WorldWideScience

Sample records for hot helium mesure

  1. Hot-wire anemometry in hypersonic helium flow

    Science.gov (United States)

    Wagner, R. D.; Weinstein, L. M.

    1974-01-01

    Hot-wire anemometry techniques are described that have been developed and used for hypersonic-helium-flow studies. The short run time available dictated certain innovations in applying conventional hot-wire techniques. Some examples are given to show the application of the techniques used. Modifications to conventional equipment are described, including probe modifications and probe heating controls.

  2. Hot-wire anemometry for turbulence measurements in helium-air mixtures

    Science.gov (United States)

    Libby, P. A.; Larue, J. C.

    1979-01-01

    The use of extended hot-wire anemometry involving an interfering probe is shown to permit measurements of variable density turbulence such as arises in the mixing of helium and air. The methods of calibration and data reduction leading to time series in one or more velocity components, in the mass fraction of helium, and in the mixture density are described. Typical results in various flows to which the technique has been applied are discussed.

  3. Spectra of Cold Molecular Ions from Hot Helium Nanodroplets

    Science.gov (United States)

    Drabbels, Marcel

    2012-06-01

    The function of a molecule is intimately related to its structure. Accordingly, in the quest for a better understanding of molecular function, the development of spectroscopic methods to elucidate molecular structures increasingly takes central stage. The amount of detail that can be derived from spectra depends on the experimental conditions, most notably on the temperature of the sample and the intermolecular interactions a molecule experiences. Helium nanodroplets provide in this respect an almost ideal matrix [1, 2]. For neutral molecules, helium nanodroplet spectroscopy thus has led to important discoveries related to the structure of key molecular systems and has provided insight into the mechanisms underlying chemical reactions. Compared to the level of sophistication that has been reached for neutrals, the spectroscopic exploration of ions is still in its infancy. The use of helium droplets as a cryogenic matrix could potentially solve many of the technical challenges associated with recording high-resolution spectra of cold molecular ions. Here, we will present a method to record spectra of ion containing helium nanodroplets that finds its roots in the nonthermal cooling dynamics of excited molecular ions. In addition, spectra of several molecular ions will be present and the influence of the helium environment on these spectra will be discussed. [1] G. Scoles, and K. K. Lehmann, Science 287, 2429 (2000). [2] J. P. Toennies, and A. F. Vilesov, Angew. Chem. Int. Ed. 43, 2622 (2004).

  4. Hydrogen in hot subdwarfs formed by double helium white dwarf mergers

    CERN Document Server

    Hall, Philip D

    2016-01-01

    Isolated hot subdwarfs might be formed by the merging of two helium-core white dwarfs. Before merging, helium-core white dwarfs have hydrogen-rich envelopes and some of this hydrogen may survive the merger. We calculate the mass of hydrogen that is present at the start of such mergers and, with the assumption that hydrogen is mixed throughout the disrupted white dwarf in the merger process, estimate how much can survive. We find a hydrogen mass of up to about $2 \\times 10^{-3}\\,\\mathrm{M}_{\\odot}$ in merger remnants. We make model merger remnants that include the hydrogen mass appropriate to their total mass and compare their atmospheric parameters with a sample of apparently isolated hot subdwarfs, hydrogen-rich sdBs. The majority of these stars can be explained as the remnants of double helium white dwarf mergers.

  5. Far-UV Spectroscopy of Two Extremely Hot, Helium-Rich White Dwarfs

    Science.gov (United States)

    Werner, K.; Rauch, T.; Kruk, J. W.

    2017-01-01

    A large proportion of hot post-asymptotic giant branch stars and white dwarfs (WDs) are hydrogen-deficient. Two distinct evolutionary sequences have been identified. One of them comprises stars of spectral type [WC] and PG1159, and it originates from a late helium-shell flash, creating helium-rich stellar atmospheres with significant admixtures of carbon (up to about 50, mass fraction). The other sequence comprises stars of spectral type O(He) and luminous subdwarf O stars which possibly are descendants of RCrB stars and extreme helium stars. Their carbon abundances are significantly lower (of the order of 1 or less) and it is thought that they originate from binary-star evolution (through merger or common-envelope evolution). Here we investigate two of the three hottest known helium-rich (DO) WDs (PG 1034+001 and PG 0038+199). They are the only ones for which spectra were recorded with the Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope, allowing a comprehensive ultraviolet spectral analysis. We find effective temperatures of T(eff) =115000 +/- 5000 K and 125000 +/- 5000 K, respectively, and a surface gravity of log g = 7 +/-0.5. In both stars, nitrogen is strongly oversolar while C and O are significantly subsolar. For all other assessed metals (Ne, Si, P, S, Ar, Fe, and Ni) we find abundances close to solar. We conclude that these WDs are immediate descendants of O(He) stars and, hence, result from close-binary evolution.

  6. Measurements of mass flux and concentration in supersonic air/helium mixing by hot-wire anemometry

    OpenAIRE

    KONDO, Akira; Sakaue, Shoji; Arai, Takakage; 近藤 暁; 坂上 昇史; 新井 隆景

    2008-01-01

    In the present study we made efforts to realize a measurement method of mass flux and concentration in supersonic air/helium flow in order to clarify the mixing process. The measuring equipment, which was used for measuring the fluctuations of mass flux and concentration, is consisted of a double-hot-wire probe and CVA (Constant Voltage Anemometer) circuit with 500 kHz bandwidth. The distance between two wires of double-hot-wire probe was 0.16 mm. By using the same material as the hot wire, t...

  7. Path integral Monte Carlo and density functional molecular dynamics simulations of hot, dense helium

    Science.gov (United States)

    Militzer, B.

    2009-04-01

    Two first-principles simulation techniques, path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD), are applied to study hot, dense helium in the density-temperature range of 0.387-5.35gcm-3 and 500K-1.28×108K . One coherent equation of state is derived by combining DFT-MD data at lower temperatures with PIMC results at higher temperatures. Good agreement between both techniques is found in an intermediate-temperature range. For the highest temperatures, the PIMC results converge to the Debye-Hückel limiting law. In order to derive the entropy, a thermodynamically consistent free-energy fit is used that reproduces the internal energies and pressure derived from the first-principles simulations. The equation of state is presented in the form of a table as well as a fit and is compared with different free-energy models. Pair-correlation functions and the electronic density of states are discussed. Shock Hugoniot curves are compared with recent laser shock-wave experiments.

  8. Spectral line shapes using the dicenter approach for dense hot plasmas: hydrogen and helium-like lines.

    Science.gov (United States)

    Sauvan, P.; Leboucher-Dalimier, E.; Angelo, P.; Derfoul, H.; Ceccotti, T.; Poquerusse, A.; Calisti, A.; Talin, B.

    2000-05-01

    This paper reports on the spectral line shape of hydrogen and helium-like lines relevant to the quasi-static dicenter model. This treatment is justified for hot dense, moderate Z plasmas. The code IDEFIX developed for the quasi-static dicenter model involves a self-consistent description of the interactions and of the radiative properties. Strong dependence of the transition energies and of the dipole moments on the interionic separation are pointed out and novel density-dependent spectroscopic features such as asymmetries, satellite-like features, molecular transitions are exhibited. The theoretical spectra presented are discussed in connection with experimental results where these exist.

  9. Abundances of neutron-capture elements in the Hot Extreme-Helium Stars V1920 Cygni and HD 124448

    CERN Document Server

    Pandey, G; Rao, N K; Jeffery, C S; Pandey, Gajendra; Lambert, David L.

    2004-01-01

    Analysis of HST STIS ultraviolet spectra of two hot extreme helium stars (EHes): V1920 Cyg and HD 124448 provide the first measurements of abundances of neutron-capture elements for EHes. Although the two stars have similar abundances for elements up through the iron-group, they differ strikingly in their abundances of heavier elements: V1920 Cyg is enriched by a factor of 30 in light neutron-capture elements (Y/Fe, Zr/Fe) relative to HD 124448. These differences in abundances of neutron-capture elements among EHes mirrors that exhibited by the RCrB stars, and is evidence supporting the view that there is an evolutionary connection between these two groups of hydrogen-deficient stars. Also, the abundances of Y and Zr in V1920 Cyg provide evidence that at least one EHe star went through a s-process synthesis episode in its earlier evolution.

  10. La mesure du danger

    CERN Document Server

    Manceron, Vanessa; Revet, Sandrine

    2014-01-01

    La mesure du danger permet d’explorer des dangers de nature aussi diverse que la délinquance, la pollution, l’écueil maritime, la maladie ou l’attaque sorcellaire, l’extinction d’espèces animales ou végétales, voire de la Planète tout entière. Au croisement de la sociologie, de l’anthropologie et de l’histoire, les différents articles analysent les pratiques concrètes de mesure pour tenter de comprendre ce qui se produit au cours de l’opération d’évaluation du danger sans préjuger de la nature de celui-ci. L’anthropologie a contribué à la réflexion sur l’infortune en s’intéressant aux temporalités de l’après : maladies, catastrophes, pandémies, etc. et en cherchant à rendre compte de l’expérience des victimes, de leur vie ordinaire bouleversée, de la recomposition du quotidien. Elle s’intéresse aussi aux autres types de mesures, les savoirs incorporés, qui reposent sur l’odorat, la vue ou le toucher et ceux qui ressortent d’une épistémologie « non ...

  11. Measurement of the local void fraction in two-phase air-water flow with a hot-film anemometer; Mesure du taux de vide local en ecoulement diphasique eau-air par un anemometre a film chaud

    Energy Technology Data Exchange (ETDEWEB)

    Delhaye, J. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1968-07-01

    The experimental knowledge of the local void-fraction is basic for the derivation of the constitutive equations of two-phase flows. This report deals with measurements of the local void-fraction based on the use of a constant temperature hot-film anemometer associated with a multichannel analyser. After determining the void-fraction profile along a diameter of a vertical pipe (40 mm I.D.), in which air and water flow upwards, we compare the void-fraction averaged over the diameter with the average value measured directly by a {gamma}-ray method. Two runs were made in bubble flow and a third in slug flow. The two methods give results in a good agreement especially for bubble flow. The void-fraction averaged over the cross-section was also calculated from the different profiles and compared in a good manner with the experimental results of R. ROUMY. For bubble flow we verified the theory of S.G. BANKOFF about the shape of the void-fraction profiles. (author) [French] Nous proposons une methode de mesure du taux de vide local a en ecoulement diphasique, basee sur l'emploi d'un anemometre a film chaud a temperature constante dont on etudie la repartition du signal en amplitude dans un analyseur multicanaux. Ayant trace un profil de taux de vide local suivant un diametre d'une conduite verticale de section circulaire parcourue par un ecoulement ascendant d'eau et d'air, nous avons compare la moyenne de {alpha} sur ce diametre a la valeur obtenue par une methode d'absorption de rayons {gamma}. Les essais ont ete faits en ecoulements a bulles et a bouchons. Les deux methodes donnent des resultats concordants en particulier pour les ecoulements a bulles. Le taux de vide moyenne dans la section, calcule a partir des differents profils, a egalement ete compare avec succes aux resultats experimentaux de R. ROUMY. Dans l'etude de la structure radiale des ecoulements a bulles, nous avons verifie l'hypothese de S.G. BAJMKOFF. (auteur)

  12. Instruments de mesure en acoustique

    DEFF Research Database (Denmark)

    Tarnov, Viggo; Jacobsen, Finn

    2008-01-01

    La mesure en acoustique fait appel à des instruments qui mesurent, d'une part la pression, d'autre part l'intensité du signal. Ce dossier présentera, notamment, deux appareils spécialisés : les sonomètres et les microphones. Il abordera l'ensemble des informations majeures à connaître sur les...

  13. MESURE DE LA PERFORMANCE GLOBALE DES ENTREPRISES

    OpenAIRE

    Renaud, Angèle; Berland, Nicolas

    2007-01-01

    International audience; L'engagement des entreprises dans le développement durable consiste à conjuguer performance et responsabilité. La performance financière ne suffit plus à apprécier la performance d'une entreprise. Dès lors, les entreprises doivent mesurer leurs progrès à partir d'une performance plus globale incluant, en dehors de la dimension économique, des dimensions sociale et environnementale. A présent, comment mesurer cette performance globale ? Existe-il des outils de mesure gl...

  14. Liquid helium

    CERN Document Server

    Atkins, K R

    1959-01-01

    Originally published in 1959 as part of the Cambridge Monographs on Physics series, this book addresses liquid helium from the dual perspectives of statistical mechanics and hydrodynamics. Atkins looks at both Helium Three and Helium Four, as well as the properties of a combination of the two isotopes. This book will be of value to anyone with an interest in the history of science and the study of one of the universe's most fundamental elements.

  15. Hot subdwarf stars in close-up view IV. Helium abundances and the $^3$He isotopic anomaly of subdwarf B star

    CERN Document Server

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

    2013-01-01

    Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample consists of newly discovered stars from the Edinburgh Cape survey. We showed that effective temperatures and surface gravities can be derived from high resolution echelle spectra with sufficient accuracy. Systematic uncertainties have been determined by comparing the parameters derived from the high resolution data with the ones derived from medium resolution spectra. Helium abundances have been measured with high accuracy. Besides the known correlation of helium abundance with temperature, two distinct sequences in helium abundance have been confirmed. Significant isotopic shifts of helium lines due to an enrichment in $^{3}$He have been found in the spectra of 8 sdBs. Most of these stars cluster in a small temperature range between $27\\,000\\,{\\rm K}$ and $31\\,000\\,{\\rm K}$ very similar to the known $^{3}$He-rich main sequence B stars, which also cluster in such a small strip, but at ...

  16. Maximal temperature measurement of the hot residues emitted in the Ar + Au reaction at 60 MeV/u; Mesure de la temperature maximale des residus chauds emis dans la reaction Ar + Au a 60 MeV/u

    Energy Technology Data Exchange (ETDEWEB)

    Lecolley, F-R. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire

    1996-06-01

    The work presented in this thesis relates to the formation and decay by evaporating light particles of hot heavy residue produced in the 60 MeV per nucleon Ar + Au reaction. Using DeMoN facility has allowed to measure the initial temperature and the evaporated neutron multiplicity associated with heavy residue. Hottest observed residues sustain a 6 MeV temperature, have a 1.0 cm/ns recoil velocity, evaporate about 22 neutrons and are produced with a non negligible cross section (50 mbarn). All the characteristics of this residue production are in good agreement with the prediction of a BNV calculations coupled with a statistical decay code. (author) 33 refs.

  17. Cosmic Ray Helium Hardening

    CERN Document Server

    Ohira, Yutaka

    2010-01-01

    Recent observations by CREAM, ATIC-2 and PAMELA experiments suggest that (1) the spectrum of cosmic ray (CR) helium is harder than that of CR proton below the knee $10^15 eV$ and (2) all CR spectra become hard at $\\gtrsim 10^{11} eV/n$. We propose a new picture that higher energy CRs are generated in more helium-rich region to explain the hardening (1) without introducing different sources for CR helium. The helium to proton ratio at $\\sim 100$ TeV exceeds the Big Bang abundance $Y=0.25$ by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in the chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium when escaping from the supernova remnant (SNR) shock. We provide a simple analytical spectrum that also fits well the hardening (2) because of the decreasing Mach number in the hot superbubble with $\\sim 10^6$ K. Our model predicts hard and con...

  18. 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...

  19. 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)

  20. MESUR: metrics from scholarly usage of resources

    CERN Document Server

    CERN. Geneva

    2007-01-01

    The MESUR project is constructing a large-scale semantic model of the scholarly community that seamlessly integrates a wide range of bibliographic, citation and usage data. Functioning as a reference data set, this model is analyzed to characterize the intricate networks of typed relationships that exist in the scholarly community. The resulting ...

  1. 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.

  2. MESUR metrics from scholarly usage of resources

    CERN Document Server

    CERN. Geneva; Van de Sompel, Herbert

    2007-01-01

    Usage data is increasingly regarded as a valuable resource in the assessment of scholarly communication items. However, the development of quantitative, usage-based indicators of scholarly impact is still in its infancy. The Digital Library Research & Prototyping Team at the Los Alamos National Laboratory's Research library has therefore started a program to expand the set of usage-based tools for the assessment of scholarly communication items. The two-year MESUR project, funded by the Andrew W. Mellon Foundation, aims to define and validate a range of usage-based impact metrics, and issue guidelines with regards to their characteristics and proper application. The MESUR project is constructing a large-scale semantic model of the scholarly community that seamlessly integrates a wide range of bibliographic, citation and usage data. Functioning as a reference data set, this model is analyzed to characterize the intricate networks of typed relationships that exist in the scholarly community. The resulting c...

  3. Cross section measurements of the processes occurring in the fragmentation of H{sub n}{sup +} (3 {<=} n {<=} 35) hydrogen clusters induced by high speed (60 keV/u) collisions on helium atoms; Mesure des sections efficaces des differents processus intervenant dans la fragmentation d`agregats d`hydrogene H{sub n}{sup +} (3 {<=} n {<=} 35) induite par collision a haute vitesse (60 keV/u) sur un atome d`helium

    Energy Technology Data Exchange (ETDEWEB)

    Louc, Sandrine [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1997-09-15

    Different processes involved in the fragmentation of ionised hydrogen clusters H{sub 3} + (H{sub 2}){sub (n-3)/2} (n = 5-35) have been studied in the same experiment: the fragmentation of the cluster is induced by the collision with an helium atom at high velocity ({approx_equal} c/100). The collision is realised in reversed kinematic - clusters are accelerated - which allows the detection of neutral and charged fragments. The different channels of fragmentation are identified by using coincidence techniques. For all the cluster sizes studied the capture cross sections of one electron of the target by the cluster is equal to the capture cross section of the H{sub 3}{sup +} ion. In the same way, the dissociation cross section of the H{sub 3}{sup +} core of the cluster does not depend on cluster size. These fragmentation processes are due to the interaction of H{sub 3}{sup +} core of the cluster and the helium atom without ionization of another component of the cluster. On the contrary, the cross sections of loss of one, two and three molecules by the cluster and the dissociation cross section of the cluster in all its molecular components depends strongly on the cluster size. This dependence is different from the one measured for the metastable decay of the cluster. Thus, the process of loss of molecules induced by a collision should correspond to a different dissociation mechanism. In regard of the singularities observed for the size dependence, the H{sub 9}{sup +}, H{sub 15}{sup +}, H{sub 19}{sup +} and H{sub 29}{sup +} clusters could be the `core` of the biggest clusters. These observation are in agreement with the size effects of smaller magnitude observed for the dissociation cross section (all the processes). The values of the cross section for the process of at least one ionization of the cluster indicate that about 80% of the fragmentation events result from this process. (author) 114 refs., 74 figs., 9 tabs.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-15

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

  5. 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

  6. Les mesures de métrologie pour le CLIC

    CERN Document Server

    Cherif, A

    2008-01-01

    Le projet CLIC est en tout point un défi technique majeur ; c?est le cas également pour la mesure dimensionnelle. Quels sont les équipements et les méthodes qui permettent de caractériser les pièces avec une incertitude de mesure aussi réduite que possible, vu les tolérances micrométriques imposées ? Afin de répondre à cette question, une veille technologique a été maintenue sur une longue période. Les acteurs relevants ont été contactés pour bénéficier d?une ouverture sur les dernières avancées dans le domaine. Différentes techniques ont été étudiées et comparées telles que la digitalisation, la tomographie X, la mesure tridimensionnelle. L'assemblage de haute précision des composants est aussi primordial. Sa mise en ?uvre sous un microscope optique ou à l'aide d'une machine tridimensionnelle est en cours d?étude. L'exposé traitera aussi de la mesure de rugosité, un domaine où nous disposons de moyens adaptés aux exigences spécifiques du projet.

  7. High resolution spectroscopy of six new extreme helium stars

    Science.gov (United States)

    Heber, U.; Jones, G.; Drilling, J. S.

    1986-01-01

    High resolution spectra of six newly discovered extreme helium stars are presented. LSS 5121 is shown to be a spectroscopical twin of the hot extreme helium star HD 160641. A preliminary LTE analysis of LSS 3184 yielded an effective temperature of 22,000 K and a surface gravity of log g = 3.2. Four stars form a new subgroup, classified by sharp-lined He I spectra and pronounced O II spectra, and it is conjectured that these lie close to the Eddington limit. The whole group of extreme helium stars apparently is inhomogeneous with respect to luminosity to mass ratio and chemical composition.

  8. Performance testing of an air/water heat pump using CO{sub 2} (R744) as refrigerant for the preparation of sanitary hot water in a hospital; Mesures des donnees energetiques d'une pompe a chaleur air/eau au CO{sub 2} (R744) pour preparation d'eau chaude sanitaire dans un hopital

    Energy Technology Data Exchange (ETDEWEB)

    Anstett, P.

    2006-07-01

    This final report prepared for the Swiss Federal Office of Energy (SFOE) describes the monitoring equipment and the results of performance tests made on a prototype heat pump of 60 kW power output used for hot water production at the hospital of Le Locle, Switzerland. The heat pump uses carbon dioxide (R744) as the working fluid and ambient air as the heat source. The heat output and the coefficient of performance for various values of cold water temperature and air temperature have been measured. The practically measured values of heat output and COP showed a low reproducibility and remained far behind the theoretical values given by the manufacturer. Instead of producing hot water at 80 {sup o}C as intended originally the authors recommend to use the heat pump only for preheating the water to 60 {sup o}C.

  9. 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...

  10. Rayleigh scattering in the atmospheres of hot stars

    CERN Document Server

    Fišák, Jakub; Munzar, Dominik; Kubát, Jiří

    2016-01-01

    Rayleigh scattering is a result of an interaction of photons with bound electrons. Rayleigh scattering is mostly neglected in calculations of hot star model atmospheres because most of the hydrogen atoms are ionized and the heavier elements have a lower abundance than hydrogen. In atmospheres of some chemically peculiar stars, helium overabundant regions containing singly ionized helium are present and Rayleigh scattering can be a significant opacity source. We evaluate the contribution of Rayleigh scattering by neutral hydrogen and singly ionized helium in the atmospheres of hot stars with solar composition and in the atmospheres of helium overabundant stars. We computed several series of model atmospheres using the TLUSTY code and emergent fluxes using the SYNSPEC code. These models describe atmospheres of main sequence B-type stars with different helium abundance. We used an existing grid of models for atmospheres with solar chemical composition and we calculated an additional grid for helium-rich stars wi...

  11. Hot Money, Hot Potato

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    International hot money flowing into Chinese capital markets has caught the attention of Chinese watchdogs The Chinese are not the only ones feasting on the thriving property and stock markets. Apparently, these markets are the targets of international h

  12. Advances in Helium Cryogenics

    Science.gov (United States)

    Sciver, S. W. Van

    This review provides a survey of major advances that have occurred in recent years in the area of helium cryogenics. Helium-temperature cryogenics is the enabling technology for a substantial and growing number of low-temperature systems from superconducting magnets to space-based experimental facilities. In recent years there have been many advances in the technology of low-temperature helium, driven mostly by new applications. However, to keep the review from being too broad, this presentation focuses mainly on three of the most significant advances. These are: (1) the development of large-scale recuperative refrigeration systems mainly for superconducting magnet applications in accelerators and other research facilities; (2) the use of stored superfluid helium (He II) as a coolant for spacebased astrophysics experiments; and (3) the application of regenerative cryocoolers operating at liquid helium temperatures primarily for cooling superconducting devices. In each case, the reader should observe that critical technologies were developed to facilitate these applications. In addition to these three primary advances, other significant helium cryogenic technologies are briefly reviewed at the end of this chapter, along with some vision for future developments in these areas.

  13. Rayleigh scattering in the atmospheres of hot stars

    Science.gov (United States)

    Fišák, J.; Krtička, J.; Munzar, D.; Kubát, J.

    2016-05-01

    Context. Rayleigh scattering is a result of an interaction of photons with bound electrons. Rayleigh scattering is mostly neglected in calculations of hot star model atmospheres because most of the hydrogen atoms are ionized and the heavier elements have a lower abundance than hydrogen. In atmospheres of some chemically peculiar stars, helium overabundant regions containing singly ionized helium are present and Rayleigh scattering can be a significant opacity source. Aims: We evaluate the contribution of Rayleigh scattering by neutral hydrogen and singly ionized helium in the atmospheres of hot stars with solar composition and in the atmospheres of helium overabundant stars. Methods: We computed several series of model atmospheres using the TLUSTY code and emergent fluxes using the SYNSPEC code. These models describe atmospheres of main sequence B-type stars with different helium abundance. We used an existing grid of models for atmospheres with solar chemical composition and we calculated an additional grid for helium-rich stars with N(He)/N(H) = 10. Results: Rayleigh scattering by neutral hydrogen can be neglected in atmospheres of hot stars, while Rayleigh scattering by singly ionized helium can be a non-negligible opacity source in some hot stars, especially in helium-rich stars.

  14. Kinematics of Subluminous O and B Stars by Surface Helium Abundance

    Science.gov (United States)

    Martin, P.; Jeffery, C. S.; Naslim, N.; Woolf, V. M.

    2016-12-01

    The majority of hot subdwarf stars are low-mass core-helium-burning stars. Their atmospheres are generally helium deficient; however a minority have extremely helium-rich surfaces. An additional fraction have an intermediate surface-helium abundance, occasionally accompanied by peculiar abundances of other elements. We have identified a sample of 88 hot subdwarfs including 38 helium-deficient, 27 intermediate-helium and 23 extreme-helium stars for which radial-velocity and proper-motion measurements, together with distances, allow a calculation of Galactic space velocities. We have investigated the kinematics of these three groups to determine whether they belong to similar or different Galactic populations. The majority of helium-deficient subdwarfs in our sample show a kinematic distribution similar to that of thick disk stars. Helium-rich sdBs show a more diverse kinematic distribution. Although the majority are probably disk stars, a minority show a much higher velocity dispersion consistent with membership of a Galactic halo population. Several of the halo subdwarfs are members of the class of "heavy-metal" subdwarfs discovered by Naslim et al. (2011, 2013).

  15. Hot Subluminous Stars

    Science.gov (United States)

    Heber, U.

    2016-08-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically highly peculiar and provide a laboratory to study diffusion processes that cause these anomalies. The most obvious anomaly lies with helium, which may be a trace element in the atmosphere of some stars (sdB, sdO) while it may be the dominant species in others (He-sdB, He-sdO). Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich versus He-poor hot subdwarf stars of the globular clusters ω Cen and NGC 2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope (CE) phase of evolution. Because the binaries are detached they provide a clean-cut laboratory to study this important but yet poorly understood phase of stellar evolution. Hot subdwarf binaries with sufficiently massive white dwarf companions are viable candidate progenitors of type Ia supernovae both in the double degenerate as well as in the single degenerate scenario as helium donors for double detonation supernovae. The hyper-velocity He-sdO star US 708 may be the surviving donor of such a double detonation supernova. Substellar companions to sdB stars have also been found. For HW Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the acoustic-mode pulsator V391 Peg was the first discovery of a planet that survived the red giant evolution of its host star. Evidence for Earth-size planets to two pulsating sdB stars have been reported and circumbinary giant planets or brown dwarfs have been found around HW

  16. La mesure du travail dans la famille : création, définition et mesure du travail parental

    OpenAIRE

    Marie-Agnès Barrère-Maurisson

    2012-01-01

    Comment les transformations de la famille, mais aussi celles de l'emploi, ont-elles conduit à de nouvelles pratiques, spécifiques et distinctes du travail domestique à proprement parler, autour de la prise en charge des enfants par la famille ? Commant ce travail particulier, le parental, a-t-il pu être isolé et défini ? Comment a-t-il été évalué, en référence à quelle mesure étalon, et pourquoi ?.

  17. Broken symmetry makes helium

    CERN Multimedia

    Gray, P L

    2003-01-01

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

  18. MESUR: USAGE-BASED METRICS OF SCHOLARLY IMPACT

    Energy Technology Data Exchange (ETDEWEB)

    BOLLEN, JOHAN [Los Alamos National Laboratory; RODRIGUEZ, MARKO A. [Los Alamos National Laboratory; VAN DE SOMPEL, HERBERT [Los Alamos National Laboratory

    2007-01-30

    The evaluation of scholarly communication items is now largely a matter of expert opinion or metrics derived from citation data. Both approaches can fail to take into account the myriad of factors that shape scholarly impact. Usage data has emerged as a promising complement to existing methods o fassessment but the formal groundwork to reliably and validly apply usage-based metrics of schlolarly impact is lacking. The Andrew W. Mellon Foundation funded MESUR project constitutes a systematic effort to define, validate and cross-validate a range of usage-based metrics of schlolarly impact by creating a semantic model of the scholarly communication process. The constructed model will serve as the basis of a creating a large-scale semantic network that seamlessly relates citation, bibliographic and usage data from a variety of sources. A subsequent program that uses the established semantic network as a reference data set will determine the characteristics and semantics of a variety of usage-based metrics of schlolarly impact. This paper outlines the architecture and methodology adopted by the MESUR project and its future direction.

  19. Education in Helium Refrigeration

    Science.gov (United States)

    Gistau Baguer, G. M.

    2004-06-01

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

  20. ``Astrophysique sur Mesure'', E-learning in Astronomy and Astrophysics

    Science.gov (United States)

    Mosser, Benoît; Delsanti, Audrey; Guillaume, Damien; Balança, Christian; Balkowski, Chantal

    2011-06-01

    ``Astrophysique sur Mesure'' (astrophysics made-to-measure) is a set of e-learning programmes started 4 years ago at the Paris Observatory. In order to deliver attractive and efficient programmes, we have added many multimedia tools to usual lectures: animations, Java applets. The programmes are presented on two different platforms. The first one offers the content of all the lectures in free access. A second platform with restricted access is provided to registered students taking part in the e-learning program and benefiting from the help of tutors. The development of these programs helps to increase the sphere of influence of astronomy taught at the Paris Observatory, hence to increase the presence of astronomy in various degree courses. Instead of teaching classical astronomy lectures to a happy few, we can bring astronomy and astrophysics to a wider audience.

  1. Helium anion formation inside helium droplets

    Science.gov (United States)

    Maalouf, Elias Jabbour Al; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  2. Hot microswimmers

    Science.gov (United States)

    Kroy, Klaus; Chakraborty, Dipanjan; Cichos, Frank

    2016-11-01

    Hot microswimmers are self-propelled Brownian particles that exploit local heating for their directed self-thermophoretic motion. We provide a pedagogical overview of the key physical mechanisms underlying this promising new technology. It covers the hydrodynamics of swimming, thermophoresis and -osmosis, hot Brownian motion, force-free steering, and dedicated experimental and simulation tools to analyze hot Brownian swimmers.

  3. Helium in Earth's early core

    Science.gov (United States)

    Bouhifd, M. A.; Jephcoat, Andrew P.; Heber, Veronika S.; Kelley, Simon P.

    2013-11-01

    The observed escape of the primordial helium isotope, 3He, from the Earth's interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth's interior have been invoked to account for variations in the 3He/4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth's iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16GPa and 3,000K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal-silicate helium partition coefficients that range between 4.7×10-3 and 1.7×10-2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium, we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.

  4. Hot subluminous stars

    CERN Document Server

    Heber, Ulrich

    2016-01-01

    Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Strikingly, the distribution in the Hertzsprung-Russell diagram of He-rich vs. He-poor hot subdwarf stars of the globular clusters omega Cen and NGC~2808 differ from that of their field counterparts. The metal-abundance patterns of hot subdwarfs are typically characterized by strong deficiencies of some lighter elements as well as large enrichments of heavy elements. A large fraction of sdB stars are found in close binaries with white dwarf or very low-mass main sequence companions, which must have gone through a common-envelope phase of evolution.They provide a clean-cut laboratory to study this important but yet purely understood phase of stellar evolution. Substellar companions to sdB stars have also been found. For HW~Vir systems the companion mass distribution extends from the stellar into the brown dwarf regime. A giant planet to the pulsator V391 ...

  5. High Efficiency Regenerative Helium Compressor Project

    Data.gov (United States)

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

  6. Cavitation in liquid helium

    Energy Technology Data Exchange (ETDEWEB)

    Finch, R. D.; Kagiwada, R.; Barmatz, M.; Rudnick, I.

    1963-11-15

    Ultrasonic cavitation was induced in liquid helium over the temperature range 1.2 to 2.3 deg K, using a pair of identical transducers. The transducers were calibrated using a reciprocity technique and the cavitation threshold was determined at 90 kc/s. It was found that this threshold has a sharp peak at the lambda point, but is, at all temperatures quite low, with an approximate range of 0.001 to 0.01 atm. The significance of the results is discussed. (auth)

  7. Abundance analyses of cool extreme helium stars

    CERN Document Server

    Pandey, G; Lambert, D L; Jeffery, C S; Asplund, M; Pandey, Gajendra; Lambert, David L.; Asplund, Martin

    2001-01-01

    Extreme helium stars (EHe) with effective temperatures from 8000K to 13000K are among the coolest EHe stars and overlap the hotter R CrB stars in effective temperature. The cool EHes may represent an evolutionary link between the hot EHes and the R CrBs. Abundance analyses of four cool EHes are presented. To test for an evolutionary connection, the chemical compositions of cool EHes are compared with those of hot EHes and R CrBs. Relative to Fe, the N abundance of these stars is intermediate between those of hot EHes and R CrBs. For the R CrBs, the metallicity M derived from the mean of Si and S appears to be more consistent with the kinematics than that derived from Fe. When metallicity M derived from Si and S replaces Fe, the observed N abundances of EHes and R CrBs fall at or below the upper limit corresponding to thorough conversion of initial C and O to N. There is an apparent difference between the composition of R CrBs and EHes; the former having systematically higher [N/M] ratios. The material present...

  8. Nucleosynthesis in Hot and Dense Media

    CERN Document Server

    Masood, Samina S

    2014-01-01

    We study the finite temperature and density effects on beta decay rates to compute their contributions to nucleosynthesis. QED type corrections to beta decay from the hot and dense background are estimated in terms of the statistical corrections to the self-mass of an electron. For this purpose, we re-examine the hot and dense background contributions to the electron mass and compute its effect to the beta decay rate, helium yield, energy density of the universe as well as the change in neutrino temperature from the first order contribution to the self-mass of electrons during these processes. We explicitly show that the thermal contribution to the helium abundance at T = m of a cooling universe 0.045 % is higher than the corresponding contribution to helium abundance of a heating universe 0.031% due to the existence of hot fermions before the beginning of nucleosynthesis and their absence after the nucleosynthesis, in the early universe. Thermal contribution to helium abundance was a simple quadratic functio...

  9. Regimes Of Helium Burning

    CERN Document Server

    Timmes, F X

    2000-01-01

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

  10. Helium diffusion in carbonates

    Science.gov (United States)

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

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  11. HOT 2012

    DEFF Research Database (Denmark)

    Lund, Henriette Romme

    Undersøgelse af, hvad der er hot - og hvad der burde være hot på læseområdet med 21 læsekyndige. Undersøgelsen er gennemført siden 2010. HOT-undersøgelsen er foretaget af Nationalt Videncenter for Læsning - Professionshøjskolerne i samarb. med Dansklærerforeningen...

  12. 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).

  13. Luminescence studies of trace gases through metastable transfer in cold helium jets

    Science.gov (United States)

    Wilde, Scott Colton

    gas and the rotational temperature determined spectroscopically should be in agreement. It was found that metastable transfer from helium in the jet provides enough energy to create a population of hot molecules of nitrogen that never reach thermal equilibrium with the buffer gas which is almost entirely made up of ground state helium atoms. This effect can be corrected for by adding some significant changes to the optical setup but are not outside the realm of possibility as they have been designed and built for other experiments. Therefore the rotational spectra of nitrogen could be used as an in situ thermometer at cryogenic temperatures with metastable helium present provided the hot molecule contribution due to collisions of the second kind of nitrogen and helium is measured and removed.

  14. Effects of helium on titanium films and the helium diffusion

    Institute of Scientific and Technical Information of China (English)

    SONG YingMin; LUO ShunZhong; LONG XingGui; AN Zhu; LIU Ning; PANG HongChao; WU XingChun; YANG BenFu; ZHENG SiXiao

    2008-01-01

    Using direct current-magnetron sputtering, Helium-trapped Ti films with a He/Ar mixture was studied. The relative helium content, helium depth profiles for the Ti films and crystallization capacity were analyzed by Enhanced Proton Backscattering Spectrometry (EPBS) and X-ray diffraction (XRD). It was found that helium diffusion enhanced as more helium trapping into Ti films, and the He holding ratios were 95.9%, 94.9%, 93.9%, 82.8% when the Ti films with the He/Ti of concentrations of 9.7 at.Q, 19.5 at.Q, 19.7 at.Q, 48.3 at.% were measured again 4 months later, respectively. The diffraction peaks be-came weak and wider, the peak of (002) plane was shifted to smaller diffraction angles and the relevant interplanar spacing d(hkl) increased gradually as more helium trapping into Ti films. The main peak was made trending to the (101) plane by both higher deposition temperature and more helium trapping.

  15. Le temps mesurable, réversible, insaisissable ?

    CERN Document Server

    Fink, Martin; Leduc , Michèle

    2016-01-01

    Depuis l'Antiquité, la nature du temps a fasciné nombre de grands penseurs. Cet ouvrage expose ce que la physique est capable de dire aujourd'hui sur le sujet. La mesure du temps, ou plus exactement celle d'une durée, se fait grâce à des horloges atomiques dont l'exactitude peut atteindre une seconde sur plusieurs milliards d'années. Nous décrivons la façon dont s'effectue le transfert du temps qui permet la synchronisation d'horloges en différents points de la Terre ou de l'espace au milliardième de seconde près, ou même mieux. Les relativités, restreinte et générale, ont bouleversé notre conception du temps et ont un impact considérable sur certains problèmes de la vie quotidienne comme l'utilisation du GPS. On abandonne l'idée d'un temps absolu, le temps devient multiple et insaisissable, et peut-être même une illusion. Enfin la flèche du temps, ou l'irréversibilité, implique que les phénomènes physiques se déroulent toujours dans un sens déterminé, en relation avec la croissan...

  16. Alkali-helium snowball complexes formed on helium nanodroplets.

    Science.gov (United States)

    Müller, S; Mudrich, M; Stienkemeier, F

    2009-07-28

    We systematically investigate the formation and stability of snowballs formed by femtosecond photoionization of small alkali clusters bound to helium nanodroplets. For all studied alkali species Ak = (Na,K,Rb,Cs) we observe the formation of snowballs Ak(+)He(N) when multiply doping the droplets. Fragmentation of clusters Ak(N) upon ionization appears to enhance snowball formation. In the case of Na and Cs we also detect snowballs Ak(2) (+)He(N) formed around Ak dimer ions. While the snowball progression for Na and K is limited to less than 11 helium atoms, the heavier atoms Rb and Cs feature wide distributions at least up to Ak(+)He(41). Characteristic steps in the mass spectra of Cs-doped helium droplets are found at positions consistent with predictions on the closure of the first shell of helium atoms around the Ak(+) ion based on variational Monte Carlo simulations.

  17. 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.

  18. Transferring superfluid helium in space

    Science.gov (United States)

    Kittel, Peter

    1986-01-01

    A simple thermodynamic model of a transfer system for resupplying liquid helium in space is presented, with application to NASA projects including the Space Infrared Telescope Facility, the Large Deployable Reflector, and the Hubble Space Telescope. The relations between different thermodynamic regimes that can be expected in the transfer line are used to study the relative efficiencies of various possible transfer techniques. Low heat leak into the transfer line, particularly at point sources such as the coupling, is necesssary for efficient transfer of liquid helium, and proper selection of supply tank temperature is important during helium resupply.

  19. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  20. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  1. Resistor monitors transfer of liquid helium

    Science.gov (United States)

    Hesketh, W. D.

    1966-01-01

    Large resistance change of a carbon resistor at the liquid helium temperature distinguishes between the transfer of liquid helium and gaseous helium into a closed Dewar. The resistor should be physically as small as possible to reduce the heat load to the helium.

  2. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures

  3. Behavior of W-based materials in hot helium gas

    Directory of Open Access Journals (Sweden)

    J. Matějíček

    2016-12-01

    A number of W-based materials (pure tungsten and some of its alloys prepared by powder metallurgy techniques was exposed to He atmosphere at 720ºC and 500kPa for 500h. Morphological surface changes were observed by SEM, chemical and phase composition was analyzed by EDS and XRD, respectively. The internal microstructure was observed by a combination of SEM, FIB and TEM techniques. Mechanical properties were determined by instrumented indentation. Some alloys developed a thin oxide layer, in some cases new morphological features were observed, while some samples remained mostly intact. The observed changes are correlated with specific compositions and microstructures.

  4. Numerical simulation of losses along a natural circulation helium loop

    Science.gov (United States)

    Knížat, Branislav; Urban, František; Mlkvik, Marek; RidzoÅ, František; Olšiak, Róbert

    2016-06-01

    A natural circulation helium loop appears to be a perspective passive method of a nuclear reactor cooling. When designing this device, it is important to analyze the mechanism of an internal flow. The flow of helium in the loop is set in motion due to a difference of hydrostatic pressures between cold and hot branch. Steady flow at a requested flow rate occurs when the buoyancy force is adjusted to resistances against the flow. Considering the fact that the buoyancy force is proportional to a difference of temperatures in both branches, it is important to estimate the losses correctly in the process of design. The paper deals with the calculation of losses in branches of the natural circulation helium loop by methods of CFD. The results of calculations are an important basis for the hydraulic design of both exchangers (heater and cooler). The analysis was carried out for the existing model of a helium loop of the height 10 m and nominal heat power 250 kW.

  5. Portable Tester Friction (PFT). Mesures du coefficient de frottement dynamique de revêtements de sol

    OpenAIRE

    Marchal, P.; Jacques, M.

    2014-01-01

    Le Portable Tester Friction (PFT) est un appareil destiné à mesurer le coefficient de frottement dynamique d’un revêtement de sol en laboratoire et sur site. Ce document décrit le protocole de mesure avec le PFT et les résultats de mesures effectuées sur un panel de quinze revêtements de sol de caractéristiques différentes (matériaux, états de surface) réalisées en présence de deux polluants (huile et solution d’eau). Le PFT présente une très bonne sensibilité et une très bonne répétabilité. ...

  6. Mesure optimale de tilt et déplacement d'un faisceau gaussien

    Science.gov (United States)

    Delaubert, V.; Treps, N.; Fabre, C.; Harb, C.; Lam, P. K.; Bachor, H.

    2006-10-01

    Nous réalisons une expérience de mesure optimale de petits déplacements d'un faisceau gaussien TEM{00}, basée sur une détection homodyne employant un oscillateur local TEM{10}. Nous montrons une amélioration de 56% du signal détecté par rapport à une détection à deux zones. Ce nouveau dispositif permet également de mesurer de façon optimale de petites valeurs de tilt, la quantité conjuguée du déplacement. Enfin, nous montrons que la compression du mode TEM{10} du faisceau incident permet une mesure de déplacement au delà de la limite quantique standard.

  7. WAVE PROPAGATION in the HOT DUCT of VHTR

    Energy Technology Data Exchange (ETDEWEB)

    Richard Schultz; Jim C. P. Liou

    2013-07-01

    In VHTR, helium from the reactor vessel is conveyed to a power conversion unit through a hot duct. In a hypothesized Depressurized Conduction Cooldown event where a rupture of the hot duct occurs, pressure waves will be initiated and reverberate in the hot duct. A numerical model is developed to quantify the transients and the helium mass flux through the rupture for such events. The flow path of the helium forms a closed loop but only the hot duct is modeled in this study. The lower plum of the reactor vessel and the steam generator are treated as specified pressure and/or temperature boundary to the hot duct. The model is based on the conservation principles of mass, momentum and energy, and on the equations of state for helium. The numerical solution is based on the method of characteristics with specified time intervals with a predictor and corrector algorithm. The rupture sub-model gives reasonable results. Transients induced by ruptures with break area equaling 20%, 10%, and 5% of the duct cross-sectional area are described.

  8. ITER helium ash accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, J.T.; Hillis, D.L.; Galambos, J.; Uckan, N.A. (Oak Ridge National Lab., TN (USA)); Dippel, K.H.; Finken, K.H. (Forschungszentrum Juelich GmbH (Germany, F.R.). Inst. fuer Plasmaphysik); Hulse, R.A.; Budny, R.V. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-01-01

    Many studies have shown the importance of the ratio {upsilon}{sub He}/{upsilon}{sub E} in determining the level of He ash accumulation in future reactor systems. Results of the first tokamak He removal experiments have been analysed, and a first estimate of the ratio {upsilon}{sub He}/{upsilon}{sub E} to be expected for future reactor systems has been made. The experiments were carried out for neutral beam heated plasmas in the TEXTOR tokamak, at KFA/Julich. Helium was injected both as a short puff and continuously, and subsequently extracted with the Advanced Limiter Test-II pump limiter. The rate at which the He density decays has been determined with absolutely calibrated charge exchange spectroscopy, and compared with theoretical models, using the Multiple Impurity Species Transport (MIST) code. An analysis of energy confinement has been made with PPPL TRANSP code, to distinguish beam from thermal confinement, especially for low density cases. The ALT-II pump limiter system is found to exhaust the He with maximum exhaust efficiency (8 pumps) of {approximately}8%. We find 1<{upsilon}{sub He}/{upsilon}{sub E}<3.3 for the database of cases analysed to date. Analysis with the ITER TETRA systems code shows that these values would be adequate to achieve the required He concentration with the present ITER divertor He extraction system.

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

    CERN Document Server

    Brooks, Jared; Schwab, Josiah; Paxton, Bill

    2016-01-01

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

  10. MESURE DE LA QUALITE DE LA DIVULGATION SOCIETALE DES ENTREPRISES FRANCAISES

    OpenAIRE

    Ben Rhouma, Amel

    2006-01-01

    International audience; Le propos de ce papier est de présenter quelques résultats empiriques concernant la mesure du niveau et de la qualité de la divulgation sociétale. Notre outil de mesure est une grille de codage similaire à celle de Wiseman (1982) et Cormier et Magnan (1999 et 2003) et adaptée au contexte légal et réglementaire français, les résultats montrent qu'il y a une progression dans le niveau et la qualité de divulgation sociétale des entreprises françaises.

  11. Bed system performance in helium circulation mode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yean Jin; Jung, Kwang Jin; Ahn, Do Hee; Chung, Hong Suk [UST, Daejeon (Korea, Republic of); Kang, Hee Suk [KAERI, Daejeon (Korea, Republic of); Yun, Sei Hun [NFRI, Deajeon (Korea, Republic of)

    2016-05-15

    As a part of the International Thermonuclear Experimental Reactor (ITER) Project, We have conducted an experiment for storing hydrogen to depleted uranium and zirconium cobalt. The helium blanket effect has been observed in experiments using metal hydrides. The collapse of the hydrogen isotopes are accompanied by the decay heat and helium-3. Helium-3 dramatically reduces the hydrogen isotope storage capacity by surrounding the metal. This phenomenon is called a helium blanket effect. In addition the authors are working on the recovery and removal techniques of helium-3. In this paper, we discuss the equipment used to test the helium blanket effect and the results of a helium circulation experiment. The helium-3 produced surrounds the storage material surface and thus disturbs the reaction of the storage material and the hydrogen isotope. Even if the amount of helium-3 is small, the storage capacity of the SDS bed significantly drops. This phenomenon is the helium blanket effect. To resolve this phenomenon, a circulating loop was introduced. Using a circulating system, helium can be separated from the storage material. We made a helium loop that includes a ZrCo bed. Then using a metal bellows pump, we tested the helium circulation.

  12. Temperature measurements in thermal plasmas; Mesures de temperatures dans les plasmas thermiques

    Energy Technology Data Exchange (ETDEWEB)

    Fauchais, P.; Coudert, J.F. [Limoges Univ., 87 (France)

    1996-05-01

    Thermal plasmas are characterized by a high pressure (10{sup 4} to 10{sup 6} Pa) and a high density of particles. Plasmas considered in this paper are produced by electric discharges, arcs, injection torches with cold or hot cathodes, water vortex torches, RF devices and are characterized by temperatures ranging from 6000 to 40000 K and ionization energies ranging from 13.5 and 16 eV (in argon, argon-hydrogen, nitrogen, nitrogen-hydrogen, argon-helium, air, oxygen, CO{sub 2} or water). Temperature measurements in thermal plasmas are difficult due to their extreme luminosity, flow rate and thermal flux, and to their temperature and flow rate gradients. The most common measurement methods are the emission spectroscopy, the laser scattering (Rayleigh, Thomson and coherent anti-Stokes Raman scattering) and the enthalpy probes. The first two methods are non-intrusive, while the last method is intrusive. This paper gives first some general remarks about the principles of each technique and focusses on the problem of fluctuations due to the plasma jet instabilities. Then, it describes briefly each technique and gives some examples of results. Finally, it compares the spectroscopic measurements with other measurements. (J.S.) 80 refs.

  13. Qualification de l’instrumentation pour des mesures nanométriques

    CERN Document Server

    Bernard, E

    2009-01-01

    Prise en main de l’instrumentation dédiée aux mesures de vibrations dans le domaine du nanomètre et mise en service de nouveaux capteurs. Développement de l’acquisition des données sous Labview, et analyse des signaux dans le domaine fréquentiel sous Matlab.

  14. Rogue mantle helium and neon.

    Science.gov (United States)

    Albarède, Francis

    2008-02-15

    The canonical model of helium isotope geochemistry describes the lower mantle as undegassed, but this view conflicts with evidence of recycled material in the source of ocean island basalts. Because mantle helium is efficiently extracted by magmatic activity, it cannot remain in fertile mantle rocks for long periods of time. Here, I suggest that helium with high 3He/4He ratios, as well as neon rich in the solar component, diffused early in Earth's history from low-melting-point primordial material into residual refractory "reservoir" rocks, such as dunites. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoir rocks being stretched and tapped to different extents during melting.

  15. 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

  16. Helium release during shale deformation: Experimental validation

    Science.gov (United States)

    Bauer, Stephen J.; Gardner, W. Payton; Heath, Jason E.

    2016-07-01

    This work describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

  17. Hot Tickets

    Science.gov (United States)

    Fox, Bette-Lee; Hoffert, Barbara; Kuzyk, Raya; McCormack, Heather; Williams, Wilda

    2008-01-01

    This article describes the highlights of this year's BookExpo America (BEA) held at the Los Angeles Convention Center. The attendees at BEA had not minded that the air was recycled, the lighting was fluorescent, and the food was bad. The first hot book sighting came courtesy of Anne Rice. Michelle Moran, author of newly published novel, "The…

  18. 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.

  19. Negative ions in liquid helium

    Science.gov (United States)

    Khrapak, A. G.; Schmidt, W. F.

    2011-05-01

    The structure of negative ions in liquid 4He is analyzed. The possibility of cluster or bubble formation around impurity ions of both signs is discussed. It is shown that in superfluid helium, bubbles form around negative alkaline earth metal ions and clusters form around halogen ions. The nature of "fast" and "exotic" negative ions is also discussed. It is assumed that "fast" ions are negative ions of helium excimer molecules localized inside bubbles. "Exotic" ions are stable negative impurity ions, which are always present in small amounts in gas discharge plasmas. Bubbles or clusters with radii smaller the radius of electron bubbles develop around these ions.

  20. On the origin of microturbulence in hot stars

    NARCIS (Netherlands)

    M. Cantiello; N. Langer; I. Brott; A. de Koter; S.N. Shore; J.S. Vink; A. Voegler; S.C. Yoon

    2008-01-01

    We present results from the first extensive study of convection zones in the envelopes of hot massive stars, which are caused by opacity peaks associated with iron and helium ionization. These convective regions can be located very close to the stellar surface. The region in the Hertzsprung-Russel d

  1. Ageing of palladium tritide: mechanical characterization, helium state and modelling; Vieillissement du tritiure de palladium: caracterisation mecanique, etat de l'helium et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Segard, M.

    2010-11-29

    deux modeles traitant, d'une part, de la germination des bulles d'helium-3 (utilisation d'un automate cellulaire) et, d'autre part, de la croissance des bulles (mecanique des milieux continus). Ces modeles etaient fonctionnels, mais leur utilisation etait limitee par le manque de donnees experimentales d'entree et de recalage. Ce travail de these a donc consiste a acquerir les donnees experimentales les plus pertinentes pour ameliorer la modelisation du vieillissement du tritiure de palladium. La premiere partie de ce travail a consiste a estimer les proprietes mecaniques du tritiure de palladium (limite d'elasticite, contrainte maximale, loi de comportementale), deduites de celles de l'hydrure et du deuterure de palladium, mesurees a l'aide d'essais de traction in situ. En seconde partie, la caracterisation du vieillissement a ete entreprise, focalisee sur des observations de bulles dans le tritiure de palladium par microscopie electronique en transmission, des mesures de pression a l'intErieur des bulles par resonance magnetique nucleaire et des mesures de gonflement macroscopique du materiau par pycnometrie. Ces travaux ont conduit a des avancees significatives quant a la comprehension du vieillissement et ont permis d'ameliorer considerablement sa modelisation

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

    Science.gov (United States)

    Vidal, Francisco V.; Welhan, John; Vidal, Victor M. V.

    1982-03-01

    Geothermal gases from submarine and subaerial hot springs in Ensenada, Baja California Norte, Mexico, were sampled for determination of gas chemistry and helium, nitrogen and stable carbon isotope composition. The submarine hot spring gas is primarily nitrogen (56.1% by volume) and methane (43.5% by volume), whereas nearby subaerial hot spring gases are predominantly nitrogen (95-99% by volume). The N 2/Ar ratios and σ 15N values of the subaerial hot spring gas indicate that it is atmospheric air, depleted in oxygen and enriched in helium. The submarine hot spring gas is most probably derived from marine sediments of Cretaceous age rich in organic matter. CH 4 is a major component of the gas mixture ( σ 13C = -44.05% 0), with only minor amounts of CO 2 ( σ13C= -10.46% 0). The σ 15N of N 2 is + 0.2% 0 with a very high N 2/Ar ratio of 160. The calculated isotopic equilibra tion temperature for CH 4CO 2 carbon exchange at depth in the Punta Banda submarine geothermal field is approximately 200°C in agreement with other geothermometry estimates. The 3He/ 4He ratios of the hot spring gases range from 0.3 to 0.6 times the atmospheric ratio, indicating that helium is predominantly derived from the radioactive decay of U and Th within the continental crust. Thus, not all submarine hydrothermal systems are effective vehicles for mantle degassing of primordial helium.

  3. Helium in atmospheres of binary stars

    Energy Technology Data Exchange (ETDEWEB)

    Leushin, V.V. (Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Fiziki)

    The helium abundances were obtained for 25 bright components of binary stars by model atmosphere analysis. The helium abundance for binary stars that lie on the main sequence are larger in the average than in single normal stars. The stars on the Hertzsppung - russel diagram lie at a larger distance from the zero age line than those with normal helium abundance.

  4. Helium resources of Mare Tranquillitatis

    Science.gov (United States)

    Cameron, Eugene N.

    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.

  5. Mesure et retroaction sur un qubit multi-niveaux en electrodynamique quantique en circuit non lineair

    Science.gov (United States)

    Boissonneault, Maxime

    L'electrodynamique quantique en circuit est une architecture prometteuse pour le calcul quantique ainsi que pour etudier l'optique quantique. Dans cette architecture, on couple un ou plusieurs qubits supraconducteurs jouant le role d'atomes a un ou plusieurs resonateurs jouant le role de cavites optiques. Dans cette these, j'etudie l'interaction entre un seul qubit supraconducteur et un seul resonateur, en permettant cependant au qubit d'avoir plus de deux niveaux et au resonateur d'avoir une non-linearite Kerr. Je m'interesse particulierement a la lecture de l'etat du qubit et a son amelioration, a la retroaction du processus de mesure sur le qubit de meme qu'a l'etude des proprietes quantiques du resonateur a l'aide du qubit. J'utilise pour ce faire un modele analytique reduit que je developpe a partir de la description complete du systeme en utilisant principalement des transfprmations unitaires et une elimination adiabatique. J'utilise aussi une librairie de calcul numerique maison permettant de simuler efficacement l'evolution du systeme complet. Je compare les predictions du modele analytique reduit et les resultats de simulations numeriques a des resultats experimentaux obtenus par l'equipe de quantronique du CEASaclay. Ces resultats sont ceux d'une spectroscopie d'un qubit supraconducteur couple a un resonateur non lineaire excite. Dans un regime de faible puissance de spectroscopie le modele reduit predit correctement la position et la largeur de la raie. La position de la raie subit les decalages de Lamb et de Stark, et sa largeur est dominee par un dephasage induit par le processus de mesure. Je montre que, pour les parametres typiques de l'electrodynamique quantique en circuit, un accord quantitatif requiert un modele en reponse non lineaire du champ intra-resonateur, tel que celui developpe. Dans un regime de forte puissance de spectroscopie, des bandes laterales apparaissent et sont causees par les fluctuations quantiques du champ electromagnetique

  6. 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)

  7. Abundance analyses of helium-rich subluminous B stars

    CERN Document Server

    N, Naslim; Ahmad, A; Behara, N T; Sahin, T

    2010-01-01

    The connection between helium-rich hot subdwarfs of spectral types O and B (He-sdB) has been relatively unexplored since the latter were found in significant numbers in the 1980's. In order to explore this connection further, we have analysed the surface composition of six He-sdB stars, including LB 1766, LB 3229, SB 21 (= Ton-S 137 = BPS 29503-0009), BPS 22940-0009, BPS 29496-0010, and BPS 22956-0094. Opacity-sampled line-blanketed model atmospheres have been used to derive atmospheric properties and elemental abundances. All the stars are moderately metal-poor compared with the Sun ([Fe/H] ~ -0.5). Four stars are nitrogen-rich, two of these are carbon-rich, and at least four appear to be neon-rich. The data are insufficient to rule out binarity in any of the sample. The surface composition and locus of the N-rich He-sdBs are currently best explained by the merger of two helium white dwarfs, or possibly by the merger of a helium white dwarf with a post-sdB white dwarf. C-rich He-sdBs require further investig...

  8. Precision spectroscopy of the helium atom

    Institute of Scientific and Technical Information of China (English)

    Shui-ming HU; Zheng-Tian LU; Zong-Chao YAN

    2009-01-01

    Persistent efforts in both theory and experiment have yielded increasingly precise understanding of the helium atom. Because of its simplicity, the helium atom has long been a testing ground for relativistic and quantum electrodynamic effects in few-body atomic systems theoretically and experimentally.Comparison between theory and experiment of the helium spectroscopy in ls2p3pJ can potentially extract a very precise value of the fine structure constant a. The helium atom can also be used to explore exotic nuclear structures. In this paper, we provide a brief review of the recent advances in precision calculations and measurements of the helium atom.

  9. Dispositif de mesure calorimétrique des pertes dans les condensateurs de puissance

    Science.gov (United States)

    Seguin, B.; Gosse, J. P.

    1997-02-01

    A calorimetric technique is used to measure the power losses in capacitors. The power dissipated in the component is measured as the difference between the heat powers delivered by a temperature regulation when the capacitor is energetized or not. The original feature of the apparatus lies in the use of the isothermal calorimetry and in the measurement of an electrical power, in condradistinction with previous and dissatisfacting attempts based on the measurement of a temperature increase. The result is an improvement of the accuracy and sensibility of the apparatus which can be used to determine the equivalent series resistance of capacitors having very low losses. Measurements realized on a polypropylene capacitor and a sinusoidal applied voltage have allowed us to separate the ohmic losses from the dielectric ones and to study their variations with temperature. Une technique de calorimétrie isotherme est appliquée à la mesure des pertes électriques dans les condensateurs. La puissance calorifique dissipée par le composant est mesurée comme la différence des puissances de chauffe délivrées par une régulation de température quand le condensateur est hors tension ou sous tension. L'originalité du dispositif réside dans l'utilisation du principe de calorimétrie isotherme et dans la nature de la grandeur physique mesurée qui est une puissance électrique alors que les tentatives antérieures de mesures calorimétriques reposaient sur la mesure d'une élévation de température. Il en résulte une amélioration de la précision et de la sensibilité de ce type d'appareillage qui peut être employé pour caractériser la résistance série équivalente des condensateurs à très faibles pertes. Une série de mesures, réalisée sur un condensateur au polypropylène soumis à une tension sinusoïdale, a permis de séparer les pertes ohmiques des pertes diélectriques et d'étudier leurs variations avec la température.

  10. Une methode simple pour la mesure de l'evapotranspiration reelle a l'echelle de la parcelle

    OpenAIRE

    1981-01-01

    Après avoir passé en revue les différentes méthodes de mesure de l’évapotranspiration réelle, qu’il s’agisse des méthodes directes telles que la pesée ou la mesure du stock en eau du sol ou des méthodes indirectes telles que la méthode du rapport de Bowen et la méthode aérodynamique combinée, on développe une méthode de mesure simple cherchant à allier les avantages de la méthode du rapport de Bowen (deux niveaux de mesure dans l’air seulement) et ceux de la méthode aérodynamique combinée...

  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 Language: Bilingual English...

  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 ...

  13. Souci du social et action publique sur mesure

    Directory of Open Access Journals (Sweden)

    Bertrand Ravon

    2008-10-01

    Full Text Available L’engagement dans la lutte contre les problèmes sociaux s’est transformé. Avec l’individualisation et la territorialisation du traitement public des problèmes sociaux, se pose de plus en plus nettement la question d’une action publique de proximité, intersubjective. Mais plutôt que de renvoyer immédiatement les raisons de cette action publique sur mesure à une critique de la psychologisation des rapports sociaux ou du déclin des institutions, il s’agit de l’analyser comme une expérience publique, avec son lot d’actions et d’affects, de convictions et d’inquiétudes, de ressources et de préoccupations. La notion de souci s’impose alors pour tenir ce double mouvement de l’engagement, entre agir et subir, des épreuves qui nous conduisent dans l’action aux attentes qui nous y maintiennent. À partir de plusieurs exemples de formation de problèmes sociaux, l’article décline alors le souci des acteurs dans deux directions. D’une part, le souci de soi est analysé comme un engagement public au sens d’un travail d’orientation de soi dans un monde incertain via la reprise d’expériences sociales négatives. D’autre part, le souci commun est envisagé comme une « communauté de charge », c’est-à-dire comme un collectif d’action publique fondé non pas à partir de propriétés communes mais à partir d’affects partagés.“Concern” in the social sphere and public action adapted to the client: singular and critical public experience of social problemsCommitment in the struggle against social problems has changed. Along with the individualisation and territorial decentralisation of the public treatment of social problems, the question of very local and intersubjective public action has come more and more into focus. But rather than immediately relegating the reasons for this tailor-made version of social action to a critique of the increasing influence of psychological methods in social relations

  14. Hot Money,Hot Problems

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    After emerging from the economic doldrums, developing economies are now confronted with a new danger-a flood of international hot money. But how has the speculative capital circumvented regulatory controls and what are the consequences concerning the stability of the developing world? Zhao Zhongwei, a senior researcher with the Institute of World Politics and Economics at the Chinese Academy of Social Sciences, discussed these issues in an article recently published in the China Securities Journal. Edited excerpts follow

  15. Interaction of Helium Rydberg State Molecules with Dense Helium.

    Science.gov (United States)

    Bonifaci, Nelly; Li, Zhiling; Eloranta, Jussi; Fiedler, Steven L

    2016-11-17

    The interaction potentials of the He2(*) excimer, in the a(3)Σu, b(3)Πg, c(3)Σg, and d(3)Σu electronic states with a ground state helium atom are presented. The symmetry of the interaction potentials closely follows the excimer Rydberg electron density with pronounced short-range minima appearing along the nodal planes of the Rydberg orbital. In such cases, a combination of the electrostatic short-range attraction combined with Pauli repulsion leads to the appearance of unusual long-range maxima in the potentials. Bosonic density functional calculations show that the (3)d state excimer resides in a localized solvation bubble in dense helium at 4.5 K, with radii varying from 12.7 Å at 0.1 MPa to 10.8 Å at 2.4 MPa. The calculated (3)d → (3)b pressure-induced fluorescence band shifts are in good agreement with experimental results determined by application of corona discharge. The magnitude of the spectral shifts indicate that the observed He2(*) molecules emit from dense helium whereas the corresponding fluorescence signal from the discharge zone appears quenched. This implies that fluorescence spectroscopy involving this electronic transition can only be used to probe the state of the surrounding medium rather than the discharge zone itself.

  16. Are 'hot spots' hot spots?

    Science.gov (United States)

    Foulger, Gillian R.

    2012-07-01

    The term 'hot spot' emerged in the 1960s from speculations that Hawaii might have its origins in an unusually hot source region in the mantle. It subsequently became widely used to refer to volcanic regions considered to be anomalous in the then-new plate tectonic paradigm. It carried with it the implication that volcanism (a) is emplaced by a single, spatially restricted, mongenetic melt-delivery system, assumed to be a mantle plume, and (b) that the source is unusually hot. This model has tended to be assumed a priori to be correct. Nevertheless, there are many geological ways of testing it, and a great deal of work has recently been done to do so. Two fundamental problems challenge this work. First is the difficulty of deciding a 'normal' mantle temperature against which to compare estimates. This is usually taken to be the source temperature of mid-ocean ridge basalts (MORBs). However, Earth's surface conduction layer is ˜200 km thick, and such a norm is not appropriate if the lavas under investigation formed deeper than the 40-50 km source depth of MORB. Second, methods for estimating temperature suffer from ambiguity of interpretation with composition and partial melt, controversy regarding how they should be applied, lack of repeatability between studies using the same data, and insufficient precision to detect the 200-300 °C temperature variations postulated. Available methods include multiple seismological and petrological approaches, modelling bathymetry and topography, and measuring heat flow. Investigations have been carried out in many areas postulated to represent either (hot) plume heads or (hotter) tails. These include sections of the mid-ocean spreading ridge postulated to include ridge-centred plumes, the North Atlantic Igneous Province, Iceland, Hawaii, oceanic plateaus, and high-standing continental areas such as the Hoggar swell. Most volcanic regions that may reasonably be considered anomalous in the simple plate-tectonic paradigm have been

  17. Comment mesurer correctement la PA chez les patients hémodialysés?

    OpenAIRE

    VANDERWECKENE, Pauline; Saint-Remy, Annie; Krzesinski, Jean-Marie

    2016-01-01

    Objectifs : Le contrôle de la pression artérielle (PA) chez le patient hémodialysé (HD) est un enjeu majeur en raison des résultats controversés sur les risques cardiovasculaires qui y sont associés. Cependant, la mesure de la PA dans cette population est difficile à appréhender au vu de sa grande variabilité. L’exactitude des mesures péridialytiques (enregistrées dans l’unité d’HD pendant la séance) est souvent remise en question. L’objectif de notre étude est d’établir la contribution et l...

  18. La mesure de la pression artérielle : écueils et chausse-trapes

    OpenAIRE

    Rorive, Georges; Dubois, Bernard; Saint-Remy, Annie

    2002-01-01

    La mesure de la pression artérielle est probablement l'acte médical le plus souvent réalisé et certainement un des moins fiables. L'introduction de la mesure ambulatoire de la pression artérielle a permis d'identifier l'importance de l'effet consultatio et, par là, de définir l'hypertension de "la blouse blanche". Celle-ci se définit comme une pression artérielle pathologique à la consultation et strictement normale en dehors. Si on la définit de cette manière, cette pathologie ne s'accompagn...

  19. Characterization of a hot-film probe for hypersonic flow

    Science.gov (United States)

    Sheplak, M.; Spina, E.; Mcginley, C.

    1995-01-01

    The critical issues concerning the application of constant-temperature hot-film anemometry to hypersonic flow are reviewed and extended. Mass-flux static calibrations were conducted in a Mach 10 helium flow, while mass-flux and total-temperature static calibrations were made in a Mach 6 air flow. In addition, comparative hot-film/hot-wire turbulence measurements were made in a Mach 11 helium boundary layer to provide insight into the dynamic response of the hot film. The measurements indicate that substrate conduction 'losses' dominate the static response of the hot-film probe, thus resulting in poor sensitivity to mass-flux and total temperature. Furthermore, it has been found that it is not possible to isolate mass-flux fluctuations at high overheat ratios for the current hot-film design. Thus, the sapphire-substrate hot-film anemometer is a robust, high-bandwidth instrument limited to qualitative transition and turbulence measurements. Finally, the extension of this technique to providing quantitative information is dependent upon the development of lower thermal-conductivity substrate materials.

  20. 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.

  1. 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.

  2. Experimental studies of antiprotonic helium

    CERN Document Server

    Widmann, E

    1998-01-01

    This talk describes the experimental studies of metastable antiprotonic helium "atomcules" pHe/sup +/ (a neutral exotic atom consisting of a helium nucleus, an antiproton and an electron) performed at CERN-LEAR, and future plans for experiments at the forthcoming Antiproton Decelerator (AD) at CERN. Laser spectroscopy experiments are reviewed which led to the observation of a total of 13 resonant transitions of the antiproton in both p/sup 4/He/sup +/ and p/sup 3/He/sup +/, and revealed a hyperfine splitting in one transition. A level of precision has been reached where the most accurate 3-body calculations need to include QED effects like the Lamb-shift to come close to the experimental results. (52 refs).

  3. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-04-15

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

  4. Elusive structure of helium trimers

    CERN Document Server

    Stipanović, Petar; Boronat, Jordi

    2016-01-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the po...

  5. Mesures magnétiques du dipôle BHN 45 pour le projet AD

    CERN Document Server

    Cornuet, D; CERN. Geneva. SPS and LEP Division

    1999-01-01

    La machine AC (Antiproton Collector) transformée en machine de décélérationd'antiprotons est appelée AD (Antiproton Decelerator). Pour vérifierle comportement de la machine à basse énergie et pendant la décélération, des mesures magnétiques ont été entreprises sur l'un des dipôles, le BHN 45.

  6. Heat transfer enhancement on thin wires in superfluid helium forced flows

    CERN Document Server

    Duri, Davide; Moro, Jean-Paul; Roche, Philippe-Emmanuel; Diribarne, Pantxo

    2014-01-01

    In this paper, we report the first evidence of an enhancement of the heat transfer from a heated wire by an external turbulent flow of superfluid helium. We used a standard Pt-Rh hot-wire anemometer and overheat it up to 21 K in a pressurized liquid helium turbulent round jet at temperatures between 1.9 K and 2.12 K. The null-velocity response of the sensor can be satisfactorily modeled by the counter flow mechanism while the extra cooling produced by the forced convection is found to scale similarly as the corresponding extra cooling in classical fluids. We propose a preliminary analysis of the response of the sensor and show that -contrary to a common assumption- such sensor can be used to probe local velocity in turbulent superfluid helium.

  7. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-01-01

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  8. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-12-31

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  9. Hot-wire anemometry for superfluid turbulent coflows

    OpenAIRE

    Durì, Davide; Baudet, Christophe; Moro, Jean-Paul; Roche, Philippe-Emmanuel; Diribarne, Pantxo

    2015-01-01

    International audience; We report the first evidence of an enhancement of the heat transfer from a heated wire to an external turbulent coflow of superfluid helium. We used a standard Pt-Rh hot-wire anemometer and overheat it up to 21 K in a pressurized liquid helium turbulent round jet at temperatures between 1.9 K and 2.12 K. The null-velocity response of the sensor can be satisfactorily modeled by the counterflow mechanism, while the extra cooling produced by the forced convection is found...

  10. Investigations of levitated helium drops

    Science.gov (United States)

    Whitaker, Dwight Lawrence

    1999-11-01

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

  11. Charging dynamics of dopants in helium nanoplasmas

    DEFF Research Database (Denmark)

    Heidenreich, Andreas; Grüner, Barbara; Schomas, Dominik

    2017-01-01

    We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared laser pulses (≤1015 W cm−2). In particular, we elucidate the interplay of dopant ionization inducing the ignition...... of a helium nanoplasma, and the charging of the dopant atoms driven by the ionized helium host. Most efficient nanoplasma ignition and charging is found when doping helium droplets with xenon atoms, in which case high charge states of both helium (He2+) and of xenon (Xe21+) are detected. In contrast, only low...... charge states of helium and dopants are measured when doping with potassium and calcium atoms. Classical molecular dynamics simulations which include focal averaging generally reproduce the experimental results and provide detailed insights into the correlated charging dynamics of guest and host clusters....

  12. Critical Landau velocity in helium nanodroplets.

    Science.gov (United States)

    Brauer, Nils B; Smolarek, Szymon; Loginov, Evgeniy; Mateo, David; Hernando, Alberto; Pi, Marti; Barranco, Manuel; Buma, Wybren J; Drabbels, Marcel

    2013-10-11

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecules embedded in helium nanodroplets of various sizes are accelerated out of the droplets by means of optical excitation, and the speed distributions of the ejected particles are determined. The measurements reveal the existence of a critical velocity in these systems, even for nanodroplets consisting of only a thousand helium atoms. Accompanying theoretical simulations based on a time-dependent density functional description of the helium confirm and further elucidate this experimental finding.

  13. Behaviour of helium after implantation in molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Viaud, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France)], E-mail: viaud@dircad.cea.fr; Maillard, S.; Carlot, G.; Valot, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France); Gilabert, E. [Chimie Nucleaire Analytique and Bio-environnementale (CNAB), Gradignan (France); Sauvage, T. [CEMHTI-CNRS, Orleans (France); Peaucelle, C.; Moncoffre, N. [Institut de Physique Nucleaire de Lyon (IPNL), Lyon (France)

    2009-03-31

    This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.

  14. Measurement of 2 characteristics of metastable helium important for laser cooling: loss rates due to collisions in presence of quasi-resonant laser radiation and transition rates for 2 forbidden transitions: 2{sup 3}P{sub 1} {yields} 1{sup 1}S{sub 0} and 2{sup 3}P{sub 2} {yields} 1{sup 1}S{sub 0}; Mesure de deux caracteristiques de l'helium metastable importantes pour le refroidissement radiatif: taux de pertes par collisions en presence de lumiere quasi-resonante et taux de transition des raies interdites 2{sup 3}P{sub 1} {yields} 1{sup 1}S{sub 0} et 2{sup 3}P{sub 2} {yields} 1{sup 1}S{sub 0}

    Energy Technology Data Exchange (ETDEWEB)

    Poupard, J

    2000-11-15

    This thesis presents the study of 2 characteristics of metastable helium that are important for laser cooling. First, we measure two-body losses in a magneto-optical trap. The losses, enhanced by nearly resonant laser radiation, are mainly due to ionizing collisions. We measure the loss rate by observing the decay of the number of trapped atoms using either atomic fluorescence or ion production. We study the loss rate as a function of the trapping laser parameters. The second part of the thesis concerns experiments to measure the transition rates of the intercombination lines: 2{sup 3}P{sub 1} to 1{sup 1}S{sub 0} and 2{sup 3}P{sub 2} to 1{sup 1}S{sub 0}. The first of these rates is measured by exciting a small fraction of the atoms in a magneto-optical trap to the 2{sup 3}P{sub 1} state and observing the decrease in the trap lifetime. We then measure the ratio of the transition rates for 2{sup 3}P{sub 1} and 2{sup 3}P{sub 2} towards the 1{sup 1}S{sub 0} ground state by monitoring the flux of UV photons associated with the transition. (author)

  15. GALEX J184559.8-413827: a new extreme helium star identified using SALT★

    Science.gov (United States)

    Jeffery, C. Simon

    2017-09-01

    A high-resolution spectrum of the helium-rich 'hot subdwarf' GALEX J184559.8-413827 (J1845-4138) obtained with SALT HRS demonstrates it to be the first extreme helium (EHe) star to be discovered in nearly 40 years. A quantitative analysis demonstrates it to have an atmosphere described by Teff = 26 170 ± 750 K, log g/cm s-2 = 4.22 ± 0.10 and a surface chemistry characterized by CNO-processed helium, a 1 per cent contamination of hydrogen (by number) and a metallicity 0.4 dex subsolar. Its distance and position are consistent with membership of the Galactic bulge. Its sharp absorption lines place strong constraints on both the rotation and microturbulent velocities. Spectroscopically, J1845-4138 closely resembles the pulsating EHe star V652 Her, generally considered to be the product of a double helium white dwarf merger evolving to become a helium-rich sdO star.

  16. 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...

  17. 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.

  18. Helium II level measurement techniques

    Science.gov (United States)

    Celik, D.; Hilton, D. K.; Zhang, T.; Van Sciver, S. W.

    2001-05-01

    In this paper, a survey of cryogenic liquid level measurement techniques applicable to superfluid helium (He II) is given. The survey includes both continuous and discrete measurement techniques. A number of different probes and controlling circuits for this purpose have been described in the literature. They fall into one of the following categories: capacitive liquid level gauges, superconducting wire liquid level gauges, thermodynamic (heat transfer-based) liquid level gauges, resistive gauges, ultrasound and transmission line-based level detectors. The present paper reviews these techniques and their suitability for He II service. In addition to these methods, techniques for measuring the total liquid volume and mass gauging are also discussed.

  19. Aspirating probes for measurement of mean concentration and fluctuating quantities in supersonic air/helium shear layer

    OpenAIRE

    Ninnemann, Todd A.

    1990-01-01

    Two aspirating hot-film probes are developed to make measurements in supersonic air/helium shear layers. The first probe is designed to measure local mean gas composition and is referred to as the mean concentration probe. This probe consists of a constant temperature hot-film sensor operating in a channel with a choked exit. The flow over the hot-fifm is influenced only by total temperature, total pressure, and gas composition. The mean probe is easily calibrated and shows acc...

  20. Hot-wire anemometry for superfluid turbulent coflows.

    Science.gov (United States)

    Durì, Davide; Baudet, Christophe; Moro, Jean-Paul; Roche, Philippe-Emmanuel; Diribarne, Pantxo

    2015-02-01

    We report the first evidence of an enhancement of the heat transfer from a heated wire to an external turbulent coflow of superfluid helium. We used a standard Pt-Rh hot-wire anemometer and overheat it up to 21 K in a pressurized liquid helium turbulent round jet at temperatures between 1.9 K and 2.12 K. The null-velocity response of the sensor can be satisfactorily modeled by the counterflow mechanism, while the extra cooling produced by the forced convection is found to scale similarly as the corresponding extra cooling in classical fluids. We propose a preliminary analysis of the response of the sensor and show that-contrary to a common assumption-such sensor can be used to probe local velocity in turbulent superfluid helium.

  1. Hot-wire anemometry for superfluid turbulent coflows

    Science.gov (United States)

    Durı, Davide; Baudet, Christophe; Moro, Jean-Paul; Roche, Philippe-Emmanuel; Diribarne, Pantxo

    2015-02-01

    We report the first evidence of an enhancement of the heat transfer from a heated wire to an external turbulent coflow of superfluid helium. We used a standard Pt-Rh hot-wire anemometer and overheat it up to 21 K in a pressurized liquid helium turbulent round jet at temperatures between 1.9 K and 2.12 K. The null-velocity response of the sensor can be satisfactorily modeled by the counterflow mechanism, while the extra cooling produced by the forced convection is found to scale similarly as the corresponding extra cooling in classical fluids. We propose a preliminary analysis of the response of the sensor and show that—contrary to a common assumption—such sensor can be used to probe local velocity in turbulent superfluid helium.

  2. Really Hot Stars

    Science.gov (United States)

    2003-04-01

    -2 in the LMC. PR Photo 09c/03: Nebula near the hot binary star BAT99-49 in the LMC. PR Photo 09d/03: The N44C Nebula in the LMC. Four unique images of highly excited nebulae in the Magellanic Clouds ESO PR Photo 09a/03 ESO PR Photo 09a/03 [Preview - JPEG: 400 x 472 pix - 74k [Normal - JPEG: 800 x 943 pix - 720k] [Full-Res - JPEG: 1200 x 1414 pix - 1.2M] ESO PR Photo 09b/03 ESO PR Photo 09b/03 [Preview - JPEG: 400 x 466 pix - 70k [Normal - JPEG: 800 x 931 pix - 928k] [Full-Res - JPEG: 1200 x 1397 pix - 1.8M] ESO PR Photo 09c/03 ESO PR Photo 09c/03 [Preview - JPEG: 400 x 469 pix - 74k [Normal - JPEG: 800 x 937 pix - 1.1M] [Full-Res - JPEG: 1200 x 1405 pix - 2.2M] ESO PR Photo 09d/03 ESO PR Photo 09d/03 [Preview - JPEG: 400 x 473 pix - 28k [Normal - JPEG: 800 x 945 pix - 368k] [Full-Res - JPEG: 1200 x 1418 pix - 600k] Captions: PR Photo 09a/03 is a reproduction of a "near-true" three-colour composite image of the highly excited nebula around the hot double star AB7 in the Small Magellanic Cloud (SMC), obtained in January 2002 with the FORS1 multi-mode instrument at the 8.2-m VLT MELIPAL telescope at the Paranal Observatory (Chile). It is based on three exposures through narrow-band optical (interference) filters that isolate the light from specific atoms and ions. In this rendering, the blue colour represents the light from singly ionized Helium (He II; wavelength 468.6 nm; exposure time 30 min), green corresponds to doubly ionized oxygen ([O III]; 495.7 + 500.7 nm; 5 min) and red to hydrogen atoms (H; H-alpha line at 656.2 nm; 5 min). Of these three ions, He II is the tracer of high excitation, i.e. the bluest areas of the nebula are the hottest. The sky field measures 400 x 400 arcsec2; the original pixel size on the 2k x 2k CCD is 0.23 arcsec. North is up and east to the left. Before combination, the CCD frames were flat-fielded and cleaned of cosmic-rays. Moreover, the stars in the blue (He II) image were removed in order to provide a clearer view of the surrounding

  3. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  4. Radioactive ions and atoms in superfluid helium

    NARCIS (Netherlands)

    Dendooven, P.G.; Purushothaman, S.; Gloos, K.; Aysto, J.; Takahashi, N.; Huang, W.; Harissopulos, S; Demetriou, P; Julin, R

    2006-01-01

    We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve t

  5. Organ protection by the noble gas helium

    NARCIS (Netherlands)

    Smit, K.F.

    2017-01-01

    The aims of this thesis were to investigate whether helium induces preconditioning in humans, and to elucidate the mechanisms behind this possible protection. First, we collected data regarding organ protective effects of noble gases in general, and of helium in particular (chapters 1-3). In chapter

  6. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  7. 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).

  8. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  9. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  10. Paramagnetic Attraction of Impurity-Helium Solids

    Science.gov (United States)

    Bernard, E. P.; Boltnev, R. E.; Khmelenko, V. V.; Lee, D. M.

    2003-01-01

    Impurity-helium solids are formed when a mixture of impurity and helium gases enters a volume of superfluid helium. Typical choices of impurity gas are hydrogen deuteride, deuterium, nitrogen, neon and argon, or a mixture of these. These solids consist of individual impurity atoms and molecules as well as clusters of impurity atoms and molecules covered with layers of solidified helium. The clusters have an imperfect crystalline structure and diameters ranging up to 90 angstroms, depending somewhat on the choice of impurity. Immediately following formation the clusters aggregate into loosely connected porous solids that are submerged in and completely permeated by the liquid helium. Im-He solids are extremely effective at stabilizing high concentrations of free radicals, which can be introduced by applying a high power RF dis- charge to the impurity gas mixture just before it strikes the super fluid helium. Average concentrations of 10(exp 19) nitrogen atoms/cc and 5 x 10(exp 18) deuterium atoms/cc can be achieved this way. It shows a typical sample formed from a mixture of atomic and molecular hydrogen and deuterium. It shows typical sample formed from atomic and molecular nitrogen. Much of the stability of Im-He solids is attributed to their very large surface area to volume ratio and their permeation by super fluid helium. Heat resulting from a chance meeting and recombination of free radicals is quickly dissipated by the super fluid helium instead of thermally promoting the diffusion of other nearby free radicals.

  11. Elusive structure of helium trimers

    Science.gov (United States)

    Stipanović, Petar; Vranješ Markić, Leandra; Boronat, Jordi

    2016-09-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond the Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the potentials. We use diffusion Monte Carlo simulations at T = 0, which give within statistical noise exact results of the ground state properties. All models predict both trimers 4He3 and 4He{}2{}3He to be in a quantum halo state.

  12. Photochemistry inside superfluid helium nano droplets

    Energy Technology Data Exchange (ETDEWEB)

    Slenczka, Alkwin; Vdovin, Alexander; Dick, Bernhard [Inst. fuer Physikalische und Theoretische Chemie, Univ. Regensburg (Germany)

    2007-07-01

    Superfluid helium nano droplets serve as the most gentle cyrogenic matrix for creating isolated and cold molecules. High resolution electronic spectroscopy is sensitive for the investigation of the very weak perturbation of the helium droplet on the embedded molecule. Fluorescence excitation spectra, dispersed emission spectra and pump--probe-spectra show details of the salvation of molecules in helium droplets which were attributed to relaxation processes of the first solvation layer around the dopant. Photochemistry such as ESIPT, tautomerization by proton transfer and charge transfer are highly sensitive on intermolecular perturbations. We have studies such processes in superfluid helium droplets. The comparison with the respective gas phase experiments and quantum chemical calculations reveals further details on the photochemistry as well as on the perturbation by the superfluid helium droplet.

  13. Permeability of Hollow Microspherical Membranes to Helium

    Science.gov (United States)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  14. Gemini helium closed cycle cooling system

    Science.gov (United States)

    Lazo, Manuel; Galvez, Ramon; Rogers, Rolando; Solis, Hernan; Tapia, Eduardo; Maltes, Diego; Collins, Paul; White, John; Cavedoni, Chas; Yamasaki, Chris; Sheehan, Michael P.; Walls, Brian

    2008-07-01

    The Gemini Observatory presents the Helium Closed Cycle Cooling System that provides cooling capacity at cryogenic temperatures for instruments and detectors. It is implemented by running three independent helium closed cycle cooling circuits with several banks of compressors in parallel to continuously supply high purity helium gas to cryocoolers located about 100-120 meters apart. This poster describes how the system has been implemented, the required helium pressures and gas flow to reach cryogenic temperature, the performance it has achieved, the helium compressors and cryocoolers in use and the level of vibration the cryocoolers produce in the telescope environment. The poster also describes the new technology for cryocoolers that Gemini is considering in the development of new instruments.

  15. Formation of the helium EUV resonance lines

    CERN Document Server

    Golding, Thomas Peter; Carlsson, Mats

    2016-01-01

    Context: While classical models successfully reproduce intensities of many transition region lines, they predict helium EUV line intensities roughly an order of magnitude lower than the observed value. Aims: To determine the relevant formation mechanism(s) of the helium EUV resonance lines, capable of explaining the high intensities under quiet sun conditions. Methods: We synthesise and study the emergent spectra from a 3D radiation-magnetohydrodynamics simulation model. The effects of coronal illumination and non-equilibrium ionisation of hydrogen and helium are included self-consistently in the numerical simulation. Results: Radiative transfer calculations result in helium EUV line intensities that are an order of magnitude larger than the intensities calculated under the classical assumptions. The enhanced intensity of He I 584 is primarily caused by He II recombination cascades. The enhanced intensity of He II 304 and He II 256 is caused primarily by non-equilibrium helium ionisation. Conclusion: The anal...

  16. Global helium particle balance in LHD

    Energy Technology Data Exchange (ETDEWEB)

    Motojima, G., E-mail: motojima.gen@lhd.nifs.ac.jp [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Masuzaki, S.; Tokitani, M.; Kasahara, H.; Yoshimura, Y.; Kobayashi, M.; Sakamoto, R.; Morisaki, T.; Miyazawa, J.; Akiyama, T. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Ohno, N. [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan); Mutoh, T.; Yamada, H. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2015-08-15

    Global helium particle balance in long-pulse discharges is analyzed for the first time in the Large Helical Device (LHD) with the plasma-facing components of the first wall and the divertor tiles composed of stainless steel and carbon, respectively. During the 2-min discharge sustained by ion cyclotron resonance heating (ICRH) and electron cyclotron heating (ECH), helium is observed to be highly retained in the wall (regarded as both the first wall and the divertor tiles). Almost all (about 96%) puffed helium particles (1.3 × 10{sup 22} He) are absorbed in the wall near the end of the discharge. Even though a dynamic retention is eliminated, 56% is still absorbed. The analysis is also applied to longer pulse discharges over 40 min by ICRH and ECH, indicating that the helium wall retention is dynamically changed in time. At the initial phase of the discharge, a mechanism for adsorbing helium other than dynamical retention is invoked.

  17. Hot subdwarf formation: Confronting theory with observation

    Directory of Open Access Journals (Sweden)

    Geier S.

    2013-03-01

    Full Text Available The formation of hot subdwarf stars is still unclear. Both single-star and binary scenarios have been proposed to explain the properties of these evolved stars situated at the extreme blue end of the horizontal branch. The observational evidence gathered in the last decade, which revealed high fractions of binaries, shifted the focus from the single-star to the binary formation scenarios. Common envelope ejection, stable Roche lobe overflow and the merger of helium white dwarfs seemed to be sufficient to explain the formation of both the binary as well as the remaining single hot subdwarfs. However, most recent and rather unexpected observations challenge the standard binary evolution scenarios.

  18. LabINRS. Mesures en laboratoire du coefficient de frottement dynamique de revêtements de sol

    OpenAIRE

    Marchal, P.; Jacques, M.

    2014-01-01

    Le LabINRS est un banc d’essai de laboratoire destiné à mesurer le coefficient de frottement dynamique d’un revêtement de sol. Ce document décrit le protocole de mesures avec le LabINRS et les résultats de mesures effectuées sur un panel de quinze revêtements de sol de caractéristiques différentes (matériaux, états de surface) réalisées en présence de deux polluants (huile et solution d’eau). Le LabINRS présente une sensibilité élevée et une très bonne répétabilité. Ces résultats ont été comp...

  19. Réduction de bruit quantique spatiale et mesures de petits déplacements en optique

    Science.gov (United States)

    Treps, N.; Maître, A.; Fabre, C.; Andersen, U.; Buchler, B.; Lame, P. K.; Bachor, H. A.

    2002-06-01

    L'étude des images optiques au niveau quantique nécessite de prendre en compte la structure multimode transverse de la lumière. Dans le cas particulier d'une mesure de position d'un faisceau lumineux effectuée par un détecteur à deux zone, on montre qu'il est nécessaire, si on veut améliorer la précision des mesures en réduisant le bruit quantique de la lumière, d'utiliser deux modes transverses. Nous présentons la première réalisation expérimentale d'une réduction de bruit spatiale, ce qui nous permet ensuite d'effectuer des mesures de petits déplacements sous la limite quantique standard.

  20. La mesure en éducation, un outil au service du politique

    OpenAIRE

    Agulhon, Catherine

    2009-01-01

    La statistique scolaire prétend rendre compte des processus complexes qui travaillent les institutions. Les organismes internationaux incitent les États à produire ces éléments de mesure, de comparaison et de mise en concurrence des systèmes scolaires, plus encore ces quinze dernières années. Chaque État a cependant construit un système d’information qui correspond aux formes d’évaluation qu’il veut donner à son projet éducatif. En France, ce système centralisé et très productif vise le suivi...

  1. Quelle mesure des effets du travail sur la santé ?

    OpenAIRE

    Bercot, Régine

    2012-01-01

    Nous envisagerons la maladie comme un processus engagé en vue d'une adaptation à un nouvel équilibre et la santé, non comme une absence de maladie, mais comme un processus de construction du bien être engageant le cadre social et les individus. Nous interrogerons la question de la mesure de la santé au travail en nous centrant sur l'enquête Sumer. Le travail est potentiellement générateur de bien être et de souffrance. Après avoir rappelé les grandes lignes de construction de cette enquête no...

  2. 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)

  3. Laser-induced reconstruction of Ag clusters in helium droplets

    Science.gov (United States)

    Gomez, Luis F.; O'Connell, Sean M. O.; Jones, Curtis F.; Kwok, Justin; Vilesov, Andrey F.

    2016-09-01

    Silver clusters were assembled in helium droplets of different sizes ranging from 105 to 1010 atoms. The absorption of the clusters was studied upon laser irradiation at 355 nm and 532 nm, which is close to the plasmon resonance maximum in spherical Ag clusters and in the range of the absorption of the complex, branched Ag clusters, respectively. The absorption of the pulsed (7 ns) radiation at 532 nm shows some pronounced saturation effects, absent upon the continuous irradiation. This phenomenon has been discussed in terms of the melting of the complex Ag clusters at high laser fluence, resulting in a loss of the 532 nm absorption. Estimates of the heat transfer also indicate that a bubble may be formed around the hot cluster at high fluences, which may result in ejection of the cluster from the droplet, or disintegration of the droplet entirely.

  4. Helium and neon abundances and compositions in cometary matter.

    Science.gov (United States)

    Marty, Bernard; Palma, Russell L; Pepin, Robert O; Zimmermann, Laurent; Schlutter, Dennis J; Burnard, Peter G; Westphal, Andrew J; Snead, Christopher J; Bajt, Sasa; Becker, Richard H; Simones, Jacob E

    2008-01-04

    Materials trapped and preserved in comets date from the earliest history of the solar system. Particles captured by the Stardust spacecraft from comet 81P/Wild 2 are indisputable cometary matter available for laboratory study. Here we report measurements of noble gases in Stardust material. Neon isotope ratios are within the range observed in "phase Q," a ubiquitous, primitive organic carrier of noble gases in meteorites. Helium displays 3He/4He ratios twice those in phase Q and in Jupiter's atmosphere. Abundances per gram are surprisingly large, suggesting implantation by ion irradiation. The gases are probably carried in high-temperature igneous grains similar to particles found in other Stardust studies. Collectively, the evidence points to gas acquisition in a hot, high ion-flux nebular environment close to the young Sun.

  5. Properties of hot subdwarfs in the GALEX survey

    CERN Document Server

    Nemeth, Peter; Vennes, Stephane

    2012-01-01

    We have analyzed a sample of hot subdwarfs (sdB, sdO) selected from the GALEX ultraviolet sky survey. Applying a model atmosphere analysis we determined the temperature, surface gravity, and helium-to-hydrogen abundance ratio, and obtained preliminary constraints on the CNO abundance for a sample of 181 stars. Adopting colourimetric (ultraviolet-infrared) and quantitative spectral decomposition we also investigated the incidence of solar type or earlier (A, F, G) companions.

  6. Hot subluminous stars: Highlights from the MUCHFUSS and Kepler missions

    Directory of Open Access Journals (Sweden)

    Geier S.

    2013-03-01

    Full Text Available Research into hot subdwarf stars is progressing rapidly. We present recent important discoveries. First we review the knowledge about magnetic fields in hot subdwarfs and highlight the first detection of a highly-magnetic, helium-rich sdO star. We briefly summarize recent discoveries based on Kepler light curves and finally introduce the closest known sdB+WD binary discovered by the MUCHFUSS project and discuss its relevance as a progenitor of a double-detonation type Ia supernova.

  7. Hot wire/film behavior in low-temperature gases

    Science.gov (United States)

    Kwack, E. Y.; Shakkottai, P.; Luchik, T. S.; Aaron, K. M.; Fabris, G.; Back, L. H.

    1992-01-01

    Commercially available hot wires/films were used to measure the velocities of evaporated hydrogen or helium gas during cryogenic mixing experiments. Hot wires were found to be too delicate to use in this harsh environment. Hot films were rugged enough to use at cryogenic temperatures even though they failed after a number of thermal cycles. Since the hot films have small aspect ratios, 13.4 and 20, they are quite sensitive to the thermal loading, Tw/Tg, even with a correction for the conduction end loss. In general, although the increase of the Nusselt number with Reynolds number at low temperatures was similar to that at room temperature, there was also a pronounced variation with Tw/Tg over the large range of 1.2 to 12 investigated.

  8. Electric response in superfluid helium

    Science.gov (United States)

    Chagovets, Tymofiy V.

    2016-05-01

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

  9. 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...

  10. 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.

  11. Particle detection by evaporation from superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.H. (Department of Physics, Brown University, Providence, Rhode Island 02912 (United States))

    1992-04-20

    We report the first experiments in which 5-MeV alpha particles are detected via evaporation from a bath of superfluid helium. The {alpha} excites phonons and rotons in the liquid helium, and these excitations are sufficiently energetic to evaporate helium atoms when they reach the free surface of the liquid. The approximate overall efficiency of this process has been determined, and we compare this with expectations. We have also been able to detect evaporation induced by a flux of {gamma}'s from a {sup 137}Cs source.

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

    Science.gov (United States)

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

    2008-03-01

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

  13. ASACUSA Anti-protonic Helium_Final

    CERN Multimedia

    CERN Audiovisual Production Service; CERN AD; Paola Catapano; Julien Ordan, Arzur Catel; Paola Catapano; ASACUSA COLLABORATION

    2016-01-01

    Latest precision measurement of the mass of the proton and the anti proton though the production of antiprotonic helium by the ASACUSA experiment at CERN's antimatter factory, with a beam from the Antiproton Decelerator

  14. Charged Condensate and Helium Dwarf Stars

    CERN Document Server

    Gabadadze, Gregory

    2008-01-01

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

  15. Charging dynamics of dopants in helium nanoplasmas

    OpenAIRE

    Heidenreich, Andreas; Grüner, Barbara; Schomas, Dominik; Stienkemeier, Frank; Krishnan, Siva Rama; Mudrich, Marcel

    2016-01-01

    We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared (NIR) laser pulses (

  16. Helium-Hydrogen Recovery System Project

    Data.gov (United States)

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

  17. 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.

  18. Helium liquefier cycles with saturated vapor compression

    Science.gov (United States)

    Minta, M.; Smith, J. L., Jr.

    The three refrigeration stages of the conventional helium liquefaction cycle are related to liquid nitrogen precooling, the use of expansion engines, and a J-T expansion. For an operation of helium refrigerators at temperatures below 4.2 K reduced pressure levels are required. Such an operation makes it necessary to enhance the compressor size and the heat exchanger surface area. In the case of 1.8 K refrigerators, practical cycles with three pressure levels are employed. It is pointed out that the saturated-vapor-compression (SVC) helium cycle provides an alternative solution to these problems. The present investigation is concerned with the design study of a SVC helium liquifier operating at elevated pressures. The study was conducted to demonstrate the potential of the SVC cycle on the basis of a direct comparison with a conventional cycle using the same precooling expanders and a supercritical wet expander instead of a J-T valve.

  19. Helium behaviour in implanted boron carbide

    Directory of Open Access Journals (Sweden)

    Motte Vianney

    2015-01-01

    Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

  20. Multiple Population Theory: Extreme helium population problem

    OpenAIRE

    Yi, Sukyoung K.

    2009-01-01

    The spreads in chemical abundances inferred by recent precision observations suggest that some or possibly all globular clusters can no longer be considered as simple stellar populations. The most striking case is omega Cen in the sense that its bluest main-sequence despite its high metallicity demands an extreme helium abundance of Y > 0.4. I focus on this issue of "the extreme helium population problem" in this review.

  1. Cosmogenic helium in a terrestrial igneous rock

    Science.gov (United States)

    Kurz, M. D.

    1986-01-01

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

  2. Effects of helium impurities on superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Selle, J.E.

    1977-07-01

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

  3. Helium Reionization in From New Sightlines

    Science.gov (United States)

    Syphers, David

    2017-01-01

    A very small number of sightlines to z~3 quasars have been studied in detail to show the progress of helium reionization. Although studying the same sightlines with each new UV spectrograph lead to a better understanding of them, the sightline variance is very strong during this patchy and extended process. We discuss detailed R>10,000 COS data from new sightlines, and what they reveal about the progress and end of helium reionization.

  4. Developpement de mesures non destructives, par ondes ultrasonores, d'epaisseurs de fronts de solidification dans les reacteurs metallurgiques

    Science.gov (United States)

    Floquet, Jimmy

    Dans les cuves d'electrolyse d'aluminium, le milieu de reaction tres corrosif attaque les parois de la cuve, ce qui diminue leur duree de vie et augmente les couts de production. Le talus, qui se forme sous l'effet des pertes de chaleur qui maintiennent un equilibre thermique dans la cuve, sert de protection naturelle a la cuve. Son epaisseur doit etre controlee pour maximiser cet effet. Advenant la resorption non voulue de ce talus, les degats generes peuvent s'evaluer a plusieurs centaines de milliers de dollars par cuve. Aussi, l'objectif est de developper une mesure ultrasonore de l'epaisseur du talus, car elle serait non intrusive et non destructive. La precision attendue est de l'ordre du centimetre pour des mesures d'epaisseurs comprenant 2 materiaux, allant de 5 a 20 cm. Cette precision est le facteur cle permettant aux industriels de controler l'epaisseur du talus de maniere efficace (maximiser la protection des parois tout en maximisant l'efficacite energetique du procede), par l'ajout d'un flux thermique. Cependant, l'efficacite d'une mesure ultrasonore dans cet environnement hostile reste a demontrer. Les travaux preliminaires ont permis de selectionner un transducteur ultrasonore a contact ayant la capacite a resister aux conditions de mesure (hautes temperatures, materiaux non caracterises...). Differentes mesures a froid (traite par analyse temps-frequence) ont permis d'evaluer la vitesse de propagation des ondes dans le materiau de la cuve en graphite et de la cryolite, demontrant la possibilite d'extraire l'information pertinente d'epaisseur du talus in fine. Fort de cette phase de caracterisation des materiaux sur la reponse acoustique des materiaux, les travaux a venir ont ete realises sur un modele reduit de la cuve. Le montage experimental, un four evoluant a 1050 °C, instrumente d'une multitude de capteurs thermique, permettra une comparaison de la mesure intrusive LVDT a celle du transducteur, dans des conditions proches de la mesure

  5. Pyridine Aggregation in Helium Nanodroplets

    Science.gov (United States)

    Nieto, Pablo; Poerschke, Torsten; Habig, Daniel; Schwaab, Gerhard; Havenith, Martina

    2012-06-01

    Pyridine crystals show the unusual property of isotopic polymorphism. Experimentally it has been observed that deuterated pyridine crystals exist in two phases while non-deuterated pyridine does not show a phase transition. Therefore, although isotopic substitution is the smallest possible modification of a molecule it greatly affects the stability of pyridine crystals. A possible experimental approach in order to understand this striking effect might be the study of pyridine aggregation for small clusters. By embedding the clusters in helium nanodroplets the aggregates can be stabilized and studied by means of Infrared Depletion Spectroscopy. Pyridine oligomers were investigated in the C-H asymmetric vibration region (2980-3100 cm-1) using this experimental technique. The number of molecules for the clusters responsibles for each band were determined by means of pick-up curves as well as mass sensitive depletion spectra. Furthermore, the intensity dependence of the different bands on applying a dc electric field was studied. The assignment of the different structures for pyridine clusters on the basis of these measurements were also carried out. S. Crawford et al., Angew. Chem. Int. Ed., 48, 755 (2009).

  6. Photoionization rates for helium: update

    CERN Document Server

    Sokół, 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...

  7. 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.

  8. Mesure du rayonnement naturel pour la modélisation de la température des organes : application aux fruits

    OpenAIRE

    Marquier, André; Adam, Boris; Guilioni, Lydie; Saudreau, Marc; Chelle, Michaël; Sinoquet, Herve

    2009-01-01

    Cet article présente une expérimentation mise en place dans un projet innovant du département Environnement et agronomie (EA). Nous développons, plus particulièrement les principes de la mesure du rayonnement naturel à l’aide d’un bilanmètre de chez Kipp & Zonen : les capteurs qui le constituent, les grandeurs mesurées et les précautions à prendre lors de son utilisation notamment dans le domaine de l’infrarouge thermique. Ensuite nous montrons l’intérêt de telles mesures lors de la validatio...

  9. Lithium in halo stars - Constraining the effects of helium diffusion on globular cluster ages and cosmology

    Science.gov (United States)

    Deliyannis, Constantine P.; Demarque, Pierre

    1991-01-01

    Stellar evolutionary models with diffusion are used to show that observations of lithium in extreme halo stars provide crucial constraints on the magnitude of the effects of helium diffusion. The flatness of the observed Li-T(eff) relation severely constrains diffusion Li isochrones, which tend to curve downward toward higher T(eff). It is argued that Li observations at the hot edge of the plateau are particularly important in constraining the effects of helium diffusion; yet, they are currently few in number. It is proposed that additional observations are required there, as well as below 5500 K, to define more securely the morphology of the halo Li abundances. Implications for the primordial Li abundance are considered. It is suggested that a conservative upper limit to the initial Li abundance, due to diffusive effects alone, is 2.35.

  10. Power, power density and efficiency optimization for a closed cycle helium turbine nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Chen Lingen E-mail: lgchenna@public.wh.hb.cn; Zheng Junlin; Sun Fengrui; Wu Chih

    2003-09-01

    The performance of a closed cycle helium turbine nuclear power plant for submarine propulsion is optimized in this paper. The power output, power density (ratio of power output to maximum specific volume in the cycle) and thermal efficiency of the cycle are derived. The maximum power, power density and efficiency are obtained by searching for the optimum heat conductance distribution among the hot side heat exchanger (intermediate heat exchanger), cold side heat exchanger (precooler) and recuperator for fixed total heat exchanger inventory with respect to the corresponding optimization objectives. The optimum results are compared with those reported in recent references for the conceptual design of a closed cycle helium turbine nuclear power plant for submarine propulsion. The numerical example shows that the method herein is valid and effective.

  11. Mesure ambulatoire de la pression artérielle, son utilité en pratique quotidienne

    OpenAIRE

    Krzesinski, Jean-Marie

    1994-01-01

    Si la nécessité du traitement de l'hypertension artérielle est un fait accepté de façon universelle, la question à propos des niveaux de pression artérielle qui méritent une intervention reste débattue. Cette difficulté trouve son origine dans une telle variabilité de la pression artérielle que les mesures au cabinet de consultation représentent seulement une vue limitée de son réel profil sur 24 heures. Le développement d'enregistreurs portatifs de la pression artérielle par méthode non i...

  12. MESURE NON INVASIVE DU DÉBIT AORTIQUE PAR VOIE OESOPHAGIÈNNE

    OpenAIRE

    Lavandier, B.; Cathignol, D.; Muchada, R.; Fady, J.; Birer, A.

    1990-01-01

    Depuis plusieurs années nous avons montré la faisabilité et l'intérêt clinique de la débitmétrie aortique par voie oesophagienne. Une amélioration importante de cette méthode a été apportée par le développement d'un nouveau type de débitmètre associant un imageur T.M. et un vélocimètre Doppler à émission pulsée. Afin de pouvoir mesurer simultanément et de façon continue le diamètre de l'aorte et la vitesse du flux sanguin aussi bien chez l'adulte que chez l'enfant (à l'aide d'une sonde oesoph...

  13. Pas d'image fiable de notre atmosphère sans mesures depuis le sol !

    OpenAIRE

    Mazière, M.; De Backer, H.; Mahieu, Emmanuel; Vander Auwera, J.; Bader, Whitney; V. De Bock; Desmet, F.; Foldes, T; Gielen, C.; Hendrick, F.; Hermans, C.; B. Langerock; Lejeune, Bernard; Mangold, A.; Tudorie, M

    2014-01-01

    Nous sommes actuellement confrontés à une atmosphère en évolution : les concentrations de ce qu’on appelle les gaz à effet de serre augmentent, la quantité d’ozone stratosphérique diminue, en particulier au-dessus de l’Antarctique où elle forme chaque année un ‘trou’ dans la couche d’ozone, et l’air n’est pas tous les jours très sain... Comment pouvons-nous détecter et surveiller ces changements pour, si nécessaire, prendre des mesures pour tenter de les contrecarrer ?...

  14. Réseau de capteurs sans fils : Application à la mesure de vibrations

    OpenAIRE

    NGUYEN VAN PHU, C

    2006-01-01

    Les progrès des techniques électroniques rendent possible le concept de mise en réseau de capteurs intelligents sans fils. Sur cette base matérielle, se sont développées diverses plate formes sans fils dont le Mote est un exemple. La particularité du Mote est qu'il a servi de support au développement d'un système d'exploitation innovant pour réseaux de capteurs sans fils, TinyOS, qui depuis a été porté sur d'autres capteurs. Le Mote est présenté ainsi qu'une application de mesure sur un pont ...

  15. Effect of dislocations on helium retention in deformed pure iron

    Science.gov (United States)

    Gong, Y. H.; Cao, X. Z.; Jin, S. X.; Lu, E. Y.; Hu, Y. C.; Zhu, T.; Kuang, P.; Xu, Q.; Wang, B. Y.

    2016-12-01

    The effects of dislocations created by deformation on helium retention in pure iron, including the helium atoms diffusion along the dislocation line and desorption from dislocation trapping sites, were investigated. The dislocation defect was introduced in specimens by cold-rolling, and then 5 keV helium ions were implanted into the deformed specimens. Slow positron beam technology and thermal desorption spectroscopy were used to investigate the evolution of dislocation defects and the desorption behavior of helium atoms under influence of dislocation. The behaviors of S-E, W-E and S-W plots indicate clearly that lots of helium atoms remain in the deformed specimen and helium atoms combining with dislocation change the distribution of electron density. The helium desorption plot indicates that dislocation accelerates helium desorption at 293 K-600 K and facilitates helium dissociation from HenVm (n/m = 1.8) cluster.

  16. Capteurs monopodes pour mesures accélérométriques

    Science.gov (United States)

    Delaite, R.; Valentin, J.-P.

    1993-08-01

    A new design for accelerometric measurements sensors is described. It uses a plate vibrating in thickness shear mode, maintained by the means of a single holder located at the crystal edge. This mounting does cancel the mechanical and thermal stresses which generally modify the sensor output signal. So the ratio signal/noise of a thickness shear accelerometer is improved and the intrinsic sensitivity is multiplied by a factor 40, by comparison with the sensitivity of a thickness shear plate bonded by the means of two opposite holders. Un nouveau dispositif destiné aux mesures d'accélération est présenté. Il met en œuvre une lame vibrant en cisaillement d'épaisseur, fixée à sa structure de maintien par l'intermédiaire d'une unique liaison. Ce montage permet d'éliminer les contraintes mécaniques et thermiques qui perturbent habituellement le signal de mesure, et qui sont liées soit au montage des éléments du capteur, soit aux variations rapides de température qui interviennent lors de la mise en fonctionnement du capteur. Le rapport signal/bruit d'un accéléromètre à lame vibrant en cisaillement d'épaisseur s'en trouve amélioré et la sensibilité à l'accélération est multipliée par un facteur 40, comparée à celle d'un capteur qui serait constitué d'une lame vibrant en cisaillement d'épaisseur, fixée par deux liaisons diamétralement opposées.

  17. Solid helium, a superfluid?; L'helium solide, un superfluide?

    Energy Technology Data Exchange (ETDEWEB)

    Balibar, S. [Centre National de la Recherche Scientifique (CNRS), Lab. de Physique Statistique de l' Ecole Normale Superieure, 75 - Paris (France)

    2007-06-15

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

  18. Hydraulic testing of helium cooled irradiation rigs of the IFMIF High Flux Test Module

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Christine, E-mail: Christine.Klein@kit.edu [Karlsruhe Institute of Technology, INR, Eggenstein-Leopoldshafen (Germany); Arbeiter, Frederik; Jackowski, Thomas; Martin, Thomas; Schlindwein, Georg [Karlsruhe Institute of Technology, INR, Eggenstein-Leopoldshafen (Germany)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Uniform perfusion of the multiple parallel minichannels of the rig model B by helium gas, which is of importance to obtain uniform and predictable temperatures, could be verified by measuring the mean velocity profiles of the rectangular jets are measured using hot-wire anemometry. Black-Right-Pointing-Pointer The pressure drop in the test section with rig model B was measured and delivers data for the validation of computational fluid dynamics (CFD) modeling approach for application in the IFMIF High Flux Test Module. The pressure drop depends significantly on the pressure level; acceleration resulting from the volumetric expansion of helium gas has to be modeled carefully in simulations. Black-Right-Pointing-Pointer Measurements with strain gage show the pressure depending deformation of the compartment container without the rig. The results agree well with simulations and approximation calculations. - Abstract: The hydraulic testing of a single 1:1 irradiation rig inside a mock-up container is part of the validation activities which support the engineering design of the High Flux Test Module. Uniform perfusion of the multiple parallel minichannels of the irradiation rigs by helium gas is of importance to obtain uniform and predictable temperatures. To evaluate the uniform distribution to the different parallel minichannels, the mean velocity profiles of the rectangular jets are measured using hot-wire anemometry. The velocity profiles show a symmetric and constant distribution of the mass flow to the parallel minichannels. The pressure drop in the test section with one of the candidate rig shapes is measured. The pressure drop depends significantly on the entrance pressure level; acceleration resulting from the volumetric expansion of helium gas has to be taken into account in simulations. Measurements with strain gage show the pressure depending deformation of the compartment container without the rig. The results agree

  19. Hot-dome anemometry

    Science.gov (United States)

    Thompson, Brian E.

    1998-05-01

    Hot-dome anemometry obtains three components of flow velocity using an array of sensors, specifically five hot films in the present contribution, which are mounted around the hemispherical tip of a cylindrical support. Calibration for speed and angle resembles that of hot wires and split films except that the procedures accommodate heat transfer dominated by forced convection from the surface of a sphere rather than single or multiple cylinders. Measurements are obtained with hot domes, conventional hot wires, and impact probes in the wake of a wing to quantify measurement uncertainties.

  20. A helium-carbon correlation on the extreme horizontal branch in ω Centauri

    Energy Technology Data Exchange (ETDEWEB)

    Latour, M.; Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, Succ. Centre-Ville, C.P. 6128, Montréal, QC H3C 3J7 (Canada); Randall, S. K. [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Bono, G. [Istituto Nazionale de Astrofisica, Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monte Porzio Catone (Italy); Calamida, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-11-10

    Taking advantage of a recent FORS2/VLT spectroscopic sample of extreme horizontal branch (EHB) stars in ω Cen, we isolate 38 spectra well suited for detailed atmospheric studies and determine their fundamental parameters (T {sub eff}, log g, and log N(He)/N(H)) using NLTE, metal line-blanketed models. We find that our targets can be divided into three groups: 6 stars are hot (T {sub eff} ≳ 45,000 K) H-rich subdwarf O stars, 7 stars are typical H-rich sdB stars (T {sub eff} ≲ 35,000 K), and the remaining 25 targets at intermediate effective temperatures are He-rich (log N(He)/N(H) ≳ –1.0) subdwarfs. Surprisingly, and quite interestingly, these He-rich hot subdwarfs in ω Cen cluster in a narrow temperature range (∼35,000 K to ∼40,000 K). We additionally measure the atmospheric carbon abundance and find a most interesting positive correlation between the carbon and helium atmospheric abundances. This correlation certainly bears the signature of diffusion processes—most likely gravitational settling impeded by stellar winds or internal turbulence—but also constrains possible formation scenarios proposed for EHB stars in ω Cen. For the He-rich objects in particular, the clear link between helium and carbon enhancement points toward a late hot flasher evolutionary history.

  1. Torque and power characteristics of a helium charged Stirling engine with a lever controlled displacer driving mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Karabulut, H.; Cinar, C.; Oztuerk, E.; Yuecesu, H.S. [Department of Mechanical Technology, Faculty of Technical Education, Gazi University, 06500 Teknikokullar, Ankara (Turkey)

    2010-01-15

    This study presents test results of a Stirling engine with a lever controlled displacer driving mechanism. Tests were conducted with helium and the working fluid was charged into the engine block. The engine was loaded by means of a prony type micro dynamometer. The heat was supplied by a liquefied petroleum gas (LPG) burner. The engine started to run at 118 C hot end temperature and the systematic tests of the engine were conducted at 180 C, 220 C and 260 C hot end external surface temperatures. During the test, cold end temperature was kept at 27 C by means of water circulation. Variation of the shaft torque and power with respect to the charge pressure and hot end temperature were examined. The maximum torque and power were measured as 3.99 Nm and 183 W at 4 bars charge pressure and 260 C hot end temperature. Maximum power corresponded to 600 rpm speed. (author)

  2. Thermal Performance of the XRS Helium Insert

    Science.gov (United States)

    Breon, Susan R.; DiPirro, Michael J.; Tuttle, James G.; Shirron, Peter J.; Warner, Brent A.; Boyle, Robert F.; Canavan, Edgar R.

    1999-01-01

    The X-Ray Spectrometer (XRS) is an instrument on the Japanese Astro-E satellite, scheduled for launch early in the year 2000. The XRS Helium Insert comprises a superfluid helium cryostat, an Adiabatic Demagnetization Refrigerator (ADR), and the XRS calorimeters with their cold electronics. The calorimeters are capable of detecting X-rays over the energy range 0.1 to 10 keV with a resolution of 12 eV. The Helium Insert completed its performance and verification testing at Goddard in January 1999. It was shipped to Japan, where it has been integrated with the neon dewar built by Sumitomo Heavy Industries. The Helium Insert was given a challenging lifetime requirement of 2.0 years with a goal of 2.5 years. Based on the results of the thermal performance tests, the predicted on-orbit lifetime is 2.6 years with a margin of 30%. This is the result of both higher efficiency in the ADR cycle and the low temperature top-off, more than compensating for an increase in the parasitic heat load. This paper presents a summary of the key design features and the results of the thermal testing of the XRS Helium Insert.

  3. Helium release from radioisotope heat sources

    Energy Technology Data Exchange (ETDEWEB)

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

    1984-05-01

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

  4. Hydrodynamic simulations of the core helium flash

    CERN Document Server

    Mocak, M; Weiss, A; Kifonidis, K; 10.1017/S1743921308022813

    2009-01-01

    We describe and discuss hydrodynamic simulations of the core helium flash using an initial model of a 1.25 M_sol star with a metallicity of 0.02 near at its peak. Past research concerned with the dynamics of the core helium flash is inconclusive. Its results range from a confirmation of the standard picture, where the star remains in hydrostatic equilibrium during the flash (Deupree 1996), to a disruption or a significant mass loss of the star (Edwards 1969; Cole & Deupree 1980). However, the most recent multidimensional hydrodynamic study (Dearborn 2006) suggests a quiescent behavior of the core helium flash and seems to rule out an explosive scenario. Here we present partial results of a new comprehensive study of the core helium flash, which seem to confirm this qualitative behavior and give a better insight into operation of the convection zone powered by helium burning during the flash. The hydrodynamic evolution is followed on a computational grid in spherical coordinates using our new version of th...

  5. Comparaison instrumentale de la mesure des précipitations en climat méditerranéen semi-aride

    OpenAIRE

    Brunel, Jean-Pierre

    1986-01-01

    La pluie est un élément important du cycle de l'eau mesuré à l'aide d'appareils très divers. A partir des données d'une station agrométéorologique du Nord de la Tunisie (zone semi-aride), il est montré dans quelles proportions peuvent varier les précipitations mesurées par différents capteurs. L'influence du vent est mise en évidence dans l'écart observé entre pluie mesurée au sol et pluie mesurée au-dessus du sol. (Résumé d'auteur)

  6. Thermal hydraulic performance analysis of the printed circuit heat exchanger using a helium test facility and CFD simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Hun [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); No, Hee Cheon [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)], E-mail: hcno@kaist.ac.kr; Lee, Jeong Ik; Jeon, Byong Guk [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2009-11-15

    The thermal-hydraulic performance of the PCHE was investigated using the KAIST helium test loop. Experiments were performed in the helium laminar region with 350 < Re < 1200. The hot/cold side inlet conditions were 25-550 {sup o}C/25-100 {sup o}C over the operating pressure of 1.5-1.9 MPa, respectively. Mass flow rates were controlled in the range of 40-100 kg/h. Pressure drop and temperature difference were measured at the inlet and outlet of the hot and cold sides. A global Fanning factor correlation and a global Nusselt number correlation were proposed using information only at the inlet and outlet of the hot and cold sides. A three-dimensional (3-D) numerical simulation was performed using FLUENT, a commercial computational fluid dynamics (CFD) code, to compare simulation results to the KAIST helium test data and to obtain the local Nusselt number in the PCHE. CFD predictions showed good agreement with experimental data. A local pitch-averaged Nusselt number correlation was proposed using local temperature, pressure, surface heat fluxes, and properties provided by CFD simulations. The system analysis code, GAMMA, was also utilized to identify which correlation was more applicable for system analysis. It turns out that the proposed local pitch-averaged Nusselt number correlation from CFD simulations is more appropriate than the global Nusselt number correlation developed from experimental data.

  7. Variability in Hot Carbon-Dominated Atmosphere (hot DQ) White Dwarfs: Rapid Rotation?

    CERN Document Server

    Williams, Kurtis A; Winget, D E; Falcon, Ross E; Bierwagon, Michael

    2015-01-01

    Hot white dwarfs with carbon-dominated atmospheres (hot DQs) are a cryptic class of white dwarfs. In addition to their deficiency of hydrogen and helium, most of these stars are highly magnetic, and a large fraction vary in luminosity. This variability has been ascribed to nonradial pulsations, but increasing data call this explanation into question. We present studies of short-term variability in seven hot DQ white dwarfs. Three (SDSS J1426+5752, SDSS J2200-0741, and SDSS J2348-0942) were known to be variable. Their photometric modulations are coherent over at least two years, and we find no evidence for variability at frequencies that are not harmonics. We present the first time-series photometry for three additional hot DQs (SDSS J0236-0734, SDSS J1402+3818, and SDSS J1615+4543); none are observed to vary, but the signal-to-noise is low. Finally, we present high speed photometry for SDSS J0005-1002, known to exhibit a 2.1 d photometric variation; we do not observe any short-term variability. Monoperiodicit...

  8. 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

  9. Primary neutral helium in the heliosphere

    CERN Document Server

    Mueller, Hans-Reinhard

    2012-01-01

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

  10. The muonic helium lamb shift experiment

    Energy Technology Data Exchange (ETDEWEB)

    Goetzfried, Johannes; Krauth, Julian [Max-Planck-Institute of Quantum Optics, Garching (Germany); Collaboration: CREMA collaboration

    2014-07-01

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

  11. Helium corona-assisted air discharge

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Nan; Gao Lei; Ji Ailing; Cao Zexian [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-15

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

  12. Superfluid helium-4 in one dimensional channel

    Science.gov (United States)

    Kim, Duk Y.; Banavar, Samhita; Chan, Moses H. W.; Hayes, John; Sazio, Pier

    2013-03-01

    Superfluidity, as superconductivity, cannot exist in a strict one-dimensional system. However, the experiments employing porous media showed that superfluid helium can flow through the pores of nanometer size. Here we report a study of the flow of liquid helium through a single hollow glass fiber of 4 cm in length with an open id of 150 nm between 1.6 and 2.3 K. We found the superfluid transition temperature was suppressed in the hollow cylinder and that there is no flow above the transition. Critical velocity at temperature below the transition temperature was determined. Our results bear some similarity to that found by Savard et. al. studying the flow of helium through a nanohole in a silicon nitrite membrane. Experimental study at Penn State is supported by NSF Grants No. DMR 1103159.

  13. 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.

  14. On Helium-Dominated Stellar Evolution: The Mysterious Role of the O(He)-Type Stars

    Science.gov (United States)

    Reindl, N.; Rauch, T.; Werner, K.; Kruk, J. W.; Todt, H.

    2014-01-01

    Context. About a quarter of all post-asymptotic giant branch (AGB) stars are hydrogen-deficient. Stellar evolutionary models explain the carbon-dominated H-deficient stars by a (very) late thermal pulse scenario where the hydrogen-rich envelope is mixed with the helium-rich intershell layer. Depending on the particular time at which the final flash occurs, the entire hydrogen envelope may be burned. In contrast, helium-dominated post-AGB stars and their evolution are not yet understood. Aims. A small group of very hot, helium-dominated stars is formed by O(He)-type stars. A precise analysis of their photospheric abundances will establish constraints to their evolution. Methods. We performed a detailed spectral analysis of ultraviolet and optical spectra of four O(He) stars by means of state-of-the-art non-LTE model-atmosphere techniques. Results. We determined effective temperatures, surface gravities, and the abundances of H, He, C, N, O, F, Ne, Si, P, S, Ar, and Fe. By deriving upper limits for the mass-loss rates of the O(He) stars, we found that they do not exhibit enhanced mass-loss. The comparison with evolutionary models shows that the status of the O(He) stars remains uncertain. Their abundances match predictions of a double helium white dwarf (WD) merger scenario, suggesting that they might be the progeny of the compact and of the luminous helium-rich sdO-type stars. The existence of planetary nebulae that do not show helium enrichment around every other O(He) star precludes a merger origin for these stars. These stars must have formed in a different way, for instance via enhanced mass-loss during their post-AGB evolution or a merger within a common-envelope (CE) of a CO-WD and a red giant or AGB star. Conclusions. A helium-dominated stellar evolutionary sequence exists that may be fed by different types of mergers or CE scenarios. It appears likely that all these pass through the O(He) phase just before they become WDs.

  15. Adsorption of Helium Atoms on Two-Dimensional Substrates

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

    Wang, Chao; Oviedo, Abner

    2012-06-01

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

  17. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Tie-Ying; LONG Xing-Gui; WANG Jun; HOU Qing; WU Zhong-Cheng; PENG Shu-Ming; LUO Shun-Zhong

    2008-01-01

    Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 300 K.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.

  18. Adsorption of Helium Atoms on Two-Dimensional Substrates

    Science.gov (United States)

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

    2016-12-01

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

  19. Intramolecular quantum chaos in doped helium nanodroplets

    Science.gov (United States)

    Polyakova, E.; Stolyarov, D.; Zhang, X.; Kresin, V. V.; Wittig, C.

    2003-07-01

    A mass spectrometric depletion spectrum (17 700-18 300 cm -1) is reported for NO 2 in superfluid (0.37 K) helium nanodroplets. Gas phase NO 2 is believed to be vibronically chaotic at these energies. Transitions are broadened and blue-shifted relative to their gas phase counterparts. The spectrum is fitted reasonably well by setting all of the widths and shifts equal to 7 cm -1. Modest dispersions (i.e., 90% lie within 2 cm -1 of the central values) are consistent with quantum chaos in NO 2. Relaxation is dominated by interactions of NO 2 with its non-superfluid helium nearest neighbors.

  20. O(^3 p) Doped Helium Droplets

    Science.gov (United States)

    Brice, Joseph T.; Douberly, Gary E.

    2017-06-01

    Atomic oxygen (^3 P) is generated via thermolysis in a commerical thermal gas cracker (Mantis Ltd. MGC-75). Complexes with HCN were investigated to qualitatively assess the doping efficiency of O(^3 P) into a helium droplet. Theoretical calculations of a linear O \\cdot\\cdot\\cdot HCN (^3 Σ) complex at the CCSD(T)/aug-cc-pVTZ level are consistent with the rotational constants extracted from the rotational substructure in the experimental spectra, and with dipole moments approximated from Stark spectra. The thermal source will be used to study reactions between O(^3 P) and hydrocarbons in helium droplets, and preliminary data on this topic will be presented.

  1. Trace Detection of Metastable Helium Molecules in Superfluid Helium by Laser-Induced Fluorescence

    CERN Document Server

    McKinsey, D N; Nikkel, J A; Rellergert, W

    2005-01-01

    We describe an approach to detecting ionizing radiation that combines the special properties of superfluid helium with the sensitivity of quantum optics techniques. Ionization in liquid helium results in the copious production of metastable helium molecules, which can be detected by laser-induced fluorescence. Each molecule can be probed many times using a cycling transition, resulting in the detection of individual molecules with high signal to noise. This technique could be used to detect neutrinos, weakly interacting massive particles, and ultracold neutrons, and to image superfluid flow in liquid He-4.

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

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.E.; Halley, J.W.; Hoon, S. [and others

    1995-04-01

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

  3. Les fondements de la mesure du temps comment les fréquences atomiques règlent le monde

    CERN Document Server

    Audoin, Claude

    1998-01-01

    La mesure du temps fondée sur des propriétés atomiques est née en 1955, avec le premier étalon de fréquence à jet de césium. Depuis, les horloges atomiques ne cessent de progresser et sont au coeur de nombreuses activités, telles que les comparaisons de temps, l'unification mondiale de l'heure ou la recherche en astronomie, géodésie, géophysique, télécommunications, etc. Cet ouvrage fournira des réponses détaillées au lecteur intéressé par la mesure du temps appliquée aux divers domaines cités.

  4. On the formation of hot DQ white dwarfs

    CERN Document Server

    Althaus, L G; Córsico, A H; Bertolami, M M Miller; Romero, A D

    2009-01-01

    We present the first full evolutionary calculations aimed at exploring the origin of hot DQ white dwarfs. These calculations consistently cover the whole evolution from the born-again stage to the white dwarf cooling track. Our calculations provide strong support to the diffusive/convective-mixing picture for the formation of hot DQs. We find that the hot DQ stage is a short-lived stage and that the range of effective temperatures where hot DQ stars are found can be accounted for by different masses of residual helium and/or different initial stellar masses. In the frame of this scenario, a correlation between the effective temperature and the surface carbon abundance in DQs should be expected, with the largest carbon abundances expected in the hottest DQs. From our calculations, we suggest that most of the hot DQs could be the cooler descendants of some PG1159 stars characterized by He-rich envelopes markedly smaller than those predicted by the standard theory of stellar evolution. At least for one hot DQ, t...

  5. A study of the hot local interstellar medium

    Science.gov (United States)

    McLean, Ryan

    2000-10-01

    Material synthesized in stellar furnaces and supernova explosions recycles through a hot phase of the interstellar medium (ISM) before it condenses into new stellar systems. I have studied the hot phase of the interstellar medium using ISM absorption line spectra of hot gas. O VI, N V and C IV each have resonance absorption lines at ultraviolet wavelength and are the most cosmically abundant elements other than hydrogen and helium. Two sounding rocket experiments built at the University of Colorado observed hot gas in the interstellar medium of galaxies. The Hot Carbon Oxygen Nitrogen Echelle Spectrograph ( HotCONES) made observations of O VI, N V and C IV in the local interstellar medium and the Wadsworth High-resolution Instrument (WHI) observed O VI in both the ISM of our galaxy and in the ISM of the Large Magellanic Cloud. I have discovered evidence for O VI components moving at speeds of up to 750 km s-1 along the line of sight. These high velocity components may be indicative of an extended supernova remnant.

  6. Absolute measurement of {beta} emitters with a 4 {pi} counter; Mesure absolue des emetteurs {beta} au compteur 4 {pi}

    Energy Technology Data Exchange (ETDEWEB)

    Le Gallic, Y. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1959-06-15

    The object of this work is to investigate the conditions under which the activity of {beta}-emitting radionuclides may be measured with a maximum of precision, and as a result to study the relevant corrections. The various problems relating to activity measurements with a 4 {pi} counter have been examined successively: - comparison of 4 {pi}, GM and proportional counters; - study of the preparation of sources; - corrections on the counting of sources; - self-absorption; - correction for absorption. The precision obtained on these measurements varies from 1.2 to 3 per cent, with the result that the 4 {pi} counter can be considered a very satisfactory calibration instrument. (author) [French] Le but de ce travail est de rechercher les conditions permettant d'obtenir avec le maximum de precision, la mesure de l'activite des radionuclides se desintegrant par emission et par consequent d'etudier les corrections qui s'y rapportent. Nous avons examine successivement les differents problemes se rapportant aux mesures d'activite au compteur 4 {pi}: - Comparaison des compteurs 4 {pi}, GM et proportionnel; - etude de la preparation des sources; - corrections sur la numeration des sources; - auto-absorption; - correction d'absorption. La precision obtenue dans ces mesures, variant de 1,2 a 3 pour cent, on peut donc considerer le compteur 4 {pi} comme un instrument d'etalonnage tres satisfaisant. (auteur)

  7. Interatomic Coulombic decay in helium nanodroplets

    DEFF Research Database (Denmark)

    Shcherbinin, Mykola; Laforge, Aaron; Sharma, Vandana

    2017-01-01

    Interatomic Coulombic decay (ICD) is induced in helium nanodroplets by photoexciting the n=2 excited state of He+ using XUV synchrotron radiation. By recording multiple-coincidence electron and ion images we find that ICD occurs in various locations at the droplet surface, inside the surface region...

  8. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to tr

  9. Messer to provide helium for LHC

    CERN Document Server

    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.

  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. Thermalization of magnetically trapped metastable helium

    CERN Document Server

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

    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.

  12. Critical Landau Velocity in Helium Nanodroplets

    NARCIS (Netherlands)

    N.B. Brauer; S. Smolarek; E. Loginov; D. Mateo; A. Hernando; M. Pi; M. Barranco; W.J. Buma; M. Drabbels

    2013-01-01

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitatio

  13. 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.…

  14. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to

  15. Photoassociation of cold metastable helium atoms

    NARCIS (Netherlands)

    Woestenenk, G.R.

    2001-01-01

    During the last decades the study of cold atoms has grown in a great measure. Research in this field has been made possible due to the development of laser cooling and trapping techniques. We use laser cooling to cool helium atoms down to a temperature of 1 mK and we are able to tr

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

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Kei, E-mail: kimamura@riken.jp [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Furukawa, Takeshi [Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Wakui, Takashi [Cyclotron and Radioisotope Center, Tohoku University, 6-3 Aoba, Aramaki, Aoba, Sendai, Miyagi 980-8578 (Japan); Yang, Xiaofei [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); School of Physics, Peking University, Chengfu Road, Haidian District, Beijing 100871 (China); Yamaguchi, Yasuhiro [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Tetsuka, Hiroki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Mitsuya, Yosuke [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Tsutsui, Yoshiki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Fujita, Tomomi [Department of Physics, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Ebara, Yuta; Hayasaka, Miki [Department of Physics, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501 (Japan); Arai, Shino; Muramoto, Sosuke [Department of Physics, Meiji University, 1-1-1 Higashi-Mita, Tama, Kawasaki, Kanagawa 214-8571 (Japan); Ichikawa, Yuichi [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Department of Physics, Tokyo Instutute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan); Ishibashi, Yoko [RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Department of Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); and others

    2013-12-15

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Claas, P.

    2006-01-15

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

  18. Helium accreting CO white dwarfs with rotation: helium novae instead of double detonation

    CERN Document Server

    Yoon, S C

    2004-01-01

    We present evolutionary models of helium accreting carbon-oxygen white dwarfs in which we include the effects of the spin-up of the accreting star induced by angular momentum accretion, rotationally induced chemical mixing and rotational energy dissipation. Initial masses of 0.6 Msun and 0.8 Msun and constant accretion rates of a few times 10^{-8} Msun/yr of helium rich matter have been considered, which is typical for the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. It is found that the helium envelope in an accreting white dwarf is heated efficiently by friction in the differentially rotating spun-up layers. As a result, helium ignites much earlier and under much less degenerate conditions compared to the corresponding non-rotating case. Consequently, a helium detonation may be avoided, which questions the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. We discuss implications of our results for the evolution of helium star plus white dwarf binary systems as possible...

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

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, D.; Slenczka, A., E-mail: alkwin.slenczka@chemie.uni-regensburg.de [Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93040 Regensburg (Germany)

    2015-01-07

    Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm{sup −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.

  20. Evaluation of helium cooling for fusion divertors

    Energy Technology Data Exchange (ETDEWEB)

    Baxi, C.B.

    1993-09-01

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

  1. Thermal Evolution of the Inhomogeneous Jovian Planets: The Effects of Helium Phase Separation

    Science.gov (United States)

    Mankovich, Christopher; Fortney, Jonathan; Moore, Kevin; Nettelmann, Nadine

    2014-11-01

    We compute evolutionary models of Jupiter and Saturn including the effects of helium phase separation in the deep interior. The aim is to simultaneously match each planet's present-day luminosity and surface helium abundance, which are at odds with homogeneous, adiabatic thermal evolution. The calculations are carried out using the open source MESA code, extended to include a modern phase diagram for hydrogen/helium mixtures at high pressures and a self-consistent radiative atmosphere grid for each planet. We find that if He redistribution proceeds much faster than a convective circulation time, then the composition gradient established between one and a few Mbar stabilizes the fluid against convection. In this region the heat is transported less efficiently by overstable double-diffusive convection, which we implement following recent 3D hydrodynamics simulations of the instability. The onset and evolution of this superadiabatic barrier region between the hot, He-rich inner adiabat and the cool, He-depleted outer adiabat bears directly on the cooling histories, especially that of Saturn. The upcoming measurement of Saturn's atmospheric He abundance expected of Cassini will place constraints on both the extent of the convectively stable region in Saturn and the general H/He phase diagram which informs the thermal evolution of all giant planets. We discuss implications for the dynamo within each planet, and ring seismology for Saturn.

  2. Gas turbine modular helium reactor in cogeneration; Turbina de gas reactor modular con helio en cogeneracion

    Energy Technology Data Exchange (ETDEWEB)

    Leon de los Santos, G. [UNAM, Facultad de Ingenieria, Division de Ingenieria Electrica, Departamento de Sistemas Energeticos, Ciudad Universitaria, 04510 Mexico, D. F. (Mexico)], e-mail: tesgleon@gmail.com

    2009-10-15

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

  3. Mesure de la concentration absolue de SiO parspectroscopie d'absorption UV

    Science.gov (United States)

    Coursimault, F.; Motret, O.; Viladrosa, R.; Pouvesle, J. M.

    2003-06-01

    Le but de cette étude est de développer un diagnostic de mesure de concentration de Si0 adapté à un procédé industriel de dépôt d'oxydes de silicium sur polymères par décharge a barrière diélectrique atmosphérique (DBD). Deux méthodes spectroscopiques basées sur des techniques d'absorption et d'auto-absorption ont été développées. La concentration de Si0 a été estimée par ajustement des spectres synthétiques calculés sur les spectres expérimentaux. Ces deux méthodes permettent de suivre l'évolution temporelle de Si0 durant les phases de décharge et de post-décharge.

  4. Molecular dynamics study of helium bubble pressure in titanium

    Institute of Scientific and Technical Information of China (English)

    Zhang Bao-Ling; Wang Jun; Hou Qing

    2011-01-01

    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.

  5. VARIABILITY IN HOT CARBON-DOMINATED ATMOSPHERE (HOT DQ) WHITE DWARFS: RAPID ROTATION?

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Kurtis A.; Bierwagen, Michael [Department of Physics and Astrophysics, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX, 75429 (United States); Montgomery, M. H.; Winget, D. E.; Falcon, Ross E., E-mail: Kurtis.Williams@tamuc.edu [Department of Astronomy, University of Texas, 1 University Station C1400, Austin, TX, 78712 (United States)

    2016-01-20

    Hot white dwarfs (WDs) with carbon-dominated atmospheres (hot DQs) are a cryptic class of WDs. In addition to their deficiency of hydrogen and helium, most of these stars are highly magnetic, and a large fraction vary in luminosity. This variability has been ascribed to nonradial pulsations, but increasing data call this explanation into question. We present studies of short-term variability in seven hot DQ WDs. Three (SDSS J1426+5752, SDSS J2200−0741, and SDSS J2348−0942) were known to be variable. Their photometric modulations are coherent over at least two years, and we find no evidence for variability at frequencies that are not harmonics. We present the first time-series photometry for three additional hot DQs (SDSS J0236−0734, SDSS J1402+3818, and SDSS J1615+4543); none are observed to vary, but the signal-to-noise is low. Finally, we present high speed photometry for SDSS J0005−1002, known to exhibit a 2.1-day photometric variation; we do not observe any short-term variability. Monoperiodicity is rare among pulsating WDs, so we contemplate whether the photometric variability is due to rotation rather than pulsations; similar hypotheses have been raised by other researchers. If the variability is due to rotation, then hot DQ WDs as a class contain many rapid rotators. Given the lack of companions to these stars, the origin of any fast rotation is unclear—both massive progenitor stars and double degenerate merger remnants are possibilities. We end with suggestions of future work that would best clarify the nature of these rare, intriguing objects.

  6. Mass-radius relations for helium white dwarfs

    CERN Document Server

    Civelek, R

    1998-01-01

    In recent years, white dwarf stars are receiving increasing attension. The recent studies on the relation of M-R for the WDs are those of Wood (1990), Vennes et al. (1995) and Althaus and Benvenuto (1997, 1998). Vennes et al. (1995) computed static M-R relation for masses between 0.4 $M_\\odot$ and 0.7 $M_\\odot$ assuming non zero temperature effects. They assumed the luminosity is proportional to the mass which works for cool WDs but their results are in the range of high effective temperatures. As Althaus and Benvenuto (1997) mentioned, luminosity is not proportional to a constant for hot WD interiors because of neutrino emission. The purpose of this study is to present the effect of neutrino emission at finite temperatures. We considered fully degenerate configuration for WDs with pure helium composition to obtain static mass-radius relation for masses greater than 0.4 $M_\\odot$ with luminosity mass ratio due to neutrino energy loss.

  7. Improved synthetic spectra of helium-core white dwarf stars

    CERN Document Server

    Rohrmann, R D; Althaus, L G; Benvenuto, O G

    2002-01-01

    We examine the emergent fluxes from helium-core white dwarfs following their evolution from the end of pre-white dwarf stages down to advanced cooling stages. For this purpose, we include a detailed treatment of the physics of the atmosphere, particularly an improved representation of the state of the gas by taking into account non-ideal effects according to the so-called occupation probability formalism. The present calculations also incorporate hydrogen line opacity from Lyman, Balmer and Paschen series, pseudo-continuum absorptions and new updated induced-dipole absorption from H$_2$-H$_2$, H$_2$-He and H-He pairs. We find that the non-ideal effects and line absorption alter the appearance of the stellar spectrum and have a significant influence upon the photometric colours in the UBVRI-JHKL system. This occurs specially for hot models $T_{\\rm eff}\\ga 8000$ due to line and pseudo-continuum opacities, and for cool models $T_{\\rm eff}\\la 4000$ where the perturbation of atoms and molecules by neighbour partic...

  8. Development and Dissemination of a Nationwide Helium Database for a National Assessment of Helium Resources.

    Science.gov (United States)

    Brennan, S. T.; East, J. A., II; Garrity, C. P.

    2015-12-01

    In 2013, Congress passed the Helium Stewardship Act requiring the U.S. Geological Survey (USGS) to undertake a national helium gas resource assessment to determine the nation's helium resources. An important initial component necessary to complete this assessment was the development of a comprehensive database of Helium (He) concentrations from petroleum exploration wells. Because Helium is often used as the carrier gas for compositional analyses for commercial and exploratory oil and gas wells, this limits the available helium concentration data. A literature search in peer-reviewed publications, state geologic survey databases, USGS energy geochemical databases, and the Bureau of Land Management databases provided approximately 16,000 data points from wells that had measurable He concentrations in the gas composition analyses. The data from these wells includes, date of sample collection, American Petroleum Institute well number, formation name, field name, depth of sample collection, and location. The gas compositional analyses, some performed as far back as 1934, do not all have the same level of precision and accuracy, therefore the date of the analysis is critical to the assessment as it indicates the relative amount of uncertainty in the analytical results. Non-proprietary data was used to create a GIS based interactive web interface that allows users to visualize, inspect, interact, and download our most current He data. The user can click on individual locations to see the available data at that location, as well as zoom in and out on a data density map. Concentrations on the map range from .04 mol% (lowest concentration of economic value) to 12% (highest naturally occurring values). This visual interface will allow users to develop a rapid appreciation of the areas with the highest potential for high helium concentrations within oil and gas fields.

  9. Pressure drop and blower performance tests in very high temperature Helium Experimental LooP (HELP)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chan Soo; Hong, Sung Deok; Kim, Yong Wan [KAERI, Daejeon (Korea, Republic of)

    2012-10-15

    Korea Atomic Energy Research Institute (KAERI) has developed the gas loops to develop and verify the key components of the nuclear hydrogen production system. At the present, KAERI is operating a small scale gas loop for feasibility tests of process heat exchanger and a very high temperature Helium Experimental LooP (HELP) for verification tests of bench scale prototypes for high temperature key components in Very High Temperature gas cooled Reactor (VHTR). Figure 1 presents the HELP assembled with the key components. The size was designed for the verification test of a 150kW intermediate heat exchanger or the simulation test in a 1/6 scaled down fuel block. The loop consists of the primary loop and the secondary loop. The primary loop and the secondary loop simulate VHTR and intermediate loop in nuclear hydrogen production system, respectively. The loops were designed to withstand the maximum temperature of 1000 .Deg. C, the maximum pressure of 9.0 MPa, and the normal mass velocity of 0.5 kg/sec. The working fluid is helium as the actual coolant of VHTR. The primary loop is composed of a preheater, a high temperature heater, a hot gas duct, intermediate heat exchangers, a water cooled U tube heat exchanger, a gas bearing circulator, a passive venting system and gas filters. The secondary loop has the same system configuration as the primary loop except a high temperature heater. Two loops share a helium supply system, a helium purification system and the water loop for a cooling tower as Figure 2. In this study, the experimental results of the bypass line pressure drop and blower performance at the nitrogen condition are analyzed to predict the main line mass flow rates without heaters.

  10. Aimant PS: controle de l'etat des sertissages internes des PFW mesures effectues surl'ensemble des aimants du PS pendant le grand arret 2004/2006

    CERN Document Server

    Ottaviani, J

    2005-01-01

    Les sertissages (douilles), utilisés pour raccorder les méplats du circuit principal des PFW à leurs câbles d’alimentation, présentent parfois des défauts de réalisation qui entraînent une résistance électrique anormale. Pour mettre en évidence ces défauts, la résistance des 4 sertissages des nappes polaires est mesurée. Les nappes sont alimentées avec un courant efficace nominal de 80A.Les mesures sont effectuées entre le bornier de connexions des 4 câbles d’alimentation des PFW et les circuits auxiliaires correspondants (Pick-ups brasés sur les enroulements). De ces mesures (câble d’alimentation et une courte partie du circuit principal) est déduite la valeur de la résistance du sertissage qui en assure la liaison. A la mesure des résistances des sertissages des nappes polaires supérieures s’ajoute la résistance des câbles qui assurent la liaison entre borniers. Dans le cadre de la rénovation des aimants du PS, les 100 unités on été mesurées.

  11. Helium-cooling in fusion power plants

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.P.C.; Baxi, C.B.; Hamilton, C.J.; Schleicher, R.W.; Streckert, H.

    1994-11-01

    This paper reviews different helium-cooled first wall and blanket designs; and compares the selection of structural materials. The authors found that the solid breeder, SiC-composite material option generates the lowest amount of induced radioactivity and afterheat and has the highest temperature capability. When combined with the direct cycle gas turbine system, it has the potential to be the most economical fusion system and can compete with advanced fission reactors. When compared to martensitic steel and V-alloy, SiC-composite is the least developed of these three structural materials, a focused development effort will be needed. Fundamental research has begun in addressing the issues of optimized composite materials, irradiation effects, leak tightness and low activation braze materials. Development of helium-cooled high heat flux components and further development of the direct cycle gas turbine system will also be needed.

  12. Survivor from asphyxiation due to helium inhalation

    Directory of Open Access Journals (Sweden)

    Massimiliano Etteri

    2016-06-01

    Full Text Available In this rare case report we describe a 27- year-old white man survived to suicide by asphyxiation using the so-called suicide bag (or exit bag filled with helium supplied through a plastic tube. He had no previous psychiatric or organic illnesses. At the time of presentation to our Emergency Department he was awake and reported severe dyspnea with a clinical pattern of acute respiratory failure. Imaging studies showed pulmonary edema and the patient was treated with non-invasive ventilation in Intensive Care Unit. After 15 days the patient was discharged from hospital in optimal conditions. These rare cases of survivor might suggest the possible causes of death from inhaling helium.

  13. Laser-Induced Breakdown in Liquid Helium

    Science.gov (United States)

    Sirisky, S.; Yang, Y.; Wei, W.; Maris, H. J.

    2017-10-01

    We report on experiments in which focused laser light is used to induce optical breakdown in liquid helium-4. The threshold intensity has been measured over the temperature range from 1.1 to 2.8 K with light of wavelength 1064 nm. In addition to the measurement of the threshold, we have performed experiments to study how the breakdown from one pulse modifies the probability that a subsequent pulse will result in breakdown.

  14. Correlation of Helium Solubility in Liquid Nitrogen

    Science.gov (United States)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

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

  15. Laser Spectroscopy of Antiprotonic Helium Atoms

    CERN Multimedia

    2002-01-01

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

  16. Dangerosité, longues peines de prison et mesures préventives en Allemagne

    Directory of Open Access Journals (Sweden)

    Axel Dessecker

    2009-10-01

    Full Text Available S’appuyant sur les statistiques des condamnations officielles en Allemagne, notre article entend donner un aperçu de l’évolution historique de la peine d’emprisonnement à perpétuité, de la détention préventive ainsi que des ordonnances de détention en milieu hospitalier pour personnes souffrant de troubles mentaux. En Allemagne, la peine d’emprisonnement à perpétuité est actuellement la punition la plus sévère, mais son rôle était moins important du temps de la peine capitale. La détention préventive et les ordonnances de détention en milieu hospitalier sont, elles, toutes deux perçues comme des mesures préventives dont la durée d’exécution apparaît d’emblée indéterminée. Alors que la question des détentions préventives est largement débattue aujourd’hui, les condamnations prononcées par les cours ont légèrement augmenté. Quant aux ordonnances, elles semblent toujours plus nombreuses.The article gives an overview on the historical development of life sentences, preventive detention, and hospital orders for mentally disordered offenders in Germany on the basis of official conviction statistics. The life sentence is the most severe punishment today, while its role was less important as long as capital punishment existed. Preventive detention and hospital orders both are viewed as preventive measures, and they are indefinite from the beginning. While preventive detention is widely discussed today, convictions by the courts have been increasing from a low level. The level of hospital orders is much higher today. Full Text

  17. Dangerosité, longues peines de prison et mesures préventives en Allemagne

    Directory of Open Access Journals (Sweden)

    Axel Dessecker

    2012-05-01

    Full Text Available S’appuyant sur les statistiques des condamnations officielles en Allemagne, notre article entend donner un aperçu de l’évolution historique de la peine d’emprisonnement à perpétuité, de la détention préventive ainsi que des ordonnances de détention en milieu hospitalier pour personnes souffrant de troubles mentaux. En Allemagne, la peine d’emprisonnement à perpétuité est actuellement la punition la plus sévère, mais son rôle était moins important du temps de la peine capitale. La détention préventive et les ordonnances de détention en milieu hospitalier sont, elles, toutes deux perçues comme des mesures préventives dont la durée d’exécution apparaît d’emblée indéterminée. Alors que la question des détentions préventives est largement débattue aujourd’hui, les condamnations prononcées par les cours ont légèrement augmenté. Quant aux ordonnances, elles semblent toujours plus nombreuses.The article gives an overview on the historical development of life sentences, preventive detention, and hospital orders for mentally disordered offenders in Germany on the basis of official conviction statistics. The life sentence is the most severe punishment today, while its role was less important as long as capital punishment existed. Preventive detention and hospital orders both are viewed as preventive measures, and they are indefinite from the beginning. While preventive detention is widely discussed today, convictions by the courts have been increasing from a low level. The level of hospital orders is much higher today. Full Text

  18. Hot plasma dielectric tensor

    NARCIS (Netherlands)

    Westerhof, E.

    1996-01-01

    The hot plasma dielectric tensor is discussed in its various approximations. Collisionless cyclotron resonant damping and ion/electron Bernstein waves are discussed to exemplify the significance of a kinetic description of plasma waves.

  19. Hot subdwarf stars and their connection to thermonuclear supernovae

    CERN Document Server

    Geier, S; Ziegerer, E; Heber, U; Nemeth, P; Irrgang, A

    2016-01-01

    Hot subdwarf stars (sdO/Bs) are evolved core helium-burning stars with very thin hydrogen envelopes, which can be formed by common envelope ejection. Close sdB binaries with massive white dwarf (WD) companions are potential progenitors of thermonuclear supernovae type Ia (SN Ia). We discovered such a progenitor candidate as well as a candidate for a surviving companion star, which escapes from the Galaxy. More candidates for both types of objects have been found by crossmatching known sdB stars with proper motion and light curve catalogues. The Gaia mission will provide accurate astrometry and light curves of all the stars in our hot subdwarf sample and will allow us to compile a much larger all-sky catalogue of those stars. In this way we expect to find hundreds of progenitor binaries and ejected companions.

  20. Shift and broadening of resonance lines of antiprotonic helium atoms in solid helium

    CERN Document Server

    Adamczak, Andrzej

    2014-01-01

    We have estimated the shift and broadening of the resonance lines in the spectrum of antiprotonic helium atoms $\\bar{p}\\mathrm{He}^{+}$ implanted in solid helium $^4$He. The application of the response function for crystalline helium has enabled determination of the contributions from the collective degrees of freedom to the shift and broadening. It occurs that the broadening due to the collective motion is negligible compared to the natural line width. The available pair-correlation functions for crystalline $^4$He have been applied for estimating the resonance-line shift due to collisions of $\\bar{p}\\mathrm{He}^{+}$ atom with the surrounding $^4$He atoms. The dependence of the line shift, which has been calculated in the quasistatic limit, on the solid-$^4$He density is nonlinear.

  1. Multipurpose closed-cycle cryocooler for liquefying hydrogen, helium-4 or helium-3

    Science.gov (United States)

    Winter, Calvin

    1990-08-01

    A cryogenic refrigerator utilizing helium-4 gas in closed-cycle Gifford-McMahon and Joule-Thomson cooling loops was built and achieves continuous operating temperatures of 2.8R. The object cooled is a thin walled (0.1mm) seamless electroformed nickel target sample cell with a volume of 160m1. Room temperature hydrogen, helium-4 or helium-3 gas, supplied at a pressure slightly above atmospheric, is liquefied by the cryocooler and fills the cell. Unusual features include: horizontal operation; a long narrow extension on the vacuum shroud (900mm long, 76mm diameter) and special valves to select an operating temperature appropriate to the sample gas and maximize the cooling power available at that temperature.

  2. Mesure par conductimetrie de la receptivite aux maladies fongiques et du niveau de resistance induite par elicitation. Etude sur 3 modeles experimentaux

    OpenAIRE

    Molot, P.M.; Mas, P.; Pivot, V; Bruneteau, M; Staron, T; Ferriere, H.; Lemaire, J.M.

    1992-01-01

    L’appréciation des dégâts parasitaires, souvent difficile à évaluer, peut être effectuée par des mesures conductimétriques; en effet, les cellules altérées libèrent davantage d’électrolytes que les cellules saines dans le milieu extérieur, dont on mesure la conductance. Cette méthode peut être utilisée dans différents cas, notamment lorsqu’il y a attaque au niveau racinaire. On mesure alors la conductance de l’eau dans laquelle baignent des racines contaminées (piment - Phytophthora capsici, ...

  3. Translation balance for measuring magnetic susceptibilities at high or low temperatures (1962); Balance de translation pour la mesure des susceptibilites magnetiques a haute ou basse temperature (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Blaise, A.; Peuch, M.A. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1962-07-01

    A translation balance is described for the measurement of the magnetic susceptibilities of liquids or solids in the temperature range from 1.7 to 1400 deg. K. Measurements are made within a magnetic field adjustable from 3400 to 16000 oersteds, in any desired atmosphere. Susceptibilities between 10{sup -8} and 10{sup -4} u.e.m. C.G.S., can be measured. (authors) [French] La balance de translation decrite ici permet la mesure des susceptibilites magnetiques des liquides ou des solides dans la gamme de temperature allant de 1,7 a 1400 deg. K. Les mesures sont effectuees dans un champ magnetique ajustable de 3400 a 16000 oersteds, sous atmosphere controlee. La gamme des mesures de susceptibilite s'etend de 10{sup -8} a 10{sup -4} u.e.m. C.G.S. (auteurs)

  4. Conception et mesures du capital-marque des marques de distributeurs : une application au secteur de la grande distribution

    OpenAIRE

    Jara, Magali

    2008-01-01

    Ce papier tente de définir et de mesurer une première partie du cadre conceptuel du capital-marque des MDD (marques de distributeurs). Pour ce faire, les travaux de Keller (1993) ainsi que les apports théoriques des recherches sur les services dans le secteur de la distribution sont mobilisés. Puis, le modèle conceptuel est précisé par des entretiens individuels de consommateurs. Après une analyse de contenu, un modèle principal du capital-marque des MDD est proposé ajoutant les dimensions d'...

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

    Energy Technology Data Exchange (ETDEWEB)

    WANG,L.; JIA,L.

    2002-07-22

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

  6. Helium liquefaction with a 4 K pulse tube cryocooler

    Science.gov (United States)

    Wang, Chao

    2001-07-01

    Helium liquefaction with a two-stage 4 K pulse tube cryocooler is introduced in this paper. The helium liquefier has a feature of precooling helium gas to be liquefied by using inefficiency of the second stage regenerator in the pulse tube cryocooler. This process reduces enthalpy of the incoming helium gas when entering the condenser and significantly increases the condensation rate. Numerical analysis predicts the precooling heat load on the second stage regenerator, decreases the PTC second stage cooling capacity by only 11% of the heat actually absorbed into the regenerator. A prototype pulse tube helium liquefier was built, which has two precooling heat exchangers on the first stage cold head and the second stage regenerator. It continuously liquefies helium with a rate of 4.8 l/day under normal pressure while consumes 4.6 kW power input.

  7. Diffusion behaviors of helium atoms at two Pd grain boundaries

    Institute of Scientific and Technical Information of China (English)

    XIA Ji-xing; HU Wang-yu; YANG Jian-yu; AO Bing-yun

    2006-01-01

    The diffusion behaviors of helium atoms at two symmetric grain boundaries (Σ5{210} and Σ3 {112}) of Pd were investigated using molecular dynamics simulations through an analytical embedded-atom method(MAEAM) model. The simulations demonstrate that the interstitial helium atoms are easily trapped at the grain boundaries and precipitated into clusters. Due to the closed-shell electronic configurations of both helium and palladium,Pd grain boundaries yield strong capability of retaining helium atoms. By calculating the mean square displacements(MSD) of an interstitial helium atom at the grain boundaries,the diffusion coefficients were determined,and the linear fits to Arrhenius relation. The diffusion activation energies of interstitial helium atom at these two Pd grain boundaries were also evaluated.

  8. Capacity enhancement of indigenous expansion engine based helium liquefier

    Science.gov (United States)

    Doohan, R. S.; Kush, P. K.; Maheshwari, G.

    2017-02-01

    Development of technology and understanding for large capacity helium refrigeration and liquefaction at helium temperature is indispensable for coming-up projects. A new version of helium liquefier designed and built to provide approximately 35 liters of liquid helium per hour. The refrigeration capacity of this reciprocating type expansion engine machine has been increased from its predecessor version with continuous improvement and deficiency debugging. The helium liquefier has been built using components by local industries including cryogenic Aluminum plate fin heat exchangers. Two compressors with nearly identical capacity have been deployed for the operation of system. Together they consume about 110 kW of electric power. The system employs liquid Nitrogen precooling to enhance liquid Helium yield. This paper describes details of the cryogenic expander design improvements, reconfiguration of heat exchangers, performance simulation and their experimental validation.

  9. 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.

  10. Existence of liquid helium above melting curve pressures

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, A.L.; Brewer, D.F.; Naji, T.; Haynes, S. (Sussex Univ., Brighton (UK). Dept. of Physics); Reppy, J.D. (Cornell Univ., Ithaca, NY (USA))

    Data are presented on the specific heat of helium confined at a high externally applied pressure within the 60 A pores of vycor glass. The specific heat shows that the helium within the pores remains in the liquid state down to temperatures well below 1 K. On the other hand the helium outside the vycor behaves normally, changing phase from solid to liquid as it warms.

  11. Non-LTE Line Formation in the Near-IR: Hot Stars

    CERN Document Server

    Przybilla, Norbert

    2010-01-01

    Line-formation calculations in the Rayleigh-Jeans tail of the spectral energy distribution are complicated by an amplification of non-LTE effects. For hot stars this can make quantitative modelling of spectral lines in the near-IR challenging. An introduction to the modelling problems is given and several examples in the context of near-IR line formation for hydrogen and helium are discussed.

  12. Contrôlabilité : Suivi des mesures de CFL réalisées avec des pneumatiques AIPCR 07 et ASTM 07

    OpenAIRE

    Cerezo, Véronique; CENTRE D'ETUDES TECHNIQUES DE L'EQUIPEMENT DE LYON - CETE LYON; LABORATOIRE REGIONAL DES PONTS ET CHAUSSEES DE LYON - CETE DE LYON - LRPC LYON

    2010-01-01

    L'étude a pour objet l'étude du comportement des pneumatiques ASTM 07 et AIPCR 07 par rapport à celui des pneus standards d'essais AIPCR 98 utilisés pour les mesures de coefficient de frottement longitudinal. Tout d'abord, les pneumatiques ASTM 07 et AIPCR 07 semblent plus tendres que les pneus AIPCR 98. Il est nécessaire de les laisser vieillir quelques temps afin de revenir à des niveaux équivalents à ceux des pneus AIPCR 98 utilisés depuis une dizaine d'années en France pour les mesures de...

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

    Science.gov (United States)

    Ringo, Sawnese; Barghouty, A. F.

    2010-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Verma Kuldeep

    2015-01-01

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

  15. Envelope loss of RGB/AGB stars and the formation of hot subdwarfs

    Directory of Open Access Journals (Sweden)

    Chen X.

    2013-03-01

    Full Text Available Low mass stars may lose their envelopes in the first giant branch (RGB or the asymptotic giant branch (AGB via envelope ejection (i.e. superwind. The envelope loss of AGB stars leads to the formation of carbon-oxygen (CO white dwarfs (WDs, while the envelope loss of AGB stars may lead to the formation of helium WDs. We mainly focus here on where a RGB/AGB star loses its envelope during its evolution and we show the inital - final mass relation. We also propose a possible channel for the formation of single hot subdwarf stars, in which an old metal-rich RGB star with positive envelope binding energy may lose its envelope and the naked helium core gets ignited to become a hot subdwarf. We also review the well-established Han et al. scenario for the formation of hot subdwarf stars, in which binary interactions lead to the formation of both single and binary hot subdwarfs. By detailed binary evolution calculations, we show that PG 1018-047, a hot subdwarf binary with a main sequence companion and a very long orbital period of 756  d, is explained naturally from the stable RLOF channel in the Han et al. scenario.

  16. Mesure de la fraction d'evenements a quatre quarks dans les desintegrations multihadroniques du boson Z au LEP

    Science.gov (United States)

    Lefebvre, Eric

    Cette thèse propose de tester la Chromodynamique Quantique (QCD) en effectuant une mesure précise d'une des trois constantes fondamentales du groupe de symétrie SU(3) utilisé pour décrire la physique des interactions fortes. Cette constante fondamentale, appelée TF, est reliée à certains états finaux spécifiques des désintégrations du Z0. Ces états apparaissent sous forme de perturbations du deuxième ordre en as et sont illustrés par des diagrammes de Feynman. À cet ordre, la chromodynamique prévoit deux types de diagrammes de Feynman distincts; le premier contient, un quark, un antiquark et deux gluons, et le second, deux quarks et deux antiquarks. La constante TF est directement proportionnelle à la fraction d'événements à deux quarks et deux antiquarks qui est l'objet de notre mesure. Notre mesure est fondée sur l'étude des événements à quatre partons dans l'état final. Ces quatre partons, en s'hadronisant, produisent quatre jets de particules qui peuvent être détectés expérimentalement et identifiés à l'aide d'algorithmes de reconstruction des jets. Des observables angulaires nous permettent de faire une discrimination parmi les états finaux de la désintégration du Z0, et ainsi déterminer la valeur de la fraction d'événements à deux quarks et deux antiquarks fq. Cette fraction peut s'exprimer par le rapport de la fraction observée expérimentalement fexq sur la fraction théorique fthq , R4q=fex qfthq. Afin d'améliorer la mesure de cette fraction et de diminuer le bruit causé par une contamination des événements d'ordres supérieurs, nous avons développe une méthode d'extrapolation. Cette méthode s'appuie sur la caractérisation de l'espace de phase des événements, exprimée par les paramètres yij. Les mesures de R4q que nous obtenons sont: R4q=2,27+0,29 -0,56 à l'aide d'une méthode conventionnelle avec la condition de sélection y34 > 0,020 > y45, et R4q=1,22+0,56 -0,71 à l'aide de notre méthode d

  17. Computational study of the interaction of cold atmospheric helium plasma jets with surfaces

    Science.gov (United States)

    Breden, Douglas; Raja, Laxminarayan L.

    2014-12-01

    We describe a computational modeling study of a cold atmospheric pressure plasma jet interacting with a dielectric surface placed normal to the jet axis. The plasma jet is generated by the application of a nanosecond pulse voltage applied to a dielectric tube through which the jet issues into ambient air. A base fluid flow field is pre-computed using a Navier-Stokes model for the helium jet impinging on the dielectric target surface with a two-species description for laminar diffusional mixing of the helium and ambient air streams. A self-consistent, multiple species, two-temperature model is used to describe the non-equilibrium plasma discharge dynamics in the presence of the base jet flow field. A single nanosecond pulse discharge event starting from initial breakdown in the dielectric tube, to propagation into the open gap, and finally the interaction with the dielectric surface is simulated. Initially, the plasma forms within the dielectric tube and propagates along the tube surface as a surface discharge driven by large induced electric fields produced by trapped charge on the dielectric surface. When the discharge reaches the end of the dielectric tube, the discharge transitions to a constricted fast ionization wave that propagates along the helium-air interface. The fast ionization wave eventually reaches the dielectric target surface where charged species are deposited as the discharge propagates parallel to the wall as a surface driven discharge. The surface driven discharge ceases to propagate once the quantity of air to helium is sufficient enough to quench the hot electrons and prevent further ionization. Due to the low speed of the flow discharge and the short life times of the radical species such as O, most of the radical species delivered to the surface are a result of the surface discharge that forms after the plasma bullet impinges against the surface. It is found that factors such as the thickness of the target dielectric and the profile of the

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

    CERN Document Server

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

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    S. S. Bulanov

    2015-06-01

    Full Text Available The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons. This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes this species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He^{3} ions, having almost the same penetration depth as He^{4} with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.

  20. IR Hot Wave

    Energy Technology Data Exchange (ETDEWEB)

    Graham, T. B.

    2010-04-01

    The IR Hot Wave{trademark} furnace is a breakthrough heat treatment system for manufacturing metal components. Near-infrared (IR) radiant energy combines with IR convective heating for heat treating. Heat treatment is an essential process in the manufacture of most components. The controlled heating and cooling of a metal or metal alloy alters its physical, mechanical, and sometimes chemical properties without changing the object's shape. The IR Hot Wave{trademark} furnace offers the simplest, quickest, most efficient, and cost-effective heat treatment option for metals and metal alloys. Compared with other heat treatment alternatives, the IR Hot Wave{trademark} system: (1) is 3 to 15 times faster; (2) is 2 to 3 times more energy efficient; (3) is 20% to 50% more cost-effective; (4) has a {+-}1 C thermal profile compared to a {+-}10 C thermal profile for conventional gas furnaces; and (5) has a 25% to 50% smaller footprint.

  1. Hot Air Engines

    Directory of Open Access Journals (Sweden)

    P. Stouffs

    2011-01-01

    Full Text Available Invented in 1816, the hot-air engines have known significant commercial success in the nineteenth century, before falling into disuse. Nowadays they enjoy a renewed interest for some specific applications. The "hot-air engines" family is made up of two groups: Stirling engines and Ericsson engines. The operating principle of Stirling and Ericsson engines, their troubled history, their advantages and their niche applications are briefly presented, especially in the field of micro-combined heat and power, solar energy conversion and biomass energy conversion. The design of an open cycle Ericsson engine for solar application is proposed. A first prototype of the hot part of the engine has been built and tested. Experimental results are presented.

  2. Tritium enrichment by thermal diffusion. I. Calculation of an installation for measuring natural tritium; Enrichissement du tritium par diffusion thermique. - I. Calcul d'une installation destinee a la mesure du tritium naturel

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, M.; Ravoire, J. [Commissariat a l' Energie Atomique, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)

    1966-07-01

    The natural content of tritium is so low that its measurement generally requires a preliminary enrichment. The thermal diffusion on hydrogen is studied as an enrichment method. The installation studied comprises two stages of columns of the hot-wire type, together with a device for transferring the tritium from the water sample into the hydrogen in the columns using catalytic exchange. A complete mathematical treatment for the operation of such a unit has been made and programmed for the IBM 7094 computer. An optimization has been effected by means of this program. It is shown that for similar performances, less hydrogen is retained in the case of hot-wire type columns than in the case of columns composed of concentric tubes. (authors) [French] La teneur naturelle du tritium est si faible que sa mesure demande generalement un enrichissement prealable. On etudie la diffusion thermique sur l'hydrogene comme moyen d'enrichissement. L'installation que l'on etudie comprend deux etages de colonnes du type fil chaud, et un dispositif de transfert du tritium de l'echantillon d'eau dans l'hydrogene des colonnes par echange catalytique. Un traitement mathematique complet du fonctionnement d'un tel ensemble a ete etabli et programme sur machine IBM 7094. Une optimisation a ete faite a l'aide du programme. On montre egalement qu'a performances egales, la retenue d'hydrogene est plus faible dans le cas des colonnes du type fil chaud que dans le cas des colonnes du type tubes concentriques. (auteurs)

  3. Lamb shift in muonic helium ion

    CERN Document Server

    Martynenko, A P

    2006-01-01

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

  4. Heat capacity of helium in cylindrical environments

    Science.gov (United States)

    Gatica, S. M.; Hernández, E. S.; Szybisz, L.

    2003-10-01

    We perform a systematic investigation of the structure, elementary, and phonon excitations of quantum fluid 4He adsorbed in the interior of carbon nanotubes. We show that the helium fluid inside the cylinder behaves exactly as in planar films on a graphite substrate, presenting the same kind of layering transition. This tendency is confirmed by the behavior of a single 3He impurity diluted into adsorbed 4He. We also present a simple description of the lowest excitation modes of the adsorbed fluid and compute the low-temperature contribution of the phonon spectrum to the specific heat, which displays the dimensionality characteristics reported in previous works.

  5. Fano Resonances observed in Helium Nanodroplets

    CERN Document Server

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

    2015-01-01

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

  6. Variable helium diffusion characteristics in fluorite

    Science.gov (United States)

    Wolff, R.; Dunkl, I.; Kempe, U.; Stockli, D.; Wiedenbeck, M.; von Eynatten, H.

    2016-09-01

    Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite (U-Th-Sm)/He thermochronometer (FHe), which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers. Incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism. The diffusion behaviour is highly variable and the parameters range between log D0/a2 = 0.30 ± 0.27-7.27 ± 0.46 s-1 and Ea = 96 ± 3.5-182 ± 3.8 kJ/mol. Despite the fact that the CaF2 content of natural fluorites in most cases exceeds 99 weight percent, the closure temperature (Tc) of the fluorite (U-Th-Sm)/He thermochronometer as calculated from these diffusion parameters varies between 46 ± 14 °C and 169 ± 9 °C, considering a 125 μm fragment size. Here we establish that minor substitutions of calcium by rare earth elements and yttrium (REE + Y) and related charge compensation by sodium, fluorine, oxygen and/or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral. With increasing REE + Y concentrations F vacancies are reduced and key diffusion pathways are narrowed. Consequently, a higher closure temperature is to be expected. An empirical case study confirms this variability: two fluorite samples from the same deposit (Horni Krupka, Czech Republic) with ca. 170 °C and ca. 43 °C Tc yield highly different (U-Th-Sm)/He ages of 290 ± 10 Ma and 79 ± 10 Ma, respectively. Accordingly, the fluorite sample with the high Tc could have quantitatively retained helium since the formation of the fluorite-bearing ores in the Permian, despite subsequent Mesozoic burial and associated regional hydrothermal heating. In contrast, the fluorite with the low Tc yields a Late Cretaceous age close to the apatite fission track (AFT) and apatite (U-Th)/He ages (AHe

  7. Influence of Helium in Gravitational Instabilities

    Science.gov (United States)

    Corona-Galindo, M. G.; Cardona, O.; Klapp, J.

    1990-11-01

    RESUMEN. Hemos analizado los modos hid rod inamicos de un modelo de fluido de dos componentes (hidr6geno y helio), y hemos obtenido la condici6n de inestabilidad para masas mayores que 1.39 veces la bien conocida masa dejeans. ABSTRACT, We have analysed the hydrodynamical modes of a two component fluid model (hydrogen and helium), and we have obtained the instability condition for masses greater than 1.39 times the well-known Jeans mass. K words: COSMOLOGY - GRAVITATION - INSTABILITIES

  8. Deposition, milling, and etching with a focused helium ion beam

    NARCIS (Netherlands)

    Alkemade, P.F.A.; Veldhoven, E. van

    2012-01-01

    The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or

  9. Laser-Induced Rotation of Iodine Molecules in Helium Nanodroplets

    DEFF Research Database (Denmark)

    Shepperson, Benjamin; Sondergaard, Anders A.; Christiansen, Lars

    2017-01-01

    Rotation of molecules embedded in helium nanodroplets is explored by a combination of fs laser-induced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective...... its helium shell. Our results open novel opportunities for studying nonequilibrium solute-solvent dynamics and quantum thermalization....

  10. Helium on Venus - Implications for uranium and thorium

    Science.gov (United States)

    Prather, M. J.; Mcelroy, M. B.

    1983-01-01

    Helium is removed at an average rate of 10 to the 6th atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on earth, suggesting comparable abundances of crustal uranium and thorium.

  11. Thermal Desorption of Helium Implanted in Tungsten at RT

    Institute of Scientific and Technical Information of China (English)

    ZHANGFu; XUZengyu; LIUXiang; CHENJiming; XUYing; N.Yoshida; H.Iwakiri

    2002-01-01

    Tungsten is envisaged as one of the main candidate materials for divertor plate of ITER and future fusion reactors. Due to D-T reaction, PFMs would suffer helium irradiation from plasma additional to the high heat loads. Helium retention and thermal desorption behavior are largely concerned.

  12. Deposition, milling, and etching with a focused helium ion beam

    NARCIS (Netherlands)

    Alkemade, P.F.A.; Veldhoven, E. van

    2012-01-01

    The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or

  13. Turnkey Helium Purification and Liquefaction Plant for DARWIN, Australia

    Science.gov (United States)

    Lindemann, U.; Boeck, S.; Blum, L.; Kurtcuoglu, K.

    2010-04-01

    The Linde Group, through its Australian subsidiary BOC Limited, has signed an agreement with Darwin LNG Pty Ltd for the supply of feed-gas to Linde's new helium refining and liquefaction facility in Darwin, Australia. Linde Kryotechnik AG, located in Switzerland, has carried out the engineering and fabrication of the equipment for the turn key helium plant. The raw feed gas flow of 20'730 Nm3/h contains up to of 3 mol% helium. The purification process of the feed gas consists of partial condensation of nitrogen in two stages, cryogenic adsorption and finally catalytic oxidation of hydrogen followed by a dryer system. Downstream of the purification the refined helium is liquefied using a modified Bryton process and stored in a 30'000 gal LHe tank. For further distribution and export of the liquid helium there are two stations available for filling of truck trailers and containers. The liquid nitrogen, required for refrigeration capacity to the nitrogen removal stages in the purification process as well as for the pre-cooling of the pure helium in the liquefaction process, is generated on site during the feed gas purification process. The optimized process provides low power consumption, maximum helium recovery and a minimum helium loss.

  14. The Orsay polarized electron source from a flowing helium afterglow

    Science.gov (United States)

    Arianer, J.; Brissaud, I.; Essabaa, S.; Humblot, H.; Zerhouni, W.

    1993-12-01

    A polarized electron source was designed at Orsay. We have chosen to adapt the flowing helium afterglow source working at Rice University because it provides a very high polarization. We have investigated a new way for the optical pumping of the helium metastables. An 85% electron polarization was reached.

  15. Neutrons on a surface of liquid helium

    Science.gov (United States)

    Grigoriev, P. D.; Zimmer, O.; Grigoriev, A. D.; Ziman, T.

    2016-08-01

    We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyze the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons, and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time of these UCNs at 0.7 K is found to exceed 1 h, and rapidly increases with decreasing temperature. Such low scattering rates should enable high-precision measurements of the sequence of discrete energy levels, thus providing improved tests of short-range gravity. The system might also be useful for neutron β -decay experiments. We also sketch new experimental propositions for level population and trapping of ultracold neutrons above a flat horizontal mirror.

  16. Neutrons on a surface of liquid helium

    CERN Document Server

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

    2015-01-01

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

  17. Liquid uranium alloy-helium fission reactor

    Science.gov (United States)

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  18. Mining for helium: Site selection and evaluation

    Science.gov (United States)

    Cameron, Eugene N.

    1988-09-01

    Part of the University of Wisconsin study of the feasibility of recovering He-3 from the moon is selection and evaluation of potential mining sites. Selection and evaluation are based primarily on salient findings by investigators: (1) Regoliths from areas underlain by highland materials contain less than 20 wppm He; (2) Regoliths of certain maria or parts of maria also contain less than 20 wppm He, but mare regoliths at the Apollo 11 and 17 sites contain 25 to 49 wppm He; (3) The helium content of a regolith is a function of its composition; and (4) Helium is concentrated in the -50 micron size fractions of regoliths. In site selection, the concern is with the compositions of lunar regoliths, in particular with their titanium contents. It is widely accepted that compositions of mare regoliths are controlled by the nature of the underlying basalts from which the regoliths are largely derived. The distribution and extent of the three groups of basalts and the regoliths derived from them are the first basis for site selection and evaluation. Other considerations are briefly discussed.

  19. Submersion of potassium clusters in helium nanodroplets

    Science.gov (United States)

    An der Lan, Lukas; Bartl, Peter; Leidlmair, Christian; Schöbel, Harald; Denifl, Stephan; Märk, Tilmann D.; Ellis, Andrew M.; Scheier, Paul

    2012-03-01

    Small alkali clusters do not submerge in liquid helium nanodroplets but instead survive predominantly in high spin states that reside on the surface of the nanodroplet. However, a recent theoretical prediction by Stark and Kresin [Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.81.085401 81, 085401 (2010)], based on a classical description of the energetics of bubble formation for a fully submerged alkali cluster, suggests that the alkali clusters can submerge on energetic grounds when they exceed a critical size. Following recent work on sodium clusters, where ion yield data from electron impact mass spectrometry was used to obtain the first experimental evidence for alkali cluster submersion, we report here on similar experiments for potassium clusters. Evidence is presented for full cluster submersion at n>80 for Kn clusters, which is in good agreement with the recent theoretical prediction. In an additional observation, we report “magic number” sizes for both Kn+ and Kn2+ ions derived from helium droplets, which are found to be consistent with the jellium model.

  20. 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...

  1. Diagnostics of a High Pressure Helium Microplasma

    Science.gov (United States)

    Wang, Qiang; Koleva, Ivanka; Economou, Demetre; Donnelly, Vincent

    2004-09-01

    Gas and plasma diagnostics were performed in a slot-type DC microplasma (200 microns gap) discharge at high pressures. The gas temperature in a helium discharge was estimated by adding small quantities of nitrogen (excimer. At 250 Torr pressure and 200 mA/cm2 current density, the gas temperature was Tg = 350 +/- 25 K. The measured gas temperature was almost independent (to within experimental uncertainty) of pressure (in the range of 150 Torr - 600 Torr), and current density (in the range of 100 mA/cm2 - 400 mA/cm2). These measurements were consistent with a simple heat transfer model. Spatially resolved measurements of electron temperature were also performed using trace rare gas optical emission actinometry (TRG-OES). These measurements are greatly complicated by collisional quenching at the high operating pressures. Electron density and electron temperature profiles was deduced by comparing emission intensities from the Paschen 2px (x = 1-10) manifold of Ne, Ar, Kr and Xe trace gases. Results suggested that the electron temperature peaks in the cathode sheath region, while the plasma density peaks away from the cathode sheath. A self-consistent fluid model of a DC helium microdischarge was in agreement with the experimental data. The model was used to study the dependence of discharge characteristics on operating conditions (pressure, gap spacing, current density, etc.).

  2. High-precision spectroscopy of antiprotonic helium

    CERN Document Server

    Widmann, E

    2001-01-01

    We present first results of laser and microwave spectroscopy experiments of antiprotonic helium performed at the new Antiproton Decelerator (AD) at CERN. Extending a series of previous measurements done at the Low Energy Antiproton Ring (LEAR) of CERN, several laser- induced transitions of the antiproton in the exotic three-body system He/sup 2+/-e/sup -/-p could be determined with a precision down to 1.3*10/sup -7/. This constitutes an improvement of a factor 3 over previous measurements, and allows to test accurate three-body calculations of this system that include QED corrections. The observed agreement on the same level can be used to infer CPT limits on the antiproton charge and mass. Furthermore, a first indication of a resonance signal of a two-laser microwave triple experiment to measure the hyperfine splitting of antiprotonic helium could been observed. Such a measurement has the potential to determine the antiproton magnetic moment to a higher precision that it is known today. (19 refs).

  3. Ultrasonic Hot Embossing

    Directory of Open Access Journals (Sweden)

    Werner Karl Schomburg

    2011-05-01

    Full Text Available Ultrasonic hot embossing is a new process for fast and low-cost production of micro systems from polymer. Investment costs are on the order of 20.000 € and cycle times are a few seconds. Microstructures are fabricated on polymer foils and can be combined to three-dimensional systems by ultrasonic welding.

  4. What's Hot? What's Not?

    Science.gov (United States)

    Buczynski, Sandy

    2006-01-01

    When Goldilocks finds three bowls of porridge at different temperatures in the three bears' house, she accurately assesses the situation and comes up with one of the most recognizable lines in children's literature," This porridge is too hot; this porridge is too cold; aahh, this porridge is just right!" Goldilocks' famous line is a perfect…

  5. Hot house bad house

    OpenAIRE

    Azzopardi, Shaun

    2014-01-01

    Shaun Azzopardi met up with a team of researchers led by Eur. Ing. Charles Yousif to take the concrete block to the next level. It is more exciting than it sounds. Photography by Dr Edward Duca. http://www.um.edu.mt/think/hot-house-bad-house/

  6. Fending Off Hot Money

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Amid uncertainties about the amount of hot money,the government strives to curb the harmful capital The benchmark Shanghai Composite Index was plagued by dips, climbs and dives as the stock market slumped from 3,186 to 2,838 points

  7. Shock Compression of Liquid Helium to 56 GPa (560) Kbar

    Science.gov (United States)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Trainor, R. J.; Governo, G. K.; Ross, M.; Young, D. A.

    1985-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  8. Shock compression of liquid helium to 56 GPa (560 kbar)

    Science.gov (United States)

    Nellis, W. J.; Holmes, N. C.; Mitchell, A. C.; Governo, G. K.; Ross, M.; Young, D. A.; Trainor, R. J.

    1984-01-01

    Shock-wave data are presented for liquid helium which has been compressed to densities up to five times greater than the normal liquid. The helium was heated to temperatures up to 21,000 K, while the maximum pressure attained was 56 GPa. The properties of helium and hydrogen are important for modeling the giant planets Saturn and Jupiter where these elements are the major constituents. Conditions on Saturn are of particular interest because studies have suggested that this planet has an internal energy source which is associated with unmixing and gravitational separation of the hydrogen-helium fluid at pressures below 1 TPa. The existence of this phase transition depends very sensitively on the hydrogen and helium equation of state. In the experiments, strong shock waves were generated by the impact of planar projectiles into cryogenic specimen holders.

  9. Localized helium excitations in 4He_N-benzene clusters

    CERN Document Server

    Huang, P; Huang, Patrick

    2003-01-01

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

  10. Updated conceptual design of helium cooling ceramic blanket for HCCB-DEMO

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Suhao [University of Science and Technology of China, Hefei, Anhui (China); Southwestern Institute of Physics, Chengdu, Sichuan (China); Cao, Qixiang; Wu, Xinghua; Wang, Xiaoyu; Zhang, Guoshu [Southwestern Institute of Physics, Chengdu, Sichuan (China); Feng, Kaiming, E-mail: fengkm@swip.ac.cn [Southwestern Institute of Physics, Chengdu, Sichuan (China)

    2016-11-15

    Highlights: • An updated design of Helium Cooled Ceramic breeder Blanket (HCCB) for HCCB-DEMO is proposed in this paper. • The Breeder Unit is transformed to TBM-like sub-modules, with double “banana” shape tritium breeder. Each sub-module is inserted in space formed by Stiffen Grids (SGs). • The performance analysis is performed based on the R&D development of material, fabrication technology and safety assessment in CN ITER TBM program. • Hot spots will be located at the FW bend side. - Abstract: The basic definition of the HCCB-DEMO plant and preliminary blanket designed by Southwestern Institution of Physics was proposed in 2009. The DEMO fusion power is 2550 MW and electric power is 800 MW. Based on development of R&D in breeding blanket, a conceptual design of helium cooled blanket with ceramic breeder in HCCB-DEMO was presented. The main design features of the HCCB-DEMO blanket were: (1) CLF-1 structure materials, Be multiplier and Li{sub 4}SiO{sub 4} breeder; (2) neutronic wall load is 2.3 MW/m{sup 2} and surface heat flux is 0.43 MW/m{sup 2} (2) TBR ≈ 1.15; (3) geometry of breeding units is ITER TBM-like segmentation; (4)Pressure of helium is 8 MPa and inlet/outlet temperature is 300/500 °C. On the basis of these design, some important analytical results are presented in aspects of (i) neutronic behavior of the blanket; (ii) design of 3D structure and thermal-hydraulic lay-out for breeding blanket module; (iii) structural-mechanical behavior of the blanket under pressurization. All of these assessments proved current stucture fulfill the design requirements.

  11. How does the Warm Breeze affect the heliospheric backscatter glow of interstellar neutral helium?

    Science.gov (United States)

    Bzowski, Maciej; Kubiak, Marzena; Sokół, Justyna

    2017-04-01

    Based on direct sampling observations of interstellar neutral helium (ISN He) by IBEX, we have discovered a new population of ISN He, dubbed the Warm Breeze (WB), and identified it as the secondary population of ISN He, created in the outer heliosheath. The WB flow is twice slower and hotter by half than the primary ISN He, and it flows from a direction different by 5° in longitude and 6° in latitude. Its density is 5% of that of ISN He. ISN He had been extensively studied in the past by analysis of the backscatter glow, but the WB was not considered in these analyses because its existence had been unknown. However, the ISN He speed and temperature derived from analyses of the heliospheric helium glow tended to be systematically biased towards slower speeds or higher temperatures with respect to those obtained from direct-sampling experiments. We calculate the expected intensity of the backscatter glow due to the ISN He and WB using the best-fit parameters recently obtained from IBEX direct-sampling observations and compare its distribution in the sky with that expected only from the primary ISN gas. In the modeling, we use a time-dependent hot model of Maxwell-Boltzmann distribution of ISN gas and carefully account for the bulk velocities and temperatures of the direct and indirect beams of the two populations, as well as for details of the ionization rates. We discuss differences between intensities of the backscatter glow expected from different regions in the sky, obtained for the models including and excluding the WB and point out that the absence of the WB component in the modeling may have biased the parameters of the primary population of ISN He derived from the helium backscatter glow and lead to underestimating the Mach number of the flow, due to a slower bulk speed or higher temperature.

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

    Science.gov (United States)

    Harbola, Varun

    2011-01-01

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

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

    Science.gov (United States)

    Harbola, Varun

    2011-01-01

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

  14. Hot Fuel Examination Facility (HFEF)

    Data.gov (United States)

    Federal Laboratory Consortium — The Hot Fuel Examination Facility (HFEF) is one of the largest hot cells dedicated to radioactive materials research at Idaho National Laboratory (INL). The nation's...

  15. La mesure des performances corporelles extraordinaires dans les métiers du sport, du luxe et de l’art

    Directory of Open Access Journals (Sweden)

    Stéphane Héas

    2009-10-01

    Full Text Available La mesure des performances est aujourd’hui omniprésente dans les sports. Cette quantification corporelle n’étonne plus outre mesure. Elle est devenue sociologique. Les affaires de dopage ne fragilisent pas cette tendance. Les performances sportives de l’élite mondiale sont devenues très éloignées de ce que le commun des mortels peut envisager. Elles sont incroyables et pourtant réelles. Parfois, une fraction de seconde seulement sépare le bonheur de la victoire de la désillusion d’une défaite. En dehors des arènes sportives, d’autres performances sont réalisées. C’est le cas par exemple des équilibristes, des «nez» dans de nombreux secteurs (viniculture, cosmétique, etc., des contorsionnistes, des imitateurs, etc. A travers 21 entretiens, nous esquissons l’étendue des performances réalisées, donc leurs mesures multiples. Comment ces performances, le plus souvent chiffrées (en nombre de fragrances testées par jour, en minutes d’équilibre maintenu sur un rouleau, etc., sont-elles vécues? Les exercices et les excès corporels sont devenus leur quotidien, la mesure, leur étalon… qu’ils tentent de maintenir ou de varier avec l’âge, à mesure que leurs capacités déclinent.

  16. Helium-Charged Titanium Films Deposited by Pulsed Laser Deposition in an Electron-Cyclotron-Resonance Helium Plasma Environment

    Institute of Scientific and Technical Information of China (English)

    金钦华; 胡佩钢; 凌浩; 吴嘉达; 施立群; 周筑颖

    2003-01-01

    Titanium thin films incorporated with helium are produced by pulsed laser deposition in an electron cyclotron resonance helium plasma environment. Helium is distributed evenly in the film and a relatively high He/Ti atomic ratio (~ 20%) is obtained from the proton backscattering spectroscopy. This high concentration ofhelium leads to a surface blistering which is observed by scanning electron microscopy. Laser repetition rate has little influence on film characters. Substrate bias voltage is also changed for the helium incorporating mechanism study, and this is a helium ion implantation process during the film growth. Choosing suitable substrate bias voltage, one can avoid the damage produced by ion implantation, which is always present in general implantation case.

  17. submitter Superconducting instrumentation for high Reynolds turbulence experiments with low temperature gaseous helium

    CERN Document Server

    Pietropinto, S; Baudet, C; Castaing, B; Chabaud, B; Gagne, Y; Hébral, B; Ladam, Y; Lebrun, P; Pirotte, O; Roche, P

    2003-01-01

    Turbulence is of common experience and of high interest for industrial applications, despite its physical grounds is still not understood. Cryogenic gaseous helium gives access to extremely high Reynolds numbers (Re). We describe an instrumentation hosted in CERN, which provides a 6 kW @ 4.5 K helium refrigerator directly connected to the experiment. The flow is a round jet; the flow rates range from 20 g/s up to 260 g/s at 4.8 K and about 1.2 bar, giving access to the highest controlled Re flow ever developed. The experimental challenge lies in the range of scales which have to be investigated: from the smallest viscous scale η, typically 1 μm at Re=107 to the largest L∼10 cm. The corresponding frequencies: f=v/η can be as large as 1 MHz. The development of an original micrometric superconducting anemometer using a hot spot and its characteristics will be discussed together with its operation and the perspectives associated with superconducting anemometry.

  18. Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars

    CERN Document Server

    Jeffery, C Simon; Saio, Hideyuki

    2011-01-01

    The surface abundances of extreme helium (EHe) and R Coronae Borealis (RCB) stars are discussed in terms of the merger of a carbon-oxygen white dwarf with a helium white dwarf. The model is expressed as a linear mixture of the individual layers of both constituent white dwarfs, taking account of the specific evolution of each star. In developing this recipe from previous versions, particular attention has been given to the inter-shell abundances of the asymptotic giant branch star which evolved to become the carbon-oxygen white dwarf. Thus the surface composition of the merged star is estimated as a function of the initial mass and metallicity of its progenitor. The question of whether additional nucleosynthesis occurs during the white dwarf merger has been examined. The high observed abundances of carbon and oxygen must either originate by dredge-up from the core of the carbon-oxygen white dwarf during a cold merger or be generated directly by alpha-burning during a hot merger. The presence of large quantiti...

  19. Study of Temperature Wave Propagation in Superfluid Helium Focusing on Radio-Frequency Cavity Cooling

    CERN Document Server

    Koettig, T; Avellino, S; Junginger, T; Bremer, J

    2015-01-01

    Oscillating Superleak Transducers (OSTs) can be used to localize quenches of superconducting radio-frequency cavities. Local hot spots at the cavity surface initiate temperature waves in the surrounding superfluid helium that acts as cooling fluid at typical temperatures in the range of 1.6 K to 2 K. The temperature wave is characterised by the properties of superfluid helium such as the second sound velocity. For high heat load densities second sound velocities greater than the standard literature values are observed. This fast propagation has been verified in dedicated small scale experiments. Resistors were used to simulate the quench spots under controlled conditions. The three dimensional propagation of second sound is linked to OST signals. The aim of this study is to improve the understanding of the OST signal especially the incident angle dependency. The characterised OSTs are used as a tool for quench localisation on a real size cavity. Their sensitivity as well as the time resolution was proven to b...

  20. Formation of gas discharging from Taketomi submarine hot spring off Ishigaki Island in the southern Ryukyu Islands, Japan

    Science.gov (United States)

    Toki, Tomohiro; Iwata, Daigo; Tsunogai, Urumu; Komatsu, Daisuke D.; Sano, Yuji; Takahata, Naoto; Hamasaki, Hiroshi; Ishibashi, Jun-ichiro

    2017-01-01

    Taketomi submarine hot spring lies off Ishigaki Island in the southern Ryukyu Islands and vents hot spring waters at temperatures up to 50 °C from the seafloor at a depth of 20 m. We investigated the chemical and isotopic composition of gases discharging from Taketomi hot spring. The gases were composed mainly of methane, with secondary nitrogen at higher than atmospheric concentration. Carbon and hydrogen isotope data suggest that the methane in the discharging gases was derived mainly from thermal decomposition of organic matter. Helium isotopes were enriched in 3He relative to the atmosphere, suggesting a supply of mantle-derived helium to the discharging gases. The mantle-derived gases transfer the deep-originated thermal energy to the hot spring and thermogenesis of organic matter. The hydrocarbons in the venting gas could be sourced from sedimentary rocks of the Yaeyama or Shimajiri Groups, or Yaeyama metamorphic rocks, and added to the ascending gases as they pass through those source rocks on their way to the surface. Because the Pleistocene rocks of the Ryukyu Group beneath the hot spring have been altered by the spring activity, the Taketomi hot spring began venting after the Pleistocene.

  1. What Is Hot Yoga (Bikram)?

    Science.gov (United States)

    Healthy Lifestyle Consumer health What is hot yoga? Answers from Edward R. Laskowski, M.D. Hot yoga is a vigorous form of yoga performed in a studio ... you check with your doctor before trying hot yoga if you have any health concerns. If you have heart disease, problems with ...

  2. 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

  3. Techniques for the measurement of the contamination of air; Technique de mesure de la contamination de l'air

    Energy Technology Data Exchange (ETDEWEB)

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

    1960-07-01

    This lecture has been given at the International Symposium of Riso 1959. Methods for measuring radioactive content of the atmosphere are described, and main results found at Saclay are given, for the following contaminants: Rn, Tn and their daughter, H-3, C-14, A-41, Kr-85, I-131, and fission products as a whole. (author) [French] Ce texte est celui d'une conference-rapport prononcee au Colloque International de Riso en 1959. On indique les techniques de mesures de la contamination radioactive de l'atmosphere et les principaux resultats obtenus jusqu'ici au CEA pour: Rn et Tn et leurs derives, H-3, C-14, A-41, Kr-85, I-131, et l'ensemble des produits de fission. (auteur)

  4. Radiation measurements in the reactors G 2 and G 3; Mesures de rayonnement aupres des piles G 2 - G 3

    Energy Technology Data Exchange (ETDEWEB)

    Chassany, J.Ph.; Estournel, R. [Commissariat a l' Energie Atomique, Centre de Production de Plutonium, Marcoule (France). Centre d' Etudes Nucleaires

    1964-07-01

    The results are given of numerous radiation measurements: - for the various working sites - for the various zones (circuit room,etc) - during the discharging operations - far various active materials (CO{sub 2}, plugs etc). They show that in general the protection has been suitably designed and that the majority of radio-protection problems are due to the elements activated in the pile and transported outside the vessel. (authors) [French] Les resultats de nombreuses mesures d'irradiation sont donnes - pour les differents lieux de travail - pour diverses zones (salle de tuyauteries, etc.) - pendant les operations de dechargement - pour differents materiaux actives (CO{sub 2}, bouchons, etc.) Ils montrent que les protections ont ete en general correctement dimensionnees et que la majorite des problemes de radioprotection est constituee par les elements actives dans la pile, transportes a l'exterieur du caisson. (auteurs)

  5. Mesure de la qualité des services d’enseignement et restructuration des secteurs éducatifs

    OpenAIRE

    Vinokur, Annie

    2012-01-01

    L’article de Romuald Normand a décrit la genèse, aux États-Unis, du mouvement de mobilisation des technologies de mesure de la qualité pour rationaliser la pédagogie scolaire sur le modèle industriel. Ce modèle tend maintenant à s’étendre à l’évaluation de la qualité des producteurs de services d’enseignement et à se déployer à l’échelle mondiale dans le but d’accroître l’efficacité des secteurs éducatifs et de réguler leur transnationalisation. On tente ici d’en montrer la fonctionnalité – m...

  6. Evaluation mécanique d'une dalle précontrainte par mesure de la courbure

    OpenAIRE

    COLLIN, B; TONNOIR, B

    2001-01-01

    L'évaluation mécanique d'un ouvrage d'art a été réalisée en utilisant conjointement, et pour la première fois sur une dalle isostatique en béton précontraint, deux prototypes de courburemètre du réseau des LPC. Cette évaluation s'est appuyée sur des mesures, faites en plusieurs sections, des variations de courbure causées par la circulation sur l'ouvrage d'un convoi de caractéristiques connues. D'un point de vue pratique, la facilité d'utilisation des courburemètres, simplement posés sur la c...

  7. The hot Hagedorn Universe

    CERN Document Server

    Rafelski, Johann

    2016-01-01

    In the context of the half-centenary of Hagedorn temperature and the statistical bootstrap model (SBM) we present a short account of how these insights coincided with the establishment of the hot big-bang model (BBM) and helped resolve some of the early philosophical difficulties. We then turn attention to the present day context and show the dominance of strong interaction quark and gluon degrees of freedom in the early stage, helping to characterize the properties of the hot Universe. We focus attention on the current experimental insights about cosmic microwave background (CMB) temperature fluctuation, and develop a much improved understanding of the neutrino freeze-out, in this way paving the path to the opening of a direct connection of quark-gluon plasma (QGP) physics in the early Universe with the QCD-lattice, and the study of the properties of QGP formed in the laboratory.

  8. The hot chocolate effect

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Frank S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    1982-05-01

    The "hot chocolate effect" was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the ten percent accuracy of the experiments.

  9. Hot chocolate effect

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, F.S.

    1982-05-01

    The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.

  10. Hot Spring Metagenomics

    Directory of Open Access Journals (Sweden)

    Olalla López-López

    2013-04-01

    Full Text Available Hot springs have been investigated since the XIX century, but isolation and examination of their thermophilic microbial inhabitants did not start until the 1950s. Many thermophilic microorganisms and their viruses have since been discovered, although the real complexity of thermal communities was envisaged when research based on PCR amplification of the 16S rRNA genes arose. Thereafter, the possibility of cloning and sequencing the total environmental DNA, defined as metagenome, and the study of the genes rescued in the metagenomic libraries and assemblies made it possible to gain a more comprehensive understanding of microbial communities—their diversity, structure, the interactions existing between their components, and the factors shaping the nature of these communities. In the last decade, hot springs have been a source of thermophilic enzymes of industrial interest, encouraging further study of the poorly understood diversity of microbial life in these habitats.

  11. An Update of the Primordial Helium Abundance

    Science.gov (United States)

    Peimbert, Antonio; Peimbert, Manuel; Luridiana, Valentina

    2015-08-01

    Three of the best determinations of the primordial helium abundance (Yp) are those obtained from low metallicity HII regions by Aver, Olive, Porter, & Skillman (2013); Izotov, Thuan, & Guseva (2014); and Peimbert, Peimbert, & Luridiana (2007). In this poster we update the Yp determination by Peimbert et al. taking into account, among other aspects, recent advances in the determination of the He atomic physical parameters, the temperature structure, the collisional effects of high temperatures on the Balmer lines, as well as the effect of H and He bound-bound absorption.We compare our results with those of Aver et al. and Izotov et al. and point out possible explanations for the differences among the three determinations. We also compare our results with those obtained with the Plank satellite considering recent measurements of the neutron mean life; this comparison has implications on the determination of the number of light neutrino families.

  12. The primordial helium abundance from updated emissivities

    CERN Document Server

    Aver, Erik; Porter, R L; Skillman, Evan D

    2013-01-01

    Observations of metal-poor extragalactic H II regions allow the determination of the primordial helium abundance, Y_p. The He I emissivities are the foundation of the model of the H II region's emission. Porter, Ferland, Storey, & Detisch (2012) have recently published updated He I emissivities based on improved photoionization cross-sections. We incorporate these new atomic data and update our recent Markov Chain Monte Carlo analysis of the dataset published by Izotov, Thuan, & Stasinska (2007). As before, cuts are made to promote quality and reliability, and only solutions which fit the data within 95% confidence level are used to determine the primordial He abundance. The previously qualifying dataset is almost entirely retained and with strong concordance between the physical parameters. Overall, an upward bias from the new emissivities leads to a decrease in Y_p. In addition, we find a general trend to larger uncertainties in individual objects (due to changes in the emissivities) and an increase...

  13. Lunar helium-3 and fusion power

    Energy Technology Data Exchange (ETDEWEB)

    1988-09-01

    The NASA Office of Exploration sponsored the NASA Lunar helium-3 and fusion power Workshop. The meeting was held to understand the potential of using He-3 from the moon for terrestrial fusion power production. It provided an overview, two parallel working sessions, a review of sessions, and discussions. The lunar mining session concluded that mining, beneficiation, separation, and return of He-3 from the moon would be possible but that a large scale operation and improved technology is required. The fusion power session concluded that: (1) that He-3 offers significant, possibly compelling, advantages over fusion of tritium, principally increased reactor life, reduced radioactive wastes, and high efficiency conversion, (2) that detailed assessment of the potential of the D/He-3 fuel cycle requires more information, and (3) D/He-3 fusion may be best for commercial purposes, although D/T fusion is more near term.

  14. Lunar Helium-3 and Fusion Power

    Science.gov (United States)

    1988-01-01

    The NASA Office of Exploration sponsored the NASA Lunar Helium-3 and Fusion Power Workshop. The meeting was held to understand the potential of using He-3 from the moon for terrestrial fusion power production. It provided an overview, two parallel working sessions, a review of sessions, and discussions. The lunar mining session concluded that mining, beneficiation, separation, and return of He-3 from the moon would be possible but that a large scale operation and improved technology is required. The fusion power session concluded that: (1) that He-3 offers significant, possibly compelling, advantages over fusion of tritium, principally increased reactor life, reduced radioactive wastes, and high efficiency conversion, (2) that detailed assessment of the potential of the D/He-3 fuel cycle requires more information, and (3) D/He-3 fusion may be best for commercial purposes, although D/T fusion is more near term.

  15. Helium and carbon isotopes in Indian diamonds

    Science.gov (United States)

    Wiens, R.; Lal, D.; Craig, H.

    1990-09-01

    Helium and carbon isotope measurements in Indian diamonds (from Andhra Pradesh) were carried out using samples that included mined diamonds from primary kimberlite source rocks and alluvial diamonds from river gravel. The He and C isotope concentrations in diamonds from these two sources were compared, and the Indian diamonds were compared to those from other regions. Results indicate that most of the He-3 in the alluvial diamonds is of cosmogenic origin and that the alluvial diamonds may also have a significant He-4 component due to alpha particles implanted during storage in a secondary matrix. One diamond, a mined kimberlite specimen, was found to have the lowest He-4 content (0.018 microcc/g) so far recorded in diamonds.

  16. Frequency metrology in quantum degenerate helium

    Directory of Open Access Journals (Sweden)

    Vassen Wim

    2013-08-01

    Full Text Available We have measured the absolute frequency of the 1557-nm doubly forbidden transition between the two metastable states of helium, 2 3S1 (lifetime 8000 s and 2 1S0 (lifetime 20 ms, with 1 kHz precision. With an Einstein coefficient of 10−7 s−1 this is one of weakest optical transitions ever measured. The measurement was performed in a Bose-Einstein condensate of 4He* as well as in a Degenerate Fermi Gas of 3He*, trapped in a crossed dipole trap. From the isotope shift we deduced the nuclear charge radius difference between the α-particle and the helion. Our value differs by 4σ with a very recent result obtained on the 2 3S → 2 3P transition.

  17. Absolute calibration of TFTR helium proportional counters

    Energy Technology Data Exchange (ETDEWEB)

    Strachan, J.D.; Diesso, M.; Jassby, D.; Johnson, L.; McCauley, S.; Munsat, T.; Roquemore, A.L. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Barnes, C.W. [Princeton Univ., NJ (United States). Plasma Physics Lab.]|[Los Alamos National Lab., NM (United States); Loughlin, M. [Princeton Univ., NJ (United States). Plasma Physics Lab.]|[JET Joint Undertaking, Abingdon (United Kingdom)

    1995-06-01

    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.

  18. The Zeeman effect for helium atom

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The g-factors of the 23P, 21P, and 33P states of the helium atom are calculated by using the vatiational wave functions constructed from the linear combinations of Slater-type basis sets. The relativistic corrections to order α2(a.u.) and the effect of the motion of the center of mass are treated by using first-order perturbation theory. Most of our predicted results are in good agreement with recent results of Yan and Drake, which were obtained by using the wave functions with doubled Hylleraas coordinates. Based on the analysis of the convergence pattern in our calculation, we believe that our predicted value of the δgL-factor for 33P state in 4He, 2.914 15×10-7, ought to be reasonable and accurate, although there are no corresponding experimental data available in the liteature yet to be compared with.

  19. Helium removal and transport studies in TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Hillis, D.L.; Hogan, J.T.; Horton, L.D.; Isler, R.C.; Klepper, C.C.; Mioduszewski, P.K. (Oak Ridge National Lab., TN (USA)); Finken, K.H.; Dippel, K.H.; Pospieszczyk, A.; Rusbueldt, D.; Euringer, H. (Association Euratom-Kernforschungsanlage Juelich (Germany, F.R.). Inst. fuer Plasmaphysik); Wolf, G.H.; Moyer, R.A.; Conn, R.W.; Gray, D.S. (California Univ., Los Angeles, CA (USA). Inst. of Plasma and Fusion Re

    1990-01-01

    Experiments demonstrating direct control of the He{sup 2+} density in a tokamak plasma have been performed in the TEXTOR tokamak with the Advanced Limiter Test-II pump limiter. Helium is injected in a short gas puff from the outside of the plasma, is observed to reach the plasma core, and then is readily from the plasma. Active He pumping is found to be a valuable technique for discriminating the actual He confinement time from {tau}*{sub He}, which is strongly dependent on recycling. Active charge-exchange spectroscopy is used to study the exhaust and transport of He{sup 2+} within the plasma, and the density evolution is modeled with the diffusive/convective transport code, MIST. 8 refs., 3 figs.

  20. Harmonic oscillator model for the helium atom

    CERN Document Server

    Carlsen, Martin

    2015-01-01

    A harmonic oscillator model in four dimensions is presented for the helium atom to estimate the distance to the inner and outer electron from the nucleus, the angle between electrons and the energy levels. The method is algebraic and is not based on the choice of correct trial wave function. Three harmonic oscillators and thus three quantum numbers are sufficient to describe the two-electron system. We derive a simple formula for the energy in the general case and in the special case of the Wannier Ridge. For a set of quantum numbers the distance to the electrons and the angle between the electrons are uniquely determined as the intersection between three surfaces. We show that the excited states converge either towards ionization thresholds or towards extreme parallel or antiparallel states and provide an estimate of the ground state energy.

  1. Electron impact ionization of helium isoelectronic systems

    Energy Technology Data Exchange (ETDEWEB)

    Talukder, M.R. [Rajshahi Univ., Dept. of Applied Physics and Electronic Engineering (Bangladesh)

    2008-09-15

    The electron impact single ionization cross sections, on the helium isoelectronic He, Li{sup 1+}, B{sup 3+}, C{sup 4+} N{sup 5+} O{sup 6+} Ne{sup 8+}, Na{sup 9+}. Ar{sup +16}, Fe{sup 24+}, Mo{sup 41+} Ag{sup 45+}, and U{sup 90+} targets, are calculated modifying the simplified Bell (SBELL) model [Eur. Phys. J. D 46, 281 (2008)]. The results of the present analysis are compared with the available experimental and theoretical data. The modified SBELL (MSBELL) model, incorporating the ionic correction factor in it, produces excellent agreement with the experimental data and theoretical calculations for all the two-electron systems, neutral or ions. This model may be a prudent choice in plasma modeling due to its simple inherent structure. (authors)

  2. Helium and Sulfur Hexafluoride in Musical Instruments

    Science.gov (United States)

    Forinash, Kyle; Dixon, Cory L.

    2014-11-01

    The effects of inhaled helium on the human voice were investigated in a recent article in The Physics Teacher.1 As mentioned in that article, demonstrations of the effect are a popular classroom activity. If the number of YouTube videos is any indication, the effects of sulfur hexafluoride on the human voice are equally popular. However, there appears to be little information available on the effects of either of these gases on musical instruments.2 We describe here the results of a student project that involved measuring the frequency shifts in an organ pipe, a trumpet, and a trombone as the result of filling the instruments with these two gases. The project was one of several possible end-of-semester projects required in an elective science of sound course for non-science majors.

  3. Radiative corrections to the polarizability of helium.

    Science.gov (United States)

    Łach, Grzegorz; Jeziorski, Bogumił; Szalewicz, Krzysztof

    2004-06-11

    The complete alpha(3) QED correction to the helium atom polarizability is computed assuming an infinite nuclear mass and found to be equal to 0.000030666(3) a.u., with the contribution from the electric-field dependence of the Bethe logarithm amounting to 0.000000193(2) a.u. After including the alpha(2) and alpha(3) corrections for the nuclear recoil and the leading part of the alpha(4) QED correction, we find that the molar polarizability of 4He is 0.51725419(9)(4) cm(3)/mol. The first of the two error bounds is dominated by the uncertainty of alpha(4) and higher-order QED corrections and the second reflects the uncertainty of the Avogadro constant.

  4. A Study of Confined Helium Atom

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The helium atom confined by a spherical parabolic potential well is studied employing the adiabatic hyperspherical approach method. Total energies of the ground and three low-excited states are obtained as a function of the confined potential radii. We find that the energies of a spherical parabolic potential well are in good agreement with those of an impenetrable spherical box for the larger confined potential radius. We find also that the confinement may cause accidental degeneracies between levels with different low-excited states and the inversion of the energy values. The results for the three-dimensional spherical potential well and the two-dimensional disc-like potential well are compared with each other. We find that the energy difference between states in a two-dimensional parabolic potential is also obviously larger than the corresponding levels for a spherical parabolic potential.

  5. Photoionizaton of Pure and Doped Helium Nanodroplets

    CERN Document Server

    Mudrich, M

    2014-01-01

    Helium nanodroplets, commonly regarded as the "nearly ideal spectroscopic matrix", are being actively studied for more than two decades now. While they mostly serve as cold, weakly perturbing and transparent medium for high-resolution spectroscopy of embedded molecules, their intrinsic quantum properties such as microscopic superfluidity still are subject-matter of current research. This article reviews recent work on pure and doped He nanodroplets using PI spectroscopy, an approach which has greatly advanced in the past years. While the notion of the ideal spectroscopic matrix mostly no longer holds in this context, photoionization techniques provide detailed insights into the photo-physical properties of pure and doped He nanodroplets and their relaxation dynamics following electronic excitation. Exploiting nowadays available high laser fields, even highly ionized states of matter on the nanoscale can be formed. Our particular focus lies on recent experimental progress including fs time-resolved spectroscop...

  6. Photoionization of helium dimers; Photoionisation von Heliumdimeren

    Energy Technology Data Exchange (ETDEWEB)

    Havermeier, Tilo

    2010-06-09

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

  7. Helium Inventory Management For LHC Cryogenics

    CERN Document Server

    Pyarali, Maisam

    2017-01-01

    The LHC is a 26.7 km circumference ring lined with superconducting magnets that operate at 1.9 K. These magnets are used to control the trajectory of beams of protons traveling in opposite directions and collide them at various experimental sites across the LHC where their debris is analyzed. The focus of this paper is the cryogenic system that allows the magnets to operate in their superconducting states. It aims to highlight the operating principles of helium refrigeration and liquefaction, with and without nitrogen pre-cooling; discuss the various refrigerators and liquefiers used at CERN for both LHC and Non-LHC applications, with their liquefaction capacities and purposes; and finally to deliberate the management of the LHC inventory and how it contributes to the strategic decision CERN makes regarding the inventory management during the Year-End Technical Stop (YETS), Extended Year-End Technical Stop (EYETS) and long shutdowns.

  8. Liquid Oxygen Thermodynamic Vent System Testing with Helium Pressurization

    Science.gov (United States)

    VanDresar, Neil T.

    2014-01-01

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

  9. Analytical modeling of helium turbomachinery using FORTRAN 77

    Science.gov (United States)

    Balaji, Purushotham

    Advanced Generation IV modular reactors, including Very High Temperature Reactors (VHTRs), utilize helium as the working fluid, with a potential for high efficiency power production utilizing helium turbomachinery. Helium is chemically inert and nonradioactive which makes the gas ideal for a nuclear power-plant environment where radioactive leaks are a high concern. These properties of helium gas helps to increase the safety features as well as to decrease the aging process of plant components. The lack of sufficient helium turbomachinery data has made it difficult to study the vital role played by the gas turbine components of these VHTR powered cycles. Therefore, this research work focuses on predicting the performance of helium compressors. A FORTRAN77 program is developed to simulate helium compressor operation, including surge line prediction. The resulting design point and off design performance data can be used to develop compressor map files readable by Numerical Propulsion Simulation Software (NPSS). This multi-physics simulation software that was developed for propulsion system analysis has found applications in simulating power-plant cycles.

  10. Molecular dynamics study of helium bubble pressure in titanium

    Science.gov (United States)

    Zhang, Bao-Ling; Wang, Jun; Hou, Qing

    2011-03-01

    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. Project supported by the National Natural Science Foundation of China (Grant No. 10775101) and National Magnetic Confinement Fusion Program of China (Grant No. 2009GB106004).

  11. Peppery Hot Bean Curd

    Institute of Scientific and Technical Information of China (English)

    1997-01-01

    Peppery Hot Bean Curd is a famous dish that originated in Chengdu,Sichuan Province.Dating back to the year under the reign of Emperor Tongzhi during the Qing Dynasty(1862-1875),a woman chef named Chen created this dish.In Chinese it is called Mapo Bean Curd. Ingredients:Three pieces of bean curd,100 grams lean pork,25 grams green soy beans or garlic

  12. The primordial helium abundance from updated emissivities

    Energy Technology Data Exchange (ETDEWEB)

    Aver, Erik [Department of Physics, Gonzaga University, 502 E Boone Ave, Spokane, WA, 99258 (United States); Olive, Keith A.; Skillman, Evan D. [School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN, 55455 (United States); Porter, R.L., E-mail: aver@gonzaga.edu, E-mail: olive@umn.edu, E-mail: ryanlporter@gmail.com, E-mail: skillman@astro.umn.edu [Department of Physics and Astronomy, University of Georgia, Athens, GA, 30602 (United States)

    2013-11-01

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

  13. Focused helium-ion-beam-induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Alkemade, P.F.A.; Miro, H. [Delft University of Technology, Kavli Institute of Nanoscience, Delft (Netherlands)

    2014-12-15

    The recent introduction of the helium ion microscope (HIM) offers new possibilities for materials modification and fabrication with spatial resolution below 10 nm. In particular, the specific interaction of He{sup +} ions in the tens of keV energy range with materials - i.e., minimal deflection and mainly energy loss via electronic excitations - renders the HIM a special tool for ion-beam-induced deposition. In this work, an overview is given of all studies of helium-ion-beam-induced deposition (He-IBID) that appeared in the literature before summer 2014. Continuum models that describe the deposition processes are presented in detail, with emphasis on precursor depletion and replenishment. In addition, a Monte Carlo model is discussed. Basic experimental He-IBID studies are critically examined. They show deposition rates of up to 0.1 nm{sup 3}/ion. Analysis by means of a continuum model yields the precursor diffusion constant and the cross sections for beam-induced precursor decomposition and beam-induced desorption. Moreover, it is shown that deposition takes place only in a small zone around the beam impact point. Furthermore, the characterization of deposited materials is discussed in terms of microstructure and resistivity. It is shown that He-IBID material resembles more electron-beam-induced-deposition (EBID) material than Ga-ion-beam-induced-deposition (Ga-IBID) material. Nevertheless, the spatial resolution for He-IBID is in general better than for EBID and Ga-IBID; in particular, proximity effects are minimal. (orig.)

  14. STIRAP on helium: Excitation to Rydberg states

    Science.gov (United States)

    Yuan, Deqian

    Research in optically induced transitions between dierent atomic levels has a long history. For transitions between states driven by a coherent optical eld, the theoretical eciency could be ideally high as 100% but there could be many factors preventing this. In the three state helium atom excitation process, i.e. 23S→33P→nL , the stimulated emission from intermediate state makes it hard to achieve ecient population transfer to the nal state through an intuitive excitation order. One technique to achieve a higher eciency is Stimulated Raman Adiabatic Passage (STIRAP) which is being studied and under research in our lab. Unlike traditional three level excitation processes, STIRAP actually uses a counter intuitive pulsed laser beams timing arrangement. The excitation objects are metastable helium atoms traveling in a vacuum system with a longitudinal velocity of ~ 1070 m/s. We are using a 389 nm UV laser to connect the 23S and the 33P state and a frequency tunable ~790 nm IR laser to connect the 33P state and the dierent Rydberg states. A third 1083 nm wavelength laser beam drives the 23S → 23P transition to transversely separate the residual metastable atoms and the Rydberg atoms for eciency measurements. The data is taken by a stainless steel detector in the vacuum system. As the Rydberg atoms will get ionized by blackbody radiation under room temperature, we can utilize this for their detection. An ion detector sitting on the eld plate is capable to collect the ion signals of the Rydberg atoms for detection. So far the whole system has not been ready for data collection and measurement, so here we are using data and results from previous theses for discussions. The highest transition frequency that has ever been achieved in our lab is around 70% after corrections.

  15. Solar Hot Water Heater

    Science.gov (United States)

    1978-01-01

    The solar panels pictured below, mounted on a Moscow, Idaho home, are part of a domestic hot water heating system capable of providing up to 100 percent of home or small business hot water needs. Produced by Lennox Industries Inc., Marshalltown, Iowa, the panels are commercial versions of a collector co-developed by NASA. In an effort to conserve energy, NASA has installed solar collectors at a number of its own facilities and is conducting research to develop the most efficient systems. Lewis Research Center teamed with Honeywell Inc., Minneapolis, Minnesota to develop the flat plate collector shown. Key to the collector's efficiency is black chrome coating on the plate developed for use on spacecraft solar cells, the coating prevents sun heat from "reradiating," or escaping outward. The design proved the most effective heat absorber among 23 different types of collectors evaluated in a Lewis test program. The Lennox solar domestic hot water heating system has three main components: the array of collectors, a "solar module" (blue unit pictured) and a conventional water heater. A fluid-ethylene glycol and water-is circulated through the collectors to absorb solar heat. The fluid is then piped to a double-walled jacket around a water tank within the solar module.

  16. Jupiter's Hot, Mushy Moon

    Science.gov (United States)

    Taylor, G. Jeffrey

    2003-01-01

    Jupiter's moon Io is the most volcanically active body in the Solar System. Observations by instruments on the Galileo spacecraft and on telescopes atop Mauna Kea in Hawai'i indicate that lava flows on Io are surprisingly hot, over 1200 oC and possibly as much as 1300 oC; a few areas might have lava flows as hot as 1500 oC. Such high temperatures imply that the lava flows are composed of rock that formed by a very large amount of melting of Io's mantle. This has led Laszlo Keszthelyi and Alfred S. McEwen of the University of Arizona and me to reawaken an old hypothesis that suggests that the interior of Io is a partially-molten mush of crystals and magma. The idea, which had fallen out of favor for a decade or two, explains high-temperature hot spots, mountains, calderas, and volcanic plains on Io. If correct, Io gives us an opportunity to study processes that operate in huge, global magma systems, which scientists believe were important during the early history of the Moon and Earth, and possibly other planetary bodies as well. Though far from proven, the idea that Io has a ocean of mushy magma beneath its crust can be tested with measurements by future spacecraft.

  17. Contribution to the study of the evolution of radiation induced He in Be O; Etudes sur l'evolution de l'helium produit par reactions nucleaires dans l'oxyde de beryllium

    Energy Technology Data Exchange (ETDEWEB)

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

    1966-11-15

    The purpose of this work in-pile investigation of He formed by (n, 2n) and (n, {alpha}) nuclear reactions, released from irradiated BeO, in the temperature range 1000 - 1350 deg. C. The experimental results show that, for an instantaneous neutron fast flux of 10{sup 13} n cm{sup -2} sec{sup -1}, an equilibrium is attempted, after several days, for a part lower than 20 per cent of the quantity of He formed, theoretically calculated from the neutron cross sections of nuclear reactions, and from the analytical form of the neutron fast flux, releases from the solid. The validity of the values of calculated helium and the gas chromatographic analytical method are also verified by dissolution of the BeO pellets in cryolite. A new fast neutron flux measuring method may be so defined. The discussion of the experimental results enables to establish that the processus of He release is characterized by two phenomena: the first one which controls the release of He atoms out of the solid and the second which reveals a capture processus, connected to the irradiation and probably due to the vacancies induced in the lattice. (author) [French] On etudie en pile le degagement de l'helium forme par reactions nucleaires (n, 2 n) et (n, {alpha}) dans l'oxyde de beryllium irradie entre 1000 et 1350 deg. C. Les resultats experimentaux montrant que, pour un flux rapide instantane de 10{sup 13} n{sub r} cm{sup -2} s{sup -1}, on aboutit, au bout de quelques jours, a un etat d'equilibre pour lequel une partie, inferieure a 20 pour cent de la quantite d'helium forme, calculee theoriquement a partir des sections efficaces des reactions nucleaires et de la forme analytique du flux rapide, s'echappe du solide. On verifie egalement par dissolution des echantillons de BeO dans la cryolithe la validite du calcul de l'helium et de la methode de dosage par chromatographie en phase gazeuse. On peut ainsi definir une methode nouvelle de mesure des flux rapides. La

  18. Nucleation, solvation and boiling of helium excimer clusters

    CERN Document Server

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

    2015-01-01

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

  19. Method for laser spectroscopy of metastable pionic helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Hori, M., E-mail: Masaki.Hori@mpq.mpg.de; Sótér, A.; Aghai-Khozani, H. [Max-Planck-Institut für Quantenoptik (Germany); Barna, D. [CERN (Switzerland); Dax, A. [Paul Scherrer Institut (Switzerland); Hayano, R. S.; Murakami, Y.; Yamada, H. [University of Tokyo, Department of Physics (Japan)

    2015-08-15

    The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic helium atoms using the high-intensity π{sup −} beam of the ring cyclotron facility of the Paul Scherrer Institute. These atoms are heretofore hypothetical three-body Coulomb systems each composed of a helium nucleus, a π{sup −} occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic helium atoms at CERN.

  20. Solvation of Na+, K+, and Their Dimers in Helium

    OpenAIRE

    An der Lan, Lukas; Bartl, Peter; Leidlmair, Christian; Jochum, Roland; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2012-01-01

    Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so-called snowballs. Calculations suggest that helium atoms in the first solvation layer of these snowballs form rigid structures and that their number (n) is well defined, especially for the lighter alkalis. However, experiments have so far failed to accurately determine values of n. We present high-resolution mass spectra of Na+He n , K+He n , Na2 +He n and K2 +He n , formed by electron ionization of do...

  1. Roles and expectations of cold compressor for helium refrigerator

    Energy Technology Data Exchange (ETDEWEB)

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

    2002-12-01

    Since around 1970, cryogenic systems have required the use of cold compressors. The requirement appeared for two reasons. The first was reduce the pressure of liquid helium with the intention of realizing the stable operation of large superconducting magnets with the best superconducting ability by decreasing operating temperature. The other was to improve the reliability of helium refrigerator compressors by introducing a turbo-compressor with oil-free bearings. This paper describes the circumstances and particular development of cold compressors, requirements related to helium refrigeration systems and cold compressors and future prospects. (author)

  2. Helium at White Dwarf Photospheric Conditions: Preliminary Laboratory Results

    Science.gov (United States)

    Schaeuble, M.; Falcon, R. E.; Gomez, T. A.; Winget, D. E.; Montgomery, M. H.; Bailey, J. E.

    2017-03-01

    We present preliminary results of an experimental study exploring helium at photospheric conditions of white dwarf stars. These data were collected at Sandia National Laboratories' Z-machine, the largest x-ray source on earth. Our helium results could have many applications ranging from validating current DB white dwarf model atmospheres to providing accurate He pressure shifts at varying temperatures and densities. In a much broader context, these helium data can be used to guide theoretical developments in new continuum-lowering models for two-electron atoms. We also discuss future applications of our updated experimental design, which enables us to sample a greater range of densities, temperatures, and gas compositions.

  3. Multi-objective Optimization on Helium Liquefier Using Genetic Algorithm

    Science.gov (United States)

    Wang, H. R.; Xiong, L. Y.; Peng, N.; Meng, Y. R.; Liu, L. Q.

    2017-02-01

    Research on optimization of helium liquefier is limited at home and abroad, and most of the optimization is single-objective based on Collins cycle. In this paper, a multi-objective optimization is conducted using genetic algorithm (GA) on the 40 L/h helium liquefier developed by Technical Institute of Physics and Chemistry of the Chinese Academy of Science (TIPC, CAS), steady solutions are obtained in the end. In addition, the exergy loss of the optimized system is studied in the case of with and without liquid nitrogen pre-cooling. The results have guiding significance for the future design of large helium liquefier.

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

    Science.gov (United States)

    Shiibayashi, Masao; Izunaga, Yasushi; Sado, Shintaro

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

  5. 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).

  6. European standardization activities on safety of liquid helium cryostats

    CERN Document Server

    CERN. Geneva

    2016-01-01

    This talk gives a general overview on the challenges of designing safety units for liquid helium cryostats with regard to existing industry standards. It reviews the work of a national working group that published the technical guideline DIN SPEC 4683 in April 2015, which is dedicated to the particular conditions in liquid helium cryostats. Based on both this guideline and equivalent documents from e.g. CEA, CERN, a working group is being formed at the European Committee for Standardization, associated to CEN/TC 268, which will work on a European standard on safety of liquid helium cryostats. The actual status and the schedule of this project are presented.

  7. Superfluid Helium On-Orbit Transfer (SHOOT) operations

    Science.gov (United States)

    Kittel, P.; Dipirro, M. J.

    1989-01-01

    The in-flight tests and the operational sequences of the Superfluid Helium On-Orbit Transfer (SHOOT) experiment are outlined. These tests include the transfer of superfluid helium at a variety of rates, the transfer into cold and warm receivers, the operation of an extravehicular activity coupling, and tests of a liquid acquisition device. A variety of different types of instrumentation will be required for these tests. These include pressure sensors and liquid flow meters that must operate in liquid helium, accurate thermometry, two types of quantity gauges, and liquid-vapor sensors.

  8. Helium at white dwarf photospheric conditions: preliminary laboratory results

    CERN Document Server

    Schaeuble, Marc; Gomez, Thomas A; Winget, Don E; Montgomery, Michael H; Bailey, James E

    2016-01-01

    We present preliminary results of an experimental study exploring helium at photospheric conditions of white dwarf stars. These data were collected at Sandia National Laboratories' Z-machine, the largest x-ray source on earth. Our helium results could have many applications ranging from validating current DB white dwarf model atmospheres to providing accurate He pressure shifts at varying temperatures and densities. In a much broader context, these helium data can be used to guide theoretical developments in new continuum-lowering models for two-electron atoms. We also discuss future applications of our updated experimental design, which enables us to sample a greater range of densities, temperatures, and gas compositions.

  9. International thermodynamic tables of the fluid state helium-4

    CERN Document Server

    Angus, S; McCarty, R D

    2013-01-01

    International Thermodynamic Tables of the Fluid State Helium-4 presents the IUPAC Thermodynamic Tables for the thermodynamic properties of helium. The IUPAC Thermodynamic Tables Project has therefore encouraged the critical analysis of the available thermodynamic measurements for helium and their synthesis into tables. This book is divided into three chapters. The first chapter discusses the experimental results and compares with the equations used to generate the tables. These equations are supplemented by a vapor pressure equation, which represents the 1958 He-4 scale of temperature that is

  10. Mesure Objective De L'attenuation et De L'effet D'occlusion Des Protecteurs Auditifs a Partir Des Potentiels Evoques Stationnaires et Multiples =

    Science.gov (United States)

    Valentin, Olivier

    Selon l'Organisation mondiale de la sante, le nombre de travailleurs exposes quotidiennement a des niveaux de bruit prejudiciables a leur audition est passe de 120 millions en 1995 a 250 millions en 2004. Meme si la reduction du bruit a la source devrait etre toujours privilegiee, la solution largement utilisee pour lutter contre le bruit au travail reste la protection auditive individuelle. Malheureusement, le port des protecteurs auditifs n'est pas toujours respecte par les travailleurs car il est difficile de fournir un protecteur auditif dont le niveau d'attenuation effective est approprie a l'environnement de travail d'un individu. D'autre part, l'occlusion du canal auditif induit une modification de la perception de la parole, ce qui cree un inconfort incitant les travailleurs a retirer leurs protecteurs. Ces deux problemes existent parce que les methodes actuelles de mesure de l'effet d'occlusion et de l'attenuation sont limitees. Les mesures objectives basees sur des mesures microphoniques intra-auriculaires ne tiennent pas compte de la transmission directe du son a la cochlee par conduction osseuse. Les mesures subjectives au seuil de l'audition sont biaisees a cause de l'effet de masquage aux basses frequences induit par le bruit physiologique. L'objectif principal de ce travail de these de doctorat est d'ameliorer la mesure de l'attenuation et de l'effet d'occlusion des protecteurs auditifs intra-auriculaires. L'approche generale consiste a : (i) verifier s'il est possible de mesurer l'attenuation des protecteurs auditifs grâce au recueil des potentiels evoques stationnaires et multiples (PEASM) avec et sans protecteur auditif (protocole 1), (ii) adapter cette methodologie pour mesurer l'effet d'occlusion induit par le port de protecteur auditifs intra-auriculaires (protocole 2), et (iii) valider chaque protocole par l'intermediaire de mesures realisees sur sujets humains. Les resultats du protocole 1 demontrent que les PEASM peuvent etre utilises pour

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

    Science.gov (United States)

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

    2011-01-01

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

  12. PREFACE: Hot Quarks 2004

    Science.gov (United States)

    Antinori, Federico; Bass, Steffen A.; Bellwied, Rene; Ullrich, Thomas; Velkovska, Julia; Wiedemann, Urs

    2005-04-01

    Why another conference devoted to ultra-relativistic heavy-ion physics? As we looked around the landscape of the existing international conferences and workshops, we realized that there was not a single one tailored to the people who are most directly involved with the actual research work: students, post-docs, and junior faculty/research scientists. Of course there are schools, but that was not what we had in mind. We wanted a meeting where young researchers could come together to discuss in depth the physics that they are working on without any hindrance. The major conferences have very limited time for discussions which is often shared amongst the most established. This leaves little room for young people to ask their questions and to get the detailed feedback which they deserve and which satisfies their curiosity. A discussion-driven workshop, centering on those without whom there will be no future—that seemed like what was needed. And thus the Hot Quarks workshop was born. The aim of Hot Quarks was to enhance the direct exchange of scientific information among the younger members of the community, from both experiment and theory. Participation was by invitation only in order to emphasize the contributions from junior researchers. This approach makes the workshop unique among the many forums in the field. For young scientists it represented an opportunity for exposure that they would not have had in one of the major conferences. The hope is that this meeting has helped to stimulate the next generation of scientists in our field and, at the same time, strengthened their sense of community. It all came together from 18 24 July 2004, when the 77 participants met at The Inn at Snakedance in the Taos Ski Valley, New Mexico, USA, for the first Hot Quarks workshop. Photograph Participants gather in the sunshine at the foot of the Taos Ski Valley chairlift. By all accounts, Hot Quarks 2004 was a great success. Every participant had the opportunity to present her or

  13. Dielectric breakdown properties of hot SF6/He mixtures predicted from basic data

    Science.gov (United States)

    Wang, Weizong; Tu, Xin; Mei, Danhua; Rong, Mingzhe

    2013-11-01

    Sulfur hexafluoride (SF6) gas has a quite high global warming potential and hence it is required that applying any substitute for SF6 gas. Much interest in the use of a mixture of helium and SF6 as arc quenching medium was investigated indicating a higher recovery performance of arc interruption than that of pure SF6. It is known that the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown relies on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF6/He mixtures related to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The critically reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. Good agreement was found between calculations for pure hot SF6 and pure hot He and experimental results and previous calculations. The addition of He to SF6 was found to decrease the critical reduced electric field strength in the whole temperature range due to a lack of electron impact attachment process for helium regardless its high ionization potential. This indicates that not the behaviour of dielectric strength but possibly the higher energy dissipation capability caused mainly by light mass and high specific heat as well as thermal conductivity of atomic helium contributes most to a higher dielectric recovery performance of arc interruption for SF6/He mixtures.

  14. The effects of He I 10830 on helium abundance determinations

    CERN Document Server

    Aver, Erik; Skillman, Evan D

    2015-01-01

    Observations of helium and hydrogen emission lines from metal-poor extragalactic H II regions provide an independent method for determining the primordial helium abundance, Y_p. Traditionally, the emission lines employed are in the visible wavelength range, and the number of suitable lines is limited. Furthermore, when using these lines, large systematic uncertainties in helium abundance determinations arise due to the degeneracy of physical parameters, such as temperature and density. Recently, Izotov, Thuan, & Guseva (2014) have pioneered adding the He 10830 infrared emission line in helium abundance determinations. The strong electron density dependence of He 10830 makes it ideal for better constraining density, potentially breaking the degeneracy with temperature. We revisit our analysis of the dataset published by Izotov, Thuan, & Stasinska (2007) and incorporate the newly available observations of He 10830 by scaling them using the observed-to-theoretical Paschen-gamma ratio. The solutions are b...

  15. Heat transfer to near-critical helium in horizontal channels

    Energy Technology Data Exchange (ETDEWEB)

    Dolgoy, M.L.; Kirichenko, Y.A.; Sklovsky, Y.B.; Troyanov, A.M.; Chernyakov, P.S. (AN Ukrainskoj SSR, Kharkov. Fiziko-Tekhnicheskij Inst. Nizkikh Temperatur)

    1983-03-01

    Experimental results on heat transfer and pressure losses during a forced motion of helium of near-critical state parameters in a horizontal channel are reported. A method of calculation of temperature and pressure distributions along the channel is proposed.

  16. Development of helium refrigeration/ liquefaction system at BARC, India

    Science.gov (United States)

    Ansari, N. A.; Goyal, M.; Chakravarty, A.; Menon, Rajendran S.; Jadhav, M.; Rane Nair, T., Sr.; Kumar, J.; Kumar, N.; Bharti, SK; Chakravarty, Abhilash; Jain, A.; Joemon, V.

    2017-02-01

    An experimental helium refrigerator/liquefier, using ultra high speed cryogenic turboexpanders, is designed and developed at Cryo-Technology Division, BARC. The developed system is based on the modified Claude cycle. The developed system is presently fully functional consisting of process compressor with gas management system, coldbox, helium receiver Dewar, tri-axial transfer line and helium recovery system. Extended trial runs are conducted to evaluate the performance of the developed system. During these trials, liquefaction rate of around 32 l/hr and refrigeration capacity of around 190W is achieved. The paper addresses design, development and commissioning aspects of the developed helium liquefier along with results of performance evaluation trial runs.

  17. Gaseous Helium Reclamation at Rocket Test Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The ability to restore large amounts of vented gaseous helium (GHe) at rocket test sites preserves the GHe and reduces operating cost. The used GHe is vented into...

  18. Heat capacity and thermal expansion of water and helium

    Science.gov (United States)

    Putintsev, N. M.; Putintsev, D. N.

    2017-04-01

    Original expressions for heat capacity CV and its components, vibrational and configurational components of thermal expansion coefficient were established. The values of CV, Cvib, Cconf, αvib and αconf for water and helium 4He were calculated.

  19. Self-Calibrating Vector Helium Magnetometer (SVHM) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase 2 SBIR proposal describes the design, fabrication and calibration of a brass-board Self-Calibrating Vector Helium Magnetometer (SVHM). The SVHM instrument...

  20. Formation and properties of metal clusters isolated in helium droplets.

    Science.gov (United States)

    Tiggesbäumker, Josef; Stienkemeier, Frank

    2007-09-14

    The unique conditions forming atomic and molecular complexes and clusters using superfluid helium nanodroplets have opened up an innovative route for studying the physical and chemical properties of matter on the nanoscale. This review summarizes the specific characteristics of the formation of atomic clusters partly generated far from equilibrium in the helium environment. Special emphasis is on the optical response, electronic properties as well as dynamical processes which are mostly affected by the surrounding quantum matrix. Experiments include the optical induced response of isolated cluster systems in helium under quite different excitation conditions ranging from the linear regime up to the violent interaction with a strong laser field leading to Coulomb explosion and the generation of highly charged atomic fragments. The variety of results on the outstanding properties in the quantum size regime highlights the peculiar capabilities of helium nanodroplet isolation spectroscopy.

  1. Helium-3 Microscopic Optical Model Potential Based on Skyrme Interaction

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    <正>The helium-3 microscopic optical potential is obtained by Green function method through nuclear matter approximation and local density approximation based on the effective Skyrme interaction. The reaction cross

  2. Simulation study of radiation damage induced by energetic helium nuclei

    CERN Document Server

    Hoang Dac Luc; Hoang Dac Dat

    2003-01-01

    High energy alpha particles produced by neutron-induced nuclear reactions can damage severely reactor materials. Simulation of this process is described using theoretical calculation and ion irradiation experiments at different displacement doses and Helium doses.

  3. Communication: Barium ions and helium nanodroplets: solvation and desolvation.

    Science.gov (United States)

    Zhang, Xiaohang; Drabbels, Marcel

    2012-08-07

    The solvation of Ba(+) ions created by the photoionization of barium atoms located on the surface of helium nanodroplets has been investigated. The excitation spectra corresponding to the 6p (2)P(1/2) ← 6s (2)S(1/2) and 6p (2)P(3/2) ← 6s (2)S(1/2) transitions of Ba(+) are found to be identical to those recorded in bulk He II [H. J. Reyher, H. Bauer, C. Huber, R. Mayer, A. Schafer, and A. Winnacker, Phys. Lett. A 115, 238 (1986)], indicating that the ions formed at the surface of the helium droplets become fully solvated by the helium. Time-of-flight mass spectra suggest that following the excitation of the solvated Ba(+) ions, these are being ejected from the helium droplets either as bare Ba(+) ions or as small Ba(+)He(n) (n < 20) complexes.

  4. Gaseous Helium Reclamation at Rocket Test Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — GHe reclamation is critical in reducing operating costs at rocket engine test facilities. Increases in cost and shortages of helium will dramatically impact testing...

  5. One of the Helium Liquifiers in the North Area

    CERN Multimedia

    1979-01-01

    Several Helium Liquifiers were installed in the North Area to cool superconducting magnets used in the experiments. At center top is M.Dykes, at bottom right J.Dozio. See CERN Annual Report 1979 p.82.

  6. Transport and extraction of radioactive ions stopped in superfluid helium

    CERN Document Server

    Huang Wan Xia; Gloos, K; Takahashi, N; Arutyunov, K; Pekola, J P; Äystö, J

    2003-01-01

    A new approach to convert a high energy beam to a low energy one, which is essential for the next generation radioactive ion beam facilities, has been proposed and tested at Jyvaeskylae, Finland. An open sup 2 sup 2 sup 3 Ra alpha-decay-recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling sup 2 sup 1 sup 9 Rn ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface was possible thanks to the high sensitivity of radioactivity detection. An efficiency of 36% was obtained for the ion extraction out of liquid helium.

  7. General mechanism for helium blistering involving displaced atom transport

    Energy Technology Data Exchange (ETDEWEB)

    McDonell, W.R.

    1979-01-01

    A mechanism developed to account for formation of vertically elongated blisters in high displacement environments produced by /sup 252/Cf alpha particles and fission fragments has been extended to formation of done-shaped blisters in the low displacement environments produced by simple helium ion beams. In this mechanism, transport of displaced atoms to relieve compressive stresses in the helium-implanted layer allows interconnections of small, subsurface bubbles to form the blister cavity. The same transport may cause thickening of the blister caps at low implantation energies. The transition from dome-shaped to vertically elongated blistering occurs between the 300 and 3000 displacements per helium atom produced by simple helium ions and /sup 252/Cf radiations respectively.

  8. On the role of helium molecules in atmospheric pressure discharges

    Science.gov (United States)

    Carbone, Emile; Schregel, Christian; Luggenhölscher, Dirk; Czarnetzki, Uwe

    2016-09-01

    Despite their intrinsic simplicity, helium plasma kinetics are still not fully understood and quantitatively described. This is particularly the case at high pressures when various molecular helium species (i.e. ions, excimer(s) and Rydberg states) are formed. In this contribution, the absolute density of helium Rydberg molecules is measured for the first time by a combination of laser photo-ionization and Thomson scattering experiments. The experiments are performed on a parallel plate, nanosecond pulsed, DC discharge at 700 mbar. The results are combined with electron and helium metastable densities measurements and compared with a kinetic model of the discharge. The source of He2 molecules in the discharge and afterglow phases are identified and discussed. The present experimental data and kinetic model solve several inconsistencies between reaction paths proposed in the literature.

  9. Turbine flowmeter for liquid helium with the rotor magnetically levitated

    Science.gov (United States)

    Rivetti, A.; Martini, G.; Goria, R.; Lorefice, S.

    A turbine flowmeter with no mechanical contact between rotor and body is described, to be used as a reference standard in our liquid helium flow rate calibration facility. The absence of contact, zeroing the bearings friction factor, ensures a good measurement repeatability, even at very low liquid helium flow rate values. The rotor is magnetically suspended by the Meissner effect: at liquid helium temperatures two magnetic fields generate sustaining forces against the surface of the two rotor ends, which are made of niobium. Due to the repulsive nature of the acting forces, the rotor equilibrium is intrinsically stable and no external electronics are required for its levitation. A particular configuration of the superconducting windings and of the rotor ends allow the rotor to levitate and hold good axial and radial stability. A detailed description of the solutions adopted for the realization of the prototype and the operation conditions are reported. The first results, made with the absolute liquid helium calibration facility, are shown.

  10. Self-Calibrating Vector Helium Magnetometer (SVHM) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR proposal describes proposed development of a conceptual design for a Self-Calibrating Vector Helium Magnetometer (SVHM) for design and fabrication...

  11. Study of Thermal Desorption of Helium from Hydrogenated Zirconium

    Institute of Scientific and Technical Information of China (English)

    SUN Wei-Ming; WEI Yu-Cheng; SHI Li-Qun

    2006-01-01

    @@ A new method prepared for helium and hydrogen co-containing Zr films is presented to simulate aging metal tritides, in which direct current magnetron sputtering with a He/H/Ar mixture is used. The retained amount and depth profiles of helium and hydrogen are determined by elastic recoil detection analysis. Thermal desorption spectrometry is applied to investigate He thermal release and the effect of hydrogen. It is found that the hightemperature peaks with a large mount of helium release obviously shifted toward lower temperature at high hydrogen concentration, especially at the hydride transformation region, and that the shapes of the release peaks also changed due to the additional hydrogen. However, at the low-temperature releasing region the peak intense decreases when phase transformation takes place. The mechanism of helium thermal release and the effect of hydrogen are also discussed.

  12. High-Range Scalar Helium Magnetometer (HSHM) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I proposal describes development of a conceptual design for a High-range Scalar Helium Magnetometer (HSHM) for the field range +/-16 Gauss. The HSHM...

  13. The U.S. Geological Survey National Helium Resource Assessment

    Science.gov (United States)

    Brennan, S. T.; East, J. A., II

    2015-12-01

    In 2013, the U.S. Congress passed legislation directing the U.S. Geological Survey (USGS) to complete a national assessment of subsurface helium gas resources. As part of this assessment, the USGS has constructed a database of helium concentration from compositional analyses of produced gas. Though most data of this data is non-proprietary, helium data have been taken from both public and proprietary sources, with a majority taken from the USGS geochemical database (http://energy.usgs.gov/GeochemistryGeophysics/GeochemistryLaboratories/GeochemistryLaboratories-GeochemistryDatabase.aspx#4413382-introduction) and from the U.S. Bureau of Land Management (BLM) natural gas database. Altogether, there are over 16,000 analyses of natural gas composition compiled. In order to complete the assessment, it was necessary to correlate the well data with geologic reservoir data so that the helium concentrations could be compared with the reservoir and field-level gas production, in place gas volumes, and gas recovery factors. The well data from the compiled database were initially cross-referenced with the proprietary IHS Inc. well database, where possible. The results of that effort were then cross-referenced with three additional databases: the proprietary NRG Associates database of significant oil and gas fields of the United States, the non-proprietary U.S. Department of Energy's gas information system (GASIS), and an internal BLM reservoir and field database. These field and reservoir databases provide the data needed to estimate the in-place helium resources for fields with economic concentrations of helium. In order for helium production to be economic, the gas produced from geologic reservoirs must be greater than 0.3 mole percent (mol%), or in the case of liquefied natural gas processing, greater than 0.04 mol%. The field and reservoir specific estimates of total gas in place volumes, gas recovery factors, and helium concentrations, can be used as inputs for a

  14. Hot bitumen grouting rediscovered

    Energy Technology Data Exchange (ETDEWEB)

    Naudts, A. [ECO Grouting Specialists, Grand Valley, ON (Canada)

    2001-10-01

    The article extols the value of hot bitumen grouting, in conjunction with cement-based grout, as a fast, safe, environmentally-friendly and cost-effective sealant. A major advantage of bitumen grout is that blown bitumen will never wash out. The article discusses the properties and some applications of bitumen grout. A diagram shows an application of bitumen and cement-based grout at a large dam. Examples of preventing water flow in dams, in a coal mine and in a potash mine are also given.

  15. Evaluation of US demo helium-cooled blanket options

    Energy Technology Data Exchange (ETDEWEB)

    Wong, C.P.C.; McQuillan, B.W.; Schleicher, R.W. [and others

    1995-10-01

    A He-V-Li blanket design was developed as a candidate for the U.S. fusion demonstration power plant. This paper presents an 18 MPa helium-cooled, lithium breeder, V-alloy design that can be coupled to the Brayton cycle with a gross efficiency of 46%. The critical issue of designing to high gas pressure and the compatibility between helium impurities and V-alloy are addressed.

  16. Helium segregation on surfaces of plasma-exposed tungsten.

    Science.gov (United States)

    Maroudas, Dimitrios; Blondel, Sophie; Hu, Lin; Hammond, Karl D; Wirth, Brian D

    2016-02-17

    We report a hierarchical multi-scale modeling study of implanted helium segregation on surfaces of tungsten, considered as a plasma facing component in nuclear fusion reactors. We employ a hierarchy of atomic-scale simulations based on a reliable interatomic interaction potential, including molecular-statics simulations to understand the origin of helium surface segregation, targeted molecular-dynamics (MD) simulations of near-surface cluster reactions, and large-scale MD simulations of implanted helium evolution in plasma-exposed tungsten. We find that small, mobile He n (1⩽  n  ⩽  7) clusters in the near-surface region are attracted to the surface due to an elastic interaction force that provides the thermodynamic driving force for surface segregation. This elastic interaction force induces drift fluxes of these mobile He n clusters, which increase substantially as the migrating clusters approach the surface, facilitating helium segregation on the surface. Moreover, the clusters' drift toward the surface enables cluster reactions, most importantly trap mutation, in the near-surface region at rates much higher than in the bulk material. These near-surface cluster dynamics have significant effects on the surface morphology, near-surface defect structures, and the amount of helium retained in the material upon plasma exposure. We integrate the findings of such atomic-scale simulations into a properly parameterized and validated spatially dependent, continuum-scale reaction-diffusion cluster dynamics model, capable of predicting implanted helium evolution, surface segregation, and its near-surface effects in tungsten. This cluster-dynamics model sets the stage for development of fully atomistically informed coarse-grained models for computationally efficient simulation predictions of helium surface segregation, as well as helium retention and surface morphological evolution, toward optimal design of plasma facing components.

  17. Wave packet dynamics of potassium dimers attached to helium nanodroplets

    OpenAIRE

    Claas, P.; Droppelmann, G.; Schulz, C. P.; Mudrich, M.; Stienkemeier, F.

    2006-01-01

    The dynamics of vibrational wave packets excited in K$_2$ dimers attached to superfluid helium nanodroplets is investigated by means of femtosecond pump-probe spectroscopy. The employed resonant three-photon-ionization scheme is studied in a wide wavelength range and different pathways leading to K$^+_2$-formation are identified. While the wave packet dynamics of the electronic ground state is not influenced by the helium environment, perturbations of the electronically excited states are obs...

  18. Helium Controller%Helium系列处理器

    Institute of Scientific and Technical Information of China (English)

    刘坛春; 石冰心

    2002-01-01

    @@ Helium系列处理器是Virata公司(现在是GlobespanVirata)的通信处理器,主要为针对宽频调制解调器、桥接器与住宅路由器在不同价格、效能与产品特性上的市场需求,主要有He-liuml00,Helium200,Helium210-80.

  19. Corrections to the Nonrelativistic Ground Energy of a Helium Atom

    Institute of Scientific and Technical Information of China (English)

    段一士; 刘玉孝; 张丽杰

    2004-01-01

    Considering the nuclear motion, we present the nonrelativistic ground energy of a helium atom by using a simple effective variational wavefunction with a flexible parameter k. Based on the result, the relativistic and radiative corrections to the nonrelativistic Hamiltonian are discussed. The high precision value of the helium ground energy is evaluated to be -2.90338 a.u. With the relative error 0.00034%.

  20. Density shift and broadening of transition lines in antiprotonic helium

    Science.gov (United States)

    Bakalov; Jeziorski; Korona; Szalewicz; Tchoukova

    2000-03-13

    The density shift and broadening of the transition lines of antiprotonic helium have been evaluated in the impact approximation using an interatomic potential calculated ab initio with the symmetry-adapted perturbation theory. The results help to remove an uncertainty of up to 10 ppm in the laser spectroscopy data on antiprotonic helium and are of importance in experimental tests of bound state QED and CPT invariance.

  1. Formation of the helium extreme-UV resonance lines

    Science.gov (United States)

    Golding, T. P.; Leenaarts, J.; Carlsson, M.

    2017-01-01

    Context. While classical models successfully reproduce intensities of many transition region lines, they predict helium extreme-UV (EUV) line intensities roughly an order of magnitude lower than the observed value. Aims: Our aim is to determine the relevant formation mechanism(s) of the helium EUV resonance lines capable of explaining the high intensities under quiet Sun conditions. Methods: We synthesised and studied the emergent spectra from a 3D radiation-magnetohydrodynamics simulation model. The effects of coronal illumination and non-equilibrium ionisation of hydrogen and helium are included self-consistently in the numerical simulation. Results: Radiative transfer calculations result in helium EUV line intensities that are an order of magnitude larger than the intensities calculated under the classical assumptions. The enhanced intensity of He iλ584 is primarily caused by He ii recombination cascades. The enhanced intensity of He iiλ304 and He iiλ256 is caused primarily by non-equilibrium helium ionisation. Conclusions: The analysis shows that the long standing problem of the high helium EUV line intensities disappears when taking into account optically thick radiative transfer and non-equilibrium ionisation effects.

  2. Cryocooled Facilities for Superconducting Coils Testing in Gaseous Helium

    Science.gov (United States)

    Naumov, A. V.; Keilin, V. E.; Kovalev, I. A.; Surin, M. I.; Shcherbakov, V. I.; Shevchenko, S. A.; Ilin, A. A.

    Two superconducting coil test facilities equipped by Sumitomo SRDK-415D cryocoolers were developed, manufactured and tested. The motivation for their constructing was to make cheaper the testing (and especially training of LTS magnets) by liquid helium (LHe) saving. It is well known that the helium price increases rapidly and this tendency most probably will continue for a long time, as the demand of helium grows faster than its production. The utilization of heat-exchange gas considerably reduces many problems, that arise in the design of completely dry LTS magnets. The goal was to decrease or even completely avoid the consumption of rather expensive liquid helium for testing the laboratory size Nb-Ti and Nb3Sn coils including their training process. Several superconducting magnets were tested by using these facilities. For example, the first facility was successfully used for testing of 13 T, 60 kg coil cooled by cryocooler in helium gas (several torr pressure) heat exchange atmosphere. The precooling time was about 45 hours. The quench current (240 A at 4.2 K) was equal to that reached in the pool boiling LHe cryostat. The second facility with 420 mm wide access bore can be used for testing of corresponding size superconducting coils with very modest consumption of liquid helium with its level well below the lower flange of the coil. Each test facility is equipped by 2 pairs of HTS current leads. Design and operational experience of one of them is described.

  3. Suspension of superfluid helium using cesium-coated surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Williams, M.C.; Giese, C.F.; Halley, J.W. [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    1996-03-01

    We report results of an experiment which demonstrates that a layer of superfluid helium can be suspended over a cesium-coated orifice. By measuring the layer thickness with a capacitance bridge, we have shown in two runs that fluid layers up to 2 mm thick were suspended over a 70-{mu}m-diam cesium-coated orifice in a platinum foil for over 2 h in a cryostat held at 1.2 K. The effect depends on the recently established fact that superfluid helium does not wet cesium-coated surfaces. As a consequence, superfluid helium is expected to form a stable meniscus across such a cesium-coated hole. The observed depths of suspended helium are consistent with a simple theoretical model based on this picture. We briefly discuss the possible application of this method to the performance of a proposed experiment to study quantum coherence in superfluid helium by directing pulsed beams of helium atoms at such a suspended layer of fluid. {copyright} {ital 1996 The American Physical Society.}

  4. Atomistic simulation of helium bubble nucleation in palladium

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu, Wangyu [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: wangyuhu2001cn@yahoo.com.cn; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: sfxiao@yahoo.com.cn; Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Deng Huiqiu [Department of Applied Physics, Hunan University, Changsha 410082 (China)

    2009-09-15

    A palladium crystal has been constructed with 11808 atoms. 55 helium atoms occupied the octahedral position of palladium crystal are introduced and retained in a spherical region. Molecular dynamic simulations are performed in a constant temperature and constant volume ensemble (NVT) with temperature controlled by Nose-Hoover thermostat. The interactions between palladium atoms are described with modified analytic embedded atom method (MAEAM), the interactions between palladium atom and helium atom are in the form of Morse potential, and the interactions between helium atoms are in the form of L-J potential function. With the analysis of the radial distribution function (RDF) and microstructure, it reveals that some of helium atoms form a series of clusters with different size, and the nucleation core is random at low temperature, and which is the embryo of helium bubble. Increasing temperature can accelerate the process of bubble nucleation, and the clusters will aggregate and coalesce into a bigger one in which there are no palladium atoms, and it is considered as a helium bubble.

  5. Helium Behaviour in Waste Conditioning Matrices during Thermal Annealing

    Energy Technology Data Exchange (ETDEWEB)

    Wiss, Thierry A.; Hiernaut, J-P; Damen, P; Lutique, Stphanie; Fromknecht, R; Weber, William J.

    2006-06-30

    Reprocessing of spent fuel produces high level waste including minor actinides and long living fission products that might be disposed in waste conditioning matrices. Several natural mineral phases were proven to be able to incorporate fission products or actinides in their crystalline structure for long periods of time. In this study, synthetic compounds of zirconolite (CaZrTi2O7) and pyrochlores (Gd2Ti2O7 and Nd2Zr2O7) were fabricated and doped with the short-lived alpha-emitter 244Cm to increase the total amount of helium and damage generated in a laboratory time scale. Helium implantations were also used to simulate the damage caused by the alpha-decay and the build-up of helium in the matrix. The samples were annealed in a Knudsen cell, and the helium release profile interpreted in conjunction with radiation damage studies and previous analysis of annealing behaviour. Several processes like diffusion, trapping or phase changes could then be attributed to the helium behaviour depending on the material considered. Despite high damage and large amount of helium accumulated, the integrity of the studied materials was preserved during storage.

  6. Helium behaviour in waste conditioning matrices during thermal annealing

    Science.gov (United States)

    Wiss, T. A. G.; Hiernaut, J.-P.; Damen, P. M. G.; Lutique, S.; Fromknecht, R.; Weber, W. J.

    2006-06-01

    Reprocessing of spent fuel produces high level waste including minor actinides and long living fission products that might be disposed in waste conditioning matrices. Several natural mineral phases were proven to be able to incorporate fission products or actinides in their crystalline structure for long periods of time. In this study, synthetic compounds of zirconolite (CaZrTi2O7) and pyrochlores (Gd2Ti2O7 and Nd2Zr2O7) were fabricated and doped with the short-lived alpha-emitter 244Cm to increase the total amount of helium and damage generated in a laboratory time scale. Helium implantations were also used to simulate the damage caused by the alpha-decay and the build-up of helium in the matrix. The samples were annealed in a Knudsen cell, and the helium release profile interpreted in conjunction with radiation damage studies and previous analysis of annealing behaviour. Several processes like diffusion, trapping or phase changes could then be attributed to the helium behaviour depending on the material considered. Despite high damage and large amount of helium accumulated, the integrity of the studied materials was preserved during storage.

  7. A Helium-Carbon Correlation on the Extreme Horizontal Branch in $\\omega$ Centauri

    CERN Document Server

    Latour, Marilyn; Fontaine, Gilles; Bono, Giuseppe; Calamida, Annalisa; Brassard, Pierre

    2014-01-01

    Taking advantage of a recent FORS2/VLT spectroscopic sample of Extreme Horizontal Branch (EHB) stars in $\\omega$ Cen, we isolate 38 spectra well suited for detailed atmospheric studies and determine their fundamental parameters ($T_{\\rm eff}$, log $g$, and log $N$(He)/$N$(H)) using NLTE, metal line-blanketed models. We find that our targets can be divided into three groups: 6 stars are hot ($T_{\\rm eff}$$\\buildrel>\\over\\sim\\ $ 45,000 K) H-rich subdwarf O stars, 7 stars are typical H-rich sdB stars ($T_{\\rm eff}$$ \\buildrel\\over\\sim\\ $ $-$1.0) subdwarfs. Surprisingly and quite interestingly, these He-rich hot subdwarfs in $\\omega$ Cen cluster in a narrow temperature range ($\\sim$35,000 K to $\\sim$40,000 K). We additionally measure the atmospheric carbon abundance and find a most interesting positive correlation between the carbon and helium atmospheric abundances. This correlation certainly bears the signature of diffusion processes - most likely gravitational settling impeded by stellar winds or internal turb...

  8. FLOWRATE MEASUREMENT OF SUPERFLUID HELIUM%超流氦流量测量

    Institute of Scientific and Technical Information of China (English)

    张敏; 王如竹

    2000-01-01

    Superfluid helium is a unique cryogenic fluid,whose flowrate measurement is different from others.Classical flowmeters like turbine,venturi and ultrasonic flowmeters can all be used with HeⅡ to some extent,while there are still some special ones like fluidic and second sound flowmeters.But temperature-pulse flowmeter and hot-wire or hot-film flowmeter are considered not very suitable for HeⅡ flow measurement.%超流氦是一种性质特殊的低温流体,其流量测量与一般流体有所不同。涡轮流量计、文丘利流量计和超声波流量计在一定条件下均能正常使用,较为特殊的还有射流流量计和第二声流量计。热脉冲流量计、热丝或热膜型流量计在超流氦流量测量中均不宜采用。

  9. Two candidate brown dwarf companions around core helium-burning stars

    CERN Document Server

    Schaffenroth, V; Nagel, K; Geier, S; Koen, C; Heber, U; Edelmann, H

    2014-01-01

    Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost its entire hydrogen envelope in the red-giant phase. Binary interactions have been invoked, but single sdBs exist as well. We report the discovery of two close hot subdwarf binaries with small radial velocity amplitudes. Follow-up photometry revealed reflection effects originating from cool irradiated companions, but no eclipses. The lower mass limits for the companions of CPD-64$^{\\circ}$481 ($0.048\\,M_{\\rm \\odot}$) and PHL\\,457 ($0.027\\,M_{\\rm \\odot}$) are significantly below the stellar mass limit. Hence they could be brown dwarfs unless the inclination is unfavourable. Two very similar systems have already been reported. The probability that none of them is a brown dwarf is very small, 0.02%. Hence we provide further evidence that substellar companions with masses that low are able to eject a common envelope and form an sdB star. ...

  10. 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)

  11. Vitesse moyenne d'un écoulement à surface libre à partir de mesures des vitesses de surface par une méthode LSPIV

    OpenAIRE

    Rion, Guillaume

    2017-01-01

    Ce travail de fin d'études a pour but d'évaluer la précision d'une technique de mesure non intrusive de vitesse de surface : la LSPIV. Le principe de cette technique de mesure est basé sur l'analyse de séquences d'images horodatées. La LSPIV, acronyme de "Large Scale Particle Image Velocimetry" repose sur l'identification du déplacement de traceurs visibles à la surface de l'eau. Une vitesse de surface est déduite du déplacement de particules entre deux images successives et de l'intervalle d...

  12. Mesures in situ et à haute fréquence de la chimie d’un cours d’eau par spectrophotométrie UV-visible

    OpenAIRE

    Faucheux, Mikaël; Fovet, Ophélie

    2014-01-01

    La variabilité de la chimie d’un cours d’eau se manifeste sur des périodes courtes comme l’événement de crue (quelques heures), mais aussi plus longues, saisonnières, pluriannuelles et décennales. La mesure en continu de la qualité de l’eau est délicate. Les méthodes classiques et standardisées se basent sur des prélèvements d’eau dont les concentrations sont ensuite mesurées en laboratoire. Les contraintes liées au prélèvement, au stockage et aux coûts limitent donc fortement l’accès à des s...

  13. Mesure des fluctuations de température dans un résonateur équipant un système thermoacoustique

    OpenAIRE

    Poignand, Gaëlle; Berson, Arganthaël; Blanc Benon, Philippe; Comte-Bellot, Geneviève; Jondeau, Emmanuel

    2010-01-01

    National audience; Dans les systèmes thermoacoustiques, les fluctuations de température présentent un caractère fortement non-linéaire aux extrémités du stack. La connaissance de ces fluctuations est essentielle dans la détermination et l'optimisation des transferts de chaleur entre le stack et les échangeurs de chaleur et demande la mise au point de nouvelles méthodes de mesure. Cette étude présente une méthode de mesures des fluctuations de température le long d'un résonateur thermoacoustiq...

  14. Mesure de l'inconnexe d'une fonction aléatoire (théorie de la prévisibilité)

    OpenAIRE

    Ravussin, Pierre Emile; Baatard, François

    2008-01-01

    La notion de mesure d'une grandeur physique est définie au sens de la mécanique aléatoire. Les équations générales de l'hydrodynamique sont données en exemple. Un modèle mathématique de prévision basé sur des mesures physiques est formulé, tout d'abord dans un cas à une dimension, puis dans un champ tridimensionnel de vecteurs turbulents. § 1 Introduction. Dès 1966, j'ai été chargé dans le cadre du groupe E.P.U.L. - I.S.M., comprenant le service de la protection de l'air (Dr. A. Junod) et la ...

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

    OpenAIRE

    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...

  16. Diffusion Monte Carlo calculation of rate of elastic transmission of a helium vapor beam through a slab of superfluid helium

    Science.gov (United States)

    Lutsyshyn, Y.; Halley, J. W.

    2011-01-01

    We present the results of diffusion Monte Carlo calculations of the elastic transmission of a low-energy beam of helium atoms through a suspended slab of superfluid helium. These calculations represent a significant improvement on variational Monte Carlo methods which were previously used to study this problem. The results are consistent with the existence of a condensate-mediated transmission mechanism, which would result in very fast transmission of pulses through a slab.

  17. An NMR study of adsorbed helium films

    Science.gov (United States)

    Kent, Anthony Joseph

    The properties of sub-monolayer Helium-3 films adsorbed on two totally different but planar substrates, Mylar† film and exfoliated graphite have been studied using NMR. The nuclear magnetic relaxation times T1 and T 2 have been measured as functions of fractional monolayer completion, temperature, substrate plane orientation and Larmor frequency using a specially designed and constructed NMR spectrometer system. The results obtained with a Mylar film substrate are consistent3with the formation of patches of solid 3He at regions of preferential adsorption on the substrate. Measurements of T2 m very low coverage 3He films on exfoliated graphite also indicate that the adsorbate forms areas of relatively high density solid, in agreement with the thermodynamic analysis of Elgin and Goodstein. Finally, detailed measurements of T2 as a function of all of the above parameters at low areal densities will help us to characterise the relaxation processes for the fluid phase of 33He on exfoliated graphite. †Mylar is the tradename of poly(ethelene-terephthalate) film, marketed by Du Pont.

  18. Helium Loop Cooling Channel Hydraulic Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Olivas, Eric Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Morgan, Robert Vaughn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Woloshun, Keith Albert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-07-02

    New methods for generating ⁹⁹Mo are being explored in an effort to eliminate proliferation issues and provide a domestic supply of ⁹⁹mTc for medical imaging. Electron accelerating technology is used by sending an electron beam through a series of ¹⁰⁰Mo targets. During this process a large amount of heat is created, which directly affects the operating temperature set for the system. In order to maintain the required temperature range, helium gas is used to serve as a cooling agent that flows through narrow channels between the target disks. Currently we are tailoring the cooling channel entrance and exits to decrease the pressure drop through the targets. Currently all hardware has be procured and manufactured to conduct flow measurements and visualization via solid particle seeder. Pressure drop will be studied as a function of mass flow and diffuser angle. The results from these experiments will help in determining target cooling geometry and validate CFD code results.

  19. Classical helium atom with radiation reaction.

    Science.gov (United States)

    Camelio, G; Carati, A; Galgani, L

    2012-06-01

    We study a classical model of helium atom in which, in addition to the Coulomb forces, the radiation reaction forces are taken into account. This modification brings in the model a new qualitative feature of a global character. Indeed, as pointed out by Dirac, in any model of classical electrodynamics of point particles involving radiation reaction one has to eliminate, from the a priori conceivable solutions of the problem, those corresponding to the emission of an infinite amount of energy. We show that the Dirac prescription solves a problem of inconsistency plaguing all available models which neglect radiation reaction, namely, the fact that in all such models, most initial data lead to a spontaneous breakdown of the atom. A further modification is that the system thus acquires a peculiar form of dissipation. In particular, this makes attractive an invariant manifold of special physical interest, the zero-dipole manifold that corresponds to motions in which no energy is radiated away (in the dipole approximation). We finally study numerically the invariant measure naturally induced by the time-evolution on such a manifold, and this corresponds to studying the formation process of the atom. Indications are given that such a measure may be singular with respect to that of Lebesgue.

  20. Near field characteristics of buoyant helium plumes

    Indian Academy of Sciences (India)

    Kuchimanchi K Bharadwaj; Debopam Das; Pavan K Sharma

    2015-05-01

    Puffing and entrainment characteristics of helium plumes emanating out into ambient air from a circular orifice are investigated in the present study. Velocity and density fields are measured across a diametric plane using Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF) respectively in phase resolved manner. Experiments are performed in Froude numbers range 0.2–0.4 and for Reynolds numbers 58–248. Puffing frequency measurements reveal that the plume puffing frequencies are insensitive to the plume exit conditions, since the instability is buoyancy driven. The frequencies obtained in the present case are in agreement with frequencies obtained by Cetegen & Kasper (1996) for plumes originating from circular nozzles of various L/D ratios. Velocity and density measurements reveal that toroidal vortex formed during a puffing cycle entrains ambient air as it traverses downstream and this periodic engulfment governs the entrainment mechanism in pulsating plumes. The obtained velocity and density fields are used to calculate mass entrainment rates. It is revealed that though the flow is unsteady, the contribution of unsteady term in mass conservation to entrainment is negligible, and it becomes zero over a puff cycle. Finally, an empirical relation for variation of mass entrainment with height has been proposed, in which the non-dimensional mass entrainment is found to follow a power law with the non-dimensional height.

  1. Observation of the antimatter helium-4 nucleus.

    Science.gov (United States)

    2011-05-19

    High-energy nuclear collisions create an energy density similar to that of the Universe microseconds after the Big Bang; in both cases, matter and antimatter are formed with comparable abundance. However, the relatively short-lived expansion in nuclear collisions allows antimatter to decouple quickly from matter, and avoid annihilation. Thus, a high-energy accelerator of heavy nuclei provides an efficient means of producing and studying antimatter. The antimatter helium-4 nucleus (4He), also known as the anti-α (α), consists of two antiprotons and two antineutrons (baryon number B = -4). It has not been observed previously, although the α-particle was identified a century ago by Rutherford and is present in cosmic radiation at the ten per cent level. Antimatter nuclei with B Collider (RHIC; ref. 6) in 10(9) recorded gold-on-gold (Au+Au) collisions at centre-of-mass energies of 200 GeV and 62 GeV per nucleon-nucleon pair. The yield is consistent with expectations from thermodynamic and coalescent nucleosynthesis models, providing an indication of the production rate of even heavier antimatter nuclei and a benchmark for possible future observations of 4He in cosmic radiation.

  2. Mesures de procédure spéciales et respect des droits de l'homme Rapport général

    NARCIS (Netherlands)

    Vervaele, J.A.E.

    2009-01-01

    Le but du rapport général est de mener une analyse comparative des rapports nationaux en vue de présenter les processus de transformation des systèmes de justice pénale internes, en particulier du procès pénal, étant donné que des mesures procédurales spéciales sont introduites pour appréhender le t

  3. Mesure asymétrie avant-arriere des quarks lourds a LEP1 avec le détecteur OPAL

    CERN Document Server

    Lafoux, H

    A partir de l'ensemble des données accumulées par OPAL au cours de la première phase de fonctionnement du LEP, nous avons mesuré l'asymétrie avant-arrière des quarks b et c au voisinage du pic du Zo. Utilisant une méthode traditionnelle, basée sur la détection des leptons produits dans les désintégrations semi-leptoniques des hadrons lourds, nous avons cherché à optimiser chaque étape de la mesure, en mettant en œuvre les algorithmes les plus appropriés. Le recours aux réseaux de neurones artificiels s'est en particulier avéré d'une grande utilité lorsque le problème à résoudre impliquait la prise en compte simultanée de multiples sources d'informations, d'origine et de nature très variées. Nos résultats sont en bon accord avec ceux des autres mesures effectuées à LEP et compatibles avec les prédictions du Modèle Standard pour un quark top de 174 ± 31 GeV/c2 et un boson de Higgs de masse comprise entre 60 et 1000 GeV/c2

  4. Electronic temperature measurement on the deca II plasma using the Bremsstrahlung; Mesure de la temperature electronique du plasma de deca II par etude du rayonnement de freinage

    Energy Technology Data Exchange (ETDEWEB)

    Dumas, A. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1967-06-01

    The electronic temperature of the DECA II machine's plasma is determined by studying the Bremsstrahlung. Two types of detectors are used for this measurement, a set scintillator-photo-multiplicator and a photoelectric effect detector with a massive silver target. The method used is the classical 'absorbent method', The absorbents used are thin formvar foils whose thickness is between 600 and 12 500 angstrom. The measurements done in two different working conditions of the DECA II machine have given: Te {approx_equal} 200 eV in the first case and Te {approx_equal} 70 eV in the second case. (author) [French] Nous avons determine la temperature electronique du plasma de la machine DECA II par l'etude du rayonnement de freinage. Pour cette mesure nous avons utilise deux types de detecteurs: des ensembles scintillateur-photomultiplicateur et un detecteur a effet photoelectrique a cible massive en argent. La methode utilisee pour cette mesure est la classique methode des absorbants. Nous avons utilise des feuilles de format tres mince (de 600 a 12 500 angstrom) comme absorbant. Les mesures faites dans deux regimes de travail differents de la machine DECA II nous ont conduit a: Te {approx_equal} 200 eV dans un cas et Te {approx_equal} eV dans l'autre cas. (auteur)

  5. Aspects et mesure de la qualité de vie : évolution et renouvellement des tableaux de bord métropolitains

    Directory of Open Access Journals (Sweden)

    Pierre J. Hamel

    2008-02-01

    Full Text Available La mesure de la qualité de vie à l’intérieur des espaces urbains préoccupe les administrations publiques depuis nombre d’années. Cet article passe en revue les modèles de mesure de la qualité de vie développés par les métropoles canadiennes. Il s’interroge sur l’évolution de ces modèles de mesure et sur leur capacité à rendre compte des différentes problématiques désormais associées à la notion de qualité de vie comme le développement social, l’environnement, la société du risque, les ambiances urbaines ou la compétitivité urbaine.For a number of years now, government bodies at all levels have been concerned with measuring quality of life within urban areas. This paper reviews the models used by Canada’s metropolises to measure quality of life. It examines how the models have evolved and their capacity to consider various issues which have become associated with the notion of quality of life, such as social development, environment, risk society, urban surroundings, or urban competitiveness.

  6. Mesure des stades de developpement du sapin baumier (Abies balsamea [L.] Mill.) par teledetection des maxima locaux sur images a tres haute resolution

    Science.gov (United States)

    Demers, Alain

    L'objectif principal de cette these est d'identifier les parametres cles pour lier le developpement morphologique de la cime du sapin baumier (Abies balsamea [L.] Mill.) aux patrons de reflectance qu'elle genere sur une image aerienne a haute resolution. La quantite et la distribution spatiale des aiguilles dans le sapin dependent de la structure des branches. Un mecanisme de ramification particulier (la reiteration) ressort comme le parametre cle pour lier l'augmentation de la biomasse foliaire et la forme de la branche. Les reiterats forment des agglomerats de feuillage qui engendrent des inegalites dans les patrons de reflectance de la cime. La reflectance est plus elevee ou il y a une forte concentration de reiterats (maximum local). On demontre que le developpement du sapin baumier se mesure au moyen de l'analyse des maxima locaux de la cime sur une image. La biomasse de l'arbre se mesure par la teledetection et l'analyse des patrons de reflectance de la cime, c'est-a-dire la mesure du niveau de reiteration par le decompte des maxima locaux de la cime. Cette etude demontre qu'il est possible de proceder a l'inventaire du volume de bois d'un peuplement par la teledetection de l'architecture des arbres.

  7. CALCUL DU DEPHASAGE A LA REFLEXION ET DES INDICES OPTIQUES DE L’ALLIAGE AMORPHE PD30Y70 A PARTIR DE LA MESURE DE SA REFLEXION

    Directory of Open Access Journals (Sweden)

    H BELBAH

    2002-06-01

    Full Text Available Les couches minces de l’alliage amorphe de composition Pd30Y70 sont déposées par pulvérisation cathodique sur des substrats en silice, sous un vide de 10-7 Torr. Les couches obtenues sont opaques et par conséquent leur transmission est nulle. Le spectre de réflexion de Pd30Y70  est mesuré dans le domaine d’énergie entre 0,5 et 6,2 eV. Cette mesure sert au calcul du déphasage à la réflexion de l’alliage à partir de l’intégrale de Kramers-Kronig. Les valeurs mesurées de la réflexion et les valeurs calculées du déphasage à la réflexion permettent de remonter aux constantes optiques (indices de réfraction et d’extinction de l’alliage et à sa structure électronique à partir des spectres d’absorption optique calculés. Le spectre d’absorption optique de Pd30Y70 amorphe est dominé par deux structures dont l’une est due aux états 4d de Pd centrée autour de 4 eV et l’autre aux états 4d de Y aux basses énergies.

  8. A Deep Test of Radial Differential Rotation in a Helium-atmosphere White Dwarf. I. Discovery of Pulsations in PG 0112+104

    Science.gov (United States)

    Hermes, J. J.; Kawaler, Steven D.; Bischoff-Kim, A.; Provencal, J. L.; Dunlap, B. H.; Clemens, J. C.

    2017-02-01

    We present the detection of non-radial oscillations in a hot, helium-atmosphere white dwarf using 78.7 days of nearly uninterrupted photometry from the Kepler space telescope. With an effective temperature >30,000 K, PG 0112+104 becomes the hottest helium-atmosphere white dwarf known to pulsate. The rich oscillation spectrum of low-order g-modes includes clear patterns of rotational splittings from consecutive sequences of dipole and quadrupole modes, which can be used to probe the rotation rate with depth in this highly evolved stellar remnant. We also measure a surface rotation rate of 10.17404 hr from an apparent spot modulation in the K2 data. With two independent measures of rotation, PG 0112+104 provides a remarkable test of asteroseismic inference.

  9. Detection of significant differences between absorption spectra of neutral helium and low temperature photoionized helium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Szczurek, M. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

    2013-11-15

    In this work, spectral investigations of photoionized He plasmas were performed. The photoionized plasmas were created by irradiation of helium stream, with intense pulses from laser-plasma extreme ultraviolet (EUV) source. The EUV source was based on a double-stream Xe/Ne gas-puff target irradiated with 10 ns/10 J Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region below 20 nm, however, spectrally integrated intensity at longer wavelengths was also significant. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The long-wavelength part of the EUV radiation was used for backlighting of the photoionized plasmas to obtain absorption spectra. Both emission and absorption spectra in the EUV range were investigated. Significant differences between absorption spectra acquired for neutral helium and low temperature photoionized plasmas were demonstrated for the first time. Strong increase of intensities and spectral widths of absorption lines, together with a red shift of the K-edge, was shown.

  10. Spectroscopic observations of Hot-Jupiters with the Hubble WFC3 camera

    Science.gov (United States)

    Damiano, Mario; Morello, Giuseppe; Tsiaras, Angelos; Zingales, Tiziano; Tinetti, Giovanna; ExoLights, ExoMol

    2016-10-01

    Thousands of exoplanets have been discovered with a huge range of masses, sizes and orbits. The next step to characterize them is to study their atmosphere. The atmospheres of giant planets are mostly made of hydrogen and helium. The relevant questions therefore concern the amounts of all elements other than hydrogen and helium, i.e. the heavy elements, that are present.The atmospheres of hot Jupiters present a critical advantage compared to the planets of the Solar System: their high temperature.Unlike Jupiter and Saturn, there is no cold trap in their atmosphere for species such as H2O, CH4, NH3, CO2 etc., which condense at much colder temperatures. Observations of hot gaseous exoplanets can therefore provide a unique access to their elementary composition (especially C, O, N, S) and enable the understanding of the early stage of planetary and atmospheric formation during the nebular phase and the following few millions years.Here we present new spectroscopic observations of hot-Jupiters' atmospheres obtained with the WFC3 camera. In our presentation we will focus on the data reduction method used and on the interpretation of the results through state of the art spectral retrieval models.

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

    Science.gov (United States)

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

    2012-12-01

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

  12. Phonon amplification using evaporation and adsorption of helium

    Energy Technology Data Exchange (ETDEWEB)

    More, T.; Adams, J.S.; Bandler, S.R.; Broueer, S.M.; Lanou, R.E.; Maris, H.J.; Seidel, G.M. [Department of Physics, Brown University, Providence, Rhode Island 02912 (United States)

    1996-07-01

    We report the results of experiments designed to investigate the feasibility of amplifying a phonon signal using the evaporation of helium from a superfluid film and its subsequent readsorption onto a helium-free surface. We envision a multistage amplifier in which helium is evaporated from a wafer with a helium film only on one side and then adsorbed onto the film-free surface of a similar wafer. The phonons created by the adsorption reach the film on the opposite side of the wafer and potentially desorb more helium than was evaporated by the first wafer. The amplification would come from the high ratio of the binding energy of a helium atom to a film-free surface relative to the binding energy to the liquid. A number of experiments are reported that investigate the efficiencies of the individual steps of the process. The gain per stage is found to be about 3 for high-energy densities in which multiphonon processes are possible. At low-energy densities, the energy deposited into a film-free wafer is found to be less than the original input energy, with the ratio of output to input energy 0.2. Since in applications requiring amplification the phonon density produced by the adsorption of helium on a wafer will be low, the configuration we have studied{emdash}phonons produced in silicon coated with a saturated {sup 4}He film{emdash}will not result in amplification. However, other configurations might improve the efficiency enough to make an amplifier possible. {copyright} {ital 1996 The American Physical Society.}

  13. Thermal Annealing Behavior of Helium in Ti Films Deposited by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; HE Zhi-Jiang; LIU Chao-Zhuo; WANG Xu-Fei; SHI Li-Qun

    2012-01-01

    Helium contents of up to 30at.% are prepared in sputter-deposited Ti Silms. Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the fi1ms at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), as well as thermal helium desorption spectroscopy (THDS). It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs, which corresponds to the change of stopping cross-section of helium atoms in the Ti 61m due to the change of physical-state of helium in the evolution of helium bubble. The ion beam analysis on the helium evolution is consistent with the THDS measurement. Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.%Helium contents of up to 30at.% are prepared in sputter-deposited Ti films.Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the films at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA),as well as thermal helium desorption spectroscopy (THDS).It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs,which corresponds to the change of stopping cross-section of helium atoms in the Ti film due to the change of physical-state of helium in the evolution of helium bubble.The ion beam analysis on the helium evolution is consistent with the THDS measurement.Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.

  14. On the Hot Money Trail

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The huge influx of international hot money is threatening inflation and affecting the country’s monetary policy In the last three months, the country’s financial supervisory departments have conducted frequent but atypical investi-gations of hot money.

  15. How hot is the sun

    Institute of Scientific and Technical Information of China (English)

    刘超

    2001-01-01

    Do you know how hot thesun is? There are no solidsor liquids on the sun. Why not? The temperature onoutside the sun is more than 10, 000℃, and that at the centre is about 20, 000, 000℃.The sun is so hot that all thesolids and all the liquids havebeen turned into gases.

  16. The Evolutionary Population Synthesis Model for Helium-Enhanced Stellar Populations

    Science.gov (United States)

    Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook

    2017-01-01

    The discovery of multiple stellar populations in the Milky Way globular clusters has stimulated a great deal of researches on the helium enhanced stellar populations. Here, we present the evolutionary population synthesis models for integrated spectro-photometric evolution of simple stellar populations (SSPs) with varied initial helium abundances. The integrated properties of helium-enhanced SSPs depend on metallicity and age as are the normal-helium SSPs, but the properties vary greatly with the initial helium abundance. We will discuss how helium-enhanced stellar populations explain many interesting observations of globular clusters and their host galaxies.

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

    Science.gov (United States)

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

    2013-12-01

    Applicability of Henry's Law to helium solubility in olivine We have experimentally determined helium solubility in San Carlos olivine across a range of helium partial pressures (PHe) with the goal of quantifying how noble gases behave during partial melting of peridotite. Helium solubility in olivine correlates linearly with PHe between 55 and 1680 bar. This linear relationship suggests Henry's Law is applicable to helium dissolution into olivine up to 1680 bar PHe, providing a basis for extrapolation of solubility relationships determined at high PHe to natural systems. This is the first demonstration of Henry's Law for helium dissolution into olivine. Averaging all the data of the PHe series yields a Henry's coefficient of 3.8(×3.1)×10-12 mol g-1 bar-1. However, the population of Henry's coefficients shows a positive skew (skewness = 1.17), i.e. the data are skewed to higher values. This skew is reflected in the large standard deviation of the population of Henry's coefficients. Averaging the median values from each experiment yields a lower Henry's coefficient and standard deviation: 3.2(× 2.3)×10-12 mol g-1 bar-1. Combining the presently determined helium Henry's coefficient for olivine with previous determinations of helium Henry's coefficients for basaltic melts (e.g. 1) yields a partition coefficient of ~10-4. This value is similar to previous determinations obtained at higher PHe (2). The applicability of Henry's Law here suggests helium is incorporated onto relatively abundant sites within olivine that are not saturated by 1680 bar PHe or ~5×10-9 mol g-1. Large radius vacancies, i.e. oxygen vacancies, are energetically favorable sites for noble gas dissolution (3). However, oxygen vacancies are not abundant enough in San Carlos olivine to account for this solubility (e.g. 4), suggesting the 3x10-12 mol g-1 bar-1 Henry's coefficient is associated with interstitial dissolution of helium. Helium was dissolved into olivine using an externally heated

  18. Mesures de contrôle en psychiatrie : impacts cliniques et juridiques de la recherche interprétative

    Directory of Open Access Journals (Sweden)

    EMMANUELLE BERNHEIM

    2009-01-01

    Full Text Available L’utilisation des mesures de contrôle (isolement et contention est une pratique très controversée en psychiatrie, tant sur les plans thérapeutique que légal. Le projet de recherche dont il est question dans cet article vise à mettre au jour l’expérience subjective des infirmières et des patients, dans un objectif d’amélioration des pratiques cliniques. La valorisation du discours des patients, à travers une posture épistémologique interprétative, se heurte aux exigences peu adaptées de comités d’éthique de la recherche habitués aux caractéristiques de la recherche positiviste. Pourtant, c’est par la mise au jour des expériences des usagers que des progrès, tant au niveau clinique que juridique, ont pu être faits dans le passé. Aujourd’hui, la recherche doit servir à redonner une place aux patients, non seulement au sein de l’hôpital, mais également au sein de la société.

  19. La thèse de Feldstein-Horioka: Ue mesure de la mobilité internationale du capital

    Directory of Open Access Journals (Sweden)

    de Sousa Andrade Alberto Joao

    2007-01-01

    Full Text Available (portugalski Nous présentons la thèse de Feldstein-Horioka (F-H sur la mobilité du capital et les développements qu’elle a suscités. Il s’agit d’une thèse qui est très ouverte à la possibilité de réfutation et dont l’histoire illustre bien la pensée méthodologique nonnaïve de Karl Popper: les discussions sur sa réfutation, en parallèle avec les tentatives de consolidation ("d’immunisation", au sens de K. Popper, ont conduit à de nouvelles lectures sur la mobilité du capital. Ces efforts de consolidation (d’ "immunization" ont conduit cette thèse à intégrer des nouvelles méthodologies économétriques et à changer partiellement son objet, en mesurant aussi la soutenabilité externe. La thèse de F-H constitue un cas exemplaire d’intégration de l’analyse théorique et d’analyse empirique.

  20. LRO-LAMP Observations of Lunar Exospheric Helium

    Science.gov (United States)

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

    2015-11-01

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

  1. Theoretical model of the helium zone plate microscope

    Science.gov (United States)

    Salvador Palau, Adrià; Bracco, Gianangelo; Holst, Bodil

    2017-01-01

    Neutral helium microscopy is a new technique currently under development. Its advantages are the low energy, charge neutrality, and inertness of the helium atoms, a potential large depth of field, and the fact that at thermal energies the helium atoms do not penetrate into any solid material. This opens the possibility, among others, for the creation of an instrument that can measure surface topology on the nanoscale, even on surfaces with high aspect ratios. One of the most promising designs for helium microscopy is the zone plate microscope. It consists of a supersonic expansion helium beam collimated by an aperture (skimmer) focused by a Fresnel zone plate onto a sample. The resolution is determined by the focal spot size, which depends on the size of the skimmer, the optics of the system, and the velocity spread of the beam through the chromatic aberrations of the zone plate. An important factor for the optics of the zone plate is the width of the outermost zone, corresponding to the smallest opening in the zone plate. The width of the outermost zone is fabrication limited to around 10 nm with present-day state-of-the-art technology. Due to the high ionization potential of neutral helium atoms, it is difficult to build efficient helium detectors. Therefore, it is crucial to optimize the microscope design to maximize the intensity for a given resolution and width of the outermost zone. Here we present an optimization model for the helium zone plate microscope. Assuming constant resolution and width of the outermost zone, we are able to reduce the problem to a two-variable problem (zone plate radius and object distance) and we show that for a given beam temperature and pressure, there is always a single intensity maximum. We compare our model with the highest-resolution zone plate focusing images published and show that the intensity can be increased seven times. Reducing the width of the outermost zone to 10 nm leads to an increase in intensity of more than 8000

  2. Helium shells and faint emission lines from slitless flash spectra.

    Science.gov (United States)

    Bazin, Cyril; Koutchmy, Serge

    2013-05-01

    At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence.

  3. Helium shells and faint emission lines from slitless flash spectra

    Directory of Open Access Journals (Sweden)

    Cyril Bazin

    2013-05-01

    Full Text Available At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence.

  4. Validation of Helium Inlet Design for ITER Toroidal Field Coil

    CERN Document Server

    Boyer, C; Hamada, K; Foussat, A; Le Rest, M; Mitchell, N; Decool, P; Savary, F; Sgobba, S; Weiss, K-P

    2014-01-01

    The ITER organization has performed design and its validation tests on a helium inlet structure for the ITER Toroidal Field (TF) coil under collaboration with CERN, KIT, and CEA-Cadarache. Detailed structural analysis was performed in order to optimize the weld shape. A fatigue resistant design on the fillet weld between the shell covers and the jacket is an important point on the helium inlet structure. A weld filler material was selected based on tensile test at liquid helium temperature after Nb3Sn reaction heat treatment. To validate the design of the weld joint, fatigue tests at 7 K were performed using heat-treated butt weld samples. A pressure drop measurement of a helium inlet mock-up was performed by using nitrogen gas at room temperature in order to confirm uniform flow distribution and pressure drop characteristic. These tests have validated the helium inlet design. Based on the validation, Japanese and European Union domestic agencies, which have responsibilities of the TF coil procurement, are pr...

  5. Analysis of a low-temperature magnetic helium pump

    Science.gov (United States)

    Prenger, Coyne; Stewart, Walter

    In an effort to improve reliability of cryocoolers, concepts involving no moving parts are being investigated. One concept utilizes an Active Magnetic Regenerator, AMR, to produce refrigeration. However, circulation of the helium working fluid is required for operation of the device. Currently available helium pumps have moving parts and; therefore, result in poor reliability. We propose a magnetically driven pump to provide the helium circulation for the AMR. The pump utilizes the magnetocaloric effect to produce an oscillatory helium flow and; has no moving parts. An analytical model has been developed to analyze the pump's performance in conjunction with an AMR operating between 7 and 20 K. At a frequency of 1 Hz a 0.5 liter pump can produce a 0.75 g/s flow rate at 20 K at an operating pressure of 5 atm. At the liquid helium temperature a two-phase version of this pump would perform substantially better than the single-phase version. A design concept has been developed and will be presented along with the model results.

  6. 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.

  7. 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.

  8. Study of helium embrittlement in boron doped EUROFER97 steels

    Science.gov (United States)

    Gaganidze, E.; Petersen, C.; Aktaa, J.

    2009-04-01

    To simulate helium effects in Reduced Activation Ferritic/Martensitic steels, experimental heats ADS2, ADS3 and ADS4 with the basic composition of EUROFER97 (9%Cr-WVTa) were doped with different contents of natural boron and separated 10B-isotope (0.008-0.112 wt.%) and irradiated in High Flux Reactor (HFR) Petten up to 16.3 dpa at 250-450 °C and in Bor-60 fast reactor in Dimitrovgrad up to 31.8 dpa at 332-338 °C. The embrittlement and hardening are investigated by instrumented Charpy-V tests with subsize specimens. Complete burn-up of 10B isotope under neutron irradiation in HFR Petten led to generation of 84, 432 and 5580 appm He and partial boron-to-helium transformation in Bor-60 led to generation of 9, 46, 880 appm He in ADS2, ADS3 and ADS4 heats, respectively. At low irradiation temperatures Tirr ⩽ 340 °C the boron doped steels show progressive embrittlement with increasing helium amount. Irradiation induced DBTT shift of EUROFER97 based heat doped with 1120 wppm separated 10B isotope could not be quantified due to large embrittlement found in the investigated temperature range. At Tirr ⩽ 340 °C helium induced extra embrittlement is attributed to material hardening induced by helium bubbles and described in terms of phenomenological model.

  9. Electronically excited rubidium atom in a helium cluster or film

    Science.gov (United States)

    Leino, Markku; Viel, Alexandra; Zillich, Robert E.

    2008-11-01

    We present theoretical studies of helium droplets and films doped with one electronically excited rubidium atom Rb∗ (P2). Diffusion and path integral Monte Carlo approaches are used to investigate the energetics and the structure of clusters containing up to 14 helium atoms. The surface of large clusters is approximated by a helium film. The nonpair additive potential energy surface is modeled using a diatomic in molecule scheme. Calculations show that the stable structure of Rb∗Hen consists of a seven helium atom ring centered at the rubidium, surrounded by a tirelike second solvation shell. A very different structure is obtained when performing a "vertical Monte Carlo transition." In this approach, a path integral Monte Carlo equilibration starts from the stable configuration of a rubidium atom in the electronic ground state adsorbed to the helium surface after switching to the electronically excited surface. In this case, Rb∗Hen relaxes to a weakly bound metastable state in which Rb∗ sits in a shallow dimple. The interpretation of the results is consistent with the recent experimental observations [G. Auböck et al., Phys. Rev. Lett. 101, 035301 (2008)].

  10. Repetitious-Hot-Pressing Technique in Hot-Pressing Process

    Institute of Scientific and Technical Information of China (English)

    Shixue SONG; Xing AI; Wei GAO; Jun ZHAO

    2003-01-01

    A new pressing method was proposed for hot-pressing process. Experimental results indicated that the porosity in Al2O3/TiC/Ni/Mo (hereafter called Al2O3/TiC composite) composite compacts decreases by 6% after adopting this new technique,compared to traditional hot-pressing technique under the same sintering temperature. The flexural strength and Vickerhardness increase from 883 MPa to 980 MPa and from 16 GPa to 21.1 GPa, respectively. A theoretical model was given toanalyze the densification mechanism of the composite in the process of repetitious-hot-pressing.

  11. Interactions of satellite-speed helium atoms with satellite-surfaces. 1. Spatial distributions of reflected helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Liu, S.M.; Rodgers, W.E.; Knuth, E.L.

    1975-06-01

    Interactions of satellite-speed helium atoms with practical satellite surfaces were investigated experimentally, and spatial distributions of satellite-speed helium beams scattered from four different engineering surfaces were measured. The 7000-m/s helium beams were produced using an arc-heated supersonic molecular beam source. The test surfaces included cleaned 6061-T6 aluminum plate, anodized aluminum foil, white paint, and quartz surfaces. Both in-plane (in the plane containing the incident beam and the surface normal) and out-of-plane spatial distributions of reflected helium atoms were measured for six different incidence angles (0, 15, 30, 45, 60, and 75 deg from the surface normal). It was found that a large fraction of the incident helium atoms were scattered back in the vicinity of the incoming beam, particularly in the case of glancing incidence angles. This unexpected scattering feature results perhaps from the gross roughness of these test surfaces. This prominent backscattering could yield drag coefficients which are higher than for surfaces with either forward-lobed or diffusive (cosine) scattering patterns. (auth)

  12. Observation of a helium ion energy threshold for retention in tungsten exposed to hydrogen/helium mixture plasma

    Science.gov (United States)

    Thompson, M.; Deslandes, A.; Morgan, T. W.; Elliman, R. G.; De Temmerman, G.; Kluth, P.; Riley, D.; Corr, C. S.

    2016-10-01

    Helium retention is measured in tungsten samples exposed to mixed H/He plasma in the Magnum-PSI linear plasma device. It is observed that there is very little He retention below helium ion impact energies of 9.0+/- 1.4 eV, indicating the existence of a potential barrier which must be overcome for implantation to occur. The helium retention in samples exposed to plasma at temperatures  >1000 K is strongly correlated with nano-bubble formation measured using grazing incidence small-angle x-ray scattering. The diameters of nano-bubbles were not found to increase with increasing helium concentration, indicating that additional helium must be accommodated by increasing the bubble concentration or an increase in bubble pressure. For some samples pre-irradiation with heavy ions of 2.0 MeV energy is investigated to simulate the effects of neutron damage. It is observed that nano-bubble sizes are comparable between samples pre-irradiated with heavy-ions, and those without heavy-ion pre-irradiation.

  13. Photochemistry of 3-hydroxyflavone inside superfluid helium nanodroplets.

    Science.gov (United States)

    Lehnig, R; Pentlehner, D; Vdovin, A; Dick, B; Slenczka, A

    2009-11-21

    3-Hydroxyflavone is a prototype system for excited state intramolecular proton transfer which is one step of a closed loop photocycle. It was intensively studied for the bare molecule and for the influence of solvents. In the present paper this photocycle is investigated for 3-hydroxyflavone and some hydrated complexes when doped into superfluid helium droplets by the combined measurement of fluorescence excitation spectra and dispersed emission spectra. Significant discrepancies in the proton transfer behavior to gas phase experiments provide evidence for the presence of different complex configurations of the hydrated complexes in helium droplets. Moreover, for bare 3-hydroxyflavone and its hydrated complexes the proton transfer appears to be promoted by the helium environment.

  14. A cryogenic axial-centrifugal compressor for superfluid helium refrigeration

    CERN Document Server

    Decker, L; Schustr, P; Vins, M; Brunovsky, I; Lebrun, P; Tavian, L

    1997-01-01

    CERN's new project, the Large Hadron Collider (LHC), will use superfluid helium as coolant for its high-field superconducting magnets and therefore require large capacity refrigeration at 1.8 K. This may only be achieved by subatmospheric compression of gaseous helium at cryogenic temperature. To stimulate development of this technology, CERN has procured from industry prototype Cold Compressor Units (CCU). This unit is based on a cryogenic axial-centrifugal compressor, running on ceramic ball bearings and driven by a variable-frequency electrical motor operating under low-pressure helium at ambient temperature. The machine has been commissioned and is now in operation. After describing basic constructional features of the compressor, we report on measured performance.

  15. An MCMC determination of the primordial helium abundance

    CERN Document Server

    Aver, Erik; Skillman, Evan D

    2011-01-01

    Spectroscopic observations of the chemical abundances in metal-poor H II regions provide an independent method for estimating the primordial helium abundance. H II regions are described by several physical parameters such as electron density, electron temperature, and reddening, in addition to y, the ratio of helium to hydrogen. It had been customary to estimate or determine self-consistently these parameters to calculate y. Frequentist analyses of the parameter space have been shown to be successful in these determinations, and Markov Chain Monte Carlo (MCMC) techniques have proven to be very efficient in sampling this parameter space. Nevertheless, accurate determination of the primordial helium abundance from observations of H II regions is constrained by both systematic and statistical uncertainties. In an attempt to better reduce the latter, and better characterize the former, we apply MCMC methods to the large dataset recently compiled by Izotov, Thuan, & Stasinska (2007). To improve the reliability...

  16. Supersonic jets of hydrogen and helium for laser wakefield acceleration

    CERN Document Server

    Svensson, K.; Wojda, F.; Senje, L.; Burza, M.; Aurand, B.; Genoud, G.; Persson, A.; Wahlström, C.-G.; Lundh, O.

    2016-01-01

    The properties of laser wakefield accelerated electrons in supersonic gas flows of hydrogen and helium are investigated. At identical backing pressure, we find that electron beams emerging from helium show large variations in their spectral and spatial distributions, whereas electron beams accelerated in hydrogen plasmas show a higher degree of reproducibility. In an experimental investigation of the relation between neutral gas density and backing pressure, it is found that the resulting number density for helium is ∼30% higher than for hydrogen at the same backing pressure. The observed differences in electron beam properties between the two gases can thus be explained by differences in plasma electron density. This interpretation is verified by repeating the laser wakefield acceleration experiment using similar plasma electron densities for the two gases, which then yielded electron beams with similar properties.

  17. 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.

  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. Nonradiative formation of the positron-helium triplet bound state

    Science.gov (United States)

    di Rienzi, Joseph; Drachman, Richard J.

    2007-02-01

    We have previously calculated the cross section for radiative formation of the interesting bound state consisting of a positron bound to helium, where the atomic electrons are in the triplet spin state. That process uses the metastable triplet helium system as target, and, as expected, it has a very small cross section. In this paper we examine a more probable process in which the state of interest is produced in an exchange rearrangement collision between a positronium atom and the singlet helium ground state: Ps+He(Se1)→PsHe+(Se3)+e- . The present calculation is done in the plane-wave Born approximation, using simple initial and final wave functions and compares post and prior forms.

  20. Experience with Dry Running Vacuum Pumps in Helium Service

    Science.gov (United States)

    Arztmann, R.

    2008-03-01

    A process vacuum system for helium using dry running vacuum pumps only was shop tested and installed in a refrigeration plant to serve cavities operating at 2K for a cryogenic storage ring. The paper explains the joint development steps of Busch AG and Linde Kryotechnik AG to use dry running vacuum pumps for helium service at ambient temperature. A roots type booster pump followed by a non lube rotary screw pump provides very good performance in a helium vacuum pump system. Variable frequency drives on both pumps allow to adjust the pump characteristics to a wide range of operating parameters. Operation without friction of sealing elements in the compression space also of the screw pump promises extended maintenance intervals and virtually no wear on the rotors. The current plant operation at Max Plank Institute in Heidelberg, Germany Laboratory will provide additional experience for further applications.

  1. Helium and neon isotopes in deep Pacific Ocean sediments

    Science.gov (United States)

    Nier, A. O.; Schlutter, D. J.; Brownlee, D. E.

    1990-01-01

    Helium and neon concentration measurements, along with isotope ratio determinations, have been made for particles collected in the deep Pacific with a magnetic sled, and they are believed to be of extraterrestrial origin. Analyses were made for samples consisting of composites of many extremely fine particles and for several individual particles large enough to contain sufficient gas for analysis but small enough to escape melting in their passage through the atmosphere. Step-heating was employed to extract the gas. Cosmic-ray spallation products or solar-wind helium and neon, if present, were not abundant enough to account for the isotopic compositions measured. In the case of the samples of magnetic fines, the low temperature extractions provided elemental and isotopic ratios in the general range found for the primordial gas in carbonaceous chondrites and gas-rich meteorites. The isotopic ratios found in the high temperature extractions suggest the presence of solar-flare helium and neon.

  2. Simulation of Helium Behaviour in Titanium Crystals Using Molecular Dynamics

    Institute of Scientific and Technical Information of China (English)

    WANG Jun; HOU Qing; SUN Tie-Ying; WU Zhong-Cheng; LONG Xing-Gui; WU Xing-Chun; LUO Shun-Zhong

    2006-01-01

    @@ The behaviour of helium in Ti crystals at 300 K has been investigated by means of the molecular dynamics. The study is focused on the influences of He-Ti interaction on the aggregation of helium atoms in the substrate. When a Born-Mayer potential is used to describe the He-Ti interaction, the He atoms are unable to cluster with each other due to the weak bridge barrier that cannot trap the helium atoms, Whereas using a He-Ti potential that is constructed by fitting the ab initio pairwise He-Ti potential, the clustering of He atoms can be observed. The results indicate that suitable He-Ti potential plays an important role in the formation of He clusters in metals.Moreover, it is noted that the shape of the formed He cluster is irregular, and the produced defect prefers to congregating on one side of the He cluster rather than spreading symmetrically around it.

  3. Financing strategies for lunar energy enterprises: The helium-3 initiative

    Science.gov (United States)

    Schmitt, Harrison H.

    1995-01-01

    Governments presently have little individual or collective interest in financing large scale lunar enterprises, either for science or potential resource utilization. For example, preliminary technical and economic considerations of the return of lunar helium-3 (3He) for terrestrial fusion power plants suggest positive economic and enviromental returns, however, no significant governmental activity has been focused on this or other space related energy options. General analysis of both short and long term returns on investment for a lunar helium-3 enterprise, including considerations of future launch costs, strongly suggests that private financing may be attracted to this endeavor. A privately organized ``catalytic financing'' approach to providing start-up capital for a lunar helium-3 enterprise appears to be worth consideration.

  4. Four-Parameter Scheme for Ground Level of Helium Atom

    Institute of Scientific and Technical Information of China (English)

    HU Xian-Quan; XU Jie; MA Yong; ZHENG Rui-Lun

    2006-01-01

    In this paper, the ground state wave function of four parameters is developed and the expression of the ground state level is derived for the helium atom when the radial Schrodinger equation of the helium atom is solved.The ground energy is respectively computed by the optimized algorithms of Matlab 7.0 and the Monte Carlo methods.Furthermore, the ground state wave function is obtained. Compared with the experiment value and the value with the variation calculus in reference, the results of this paper show that in the four-parameter scheme, not only the calculations become more simplified and precise, but also the radial wave function of the helium atom meets the space symmetry automatically in ground state.

  5. Long flexible transfer lines for gaseous and liquid helium

    CERN Document Server

    Laeger, H; Rohner, P

    1978-01-01

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

  6. Characterizing uniform discharge in atmospheric helium by numerical modelling

    Institute of Scientific and Technical Information of China (English)

    Lü Bo; Wang Xin-Xin; Luo Hai-Yun; Liang Zhuo

    2009-01-01

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

  7. The Story of Helium and the Birth of Astrophysics

    CERN Document Server

    Nath, Biman B

    2013-01-01

    Biman Nath The Story of Helium and the Birth of Astrophysics Helium was the first element ever discovered by astronomers. Its presence was first indicated in the Sun and not on Earth. Further, its discovery marked the birth of the new science of astrophysics. However, it turns out that the events leading to the discovery of helium have been rather misrepresented in books, journals, and even encyclopedias. The usual story about its joint discovery during a solar eclipse in 1868 by French astronomer Pierre Janssen and late in England by Norman Lockyer, is far from the truth. Janssen never mentioned any new spectral line in his reports. The actual story turns out to be as dramatic as in fiction. This book tells the story without jargon, using the words of the scientists themselves (from their letters and reports), and rescues the real story from the backwaters of history.

  8. Hot Hydrogen Test Facility

    Science.gov (United States)

    Swank, W. David; Carmack, Jon; Werner, James E.; Pink, Robert J.; Haggard, DeLon C.; Johnson, Ryan

    2007-01-01

    The core in a nuclear thermal rocket will operate at high temperatures and in hydrogen. One of the important parameters in evaluating the performance of a nuclear thermal rocket is specific impulse, ISP. This quantity is proportional to the square root of the propellant's absolute temperature and inversely proportional to square root of its molecular weight. Therefore, high temperature hydrogen is a favored propellant of nuclear thermal rocket designers. Previous work has shown that one of the life-limiting phenomena for thermal rocket nuclear cores is mass loss of fuel to flowing hydrogen at high temperatures. The hot hydrogen test facility located at the Idaho National Lab (INL) is designed to test suitability of different core materials in 2500°C hydrogen flowing at 1500 liters per minute. The facility is intended to test low activity uranium containing materials but is also suited for testing cladding and coating materials. In this first installment the facility is described. Automated data acquisition, flow and temperature control, vessel compatibility with various core geometries and overall capabilities are discussed.

  9. Charmonium in Hot Medium

    CERN Document Server

    Zhao, Xingbo

    2012-01-01

    We investigate charmonium production in the hot medium created by heavy-ion collisions by setting up a framework in which in-medium charmonium properties are constrained by thermal lattice QCD (lQCD) and subsequently implemented into kinetic approaches. A Boltzmann transport equation is employed to describe the time evolution of the charmonium phase space distribution with the loss and gain term accounting for charmonium dissociation and regeneration (from charm quarks), respectively. The momentum dependence of the charmonium dissociation rate is worked out. The dominant process for in-medium charmonium regeneration is found to be a 3-to-2 process. Its corresponding regeneration rates from different input charm-quark momentum spectra are evaluated. Experimental data on $J/\\psi$ production at CERN-SPS and BNL-RHIC are compared with our numerical results in terms of both rapidity-dependent inclusive yields and transverse momentum ($p_t$) spectra. Within current uncertainties from (interpreting) lQCD data and fr...

  10. Experimental characterization of turbulent superfluid helium

    Science.gov (United States)

    Paoletti, Matthew S.

    Fundamental processes in turbulent superfluid 4He are experimentally characterized by refining a visualization technique recently introduced by Bewley et al.. A mixture of hydrogen and helium gas is injected into the bulk fluid, which produces a distribution of micron-sized hydrogen tracer particles that are visualized and individually tracked allowing for local velocity measurements. Tracer trajectories are complex since some become trapped on the quantized vortices while others flow with the normal fluid. This technique is first applied to study the dynamics of a thermal counterflow. The resulting observations constitute the first direct confirmation of two-fluid motions in He II and provide a quantitative test of the expression for the dependence of the normal fluid velocity, vn, on the applied heat flux, q, derived by L. D. Landau in 1941. Nearly 20,000 individual reconnection events are identified for the first time and used to characterize the dynamics by the minimum separation distance, delta( t), between two reconnecting vortices. Dimensional arguments predict that this separation behaves asymptotically as delta(t) ≈ A(kappa∣t -- t0∣) 1/2, where kappa = h/m is the quantum of circulation. The major finding of the experiments is strong support for this asymptotic form with kappa as the dominant controlling quantity. Nevertheless there are significant event-to-event fluctuations that are equally well fit by two modified expressions: (a) an arbitrary power-law expression delta( t) = B∣t -- t0∣alpha and (b) a correction-factor expression delta(t) = A(kappa∣t -- t 0)1/2 (1 + c∣t -- t0∣). In light of various physical interpretations we regard the correction-factor expression (b), which attributes the observed deviations from the predicted asymptotic form to fluctuations in the local environment and boundary conditions, as best describing the experimental data. The observed dynamics appear statistically time-reversible, suggesting that an effective

  11. Compositional diversity in the atmospheres of hot Neptunes, with application to GJ 436b

    CERN Document Server

    Moses, Julianne I; Visscher, Channon; Richardson, Molly R; Nettelmann, Nadine; Fortney, Jonathan J; Stevenson, Kevin B; Madhusudhan, Nikku

    2013-01-01

    Neptune-sized extrasolar planets that orbit relatively close to their host stars -- often called "hot Neptunes" -- are common within the known population of exoplanets and planetary candidates. Similar to our own Uranus and Neptune, inefficient accretion of nebular gas is expected produce hot Neptunes whose masses are dominated by elements heavier than hydrogen and helium. At high atmospheric metallicities of 10-10,000x solar, hot Neptunes will exhibit an interesting continuum of atmospheric compositions, ranging from more Neptune-like, H2-dominated atmospheres to more Venus-like, CO2-dominated atmospheres. We explore the predicted equilibrium and disequilibrium chemistry of generic hot Neptunes and find that the atmospheric composition varies strongly as a function of temperature and bulk atmospheric properties such as metallicity and the C/O ratio. Relatively exotic H2O, CO, CO2, and even O2-dominated atmospheres are possible for hot Neptunes. We apply our models to the case of GJ 436b, where we find that a...

  12. 76 FR 30362 - Federal Acquisition Regulation; Submission for OMB Review; Acquisition of Helium

    Science.gov (United States)

    2011-05-25

    ... ADMINISTRATION [OMB Control No. 9000-0113; Docket 2011-0079; Sequence 5] Federal Acquisition Regulation; Submission for OMB Review; Acquisition of Helium AGENCY: Department of Defense (DOD), General Services... approved information collection requirement concerning acquisition of helium. Public comments...

  13. The Federal Helium supply: How we got here and where we might be going

    Science.gov (United States)

    Elsesser, Mark

    2015-03-01

    Helium is a limited, non-renewable resource with large uncertainties in both supply and price. It's essential for academic researchers across the physical sciences and engineering disciplines who depend on liquid helium to perform experiments and maintain critical instruments. However, because only about three percent of helium is used for scientific research, academic users have little leverage in the helium marketplace. With the Federal Helium Reserve required to sell off its remaining supply and close its doors within the next decade, many in academia are wondering ``what's next''? I will discuss the history of the Federal Helium Reserve, including legislation that shaped its development, and possibilities going forward. Additionally, I will describe a new APS initiative where we have formed a small consortium of academic liquid helium users and are allowing the Defense Logistics Agency to represent the consortium in liquid helium contract negotiations.

  14. Hot scalar electrodynamics as a toy model for hot QCD

    CERN Document Server

    Krämmer, U; Schulz, H; Kraemmer, Ulrike; Rebhan, Anton K; Schulz, Hermann

    1995-01-01

    Hot scalar electrodynamics is adopted as a toy model for a hot gluon plasma to display some aspects of the compulsory resummation of hard thermal loops when next-to-leading order quantities at soft momentum scales are to be calculated. [Talk given by A.K.R. at a one-day meeting dedicated to the memory of Tanguy ALTHERR, held on November 4, 1994 at CERN, Geneva. To appear in a Gedenkschrift published by World Scientific.

  15. Methods of Helium Injection and Removal for Heat Transfer Augmentation

    Science.gov (United States)

    Haight, Harlan; Kegley, Jeff; Bourdreaux, Meghan

    2008-01-01

    While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives usually involve simulation of an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Cryogenic Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

  16. Sodium dopants in helium clusters: Structure, equilibrium and submersion kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Calvo, F. [Laboratoire Interdisciplinaire de Physique, Rue de La Piscine, Campus Saint Martin d’Hères, 38000 Grenoble (France)

    2015-12-31

    Alkali impurities bind to helium nanodroplets very differently depending on their size and charge state, large neutral or charged dopants being wetted by the droplet whereas small neutral impurities prefer to reside aside. Using various computational modeling tools such as quantum Monte Carlo and path-integral molecular dynamics simulations, we have revisited some aspects of the physical chemistry of helium droplets interacting with sodium impurities, including the onset of snowball formation in presence of many-body polarization forces, the transition from non-wetted to wetted behavior in larger sodium clusters, and the kinetics of submersion of small dopants after sudden ionization.

  17. Detection and Imaging of He_2 Molecules in Superfluid Helium

    CERN Document Server

    Rellergert, W G; Garvan, A; Hanson, J C; Lippincott, W H; Nikkel, J A; McKinsey, D N

    2007-01-01

    We present data supporting our previous proposal [1] for using cycling transitions to detect and image metastable He_2 triplet molecules in superfluid helium. We demonstrate that limitations on the cycling efficiency due to the vibrational structure of the molecule can be mitigated by the use of repumping lasers. Images of the molecules obtained using the method are also shown. This technique gives rise to a new kind of ionizing radiation detector. The use of He_2 triplet molecules as tracer particles in the superfluid promises to be a powerful tool for visualization of both quantum [2-4] and classical [5] turbulence in liquid helium.

  18. Transmission Electron Microscopy Characterization of Helium Bubbles in Aged Plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, A J; Wall, M A; Zocco, T G; Blobaum, K M

    2004-11-02

    The self-irradiation damage generated by alpha decay of plutonium results in the formation of lattice defects, helium, and uranium atoms. Over time, microstructural evolution resulting from the self-irradiation may influence the physical and mechanical properties of the material. In order to assess microstructural changes, we have developed and applied procedures for the specimen preparation, handling, and transmission electron microscopy characterization of Pu alloys. These transmission electron microscopy investigations of Pu-Ga alloys ranging in age up to 42-years old reveal the presence of nanometer-sized helium bubbles. The number density of bubbles and the average size have been determined for eight different aged materials.

  19. Operation of an opamp at liquid helium temperature.

    Science.gov (United States)

    Ng, K.-W.

    1994-02-01

    The stray capacitance between long wires in a cryogenics systems will slow down measurement rate, and also introduce unnecessary noise pick up. It is necessary to install the preamplifier as close to the signal source as possible to diminish the capacitive coupling effects. The most commonly used semiconducting device for this purpose is the MOSFET, which can function at liquid helium temperatures. Under special operation procedures, an all MOSFET operational amplifier can also be operated at liquid helium temperature. The use of opamp will simplify the construction of more complicated circuitry for low temperature applications.

  20. Conductivity change of defective graphene by helium ion beams

    Directory of Open Access Journals (Sweden)

    Yuichi Naitou

    2017-04-01

    Full Text Available Applying a recently developed helium ion microscope, we demonstrated direct nano-patterning and Anderson localization of single-layer graphene (SLG on SiO2/Si substrates. In this study, we clarified the spatial-resolution-limitation factor of direct nano-patterning of SLG. Analysis of scanning capacitance microscopy measurements reveals that the conductivity of helium ion (H+-irradiated SLG nanostructures depends on their geometrical size, i.e., the smaller the H+-irradiated SLG region, the higher its conductivity becomes. This finding can be explained by the hopping carrier transport across strongly localized states of defective SLG.

  1. A Neutron Scattering Study of Collective Excitations in Superfluid Helium

    DEFF Research Database (Denmark)

    Graf, E. H.; Minkiewicz, V. J.; Bjerrum Møller, Hans

    1974-01-01

    Extensive inelastic-neutron-scattering experiments have been performed on superfluid helium over a wide range of energy and momentum transfers. A high-resolution study has been made of the pressure dependence of the single-excitation scattering at the first maximum of the dispersion curve over...... of the multiexcitation scattering was also studied. It is shown that the multiphonon spectrum of a simple Debye solid with the phonon dispersion and single-excitation cross section of superfluid helium qualitatively reproduces these data....

  2. Nanocrystalline silicon prepared at high growth rate using helium dilution

    Indian Academy of Sciences (India)

    Koyel Bhattacharya; Debajyoti Das

    2008-06-01

    Growth and optimization of the nanocrystalline silicon (nc-Si : H) films have been studied by varying the electrical power applied to the helium diluted silane plasma in RF glow discharge. Wide optical gap and conducting intrinsic nanocrystalline silicon network of controlled crystalline volume fraction and oriented crystallographic lattice planes have been obtained at a reasonably high growth rate from helium diluted silane plasma, without using hydrogen. Improving crystallinity in the network comprising ∼ 10 nm Si-nanocrystallites and contributing optical gap widening, conductivity ascending and that obtained during simultaneous escalation of the deposition rate, promises significant technological impact.

  3. The Erosion of Frozen Argon by Swift Helium Ions

    DEFF Research Database (Denmark)

    Besenbacher, F.; Bøttiger, Jørgen; Graversen, O.

    1981-01-01

    The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore unequivo......The temperature, energy, and thickness dependence of the erosion rates of frozen argon films when irradiated with 0.1–3 MeV helium ions have been measured. The erosion yields Y are much too high to be explained by the concentional collisional cascade-sputtering theory and are furthermore...

  4. An investigation of high fractions of metastable helium atoms

    Institute of Scientific and Technical Information of China (English)

    X.P.Feng(冯贤平); B.W.James

    2003-01-01

    Penning type discharge was adopted to excite helium atoms. It is suitable for generating high densitymetastables at a range from 0.1 mTorr to 0.5 Tort. The highest metastable density of 3.5 × 1010 cm-3was observed at a static gas pressure of 0.5 Torr. The highest fraction of metastables (N21s/NHe) of 10-3in a low gas pressure was obtained. The variation of the magnetic field strength on the discharge doesnot result in a significant density change of the metastable helium atoms. When no magnetic field wasapplied, no discharge took place.

  5. A design for a pinhole scanning helium microscope

    Energy Technology Data Exchange (ETDEWEB)

    Barr, M.; Fahy, A. [Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308 (Australia); Jardine, A.; Ellis, J.; Ward, D. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); MacLaren, D.A. [Dept. of Physics, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Allison, W. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Dastoor, P.C., E-mail: Paul.Dastoor@newcastle.edu.au [Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308 (Australia)

    2014-12-01

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

  6. Radioactive core ions of microclusters, ``snowballs`` in superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, N. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Shimoda, T. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Fujita, Y. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Miyatake, H. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Mizoi, Y. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Kobayashi, H. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Sasaki, M. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Shirakura, T. [Osaka Univ., Toyonaka (Japan). Dept. of Physics; Itahashi, T. [Research Center for Nuclear Physics, Osaka Univ., Ibaraki (Japan); Mitsuoka, S. [Research Center for Nuclear Physics, Osaka Univ., Ibaraki (Japan); Matsukawa, T. [Naruto Univ. of Education, Tokushima (Japan); Ikeda, N. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Morinobu, S. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics; Hinde, D.J. [Australian National Univ., Canberra, ACT (Australia). Research School of Physical Sciences; Asahi, K. [Tokyo Inst. of Tech. (Japan). Dept. of Physics; Ueno, H. [Tokyo Inst. of Tech. (Japan). Dept. of Physics; Izumi, H. [Tokyo Inst. of Tech. (Japan). Dept. of Physics

    1996-12-01

    Short-lived beta-ray emitters, {sup 12}B, sustaining nuclear spin polarization were introduced into superfluid helium. The nuclear polarization of {sup 12}B was observed via measurement of beta-ray asymmetry. It was found that the nuclear polarization was preserved throughout the lifetime of {sup 12}B (20.3 ms). This suggests that the ``snowball``, an aggregation of helium atoms produced around an alien ion, constitutes a suitable milieu for freezing-out the nuclear spin of the core ion and that most likely the solidification takes place at the interior of the aggregation. (orig.).

  7. Detectability of Light Dark Matter with Superfluid Helium.

    Science.gov (United States)

    Schutz, Katelin; Zurek, Kathryn M

    2016-09-16

    We show that a two-excitation process in superfluid helium, combined with sensitivity to meV energy depositions, can probe dark matter down to the ∼keV warm dark matter mass limit. This mass reach is 3 orders of magnitude below what can be probed with ordinary nuclear recoils in helium at the same energy resolution. For dark matter lighter than ∼100  keV, the kinematics of the process requires the two athermal excitations to have nearly equal and opposite momentum, potentially providing a built-in coincidence mechanism for controlling backgrounds.

  8. Nucleation, solvation and boiling of helium excimer clusters

    OpenAIRE

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

    2015-01-01

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

  9. Dynamic simulator of helium refrigeration system; Hemiumu reitoki doteki shumyureta

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, H.; Mori, M.; Miyake, A. [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan)

    1999-06-07

    The helium refrigerator has various operation modes. Therefore, it is insufficient for developing the refrigerating machine only by the static simulator, which simulates only one design point. It is necessary to carry out the design, which can deal with the change of the operation mode and construction of the appropriate controllability of the system. The construction of the dynamic simulator is required in the reason. This time, the heat exchanger in the helium refrigerator cool-down was unsteadily analyzed, and it was compared with the measured value. (NEDO)

  10. Inelastic collisions of excited helium atoms with normal rubidium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Blagoev, K.B.; Kasyanenko, S.V.; Krauze, U.; Tolmachev, Y.A.

    1986-05-01

    The afterglow of helium lines in a helium--rubidium mixture excited by a pulsed electron beam has been studied. The effective quenching probabilities at different concentrations of rubidium have been measured, and the rate constants and effective quenching cross sections have been determined. An analysis of possible mechanisms of an inelastic collision is given. A major role of the ionic term in the interaction of the particles during collisions is indicated. The experimental values of the cross sections are compared with the results of a calculation in different approximations.

  11. Small Friends of Hot Jupiters

    Science.gov (United States)

    Nunez, Luis Ernesto; Johnson, John A.

    2017-01-01

    Hot Jupiters are Jupiter-sized gas giant exoplanets that closely orbit their host star in periods of about 10 days or less. Early models hypothesized that these exoplanets formed away from the star, then over time drifted to their characteristically closer locations. However, new theories predict that Hot Jupiters form at their close proximity during the process of core accretion (Batygin et al. 2015). In fact, a super-Earth and a Neptune-sized exoplanet have already been detected in the Hot Jupiter-hosting star WASP-47 (Becker et al. 2015). We will present our analysis of radial velocity time series plots to determine whether low-mass, short-period planets have been previously overlooked in systems of stars which host Hot Jupiters.The SAO REU program is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. 1262851.

  12. Hot dry rock geothermal energy

    Science.gov (United States)

    Heiken, G.; Murphy, H.; Nunz, G.; Potter, R.

    1981-08-01

    Man-made geothermal systems are discussed which make it possible to extract heat from hot rocks in areas where natural fluids are insufficient for the development of hydrothermal energy. The location and magnitude of high- and low-temperature geothermal resources in the USA for such hot dry rock (HDR) systems are examined. An HDR concept is described in which water is injected into one of two nearly parallel wells connected at depth by man-made fractures; the injected water circulates through the fracture system, where it is heated by conduction from the hot rock, and hot fluid, which can be used for heating or for electric power generation, rises through the second well. Some heat-extraction experiments using the described concept are reviewed which are being conducted in a complex volcanic field in New Mexico. The economics of HDR energy is evaluated.

  13. Do scientists trace hot topics?

    Science.gov (United States)

    Wei, Tian; Li, Menghui; Wu, Chensheng; Yan, Xiao-Yong; Fan, Ying; Di, Zengru; Wu, Jinshan

    2013-01-01

    Do scientists follow hot topics in their scientific investigations? In this paper, by performing analysis to papers published in the American Physical Society (APS) Physical Review journals, it is found that papers are more likely to be attracted by hot fields, where the hotness of a field is measured by the number of papers belonging to the field. This indicates that scientists generally do follow hot topics. However, there are qualitative differences among scientists from various countries, among research works regarding different number of authors, different number of affiliations and different number of references. These observations could be valuable for policy makers when deciding research funding and also for individual researchers when searching for scientific projects.

  14. Coulomb explosion of "hot spot"

    CERN Document Server

    Oreshkin, V I; Chaikovsky, S A; Artyomov, A P

    2016-01-01

    The study presented in this paper has shown that the generation of hard x rays and high-energy ions, which are detected in pinch implosion experiments, may be associated with the Coulomb explosion of the hot spot that is formed due to the outflow of the material from the pinch cross point. During the process of material outflow, the temperature of the hot spot plasma increases, and conditions arise for the plasma electrons to become continuously accelerated. The runaway of electrons from the hot spot region results in the buildup of positive space charge in this region followed by a Coulomb explosion. The conditions for the hot spot plasma electrons to become continuously accelerated have been revealed and estimates have been obtained for the kinetic energy of the ions generated by the Coulomb explosion.

  15. Calculations of Electron Structure of Endohedrally Confined Helium Atom with B-Spline Type Functions

    Institute of Scientific and Technical Information of China (English)

    QIAO HaoXue; SHI TingYun; LI BaiWen

    2002-01-01

    The B-spline basis set method is used to study the properties of helium confined endohedrally at thegeometrical centre of a fullerene. The boundary conditions of the wavefunctions can be simply satisfied with thismethod. From our results, the phenomenon of "mirror collapse" is found in the case of confining helium. The interestingbehaviors of confining helium are also discussed.

  16. 43 CFR 16.1 - Agreements to dispose of helium in natural gas.

    Science.gov (United States)

    2010-10-01

    ... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Agreements to dispose of helium in natural gas. 16.1 Section 16.1 Public Lands: Interior Office of the Secretary of the Interior CONSERVATION OF HELIUM § 16.1 Agreements to dispose of helium in natural gas. (a) Pursuant to his authority...

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

    Energy Technology Data Exchange (ETDEWEB)

    Fiering, K.B.; Ryan, S.R. (Arizona Univ., Tucson (USA). Dept. of Physics); Wing, W.H. (Arizona Univ., Tucson (USA). Dept. of Physics; Arizona Univ., Tucson (USA). Optical Sciences Center)

    1982-11-14

    Absolute velocity-resolved total integral cross sections have been measured for collisions of helium singlet (2/sup 1/S/sub 0/) and triplet (2/sup 3/S/sub 1/) metastable (He*) atoms with ground-state helium, neon, and argon atoms in the thermal velocity range of 1.0-3.5x10/sup 5/ cms/sup -1/. Additional measurements on the He*-Ne system with a large input aperture at the detector to suppress the sensitivity of the apparatus to elastic scattering failed to show the previously predicted sharply rising velocity structure in the inelastic excitation transfer cross sections.

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

    Energy Technology Data Exchange (ETDEWEB)

    Fiering, K.B.

    1981-01-01

    Absolute total integral velocity-resolved cross sections have been measured for collisions of helium singlet (2/sup 1/S/sub 0/) and triplet (2/sup 3/S/sub 1/) metastables with ground-state helium, neon, and argon in the thermal velocity range of 1.0 to 3.5 x 10/sup 5/ cm/sec. Additional measurements on the He/sup +/-Ne system with a large input acceptance angle at the detector failed to show previously predicted sharply-rising velocity structure in the inelastic transfer cross sections. The measurements were taken with a crossed-beam time-of-flight apparatus.

  19. a Crossed-Beam Time-Of Study of Metastable Helium in Collisions with Helium, Neon, and Argon.

    Science.gov (United States)

    Fiering, Kenneth Barratt

    Absolute total integral velocity-resolved cross sections have been measured for collisions of helium singlet (2('1)S(,0)) and triplet (2('3)S(,1)) metastables with ground-state helium, neon, and argon in the thermal velocity range of 1.0-3.5 x 10('5) cm/sec. Additional measurements on the He*-Ne system with a large input acceptance angle at the detector failed to show previously predicted sharply -rising velocity structure in the inelastic transfer cross sections. The measurements were taken with a crossed-beam time-of-flight apparatus.

  20. Quantitative spectroscopy of hot stars

    Science.gov (United States)

    Kudritzki, R. P.; Hummer, D. G.

    1990-01-01

    A review on the quantitative spectroscopy (QS) of hot stars is presented, with particular attention given to the study of photospheres, optically thin winds, unified model atmospheres, and stars with optically thick winds. It is concluded that the results presented here demonstrate the reliability of Qs as a unique source of accurate values of the global parameters (effective temperature, surface gravity, and elemental abundances) of hot stars.

  1. Hubble Space Telescope ultraviolet spectroscopy of the hottest known helium-rich pre-white dwarf KPD0005+5106

    CERN Document Server

    Werner, K

    2015-01-01

    We present a model atmosphere analysis of ultraviolet echelle spectra of KPD0005+5106 taken with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. The star is the hottest known pre-white dwarf (Teff = 200,000+-20,000 K, log g = 6.7+-0.3; Wassermann et al. 2010). Its atmosphere is composed of helium with trace amounts of metals. It is of the so-called O(He) spectral type that comprises very hot helium-rich pre-white dwarfs whose origin is debated. From neon and silicon ionisation balances, we derive tighter constraints on the effective temperature (195,000+-15,000 K) and improve previous abundance determinations of these elements. We confirm the idea that KPD0005+5106 is the descendant of an R Coronae Borealis (RCB) star and, hence, is the outcome of a binary-white dwarf merger. We discuss the relation of KPD0005+5106 to other O(He) and RCB stars.

  2. The far-ultraviolet spectra of two hot PG1159 stars

    CERN Document Server

    Werner, K; Kruk, J W

    2016-01-01

    PG1159 stars are hot, hydrogen-deficient (pre-) white dwarfs with atmospheres mainly composed of helium, carbon, and oxygen. The unusual surface chemistry is the result of a late helium-shell flash. Observed element abundances enable us to test stellar evolution models quantitatively with respect to their nucleosynthesis products formed near the helium-burning shell of the progenitor asymptotic giant branch stars. Because of the high effective temperatures (Teff), abundance determinations require ultraviolet spectroscopy and non-local thermodynamic equilibrium model atmosphere analyses. Up to now, we have presented results for the prototype of this spectral class and two cooler members (Teff in the range 85,000-140,000 K). Here we report on the results for two even hotter stars (PG1520+525 and PG1144+005, both with Teff = 150,000 K) which are the only two objects in this temperature-gravity region for which useful far-ultraviolet spectra are available, and revisit the prototype star. Previous results on the a...

  3. High speed pulsed magnetic fields measurements, using the Faraday effect; Mesures de champs magnetiques pulses rapides a l'aide de l'effet Faraday

    Energy Technology Data Exchange (ETDEWEB)

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

    1964-12-01

    For these measures, the information used is the light polarization plane rotation induced by the magnetic field in a glass probe. This rotation is detected using a polarizer-analyzer couple. The detector is a photomultiplier used with high-current and pulsed light. In a distributed magnet (gap: 6 x 3 x 3 cm) magnetic fields to measure are 300 gauss, lasting 0.1 {mu}s, with rise times {<=} 35 ns, repetition rate: 1/s. An oscilloscope is used to view the magnetic field from the P.M. plate signal. The value of the field is computed from a previous static calibration. Magnetic fields from 50 to 2000 gauss (with the probe now used) can be measured to about 20 gauss {+-} 5 per cent, with a frequency range of 30 MHz. (author) [French] Pour faire de telles mesures, on utilise comme information la rotation du plan de polarisation de la lumiere provoquee par le champ magnetique dans une sonde en verre. On detecte cette rotation au moyen d'un polariseur et d'un analyseur, qui sont regles a 45 deg. pour conserver un phenomene lineaire. Le detecteur est un photomultiplicateur travaillant en fort courant en lumiere pulsee. Dans un aimant distribue d'entrefer 6 x 3 x 3 cm, on obtient des champs magnetiques a mesurer de 300 gauss, durant 0.1 {mu}s, avec des temps de montee {<=} 35 ns; au taux de 1 fois par seconde. L'observation du champ se fait sur oscilloscope a partir du signal de plaque du P.M. La valeur absolue du champ est obtenue au moyen d'un etalonnage statique prealable. On peut ainsi mesurer a 20 gauss et {+-} 5 pour cent pres environ des champs magnetiques de 50 a 2000 gauss (avec la sonde actuelle) et avec une bande passante de 30 MHz. (auteur)

  4. Apparatus to measure low level helium for neutron dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Ozaki, Shuji; Takao, Yoshiyuki; Muramasu, Masatomo; Hida, Tomoya; Sou, Hirofumi; Nakashima, Hideki [Kyushu Univ., Fukuoka (Japan); Kanda, Yukinori

    1998-03-01

    An apparatus to measure low level helium in a solid sample for neutron dosimetry in the practical use such as area monitoring in the long-term and reactor surveillance was reported. In our previous work, the helium atoms measurement system (HAMS) was developed. A sample was evaporated in the furnace and the released gas from the sample was analyzed with the mass spectrometer of the system to determine the amount of helium contained in it. The system has been improved to advance the lower helium measurement limit in a solid sample for its application to an area monitoring system. The mass of a solid is up to 100mg. Two important points should be considered to advance the lower limit. One was to produce a high quality vacuum in the system chamber for suppressing background gases during the sample measurement. The other important point was to detect very small output from the mass spectrometer. A pulse counting system was used to get high sensitivity in the mass 4 analyzing. (author)

  5. Solvation of Na+, K+, and their dimers in helium.

    Science.gov (United States)

    An der Lan, Lukas; Bartl, Peter; Leidlmair, Christian; Jochum, Roland; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2012-04-02

    Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so-called snowballs. Calculations suggest that helium atoms in the first solvation layer of these snowballs form rigid structures and that their number (n) is well defined, especially for the lighter alkalis. However, experiments have so far failed to accurately determine values of n. We present high-resolution mass spectra of Na(+)He(n), K(+)He(n), Na(2)(+)He(n) and K(2)(+)He(n), formed by electron ionization of doped helium droplets; the data allow for a critical comparison with several theoretical studies. For sodium and potassium monomers the spectra indicate that the value of n is slightly smaller than calculated. Na(2)(+)He(n) displays two distinct anomalies at n=2 and n=6, in agreement with theory; dissociation energies derived from experiment closely track theoretical values. K(2)(+)He(n) distributions are fairly featureless, which also agrees with predictions.

  6. Helium effects on tungsten surface morphology and deuterium retention

    NARCIS (Netherlands)

    Ueda, Y.; H. Y. Peng,; H. T. Lee,; N. Ohno,; S. Kajita,; Yoshida, N.; Doerner, R.; De Temmerman, G.; V. Alimov,; G. Wright,

    2013-01-01

    Recent experimental results on tungsten surface morphology, especially nano-structure (fuzz), induced by helium plasma exposure at temperatures between 1000 K and 2000 K are reviewed. This structure was firstly reported in 2006. In this review, most of experimental results reported

  7. Microstructure of helium-implanted Nimonic PE16

    Energy Technology Data Exchange (ETDEWEB)

    Czyrska-Filemonowicz, A.; Gadalla, A.A.; Kesternich, W.; Weckermann, B.

    1987-09-01

    Transmission electron microsocpy has been used to investigate the microstructure in Nimonic PE16 after room temperature a-implementation followed by subsequent annealing. Helium bubble formation in the matrix, at dislocations, at grain boundaries and at precipitates of ..gamma..', M/sub 23/C/sub 6/, and MC type has been studied.

  8. On the ground state of a model for compressed helium

    NARCIS (Netherlands)

    Seldam, C.A. ten; Groot, S.R. de

    1952-01-01

    In the problem of the “compressed helium atom”, the boundary condition that the wave function ψ must vanish at infinity (r = ∞), is replaced by: ψ = 0 at a finite r = r0. This problem is solved by a variational method, which for the limiting case of the free atom (r0 → ∞) coincides with one of Hylle

  9. Impulsive Laser Induced Alignment of Molecules Dissolved in Helium Nanodroplets

    DEFF Research Database (Denmark)

    Pentlehner, Dominik; H. Nielsen, Jens; Slenczka, Alkwin

    2013-01-01

    We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (CH3I) molecules dissolved in a helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than that of isolated molecule...

  10. The Helium Atom and Isoelectronic Ions in Two Dimensions

    Science.gov (United States)

    Patil, S. H.

    2008-01-01

    The energy levels of the helium atom and isoelectronic ions in two dimensions are considered. The difficulties encountered in the analytical evaluation of the perturbative and variational expressions for the ground state, promote an interesting factorization of the inter-electronic interaction, leading to simple expressions for the energy. This…

  11. Field Ionization detection of supersonic helium atom beams

    Science.gov (United States)

    Doak, R. B.

    2003-10-01

    Field ionization detectors (FID) may offer near-unity detection efficiency and nanoscale spatial resolution. To date, FID detection of molecular beams has been limited to effusive beams of broad Maxwellian velocity distributions. We report FID measurements on monoenergetic helium beams, including intensity measurements and time-of-flight measurements. The FID tips were carefully prepared and characterized in a field ionization microscope prior to use. With the supersonic helium beam we find a much smaller effective detection area ( 50 sq. nm) than was reported in the effusive helium beam experiments ( 200,000 sq. nm). This suggests that the FID ionization yield depends strongly on energy loss by the impinging atom during its initial collision with the FID surface: Our thermal energy, monoenergetic helium beam atoms likely lose little or no energy upon scattering from the clean tungsten FID surface, allowing the scattered atoms to escape the FID polarization field and therby reducing the ionization yield. To improve signal levels, inelastic scattering might be enhanced by use of lower beam velocities (present in the tails of a Maxwellian) or by adsorbing an overlayer on the FID tip (present at cryogenic tip temperatures). These factors likely explain the higher detection yields measured in the effusive beam experiments.

  12. Molecular Iodine Fluorescence Using a Green Helium-Neon Laser

    Science.gov (United States)

    Williamson, J. Charles

    2011-01-01

    Excitation of molecular iodine vapor with a green (543.4 nm) helium-neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature…

  13. Sputtering of solid nitrogen by keV helium ions

    DEFF Research Database (Denmark)

    Ellegaard, O.; Schou, Jørgen; Sørensen, H.;

    1993-01-01

    Solid nitrogen has become a standard material among the frozen molecular gases for electronic sputtering. We have combined measurements of sputtering yields and energy spectra from nitrogen bombarded by 4-10 keV helium ions. The data show that the erosion is electronic rather than knockon...

  14. Measurement of strong interaction effects in antiprotonic helium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Davies, J.D.; Gorringe, T.P.; Lowe, J.; Nelson, J.M.; Playfer, S.M.; Pyle, G.J.; Squier, G.T.A. (Birmingham Univ. (UK). Dept. of Physics); Baker, C.A.; Batty, C.J.; Clark, S.A.

    1984-09-27

    The strong interaction shift and width for the 2 p level and the width for the 3d level have been measured for antiprotonic helium atoms. The results are compared with optical model calculations. The possible existence of strongly bound antiproton states in nuclei is discussed.

  15. Impulsive Laser Induced Alignment of Molecules Dissolved in Helium Nanodroplets

    DEFF Research Database (Denmark)

    Pentlehner, Dominik; H. Nielsen, Jens; Slenczka, Alkwin

    2013-01-01

    We show that a 450 fs nonresonant, moderately intense, linearly polarized laser pulse can induce field-free molecular axis alignment of methyliodide (CH3I) molecules dissolved in a helium nanodroplet. Time-resolved measurements reveal rotational dynamics much slower than that of isolated molecule...

  16. Transport and extraction of radioactive ions stopped in superfluid helium

    NARCIS (Netherlands)

    Huang, WX; Dendooven, P; Gloos, K; Takahashi, N; Arutyunov, K; Pekola, JP; Aysto, J

    2003-01-01

    A new approach to convert a high energy beam to a low energy one, which is essential for the next generation radioactive ion beam facilities, has been proposed and tested at Jyvaskyla, Finland. An open Ra-223 alpha-decay-recoil source has been used to produce radioactive ions in superfluid helium. T

  17. Experimental studies of amplification using evaporation and adsorption of helium

    Energy Technology Data Exchange (ETDEWEB)

    More, T. [Brown Univ., Providence, RI (United States). Dept. of Physics; Adams, J.S. [Brown Univ., Providence, RI (United States). Dept. of Physics; Bandler, S.R. [Brown Univ., Providence, RI (United States). Dept. of Physics; Brouer, S.M. [Brown Univ., Providence, RI (United States). Dept. of Physics; Lanou, R.E. [Brown Univ., Providence, RI (United States). Dept. of Physics; Maris, H.J. [Brown Univ., Providence, RI (United States). Dept. of Physics; Seidel, G.M. [Brown Univ., Providence, RI (United States). Dept. of Physics

    1996-02-11

    The design of a phonon amplifier based on the evaporation of helium atoms from a superfluid film and their adsorption onto a bare solid surface is discussed. Experimental results indicate that substantial improvement in efficiency is required to be able to construct such an amplifier. A possible modification to achieve this improvement is considered. (orig.).

  18. Projected performance of a large superfluid helium solar neutrino detector

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Enss, C.; Goldhaber, G.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M. (Brown Univ., Providence, RI (United States))

    1993-11-01

    Based upon experiments carried out using radioactive sources to investigate the particle detection properties of superfluid helium the authors project a configuration for and the response of a full scale detector for solar neutrinos employing the roton/quantum evaporation technique.

  19. A catalogue of helium abundance indicators from globular cluster photometry

    Science.gov (United States)

    Sandquist, Eric L.

    2000-04-01

    We present a survey of helium abundance indicators derived from a comprehensive study of globular cluster photometry in the literature. For each of the three indicators used, we conduct a thorough error analysis, and identify systematic errors in the computational procedures. For the population ratio RNHBNRGB, we find that there is no evidence of a trend with metallicity, although there appears to be real scatter in the values derived. Although this indicator is the one best able to provide useful absolute helium abundances, the mean value is Y~0.20, indicating the probable presence of additional systematic error. For the magnitude difference from the horizontal branch to the main sequence Δ and the RR Lyrae mass-luminosity exponent A, it is only possible to determine relative helium abundances reliably. This is due to continuing uncertainties in the absolute metallicity scale for Δ, and uncertainty in the RR Lyrae temperature scale for A. Both indicators imply that the helium abundance is approximately constant as a function of [Fe/H]. According to the A indicator, both Oosterhoff I and II group clusters have constant values independent of [Fe/H] and horizontal branch type. In addition, the two groups have slopes dlog/d[Fe/H] that are consistent with each other, but significantly smaller than the slope for the combined sample.

  20. Direct Three-body Triple-$\\alpha$ in Helium Novae

    CERN Document Server

    Connolly, Ryan; Brown, Edward F

    2016-01-01

    In AM CVn binaries, a white dwarf primary accretes material from a helium-rich white dwarf or stellar companion. The unstable ignition of nuclear burning via the $3\\alpha$ reaction in an accumulated helium layer powers a thermonuclear runaway near accretion rates $\\dot{M} \\lesssim 10^{-6} \\, \\mathrm{M_{\\odot} \\ yr^{-1}}$ that may be observed as helium nova or .Ia supernova. Helium burning in the primary's envelope at temperatures $T \\lesssim 10^{8} \\, \\mathrm{K}$ may proceed via the direct three-body fusion of $\\alpha$-particles. Here we show that the direct three-body rate by Nguyen et al. (2012) -- which is reduced relative to the extrapolated resonant rate at temperatures $T \\gtrsim 5 \\times 10^{7} \\, \\mathrm{K}$ -- results in novae with longer recurrence times and larger ignition masses. By contrast, we find that the enhancement in the direct three-body rate at temperatures below $T \\lesssim 5 \\times 10^{7} \\, \\mathrm{K}$ does not result in significant differences in nova outburst properties. The most mas...