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

    Science.gov (United States)

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

    2014-10-01

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

  3. 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.

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

    International Nuclear Information System (INIS)

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

  5. Kapitza conductance between Gd3Ga5O12 and superfluid helium

    International Nuclear Information System (INIS)

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

  6. Kapitza conductance between Gd3Ga5O12 and superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Lacaze, A.

    1985-10-10

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

  7. Low-Cost Helium Cryostat for 1.5K.

    Czech Academy of Sciences Publication Activity Database

    Hanzelka, Pavel; Jelínek, Josef; Musilová, V?ra

    Praha : Czech Committee of the International Institute of Refrigeration, 1998, s. 92-95. ISSN 1211-3611. [ Cryogenics /5./. Praha (CZ), 12.05.1998-15.05.1998] Subject RIV: BM - Solid Matter Physics ; Magnetism

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

    Science.gov (United States)

    T?kési, Károly; DuBois, Robert D.; Mukoyama, Takeshi

    2014-09-01

    The interaction between positronium and a helium atom is studied using the 5-body classical trajectory Monte Carlo method. We present the total cross sections for the dominant channels, namely for single ionization of the target, and ionization of the projectile, resulting from pure ionization and also from electron transfer (capture or loss) processes for 1-5.7 a.u. incident velocities of the positronium atom. Our results were compared with the calculated data using hydrogen projectiles having the same velocities as well as with the experimental data in collisions between H and He [R.D. DuBois, Á. Kövér, Phys. Rev. A 40, 3605 (1989)]. We analyze the similarities and deviations for ionization of helium atoms by positronium and hydrogen projectile impact. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

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

    Science.gov (United States)

    Erdem, Erinc; Kontis, Konstantinos; Saravanan, Selvaraj

    2014-01-01

    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. PMID:25494348

  11. Antiprotonic helium

    CERN Multimedia

    Eades, John

    2005-01-01

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

  12. 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)

  13. FLOATING PRESSURE CONVERSION AND EQUIPMENT UPGRADES OF TWO 3.5KW, 20K, HELIUM REFRIGERATORS

    Energy Technology Data Exchange (ETDEWEB)

    J. Homan, V. Ganni, A. Sidi-Yekhlef, J. Creel, R. Norton, R. Linza, G. Vargas, J. Lauterbach, J. Urbin, D. Howe

    2010-04-01

    Two helium refrigerators, each rated for 3.5 KW at 20 K, are used at NASA's Johnson Space Center (JSC) in Building No. 32 to provide cryogenic-pumping within two large thermal-vacuum chambers. These refrigerators were originally commissioned in 1996. New changes to the controls of these refrigerators were recently completed. This paper describes some of the control issues that necessitated the controls change-over. It will describe the modifications and the new process control which allows the refrigerators to take advantage of the Ganni Cycle “floating pressure” control technology. The controls philosophy change-over to the floating pressure control technology was the first application on a helium gas refrigeration system. Previous implementations of the floating pressure technology have been on 4 K liquefaction and refrigeration systems, which have stored liquid helium volumes that have level indications used for varying the pressure levels (charge) in the system for capacity modulation. The upgrades have greatly improved the performance, stability, and efficiency of these two refrigerators. The upgrades have also given the operators more information and details about the operational status of the main components (compressors, expanders etc.) of the refrigerators at all operating conditions (i.e. at various loads in the vacuum chambers). The performance data of the two systems, pre and post upgrading are presented.

  14. 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)

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

    Science.gov (United States)

    Scholder, Olivier; Jefimovs, Konstantins; Shorubalko, Ivan; Hafner, Christian; Sennhauser, Urs; Bona, Gian-Luca

    2013-10-01

    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. PMID:24013454

  16. Behaviour of the HeI 587.6, 667.8, 706.5 and 728.1nm lines in B-type stars. On the helium stratification in the atmosphere of magnetic helium peculiar stars.

    Science.gov (United States)

    Leone, F.; Lanzafame, A. C.

    1997-04-01

    High resolution spectra of the HeI587.6, 667.8 706.5 and 728.1nm lines have been obtained to test the prediction (notably by Vauclair et al. 1991) that helium abundance should decrease with depth in helium rich stars and increase in helium weak stars. A sample of B-type main sequence stars, with expected solar abundances and non stratified atmospheres, have also been observed in order to compare the behaviour of the selected lines with the chemically peculiar case and with theory. We found significant discrepancies with theory for the lines HeI 706.5. and 728.1nm, and, in order to outline differences between 'normal' and 'peculiar' stars, we have adopted an empirical correction to the Lorentz broadening parameter in the Voigt profile, under the assumption of LTE. This parameter is derived from the imposition of a satisfactory fit with observations for the relation equivalent width vs. effective temperature for normal B stars. For helium rich stars we confirm Vauclair et al. (1991) predictions that helium abundance decreases with depth. However, we found that helium abundance decreases with depth in helium weak stars too, which contradicts Vauclair et al. (1991) predictions. For some peculiar stars, the inferred helium abundance is in disagreement with the peculiarity class reported in the General Catalogue of Ap and Am stars (Renson et al. 1991).

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2008-01-01

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

  20. Effect of injection temperature, 5% pre-strain and long time aging on the high-temperature mechanical properties of helium injected 316 stainless steel

    International Nuclear Information System (INIS)

    The helium embrittlement of 316 stainless steel, helium injected to concentrations of 3 approx. 10 at ppm at 573 +- 50 or 1073 +- 20 K, was measured by tensile tests at 1023 K and was completly suppressed by the 5% pre-straining. This improved effect was lost by a post-injection again of 1000 h at 1123 K or 3000 h at 1023 K. It was concluded from the TEM observations that in the solution treated material helium bubbles were concentrated on the grain boundaries and caused embrittlement, but in the 5% pre-strained material helium bubbles nucleated on the dislocations and grew large enough to be unable to be dragged to the grain boundaries by the dislocations during the tensile test. The embrittlement after the long time aging was due to the gathering of the large helium bubbles at the sigma-phase boundaries by a sweepout mechanism due to dislocation climb during the long time thermal recovery process. (orig.)

  1. Effect of helium on swelling and microstructural evolution in ion-irradiated V-15Cr-5Ti alloy

    International Nuclear Information System (INIS)

    An investigation was made on the effects of implanted helium on the swelling and microstructural evolution that results from energetic single- and dual-ion irradiation of the V-15Cr-5Ti alloy. Single-ion irradiations were utilized for a simulated production of the irradiation damage that might be expected from neutron irradiation of the alloy in a reactor with a fast neutron energy spectrum (E > 0.1 MeV). Dual-ion irradiations were utilized for a simulated production of the simultaneous creation of helium atoms and irradiation damage in the alloy in the MFR environment. Experimental results are also presented on the radiation-induced segregation of the constituent atoms in the single- and dual-ion irradiated alloy

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

    International Nuclear Information System (INIS)

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

  3. Helium penetration into solids in process of their deformation at 0.5-4.2 K

    International Nuclear Information System (INIS)

    It is shown by means of mass spectrometric technique that the helium penetration phenomenon detected earlier (dislocation-dynamical diffusion) into L:F monocrystals in the process of their deformation in the liquid 3He and 4He media takes place also for other solid bodies: NaCl, CsI monocrystals and Cu, Pb, Al, Cd, In, Zn polycrystals. Helium penetrates into the surface layer of the investigated solid bodies in approximately 1012 at/cm2 quantity. Gas release curve shapes obtained during dynamical annealing of the mono- and polycrystals deformed in liquid 3He is determined by a materials its dislocation structure and impurity state. It is possible to suggest on the baisis of the performed investigation into a wide range of materials that the phenomenon of the medium atom penetration into deformed crystalline bodies has a common nature

  4. Microstructural analysis of 9% Cr martensitic steels containing 0.5 at.% helium

    International Nuclear Information System (INIS)

    Microstructural examinations by transmission electron microscopy and small angle neutron scattering were performed on 100 ?m thick specimens of 9Cr-1Mo (EM10) and modified 9Cr-1Mo (T91) martensitic steels homogeneously implanted with 23 MeV ? particles to a concentration of 5000 appm. Two implantation temperatures were selected, 250 and 550 deg. C, which correspond respectively to the lower and higher bounds of the operation temperature range foreseen for the window of accelerator driven systems devoted to waste transmutation. 250 deg. C is also the maximum operating temperature of the European spallation source window. The TEM samples were punched out from implanted tensile specimens following testing, which revealed, as detailed in a companion paper [P. Jung et al., these Proceedings], drastic hardening and complete ductility loss for the specimens implanted at 250 deg. C. Helium bubbles were detected in both materials implanted at 250 and 550 deg. C and bubble size distributions as well as number densities were determined. Furthermore, it was found that the bubbles are at thermodynamic equilibrium. Based on the microstructural results, it is shown that the high degree of hardening of specimens implanted at 250 deg. C is due to the high density of tiny helium bubbles they contain. It is furthermore suggested that the brittle, intergranular fracture mode displayed by these specimens results from the combined effects of pronounced intragranular hardening and weakeninced intragranular hardening and weakening of prior austenite grain boundaries due to helium

  5. Helium energy spectra from 5 to >150 MeV/n from SOHO EPHIN

    International Nuclear Information System (INIS)

    Since its launch in Dec 1995 the SOHO spacecraft is providing observations of energetic particles at the lagrangian point L1. On board is the Electron Proton Helium Instrument (EPHIN), which measures nominally electrons in the energy range from 250 keV to >10 MeV, protons from 4 MeV to >53 MeV and helium from 4 MeV/n to >53 MeV/n. The instrument is based on six semiconductor silicon detectors with an anticoincidence scintillator. The total thickness for stopping particles is 13.45mm. The well-proven De/dx-E method is used to determine energy and mass of the stopping particles. However, penetrating particles, i.e. electrons >10 MeV and nuclei >53 MeV/n, are registered in a single integral channel. In this work we make use of the dE/dx-dE/dx method and show that the energy range can successfully be extended to 150 MeV/n for helium. Energy spectra as well as their temporal evolution are presented in the investigation of the modulation of anomalous cosmic rays (ACR) and Galactic cosmic rays (GCR)

  6. First principles assessment of helium trapping in Y{sub 2}TiO{sub 5} in nano-featured ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Yanan [School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jiang, Yong, E-mail: yjiang@csu.edu.cn, E-mail: odette@engineering.ucsb.edu; Yang, Litong; Lan, Guoqiang [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Lab for Nonferrous Materials of Ministry of Education, Central South University, Changsha 410083 (China); Robert Odette, G., E-mail: yjiang@csu.edu.cn, E-mail: odette@engineering.ucsb.edu; Yamamoto, Takuya [Materials Department, University of California, Santa Barbara 93106 (United States); Shang, Jiacheng; Dang, Ying [National Key Lab for Reactor Fuels and Materials, Nuclear Power Institute of China, Chengdu 610041 (China)

    2014-10-14

    Nano-scale Y{sub 2}Ti{sub 2}O{sub 7} and Y{sub 2}TiO{sub 5} 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 Y{sub 2}TiO{sub 5}. The results suggest that helium is more deeply trapped in Y{sub 2}TiO{sub 5} compared to Y{sub 2}Ti{sub 2}O{sub 7}. Helium occupies open channels in Y{sub 2}TiO{sub 5}, where it weakly chemically interacts with neighboring oxygen anions, and results in less volume expansion compared to Y{sub 2}Ti{sub 2}O{sub 7}, 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. 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)

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

    International Nuclear Information System (INIS)

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

  9. ?-Helium-4 scattering experiment at 5GeV/c. Data processing

    International Nuclear Information System (INIS)

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

  10. 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.

  11. 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)

  12. Mass distribution at moderate energy: 38.5 MeV helium ion induced fission of 232Th

    International Nuclear Information System (INIS)

    Mass distribution in 38.5 MeV helium ion induced fission of 232Th was determined using radiochemical and spectrometric techniques. The chain yields of 30 different fission products covering both symmetric and asymmetric mass divisions were determined. The radiochemical data in the symmetric region was very useful in establishing the peak corresponding to symmetric mass division. The correlation between the peak, to valley ratio (P/V) and the excitation energy based on literature data was used to arrive at the contributions of the first and third chance fission. This, together with the statistical model calculations for multichance fission leads to an estimate of af/an 1.03. (author)

  13. 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

  14. 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...

  15. Heat transfer from horizontal cylinder to subcooled liquid helium

    International Nuclear Information System (INIS)

    Experiments were made on the heat transfer in subcooled liquid helium I and II from a horizontal copper cylinder which was 2.5 cm in diameter and 5 cm in length. The results for helium I indicated some difference between subcooled and saturated helium. The heat flux in subcooled helium was larger than that of saturated helium in the nucleate-boiling region. In the free-convection region, the heat flux of subcooled helium was smaller than that of saturated helium. In the experiments for helium II, it was found that the difference of heat transfer rate between subcooled and saturated helium were not significant. (author)

  16. 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...

  17. 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.

  18. 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)

  19. Level indicator for liquid helium

    International Nuclear Information System (INIS)

    A level indicator for liquid helium and its block diagram are described. A section of wire made of a superconductor serves as the level indicator for measuring liquid helium. A current flows along this wire, that a part of wire, which is in helium vapours, transfers to a normal state due to joule heat release and corresponding wire overheating, while the other part of wire, which is in liquid helium, remains superconductive due to better heat exchange in liquid, than in gas. Thus, indicator resistance linearly depends on the level of liquid helium, the zero resistance of the indicator corresponding to the maximal level. The indicator differs in simplicity, high sensitivity, linearity and convenience in operation. The indicator design, volt-ampere characteristics of the indicator made of Nb-Ti wire 0.05 mm in diameter at different levels of liquid helium and an electric block diagram are presented. The indicator error does not exceed 5 mm

  20. A new design code for 1,5 Mwt helium heat exchanger

    International Nuclear Information System (INIS)

    There is the ASME B and PV code for design criteria of high temperature heat exchanger and these design codes cannot be applied to the 1.5 Mwt Heat Exchanger System because the codes applying range are limited up to 8150C, while the new heat exchanger system is supposed to be operated at the temperatures upto 10000C. Because this heat exchanger is a test loop for nuclear direct steal making plant, its design and construction requires as much safety assurance as the nuclear power plant. In order to satisfy safety requirement, a new design code specifying heat exchanger components operable at a maximum allowable temperature of 1,0000C was proposed. (orig.)

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

    CERN Document Server

    2004-01-01

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

  2. X-ray studies of nickel, steel - Kh16N15M3B and steel -Kh20N40M5B irradiated by helium ions

    International Nuclear Information System (INIS)

    The effect of helium ion irradiation to the concentrations of 0.05, 0.15, 0.50 and 1.00 at.% He (with He+ ion energy up to 3.5 MeV) on the structure of recrystallized nickel, steel-Kh16N15M3B and steel-Kh20N40M5B is studied by means of X-ray analysis. It is shown that phase composition of irradiated samples does not exhibit any changes: the initial f.c.c. structure was preserved under all irradiations. The lattice spacing of irradiated samples is found to vary nonmonotonically depending on the concentration of injected helium. Experimental data on the effect of post-irradiation annealing are indicative of nonmonotonic variation of the lattice spacing depending on the annealing temperature as well. It is concluded that changes observed in the diffraction pattern for investigated samples under He+ ion irradiation are not due to radiation damages (interstices, vacancies, dislocation loops, stacking faults, etc.) but to accumulation and evolution of helium atoms in the matrix lattice

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

    International Nuclear Information System (INIS)

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

  4. Helium behaviour in nuclear glasses

    International Nuclear Information System (INIS)

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

  5. Calculation of the electron-impact coherence parameters for excitation of the 31D state of helium at 26.5 eV

    International Nuclear Information System (INIS)

    The 19-state and 29-state R-matrix methods of Fon et al have been extended to calculate the differential cross section (DCS) and electron-impact coherence parameters (EICP) associated with excitation of the 3 1D state of helium for an incident electron energy of 26.5 eV at electron scattering angles ranging from 0-180o. The calculated EICP values are compared with the only experimental data reported recently by McLaughlin et al. The agreement is good. (Author)

  6. 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

  7. Thermal desorption of implanted helium from beryllium

    International Nuclear Information System (INIS)

    Hot isostatic pressed foils of 99.5 wt.% beryllium have been implanted at room temperature with 30 keV helium to fluences ranging from 1020 to 1021 He+/m2. Linear ramp thermal desorption measurements up to 1073 K (? 0.7 Tm) were performed to study the mechanisms by which the helium is trapped. Some of the samples have been deliberately corroded to investigate the effect of the surface contamination on the helium release. (orig.)

  8. 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...

  9. Helium induced blistering during simultaneous sputtering

    International Nuclear Information System (INIS)

    The results of helium implantation during sputtering of stainless steel are described in this paper. These experiments simulate the simultaneous bombardment of unconfined 3.5 MeV alpha particles and erosion due to sputtering primarily from the charge exchange neutral (D, T) flux. The results indicate that helium induced blister formation can take place, with simultaneous sputtering, under conditions appropriate to a fusion reactor. The critical experimental parameters of helium flux and surface velocity are in excellent agreement with simple calculations that predict the conditions under which helium induced surface deformation takes place. (Auth.)

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

    International Nuclear Information System (INIS)

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

  11. Positronium formation in helium

    International Nuclear Information System (INIS)

    Preliminary measurements of positronium formation in helium gas have been completed. The experimental method involves the transmission of a beam of slow positrons of controllable energy through a gas cell and the detection of all those positrons which do not form positronium. The method, in principle, allows the measurement of absolute values of the positronium formation cross section. Results in the energy range from 9eV to 26.5eV show a distinct drop in the collected slow positron flux above the positronium formation threshold energy. (Auth.)

  12. Liquid helium target

    International Nuclear Information System (INIS)

    A liquid helium target system has been built and used for the experiment on the reaction 4He(?, p). The target system has worked satisfactorily; the consumption rate of liquid helium is 360 ml/h and the cryogenic system retains liquid helium for about ten hours. The structure, operation and performance of the target system are reported. (author)

  13. Subharmonic responses in liquid helium

    International Nuclear Information System (INIS)

    We report measurements of the subharmonic responses of liquid helium to ultrasound in the temperature range 1.3 K< T<2.5 K at applied frequencies of 0.3, 1.0, 2.8, and 10 MHz. Experimental results are compared in detail to the oscillating bubble model of Eller and Flynn and to predictions based upon parametric amplification. We show that the subharmonic response in liquid helium, below the superfluid transition, is directly associated with bulk turbulence. Visualization of the subharmonic response by light diffraction demonstrates that it can be a sustained and coherent bulk effect

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

    International Nuclear Information System (INIS)

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

  15. Direct photoionization of excited helium

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    ARD, K.E.

    2000-04-19

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

  17. Two-dimensional silicide 5×3 structure on Cu(001) as seen by scanning tunneling microscopy and helium-atom scattering

    Science.gov (United States)

    Graham, A. P.; Hinch, B. J.; Kochanski, G. P.; McCash, E. M.; Allison, W.

    1994-11-01

    The incommensurate 5×3 structure, which is formed when silicon is deposited on copper(001) via a saturation exposure to silane at 420 K, has been examined with helium-atom scattering and scanning tunneling microscopy. The surface was found to be a two-dimensional copper-silicon alloy having large domains of a near perfect hexagonal structure with Cu2Si stoichiometry. The surface layer displays a rotation of one surface-lattice vector with respect to the substrate of 4.4°, and a high-order commensuration along the other surface-lattice vector, without rotation. The overlayer exhibited unequal densities of the four possible domains and it appears that the long-range order is influenced by the presence of steps on the copper(001) surface. The overall atomic density in the surface layer is 27.6% higher than on the unreconstructed surface. The driving force for the formation of the sheared hexagonal structure is believed to be the need to increase surface coordination and density together with a strongly directional in-plane bonding between Cu and Si atoms.

  18. A helium regenerative compressor

    International Nuclear Information System (INIS)

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

  19. Improved theory of helium fine structure

    OpenAIRE

    Pachucki, Krzysztof

    2006-01-01

    Improved theoretical predictions for the fine-structure splitting of $2^3P_J$ levels in helium are obtained by the calculation of contributions of order $\\alpha^5 Ry$. New results for transition frequencies, $\

  20. Stopping of 5-100 keV helium in tantalum, niobium, tungsten, and AISI 316L steel

    International Nuclear Information System (INIS)

    The stopping power of Ta, Nb, W, and AISI 316L stainless steel for He ions at velocities below the Bohr velocity has been deduced by comparing the ranges of 5 to 100 keV He+-ions determined with the elastic-recoil-detection-analysis method with those obtained in molecular dynamics simulations. The nuclear slowing down was treated through the use of molecular dynamics calculations and a potential obtained from density-functional theory calculations. The comparisons showed that the electronic stopping powers given by Ziegler, Biersack and Littmark, had to be multiplied with a factor of 1.4 for Ta, 1.0 for Nb, 1.1 for W, and 1.0 for AISI 316L. The uncertainty of the factors and hence the scaled stopping power values is ±5%. The total stopping powers were obtained from molecular dynamics simulations in which the modified electronic stopping powers were used. (orig.)

  1. 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)

  2. 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)

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

    International Nuclear Information System (INIS)

    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. (active media)

  4. 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

  5. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

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

  6. Helium resources of Mare Tranquillitatis

    Science.gov (United States)

    Cameron, Eugene N.

    1991-01-01

    Wisconsin Center for Space Automation and Robotics, Univ. of Wisc., Madison, Wisc. Mare Tranquillitatis, about 300000 sq km in area, is currently the most promising lunar source of He-3 for fueling fusion power plants on Earth. About 60 pct. of the mare regolith consists of particles 100 microns or less in diameter. Helium and other gases derived from the solar wind are concentrated in the fine size fractions. Studies of very small craters indicate that the average regolith exceeds 3 m in areas away from larger craters and other mare features not amenable to mining. There is no evidence of decrease of helium content of regolith and depth. Helium is known to be enriched in regoliths that are high in TiO2 content. Remote sensing indicates that about 90 pct. of Mare Tranquillitatis is covered by regolith ranging from about 6 to +7.5 pct. TiO2; inferred He contents range from 20 to at least 45 wppm total helium (7 to 18 wppb He-3). Detailed studies of craters and inferred ejecta halos displayed on high resolution photographs of the Apollo 11 and Ranger 8 areas suggest that as much as 50 pct. of the mare regolith may be physically minable, on average, with appropriate mining equipment. Assuming that the average thickness of regolith is 3 m, and that 50 pct. of the mare area is minable, the He-3 content of minable regolith containing 20 to 45 wppm total He is estimated at about 94,000 tonnes.

  7. Helium refrigeration considerations for cryomodule design

    International Nuclear Information System (INIS)

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

  8. Helium refrigeration considerations for cryomodule design

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-29

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

  9. Helium leak testing the Westinghouse LCP coil

    International Nuclear Information System (INIS)

    The tests, equipment, and techniques used to check the Westinghouse LCP coil for coolant flow path integrity and helium leakage are unique in terms of test sensitivity and application. This paper will discuss the various types of helium leak testing done on the LCP coil as it enters different stages of manufacture. The emphasis will be on the degree of test sensitivity achieved under shop conditions, and what equipment, techniques and tooling are required to achieve this sensitivity (5.9 x 10-8 scc/sec). Other topics that will be discussed are helium flow and pressure drop testing which is used to detect any restrictions in the flow paths, and the LCP final acceptance test which is the final leak test performed on the coil prior to its being sent for testing. The overall allowable leak rate for this coil is 5 x 10-6 scc/sec. A general evaluation of helium leak testing experience are included

  10. 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

  11. Helium the disappearing element

    CERN Document Server

    Sears, Wheeler M

    2015-01-01

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

  12. 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)

  13. 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...

  14. Correlations in Hot Dense Helium

    OpenAIRE

    Militzer, Burkhard

    2009-01-01

    Hot dense helium is studied with first-principles computer simulations. By combining path integral Monte Carlo and density functional molecular dynamics, a large temperature and density interval ranging from 1000 to 1000000 K and 0.4 to 5.4 g/cc becomes accessible to first-principles simulations and the changes in the structure of dense hot fluids can be investigated. The focus of this article are pair correlation functions between nuclei, between electrons, and between elec...

  15. Charged Hydrogenic, Helium and Helium-Hydrogenic Molecular Chains in a Strong Magnetic Field

    OpenAIRE

    Turbiner, A. V.; Guevara, N. L.; Vieyra, J. C. Lopez

    2009-01-01

    A non-relativistic classification of charged molecular hydrogenic, helium and mixed helium-hydrogenic chains with one or two electrons which can exist in a strong magnetic field $B \\lesssim 10^{16} $G is given. It is shown that for both $1e-2e$ cases at the strongest studied magnetic fields the longest hydrogenic chain contains at most five protons indicating to the existence of the $\\rm{H}_5^{4+}$ and $\\rm{H}_5^{3+}$ ions, respectively. In the case of the helium chains the ...

  16. Liquid helium plant in Dubna

    International Nuclear Information System (INIS)

    The liquid-helium cooling capacity installed at the Laboratory of High Energies is about 5 kw at a 4.5 K temperature level. It is provided with four industrial helium liquefiers of 1.6 kw/4.5 K each. They have been made by the Russian enterprise NPO GELYMASH and upgraded by the specialists of the Laboratory. The first one was put into operation in 1980, the two others in 1991, and the last one is under commissioning. The development of the LHE cryoplant was concerned with the construction of the new superconducting accelerator Nuclotron aimed to accelerate nuclei and heavy ions up to energies of 6 GeV/u. The first test run at the Nuclotron was carried out in March 1993, and the total running time has been about 2000 hours up to now. Since 1992 the cryoplant has been intensively used by the users outside the Laboratory. More than a million liters of liquid helium was provided in 1993 for such users. The reliability of the cryoplant system was as high as 98 percent for 4500 hours of operation in 1993-1994. 7 refs., 4 figs., 1 tab

  17. An Introduction to the Helium Ion Microscope

    Science.gov (United States)

    Notte, John; Ward, Bill; Economou, Nick; Hill, Ray; Percival, Randy; Farkas, Lou; McVey, Shawn

    2007-09-01

    A new microscope has been developed that uses a beam of helium ions which is focused and scanned across the sample. In principle, and in its applications, it is similar to a traditional scanning electron microscope (SEM). However, the source technology, the sample interaction, and the contrast mechanisms are distinctly different. The helium ion source offers high brightness (4×109 A/cm2sr) and a small energy spread (?E/E˜3×10-5), and hence allows the beam to be focused to small probe sizes (as small as 0.25 nm). As the beam interacts with the sample, the beam penetrates relatively deeply before it diverges and hence there is a narrow sample interaction region near the surface. The helium beam generates secondary electrons, scattered helium atoms (ions and neutrals), and other detectable particles from which images can be generated or analysis can be performed.

  18. 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)

  19. 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

  20. The helium purification system of the HTR-10

    International Nuclear Information System (INIS)

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

  1. Light scattering by a liquid-gas helium spray

    Science.gov (United States)

    Ladam, Y.; Wolf, P.-E.; Thibault, P.; Puech, L.

    2001-05-01

    Light scattering by liquid helium droplets or gaseous helium bubbles is strongly forward. This has two direct experimental consequences: rare scatterers are very bright in a narrow (ll 5^{circ}) angular region in the forward direction; and even in the presence of multiple scattering the intensity collected at large angles is linear in the concentration of scatterers. These properties are explained, and the second one is illustrated with a liquid-gas helium spray.

  2. The descending helium balloon

    Science.gov (United States)

    Helseth, Lars Egil

    2014-07-01

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

  3. Cooling with Superfluid Helium

    OpenAIRE

    Lebrun, P.; Tavian, L

    2015-01-01

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

  4. 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...

  5. 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...

  6. High Efficiency Regenerative Helium Compressor Project

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

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

    International Nuclear Information System (INIS)

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

  8. Tritium/Helium-3 Dating

    Science.gov (United States)

    First, the USGS summarizes the use of tritium and helium-3 for dating geologically young groundwater (1). Researchers can find the conditions needed to solve the helium isotope mass balance as well as equations and corrections needed to obtain the age of water. The second website, provided by the Rosenstiel School of Marine and Atmospheric Sciences, discusses the presence of tritium and helium isotopes in the oceans (2). Users can find out about the Noble Gas Isotope Lab's research projects including the _Mantle 3He Distribution and Deep Circulation in the Indian Ocean_. Next, the University of Ottawa offers equations for helium and tritium concentrations and decay (3). Visitors can also learn how solubility of noble gases is affected by temperature. Fourth, the University of Waterloo describes the characteristics of the hydrogen radioisotope, tritium (4). The website explains how tritium was discovered through the work of Lord Rutherford, Sir John, Ernest Lawrence, Luis Alvarex, Willard Libby, and others. Next, the University of T'bingen furnishes a pdf file dealing with numerous dating techniques including fission track, radio carbon, and thermoluminescence dating (5). Beginning on page nine, individuals can learn about tritium formation and decay as well as its use in dating ground water. At the sixth website, the USGS describes the characteristics of the stable isotopes of helium (6). Visitors can discover how 3He is used to date geologically young ground water, whereas 4He is used to date older ground water. The seventh website, created by SAHRA (Sustainability of semi-Arid Hydrology and Riparian Areas) at the University of Arizona, illustrates the effectiveness of isotope hydrology in "understanding fundamental physical, chemical, biological, and climate forcing processes occurring in a watershed" (7). Along with the discussion of the fundamentals of age dating and sources of isotopes, visitors can learn the advantages to using tritium for water samples collected in the field. Lastly, the Victoria University of Manchester introduces its research using noble gas isotopes to better understand earth systems (8). Visitors can discover the decay rates of tritium to 3He and the rates of accumulation of 4He in older groundwater as well as many applications of dating water.

  9. Superfluid helium acoustic microscopy

    International Nuclear Information System (INIS)

    This dissertation describes the development of an acoustic microscope operating in superfluid helium at temperatures less than 0.1K. The acoustic microscope uses sound waves, brought to a focus in a liquid, to image a sample. The lateral resolution of the microscope is approximately equal to the wavelength of the sound in the liquid. Low temperature superfluid helium is the ultimate fluid for acoustic microscopy because of its extremely small acoustic attenuation, allowing short wavelength and high resolution imaging. The present resolution of the helium acoustic microscope is 200 A using 8 GHz sound waves. The wavelength in helium at this frequency is only 300 A, twenty times shorter than red light. Several images are presented, including biological and integrated circuit samples. Comparisons are made with other forms of high resolution microscopy, specifically the scanning and transmission electron microscopes. By virtue of its contrast mechanisms and high resolution, the helium acoustic microscope can image many sample features that cannot be seen in other ways

  10. Atmospheric helium isotopic ratio

    International Nuclear Information System (INIS)

    A recent study of the isotopic ratio of helium (3He/4He) in the terrestrial atmosphere led the individuals who made the investigation to suggest that this ratio is decreasing with time, probably due to anthropogenic release of low isotopic ratio crustal helium from oil and gas wells. The measurements made over an 11 year period from 1977 to 1988 led to the prediction that the rate of decrease was of the order of 1x10-9/yr. Several absolute isotopic ratio measurements made between 1969 and the present time also have been reported. These show a slight decrease in the helium isotopic ratio (much less than the 11 year data set shows). In the present paper, the authors report an unpublished, absolute helium isotopic ratio measurement the authors made in 1956. This value, when combined with the previously reported results, extends the time over which such measurements were made to a 32 year period and does not confirm that there is any decrease in the helium isotopic ratio in the atmosphere over this time. 12 refs., 1 fig., 1 tab

  11. atmospheric helium isotopic ratio

    Science.gov (United States)

    Hoffman, John H.; Nier, Alfred O.

    1993-01-01

    A recent study of the isotopic ratio of helium (3He/4He) in the terrestrial atmosphere led the individuals who made the investigation to suggest that this ratio is decreasing with time, probably due to anthropogenic release of low isotopic ratio crustal helium from oil and gas wells. The measurements made over an 11 year period from 1977 to 1988 led to the prediction that the rate of decrease was of the order of 1 × 10-9/yr. Several absolute isotopic ratio measurements made between 1969 and the present time also have been reported. These show a slight decrease in the helium isotopic ratio (much less than the 11 year data set shows). In the present paper, we report an unpublished, absolute helium isotopic ratio measurement the authors made in 1956. This value, when combined with the previously reported results, extends the time over which such measurements were made to a 32 year period and does not confirm that there is any decrease in the helium isotopic ratio in the atmosphere over this time.

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

    International Nuclear Information System (INIS)

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

  13. 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.

  14. Helium Production and Possible Projection

    Directory of Open Access Journals (Sweden)

    Steve Mohr

    2014-03-01

    Full Text Available The future availability of helium has been raised as an issue in the literature. However, a disaggregated projection of helium production has not been attempted, presumably due to the difficult nature of accessing disaggregated historic production data to test the accuracy of this issue. This paper presents collated and estimated historic helium production statistics from 1921 to 2012 for each helium producing country in the world and by U.S. state. A high and regular growth projection of helium has been created. It is found that helium resources are sufficient for the near future, with the projected production plateauing in 2060–2075 and 2090–2100 for the high and regular growth scenarios, respectively. As long as natural gas deposits with helium are appropriately managed, there is little likelihood for helium shortages to occur in the short term due to geologic constraints.

  15. 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.

  16. Cavitation in flowing superfluid helium

    Science.gov (United States)

    Daney, D. E.

    1988-01-01

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

  17. Charged particles over liquid helium

    International Nuclear Information System (INIS)

    The analysis of dusty plasma properties at cryogenic temperatures shows that it is necessary to take into account the condensation of helium on the plasma particles. The micron particles in the saturated helium vapor are covered by a liquid helium film of 100 A thick. This leads to the limitation of electron charge of the particles, as the electrons can hardly penetrate such a film. The exceptions are Cs, Rb and K clusters as they are not wetted with helium.

  18. Onset Properties of Supersolid Helium

    OpenAIRE

    Yu, Yongle

    2010-01-01

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

  19. Helium in Chemically Peculiar Stars

    OpenAIRE

    Leone, F.

    1998-01-01

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

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

    OpenAIRE

    Pachucki, Krzysztof; Yerokhin, Vladimir A.

    2010-01-01

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

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

    OpenAIRE

    Vogel, Eckhard; Bich, Eckard; Hellmann, Robert

    2007-01-01

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

  2. Helium White Dwarfs in Cataclysmic Variables

    OpenAIRE

    Shen, Ken J.; Idan, Irit; Bildsten, Lars

    2009-01-01

    Binary evolution predicts a population of helium core (M < 0.5 Msol) white dwarfs (WDs) that are slowly accreting hydrogen-rich material from low mass main sequence or brown dwarf donors with orbital periods less than four hours. Four binaries are presently known in the Milky Way that will reach such a mass-transferring state in a few Gyr. Despite these predictions and observations of progenitor binaries, there are still no secure cases of helium core WDs among the mass-tran...

  3. 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.

  4. 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.

  5. 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)

  6. Helium refrigerator for 'SULTAN'

    International Nuclear Information System (INIS)

    The authors describe the helium refrigerator designed for the SULTAN test facility. SULTAN (Supraleiter-Testanlage) is intended to serve for the developments and testing of high field superconducting magnets. These magnets are needed mainly for future applications in nuclear fusion. (Auth.)

  7. Cooling by mixing of helium isotopes

    International Nuclear Information System (INIS)

    The principles of the helium dilution refrigerator are outlined. The lowest temperature attained with a continuously operated dilution refrigerator was about 10 mK, and 5 mK for a limited period when the supply of concentrated 3He to the mixing chamber was interrupted. (R.S.)

  8. 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

  9. The Weakest Link: Bonding between Helium Atoms

    Science.gov (United States)

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

    2007-01-01

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

  10. Helium behavior in vanadium-based alloys irradiated in the dynamic helium charging experiments

    International Nuclear Information System (INIS)

    Helium effect of neutron irradiated vanadium alloys, containing titanium, has been studied using Dynamic Helium Charging Experiment (DHCE) in FFTF. Cavity formation was observed only in pure vanadium irradiated at 430 to 600 C and in V-5Ti irradiated at 600 C. No apparent cavity formation was obtained in V-3Ti-1Si and V-4Cr-4Ti. The precipitation of titanium oxide in V-5Ti, V-3Ti-1Si and V-4Cr-4Ti occurred in all irradiation conditions in this study and the precipitates of Ti5Si3 only appeared in V-3Ti-1Si irradiated at 600 C up to 15 dpa with helium generation rate of 4 appmHe/dpa. It is suggested that titanium oxide plays an important role for suppression of cavity formation and swelling from early stage of irradiation. Detail characterization of precipitates and He effect for neutron damages in vanadium alloys are discussed here

  11. Creating nanohole arrays with the helium ion microscope

    Science.gov (United States)

    Ananth, Mohan; Stern, Lewis; Ferranti, David; Huynh, Chuong; Notte, John; Scipioni, Larry; Sanford, Colin; Thompson, Bill

    2011-06-01

    Helium Ion Microscopy has been established as a powerful imaging technique offering unique contrast and high resolution surface information. More recently, the helium ion beam has been used for nanostructuring applications similar to a gallium focused ion beam. A key difference between helium and gallium induced sputtering is the less intense damage cascade which lends this technique to precise and controlled milling of different materials enabling applications. The helium ion beam has been used for drilling 5nm holes in a 100nm gold foil (20:1 aspect ratio) while the gallium beam sputtered holes of a similar aspect ratio seem to be limited to a 50nm hole size. This paper explores the drilling of nanopores in gold films and other materials and offers an explanation for the observed differences in results between helium and gallium ions.

  12. Cryosorption vacuum pumping of hydrogen and helium mixtures

    International Nuclear Information System (INIS)

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

  13. Helium accumulation in groundwater. Pt. 3

    International Nuclear Information System (INIS)

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

  14. 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.

  15. 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.

  16. 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.

  17. Purification of helium gas for the helium test loop

    International Nuclear Information System (INIS)

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

  18. Helium Ion Microscopy

    OpenAIRE

    Hlawacek, Gregor; Veligura, Vasilisa; van Gastel, Raoul; Poelsema, Bene

    2013-01-01

    Helium Ion Microcopy (HIM) based on Gas Field Ion Sources (GFIS) represents a new ultra high resolution microscopy and nano-fabrication technique. It is an enabling technology that not only provides imagery of conducting as well as uncoated insulating nano-structures but also allows to create these features. The latter can be achieved using resists or material removal due to sputtering. The close to free-form sculpting of structures over several length scales has been made p...

  19. Excitations in confined helium

    OpenAIRE

    Apaja, V.; Krotscheck, E.

    2003-01-01

    We design models for helium in matrices like aerogel, Vycor or Geltech from a manifestly microscopic point of view. For that purpose, we calculate the dynamic structure function of 4He on Si substrates and between two Si walls as a function of energy, momentum transfer, and the scattering angle. The angle--averaged results are in good agreement with the neutron scattering data; the remaining differences can be attributed to the simplified model used here for the complex pore...

  20. 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.

  1. 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

  2. Applications of Groundwater Helium

    Science.gov (United States)

    Kulongoski, Justin T.; Hilton, David R.

    2011-01-01

    Helium abundance and isotope variations have widespread application in groundwater-related studies. This stems from the inert nature of this noble gas and the fact that its two isotopes ? helium-3 and helium-4 ? have distinct origins and vary widely in different terrestrial reservoirs. These attributes allow He concentrations and 3He/4He isotope ratios to be used to recognize and quantify the influence of a number of potential contributors to the total He budget of a groundwater sample. These are atmospheric components, such as air-equilibrated and air-entrained He, as well as terrigenic components, including in situ (aquifer) He, deep crustal and/or mantle He and tritiogenic 3He. Each of these components can be exploited to reveal information on a number of topics, from groundwater chronology, through degassing of the Earth?s crust to the role of faults in the transfer of mantle-derived volatiles to the surface. In this review, we present a guide to how groundwater He is collected from aquifer systems and quantitatively measured in the laboratory. We then illustrate the approach of resolving the measured He characteristics into its component structures using assumptions of endmember compositions. This is followed by a discussion of the application of groundwater He to the types of topics mentioned above using case studies from aquifers in California and Australia. Finally, we present possible future research directions involving dissolved He in groundwater.

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

    International Nuclear Information System (INIS)

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

  4. 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

  5. The winter helium bulge revisited

    Science.gov (United States)

    Liu, Xianjing; Wang, Wenbin; Thayer, Jeffrey P.; Burns, Alan; Sutton, Eric; Solomon, Stanley C.; Qian, Liying; Lucas, Greg

    2014-10-01

    A newly implemented helium module in the National Center for Atmospheric Research-Thermosphere Ionosphere Electrodynamics general circulation model offers the first opportunity in three decades to describe helium behavior in the context of a first principles, self-consistent model and to test early theories of wintertime helium bulge formation. This study shows general agreement with the findings of Reber and Hays (1973) but articulates the definitive role of vertical advection in the bulge formation. Our findings indicate vertical advection and molecular diffusion are the dominate processes responsible for the solstice helium distribution. Horizontal winds indirectly contribute to the helium bulge formation by their divergent wind field that leads to vertical winds in order to maintain thermosphere mass continuity. As a minor gas, thermospheric helium does not contribute to mass continuity and its distribution is dictated by more local interactions and constraints.

  6. Broadening and shift of thulium resonance lines by helium

    International Nuclear Information System (INIS)

    The absorption spectra of twenty resonance lines of atomic thulium are studied in the presence of helium whose pressure was 25--85 atm. The dependences of the width and shift of the electric-dipole transition lines on the pressure of helium are approximated by straight lines. The constants of the broadening and shift of the indicated lines of thulium by helium have values typical for metal atoms in helium. An exceptionally small broadening by helium is detected for the 1.14-?m line of thulium, corresponding to a magnetic-dipole transition between the 2F5/sub //2 and 2F7/sub //2 levels of the ground state, equal to (1.0 +- 0.2) x 10-3 cm-1/r. d., which is more than 2 orders of magnitude smaller than the typical values for lines of similar transitions in atoms of other metals. A red shift by helium is detected by lines of resonant electric-dipole transitions caused by a transition of the f electron to the 5d state. The influence on the broadening and shift by helium for lines of the resonant electric-dipole transitions of thulium, of the screening of transitions by the outer 6s2 shell, and of the superposition of electronic configurations is noted

  7. Cavitation pressure in liquid helium

    OpenAIRE

    Caupin, Frederic; Balibar, Sebastien

    2001-01-01

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

  8. Reciprocating magnetic refrigerator for helium liquefaction

    International Nuclear Information System (INIS)

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

  9. Development of 18 K helium refrigeration system for CERN

    CERN Document Server

    CERN. Geneva

    2004-01-01

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

  10. Liquid-helium scintillation detection with germanium photodiodes

    International Nuclear Information System (INIS)

    Special high-purity germanium photodiodes have been developed for the direct detection of vacuum ultraviolet scintillations in liquid helium. The photodiodes are immersed in the liquid helium, and scintillations are detected through one of the bare sides of the photodiodes. Test results with scintillation photons produced by 5.3-MeV ? particles are presented. The use of these photodiodes as liquid-helium scintillation detectors may offer substantial improvements over the alternate detection method requiring the use of wavelength shifters and photomultiplier tubes

  11. Helium ion implanted waveguide lasers

    International Nuclear Information System (INIS)

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

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

    OpenAIRE

    Moreira, Manuel; Madureira, Pedro

    2005-01-01

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

  13. 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)...

  14. Portable detector set discloses helium leak rates

    Science.gov (United States)

    Anderson, G. E.

    1967-01-01

    Portable helium detector measuring helium leak rates makes possible the use of the inert gas helium as a tracer. This helps solve safety and contamination problems in detecting leaks in closed fluid systems.

  15. 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.)

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

    CERN Document Server

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

    CERN Document Server

    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 ...

  18. The irradiation of high purity and helium doped aluminium with aluminium ions

    International Nuclear Information System (INIS)

    Cavity formation in high purity aluminum has been explored with the controlled addition of helium gas. Aluminium specimens containing no helium and preinjected helium concentrations of 0.1, 1.0 and 10 at.ppm were irradiated with aluminum ions at 1000C to doses of 0.5 to 26 dpa. The helium preinjection was performed at room temperature (250C) by a controlled-thickness alpha particles source made from 244Cm oxide. All of the samples containing helium exhibited cavity formation while the aluminum containing no helium showed only vacancy loops and dislocation tangles. The microstructural effects observed were very heterogeneous and scattered in the irradiated aluminum even at the highest damage levels (26 dpa). The cavities were located in the vicinity of grain boundaries but no voids were observed on the grain boundaries themselves. Cavities were observed only in aluminum containing helium. (orig.)

  19. Vacancies in solid helium

    International Nuclear Information System (INIS)

    Some theoretical and experimental properties of thermally excited Schottky type vacancies in solid helium are reviewed: the mechanism for creation of a vacancy and the possibility for the latter to tunnel from one lattice site to a neighbouring one are considered. This tunnelling is compared with Pauli exchange interactions in solid 3He. The possibility of vacancy waves is studied and the difference between the cases of 3He and 4He pointed out. X ray scattering in body centered cubic helium three yields the energy of formation of vacancies without ambiguity in principle, although with a so far limited accuracy. Vacancy induced diffusion of magnetization in body centered cubic 3He is studied by the method of moments and existing experimental data are recalled. Spin lattice relaxation is recalled with some detail, both the Zeeman-vacancies relaxation due to the modulation of the dipole-dipole interactions by the motion of the vacancies and the exchange-lattice relaxation through the vacancies. The Zeeman-vacancies relaxation is studied by the method of moments, in parallel with the theory of diffusion. The exchange-lattice relaxation is calculated by the method of strong collisions of Ailion and Slichter. The various published experiments are reviewed. In the case of body centered cubic helium three, it can be concluded to the tunnelling of vacancies by comparison of NMR activation energies with the energies of formation measurgies with the energies of formation measured by X ray scattering. The case of the 3He impurities in hexagonal close packed 4He is also studied as it also reveals the existence of vacancies in 4He. Finally the possibility of inelastic scattering of either neutrons or light by vacancies is noted. It is not possible to detect directly by such an experiment the vacancy waves

  20. Helium II flow through and vapor separation by porous plugs

    International Nuclear Information System (INIS)

    The characteristics of liquid helium II flow through porous plugs with vapor on the downstream side have been studied and liquid/vapor phase separation by the plugs has been observed. Such a plug has been proposed for the containment of liquid helium in a low gravity environment. The plug automatically allows helium vapor venting under a heat load without liquid loss into an open vent line. Here, results are reported for a sintered nickel plug with 10 ?m diameter pores and for Al203 ceramic plugs with 10 ?m and 0.5 ?m pores. The helium flow rate through the plugs was measured for various heat inputs at temperatures between 1.5K and Tsub(lambda). (Auth.)

  1. Extreme ultraviolet spectroscopy of helium-hydrogen plasma

    International Nuclear Information System (INIS)

    Extreme ultraviolet spectroscopy was recorded on microwave discharges of helium with 2% hydrogen. Novel emission lines were observed with energies of q . 13.6 eV, q = 1, 2, 3, 7, 9, 11, or q . 13.6 eV, q = 4, 6, 8 less 21.2 eV corresponding to inelastic scattering of these photons by helium atoms due to excitation of He (1s2) to He (1s12p1). The average hydrogen atom temperature was measured to be 180-210 eV versus ?3 eV for pure hydrogen. The electron temperature Te for helium-hydrogen was 30 500 ± 5% K compared to 7400±5% K for pure helium. Known explanations for the novel series of spectral lines and extraordinary broadening were ruled out

  2. Simulation of liquid helium

    International Nuclear Information System (INIS)

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

  3. Helium pneumoperitoneum for laparoscopic cholecystectomy: ventilatory and blood gas changes.

    Science.gov (United States)

    McMahon, A J; Baxter, J N; Murray, W; Imrie, C W; Kenny, G; O'Dwyer, P J

    1994-07-01

    Laparoscopic cholecystectomy with carbon dioxide pneumoperitoneum may result in hypercarbia and acidosis in patients with cardiorespiratory disease. The aim of the present study was to assess helium as an alternative to carbon dioxide for creating the pneumoperitoneum. Ventilation requirements and carbon dioxide levels were assessed at the beginning and end of laparoscopic cholecystectomy using helium (n = 30) and carbon dioxide (n = 30) pneumoperitoneum. Insufflation with helium did not result in an increase in ventilation requirement although, like carbon dioxide pneumoperitoneum, it was associated with a mean rise in peak airway pressure (of 7 cmH2O; P helium (P = 0.006). Carbon dioxide pneumoperitoneum was associated with a significant rise in arterial carbon dioxide levels, despite increasing ventilation. Four patients with helium pneumoperitoneum had surgical emphysema for 5 days. Helium may be a suitable alternative to carbon dioxide for creating pneumoperitoneum in patients with severe cardiorespiratory disease. However, because of its low water solubility helium has a lower safety margin than carbon dioxide in the rare event of gas embolism. PMID:7922057

  4. 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.)

  5. Single electron loss by fast ions in helium

    International Nuclear Information System (INIS)

    The single electron loss cross section in collisions of B, N, Ne ions with helium atoms is calculated by plane wave Born approximation. The screening effect is taken into account as in approximation of a sum rule and by evaluation of amplitudes for 1 snl (n < 5, l < 2) excitation and ionization of helium. The calculation results are in the satisfactory agreement with experimental data

  6. First Principles Calculations of Shock Compressed Fluid Helium

    OpenAIRE

    Militzer, B.

    2006-01-01

    The properties of hot dense helium at megabar pressures were studied with two first-principles computer simulation techniques, path integral Monte Carlo and density functional molecular dynamics. The simulations predicted that the compressibility of helium is substantially increased by electronic excitations that are present in the hot fluid at thermodynamic equilibrium. A maximum compression ratio of 5.24(4)-fold the initial density was predicted for 360 GPa and 150000 K. T...

  7. 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

  8. Quantum cavitation in liquid helium

    OpenAIRE

    Guilleumas, Montserrat; Barranco Go?mez, Manuel; Jezek, Dora M.; Lombard, Roland J.; Pi Pericay, Marti?

    1996-01-01

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

  9. Phase and density dependence of the delayed annihilation of metastable antiprotonic helium atoms in gas, liquid and solid helium

    International Nuclear Information System (INIS)

    Systematic studies of the phase and density dependence of the delayed annihilation time spectra of antiprotons (DATS) in gaseous, liquid and solid helium have been performed using the Low Energy Antiproton Ring (LEAR) at CERN. The results show a small but significant dependence of DATS on the phase and density of the helium medium. The average lifetime of antiprotons (Tav) in gas at 10-30 K was found to be 4.03 ± 0.02 ?s. In liquid helium Tav decreases with density from 3.0 ?s at 1 bar to 2.5 ?s at 60 bar, while in solid helium its value is 2.14 ± 0.03 ?s, 20% shorter than that in liquid helium of the same density. There is no change of DATS between normal 1-bar liquid and superfluid helium. An isotope effect between 4He and 3He similar to the one previously observed in the gas phase has also been found for liquid helium. All the data can be fitted fairly well with a simple three-level chain decay model which describes the general structure of DATS, characterized by downward curving behavior on a logarithmic scale at later times and by the presence of a short-lived component. No delayed annihilation was observed in lithium. (author)

  10. 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

  11. Leak detection with liquid helium

    International Nuclear Information System (INIS)

    A method for approximately locating ultra-small leaks in a superconducting cyclotron magnet cryostat has been developed using liquid helium. A method for locating ultra-small leaks using cold helium gas (<,m 205K) has been reported. The cold gas method requires a means of varying the return path of the liquid helium boil-off gas to refrigerator. The main part of the MSU cryostat is inaccessible to temperature variations due to gas flow changes, which primarily occur at the top of the cryostat. In the main body of the cryostat there is the option of raising and lowering the liquid helium level, and it has been discovered that the location of the leak is clearly defined as it is covered (uncovered) by liquid helium. (orig.)

  12. Interstellar helium in the heliosphere

    Science.gov (United States)

    Müller, Hans-Reinhard; Bzowski, Maciej; Möbius, Eberhard; Zank, Gary P.

    2013-06-01

    Several years of neutral measurements by NASA/IBEX-Lo have yielded detailed observations of direct interstellar neutral helium (primary particles). Prior to IBEX, interstellar helium had been observed through UV backscattering, pickup ions, and directly by Ulysses-GAS. The IBEX measurements now also provide strong indications for the presence of secondary neutral helium that is thought to originate in the outer heliosheath from charge exchange. In order to model both primary and secondary particle populations and characterize them throughout the heliosphere, a detailed calculation method based on Keplerian orbits is used, and some sample results are presented. The helium velocity distribution functions throughout the heliosphere are characterized. In the inner heliosphere they exhibit an intricate structure, in particular downwind of the Sun where the helium focusing cone resides as well.

  13. 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).

  14. 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; N. C. Sturchio

    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...

  15. Central helium density measurements in PLT

    International Nuclear Information System (INIS)

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

  16. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-10-15

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

  18. Radiative lifetime measurement of the 3 1S, 3 1D, 4 1D, 4 1F, and 5 1F excited states of helium

    International Nuclear Information System (INIS)

    The lifetimes of the 3 1S, 3 1D, 4 1D, 4 1F, and 5 1F states of He have been determined experimentally to be 54.5 +- 0.8, 16.7 +- 0.8, 36.4 +- 1.2, 67 +- 10, and 142 +- 20 nesc, respectively. The measurements were made at several incident electron energies using a pulsed-electron time-delayed-coincidence technique

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

    International Nuclear Information System (INIS)

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

  20. 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.

  1. Photoionization of helium dimers

    International Nuclear Information System (INIS)

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

  2. 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)

  3. 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

  4. Mass distribution at moderate excitation energies: 28.5 MeV helium ion induced fission of 232Th [Paper No. NC-1

    International Nuclear Information System (INIS)

    Mass distribution in 30 MeV alpha particle induced fission of 232Th was studied using high resolution gamma spectrometry. The chain yields of thirteen mass chains were determined. The distribution was found to be asymmetric with peak to valley ratio of 5.3. The yields were compared with similar other fissioning systems reported in literature. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-03-01

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

  6. Random walk of helium bubbles in vanadium

    International Nuclear Information System (INIS)

    Helium bubbles will be generated in the first wall of any fusion reactor. These bubbles will either cause swelling and embrittlement in their own right or act as precursors to a population of voids, depending on the temperature and various irradiation and material parameters. Bubbles can, in principle, grow either by the re-solution and re-precipitation of the inert gas (ripening) or by migration and coalescence. We have studied the growth of bubbles arising from the room temperature implantation of helium to a concentration of 5 x 1026He/m3 in Vanadium. We demonstrate in this paper that during isothermal annealing at 950 deg C (0.55 Tsub(m)) faceted helium bubbles undergo Brownian motion and grow only by coalescence. No bubble was observed to shrink and hence ripening can be ruled out. The rate controlling process which limits the migration and hence growth rate at this temperature could be surface diffusion or the nucleation of ledges on bubble facets. We conclude both from our hot stage electron microscope observations and from isothermal annealing of bulk specimens that ledge nucleation is rate limiting even for bubbles less than 10 nm in size. The energy of a monatomic ledge on a brace 100 brace surface in Vanadium is deduced to lie between 3 and 5 x 10-11 J/m. (author)

  7. Indigenous development of helium liquefier

    International Nuclear Information System (INIS)

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

  8. Electronic properties of physisorbed helium

    Energy Technology Data Exchange (ETDEWEB)

    Kossler, Sarah

    2011-09-22

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

  9. Helium isotopes in energy exploration

    International Nuclear Information System (INIS)

    Helium isotope geochemistry is a new and rapidly developing research area with important applications in the field of earth resources. Natural variations in the helium isotopic ratio have a range in excess of 105; the wide variation is due to radioactive generation of each isotope in well-separated geochemical environments. Admixtures of tritium generated (atmospheric) 3He and ?-particle derived (crustal) 4He, provide a ready means of isotopic tracing with possible applications in the mineral exploration industry. The dispersion of helium isotopes in the near surface environment is an important indicator of uranium mineralization, of heavy mineral deposits, of oil and gas reservoirs and of hydrocarbon structure boundaries

  10. Discrete liquid helium level indicator

    International Nuclear Information System (INIS)

    Characteristics of liquid helium level indicators produced according to different procedUres from carbon-resistors of the ''Allen-Bredly'' company are presented. A change in the pick-up signal by 104% is attained during the vapour-liquid interface transition at heat release in liquid Wsub(liq.)not equal to 4.9 mW. The accuracy of the level determination is ?H<=2 mm. A six-position liquid helium level indicator enabling to reliably determine the liquid helium level under different operation conditions of the cryostat is described

  11. Electronic properties of physisorbed helium

    International Nuclear Information System (INIS)

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

  12. 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)

  13. 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

  14. Implanting helium into nanocrystalline hydrogen storage alloy

    International Nuclear Information System (INIS)

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

  15. Helium cooling of fusion reactors

    International Nuclear Information System (INIS)

    On the basis of worldwide design experience and in coordination with the evolution of the International Thermonuclear Experimental Reactor (ITER) program, the application of helium as a coolant for fusion appears to be at the verge of a transition from conceptual design to engineering development. This paper presents a review of the use of helium as the coolant for fusion reactor blanket and divertor designs. The concept of a high-pressure helium cooling radial plate design was studied for both ITER and PULSAR. These designs can resolve many engineering issues, and can help with reaching the goals of low activation and high performance designs. The combination of helium cooling, advanced low-activation materials, and gas turbine technology may permit high thermal efficiency and reduced costs, resulting in the environmental advantages and competitive economics required to make fusion a 21st century power source. ((orig.))

  16. Precision spectroscopy of antiprotonic helium

    OpenAIRE

    Widmann, Eberhard

    2007-01-01

    Antiprotonic helium, a neutral exotic three-body system consisting of a helium nucleus, an electron and an antiproton, is being studied at the Antiproton Decelerator of CERN by the ASAUCSA collaboration. Using laser spectroscopy of the energy levels of the antiproton in this system and comparison to theory, a value of the antiproton-to-electron mass ratio with an error of 3 ppb could be obtained. This result agrees with the most precise measurement of the value of the proton...

  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. 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)

  19. Cryogenic filter method produces super-pure helium and helium isotopes

    Science.gov (United States)

    Hildebrandt, A. F.

    1964-01-01

    Helium is purified when cooled in a low pressure environment until it becomes superfluid. The liquid helium is then filtered through iron oxide particles. Heating, cooling and filtering processes continue until the purified liquid helium is heated to a gas.

  20. Superfluid Helium Orbital Resupply Coupling

    Science.gov (United States)

    Ryder, M. O.; Morash, D. H.; Schoenberg, R. J.

    1989-01-01

    The resupply of superfluid helium to satellites and other space-based experiment packages can increase the useful longevity of these devices far beyond their present life expectancies which are many times determined by the supply of helium coolant. The transfer of superfluid helium to spacecraft in space will require a reusable coupling that functions at 1.8 Kelvin with little heat leak and low pressure drop. Moog has designed the Helium Resupply Coupling to meet these operational requirements. Initially, the coupling manual mode operation will be demonstrated on orbit by an EVA crew member during the Space Shuttle borne Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The ultimate application will use robotic (automatic) coupling operation to which the present design readily adapts. The utilization of Moog's exclusive Rotary Shut-Off (RSO) technology in the development of the Superfluid Helium Resupply Coupling is described. The coupling not only performs the function of a flow control valve and disconnect but also provides adequate safety features for a shuttle launched man-rated payload. In addition, the coupling incorporates the necessary features to provide the high thermal isolation of the internal flow path from the external environment.

  1. Development of ultrahigh pressure helium booster system

    International Nuclear Information System (INIS)

    Operation principle, design principle, fabrication and cautions in operation of ultrahigh pressure He booster system are introduced, and main parts selection method and high pressure seal design of the booster system are discussed. The as-developed system can output 300 MPa helium gas with (3.5 ? 5.0) x 10-7 Pa · m3/s leak rate through manual or automatic pressure boosting and keeping. Main function parameters of the system are accessed and compared with those of three congeneric systems. The result shows that the system was rationally designed with superior performance and safety, and the system would be used to test ICF microsphere filling DT system. (authors)

  2. Development of compact helium leak detector

    International Nuclear Information System (INIS)

    For long vacuum chambers, like booster ring, transport lines etc., leak hunting after assembly is very important and for this purpose, we have developed a compact helium leak detector cell with small radius of curvature (2.5 cm), very low accelerating voltage, (270 V), in-built pressure monitoring (in the range of 10-4 mbar to 10-5 mbar), and light weight due to ferrite magnets in place of Alnico magnets. In combination with an isolation valve, the analyzing cell becomes a part of the vacuum system, rendering its service, whenever required. (author). 2 figs

  3. Liquid helium vessel thermal heat load calculation and modification of the liquid helium cryostat for improved thermal performances

    International Nuclear Information System (INIS)

    A room temperature bore superconducting (SC) solenoid magnet has been developed at Control Instrumentation Division (CnID) for carrying out liquid PbLi Magneto Hydro Dynamic (MHD) and corrosion experimental studies for ITER TBM. The SC solenoid magnet is designed to generate central bore magnetic field of 4 Tesla in a bore diameter of 300 mm and length of 800 mm with a field uniformity of 0.5% or better. The SC magnet is made up of low temperature NbTi copper composite wire whose critical temperature (Tc) is 9.8 K. The SC magnet needs to be cooled to liquid helium temperature (4.2 K) for its stable operation. Considering the operational requirement, an adiabatically stable SC magnet is under development. The adiabatically cooled SC magnet is completely immersed inside the liquid helium vessel. As the latent heat of vaporisation of liquid helium is less, heat load on liquid helium vessel needs to be reduced. In this paper we discuss about the liquid helium cryostat developed with conduction cooled thermal shield. Various heat loads on the liquid helium cryostat is calculated. Design modification of the existing cryostat to reduce the heat load and improved thermal performance is discussed. (author)

  4. High temperature creep of a helium-implanted titanium aluminide alloy

    International Nuclear Information System (INIS)

    The creep properties of an intermetallic alloy Ti-46Al-2W-0.5Si (at%) including strain rate and time to fracture were investigated in vacuum using helium-implanted and non-implanted samples, at a temperature of 1073 K and a stress of 200 MPa. The implantation was performed using 24 MeV He-ions, homogeneously implanting the samples with up to 1333 appm (atomic parts per million) helium. The size and location of helium bubbles were determined with transmission electron microscopy (TEM). Samples implanted with helium content above 10 appm exhibited strong helium embrittlement, reducing both the time to fracture and the elongation at fracture. The corresponding critical helium bubble size rc was determined to 10 nm.

  5. Helium-cooled blanket designs

    International Nuclear Information System (INIS)

    A systematic selection and evaluation of helium-cooled blanket concepts has been performed as part of the Blanket Comparison and Selection Study (BCSS). Helium-cooled Li2O, lithium, LiAlO2/Be, and Flibe/Be blanket concepts were selected for detailed design and evaluation. These concepts are applicable to both tokamak and tandem mirror reactors (TMRs). The design and analysis of Li2O, lithium, and LiAlO2/Be blanket concepts are presented. Previous blanket designs were studied and the pressurized lobe configuration was selected for the helium-cooled BCSS designs. Fifty-four different combinations of structural, breeder, and neutron multiplier materials were considered and four helium-cooled blanket concepts were selected for detailed design and evaluation. Mechanical, thermal, and neutronic designs were developed, and tritium control methods were specified. In the final BCSS evaluation, the Li2O blanket design ranked second for tokamaks and third for TMRs. The lithium blanket design ranked third for tokamaks and fourth for TMRs. To help guide future research and development, the critical issues associated with each of the helium-cooled designs were identified and necessary experimental data highlighted. These data include irradiation behavior of the blanket materials, compatibility between the structure and liquid-metal breeder materials, and the behavior of tritium in a helium-cooled blanket environment. The designium-cooled blanket environment. The designs offer favorable performance, design simplicity, and attractive safety features for fusion reactors. Design improvements were identified that could allow still better performance of the helium-cooled blanket designs

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

    Science.gov (United States)

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

    2014-03-01

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

  7. 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

  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. Diffusion and retention of helium in titanium carbide

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-01

    The knowledge of helium migration in TiC is an important issue due to its possible use as fuel coating in fission reactors and as first wall material coating in fusion reactors. Helium release measurements and diffusion coefficient calculations of helium in polycrystalline TiC have been carried out in the temperature range (1000–1600 °C) for the time period of 2 h. Polished bars of TiC were implanted with 3 MeV {sup 3}He{sup +} ions in normal incidence at a dose of 5 × 10{sup 20} at./m{sup 2} at room temperature. Helium depth profile was measured at each step using the {sup 3}He(d, p{sub 0}){sup 4}He nuclear reaction by varying the incident deuteron energy from 900 to 1800 keV. Effective diffusion coefficients vary from 4.20 × 10{sup ?18} to 2.59 × 10{sup ?17} m{sup 2} s{sup ?1} and activation energy values obtained are in the range 0.8–2.5 eV. Due to scarce availability of stoichiometric TiC, challenges in this study came from native vacancies present in the samples. The helium distribution and its release were affected by the presence of grain boundaries. He is considered to undergo two distinct populations into the sample and different values of diffusion coefficient have been determined for each population.

  10. Diffusion and retention of helium in titanium carbide

    Science.gov (United States)

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

    2014-05-01

    The knowledge of helium migration in TiC is an important issue due to its possible use as fuel coating in fission reactors and as first wall material coating in fusion reactors. Helium release measurements and diffusion coefficient calculations of helium in polycrystalline TiC have been carried out in the temperature range (1000-1600 °C) for the time period of 2 h. Polished bars of TiC were implanted with 3 MeV 3He+ ions in normal incidence at a dose of 5 × 1020 at./m2 at room temperature. Helium depth profile was measured at each step using the 3He(d, p0)4He nuclear reaction by varying the incident deuteron energy from 900 to 1800 keV. Effective diffusion coefficients vary from 4.20 × 10-18 to 2.59 × 10-17 m2 s-1 and activation energy values obtained are in the range 0.8-2.5 eV. Due to scarce availability of stoichiometric TiC, challenges in this study came from native vacancies present in the samples. The helium distribution and its release were affected by the presence of grain boundaries. He is considered to undergo two distinct populations into the sample and different values of diffusion coefficient have been determined for each population.

  11. Diffusion and retention of helium in titanium carbide

    International Nuclear Information System (INIS)

    The knowledge of helium migration in TiC is an important issue due to its possible use as fuel coating in fission reactors and as first wall material coating in fusion reactors. Helium release measurements and diffusion coefficient calculations of helium in polycrystalline TiC have been carried out in the temperature range (1000–1600 °C) for the time period of 2 h. Polished bars of TiC were implanted with 3 MeV 3He+ ions in normal incidence at a dose of 5 × 1020 at./m2 at room temperature. Helium depth profile was measured at each step using the 3He(d, p0)4He nuclear reaction by varying the incident deuteron energy from 900 to 1800 keV. Effective diffusion coefficients vary from 4.20 × 10?18 to 2.59 × 10?17 m2 s?1 and activation energy values obtained are in the range 0.8–2.5 eV. Due to scarce availability of stoichiometric TiC, challenges in this study came from native vacancies present in the samples. The helium distribution and its release were affected by the presence of grain boundaries. He is considered to undergo two distinct populations into the sample and different values of diffusion coefficient have been determined for each population

  12. 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.

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

    Science.gov (United States)

    Lowenstern, J B; Evans, W C; Bergfeld, D; Hunt, A G

    2014-02-20

    Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents. The hydrothermal system at Yellowstone National Park is famous for its high helium-3/helium-4 isotope ratio, commonly cited as evidence for a deep mantle source for the Yellowstone hotspot. However, much of the helium emitted from this region is actually radiogenic helium-4 produced within the crust by ?-decay of uranium and thorium. Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Our results demonstrate the extremes in variability of crustal helium efflux on geologic timescales and imply crustal-scale open-system behaviour of helium in tectonically and magmatically active regions. PMID:24553240

  14. Helium transport and exhaust studies in enhanced confinement regimes in DIII-D

    International Nuclear Information System (INIS)

    A better understanding of helium transport in the plasma core and edge in enhanced confinement regimes is now emerging from recent experimental studies on DIII-D. Overall, the results are encouraging. Significant helium exhaust (?*He/?E ? 11) has been obtained in a diverted, ELMing H-mode plasma simultaneous with a central source of helium. 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. Perturbative helium transport studies using gas puffing have shown that DHe/Xeff?1 in all confinement regimes studied to date (including H-mode and VH-mode). Furthermore, there is no evidence of preferential accumulation of helium in any of these regimes. However, measurements in the core and pumping plenum show a significant dilution of helium as it flows from the plasma core to the pumping plenum. Such dilution could be the limiting factor in the overall removal rate of helium in a reactor system

  15. Helium isotopes in geothermal and volcanic gases of the Western United States, II. Long Valley Caldera

    Science.gov (United States)

    Welhan, J. A.; Poreda, R. J.; Rison, W.; Craig, H.

    1988-05-01

    Systematic trends in helium isotope ratios and gas compositions in Long Valley caldera hot-spring and fumarole gases reflect subsurface processes and conditions in the hydrothermal system. High {3He}/{4He} ratios (to 6.5 × atmospheric) indicate a magmatic helium source diluted to varying degrees by crustal radiogenic helium, as observed in western United States geothermal systems in general. Helium isotope ratios increase eastward across the caldera, which we interpret as an input of magmatic helium to the hydrothermal fluid as it flows eastward over the caldera. Decreasing He/condensible-gas (? He/CO 2) ratios accompanying this trend suggest that CO 2 addition and/or preferential helium loss due to boiling are also occurring, although near-surface, pH-related CO 2?HCO 3 equilibria obscure the nature of this effect. Substantial changes in {3He}/{4He} ratios were observed in Long Valley gases between 1978 and 1985. Helium isotope ratios increased by 15% in the Hot Creek thermal vent, with maximum ratios achieved in 1983. Helium isotope ratios subsequently decreased in this and other hot vents in the caldera. These observations indicate that substantial changes in the mixing ratio of radiogenic and magmatic helium may occur over relatively short periods of time in magmatically active systems.

  16. 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

  17. 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.

  18. 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

  19. Pierre Gorce working on a helium pump.

    CERN Multimedia

    1975-01-01

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

  20. Primary population of antiprotonic helium states

    OpenAIRE

    Re?vai, J.; Shevchenko, N. V.

    2003-01-01

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

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

    Science.gov (United States)

    2010-10-01

    ...2010-10-01 2010-10-01 false Required Sources for Helium and Helium Usage Data. 52.208-8 Section 52.208-8...Provisions and Clauses 52.208-8 Required Sources for Helium and Helium Usage Data. As prescribed in...

  2. The cosmic production of Helium

    CERN Document Server

    Jiménez, R; MacDonald, J; Gibson, B K; Jimenez, Raul; Flynn, Chris; Donald, James Mac; Gibson, Brad K.

    2003-01-01

    We estimate the cosmic production rate of helium relative to metals ($\\Delta Y/\\Delta Z$) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is $\\Delta Y/\\Delta Z=2.1 \\pm 0.4$ at the 68% confidence level. Our derived value agrees with determinations from HII regions and with theoretical predictions from stellar yields with standard assumptions for the initial mass function. The amount of helium in stars determines how long they live and therefore how fast they will enrich the insterstellar medium with fresh material.

  3. Electron Bubbles in Liquid Helium

    CERN Document Server

    McDonald, K T

    2003-01-01

    When an electron (or positronium atom) is injected into liquid helium with nearly zero energy, a bubble quickly forms around it. This phenomenon (which also occurs in liquid hydrogen, liquid neon and possibly in solid helium) lowers the mobility of the electron to a value similar to that for a positive ion. We estimate the radius of the bubble at zero pressure and temperature based on the zero point energy of the electron. If the liquid is held in a state of negative pressure, the bubble will expand beyond the radius at zero pressure. We also estimate the negative pressure such that a bubble once formed will grow without limit.

  4. 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.

  5. Electron Bubbles in Liquid Helium

    OpenAIRE

    Mcdonald, Kirk T.

    2003-01-01

    When an electron (or positronium atom) is injected into liquid helium with nearly zero energy, a bubble quickly forms around it. This phenomenon (which also occurs in liquid hydrogen, liquid neon and possibly in solid helium) lowers the mobility of the electron to a value similar to that for a positive ion. We estimate the radius of the bubble at zero pressure and temperature based on the zero point energy of the electron. If the liquid is held in a state of negative pressur...

  6. Reexamination of helium fine structure

    OpenAIRE

    Pachucki, K.; Yerokhin, V. A.

    2009-01-01

    In order to explain discrepancies between theoretical predictions and experimental data for the helium fine structure, we check and recalculate all theoretical contributions up to orders m\\alpha^7 and m^2/M\\alpha^6. The previous result for the m\\alpha^7 correction is improved by a much more accurate calculation of relativistic corrections to the Bethe logarithm. The theoretical values of the 2^3P_0-2^3P_1 and 2^3P_1-2^3P_2 fine structure intervals in helium are, correspondin...

  7. Diffraction of an atomic helium beam

    International Nuclear Information System (INIS)

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

  8. 30 CFR 256.11 - Helium.

    Science.gov (United States)

    2010-07-01

    ...2010-07-01 2010-07-01 false Helium. 256.11 Section 256.11 Mineral...Sulphur Management, General § 256.11 Helium. (a) Each lease issued or continued...the ownership of and the right to extract helium from all gas produced from the...

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

    International Nuclear Information System (INIS)

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

  10. A transient modeling of a helium turbine power system

    International Nuclear Information System (INIS)

    In this study, a transient performance simulation model of an indirect helium turbine cycle system is developed. One-dimension models are built to simulate the components, including helium turbine model, compressor model, heat exchanger model, valve model, duct model and shaft rotation model. The simulation code is established on MATLAB and the ordinary differential equations derived from component model are solved by the ode15s solvers of MATLAB. The accident of loss of load and the transient of decreasing heat transfer capacity of intermediate heat exchanger by 5% are simulated and analyzed. The analysis of calculated results validates the present model. (author)

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

    OpenAIRE

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

    2015-01-01

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

  12. Supercritical Helium Cooling of the LHC Beam Screens

    CERN Document Server

    Hatchadourian, E; Tavian, L

    1998-01-01

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

  13. 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)

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

    International Nuclear Information System (INIS)

    An absolute determination of the electron spin polarization of a GaAs photoemission source was made using the method of helium polarimetry. Measurements of the source polarization were also made using a Mott spin polarization analyser. We report an electron beam polarization of (25.5±1)% and an effective Sherman function of 0.26±0.01 for the Mott detector at 31.8±0.6 keV incident electron energy. The Sherman function is also presented for a number of incident energies between 10 keV and 37 keV. A complete set of Stoke's parameters is reported for the 33P-23S (3889 A) helium line. The characteristics of the source, Mott detector and helium polarimeter are discussed in detail. (author)

  15. 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.

  16. Ultrahigh vacuum facility with the helium cryocondensation pump

    International Nuclear Information System (INIS)

    Construction of ultrahigh vacuum equipment with a helium cryocondensation pump, designed for making ultrahigh-vacuum studies of films of various materials sprayed in this equipment, is described. The equipment consists of a serially connected, and constantly functioning in an operating regime, ultrahigh vacuum oil-vapor diffusion pump which gives a limiting vacuum of 10-9 to 10-10 mm Hg, at the outlet of which a vacuum of 10-5 to 10-6 mm Hg is maintained, and a helium cryocondensation pump with traps cooled with liquid helium and surrounded below with and above with nitrogen traps and followed by a chamber and chamber cryostat with sample holder. The limiting vacuum, reached in the receiver equipment, is better than 10-14 mm Hg. The body of all ultrahigh vacuum units may be heated to 5000C and cooled to 77 K. The equipment satisfies the requirements for ultrahigh vacuum cryogenic equipment with long continuous evacuation capability

  17. A continuous level-indicator for liquid helium

    International Nuclear Information System (INIS)

    In most cases of work involving liquid helium, continuous monitoring of the liquid level is a basic requirement. Conventional liquid-level indicators suffer from a number of defects - innaccurate detection, limitations as to permissible ambient conditions, complexity of calibration, and the fact that the detecting element cannot be replaced - which make such indicators unsatisfactory for industrial application. A new continuous level indicator without these defects has been constructed using a detecting element of Nb-Ti wires having the extremely small resistivity ratios of rho300K/rho10K=1.07 and rho10K/rho77K=0.975. Standard specifications of the element are: measuring length 400mm, outside diameter 5mm, weight 20g, and a heat loss in liquid helium of zero and in gaseous helium of 0.02 W/cm. (auth.)

  18. Two phase coexistence for the hydrogen-helium mixture

    CERN Document Server

    Fantoni, Riccardo

    2015-01-01

    We use our newly constructed quantum Gibbs ensemble Monte Carlo algorithm to perform computer experiments for the two phase coexistence of a hydrogen-helium mixture. Our results are in quantitative agreement with the experimental results of C. M. Sneed, W. B. Streett, R. E. Sonntag, and G. J. Van Wylen. The difference between our results and the experimental ones is in all cases less than 15% relative to the experiment, reducing to less than 5% in the low helium concentration phase. At the gravitational inversion between the vapor and the liquid phase, at low temperatures and high pressures, the quantum effects become relevant. At extremely low temperature and pressure the first component to show superfluidity is the helium in the vapor phase.

  19. Cryopumping of hydrogen and helium

    International Nuclear Information System (INIS)

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

  20. 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

  1. Production of negative helium ions

    International Nuclear Information System (INIS)

    A negative helium ion source using potassium charge exchange vapor has been developed to be used as an injector for the Pelletron accelerator. 3He and ? beam currents of up to 2?A have been extracted with 75% particle transmission through the machine

  2. Internally-cooled cabled superconductors cooled with helium II

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-03-01

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

  4. Helium embrittlement of a lamellar titanium aluminide

    International Nuclear Information System (INIS)

    Embrittlement by helium was investigated in a lamellar TiAl alloy under two conditions: (a)Specimens were implanted to various amounts of helium up to 762 appm at temperatures from 630 °C to 1000 °C and some of them subsequently creep-tested at the same temperature under stresses from 150 to 300 MPa. The microstructure and fracture surfaces of creep-deformed and non-creep-deformed specimens were then studied by transmission electron microscopy (TEM) and by scanning electron microscopy (SEM), respectively. (b)Specimens were implanted to various amounts of helium at a low temperature (150 °C) and post-implantation annealed at elevated temperatures for TEM studies. Embrittlement was revealed by reduction in time- and strain-to-rupture and by a transition in fracture surface from ductile to an inter-lamellar appearance. Embrittlement occurred above a critical He concentration, which decreased from about 10 appm at 700 °C to below 6 appm at 900 °C. TEM showed that embrittlement could be associated to reaching a critical bubble diameter of about 5 nm. Bubble diameters increased with increasing temperature ranging in high-temperature implanted specimens from about 3 nm (630 °C) to 20 nm (1000 °C) and in post-implantation annealed ones from 1.2 nm (600 °C) to 2.2 nm (900 °C), respectively. With increasing temperature, the bubble distribution grew less homogenous with a lower density of larger bubbles situated preferentially at interfaces and sinks. This was ascribed to a change in bubble nucleation mode from homogeneous di-atomic nucleation at lower temperatures to multi-atomic nucleation at sinks at higher temperature

  5. 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

  6. 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.

  7. 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...

  8. Simplicity works for superfluid helium

    International Nuclear Information System (INIS)

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently bpuzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  9. Simplicity works for superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bowley, Roger [University of Nottingham, Nottingham (United Kingdom)

    2000-02-01

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  10. Helium production in natural gas reservoirs

    International Nuclear Information System (INIS)

    About 11,000 published natural gas analyses of helium are used in the estimation of the average global scale accumulation and concentration of radiogenic helium in sediments. Simple lognormal statistics is employed to derive a net accumulation rate between 1dagger105 to 6.7dagger105 helium atoms per cubic meter of reservoir rock per second. This acccumulation rate permitted to infer an average helium concentration of nonreservoir sediments of about 67 ppm. By assuming a simple closed system model it is shown that deep seated sources of helium are not necessary to explain the present regime of helium in sediments on a global scale. Helium accumulation rates and concentrations obtained by this method are in close agreement with existing fundamental geochemical estimates of uranium and thorium in rather average type sediments

  11. 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 ...

  12. 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...

  13. Vanadium alloys with improved resistance to helium embrittlement

    International Nuclear Information System (INIS)

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

  14. 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.)

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

    International Nuclear Information System (INIS)

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

  16. 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.

  17. 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)

  18. Muon transfer from deuterium to helium

    CERN Document Server

    Augsburger, M A; Breunlich, W H; Cargnelli, M; Chatellard, D; Egger, J P; Gartner, B; Hartmann, F J; Huot, O; Jacot-Guillarmod, R; Kammel, P; King, R; Knowles, P; Kosak, A; Lauss, B; Marton, J; Mühlbauer, M; Mulhauser, F; Petitjean, C; Prymas, W; Schaller, L A; Schellenberg, L; Schneuwly, H; Tresch, S; Von Egidy, T; Zmeskal, J

    2003-01-01

    We report on an experiment at the Paul Scherrer Institute, Villigen, Switzerland measuring x rays from muon transfer from deuterium to helium. Both the ground state transfer via the exotic dmu3,4He* molecules and the excited state transfer from mud* were measured. The use of CCD detectors allowed x rays from 1.5 keV to 11 keV to be detected with sufficient energy resolution to separate the transitions to different final states in both deuterium and helium. The x-ray peaks of the dmu3He* and dmu4He* molecules were measured with good statistics. For the D2+3He mixture, the peak has its maximum at E_dmu3He = 6768 +- 12 eV with FWHM Gamma_dmu3He = 863 +- 10 eV. Furthermore the radiative branching ratio was found to be kappa_dmu3He = 0.301 +- 0.061. For the D_2+4He mixture, the maximum of the peak lies at E_dmu4He = 6831 +- 8 eV and the FWHM is Gamma_dmu4He = 856 +- 10 eV. The radiative branching ratio is kappa_dmu4He = 0.636 +- 0.097. The excited state transfer is limited by the probability to reach the deuterium...

  19. Absolute calibration of TFTR helium proportional counters

    International Nuclear Information System (INIS)

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

  20. Negative helium charge exchange ion source

    International Nuclear Information System (INIS)

    A high intensity positive ion beam which comes from duoplasmatron is focused through a tube with a small diameter. At the center of this canal a controlled lithium metal vapor brings about the pressure in the canal, under which the negative helium beam can be produced. Incident ions pick up electrons from collisions with the lithium metal vapor and a fraction is changed into ions with a net negative charge. Undesirable ions and neutral particles are eliminated by the analyzing magnet. The authors have got initial results of 2.5 microampere of He- ions. The efficiency of charge exchange is about 0.5%?1% and the optimum temperature is ?700 degree C

  1. Towards helium-3 neutron polarizers

    International Nuclear Information System (INIS)

    With a large absorption cross-section entirely due to antiparallel spin capture, polarized helium-3 is presently the most promising broad-band polarizer for thermal and epithermal neutrons. Immediate interest was raised amongst the neutron community when a dense gaseous 3He polarizer was used for the first time in 1988, on a pulsed neutron beam at Los Alamos. With 20 W of laser power on a 30 cm long, 8.6 atm target, 40% 3He polarization was achieved in a recent polarized electron scattering experiment at SLAC. In this technique the 3He nuclei are polarized directly at an appropriate high pressure through spin-exchange collisions with a thick, optically pumped rubidium vapor. A different and competitive approach is being presently developed at Mainz University in collaboration with ENS Paris and now the ILL. A discharge is established in pure 3He at low pressure producing excited metastable atoms which can be optically pumped with infra-red light. Highly effective exchange collision with the atoms remaining in the ground state quickly produces 75% polarization at 1.5 mbar. A truly non-magnetic system then compresses the polarized gas up to several bars as required. The most recent machine comprises a two-stage glass-titanium compressor. In less than 1 h it can inflate a 100 cm3 target cell with three bars of polarized gas. The very long relaxation times (several days) now being obtained at high pressure with a speceing obtained at high pressure with a special metallic coating on the glass walls, the polarized cell can be detached and inserted in the neutron beam as polarizer. We expect 50% 3He-polarization to be reached soon, allowing such filters to compete favorably with existing Heusler-crystal polarizers at thermal and short neutron wavelengths. It must be stressed that such a system based on a 3He polarization factory able to feed several passive, transportable, polarizers is well matched to neutron scattering needs. (orig.)

  2. 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.

  3. 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.

  4. Superfluid helium leak sealant study

    Science.gov (United States)

    Vorreiter, J. W.

    1981-01-01

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

  5. Confined helium on Lagrange meshes

    CERN Document Server

    Baye, Daniel

    2015-01-01

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

  6. 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.

  7. Isolating electrons on superfluid helium

    OpenAIRE

    Takita, Maika; Lyon, S. A.

    2014-01-01

    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 $10^9$ 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 ...

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

    OpenAIRE

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

    2015-01-01

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

  9. 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

  10. Some effects of preinjected helium and irradiation temperature in void formation in aluminum irradiated with aluminum ions

    International Nuclear Information System (INIS)

    To observe the effect of helium and temperature on void formation in aluminum, high-purity foils were irradiated with 1.2- or 1.4-MeV Al+ ions at temperatures from 30 to 1200C, both with and without preinjected helium. Dislocation loops formed in all samples, but the samples without helium produced no voids visible in the transmission electron microscope even after doses up to 2.7 displacements per atom (dpa) (6.5 x 1015 Al+/cm2). Samples preinjected with 0.1, 1, and 10 appM helium and then irradiated at 100 and 1200C produced voids at doses of approximately 0.5 dpa (1.2 x 1015 Al+/cm2). With irradiation at 750C and below, voids formed only in samples preinjected with 0.1 appM helium. With irradiation at 1000C, the average void sizes and void densities were not significantly different for the three helium levels, whereas at 1200C the average void size decreased with increasing helium content and the density increased. With helium levels of 0.1 and 1 appM helium, varying the temperature produced an increase in void size with increasing temperature and a decrease in void density

  11. Tritium-helium effects in metals

    International Nuclear Information System (INIS)

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

  12. Helium diffusion in nickel at high temperatures

    International Nuclear Information System (INIS)

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

  13. Helium enrichment during convective carbon dioxide dissolution

    Science.gov (United States)

    Larson, T.; Hesse, M. A.

    2013-12-01

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

  14. Pair Correlations in Superfluid Helium 3

    OpenAIRE

    Vollhardt, D.

    1997-01-01

    In 1996 Lee, Osheroff and Richardson received the Nobel Prize for their 1971 discovery of superfluid helium 3 -- a discovery which opened the door to the most fascinating system known in condensed matter physics. The superfluid phases of helium 3, originating from pair condensation of helium 3 atoms, turned out to be the ideal test-system for many fundamental concepts of modern physics, such as macroscopic quantum phenomena, (gauge-)symmetries and their spontaneous breakdown...

  15. 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...

  16. Helium leak testing methods in nuclear applications

    International Nuclear Information System (INIS)

    Helium mass-spectrometer leak test is the most sensitive leak test method. It gives very reliable and sensitive test results. In last few years application of helium leak testing has gained more importance due to increased public awareness of safety and environment pollution caused by number of growing chemical and other such industries. Helium leak testing is carried out and specified in most of the critical area applications like nuclear, space, chemical and petrochemical industries

  17. 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

  18. Spectroscopy and dynamics in helium nanodroplets

    OpenAIRE

    Stienkemeier, Frank; Lehmann, Kevin K.

    2006-01-01

    This article provides a review of recent work in the field of helium nanodroplet spectroscopy with emphasis on the dynamical aspects of the interactions between molecules in helium as well as their interaction with this unique quantum solvent. Emphasis is placed on experimental methods and studies introducing recent new approaches, in particular including time-resolved techniques. Corresponding theoretical results on the energetics and dynamics of helium droplets are also di...

  19. Capture of slow antiprotons by helium atoms

    OpenAIRE

    Revai, J.; Shevchenko, N. V.

    2004-01-01

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

  20. Radioactive transitions in the helium isoelectronic sequence

    Science.gov (United States)

    Dalgarno, A.

    1971-01-01

    The principles of the atomic spectrum theory are used to quantitatively analyze radiation transitions in two-electron helium-like atomic systems. Quantum theoretical methods, describing absorption and emission of a single photon in a radiative transition between two stationary states of an atomic system, reproduced the energy level diagram for the low lying states of helium. Reliable values are obtained from accurate variationally determined two-electron nonrelativistic wave functions for radiative transition probabilities of 2 3p states in the helium isoelectric sequence, and for the 2 1s and 2 3s1 states of the helium sequence.

  1. 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

  2. The Liquefaction of Hydrogen and Helium Using Small Coolers

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Thiering, Russell; Taylor, David; Lu, Weijian

    2012-06-01

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

  4. The spectral shapes of hydrogen and helium nuclei in cosmic rays

    Science.gov (United States)

    Erlykin, A. D.; Wolfendale, A. W.

    2015-07-01

    The latest measurements of the energy spectra of protons and helium nuclei show with confidence that there is a significant difference in the shapes, with the proton spectrum being steeper than that of helium. The ratio of the proton to helium intensities falls in the energy range from 30 GeV (where solar modulation ceases) to the maximum energy (as measured) of about 1000 GeV by a factor of ? 1.5. The reason for the difference is sought, here, and some possibilities are put forward, of which we consider that the different radial distance from the centre of supernovae, of the elements to be accelerated, is the most likely.

  5. 21 CFR 868.1640 - Helium gas analyzer.

    Science.gov (United States)

    2010-04-01

    ... 2010-04-01 2010-04-01 false Helium gas analyzer. 868.1640 Section 868...DEVICES Diagnostic Devices § 868.1640 Helium gas analyzer. (a) Identification. A helium gas analyzer is a device intended to...

  6. Experimental loop for tests of helium-cooled HHF components at 600 C/10 MPA input

    International Nuclear Information System (INIS)

    The Efremov Institute has completed the 1st stage of helium loop construction. This work has been carried out in collaboration with FZK. The helium loop is intended for tests of divertor design options, which meet the requirements for the DEMO helium-cooled fusion reactor. These tests include selection of divertor materials and joining technology, optimization of the cooling regimes, thermal cycling of mockups to estimate the divertor component lifetime. It is also possible to use the loop in other areas of high-temperature helium nuclear technology (tests of first wall mock-ups, fission helium reactors relevant experiments). On the basis of the results of the systematic mock-ups tests it is planned to create the database for validation of the gas-dynamic and thermal mechanic codes used for simulation of processes in high-heat-flux components. The helium loop is capable of testing the mock-ups at a nominal helium input temperature of 600 C and a pressure of 10 MPa. Maximum possible pressure losses in mock-ups amount to 0.5 MPa. At this stage of works a stationary helium flow rate of 24 g/s is provided by oil-free membrane compressor. One more possible loop regime is by periodic gas pulses at 50 g/s and duration up to 120 s. The diagnostic system provides measurement of more than 40 gas and mock-up parameters such as pressure, flow rate and temperature, as well the surface temperature distribution by an infra-red camera. Mock-up heat loading is provided by the e-beam op heat loading is provided by the e-beam of the TSEFEY facility with an applied power of 60 kW. The testing results of singlefinger mock-ups of the vertical target for the DEMO helium-cooled divertor are presented. At the next stage the helium loop will be capable of attaining a flow rate of 150 g/s (using a helium circulating pump), which is sufficient for tests of nine-finger modules of the DEMO helium-cooled divertor. Some preliminary design simulations have been made in order to assess the hot pump performance for different pump types. As result of these simulations a vortex-type pump has been chosen and its design has been adapted to the helium loop requirements. Preliminary experiments have been carried out with a simplified model and drive in order to verify the accepted solutions. The design solutions and R and D results of the activities at this stage of loop development are also presented. (orig.)

  7. Interaction of Helium Rydberg State Atoms with Superfluid Helium

    Science.gov (United States)

    Fiedler, Steven L.; Eloranta, Jussi

    2014-03-01

    The pair potentials between ground state helium and Rydberg He atoms are calculated by the full configuration interaction electronic structure method for both the electronic singlet and the triplet manifolds. The obtained pair potentials are validated against existing experimental molecular and atomic data. Most states show remarkable energy barriers at long distances ( Å), which can effectively stabilize He against the formation of He at low nuclear kinetic energies. Bosonic density functional theory calculations, based on the calculated pair potential data, indicate that the triplet ground state He reside in spherical bubbles in superfluid helium with a barycenter radius of 6.1 Å at the liquid saturated vapor pressure. The pressure dependency of the relative He absorption line blue shift in the liquid was obtained through both the statistical line broadening theory as well as the dynamic adiabatic following method. The pronounced difference between the results from the static and dynamic models is attributed to the dynamic Jahn-Teller effect that takes places in the electronically excited state within the dephasing time of 150 fs. Transient non-thermalized liquid surroundings near He may contribute to an artificial reduction in the absorption line blue shift by up to 30 cm.

  8. 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...

  9. Helium bubble bursting in tungsten

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-28

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

  10. Excitations of amorphous solid helium

    OpenAIRE

    Bossy, Jacques; Ollivier, Jacques; Schober, Helmut; Glyde, Henry R.

    2012-01-01

    We present neutron scattering measurements of the dynamic structure factor, $S(Q,\\omega)$, of amorphous solid helium confined in 47 $\\AA$ pore diameter MCM-41 at pressure 48.6 bar. At low temperature, $T$ = 0.05 K, we observe $S(Q,\\omega)$ of the confined quantum amorphous solid plus the bulk polycrystalline solid between the MCM-41 powder grains. No liquid-like phonon-roton modes, other sharply defined modes at low energy ($\\omega$ 1 K), the amorphous solid in the MCM-41 po...

  11. 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

  12. 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 ...

  13. 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)

  14. 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)

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

    International Nuclear Information System (INIS)

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

  16. Spectroscopy of antiprotonic helium atoms and its contribution to the fundamental physical constants

    OpenAIRE

    Hayano, Ryugo S.

    2010-01-01

    Antiprotonic helium atom, a metastable neutral system consisting of an antiproton, an electron and a helium nucleus, was serendipitously discovered, and has been studied at CERN’s antiproton decelerator facility. Its transition frequencies have recently been measured to nine digits of precision by laser spectroscopy. By comparing these experimental results with three-body QED calculations, the antiproton-to-electron massratio was determined as 1836.152674(5). This result contributed to the CO...

  17. Determining the antiproton magnetic moment from measurements of the hyperfine structure of antiprotonic helium

    OpenAIRE

    Bakalov, Dimitar; Widmann, Eberhard

    2006-01-01

    Recent progress in the spectroscopy of antiprotonic helium has allowed for measuring the separation between components of the hyperfine structure (HFS) of the (37,35) metastable states with an accuracy of 300 MHz, equivalent to a relative accuracy of 3x10^{-5}. The analysis of the uncertainties of the available theoretical results on the antiprotonic helium HFS shows that the accuracy of the value of the dipole magnetic moment of the antiproton (currently known to only 0.3 %...

  18. Helium-ion-induced release of hydrogen from graphite

    International Nuclear Information System (INIS)

    The ion-induced release of hydrogen from AXF-5Q graphite was studied for 350-eV helium ions. The hydrogen was implanted into the graphite with a low energy (?200 eV) and to a high fluence. This achieved a thin (?10-nm), saturated near-surface region. The release of hydrogen was measured as a function of helium fluence. A model that includes ion-induced detrapping, retrapping, and surface recombination was used to analyze the experimental data. A value of (1.65 +- 0.2) x 10-16 cm2 was obtained from the detrapping cross section, and a value of (0.5 to 4) x 10-14 cm4/atoms was obtained for the recombination coefficient. 11 refs., 4 figs

  19. 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)

  20. Nuclear fusion and the helium supply problem

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, A.M., E-mail: alex.bradshaw@ipp.mpg.de [Max Planck Institute for Plasma Physics, Association IPP-Euratom, Boltzmannstr. 2, 85741 Garching (Germany); Fritz Haber Institute of the Max Planck Society, Faradayweg 4-6, 14195 Berlin (Germany); Hamacher, T. [Institute for Energy Economy and Application Technology, Technical University of Munich, Arcisstrasse 21, 80333 München (Germany)

    2013-10-15

    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.

  1. Dielectronic recombination of the helium ion

    International Nuclear Information System (INIS)

    Dielectronic recombination of the helium ion under conditions of intersecting beams is observed for the first time. Two peaks are observed in the energy dependence of the cross section of the process. The dielectronic recombination cross section is comparable to the cross section for excitation of the resonant level of the helium ion

  2. Leak detection with a helium mass spectrometer

    International Nuclear Information System (INIS)

    This article describes the latest two developments of mass spectrometers: 1) a ''counter flow'' spectrometers allowing for a shorter test cycle without having to use liquid nitrogen traps, and 2) a probe apparatus for testing a large volume object pressurized from the inside with helium or an air-helium mixture

  3. Helium leak detection in power stations

    International Nuclear Information System (INIS)

    Helium leak detection in power stations has several advantages: 1. Localisation of leakages; 2. Helium is non-toxic and non-inflammable and can detect very small leak rates owing to the low background in atmospheric air; 3. quantifiable and reproducible leakage rates can be measured. (orig.)

  4. Helium Speech: An Application of Standing Waves

    Science.gov (United States)

    Wentworth, Christopher D.

    2011-01-01

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

  5. LOX Tank Helium Removal for Propellant Scavenging

    Science.gov (United States)

    Chato, David J.

    2009-01-01

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

  6. 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.

  7. Two Photon Absorption Laser Induced Fluorescence of Helium Ions in a Microwave Assisted Helicon Source

    Science.gov (United States)

    Scime, Earl

    2014-10-01

    The spectroscopic measurement of helium ion velocity distribution functions in a low temperature plasma is problematic for a number of reasons. First and foremost is the difficulty in accessing the UV and soft x-ray transitions to the ground state. Conventional laser induced fluorescence on ions in plasmas is routinely performed in argon, neon, xenon, and barium. Two-photon absorption laser induced fluorescence (TALIF) on neutrals has been demonstrated in hydrogen, nitrogen, and oxygen plasmas. We have successfully performed LIF on helium atoms and have had some hints of success with laser absorption spectroscopy on excited states of helium ions, the n = 5 to n = 6 transition in the infrared (1012 nm). Here we report a new approach using TALIF to access the n = 2 to n = 6 transition of singly ionized helium. The fluorescence path at 656 nm completes the three-level sequence. To obtain the electron temperatures necessary to create a sufficient population of metastable helium ions trapped in the 2S state, we have increased the electron temperature of a helicon plasma with 1.2 kW of microwaves at 2.45 GHz. Here we report emission spectroscopy measurements that confirm the increase in excited state population densities and preliminary TALIF measurements on helium ions. The spectroscopic measurement of helium ion velocity distribution functions in a low temperature plasma is problematic for a number of reasons. First and foremost is the difficulty in accessing the UV and soft x-ray transitions to the ground state. Conventional laser induced fluorescence on ions in plasmas is routinely performed in argon, neon, xenon, and barium. Two-photon absorption laser induced fluorescence (TALIF) on neutrals has been demonstrated in hydrogen, nitrogen, and oxygen plasmas. We have successfully performed LIF on helium atoms and have had some hints of success with laser absorption spectroscopy on excited states of helium ions, the n = 5 to n = 6 transition in the infrared (1012 nm). Here we report a new approach using TALIF to access the n = 2 to n = 6 transition of singly ionized helium. The fluorescence path at 656 nm completes the three-level sequence. To obtain the electron temperatures necessary to create a sufficient population of metastable helium ions trapped in the 2S state, we have increased the electron temperature of a helicon plasma with 1.2 kW of microwaves at 2.45 GHz. Here we report emission spectroscopy measurements that confirm the increase in excited state population densities and preliminary TALIF measurements on helium ions. This work is funded by the US Department of Energy through Grant DE-SC0004736.

  8. 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.

  9. Primordial helium and the cosmic background radiation

    International Nuclear Information System (INIS)

    The products of primordial nucleosynthesis, along with the cosmic microwave background (CMB) photons, are relics from the early evolution of the Universe whose observations probe the standard model of cosmology and provide windows on new physics beyond the standard models of cosmology and of particle physics. According to the standard, hot big bang cosmology, long before any stars have formed a significant fraction ( ? 25%) of the baryonic mass in the Universe should be in the form of helium-4 nuclei. Since current observations of 4He are restricted to low redshift regions where stellar nucleosynthesis has occurred, an observation of high redshift, prestellar, truly primordial 4He would constitute a fundamental test of the hot, big bang cosmology. At recombination, long after big bang nucleosynthesis (BBN) has ended, the temperature anisotropy spectrum imprinted on the CMB depends on the 4He abundance through its connection to the electron density and the effect of the electron density on Silk damping. Since the relic abundance of 4He is relatively insensitive to the universal density of baryons, but is sensitive to a non-standard, early Universe expansion rate, the primordial mass fraction of 4He, Yp, offers a test of the consistency of the standard models of BBN and the CMB and, provides constraints on non-standard physics. Here, the WMAP seven year data (supplemented by other CMB experiments), which lead to an indirect determination of Yp at high redshift, are compared to the BBN predictions and to the independent, direct observations of 4He in low redshift, extragalactic HII regions. At present, given the very large uncertainties in the CMB-determined primordial 4He abundance (as well as for the helium abundances inferred from HII region observations), any differences between the BBN predictions and the CMB observations are small, at a level ?<1.5?

  10. 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.

  11. Free molecule drag on helium clusters

    International Nuclear Information System (INIS)

    This paper takes observation of free molecules drag coefficients below 2 for helium clusters of either isotope to indicate quantum fluid inviscity of the helium microdroplets. Inviscity means that the Knudsen number vanishes also for atomic projectiles. The helium fluid moves as a structureless contimuum even at very small dimensions. It is shown that the helium clusters must be so cold that with both isotopes the helium atoms do not move more independently but as a coherent quantum state. Viscosity then results only from the residual thermal excitations which form a gas of independent quasiparticles. Within the small cluster volume, however, there are only very few of them left at sufficiently low temperatures, and the viscosity vanishes as a result of the quasiparticle rarefaction

  12. 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.

  13. 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)

  14. 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

  15. Superfluid helium as a technical coolant

    CERN Document Server

    Lebrun, P

    1997-01-01

    The characteristics of superfluid helium as a technical coolant, which derive from its specific transport properties, are presented with particular reference to the working area in the phase diagram (saturated or pressurised helium II). We then review the principles and scaling laws of heat transport by equivalent conduction and by forced convection in pressurised helium II, thus revealing intrinsic limitations as well as technological shortcomings of these cooling methods. Once properly implemented, two-phase flow of saturated helium II presents overwhelming advantages over the previous solutions, which dictated its choice for cooling below 1.9 K the long strings of superconducting magnets in the Large Hadron Collider (LHC), a 26.7 km circumference particle collider now under construction at CERN, the European Laboratory for Particle Physics near Geneva (Switzerland). We report on recent results from the ongoing research and development programme conducted on thermohydraulics of two-phase saturated helium II...

  16. 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

  17. Atmospheric helium isotope ratio: Possible temporal and spatial variations

    Science.gov (United States)

    Sano, Yuji; Furukawa, Yukiko; Takahata, Naoto

    2010-09-01

    The atmospheric 3He/ 4He ratio has been considered to be constant on a global scale, because the residence time of helium is significantly longer than the mixing time in the atmosphere. However, this ratio may be decreasing with time owing to the anthropogenic release of crustal helium from oil and natural gas wells, although this observation has been disputed. Here, we present the 3He/ 4He ratios of old air trapped in historical slags in Japan and of modern surface air samples collected at various sites around the world, measured with a newly developed analytical system. In air helium extracted from metallurgical slag found at refineries in operation between AD 1603 and 1907 in Japan, we determined a mean 3He/ 4He ratio of (5106 ± 108) × 10 -5 R HESJ (where R HESJ is the 3He/ 4He ratio of the Helium Standard of Japan), which is consistent with the previously reported value of (5077 ± 59) × 10 -5 R HESJ for historical slags in France and United Arab Emirates and about 4% higher than that of average modern air, (4901 ± 4) × 10 -5 R HESJ. This result implies that the air 3He/ 4He ratio has decreased with time as expected by anthropogenic causes. Our modern surface air samples revealed that the 3He/ 4He ratio increases from north to south at a rate of (0.16 ± 0.08) × 10 -5 R HESJ/degree of latitude, suggesting that the low 3He/ 4He ratio originates in high-latitude regions of the northern hemisphere, which is consistent with the fact that most fossil fuel is extracted and consumed in the northern hemisphere.

  18. Monte Carlo simulations of neon versus helium ion beam induced deposition, sputtering and etching

    Science.gov (United States)

    Timilsina, Rajendra; Smith, Daryl; Rack, Philip

    2013-03-01

    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 the both simulations. Notably, the helium pillars are dominated by SE-I electrons whereas the neon pillars 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 (10ms) 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 the both ion types. However, the helium has the larger SE yield as compared to that of neon in the both low and high precursor residence time, and thus pillars are wider in all the simulations studied.

  19. 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)

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

    Science.gov (United States)

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

    2013-03-01

    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.

  1. 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)

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

    International Nuclear Information System (INIS)

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

  3. Shape of atomic lines emitted by cryoplasma in Helium

    International Nuclear Information System (INIS)

    Experimental data on spectral shape of the line 706nm emitted by corona discharge in liquid and gaseous cryogenic helium are presented. The data have their explanation in a frame work of the bubble model. The long-range interaction between excited He* atoms and He atoms in the ground state was used for a description of the fluorescence measurements. The 'hump' like repulsive part of the inter-atomic potential at intermediate internuclear separations around 5 Å was calculated by using the full configuration interaction method as implemented in the MOLPRO code. The repulsion gives rise to the establishment of cavities around excited atoms in liquid helium and radius and profiles of the cavity boundaries were calculated for this potential and different pressures. The potential was used to simulate the atomic line fluorescence profile as a function of external pressure between 0.1 and 3.5 MPa. The fluorescence shows characteristic line shifts and widths as a function of pressure. By comparison with the theoretical predictions, we found evidence that for corona discharge-excited liquid helium the He* atoms reside in a cavity and hence emit from within the liquid phase. The measurements carried out at higher temperature 5.1K give spectra are characterised for the bubble states similar to the states were obtained in superfluid He II at 1.8 K

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

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

  7. Effects of dislocations on thermal helium desorption from nickel and iron

    International Nuclear Information System (INIS)

    Helium atoms in metals have a strong tendency to accumulate at defects. Unfortunately, the experimental identification of the trapping sites of helium atoms is difficult. In this paper, the effects of dislocations on the trapping and desorption of helium atoms in nickel and iron were studied by thermal desorption spectroscopy. Defects were introduced in well-annealed high-purity metals by cold rolling. Positron annihilation spectroscopy was carried out to identify defects by measuring the positron lifetime before annihilation with various defects. The trapping and desorption of helium atoms at dislocations were investigated by implantation with low-energy He+ ions, both without irradiation damage (0.1 keV or 0.15 keV) and with irradiation damage (5.0 keV).

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

    International Nuclear Information System (INIS)

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

  9. 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.

  10. Effect of weld thermal cycle and restraint stress on helium bubble formation in stainless steels

    International Nuclear Information System (INIS)

    Helium bubble structure was examined in helium-implanted stainless steels after applying thermal cycles and tensile stresses using a weld thermal and stress cycle simulator. SUS304 specimens implanted with helium ions to 5 appm were heated at 1473 K for 2 s in an argon gas atmosphere. The heat-up rate and cooling rate were controlled to be 90 and 130 K/s, respectively. Tensile stresses ranging from 0 to 4 MPa were applied immediately after reaching a temperature of 1473 K. TEM observation revealed that bubble formation occurred even after short annealing times and that the size of the helium bubbles was strongly dependent on the tensile stress during heating

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

    International Nuclear Information System (INIS)

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

  12. Optical Forces on Metastable Helium

    Science.gov (United States)

    Corder, Christopher Scott

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

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

    International Nuclear Information System (INIS)

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

  14. 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.

  15. Helium-cooled, solid breeder blanket design for a tokamak fusion reactor

    International Nuclear Information System (INIS)

    A preliminary design for a helium-cooled, solid breeder blanket for a tokamak fusion reactor has been developed and its performance looks quite good. The design is capable of bearing a 4 MW/m2 neutron wall load and the ideal pumping power required for the whole primary helium loop including the steam generators is only 2.5% of the total thermal power. The coolant pressure is at the moderate level of 5 MPa. The integrated helium duct work results in a compact blanket having a maximum overall thickness of only 86 cm. The design work was mainly focused on the thermal-hydraulic aspects, which in fact represent the key problems associated with using helium as a coolant. The present work, however, demonstrates that several disadvantages of helium can be avoided or at least minimized by an appropriate design. Thus, a major part of the criticisms against gas cooling for tokamaks are effectively refuted by this design study. Based on the work presented here, the conceptual design for a helium-cooled, solid breeder blanket test module has been adapted and submitted for the INTOR Testing Program. (Auth.)

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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–Hen, n = 1–3) decreases with increasing temperature, except for He–He2 at T n for helium clusters are also investigated. He2 migrates more quickly than a single He atom does at T 2 changes at higher temperatures. Another counterintuitive observation is that D5 > D3 > D4 at T 5. The Arrhenius relation describes the diffusion of Hen 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

  18. Atom lithography with metastable helium

    Science.gov (United States)

    Allred, Claire S.; Reeves, Jason; Corder, Christopher; Metcalf, Harold

    2010-02-01

    A bright metastable helium (He?) beam is collimated sequentially with the bichromatic force and three optical molasses velocity compression stages. Each He? atom in the beam has 20 eV of internal energy that can destroy a molecular resist assembled on a gold coated silicon wafer. Patterns in the resist are imprinted onto the gold layer with a standard selective etch. Patterning of the wafer with the He? was demonstrated with two methods. First, a mesh was used to protect parts of the wafer making an array of grid lines. Second, a standing wave of ? =1083 nm light was used to channel and focus the He? atoms into lines separated by ? /2. The patterns were measured with an atomic force microscope establishing an edge resolution of 80 nm. Our results are reliable and repeatable.

  19. Helium isotopes in an aurora

    International Nuclear Information System (INIS)

    Aluminum and platinum foils were flown into two bright auroras and subsequently recovered. They were then analyzed for traces of trapped noble gases in a sensitive high-resolution mass spectrometer. The detection of 3He is reported and measurements of the 4He flux reported in a previous paper are confirmed. The 4He:3He ratio in the first (brighter) aurora was 2950+-250. This ratio is only slightly higher than the average solar wind ratio of 2350 and since the atmospheric ratio is grossly different (250 times larger), establishes the solar wind as the principal source of auroral helium, at least in the aurora concerned. The result supports earlier suggestions that auroral precipitation is one of the main sources of the 3He in the terrestrial atmosphere. Current estimates of 3He sources and loss rates are found to be consistent with a balanced atmospheric 3He budget

  20. 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)

  1. 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...

  2. The KfK design of a helium-cooled ceramic blanket for NET

    International Nuclear Information System (INIS)

    A conceptual design of a helium-cooled blanket for the NET double null plasma configuration with a neutron wall load of 1 MW/m2 and 600 MW fusion power is presented. The outboard blanket is made up of self-supporting canisters containing the beryllium multiplier in form of plates. The 6 mm wide slits between the plates contain a bed of 0.5 mm Li4SiO4 pebbles. The helium purge flow at 0.1 MPa carries away the tritium produced in the bed. The first wall of stainless steel and with a graphite tile protection is cooled by toroidally running helium tubes. The inboard blanket is made up of a similar structure, however the helium coolant tubes run in the poloidal direction to allow for more breeding material in the narrow space available. The divertors are composed of TZM elements cooled by helium. The outboard first wall and blanket are cooled by helium at 6 MPa, (inlet temperature=2000C outlet temperature=4500C), while the divertor and the inboard first wall are cooled in series by helium at 11.5 MPa and the inboard blanket by helium at 8 MPa. The calculated temperatures and stresses in blanket, first wall and divertor, appear to be acceptable. Based on the LISA-2 experiments the tritium blanket inventory is about 400 g. The daily tritium production is 96 g and the three-dimensional real tritium breeding ratio is 1.04 for a 6Li enrichment of 90%. (orig.)

  3. Neovascular glaucoma after helium ion irradiation for uveal melanoma

    International Nuclear Information System (INIS)

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

  4. 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.

  5. Quantum solvation of carbonyl sulfide with helium atoms.

    Science.gov (United States)

    Tang, Jian; Xu, Yunjie; McKellar, A R W; Jäger, Wolfgang

    2002-09-20

    High-resolution infrared and microwave spectra of He(N)-carbonyl sulfide (He(N)-OCS) clusters with N ranging from 2 to 8 have been detected and unambiguously assigned. The spectra show the formation of a solvation layer beginning with an equatorial "donut" of five helium atoms around the OCS molecule. The cluster moment of inertia increases as a function of N and overshoots the liquid droplet limit for N > 5, implying that even atoms in the first solvation shell are decoupled from the OCS rotation in helium nanodroplets. To the extent that this is due to superfluidity, the results directly explore the microscopic evolution of a phenomenon that is formally macroscopic in nature. PMID:12242436

  6. Experimental study of ultracold neutron production in pressurized superfluid helium

    CERN Document Server

    Schmidt-Wellenburg, P; Farhi, E; Fertl, M; Leung, K K H; Rahli, A; Soldner, T; Zimmer, O

    2015-01-01

    We have investigated experimentally the pressure dependence of the production of ultracold neutrons (UCN) in superfluid helium in the range from saturated vapor pressure to 20bar. A neutron velocity selector allowed the separation of underlying single-phonon and multiphonon pro- cesses by varying the incident cold neutron (CN) wavelength in the range from 3.5 to 10{\\AA}. The predicted pressure dependence of UCN production derived from inelastic neutron scattering data was confirmed for the single-phonon excitation. For multiphonon based UCN production we found no significant dependence on pressure whereas calculations from inelastic neutron scattering data predict an increase of 43(6)% at 20bar relative to saturated vapor pressure. From our data we conclude that applying pressure to superfluid helium does not increase the overall UCN production rate at a typical CN guide.

  7. 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

  8. Helium effects in iron- and nickel-base developmental alloys

    Science.gov (United States)

    Shiraishi, H.; Hasegawa, A.

    1988-07-01

    The void swelling of Ni-base gamma-prime precipitation strengthened single crystal alloy (TMS-12) and oxide dispersioned MA 754 and MA 956 was investigated using proton irradiation at temperatures ranging from 723 to 873 K. In TMS-12, the voids preferably formed on the precipitates-matrix interface. The swelling increased with increase of the irradiation temperature and the maximum swelling of 3% was obtained at 873 K, which was lower than that in 10% CW 316 and JPCA. The voids were found to nucleate preferably on the oxide-matrix interface in MA 754. The expected reduction of swelling was not obtained in this alloy. Only few voids were found and excellency in swelling characteristic was found in MA 956. The helium embrittlement of MA 956 was studied using the samples pre-injected with a beam of 26 MeV 3He from the NRIM compact cyclotron to concentration of 40 appm He at 873 K. The tensile test was carried out at 873 K varying the strain rate from 10 -3/s to 10 -5/s. Superplastic deformation was observable without helium implantation. The reduction of the total elongation due to helium was observed only at the strain rate of 10 -5/s.

  9. 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

  10. Diffusion and permeation constants of helium in various glasses

    International Nuclear Information System (INIS)

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

  11. 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.

  12. Superfluid helium-4: An introductory review

    International Nuclear Information System (INIS)

    Helium was first liquefied by Kamerlingh Onnes in Leiden in July 1908, an achievement that followed much careful and painstaking work. On the same day Onnes reduced the temperature of his helium to a value approaching lK, and he must therefore have produced and observed the superfluid phase. These experimental discoveries led very quickly to a series of remarkable theoretical contributions that laid the foundations for all subsequent work. The period since the second world war has of course seen an enormous amount of work on superfluid helium-4. In reviewing it the author tries to see it in terms of two threads: one originating from Landau; the other from London

  13. 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.

  14. Elastic and inelastic positron–helium scattering

    International Nuclear Information System (INIS)

    Elastic and inelastic positron–helium scatterings have been investigated with the coupled-channel optical method (CCO). Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential. Calculations are reported of cross sections of elastic scattering, total excitation and n = 2, 3, and 4 excitations of ground-state helium for incident energies from 30 eV to 400 eV. The present calculation shows that the ionization and Ps-formation channels significantly affect the cross sections of elastic and inelastic positron–helium scatterings. (atomic and molecular physics)

  15. 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.

  16. Limits of metastability of liquid helium

    International Nuclear Information System (INIS)

    Helium can remain in a metastable liquid state at a pressure below its saturated vapour pressure or above its melting pressure. This metastability can reach high degrees in helium because of its purity. We review the present knowledge of the stretched liquid state; experiments on cavitation are interpreted in relation to the existence of a liquid-gas spinodal limit. In view of recent experiments, we also consider overpressurized liquid helium 4 and address the question of the stability of the superfluid phase against the solid

  17. 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

  18. 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

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

    Science.gov (United States)

    Kogut, Alan; James, Bryan; Fixsen, Dale

    2013-01-01

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

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

    Science.gov (United States)

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

    2015-07-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  4. Yield spectrum for protons impacting on helium

    International Nuclear Information System (INIS)

    An approximate yield spectrum is developed for proton energy degradation in helium and apply it to determination of the efficiency for the production of various characteristic emissions. 17 references

  5. Primary helium heater for propellant pressurization systems

    Science.gov (United States)

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

    1991-01-01

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

  6. Helium purification system for HTR-10

    International Nuclear Information System (INIS)

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

  7. Helium Find Thaws the Cold Fusion Trail.

    Science.gov (United States)

    Pennisi, E.

    1991-01-01

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

  8. Helium leak testing (problems and trends)

    International Nuclear Information System (INIS)

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

  9. On the helium gas leak test

    International Nuclear Information System (INIS)

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

  10. 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)

  11. 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

  12. Helium-Hydrogen Recovery System Project

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

  13. Helium cosmic ray flux measurements at Mars

    International Nuclear Information System (INIS)

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

  14. 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

  15. Helium refrigeration considerations for ADS cryomodule design

    International Nuclear Information System (INIS)

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

  16. 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

  17. A highly contrasting scanning helium microscope

    Science.gov (United States)

    Fahy, A.; Barr, M.; Martens, J.; Dastoor, P. C.

    2015-02-01

    We present a scanning helium microscope equipped to make use of the unique contrast mechanisms, surface sensitivity, and zero damage imaging the technique affords. The new design delivers an order of magnitude increase in the available helium signal, yielding a higher contrast and signal-to-noise ratio. These improvements allow the microscope to produce high quality, intuitive images of samples using topological contrast, while setting the stage for investigations into further contrast mechanisms.

  18. Static Pressure-Assisted Seal For Helium

    Science.gov (United States)

    Stuck, Donald E.; Okabayashi, Takateru

    1990-01-01

    Two-piece, all-metal, pressure-assisted static flange seal holds in pressurized helium satisfactorily at temperature of negative 80 degree F (negative 62 degree C). Installed between two flanges, then bolted together. New version includes one pressure-assisted metal sealing element held in place by metal plate and flanges. Certified for use in flight on helium joints of Space Shuttle main engine. Likely terrestrial applications include laboratory and industrial gas-distribution systems.

  19. Calculation of the resonant ionization of helium

    International Nuclear Information System (INIS)

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

  20. Helium-propane as drift chamber gas

    International Nuclear Information System (INIS)

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

  1. Helium-propane as drift chamber gas

    International Nuclear Information System (INIS)

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

  2. Helium leak detector of high sensitivity

    International Nuclear Information System (INIS)

    A sensitive mass spectrometer helium leak detector using stigmatic focussing conditions for ion optical geometry has been designed. The minimum detectable leak rate is found to be 2 x 10-11 std cc/sec for helium (8 x 10-12 std cc/sec for air) with a system response of less than 1 second. In this paper we present briefly its design features and performance data. (author). 4 refs., 4 figs

  3. Helium Mixing in Globular Cluster Stars

    OpenAIRE

    Sweigart, A. V.

    1997-01-01

    The observed abundance variations in globular cluster red giants indicate that these stars may be mixing helium from the hydrogen shell outward into the envelope, presumably as a result of internal rotation. We have investigated the implications of such helium mixing for both the red- giant-branch (RGB) and horizontal-branch (HB) phases by computing a number of noncanonical evolutionary sequences for different assumed mixing depths and mass loss rates. We find that the heliu...

  4. 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...

  5. Thin helium film on a glass substrate

    OpenAIRE

    Boninsegni, Massimo

    2009-01-01

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

  6. Primary neutral helium in the heliosphere

    OpenAIRE

    Mueller, Hans-reinhard; Cohen, Jill H.

    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 neutr...

  7. 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/...

  8. COSMIC-RAY PROTON AND HELIUM SPECTRA FROM THE FIRST CREAM FLIGHT

    International Nuclear Information System (INIS)

    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 ± 0.02 for protons from 2.5 TeV to 250 TeV and -2.58 ± 0.02 for helium nuclei from 630 GeV nucleon-1 to 63 TeV nucleon-1. They are harder than previous measurements at a few tens of GeV nucleon-1. 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 ± 0.5 for the range from 2.5 TeV nucleon-1 to 63 TeV nucleon-1. This ratio is considerably smaller than the previous measurements at a few tens of GeV nucleon-1.

  9. Operation of helium-filled proportional counter at low temperatures (4.2-295 K)

    International Nuclear Information System (INIS)

    Following the previous work by our group, the operation of the helium-filled counter has been studied more in detail at liquid-helium (? 5 K), liquid-nitrogen (77 K) and room (295 K) temperatures. The collimated ?-ray beam from a 210Po source, which is installed inside the counter, has made it possible to measure the gas gain M from the ionization-chamber region with M = ? 1. The operation of the helium-filled counter is rather unstable at 77 and 295 K; when the applied voltage is increased, the gas gain steeply rises up to 103 and the pulse rise time becomes longer than 200 ?s. On the other hand, the counter works stably at 5 K, although available gas gains are comparatively small, i.e., at most 170. The slope of gas gain at 5 K is more gentle than that at 77 or 295 K and the pulse rise time does not change (? 2 ?s) so much in the wide range of applied voltage. Measured results for gas gain and pulse rise time are reported in this paper. The favourable operation at 5 K is not only due to the absence of impurity in helium gas but also to the suppression of electron emission from the cathode. This new feature of the proportional-counter operation at a very low temperature is also discussed from the standpoint of atomic processes in helium gas. (orig.)

  10. 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.)

  11. Microstructural evolution in high energy helium implanted nickel and copper

    Science.gov (United States)

    Ehrhart, P.; Gaber, A.; Gadalla, A. A.; Jäger, W.; Tsukuda, N.

    Thin nickel and copper foils (- 12 ?m thick) have been homogeneously implanted with 0-6 MeV ?-particles yielding helium concentrations between 0.1 and 5 at.%. These foils have been investigated by measurements of the length and the lattice parameter and by transmission electron microscopy (TEM). Starting at the lowest implantation dose clustering of irradiation induced vacancies and interstitial atoms leads to the formation of stacking fault tetrahedra (SFT) and dislocation loops that eventually interact to form a dislocation network. In addition a large number of small vacancy-helium complexes is present that are characterized by a rather low average He density, i.e. the concentration of He atoms CH, is about one half of the vacancy concentration cv. At higher implantation doses ( cHe ? 0.6 at.%) cHe/ cV increases slightly up to a value of 1 and small cavities become visible in the TEM. A "model" is proposed that describes this microstructural evolution by the continuous nucleation of stable He-vacancy (He-V) complexes as a result of high energy collision cascades. This model directly explains the low average helium density ( cHe/ cV SFTs. Defect annealing and bubble growth during thermal annealing are discussed.

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2011-01-01

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

  14. 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

  15. Design considerations for very large helium refrigeration system

    International Nuclear Information System (INIS)

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

  16. 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.

  17. 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.

  18. 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...

  19. Advances in helium ion microscopy

    International Nuclear Information System (INIS)

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

  20. Anti-helium from Dark Matter annihilations

    CERN Document Server

    Cirelli, Marco; Taoso, Marco; Vittino, Andrea

    2014-01-01

    Galactic Dark Matter (DM) annihilations can produce cosmic-ray anti-nuclei via the nuclear coalescence of the anti-protons and anti-neutrons originated directly from the annihilation process. Since anti-deuterons have been shown to offer a distinctive DM signal, with potentially good prospects of detection in large portions of the DM-particle parameter space, we explore here the production of heavier anti-nuclei, specifically anti-helium. Even more than for anti-deuterons, the DM-produced anti-He flux can be mostly prominent over the astrophysical anti-He background at low kinetic energies, typically below 3-5 GeV/n. However, the larger number of anti-nucleons involved in the formation process makes the anti-He flux extremely small. We therefore explore, for a few DM benchmark cases, whether the yield is sufficient to allow for anti-He detection in current-generation experiments, such as AMS-02. We account for the uncertainties due to the propagation in the Galaxy and to the uncertain details of the coalescen...

  1. 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

  2. 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

  3. 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).

  4. Helium-filled proportional counter for low-temperature operation (4.2--300 K) and its application to cryogenic resonance-electron Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    The operation of a proportional counter filled with helium gas has been investigated at low temperatures down to 5 K. It has been found for the first time that a helium-filled counter cooled at temperatures below 30 K works well in the proportional region, but with low gas gains (? 100). The operation at low temperatures (? 30 K) is attributed to the complete removal of impurities from helium gas as well as the extreme depression of the reaction frequency of metastable heliums. The absence of impurities results in eliminating the Penning effect, i.e., an ionization process of impurity atoms or molecules by collisions with metastable helium, which spreads electron avalanches in both space and time if helium gas contains a slight amount of impurities (1--103 ppm). Continuous discharges caused by the photoeffect of ultraviolet photons, which are mostly produced in decay channels of metastable helium, are thermally quenched at low temperatures below 30 K. The helium-filled counter provides us with a new method to detect nuclear radiations at very low temperatures. The present counter technique has been successfully applied to the resonance-electron Moessbauer spectroscopy near liquid-helium temperature (--5 K)

  5. Microstructural observation on helium injected and creep ruptured JPCA

    Science.gov (United States)

    Yamamoto, N.; Shiraishi, H.; Kamitsubo, H.; Kohno, I.; Shikata, T.; Hishinuma, A.

    1986-11-01

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

  6. Microstructural observation on helium injected and creep ruptured JPCA

    International Nuclear Information System (INIS)

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

  7. 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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  13. 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.)

  14. 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

  15. Tritium control in helium-cooled blankets

    International Nuclear Information System (INIS)

    As a part of the Blanket Comparison and Selection Study (BCSS), GA Technologies was responsible for the design of helium-cooled, solid- and liquid-metal breeder blankets. Conceptual blanket designs were developed, including the consideration of the generation, transport, and extraction of tritium. Evaluations were made of the inventory and leakage of tritium for helium-cooled Li2O and LiAlO2 and liquid lithium breeder blankets for tokamak and tandem mirror reactors. To facilitate the evaluation, a solid breeder tritium code TRIT4 was developed. The results from this study indicate that tritium inventories and leakages are acceptable for the proposed helium-cooled blankets. An assumption made in the tritium leakage calculations was that tritium is released to the helium purge and coolant streams as T2 and remains in that form. If oxidation to T2O is possible, significant reduction in the tritium leakage will be possible. We conclude that more experimental data on breeder material properties and tritium permeation behavior are needed. However, we are certain that an adequate number of different techniques are available to control the breeder tritium inventory and leakage to an acceptable level in helium-cooled solid- and lithium-breeder blankets

  16. Tritium control in helium-cooled blankets

    Science.gov (United States)

    Wong, C. P. C.; Maya, I.; Kessel, C.; Roelant, D.; Schultz, K. R.

    1985-06-01

    As a part of the Blanket Comparison and Selection study (BCSS), GA Technologies as responsible for the design of helium-cooled, solid- and liquid-metal breeder blankets. Conceptual blanket designs are developed, including the consideration of the generation, transport, and extraction of tritium. Evaluations are made of the inventory and leakage of tritium for helium-cooled Li2O and LiAlO2 and liquid lithium breeder blankets for tokamak and tandem mirror reactors. To facilitate the evaluation, a solid breeder tritium code TRIT4 is developed. The results from this study indicate that tritium inventories and leakages are acceptable for the proposed helium-cooled blankets. An assumption made in the tritium leakage calculations is that tritium is released to the helium purge and coolant streams as T2 and remains in that form. If oxidation to T2O is possible, significant reduction in the tritium leakage will be possible. It is concluded that more experimental data on breeder material properties and tritium permeation behavior are needed. However, an adequate number of techniques is available to control the breeder tritium inventory and leakage to an acceptable level in helium-cooled solid- and lithium-breeder blankets.

  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. 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)

  19. 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)

  20. 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)

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

    International Nuclear Information System (INIS)

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

  2. Experimental and numerical investigation of time evolution of discharge current and optical emission in helium–nitrogen cryoplasmas

    Science.gov (United States)

    Muneoka, Hitoshi; Urabe, Keiichiro; Choi, Jai Hyuk; Stauss, Sven; Terashima, Kazuo

    2014-12-01

    Cryoplasmas represent a class of non-equilibrium plasmas whose gas temperature can be controlled below room temperature. However, so far, the influence of the plasma gas temperature on the plasma chemical reactions has not yet been examined in detail. Here we investigated the time-dependent reaction dynamics related to optical emission in helium–nitrogen cryoplasmas. We acquired voltage and discharge current waveforms, optical emission spectra, and observed a temporal change of the emission intensity in helium–nitrogen cryoplasmas at two experimental conditions (temperatures of temperature detector: 5 K and plasma gas temperature: 28 K (condition A), 40 K and 54 K (condition B)). Two time-dependent phenomena were observed: the first was a longer duration of the discharge current compared to that of helium emission at both conditions A and B, and the second was nitrogen ion emission delayed by about 8 µs with respect to the emissions of atomic helium and helium dimers at 40 K. The experimental observations could be reproduced qualitatively by a global reaction model, which took into account the effect of the plasma gas temperature on the reaction rate constants and the diffusion coefficients. The simulations suggested that the reactions related to metastable helium atom were the key reactions, and that the long lifetimes of metastable helium atoms at cryogenic gas temperatures are crucial for the appearance of the time-dependent phenomena. These results imply that the plasma gas temperature is one of the key parameters in non-equilibrium plasma chemistry.

  3. 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

  4. 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.

  5. 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.

  6. Electron swarm parameters in helium and neon

    International Nuclear Information System (INIS)

    Experimental values have been obtained for both the drift velocity and the ratio of longitudinal diffusion coefficient to mobility for electrons in helium (1.4<=E/N<=226 Td) and neon (1.4<=E/N<=339 Td). Comparison is made with a Monte Carlo computer simulation and a good fit is obtained with the present and previously measured data. The computer simulation results for ionisation coefficient and ratio of radial diffusion coefficient to mobility are compared with both experimental and other theoretical values over a wide range of E/N. A comparison between the mean swarm energy and the breakdown voltage shows that equilibrium conditions exist at the highest E/N (2260 Td for helium and 5600 Td for neon) for which the computations were carried out. A set of cross-sections which accurately simulate electron swarm behaviour in helium and neon are given. (author)

  7. Screw Compressor Characteristics for Helium Refrigeration Systems

    Science.gov (United States)

    Ganni, V.; Knudsen, P.; Creel, J.; Arenius, D.; Casagrande, F.; Howell, M.

    2008-03-01

    The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression. At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well as to implement practical solutions.

  8. 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

  9. Energy spectra of protons and helium nuclei in 1011 - 1013 eV energy range in near-Earth space

    International Nuclear Information System (INIS)

    Using the position-sensitive calorimeter of PAMELA spectrometer energy spectra of protons and helium nuclei of primary cosmic rays in the energy range of 50 GeV-15 TeV and 50 GeV-3.5 TeV/nucleon, correspondingly, are determined, that is necessary for correcting the models of generation and cosmic radiation propagation. The techniques of protons and helium nuclei isolation from general particle flow detecting by installation and their energy determination are developed

  10. 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)

  11. 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

  12. Tritium control in helium-cooled blankets

    International Nuclear Information System (INIS)

    As a part of the Blanket Comparison and Selection Study (BCSS), GA Technologies was responsible for the design of helium-cooled, solidand liquid-metal breeder blankets. Conceptual blanket designs were developed, including the consideration of the generation, transport, and extraction of tritium. Evaluations were made of the inventory and leakage of tritium for helium-cooled Li2O and LiA102 and liquid lithium breeder blankets for tokamak and tandem mirror reactors. To facilitate the evaluation, a solid breeder tritium code TRIT4 was developed

  13. Rotary magnetic refrigerator for superfluid helium production

    International Nuclear Information System (INIS)

    A new rotary-magnetic refrigerator designed to obtain superfluid helium temperatures by executing a magnetic Carnot cycle is developed. A rotor containing 12 magnetic refrigerants (gadolinium-gallium-garnet) is immersed in liquid helium at 4.2 K and rotated at constant speed in a steady magnetic field distribution. Performance tests demonstrate that the new rotary refrigerator is capable of obtaining a temperature of 1.48 K. The maximum useful cooling power obtained at 1.8 K is 1.81 W which corresponds to a refrigeration efficiency of 34%

  14. 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

  15. Ab Initio Simulations of Dense Helium Plasmas

    International Nuclear Information System (INIS)

    We study the thermophysical properties of dense helium plasmas by using quantum molecular dynamics and orbital-free molecular dynamics simulations, where densities are considered from 400 to 800 g/cm3 and temperatures up to 800 eV. Results are presented for the equation of state. From the Kubo-Greenwood formula, we derive the electrical conductivity and electronic thermal conductivity. In particular, with the increase in temperature, we discuss the change in the Lorenz number, which indicates a transition from strong coupling and degenerate state to moderate coupling and partial degeneracy regime for dense helium.

  16. Ab Initio Simulations of Dense Helium Plasmas

    CERN Document Server

    Wang, Cong; Zhang, Ping

    2010-01-01

    We study the thermophysical properties of dense helium plasmas by using quantum molecular dynamics and orbital-free molecular dynamics simulations, where densities are considered from 400 to 800 g/cm$^{3}$ and temperatures up to 800 electron-volt. Results are presented for the equation of state. From the Kubo-Greenwood formula, we derive the electrical conductivity and electronic thermal conductivity. In particular, with the increase of temperature, we discuss the change of Lorenz number, which indicates a transition from strong coupling and degenerate state to moderate coupling and partial degeneracy regime for dense helium.

  17. High precision theory of atomic helium

    Energy Technology Data Exchange (ETDEWEB)

    Drake, G.W.F. [Windsor Univ., ON (Canada). Dept. of Physics

    1999-07-01

    Essentially exact calculations of the nonrelativistic wave functions and energies of helium are reviewed, together with the lowest-order relativistic corrections. The results are extended to the entire singly-excited spectrum of helium by means of asymptotic expansion (core polarization), and quantum defect methods. Comparisons with high-precision experimental atomic transition frequencies then provide a measure of higher-order relativistic and quantum electrodynamic effects. Other applications are discussed, such as the determination of nuclear radii from the isotope shift, and measurement of the fine structure constant from fine structure splittings. Recent progress for the more difficult lithium problem is briefly reviewed. (orig.)

  18. 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.

  19. Helium mobility in advanced nuclear ceramics

    Science.gov (United States)

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

    2014-05-01

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

  20. Level gauge for the liquid helium

    International Nuclear Information System (INIS)

    Level gauge for liquid helium, which can be used as a level indicator and a gauge of limit level is described. An accuracy of the liquid level measurement is equal to +-1 mm. At constant feed, the gauge reaction on its passage from liquid helium into the gaseous one is equal to 0.2 s. Maximum electric imput power of the device produced on the PEhS-10 relay basis, operating under the regime of a low level gauge, does not exceed 0.11 W. Reading of the level gauge do not depend on steam pressure over the liquid surface

  1. 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

  2. Energy harvesting in doped helium nano-droplets

    International Nuclear Information System (INIS)

    We report the observation of sequential Penning ionization of dopants by metastable helium atoms in helium nano-droplets resulting in doubly charged ions. Strong charge induced dipole-interaction between the excited helium atom and the target ion provides a high probability for the transfer of the internal energy of the excited helium atom to the dopant ion. This process may also lead subsequently to a Coulomb explosion of molecular or cluster dopants.

  3. A new helium gas recovery and purification system

    International Nuclear Information System (INIS)

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

  4. Gearbox Scheme in High Temperature Reactor Helium Gas Turbine System

    OpenAIRE

    Sheng Liu; Xuanyu Sheng

    2012-01-01

    Helium Turbine is used in High Temperature Reactor Helium Gas Turbine (HTR-GT) system, by which the direct helium circulation between the reactor and turbine generator system will come true. Between helium turbine and generator, there is gearbox device which reduces the turbine rotation speed to normal speed required by the generator. Three optional gearbox schemes are discussed. The first is single reduction cylindrical gearbox, which consists of one high speed gear and one low speed gear. I...

  5. Calculation of hydrodynamic mass for atomic impurities in helium

    OpenAIRE

    Lehmann, Kevin K.

    2001-01-01

    We present a simple numerical procedure for calculating the irrotational hydrodynamic flow in a helium solvation structure around a spherical solute in linear motion through superfluid helium. The calculation requires only the radial helium density around the impurity as input. From the resulting irrotational flow, the helium contribution to the effective mass of the solute is calculated. The results for alkali cations are compared to recent many-body Variational Monte Carlo...

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

    OpenAIRE

    Pierce, Marlon; Manousakis, Efstratios

    1998-01-01

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

  7. Direct modeling of neutral helium in the heliosphere

    OpenAIRE

    Mueller, Hans-reinhard

    2012-01-01

    Several years of neutral particle measurements by the NASA/IBEX mission have yielded direct observations of interstellar neutral helium and oxygen. The data indicate the presence of secondary neutral helium and oxygen, which are created within the heliosphere by charge exchange involving helium or oxygen ions. This contribution describes a detailed conserving calculation method based on Keplerian orbits that has been developed to characterize helium distribution functions th...

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

    Science.gov (United States)

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

    2000-01-01

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

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

    International Nuclear Information System (INIS)

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

  10. Helium release and microstructural changes in Er(D,T)2-x 3Hex films

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-12-01

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

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

    International Nuclear Information System (INIS)

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

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

    CERN Document Server

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

    2013-01-01

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

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

    International Nuclear Information System (INIS)

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

  15. Positron and deuteron depth profiling in helium-3-implanted electrum-like alloy

    International Nuclear Information System (INIS)

    In spite of previous extensive studies, the helium behavior in metals still remains an issue in microelectronics as well as in nuclear technology. A gold-silver solid solution (Au60Ag40: synthetic gold-rich electrum) was chosen as a relevant model to study helium irradiation of heavy metals. After helium-3 ion implantation at an energy ranging from 4.2 to 5.6 MeV, nuclear reaction analysis (NRA) based on the 3He(d,p)4He reaction, was performed in order to study the thermal diffusion of helium atoms. At room temperature, NRA data reveal that a single Gaussian can fit the He-distribution, which remains unchanged after annealing at temperatures below 0.45 of the melting point. Slow positron implantation spectroscopy, used to monitor the fluence dependence of induced defects unveils a positron saturation trapping, which occurs for He contents of the order of 50-100 appm, whereas concentrations larger than 500 appm seem to favor an increase in the S-parameter of Doppler broadening. Moreover, at high temperature, NRA results clearly show that helium long range diffusion occurs, though, without following a simple Fick law

  16. Recondensation performance of liquid helium cryostat for a 28 GHz electron cyclotron resonance ion source.

    Science.gov (United States)

    Choi, Seyong; Lee, Byoung-Seob; Park, Jin Yong; Ok, Jung-Woo; Shin, Chang Seouk; Yoon, Jang-Hee; Won, Mi-Sook; Kim, Byoung-Chul

    2014-02-01

    Cryostat performance is essential for the stable operation of a superconducting magnet. A closed-cycle liquid helium cryostat was adopted for use for a superconducting electron cyclotron resonance (ECR) ion source by recondensing liquid helium vapor. The goal was to maintain the liquid helium filled reservoir at a constant level without transferring any liquid helium during the normal operation of the ECR ion source. To accomplish this, Gifford-McMahon (GM) refrigerators, which have two cold heads, were installed on the top of the cryostat. The cooling power of the GM cryocooler is 1.5?W at the second stage and 50 W at the first stage. Each stage was connected to the liquid helium reservoir, a radiation shield including high-Tc current lead, and related items. Before commissioning the ECR ion source, a preliminary evaluation of the recondensation performance was carried out with the magnet in partial operation. The design of the cryostat, its fabrication, and the experimental results are reported. PMID:24593494

  17. Nuclear fuel rod helium leak inspection apparatus and method

    International Nuclear Information System (INIS)

    This patent describes an inspection apparatus for testing nuclear fuel rods for helium leaks. It comprises a test chamber being openable and closable for receiving at least one nuclear fuel rod; means separate from the fuel rod for supplying helium and constantly leaking helium at a predetermined known positive value into the test chamber to constantly provide an atmosphere of helium at the predetermined known positive value in the test chamber; and means for sampling the atmosphere within the chamber and measuring the helium in the atmosphere such that a measured helium value below a preset minimum helium value substantially equal to the predetermined known positive value of the atmosphere of helium being constantly provided in the test chamber indicates a malfunction in the inspection apparatus, above a preset maximum helium value greater than the predetermined known positive in the test chamber indicates the existence of a helium leak from the fuel rod, or between the preset minimum and maximum helium values indicates the absence of a helium leak from the fuel rod

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

    International Nuclear Information System (INIS)

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

  19. Direct detection of vacuum ultraviolet scintillations in liquid helium using germanium photodiodes

    Science.gov (United States)

    Luke, Paul N.; Steiner, Herbert M.; Haller, E. E.

    1982-08-01

    Direct detection of vacuum ultraviolet scintillations in liquid helium produced by 5.3 MeV ? particles has been accomplished using a high-purity germanium photodiode. The diode was immersed in the liquid helium and operated in the side-entry mode with a senstive area of 0.3×1.0 cm. Scintillation from each ? particle was detected as a single pulse. A signal rise time <0.1 ?s was obtained at an electric field ?1200 V cm-1. The quantum efficiency of the photodiode was estimated to be ˜4.

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

    International Nuclear Information System (INIS)

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

  1. Helium-excited reactive magnetron sputtering for stress-free silicon nitride films

    Science.gov (United States)

    Sugimoto, Iwao; Nakano, Satoko

    1993-04-01

    Compressive stress in reactively magnetron-sputtered silicon nitride films can be considerably reduced by helium-excited rf plasma. Plasma emission spectroscopy reveals that plasma consisting of the gas ratio of He/N2=11.5 preferentially produces the highly reactive N2+ ions through collisional ionization by the metastably excited helium atoms and suppresses the generation of energetic particles. Increasing plasma reactivity for Si—N bond formation and reduction of the peening effect both effectively reduce the resulting film stress.

  2. Electron yield of glow discharge cathode materials under helium ion bombardment

    Science.gov (United States)

    Szapiro, B.; Rocca, J. J.; Prabhuram, T.

    1988-08-01

    The secondary electron emission coefficient of materials for helium ion bombardment in the energy range 0.5-20 keV was measured for the surface conditions of cathodes in high voltage glow discharges. The materials studied are oxidized aluminum, oxidized magnesium, a molybdenum-aluminum oxide sintered composite, molybdenum, stainless steel, copper, gold, and graphite. Each sample was surface conditioned by operating it as cathode of a helium glow discharge shortly before the electron yield measurement. The results are relevant to the modeling of glow discharges and the design of cold cathode electron guns.

  3. Helium physisorption on internal surfaces of radiation-induced cavities in aluminum: a positron annihilation study

    International Nuclear Information System (INIS)

    Positron lifetime spectra have been measured as a function of temperature in the range 10-295 K for aluminum single crystals irradiated with 0-40 MeV ? particles to a total dose of ? 5x1017 cm-2. We present results for the temperature dependence of the lifetime component representing annihilations of the positrons trapped in helium-filled cavities. We discuss these results in terms of positron diffusion and helium physisorption on the internal surfaces of the irradiation-induced cavities. (orig.)

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

    International Nuclear Information System (INIS)

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

  5. SIMS depth profiling of implanted helium in pure iron using CsHe{sup +} detection mode

    Energy Technology Data Exchange (ETDEWEB)

    Lefaix-Jeuland, H., E-mail: helene.lefaix@cea.fr [CEA, DEN, Service De Recherches De Métallurgie Physique, F-91191 Gif-Sur-Yvette (France); Moll, S.; Legendre, F. [CEA, DEN, Service De Recherches De Métallurgie Physique, F-91191 Gif-Sur-Yvette (France); Jomard, F. [Groupe d’Etude de la Matière Condensée (CNRS and University of Versailles Saint Quentin), 45 avenue des Etats-Unis, 78035 Versailles cedex (France)

    2013-01-15

    Helium distribution in implanted monocrystalline and polycrystalline Fe samples has been measured by secondary ion mass spectrometry (SIMS). The use of Cs{sup +} primary ions in conjunction with the detection of CsHe{sup +} molecular ions was shown to be an efficient method to overcome the very high first ionization potential of helium. The implantation ranges of 60 keV He ions in samples are measured about 220 nm in agreement with projected ranges calculated by TRIM. He concentrations at or above 5 × 10{sup 18} at/cm{sup 3} (?60 ppm) were measured. This study confirms the paramount interest of SIMS as a direct He depth profiling technique.

  6. Direct detection of vacuum ultraviolet scintillations in liquid helium using germanium photodiodes

    International Nuclear Information System (INIS)

    Direct detection of vacuum ultraviolet scintillations in liquid helium produced by 5.3 MeV ? particles has been accomplished using a high-purity germanium photodiode. The diode was immersed in the liquid helium and operated in the side-entry mode with a senstive area of 0.3 x 1.0 cm. Scintillation from each ? particle was detected as a single pulse. A signal rise time or approx. =1200 V cm-1. The quantum efficiency of the photodiode was estimated to be approx.4

  7. Effect of implanted helium on tensile properties and hardness of 9% Cr martensitic stainless steels

    International Nuclear Information System (INIS)

    Hundred micrometer thick specimens of 9% Cr martensitic steels EM10 and T91 were homogeneously implanted with He4 to concentrations up to 0.5 at.% at temperatures from 150 to 550 deg. C. The specimens were tensile tested at room temperature and at the respective implantation temperatures. Subsequently the fracture surfaces were analysed by scanning electron microscopy and some of the specimens were examined in an instrumented hardness tester. The implanted helium caused hardening and embrittlement which both increased with increasing helium content and with decreasing implantation temperature. Fracture surfaces showed intergranular brittle appearance with virtually no necking at the highest implantation doses, when implanted below 250 deg. C. The present tensile results can be scaled to tensile data after irradiation in spallation sources on the basis of helium content but not on displacement damage. An interpretation of this finding by microstructural examination is given in a companion paper [J. Nucl. Mater., these Proceedings

  8. Spectroscopy of antiprotonic helium atoms and its contribution to the fundamental physical constants

    CERN Document Server

    Hayano, R S

    2010-01-01

    Proceedings of the Japan Academy, Series B Vol. 86 (2010) No. 1 P 1-10 Language: Next Article http://dx.doi.org/10.2183/pjab.86.1 JST.JSTAGE/pjab/86.1 Reviews Spectroscopy of antiprotonic helium atoms and its contribution to the fundamental physical constants Ryugo S. HAYANO1) 1) Department of Physics, The University of Tokyo Released 2010/01/14 Keywords: antiproton, CERN, fundamental physical constants, laser spectroscopy Full Text PDF [1604K] Abstracts References(25) Antiprotonic helium atom, a metastable neutral system consisting of an antiproton, an electron and a helium nucleus, was serendipitously discovered, and has been studied at CERN’s antiproton decelerator facility. Its transition frequencies have recently been measured to nine digits of precision by laser spectroscopy. By comparing these experimental results with three-body QED calculations, the antiproton-to-electron massratio was determined as 1836.152674(5). This result contributed to the CODATA recommended val...

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  13. Back pressure helium leak testing of fuel elements for Dhruva research reactor

    International Nuclear Information System (INIS)

    Leak tightness specification on fuel elements for reactor use is always very stringent. The fuel element fabricated for Dhruva reactor is specified to be leak-tight up to 1 x 10-8 std. cc/sec. The fuel element consists of natural metallic uranium rod around 12.5 mm diameter and 3 meter long in encased in aluminium tube and seal welded at both ends. Since helium gas is not filled inside the fuel element while doing seal welding, the only way to do helium leak testing of such fuel rods is by back-pressure technique. This paper describes the development of test facility for carrying out such test and discusses the experiences of carrying out helium leak testing by back-pressure technique on more than 700 numbers of fuel rods for Dhruva reactor. (author). 4 refs., 3 figs., 1 tab

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

    CERN Document Server

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

    1997-01-01

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

  15. Effect of the physical properties of the overburden on helium emanometry. National Uranium Resource Evaluation

    International Nuclear Information System (INIS)

    During the period of 1977 to 1978, a detailed soil helium study (40 samples per square kilometer) was carried out over three known mineralized areas, each being approximately 2.5 square kilometers in extent. These areas were: the Red Desert and Copper Mountain research sites in Wyoming, and the Spokane Mountain research site in Washington State. The result of the detailed study indicated that there was an association between the soil helium anomalies and the known uranium orebodies. This study was carried out in order to determine whether the technique could be used on a semi-reconnaissance basis (10 samples per square kilometer) and to determine if the helium anomalies truly indicate the presence of uranium deposits or reflect the variations in the physical properties of the overburden. The physical properties studied were the porosity and permeability of the rocks. This study was carried out at the Red Desert research site and at the Copper Mountain research site

  16. Microstructure of nimonic PE-16 irradiated to produce high helium contents

    International Nuclear Information System (INIS)

    Initial experiments have begun on the effects of HFIR irradiation of PE-16, where large amounts of helium are produced in the alloy. Irradiation at 400 and 6500C produced cavities coated with the ?' precipitate phase. After irradiation at 4000C and a helium content of 370 at. ppM, the average cavity size was 16.5 nm; at 6500C and a helium content of 1030 at. ppM, a bimodal cavity distribution was created with average sizes of 31.3 and 124.0 nm. Faulted loops were formed at 4000C but not at 6500C. A new observation for irradiated PE-16 was the precipitation of M23C6 in the grain boundaries at 6500C. Experiments under way should help explain many of the microstructural changes in these exploratory PE-16 specimens

  17. Rogue Mantle Helium and Neon

    Science.gov (United States)

    Albarede, F.

    2007-12-01

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

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

    International Nuclear Information System (INIS)

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

  19. Charged hydrogenic, helium, and helium-hydrogenic molecular chains in a strong magnetic field

    Science.gov (United States)

    Turbiner, A. V.; López Vieyra, J. C.; Guevara, N. L.

    2010-04-01

    A nonrelativistic classification of charged molecular hydrogenic, helium, and mixed helium-hydrogenic chains with one or two electrons which can exist in a strong magnetic field B?1016 G is given. It is shown that for both 1e-2e cases at the strongest studied magnetic fields the longest hydrogenic chain contains at most five protons, indicating the existence of H54+ and H53+ ions, respectively. In the case of the helium chains, the longest chains can exist at the strongest studied magnetic fields with three and four ? particles for 1e-2e cases with the possible existence of He35+ and He46+, respectively. For mixed helium-hydrogenic chains, the number of heavy centers can reach five for the highest magnetic fields studied. In general, for a fixed magnetic field, two-electron chains are more bound than one-electron chains.

  20. Infrared absorption of dense helium and its importance in the atmospheres of cool white dwarfs

    Science.gov (United States)

    Kowalski, Piotr M.

    2014-06-01

    Aims: Hydrogen-deficient white dwarfs are characterized by very dense, fluid-like atmospheres of complex physics and chemistry that are still poorly understood. The incomplete description of these atmospheres by the models results in serious problems with the description of spectra of these stars and subsequent difficulties in derivation of their surface parameters. Here, we address the problem of infrared (IR) opacities in the atmospheres of cool white dwarfs by direct ab initio simulations of IR absorption of dense helium. Methods: We applied state-of-the-art density functional theory-based quantum molecular dynamics simulations to obtain the time evolution of the induced dipole moment. The IR absorption coefficients were obtained by the Fourier transform of the dipole moment time autocorrelation function. Results: We found that a dipole moment is induced due to three- and more-body simultaneous collisions between helium atoms in highly compressed helium. This results in a significant IR absorption that is directly proportional to ?He3, where ?He is the density of helium. To our knowledge, this absorption mechanism has never been measured or computed before and is therefore not accounted for in the current atmosphere models. It should dominate the other collisionally induced absorptions (CIA), arising from H-He and H2-He pair collisions, and therefore shape the IR spectra of helium-dominated and pure helium atmosphere cool white dwarfs for He/H > 104. Conclusions: Our work shows that there exists an unaccounted IR absorption mechanism arising from the multi-collisions between He atoms in the helium-rich atmospheres of cool white dwarfs, including pure helium atmospheres. This absorption may be responsible for a yet unexplained frequency dependence of near- and mid-IR spectra of helium-rich stars. The opacity table is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/L8

  1. Deuterium retention and desorption behavior of reduced activated ferritic steel with surface damage due to high energy helium ion irradiation

    International Nuclear Information System (INIS)

    Reduced activation ferritic-martensitic steel F82H was irradiated with 5 keV helium ions to introduce the surface damage. After the irradiation, the irradiated F82H was continuously exposed to 1.7 keV deuterium ions. The effects of the damages introduced by the helium ion irradiation on deuterium retention and desorption behavior of F82H were investigated. The HD desorption had a peak at around 500 K, which was shifted to the high temperature region when the helium ion fluence increased. The decrease in HDO desorption at the high fluence region was observed. This might be owing to the oxygen depletion on the surface by the sputtering. The amount of retained deuterium of the F82H gradually increased with the helium ion fluence and saturated at 7.2 dpa.

  2. Porous plug and superfluid helium film flow suppressor for the soft X-ray spectrometer onboard Astro-H

    Science.gov (United States)

    Ishikawa, Kumi; Ezoe, Yuichiro; Yamaguchi, Hiroya; Mitsuishi, Ikuyuki; Yoshitake, Hiroshi; Mitsuda, Kazuhisa; Fujimoto, Ryuichi; Ohashi, Takaya; Murakami, Masahide; Kanao, Ken-ichi; Yoshida, Seiji; Tsunematsu, Shoji; DiPirro, Michael; Shirron, Peter; SXS Team

    2010-09-01

    Suppression of superfluid helium flow is critical for the Soft X-ray Spectrometer (SXS) onboard Astro-H, to achieve a life time of the liquid helium over 5 years. The superfluid film flow must be sufficiently small, compared to a nominal helium gas flow rate of the SXS (25?g/s). For this purpose, four devices composed of a porous plug, an orifice, a heat exchanger, and knife edge devices will be employed based on the experience of the X-ray microcalorimeter (XRS for X-Ray Spectrometer) onboard Suzaku. The porous plug is a phase separator of the liquid and gas helium. A potential film flow leaking from the porous plug is suppressed by the orifice. Almost all the remaining film flow evaporates at the heat exchanger. The knife edge devices stop the remaining film flow by using atomically sharp edges. In this paper, we describe the principle and design of these four devices.

  3. A semiclassical model of the helium atom

    International Nuclear Information System (INIS)

    A semiclassical model of the helium atom is presented, which has as its basis the concept of classical non-linear resonances. A novel feature of the calculation is its incorporation of exchange effects, leading to singlet-triplet splittings, hitherto inaccessible by a semiclassical approach. Energies of a variety of singly and doubly excited states are given. (author)

  4. Potential applications of high temperature helium

    International Nuclear Information System (INIS)

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

  5. An asteroseismic signature of helium ionization

    CERN Document Server

    Houdek, G

    2006-01-01

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

  6. Thermalization of magnetically trapped metastable helium

    OpenAIRE

    Browaeys, A.; Robert, A3; Sirjean, O.; Poupard, J.; Nowak, S.; Boiron, D.; Westbrook, C.I.; Aspect, A.

    2001-01-01

    We have observed thermalization by elastic collisions of magnetically trapped metastable helium atoms. Our method directly samples the reconstruction of a thermal energy distribution after the application of an RF knife. The relaxation time of our sample towards equilibrium gives an elastic collision rate constant close to the unitarity limit.

  7. Messer to provide helium for LHC

    CERN Multimedia

    2008-01-01

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

  8. Liquid helium servicing from the space station

    Science.gov (United States)

    Breon, S. R.

    The current concept of liquid helium resupply from the space station is discussed with regard to user and space station requirements, as well as requirements of the liquid helium servicing facility itself. A number of trade-offs which will affect both the hardware and the operation of the facility are presented. A total of 12 potential users have been identified. The users are divided into two groups: large volume users which are serviced every one to two years and small volume users which are serviced every few months. Both groups have a very strong impact on the definition of the liquid helium servicing facility. The facility components will be based on results of the Superfluid Helium On Orbit Transfer flight demonstration being conducted by NASA. Currently, the space station design includes a customer servicing bay which provides electrical power, thermal and contamination control, and connections for control and data handling systems. Restrictions on venting and vibrational disturbances on the space station may preclude servicing during quiescent periods when accelerations are minimal.

  9. Fuzzy pressure controller for helium bath cryostats.

    Czech Academy of Sciences Publication Activity Database

    Hanzelka, Pavel; Jura, P.

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

  10. Messer to provide helium for LHC project

    CERN Multimedia

    2008-01-01

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

  11. Helium and Sulfur Hexafluoride in Musical Instruments

    Science.gov (United States)

    Forinash, Kyle; Dixon, Cory L.

    2014-01-01

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

  12. Phase Transitions in liquid Helium 3

    OpenAIRE

    Kindermann, Markus; Wetterich, Christof

    2000-01-01

    The phase transitions of liquid Helium 3 are described by truncations of an exact nonperturbative renormalization group equation. The location of the first order transition lines and the jump in the order parameter are computed quantitatively. At the triple point we find indications for partially universal behaviour. We suggest experiments that could help to determine the effective interactions between fermion pairs.

  13. A Helium nanodrop bouncing off a wall

    OpenAIRE

    Ka Lbermann, G.

    2003-01-01

    We investigate numerically the quantum collision between a stable Helium nanodrop and an infinitely hard wall in one dimension. The scattering outcome is compared to the same event omitting the quantum pressure. Only the quantum process reflects the effect of diffraction of wave packets in space and time.

  14. Forbidden transitions in the helium atom

    OpenAIRE

    Lach, Grzegorz; Pachucki, Krzysztof

    2001-01-01

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

  15. Low-energy Antiproton Interaction with Helium

    OpenAIRE

    Gibbs, W. R.

    1997-01-01

    An ab initio potential for the interaction of the neutral helium atom with antiprotons and protons is calculated using the Born-Oppenheimer approximation. Using this potential, the annihilation cross section for antiprotons in the energy range 0.01 microvolt to 1 eV is calculated.

  16. Thermal expansion of single-crystal fullerite C60 at liquid-helium temperatures

    International Nuclear Information System (INIS)

    The thermal expansion of single crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2-10 K). At temperatures below approx 4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with previous results on polycrystalline materials. A qualitative explanation of the results is proposed

  17. The liquid helium thermosyphon for the GEM Detector Magnet

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2015-06-01

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

  20. Doubly excited helium. From strong correlation to chaos

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Pentlehner, D.; Slenczka, A.

    2015-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1998-03-01

    A method was recently proposed by Garner and Greenwood that would allow the separation of the effects of solid and gaseous transmutation for Cu-Zn-Ni alloys. Pure copper produces zinc and nickel during neutron irradiation. {sup 63}Cu transmutes to {sup 64}Ni and {sup 64}Zn, in about a 2-to-1 ratio, and {sup 65}Cu transmutes to {sup 66}Zn. The {sup 64}Zn further transmutes to {sup 65}Zn which has been shown to have a high thermal neutron (n,{alpha}) cross-section. Since a three-step reaction sequence is required for natural copper, the amount of helium produced is much smaller than would be produced for the two-step, well-known {sup 58}Ni (n,{gamma}) {sup 59}Ni (n,{alpha}) reaction sequence. The addition of natural Zn and Ni to copper leads to greatly increased helium production in neutron spectra with a significant thermal component. Using a suitable Cu-Zn-Ni alloy matrix and comparative irradiation of thermal neutron-shielded and unshielded specimens, it should be possible to distinguish the separate influences of the solid and gaseous transmutants. Whereas helium generation rates have been previously measured for natural nickel and copper, they have not been measured for natural Zn or Cu-Ni-Zn alloys. The (N,{alpha}) cross section for {sup 65}Zn was inferred from helium measurements made with natural copper. By comparing helium production in Cu and Cu-Zn alloys, this cross section can be determined more accurately. In the current study, both the solid and helium transmutants were measured for Cu, Cu-5Ni, Cu-3.5Zn and Cu-5Ni-2Zn, irradiated in each of two positions in the HFIR JP-23 test. Highly accurate helium measurements were performed on these materials by isotope dilution mass spectrometry using a facility that was recently moved from Rockwell International to PNNL. It is shown that both the helium and solid transmutants for Cu-zn-Ni alloys can be calculated with reasonable certainty, allowing the development of a transmutation experiment as proposed by Garner and Greenwood.

  3. Thermal compression of atomic hydrogen on helium surface

    CERN Document Server

    J"arvinen, J; Vasilev, S

    2006-01-01

    We describe experiments with spin-polarized atomic hydrogen gas adsorbed on liquid $^{4}$He surface. The surface gas density is increased locally by thermal compression up to $5.5\\times10^{12}$ cm$^{-2}$ at 110 mK. This corresponds to the onset of quantum degeneracy with the thermal de-Broglie wavelength being 1.5 times larger than the mean interatomic spacing. The atoms were detected directly with a 129 GHz electron-spin resonance spectrometer probing both the surface and the bulk gas. This, and the simultaneous measurement of the recombination power, allowed us to make accurate studies of the adsorption isotherm and the heat removal from the adsorbed hydrogen gas. From the data, we estimate the thermal contact between 2D hydrogen gas and phonons of the helium film. We analyze the limitations of the thermal compression method and the possibility to reach the superfluid transition in 2D hydrogen gas.

  4. The future of helium as a natural resource

    CERN Document Server

    Glowacki, Bartek A; Nuttall, William J

    2012-01-01

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

  5. Method to control the amount of helium during leak testing

    International Nuclear Information System (INIS)

    The purpose of this paper is to demonstrate a method for limiting the amount of helium administered during leak testing and provide a method for keeping the atmospheric helium in a location to a minimum to eliminate backstreaming into the system. This method utilizes the permeability of a balloon. The transporting of helium to the leak check area is also safer by not requiring a cylinder in the leak check location. Utilizing the many shapes of balloons and partially filling of the balloon, any configuration can deliver helium to the leak location. The balloon I filled for the test fell to the floor with the amount of helium I put into the balloon

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

    CERN Document Server

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

    2011-01-01

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

  7. Growth process of helium bubbles in aluminium

    International Nuclear Information System (INIS)

    The growth process of helium bubbles in ?-particle bombarded pure aluminum during isothermal anneal ranging 200 to 6450C and 1 to 100 hr was observed by a transmission electron microscope and the possible growth mechanisms are discussed. The effects of helium concentration and cold work were investigated. The helium bubbles are detectable only at the anneal above 5500C in both annealed and cold worked samples. The cold work does not cause any extra coarsening trend of bubbles. The observed types of bubble distribution in the grain interior are divided into two categories, irrespective of helium concentration and cold work; (1) the fine and uniform bubble distribution, in which case the average size is limited to about 200 A or less in diameter even at the anneal just below the melting point, and (2) the coarsened and non-uniform bubble distribution ranging 500 to 4000 A in diameter. The intermediate size bubbles are scarcely found in any cases. In the above fine bubble distribution, the increase of helium concentration by a factor of two increases the density by the same factor of two, but does not change the mean size of bubbles. Corresponding to the above two characteristic bubble distributions, it is concluded that two different mechanisms are operative in this experiment; (1) the growth of bubbles by the Brownian motion, in which the growth rate of bubbles is decreased to almost zero by bubble faceting and this results in the bubble size cong and this results in the bubble size constancy during the prolonged annealing, and (2) the growth of bubbles by the grain boundary sweep-out mechanism, by which the abrupt coarsening of bubbles is caused. The lack of existence of the intermediate size bubbles is explained in this way. (auth.)

  8. Growth process of helium bubbles in aluminum

    International Nuclear Information System (INIS)

    The growth process of helium bubbles in ?-particle bombarded pure aluminum during isothermal anneal at 200 to 6450C for 1 hr to 100 hr was observed by transmission electronmicroscopy and possible mechanisms are discussed. The effects of helium concentration and cold work were investigated. Helium bubbles are detectable only by annealing above 5500C for 1 hr in both the annealed and cold worked samples. The cold work does not cause any extra coarsening trend of bubbles. The observed types of the bubble distribution are divided into two categories, irrespective of helium concentration and cold work; (1) fine and uniform bubble distribution, in which case the average size is limited to about 200 A or less in diameter even by the anneal just below the melting point, and (2) the coarsened and nonuniform bubble distribution ranging from 500 to 4000 A in diameter. The intermediate size bubbles are scarcely found in any cases. In the above fine bubble distribution, the increase of helium concentration by a factor of two increases the density by the same factor of two, but does not change the mean size of bubbles. From these two characteristic bubble distributions, it is concluded that two different mechanisms are operative in this experiment (1) the growth of bubbles by Brownian motion, in which the growth rate of bubbles is decreased to almost zero by bubble faceting and this results in the bubble size constancy during the prolonged annealing, and (2) during the prolonged annealing, and (2) the growth of bubbles by the grain boundary sweep-out mechanism, by which the abrupt coarsening of bubbles is caused. The lack of the intermediate size bubble is explained in this way. (auth.)

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

    International Nuclear Information System (INIS)

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

  10. Molecular dynamics study of helium bubble pressure in titanium

    International Nuclear Information System (INIS)

    In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals. (condensed matter: structural, mechanical, and thermal properties)

  11. The installation of helium auxiliary systems in HTGR

    International Nuclear Information System (INIS)

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

  12. Flow characteristics and redesign of highly loaded helium compressors

    International Nuclear Information System (INIS)

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

  13. The study of helium release, damage accumulation and surface morphology in annealing process of helium-implanted spinel

    International Nuclear Information System (INIS)

    Magnesium aluminate spinel(MgAl2O4), due to its excellent radiation resistance, good electrical insulation, high melting point and thermal conductance, has the potential for use as electrical insulator in future fusion reactor. In addition, it is also one of the candidate materials for use as a uranium free inert matrix for the transmutation of minor actinides. Helium accumulation in materials due to a decay and (n, ?) nuclear reaction has a severe influence to the mechanism properties. It is therefore of importance to study the helium behavior and damage accumulation in spinel for the application of spinel in nuclear energy field. MgAl2O4(110) single-crystal specimens were implanted with 100 keV 4He+ ions at room temperature to fluences of 0.5, 2 and 8 x 1016 cm-2. The as-implanted samples were annealed at temperature of 500, 700, 900, 1000 and 1100 degree C respectively for 1 hour in vacuum. Different techniques, including Fourier transformed infrared (FTIR) spectroscopy, thermal desorption spectroscopy (TDS), Rutherford back scattering in channeling geometry (RBS-c) and atomic force microscopy (AFM) were adopted subsequently to analyze the samples. It was found that the infra-red absorbance peak corresponding to the Al-O bond vibration shifted to different directions in the as-implantation and annealing processes. At the same time the damage accumulation in spinel showed differmage accumulation in spinel showed different behavior depending on implantation dose in the annealing process. The shift of the infra-red absorbance peak and the different damage accumulation behavior are considered to be related with the He agglomeration resulting in the formation of He clusters or He bubbles in spinel. The surface morphology analysis confirmed the formation of helium bubbles below the implanted surface at the higher doses after some annealing process. (authors)

  14. Helium nano-bubble evolution in aging metal tritides

    International Nuclear Information System (INIS)

    A continuum-scale, evolutionary model of helium (He) nano-bubble nucleation, growth and He release for aging bulk metal tritides is presented which accounts for major features of the experimental database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, is found to occur during the first few days following tritium introduction into the metal and is sensitive to the He diffusivity and pairing energy. An effective helium diffusivity of 0.3 x 10-16 cm2/s at 300 K is required to generate the average bubble density of 5x 1017 bubbles/cm3 observed by transmission electron microscopy (TEM). Early bubble growth by dislocation loop punching with a l/radius bubble pressure dependence produces good agreement with He atomic volumes and bubble pressures determined from swelling data, nuclear magnetic resonance (NMR) measurements, and hydride pressure-composition-temperature (PCT) shifts. The model predicts that later in life neighboring bubble interactions may first lower the loop punching pressure through cooperative stress effects, then raise the pressure by partial blocking of loops. It also accounts for the shape of the bubble spacing distribution obtained from NMR data. This distribution is found to remain fixed with age, justifying the separation of nucleation and growth phases, providing a sensitive test of the growth formulation, and indicating that further significant bubble nucleation does not occur throughout life.nucleation does not occur throughout life. Helium generated within the escape depth of surfaces and surface-connected porosity produces the low-level early helium release. Accelerated or rapid release is modeled as inter-bubble fracture using an average ligament stress criterion. Good agreement is found between the predicted onset of fracture and the observed He-metal ratio (HeM) for rapid He release from bulk palladium tritide. An examination of how inter-bubble fracture varies over the bubble spacing distribution shows that the critical Hem will be lower for thin films or small particle material. It is concluded that control of He retention can be accomplished through control of bubble nucleation

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

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2004-05-01

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

  16. Near-infrared spectroscopy of ethylene and ethylene dimer in superfluid helium droplets.

    Science.gov (United States)

    Scheele, Iris; Conjusteau, André; Callegari, Carlo; Schmied, Roman; Lehmann, Kevin K; Scoles, Giacinto

    2005-03-01

    The nu(5)+nu(9) spectra of ethylene, C(2)H(4), and its dimer, solvated in helium nanodroplets, have been recorded in the wavelength region near 1.6 microm. The monomer transitions show homogeneous broadening of approximately 0.5 cm(-1), which is interpreted as due to an upper state vibrational relaxation lifetime of approximately 10 ps. Nearly resonant vibrational energy transfer (nu(5)+nu(9)-->2nu(5)) is proposed as the relaxation pathway. The dimer gives a single unresolved absorption feature located 4 cm(-1) to the red of the monomer band origin. The scaling of moments of inertia upon solvation in helium is 1.18 for the monomer and >2.5 for the dimer. In terms of the adiabatic following approximation, this classifies the monomer as a fast rotor and the dimer as a slow rotor. PMID:15836315

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

    International Nuclear Information System (INIS)

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

  18. WARM BREEZE FROM THE STARBOARD BOW: A NEW POPULATION OF NEUTRAL HELIUM IN THE HELIOSPHERE

    International Nuclear Information System (INIS)

    We investigate the signals from neutral helium atoms observed in situ from Earth orbit in 2010 by the Interstellar Boundary Explorer (IBEX). The full helium signal observed during the 2010 observation season can be explained as a superposition of pristine neutral interstellar He gas and an additional population of neutral helium that we call the Warm Breeze. The Warm Breeze is approximately 2 times slower and 2.5 times warmer than the primary interstellar He population, and its density in front of the heliosphere is ?7% that of the neutral interstellar helium. The inflow direction of the Warm Breeze differs by ?19° from the inflow direction of interstellar gas. The Warm Breeze seems to be a long-term, perhaps permanent feature of the heliospheric environment. It has not been detected earlier because it is strongly ionized inside the heliosphere. This effect brings it below the threshold of detection via pickup ion and heliospheric backscatter glow observations, as well as by the direct sampling of GAS/Ulysses. We discuss possible sources for the Warm Breeze, including (1) the secondary population of interstellar helium, created via charge exchange and perhaps elastic scattering of neutral interstellar He atoms on interstellar He+ ions in the outer heliosheath, or (2) a gust of interstellar He originating from a hypothetic wave train in the Local Interstellar Cloud. A secondary population is expected from models, but the characteristics of o not fully conform to modeling results. If, nevertheless, this is the explanation, IBEX-Lo observations of the Warm Breeze provide key insights into the physical state of plasma in the outer heliosheath. If the second hypothesis is true, the source is likely to be located within a few thousand AU from the Sun, which is the propagation range of possible gusts of interstellar neutral helium with the Warm Breeze characteristics against dissipation via elastic scattering in the Local Cloud. Whatever the nature of the Warm Breeze, its discovery exposes a critical new feature of our heliospheric environment

  19. Helium- and sodium-bonded mixed-nitride fuel performance

    International Nuclear Information System (INIS)

    Recent PIE data for sodium-bonded mixed-nitride fuel provide promising support for the shrouded-fuel design concept for preventing fuel-clad mechanical interaction until the fuel cladding gap is consumed. Mechanical interaction apparently is precluded since the Type 316 stainless steel appears to begin swelling at a rate greater than the fuel before the gap is consumed. These data also indicate very low fission-gap release rates for the mixed-nitride fuel and a lack of chemical reaction with the stainless steel cladding. Irradiation tests of helium-bonded fuel elements have resulted in a number of test element failures. The only design feature common to all elements was a small (nominal 0.127 mm) gap; two of the elements were loaded with high-density fuel pellets and one with low-density pellets. Diametral expansions were found to be related to smear density with gap size influencing the results. A linear dependence of diametral expansions on burnup is indicated. Helium-bonded elements fabricated with a small gap (0.127 mm) and containing fuel with pellet densities in excess of 88% of theoretical exhibit severe ridging. The ridge peaks coincide with pellet-pellet interfaces. Element failure is not related to ridging. 5 figures

  20. A <= 6 helium clusters using soft core potentials

    CERN Document Server

    Gattobigio, M; Viviani, M

    2011-01-01

    In this work we investigate small clusters of helium atoms using the hyperspherical harmonic basis. We consider systems with $A=2,3,4,5,6$ atoms with an inter-particle potential which does not present a strong repulsion at short distances. We use an attractive gaussian potential that reproduces the values of the dimer binding energy, the atom-atom scattering length, and the effective range obtained with one of the widely used He-He interactions, the LM2M2 potential. In systems with more than two atoms we consider a repulsive three-body force that, by construction, reproduces the trimer binding energy of the LM2M2 potential. With this model, consisting in the sum of a two- and three-body potential, we have calculated the spectrum of clusters formed by four, five and six helium atoms. We have found that these systems present two bound states, one deep and one shallow close to the threshold fixed by the energy of the $(A-1)$-atom system. Universal relations between the energies of the excited state of the $A$-at...