum or Inconel 600, and the electromotive force dropped remarkably. On the other hand, when Pt-10% Rh alloy was used as the sheath material, the reaction was suppressed, and the electromotive force was stable even after 1000 hours at 1200 deg C. The sheathed thermocouples for the HENDEL require the compatibility with graphite, the corrosion resistance to the impurities in helium gas and the stability of electromotive force from the conditions of their use. Using various combinations of sheath materials and thermocouple wires, these properties were examined, and the combinations of R thermocouple-PR 10% sheath and WRe 5-26% thermocouple-tantalum sheath showed good results. (Kako, I.)

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

    Science.gov (United States)

    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

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

    CERN Document Server

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

    2011-01-01

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

  10. Investigation of Cellular Interactions of Nanoparticles by Helium Ion Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arey, Bruce W.; Shutthanandan, V.; Xie, Yumei; Tolic, Ana; Williams, Nolann G.; Orr, Galya

    2011-06-01

    The helium ion mircroscope (HIM) probes light elements (e.g. C, N, O, P) with high contrast due to the large variation in secondary electron yield, which minimizes the necessity of specimen staining. A defining characteristic of HIM is its remarkable capability to neutralize charge by the implementation of an electron flood gun, which eliminates the need for coating non-conductive specimens for imaging at high resolution. In addition, the small convergence angle in HeIM offers a large depth of field (~5x FE-SEM), enabling tall structures to be viewed in focus within a single image. Taking advantage of these capabilities, we investigate the interactions of engineered nanoparticles (NPs) at the surface of alveolar type II epithelial cells grown at the air-liquid interface (ALI). The increasing use of nanomaterials in a wide range of commercial applications has the potential to increase human exposure to these materials, but the impact of such exposure on human health is still unclear. One of the main routs of exposure is the respiratory tract, where alveolar epithelial cells present a vulnerable target at the interface with ambient air. Since the cellular interactions of NPs govern the cellular response and ultimately determine the impact on human health, our studies will help delineating relationships between particle properties and cellular interactions and response to better evaluate NP toxicity or biocompatibility. The Rutherford backscattered ion (RBI) is a helium ions imaging mode, which backscatters helium ions from every element except hydrogen, with a backscatter yield that depends on the atomic number of the target. Energy-sensitive backscatter analysis is being developed, which when combined with RBI image information, supports elemental identification at helium ion nanometer resolution. This capability will enable distinguishing NPs from cell surface structures with nanometer resolution.

  11. Investigation of cellular interactions of nanoparticles by helium ion microscopy

    Science.gov (United States)

    Arey, B. W.; Shutthanandan, V.; Xie, Y.; Tolic, A.; Williams, N.; Orr, G.

    2011-06-01

    The helium ion microscope (HIM) probes light elements (e.g. C, N, O, P) with high contrast due to the large variation in secondary electron yield, which minimizes the necessity of specimen staining. A defining characteristic of HIM is its remarkable capability to neutralize charge by the implementation of an electron flood gun, which eliminates the need for coating non-conductive specimens for imaging at high resolution. In addition, the small convergence angle in HeIM offers a large depth of field (~5× FE-SEM), enabling tall structures to be viewed in focus within a single image. Taking advantage of these capabilities, we investigate the interactions of engineered nanoparticles (NPs) at the surface of alveolar type II epithelial cells grown at the airliquid interface (ALI). The increasing use of nanomaterials in a wide range of commercial applications has the potential to increase human exposure to these materials, but the impact of such exposure on human health is still unclear. One of the main routs of exposure is the respiratory tract, where alveolar epithelial cells present a vulnerable target at the interface with ambient air. Since the cellular interactions of NPs govern the cellular response and ultimately determine the impact on human health, our studies will help delineating relationships between particle properties and cellular interactions and response to better evaluate NP toxicity or biocompatibility. The Rutherford backscattered ion (RBI) is a helium ions imaging mode, which backscatters helium ions from every element except hydrogen, with a backscatter yield that depends on the atomic number of the target. Energy-sensitive backscatter analysis is being developed, which when combined with RBI image information, supports elemental identification at helium ion nanometer resolution. This capability will enable distinguishing NPs from cell surface structures with nanometer resolution.

  12. Helium and lead isotope geochemistry of the Azores Archipelago

    Science.gov (United States)

    Moreira, Manuel; Doucelance, Régis; Kurz, Mark D.; Dupré, Bernard; Allègre, Claude Jean

    1999-05-01

    New helium and lead isotopic data for basalts from the Azores archipelago (North Atlantic) show that the Azores have 4He/ 3He ratios both higher and lower than MORB values. Good covariations of helium and lead isotopes are observed at the scale of the archipelago, and suggest the coexistence of two mantle components in the Azores which are identified by data from São Miguel and Terceira. The eastern part of São Miguel island displays radiogenic helium ( 4He/ 3He > 140,000, R/ RaTerceira basalts contain relatively unradiogenic/primitive 4He/ 3He ratios, with a minimum value of 64,000 ( R/ Ra=11.3), and relatively high lead isotopic ratios ( 206Pb/ 204Pb = 20.02, 207Pb/ 204Pb = 15.64 and 208Pb/ 204Pb = 39.35). We propose that the Terceira source has a composition produced by a mixing between recycled oceanic crust (high 206Pb/ 204Pb) and entrained lower mantle (high 3He) material. The São Miguel island isotopic signature may be due to sampling of local (km-size) heterogeneity located at relatively shallow depth. The preferred origin of this heterogeneity is the Jurassic delamination of subcontinental lithosphere, which occurred during rifting and opening of the North Atlantic. The primitive helium ratios were also observed on the Mid Atlantic ridge at 38.5°N, reflecting plume-ridge interaction, whereas radiogenic ratios (>100,000) were observed at latitude higher than 40°N and may reflect the influence of the São Miguel component at the ridge.

  13. Helium-cooled nuclear reactor

    International Nuclear Information System (INIS)

    In helium cooled HTR's there is a by-pass circuit for cleaning purposes in addition to the main cooling circuit. This is to remove such impurities as hydrogen, methane, carbon monoxide and water from the coolant. In this system, part of the coolant successively flows first through an oxidation bed of copper oxide and an absorption bed of silica gel, then through activated charcoal or a molecular sieve. The hydrogen and carbon monoxide impurities are absorbed and the dry gas is returned to the main cooling circuit. To lower the hydrogen/water ratio without increasing the hydrogen fraction in the main cooling circuit, some of the hydrogen fraction converted into water is added to the cooling circuit. This is done, inter alia, by bypassing the water produced in the oxidation bed before it enters the absorption bed. The rest of the by-pass circuit, however, also includes an absorption bed with a molecular sieve. This absorbs the oxidized carbon monoxide fraction. In this way, such side effects as the formation of additional methane, carburization of the materials of the by-pass circuit or loss of graphite are avoided. (DG/RF)

  14. Photoionization rates for helium: update

    CERN Document Server

    Sokó?, Justyna M

    2014-01-01

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

  15. Helium and Neon in Comets

    Science.gov (United States)

    Jewitt, David

    1996-01-01

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

  16. Helium isotopes in lithospheric peridotites and eclogites

    Science.gov (United States)

    Day, J. M.; Hilton, D. R.; Halldorsson, S. A.; Pearson, G.; Taylor, L. A.

    2012-12-01

    Helium isotope ratios are sensitive tracers of mantle heterogeneity and demonstrate preservation and isolation of reservoirs in Earth's mantle since planetary accretion. Two important but poorly characterized reservoirs for He are subducted oceanic crust and cratonic continental lithosphere. Both of these reservoirs may play a direct role in the genesis of some intraplate lavas, and in the evolution of He in Earth's mantle. We report new He isotope data for Archaean and Proterozoic eclogites and cratonic peridotite xenoliths from South Africa, Siberia, and Canada. Eclogites from Roberts Victor are thought to come from recycled oceanic-crustal precursors. The He isotope ratios (0.05-0.41 RA, where RA is 3He/4He ratio relative to air) of garnet and clinopyroxene within a Roberts Victor eclogite xenolith are consistent with predicted He systematics of ancient recycled oceanic crust, implicating recycled oceanic crust with low time-integrated 3He/(U+Th); Garnets from a KAO eclogite have higher 3He/4He (4.7 RA). Archaean Kaapvaal cratonic peridotite minerals have low 3He/4He (0.01-0.06 RA), with olivines from Siberian cratonic peridotites exhibiting less radiogenic 3He/4He (2.7-3.8 RA). No differences in 3He/4He ratios are noted for high- and low-temperature peridotites. We also measured olivines from a Vitim garnet lherzolite from the Lake Baikal rift, which yielded 3He/4He of 9.6RA; this ratio is consistent with melt modification during shallowing of the lithosphere in this region during rifting and suggests infiltration by melts with high-3He/4He. The most recent estimate of 3He/4He of the continental lithospheric mantle is 6.1 ±0.9 RA [Gautheron & Moriera, EPSL, 2002], requiring a more radiogenic source than depleted upper mantle, and attributed to steady-state helium flux into the continents from the asthenosphere over 0.1 Ga time-scales. Using experiments with crushed olivine grains, from Archaean cratonic peridotites and Proterozoic non-cratonic peridotites, give means of 2.46 ±1.56 RA (n = 8) and 6.56 ±3.23 RA (n = 25) respectively; the average 3He/4He of non-cratonic peridotites is similar to melts considered to be derived from the lithosphere-asthenosphere boundary (6.17 ±1.41 RA, n = 103). The mean 3He/4He ratio of diamond inclusions (1.94 ±2.18 RA, 1.S.D., n = 38) is similar to the mean of olivines from Archaean cratonic peridotites. Thus, all cratonic continental mantle peridotites and eclogites measured to date exhibit more radiogenic 3He/4He than depleted upper mantle and can be modeled by closed-system evolution of helium. Previous workers, using a steady-state model for He in continental lithosphere, determined that modeled 3He fluxes were similar to those measured at mid-oceanic ridges (4 at/s/cm2), and were far greater than the average 3He flux measured on the continents (~0.1-0.4 at/s/cm2; Gautheron & Moriera, 2002). Our results show that the continental lithosphere may be heterogeneous with respect to He, according to lithospheric age, with bias toward modified samples that have interacted with mantle-derived melts. Our model indicates 3He fluxes for continental lithosphere of 0.25-0.4 at/s/cm2 and 2.5-4 at/s/cm2 for Archaean cratonic lithosphere and Archaean-Proterozoic non-cratonic lithosphere, respectively. This work was supported by grants from the NSF (EAR 1116089) and The San Diego Foundation (C-2011-00204).

  17. Accurate measurement of atmospheric helium isotopes.

    Science.gov (United States)

    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

  18. Rotationally induced dissipation in superfluid helium

    International Nuclear Information System (INIS)

    In an attempt to make a superfluid 4He analog of the radio-frequency superconducting quantum interference device (SQUID) that could be used as a gyroscope, we measured the critical velocity of the ac superflow through an orifice 5 ?m in radius. The orifice was supported by a septum placed inside a hollow torus filled with liquid helium. The superflow through the orifice was induced by rotating the whole torus. The torus was the inertial member of a high-quality-factor torsion pendulum forced to oscillate at its resonance frequency. The occurrence of dissipation was detected by analyzing the oscillator motion. The principle on which this device works is analyzed, and results are reported of experiments in which quite reproducible critical oscillation amplitudes---well accounted for by intrinsic vortex formation---were obtained. Depending on the value of the forcing torque, the critical behavior manifested itself either as the occurrence of sudden collapses of the oscillation amplitude or as a steady excess dissipation. The energy involved in the process was estimated. Temperature dependencies of the critical amplitude up to 2.115±0.003 K were measured. The results were found to be in agreement both with the ac data obtained with the Helmholtz-resonator technique and with the data obtained with dc flow measurements

  19. Rotationally induced dissipation in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bonaldi, M.; Vitale, S. (Dipartimento di Fisica, Universita degli Studi di Trento, I-38050 Povo, Trento (Italy) Gruppo di Trento, Istituto Nazionale di Fisica Nucleare, I-38050 Povo, Trento (Italy)); Cerdonio, M. (Laboratori Nazionali di Legnaro, Istituto Nazionale di Fisica Nucleare, I-35020 Legnaro, Padova (Italy))

    1990-12-01

    In an attempt to make a superfluid {sup 4}He analog of the radio-frequency superconducting quantum interference device (SQUID) that could be used as a gyroscope, we measured the critical velocity of the ac superflow through an orifice 5 {mu}m in radius. The orifice was supported by a septum placed inside a hollow torus filled with liquid helium. The superflow through the orifice was induced by rotating the whole torus. The torus was the inertial member of a high-quality-factor torsion pendulum forced to oscillate at its resonance frequency. The occurrence of dissipation was detected by analyzing the oscillator motion. The principle on which this device works is analyzed, and results are reported of experiments in which quite reproducible critical oscillation amplitudes---well accounted for by intrinsic vortex formation---were obtained. Depending on the value of the forcing torque, the critical behavior manifested itself either as the occurrence of sudden collapses of the oscillation amplitude or as a steady excess dissipation. The energy involved in the process was estimated. Temperature dependencies of the critical amplitude up to 2.115{plus minus}0.003 K were measured. The results were found to be in agreement both with the ac data obtained with the Helmholtz-resonator technique and with the data obtained with dc flow measurements.

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

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, Khris B.; Dresel, P Evan; Evans, John C.

    2001-10-31

    Seventy soil gas-sampling points were installed around the perimeter of the 618-11 Burial Ground, approximately 400 feet downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 3,100 feet. Soil gas samples were collected and analyzed for helium-3/helium-4 ratios from these 70 points. Helium-3/helium-4 ratios determined from the soil gas sampling points showed significant enrichments, relative to ambient air helium-3 concentrations. The highest concentrations were located along the northern perimeter of the burial ground. Helium-3/helium-4 ratios (normalized to the abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transect downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground. This vadose zone source is likely the source of tritium in the groundwater. The helium-3/helium-4 ratios also suggest the groundwater plume is traveling east-northeast from the burial ground and the highest groundwater tritium value may be to the north of well 699-13-3A. Finally, there appears to be no immediately upgradient sources of tritium impacting the burial ground since all the upgradient helium-3/helium-4 ratios are approximately 1.0.

  1. Helium diffraction from the GaAs(110) surface and the generation of helium-surface potentials

    International Nuclear Information System (INIS)

    A theoretical analysis of the helium diffraction experiments performed on the GaAs(110) surface by Cardillo, Becker, Sibener, and Miller is presented. Dynamic scattering calculations for several model potentials approximating that of the surface are presented. These suggest that the surface is a smoothly corrugated soft wall with a peak-to-trough distance along the [001] direction of approx.1 A and an attractive well depth of approx. 7 meV. Existing methods for generating van der Waals potentials are reviewed and an explanation is suggested for their poor performance in the case of helium. New semiempirical rules fit to the known helium rare-gas potentials and consistent with the recent results of Esjberg and Norskov are proposed. These are used to construct an approximate potential for GaAs(110), which we show to agree qualitatively with the empirically fit potential. The classical turning-point surface of this potential lies 3.5 A above the As nucleus. Scattering calculations performed on this potential are shown to agree poorly with experiment. We conclude from this that the scattering is very sensitive to nuances in the potential and that very accurate surface charge densities will be required before a potential capable of scattering in agreement with experiment can be constructed

  2. Parametric study on thermal efficiency of the helium turbine cycle with rotor cooling flow

    International Nuclear Information System (INIS)

    Thermal efficiency of a HTGR plant with helium turbine has been studied parametrically. The HTGR plant includes helium compressor, helium turbine, regenerative heat exchanger, precooler and intercooler. Small part of the outlet flow from the compressor is introduced into the high-temperature turbine rotor for cooling. With turbine inlet temperature, turbine pressure expansion ratio and cooling flow rate as parameters, thermal efficiencies were calculated numerically by computer code GASTUR-III. (1) In the regenerative cycle with turbine inlet temperature 10000C, the maximum thermal efficiencies are 46.2%, 45.6% and 45.1% for cooling flow rates 0%, 0.5% and 1% respectively. (2) In the intercooling regenerative cycle with turbine inlet temperature 10000C, the values are 48.5%, 48.0% and 47.5%. (3) With increase of the cooling flow, the thermal efficiency decreases almost linearly; 1% increase of the cooling flow results in 1% reduction of the thermal efficiency. (auth.)

  3. Helium and displacement damage produced by 600 MeV proton beams in high purity aluminum

    International Nuclear Information System (INIS)

    Pure aluminum samples (99.9999%) have been irradiated in the Proton Irradiation Experiment (PIREX) installed in the 600 MeV proton beam of the accelerator in the Swiss Nuclear Research Institute (SIN), at temperatures between 400K and 500K and displacement doses between 0.9 and 5 displacements per atom (dpa). Average displacement rate is 3.5 X 10-6 dpa/s. The specimens were analyzed for both 3He and 4He. Measured helium content is 215 atomic parts per million (appm)/dpa. No diffusional spreading of sodium or helium was measured. The helium bubble structure was examined and shows a swelling of 0.16% at about5 dpa

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

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

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

    2004-01-01

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

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

    International Nuclear Information System (INIS)

    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

  7. Application of gas chromatographic method in simultaneous measurements of helium, argon and neon concentration in groundwaters

    Science.gov (United States)

    Najman, J.; Bielewski, J.; Sliwka, I.

    2012-04-01

    Helium concentration in groundwater is a fine indicator in water dating in a range from a hundred to tens of thousands of years. Gas chromatography (GC) measurements of helium can be used as an alternative to mass spectrometry (MS) determinations of 4He for groundwater dating [1]. Argon and neon concentrations mainly serve for determining the temperature of recharge and the air excess which is needed to correct measured values of helium concentration [2] . A chromatographic measurement system of helium, argon and neon concentration in groundwater is presented [3]. Water samples are taken from groundwater with a precise procedure without contamination with air in a special stainless steel vessels of volume equal to 2900 cm3. Helium is extracted from water samples using the head-space method. After enrichment by cryotrap method helium is analyzed in the gas chromatograph equipped with the thermal conductivity detector (TCD) with detection limit of about 2.8 ng He. The helium limit of detection of presented method is 1,2·10-8 cm3STP/gH2O [4]. We are currently working on adapting the method of cryogenic enrichment of helium concentration for simultaneous measurements of the concentration of helium, argon and neon using single sample of groundwater. Neon will be measured with the thermal conductivity detector and capillary column filled with molecular sieve 5A. Argon will be analyzed also with the thermal conductivity detector and packed column filled with molecular sieve 5A. This work was supported by grant No. N N525 3488 38 from the polish National Science Centre. [1] A. Zuber, W. Ci??kowski, K. Ró?a?ski (red.), Tracer methods in hydrogeological studies - a methodological guide. Wroclaw University of Technology Publishing House, Wroclaw, 2007 (in polish). [2] P. Mochalski, Chromatographic method for the determination of Ar, Ne and N2 in water, Ph.D. thesis, Institute of Nuclear Physics Polish Academy of Sciences in Krakow, 2003 (in polish). [3] A. ?urek, P. Mochalski, Use of the gas chromatographic method for the denitrification process assessment in groundwater of the Triassic aquifer in Opole region (southern Poland), Geology, Quarterly, AGH, 36, z.1, 135-148, 2010 (in polish). [4] J. Najman, Development of chromatographic measurement method of helium concentration in groundwater for the purpose of dating in the hydrological issues, Ph.D. thesis, Institute of Nuclear Physics Polish Academy of Sciences in Krakow, 2008, http://www.ifj.edu.pl/SD/rozprawy_dr/rozpr_Najman.pdf?lang=pl(in polish).

  8. The influence of helium on the void swelling of a ferritic alloy irradiated in a HVEM

    International Nuclear Information System (INIS)

    Ferritic steels are possible candidate alloys for fusion reactors and therefore a study on the influence of a wide range of helium concentration levels on the void swelling of ferritic alloys has been performed. Specimens of the alloy DTO2 with composition Fe - 12.5 Cr - 4.73 Ti - 1.54 Mo - 1.36 O - 0.02 C - 0.03 N have been irradiated in the HVEM of the University of Antwerp (RUCA) at a dose rate of 5.5 x 10-3 dpa s-1. Previous to electron irradiation, specimens were doped with helium in the VEC or the University of Louvain-la-Neuve (UCL), at specimen temperatures ranging from 250 to 3500C. The following experiments have been performed. The influence of helium concentration on void swelling at 4500C, the influence of helium on the void swelling as a function of irradiation temperature and the influence of helium on the relation between swelling and irradiation doses. The results are presented and discussed. (Auth./C.F.)

  9. Quantum statistics and liquid helium 3 - helum 4 mixtures

    International Nuclear Information System (INIS)

    The behaviour of liquid helium 3-helium 4 mixtures is considered from the point of view of manifestation of quantum statistics effects in macrophysics. The Boze=Einstein statistics is shown to be of great importance for understanding superfluid helium-4 properties whereas the Fermi-Dirac statistics is of importance for understanding helium-3 properties. Without taking into consideration the interaction between the helium atoms it is impossible to understand the basic properties of liquid helium 33 - helium 4 mixtures at constant pressure. Proposed is a simple model of the liquid helium 3-helium 4 mixture, namely the binary mixture consisting of solid spheres of two types subjecting to the Fermi-Dirac and Bose-Einstein statistics relatively. This model predicts correctly the most surprising peculiarities of phase diagrams of concentration dependence on temperature for helium solutions. In particular, the helium 4 Bose-Einstein statistics is responsible for the phase lamination of helium solutions at low temperatures. It starts in the peculiar critical point. The helium 4 Fermi-Dirac statistics results in incomplete phase lamination close to the absolute zero temperatures, that permits operation of a powerful cooling facility, namely refrigerating machine on helium solution

  10. Helium turbo-expander with an alternator: Large helium refrigerator-liquefier system

    Science.gov (United States)

    Akiyama, Y.

    1980-07-01

    The requirements for practical use of the large scale helium refrigerator system are considered. As a long continuous operation is required, the life time of the system should be approximately as long as that of other electrical machines. The refrigerator should be connected directly to the superconducting system by circulation of coolant (liquid or gaseous helium). In this case, an accident of the refrigerator system causes a fatal breakdown of the full system. The contamination in the circulating helium should be avoided. The efficiency of the refrigerator system should be as high as possible. The control method must be established so that the refrigerator can be operated for a long period by a few operators. A helium turbo-expander with externally pressurized helium gas bearings at the temperature of liquid nitrogen and an alternator as a brake was employed for the investigation.

  11. Partial discharges in lapped polymer taped insulation impregnated with supercritical helium

    International Nuclear Information System (INIS)

    Apparatus has been designed and constructed to evaluate the high-voltage parameters of lapped cable models impregnated with supercritical helium for pressures up to 1.5 MPa and for temperatures to 4.2K. The tape materials studied are as follows: high-density polythene, Valeron (cross-laminated polythene film), polypropylene, Nylon 11 and polysulphone with limited tests using polycarbonate. The variation of the maximum value of discharge with applied alternating voltage was obtained, and also the variation of inception stress (1 pC and 5 pC) with helium density and pressure. (author)

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

    International Nuclear Information System (INIS)

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

  13. Cryogenic neutron detector comprising an InSb semiconductor detector and a supercritical helium-3 gas converter

    International Nuclear Information System (INIS)

    We evaluated the neutron-detection characteristics of a proposed cryogenic neutron detector comprising an InSb semiconductor detector and a helium-3 gas converter. The neutron detector was operated at 4.2 K with helium-3 gas filling up to 1.5 atm, at which the density of the helium-3 nucleus corresponds to that at 160 atm at room temperature. The secondary particles generated by the 3He(n,p)T reaction were successfully detected by the InSb detector with a time response of ?80 ns at all tested gas pressures

  14. Helium turbine power generation in high temperature gas reactor

    International Nuclear Information System (INIS)

    This paper presents studies on the helium turbine power generator and important components in the indirect cycle of high temperature helium cooled reactor with multi-purpose use of exhaust thermal energy from the turbine. The features of this paper are, firstly the reliable estimation of adiabatic efficiencies of turbine and compressor, secondly the introduction of heat transfer enhancement by use of the surface radiative heat flux from the thin metal plates installed in the hot helium and between the heat transfer coil rows of IHX and RHX, thirdly the use of turbine exhaust heat to produce fresh water from seawater for domestic, agricultural and marine fields, forthly a proposal of plutonium oxide fuel without a slight possibility of diversion of plutonium for nuclear weapon production and finally the investigation of GT-HTGR of large output such as 500 MWe. The study of performance of GT-HTGR reduces the result that for the reactor of 450 MWt the optimum thermal efficiency is about 43% when the turbine expansion ratio is 3.9 for the turbine efficiency of 0.92 and compressor efficiency of 0.88 and the helium temperature at the compressor inlet is 45degC. The produced amount of fresh water is about 8640 ton/day. It is made clear that about 90% of the reactor thermal output is totally used for the electric power generation in the turbine and for the multi-puposed utilization of the heat from the turbine exhaust gas and compressed helium cooling seawater. The GT-Large HTGR is realized by the separation of the pressure and temperature boundaries of the pressure vessel, the increase of burning density of the fuel by 1.4 times, the extention of the nuclear core diameter and length by 1.2 times, respectively, and the enhancement of the heat flux along the nuclear fuel compact surface by 1.5 times by providing riblets with the peak in the flow direction. (J.P.N.)

  15. Development of charcoal sorbents for helium cryopumping

    International Nuclear Information System (INIS)

    High vacuum adsorption of helium on activated charcoal at liquid helium temperatures has demonstrated the high specific pumping speeds needed for fusion power systems. However, this method of cryopumping has not been optimized. This paper describes the results of a program to evaluate the effects of different grades of charcoal as well as the effects of various charcoal bonding methods on helium pumping speed and capacity. Coal- and coconut-based charcoals were evaluated using various attachment techniques such as brazing, refractory ceramic adhesives and mechanical retention. Results suggest that both charcoal particle size and grade had a strong effect on pumping speed and capacity. Coconut-based charcoals appear to give superior overall characteristics compared to coal-based charcoals, while smaller particles give higher pumping speeds. Various bonding media and attachment methods have a measurable effect on helium pumping characteristics suggesting that thermal conductivity of the bond and good contact with the charcoal are key parameters. Additional test data show the results of pumping mixtures of helium and deuterium

  16. Imaging the Photodynamics of Doped Helium Droplets

    Science.gov (United States)

    Drabbels, Marcel

    2006-03-01

    During the last decade helium nanodroplets have been established as an ideal spectroscopic matrix. Helium droplets are also thought to be ideal low temperature nanoreactors because of their ability to stabilize weakly bound species. As the focus is nowadays shifting to the study of chemical reactions in liquid helium droplets, question related to the energy relaxation and solvation dynamics become more and more prominent. To address these questions experiments have been performed in with species with a well defined kinetic energy distribution have been created via the photodissociation molecules residing inside helium droplets. The velocity distributions of the photofragments that have escaped from the droplets have been determined using ion imaging techniques. The analysis of speed distributions as function of droplet size and precursor has enabled to obtain a consistent picture of the mechanisms underlying the translational motion of these non-thermal species through this quantum liquid. Additional information on the solvation dynamics could be obtained by using non-resonant ionization techniques in these experiments. More recently the translational dynamics of quasi-free electrons in helium droplets has been investigated by means of photoelectron spectroscopy. The results on these experiments indicate that the relaxation of the electrons is governed by the same mechanism responsible for the kinetic energy relaxation of non-thermal neutral molecules.

  17. Liquid helium and the dilution refrigerator

    International Nuclear Information System (INIS)

    Anomalies occure in the density and specific heat of helium at a very low temperature. Below the Lambda-transition temperature helium is a superfluid. Liquid helium also has enormous thermal conductivity. If two vessels containing superfluid helium are connected through a narrow capillary then a temperature difference gives rise to a corresponding pressure difference. 4He obeys Bose-Einstein statistics and 3He obeys Fermi-Dirac statistics. The operation of the helium refrigerator depends on a naturally occuring isotopic separation of a mixture of 4He and 3He below 1 Kelvin. At this temperature 3He can expand by being diluted with 4He. When mixtures containing more than 6% 3He are cooled below 0.86 Kelvin they separate out into a lighter quasi-liquid 3He rich phase floating on top of a denser quasi-gas 4He rich phase. The 4He in the lower phase is almost entirely superfluid with zero entropy and viscosity functioning as a background matrix through which the 3He moves. There is a latent heat of transition as 3He passes from the upper to the lower phase to produce a cooling similar to a liquid cooled by evaporation

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Effect of helium on fatigue crack growth and life of reduced activation ferritic/martensitic steel

    International Nuclear Information System (INIS)

    The effects of helium on the fatigue life, micro-crack growth behavior up to final fatigue failure, and fracture mode under fatigue in the reduced activation ferritic/martensitic steel, F82H IEA-heat, were investigated by low cycle fatigue tests at room temperature in air at a total strain range of 0.6–1.5%. Significant reduction of the fatigue life due to helium implantation was observed for a total strain range of 1.0–1.5%, which might be attributable to an increase in the micro-crack propagation rate. However, the reduction of fatigue life due to helium implantation was not significant for a total strain range of 0.6–0.8%. A brittle fracture surface (an original point of micro-crack initiation) and a cleavage fracture surface were observed in the helium-implanted region of fracture surface. A striation pattern was observed in the non-implanted region. These fracture modes of the helium-implanted specimen were independent of the strain range

  20. Effect of helium on fatigue crack growth and life of reduced activation ferritic/martensitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan); Takahashi, Manabu, E-mail: takahashi.manabu@jupiter.qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan); Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan); Yamazaki, Masanori, E-mail: m-yamaza@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research, Tohoku University, 2145-2, Narita-cyo, Oarai, Ibaraki 311-1313 (Japan)

    2013-11-15

    The effects of helium on the fatigue life, micro-crack growth behavior up to final fatigue failure, and fracture mode under fatigue in the reduced activation ferritic/martensitic steel, F82H IEA-heat, were investigated by low cycle fatigue tests at room temperature in air at a total strain range of 0.6–1.5%. Significant reduction of the fatigue life due to helium implantation was observed for a total strain range of 1.0–1.5%, which might be attributable to an increase in the micro-crack propagation rate. However, the reduction of fatigue life due to helium implantation was not significant for a total strain range of 0.6–0.8%. A brittle fracture surface (an original point of micro-crack initiation) and a cleavage fracture surface were observed in the helium-implanted region of fracture surface. A striation pattern was observed in the non-implanted region. These fracture modes of the helium-implanted specimen were independent of the strain range.

  1. Helium-neon laser irradiation stimulates migration and proliferation in melanocytes and induces repigmentation in segmental-type vitiligo.

    Science.gov (United States)

    Yu, Hsin-Su; Wu, Chieh-Shan; Yu, Chia-Li; Kao, Ying-Hsien; Chiou, Min-Hsi

    2003-01-01

    Low-energy helium-neon lasers (632.8 nm) have been employed in a variety of clinical treatments including vitiligo management. Light-mediated reaction to low-energy laser irradiation is referred to as biostimulation rather than a thermal effect. This study sought to determine the theoretical basis and clinical evidence for the effectiveness of helium-neon lasers in treating vitiligo. Cultured keratinocytes and fibroblasts were irradiated with 0.5-1.5 J per cm2 helium-neon laser radiation. The effects of the helium-neon laser on melanocyte growth and proliferation were investigated. The results of this in vitro study revealed a significant increase in basic fibroblast growth factor release from both keratinocytes and fibroblasts and a significant increase in nerve growth factor release from keratinocytes. Medium from helium-neon laser irradiated keratinocytes stimulated [3H]thymidine uptake and proliferation of cultured melanocytes. Furthermore, melanocyte migration was enhanced either directly by helium-neon laser irradiation or indirectly by the medium derived from helium-neon laser treated keratinocytes. Thirty patients with segmental-type vitiligo on the head and/or neck were enrolled in this study. Helium-neon laser light was administered locally at 3.0 J per cm2 with point stimulation once or twice weekly. The percentage of repigmented area was used for clinical evaluation of effectiveness. After an average of 16 treatment sessions, initial repigmentation was noticed. Marked repigmentation (>50%) was observed in 60% of patients with successive treatments. Basic fibroblast growth factor is a putative melanocyte growth factor, whereas nerve growth factor is a paracrine factor for melanocyte survival in the skin. Both nerve growth factor and basic fibroblast growth factor stimulate melanocyte migration. It is reasonable to propose that helium-neon laser irradiation clearly stimulates melanocyte migration and proliferation and mitogen release for melanocyte growth and may also rescue damaged melanocytes, therefore providing a microenvironment for inducing repigmentation in vitiligo. PMID:12535198

  2. "Eclipse" effect in the scattering of weakly bound helium clusters.

    Science.gov (United States)

    Kalinin, Anton; Kornilov, Oleg; Rusin, Lev; Toennies, J Peter; Vladimirov, George

    2004-10-15

    The total cross sections of the helium dimer, trimer, and tetramer for scattering from Kr atoms have been measured for cluster beam velocities between 250 and 820 m/s. The dimer cross section is twice that of the atom within 5% indicating that the Kr atoms scatter from the He atoms independently, which is consistent with the large dimer bond distance of about 50 A. The trimer and tetramer cross sections are somewhat larger and can be described by an impulse approximation with a multiple "eclipse" correction, extending ideas of Glauber for high energy collisions with the deuteron. PMID:15524987

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

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

  4. Settling of helium and the ages of the globular clusters

    International Nuclear Information System (INIS)

    Model low-mass globular-cluster stars were evolved with their helium allowed to diffuse under the influence of gravity, thermal diffusion, and concentration gradient. The evolution tended to speed up. Also, the turnoff point moved toward lower luminosity and slightly lower surface temperature. If the luminosity at turnoff is used as the sole criterion for determining the age of a globular cluster, the inferred ages of such clusters are reduced by about 22% from starting values in the vicinity of 1.5 x 1010 yr

  5. Primitive helium and neon isotopes in Terceira island (Azores archipelago)

    OpenAIRE

    Madureira, Pedro; Moreira, P.; Mata, M.; J Alle?gre, C. J.

    2005-01-01

    We present the first neon data, as well as new helium data, on Terceira Island (Azores archipelago, Portugal). Clear 20Ne and 21Ne excesses compared to air are observed (20Ne/22Ne > 11.2) and moreover, the samples show a more primitive 21Ne/22Ne ratio than MORB, confirming that the Azores hotspot can be considered as sampling a “primitive”, relatively undegassed, reservoir. Most 4He/3He isotopic ratios range between 80,000 and 63,500 (not, vert, similar 9 to 11.5 R/Ra), being similar to t...

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

    International Nuclear Information System (INIS)

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

  7. Subtask 12G1: Effects of dynamically charged helium on swelling and microstructure of vanadium-base alloys

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-03-01

    The objective of this work is to determine void structure, distribution, and density changes of several vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). 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{degrees}C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible. For specimens irradiated to {approx}18-31 dpa at 500-600{degrees}C 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 {approx}31 dpa at 425{degrees}C, when helium was generated at a rate of 0.4-0.8 appm helium/dpa, were diffuse helium bubbles observed in limited regions of grain matrices and near {approx}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{degrees}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 Ti{sub 5}Si{sub 3} was observed for DHCE at >500{degrees}C but not at 425{degrees}C.

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

    International Nuclear Information System (INIS)

    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)

  9. Thermal-hydraulic characteristics inside in-core structure test section (T2) of helium engineering demonstration loop (HENDEL) under loss of forced circulation condition

    International Nuclear Information System (INIS)

    As the results of experimental and analytical works using T2 test section in HENDEL, the thermal and hydraulic characteristics inside the pressure vessel under loss of forced circulation condition are summarized as follows, (1) Temperatures of side shielding blocks and metallic structures such as a pressure vessel, core restraint mechanism reach their peak temperatures at 15-40 hours after the starting time of natural convection. The temperature transients of components agree with analytical results, comparatively. (2) Pressure difference between cold and hot helium gas becomes close to zero in 6 minutes after the starting time of natural convection due to the leakage flow of helium gas through the graphite blocks. The exchange of hot and cold helium gas through the leakage paths in the CBS graphite blocks are predicted by analytical results. (3) Helium gas pressure decreases after the starting point of natural convection. The reason is considered that hot helium gas is cooled down in the hot gas ducts, helium gas coolers and a helium gas heater with water jacket between T2 test section and the closed valves of M+A sections in HENDEL. (4) Initial temperatures of the CBS graphite components depend on helium gas pressure because leakage flow of cold helium gas through the CBS increases with helium gas pressure. (5) The elapsed times which temperatures of pressure vessel reach peak temperatures become shorter and the peak temperature decreases as her and the peak temperature decreases as helium gas pressure is higher. The reason is considered that natural convection becomes stronger and the heat transfer coefficients on the CBS and pressure vessel increase as helium gas pressure increases under the natural convection conditions. (author)

  10. Primary neutral helium in the heliosphere

    CERN Document Server

    Mueller, Hans-Reinhard

    2012-01-01

    Two years of neutral measurements by IBEX-Lo have yielded several direct observations of interstellar neutral helium and oxygen during preferred viewing seasons. Besides the interstellar signal, there are indications of the presence of secondary neutral helium and oxygen created in the heliosphere. Detailed modeling of these particle species is necessary to connect the measured fluxes to the pristine local interstellar medium while accounting for loss and production of neutral particles during their path through the heliosphere. In this contribution, global heliosphere models are coupled to analytic calculations of neutral trajectories to obtain detailed estimates of the neutral distribution function of primary interstellar helium atoms in the heliosphere, in particular in the inner heliosphere.

  11. Electron Diffraction of Superfluid Helium Droplets

    Science.gov (United States)

    2014-01-01

    We present experimental results of electron diffraction of superfluid helium droplets and droplets doped with phthalocyanine gallium chloride and discuss the possibility of performing the same experiment with a laser aligned sample. The diffraction profile of pure droplets demonstrates dependence on the nozzle temperature, that is, on the average size of the droplets. Larger clusters demonstrate faster decay with increasing momentum transfer, whereas smaller clusters converge to isolated gas phase molecules at source temperatures of 18 K and higher. Electron diffraction of doped droplets shows similar modified molecular scattering intensity as that of the corresponding gas phase molecules. On the basis of fittings of the scattering profile, the number of remaining helium atoms of the doped droplets is estimated to be on the order of hundreds. This result offers guidance in assessing the possibility of electron diffraction from laser aligned molecules doped in superfluid helium droplets. PMID:24920997

  12. Simulating the tevatron liquid helium satellite refrigerators

    International Nuclear Information System (INIS)

    A computer program to simulate the Fermilab Tevatron liquid helium satellite refrigeration system has been developed. The simulator program takes advantage of the Macintosh platform upon which it was developed to produce a unique, easy to use Macintosh interface to facilitate ease of cycle design and modification. The user can drag icons representing refrigerator components around on the screen and piece them together to form a variety of liquid helium refrigeration cycle configurations. Extensive use of the icons, windows, and pull-down menus of the Macintosh interface allows the user to easily alter refrigeration component configurations and parameters. Calculation accuracy is retained by using existing helium property subroutines and component models. The user interface, program output, and code details are described. Sample configurations and results are presented

  13. Metastable helium density probe for remote plasmas

    International Nuclear Information System (INIS)

    Helium metastable atom density was spatially determined by a modified electrostatic probe in a remote plasma. The probe structure was similar to that of a guard ring probe. Opposite polarity voltages were applied to the inner probe and the guard ring to shield both electrons and ions from the vicinity of the inner probe. Therefore, the inner probe current is due to secondary electrons generated by the de-exciting helium metastable atom flux. The photoelectron current was removed by shielding and orienting the probe 90 deg. to the direction of the plasma-generated photon flux. Helium metastable atom density on the order of 107 cm-3 was measured. Limitations on the use of this technique are revealed by comparisons with simulated metastable distributions.

  14. Helium corona-assisted air discharge

    International Nuclear Information System (INIS)

    Operation of atmospheric discharge of electronegative gases including air at low voltages yet without consuming any inert gas will enormously promote the application of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium-filled glass bulb--for a needle-plate distance of 12 mm, 1.0 kV suffices. Ultraviolet emission from helium corona facilitates the discharging of air, and the discharge current manifests distinct features such as relatively broad Trichel pulses in both half periods. This design allows safe and economic implementation of atmospheric discharge of electronegative gases, which will find a broad palette of applications in surface modification, plasma medicine and gas treatment, etc.

  15. Helium desorption from a tungsten single crystal

    International Nuclear Information System (INIS)

    Entrapment of helium in molybdenum and tungsten has been investigated both theoretically and experimentally in detail in the past. In general, peaks observed in the thermal desorption spectra of helium are related to the detrapping reactions of helium from Hesub(n)V (n = 1 to 4) complexes. A computer programme is developed to simulate the activation energies of these detrapping reactions in the bulk of the solid and in the vicinity of the crystal surface. Experimental values of the activation energies of these reactions reported earlier by Kornelsen show good agreement with the values calculated for the same reactions occurring in the bulk. Values calculated for these reactions near the surface are much lower than the experimental values. It is further shown that an agreement between the experimental and the calculated values of activation energies for the surface reactions is possible only if the entrapment is made to occur near the surface. (author)

  16. Helium generation cross sections for fast neutrons

    International Nuclear Information System (INIS)

    Fast-neutron-induced total helium production cross sections are an important source of information for the development of materials for fusion reactors. These cross sections are presently being measured at Rockwell International, with the measurements based on high-sensitivity gas mass spectrometry. Cross sections are given for helium production in Al, Ti, Cr, Fe, Ni, Cu, Au, and the separated isotopes of Ni and Cu, for approx. 14.8-MeV neutrons from the T(d,n) reaction. A detailed fluence mapping of the irradiation volume was required to relate helium generation measurements to cross sections. The importance of comprehensive passive dosimetry in all fast-neutron irradiation experiments is emphasized. 4 figures, 1 table

  17. Catching proteins in liquid helium droplets

    CERN Document Server

    Kupser, Peter; Meijer, Gerard; von Helden, Gert

    2010-01-01

    An experimental approach is presented that allows for the incorporation of large mass/charge selected ions in liquid helium droplets. It is demonstrated that droplets can be efficiently doped with a mass/charge selected amino acid as well as with the much bigger m$\\approx$12 000 amu protein Cytochrome C in selected charge states. The sizes of the ion-doped droplets are determined via electrostatic deflection. Under the experimental conditions employed, the observed droplet sizes are very large and range, dependent on the incorporated ion, from 10$^{10}$ helium atoms for protonated Phenylalanine to 10$^{12}$ helium atoms for Cytochrome C. As a possible explanation, a simple model based on the size- and internal energy-dependence of the pickup efficiency is given.

  18. Helium Speech: An Application of Standing Waves

    Science.gov (United States)

    Wentworth, Christopher D.

    2011-04-01

    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 phenomenon requires that we distinguish between the frequencies of sound produced by the larynx and the filtering of those frequencies by the vocal tract. We will describe here an experiment done by introductory physics students that uses helium speech as a context for learning about the human vocal system and as an application of the standing sound-wave concept. Modern acoustic analysis software easily obtained by instructors for student use allows data to be obtained and analyzed quickly.

  19. Precision spectroscopy of Kaonic helium-3 and helium-4 3d?2p X-rays

    International Nuclear Information System (INIS)

    Recently, the shift of the kaonic helium-4 2p state was precisely determined by the E570 and SIDDHARTA experiments. Prior to the experiment by E570, the average of three earlier experimental results showed -43±8 eV,while most of the theoretical calculations give ?0 eV. This five-sigma discrepancy between theory and experiment was known as the 'kaonic helium puzzle'. A recent theoretical model showed a possible resonance-like shift of maximum 10 eV for a certain value of a deep antikaon-nucleon interaction potential, which is different in helium 3 and helium 4.The E570 experiment determined the shift of the kaonic helium-4 2p state as +2±2 (stat)±2 (sys) eV in 2007. The SIDDHARTA experiment determined the shift as 0±6(stat)±2(sys) eV in 2009. The results of these experiments resolved the long-standing puzzle. A new experiment of the kaonic helium-3 X-ray measurement is being prepared by the J-PARC E17 collaborators, and the kaonic helium-3 X-ray data taken very recently by the SIDDHARTA experiment are on the way to be analyzed. The results of the E570, E17 and SIDDHARTA experiments examine the strong interaction for light nuclei with different isospin, and test furthermore recent theoretical predictions.

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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 correct 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.

  2. Observations of energetic helium ions in the Earth's radiation belts during a sequence of geomagnetic storms

    International Nuclear Information System (INIS)

    Every year a significant number of magnetic storms disturb the earth's magnetosphere and the trapped particle populations. In this paper, we present observations of energetic (MeV) helium ions made with Explorer 45 during a sequence of magnetic storms during June through December of 1972. The first of these storms started on June 17 and had a Dst index excursion to approx.190 gamma, and the MeV helium ions were perturbed primarily beyond 3 earth radii in the equatorial radiation belts with a typical flux increase of an order of magnitude at L = 4. The second storm period took place during August and was associated with very major solar flare activity. Although the Dst extremum was at best 35 gamma less than the June storm, this period can be characterized as irregular (or multi-storm) with strong compression of the magnetosphere and very large (order of magnitude) MeV helium ion flux enhancements down to Lapprox.2. Following this injection the trapped helium ion fluxes showed positive spectral slope with the peak beyond 3.15 MeV at L = 2.5; and at the lowest observable L shells (Lapprox.2--3) little flux decay (tau>100 days) was seen during the rest of the year. Any effects of two subsequent major magnetic storms in September and November were essentially undetectable in the prolonged after-effect of the August solar flare associated MeV helium ion injection. The helium ion radial profile of the phase space density showed a significant negative slope during this periognificant negative slope during this period, and we infer that radial diffusion constitutes a significant loss of helium ions on L shells above Lapprox. =4 during the aftermath of the August 1972 magnetic storm

  3. Helium damage in austenitic stainless steels

    International Nuclear Information System (INIS)

    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

  4. Helium burning in moderate-mass stars

    CERN Document Server

    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.

  5. Experiments with single electrons in liquid helium

    International Nuclear Information System (INIS)

    We describe experiments we have performed in which we are able to image the motion of individual electrons moving in liquid helium 4. Electrons in helium form bubbles of radius ?19 A. We use the negative pressure produced by a sound wave to expand these bubbles to a radius of about 10 ?m. The bubbles are then illuminated with light from a flash lamp and their position recorded. We report on several interesting phenomena that have been observed in these experiments. It appears that the majority of the electrons that we detect result from cosmic rays passing through the experimental cell. We discuss this mechanism for electron production

  6. Excited state positronium collisions with helium

    Energy Technology Data Exchange (ETDEWEB)

    Starrett, C. [Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast BT7 1NN (United Kingdom)], E-mail: c.starrett@qub.ac.uk; Walters, H.R.J. [Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); McAlinden, Mary T. [School of Computing and Mathematical Sciences, Oxford Brookes University, Wheatley Campus, Oxford OX33 1HX (United Kingdom)

    2008-02-15

    Calculations of the discrete positronium (Ps) transition Ps(2s) {yields} Ps(2p) in collisions with ground state helium are reported. Results are presented at total and single differential levels. Calculations are made within the first born approximation (FBA). The Hartley-Walters approximation is used to sum over all possible final excited atom states. In addition, impulse approximation (IA) calculations are reported for Ps(2s) and Ps(2p) fragmentation collisions with ground state helium, where the atom does not change state. Again, the FBA with the HWA is used to account for collisions in which the atom is excited or ionized.

  7. Excited state positronium collisions with helium

    International Nuclear Information System (INIS)

    Calculations of the discrete positronium (Ps) transition Ps(2s) ? Ps(2p) in collisions with ground state helium are reported. Results are presented at total and single differential levels. Calculations are made within the first born approximation (FBA). The Hartley-Walters approximation is used to sum over all possible final excited atom states. In addition, impulse approximation (IA) calculations are reported for Ps(2s) and Ps(2p) fragmentation collisions with ground state helium, where the atom does not change state. Again, the FBA with the HWA is used to account for collisions in which the atom is excited or ionized

  8. Detection of solar neutrinos in superfluid helium

    International Nuclear Information System (INIS)

    A new method for detecting solar neutrinos and other weakly interacting particles is proposed and described. The detector consists of a large mass of superfluid helium at low temperatures (20 mK). When a neutrino is scattered off an electron, the recoil energy of the electron (10/sup -6/ to 10/sup -7/ erg) is deposited in the helium. This small amount of energy can be detected because of the unusual kinetics of rotons at low temperatures. It should be possible to construct a detector of sufficiently low background and large size to measure solar neutrino spectra

  9. Helium damage in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Caskey, G.R. Jr.; Mezzanotte, D.A. Jr.; Rawl, D.E. Jr.

    1983-01-01

    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.

  10. Helium mobility in advanced nuclear ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, S., E-mail: shradha.agarwal@cea.fr [CEA/DEN/Service de Recherches de Métallurgie Physique, Laboratoire JANNUS (France); Trocellier, P.; Serruys, Y. [CEA/DEN/Service de Recherches de Métallurgie Physique, Laboratoire JANNUS (France); Vaubaillon, S. [CEA/DEN/Service de Recherches de Métallurgie Physique, Laboratoire JANNUS (France); CEA-INSTN/UEPTN, Centre d’Etudes de Saclay, F-91191 Gif sur Yvette (France); Miro, S. [CEA/DEN/Service de Recherches de Métallurgie Physique, Laboratoire JANNUS (France)

    2014-05-01

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

  11. Helium mobility in advanced nuclear ceramics

    International Nuclear Information System (INIS)

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

  12. Photoassociation of cold metastable helium atoms

    OpenAIRE

    Woestenenk, G. R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to trap 106 atoms in our magneto-optical trap. The helium atoms are in a metastable state, the He 23S1 state, which has a lifetime of more than 2 hours. With cold atoms phenom...

  13. Properties of hydrogen/helium accretion plasmas

    International Nuclear Information System (INIS)

    We study the properties of impulsively-heated plasmas initially composed of hydrogen and helium. We follow the time-dependent behavior of the ion and electron temperatures, the pair density, and the densities of hydrogen, helium, and nuclei formed in fusion and breakup reactions. We also consider neutron production and escape, and calculate the 0.431 and 0.478 MeV line luminosities from ?-? fusion reactions, and the 2.22 MeV line luminosity from neutron capture on protons. 13 refs., 3 figs., 1 tab

  14. Density functional theory study on helium behavior in aluminum

    International Nuclear Information System (INIS)

    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)

  15. Helium generation and its effect on BWR fuel rods

    International Nuclear Information System (INIS)

    It was reported that a significant amount of helium is produced in the fuel pellets by ternary fission and alpha decay of transuranic elements. Some of the generated helium atoms are released from the fuel pellets to the gap and plenum region. The released helium atoms will improve the gap conductance and thus reduce fission gas release of the fuel rods. This phenomenon is especially prominent in high burnup BWR fuel rods. The purpose of this paper is to (1) present the helium release data from high burnup BWR rods, (2) predict the amount of helium generation by a lattice physics code and correlate the helium release with the generation amount, (3) evaluate the accuracy of the predicted helium generation by comparing with experimentally measured values, (4) evaluate the effect of helium release on fuel performance by using the formulae described in this paper. (author)

  16. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    International Nuclear Information System (INIS)

    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 helium–titanium 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)

  17. On the problem of thallium 201 production under irradiation of a thallium target by helium 3 ions

    International Nuclear Information System (INIS)

    The problem of thallium-201 production as a result of irradiation by ?60 MeV helium-3 ions of thallium-203, 204 isotopes is discussed. Energy ranges of irradiation of thallium-203, 205 isotopes by helium-3 ions are determined, taking into account requirements VFS 42-1325-83 to radionuclide impurities in preparation: for targets enriched by thallium-203 they constitute 37.5-48.0 MeV, for targets enriched by thallium-205 - 48-60 MeV

  18. Energy spectra of finite temperature superfluid helium-4 turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Kivotides, Demosthenes [Department of Aeronautics, Imperial College London, London SW7 2AZ (United Kingdom)

    2014-10-15

    A mesoscopic model of finite temperature superfluid helium-4 based on coupled Langevin-Navier-Stokes dynamics is proposed. Drawing upon scaling arguments and available numerical results, a numerical method for designing well resolved, mesoscopic calculations of finite temperature superfluid turbulence is developed. The application of model and numerical method to the problem of fully developed turbulence decay in helium II, indicates that the spectral structure of normal-fluid and superfluid turbulence is significantly more complex than that of turbulence in simple-fluids. Analysis based on a forced flow of helium-4 at 1.3 K, where viscous dissipation in the normal-fluid is compensated by the Lundgren force, indicate three scaling regimes in the normal-fluid, that include the inertial, low wavenumber, Kolmogorov k{sup ?5/3} regime, a sub-turbulence, low Reynolds number, fluctuating k{sup ?2.2} regime, and an intermediate, viscous k{sup ?6} range that connects the two. The k{sup ?2.2} regime is due to normal-fluid forcing by superfluid vortices at high wavenumbers. There are also three scaling regimes in the superfluid, that include a k{sup ?3} range that corresponds to the growth of superfluid vortex instabilities due to mutual-friction action, and an adjacent, low wavenumber, k{sup ?5/3} regime that emerges during the termination of this growth, as superfluid vortices agglomerate between intense normal-fluid vorticity regions, and weakly polarized bundles are formed. There is also evidence of a high wavenumber k{sup ?1} range that corresponds to the probing of individual-vortex velocity fields. The Kelvin waves cascade (the main dynamical effect in zero temperature superfluids) appears to be damped at the intervortex space scale.

  19. Energy spectra of finite temperature superfluid helium-4 turbulence

    International Nuclear Information System (INIS)

    A mesoscopic model of finite temperature superfluid helium-4 based on coupled Langevin-Navier-Stokes dynamics is proposed. Drawing upon scaling arguments and available numerical results, a numerical method for designing well resolved, mesoscopic calculations of finite temperature superfluid turbulence is developed. The application of model and numerical method to the problem of fully developed turbulence decay in helium II, indicates that the spectral structure of normal-fluid and superfluid turbulence is significantly more complex than that of turbulence in simple-fluids. Analysis based on a forced flow of helium-4 at 1.3 K, where viscous dissipation in the normal-fluid is compensated by the Lundgren force, indicate three scaling regimes in the normal-fluid, that include the inertial, low wavenumber, Kolmogorov k?5/3 regime, a sub-turbulence, low Reynolds number, fluctuating k?2.2 regime, and an intermediate, viscous k?6 range that connects the two. The k?2.2 regime is due to normal-fluid forcing by superfluid vortices at high wavenumbers. There are also three scaling regimes in the superfluid, that include a k?3 range that corresponds to the growth of superfluid vortex instabilities due to mutual-friction action, and an adjacent, low wavenumber, k?5/3 regime that emerges during the termination of this growth, as superfluid vortices agglomerate between intense normal-fluid vorticity regions, and weakly polarized bundles are formed. There is also evidence of a high wavenumber k?1 range that corresponds to the probing of individual-vortex velocity fields. The Kelvin waves cascade (the main dynamical effect in zero temperature superfluids) appears to be damped at the intervortex space scale

  20. Boron diffusion in presence of defects induced by helium implantation

    International Nuclear Information System (INIS)

    Among numerous metallic impurities gettering techniques, helium implantation that leads to the formation of both defect types (interstitial and vacancy type) has been investigated. The gettering efficiency has been demonstrated for metals like Au, Ni, Cu or Fe. Moreover, dopant gettering has also been observed on these defects. Boron is of particular interest for the realisation of ultra-shallow junctions. Its interactions with interstitial type defects are widely studied in the literature. In this paper, we will focus our attention on boron diffusion in presence of He induced defects. The boron diffusion, known to be driven by interstitial mechanism, can be largely affected by the presence of cavities, which are sinks for interstitials. In this work, n-type Si wafers doped at 1 x 1014 B cm-3 were implanted with helium for various doses 1-5 x 1016 He+ cm-2 and energies 40-100 keV. Boron implantation was then performed at 5 keV for a dose of 2 x 1013 B cm-2. Secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM), spreading resistance profilometry and simulation with PROMIS 1.5 code were used in order to study the defect band impact on boron diffusivity and electrical activity after classical thermal treatments. The impact of various parameters on boron diffusivity, such as defect density, distance between boron profile and defect band or annealing temperature isnd defect band or annealing temperature is discussed in this work