WorldWideScience
 
 
1

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

International Nuclear Information System (INIS)

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

1982-01-01

2

Effects of helium on void swelling in boron doped V-5Fe alloys  

International Nuclear Information System (INIS)

The effects of helium on void swelling in V-5Fe were investigated with natural boron-doping techniques during FFTF/MOTA (fast flux test facility/materials open test assembly) irradiation. Microstructural observation was carried out to understand the swelling behavior obtained from density measurements. The cavity size distribution in V-5Fe-xB (x = 0, 100, and 500 appm) irradiated at temperatures lower than 713 K indicates a suppressant effect of helium on void growth, and an enhancing effect on cavity nucleation. Since the chemical effect of boron addition is competitive with the transmutation effect, the results have been compared with that of the dual ion irradiation experiments to allow separation of the effect of helium from the effect of boron. (orig.)

1998-01-01

3

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

UK PubMed Central (United Kingdom)

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

Scholder O; Jefimovs K; Shorubalko I; Hafner C; Sennhauser U; Bona GL

2013-09-01

4

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

Science.gov (United States)

We demonstrate a reliable fabrication method to produce plasmonic dipole nanoantennas with gap values in the range of 3.5-20 nm. The method combines electron beam lithography to create gold nanorods and helium focused ion beam milling to cut the gaps. Results show a reproducibility within 1 nm. Scattering spectra of antennas show a red shift of resonance wavelengths and an increase of the intensity of resonance peaks with a decrease of the gap size, which is in agreement with finite element simulations. The measured refractive index sensitivity was about 250 nm per refractive index unit for antennas with gap values below 5 nm. PMID:24013454

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

2013-09-06

5

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

UK PubMed Central (United Kingdom)

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

Scholder O; Jefimovs K; Shorubalko I; Hafner C; Sennhauser U; Bona GL

2013-10-01

6

Emission spectrum of the C sub 2 radical embedded in superfluid helium around 1.5 K  

CERN Multimedia

The C sub 2 d sup 3 PI sub g -a sup 3 PI sub u (upsilon' - upsilon'') Swan band emission spectrum induced by the laser ablation of graphite in the superfluid helium around 1.5 K, was observed. Only the vibrational progression of DELTA upsilon = upsilon' - upsilon'', where DELTA upsilon less than 0 are observed, indicating fast (tau < 100 ns) vibrational relaxation in superfluid helium. This result also indicates a unique characteristic of superfluid helium as a circumstance of chemical processes. (author)

Wada, A

2003-01-01

7

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

International Nuclear Information System (INIS)

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

1996-01-01

8

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

International Nuclear Information System (INIS)

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

2012-01-01

9

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

Energy Technology Data Exchange (ETDEWEB)

The alloy V-15Cr-5Ti was cyclotron-implanted with 80 appM He and subsequently irradiated in the Experimental Breeder Reactor (EBR-II) to 30 dpa. The same alloy was also irradiated in the 10, 20, and 30% cold-worked conditions. Irradiation temperatures ranged from 400 to 700/sup 0/C. No significant effects of helium on mechanical properties were found in this temperature range although the neutron irradiation shifted the temperature of transition from cleavage to ductile fracture to about 625/sup 0/C. Ten percent cold work was found to have a beneficial effect in reducing the tendency for cleavage fracture following irradiation, but high levels (20%) were observed to reduce ductility. Still higher levels (30%) improved ductility by inducing recovery during the elevated-temperature irradiation. Swelling was found to be negligible, but precipitates - titanium oxides or carbonitrides - contained substantial cavities.

Grossbeck, M.L.; Horak, J.A.

1986-01-01

10

Cryosorption pumping of helium at 4.2 K by type 5A molecular sieve  

International Nuclear Information System (INIS)

[en] Experimental results are given for helium pumping as a function of loading for three runs in the low-feed-rate pumping regime (Q less than 2 x 10-3 torr-liter/sec). Another figure shows helium pumping speeds for feed rates exceeding 2 x 10-3 torr-liter/sec. Each of these runs begins with an initial speed near 650 liters/sec

1977-06-17

11

The Greenwood-Foreman-Rimmer loop punching mechanism as applied to helium bubble growth in nickel implanted with 5 keV He+ ions at 273 K  

International Nuclear Information System (INIS)

It is shown that as a result of the Greenwood-Foreman-Rimmer loop punching mechanism applied for helium bubble growth in nickel implanted with 5 keV He+ ions at 273 K, a considerable amount of helium remains outside the bubbles which are visible in a transmission electron microscope (TEM). It is also shown that even when it is assumed that there is an energy barrier with an upper limit equal to the formation energy of a self-interstitial atom, not all implanted helium can be accumulated in the bubbles below the critical dose for blistering. The experimental observation of bubble growth in a helium pre-implanted nickel specimen during 1 MeV e- irradiation may demonstrate that indeed a significant amount of helium remains between the bubbles visible in TEM. (author).

1983-01-01

12

Greenwood-Foreman-Rimmer loop punching mechanism as applied to helium bubble growth in nickel implanted with 5 keV He/sup +/ ions at 273 K  

Energy Technology Data Exchange (ETDEWEB)

It is shown that as a result of the Greenwood-Foreman-Rimmer loop punching mechanism applied for helium bubble growth in nickel implanted with 5 keV He/sup +/ ions at 273 K, a considerable amount of helium remains outside the bubbles which are visible in a transmission electron microscope (TEM). It is also shown that even when it is assumed that there is an energy barrier with an upper limit equal to the formation energy of a self-interstitial atom, not all implanted helium can be accumulated in the bubbles below the critical dose for blistering. The experimental observation of bubble growth in a helium pre-implanted nickel specimen during 1 MeV e/sup -/ irradiation may demonstrate that indeed a significant amount of helium remains between the bubbles visible in TEM.

Swygenhoven, H. van; Stals, L.M. (Limburgs Universitair Centrum (Belgium))

1983-11-01

13

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

International Nuclear Information System (INIS)

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

1975-09-29

14

Helium localisation in tritides  

International Nuclear Information System (INIS)

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

1982-06-11

15

Effect of helium and DPA's on tensile properties of V-5Ti and V-3Ti-1Si  

International Nuclear Information System (INIS)

Specimens of the alloys V-5Ti and V-3Ti-1Si were irradiated in a mixed-spectrum fission reactor in reactor grade liquid sodium to a fast neutron fluence of 3.8 x 1025m-2 (E>0.1 MeV), which corresponds to 6.2 dpa. Irradiation temperatures were 500, 600 and 700 deg C. Some of the specimens were pre-injected with helium to 100 appm at approx 50 deg C by means of a cyclotron. In addition, part of the specimens were doped with boron-10 to concentrations of 100 and 600 appm. Tensile testing, at temperatures equal to the irradiation temperatures and at a strain rate of 10-4 s-1, showed an increase in strength and reduced elongation at 500 deg C and to a lesser extent at 600 deg C. These changes are caused by displacement damage. Helium, pre-injected as well as produced by transmutation of boron-10, did not have a significant influence on the tensile properties. Cavities seen in the irradiated materials at low concentrations, were not preferentially located on grain boundaries. There was no apparent deleterious effect of lithium, which is also a transmutation product of boron-10. (author). 12 refs.; 8 figs.; 3 tabs.

1991-01-01

16

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

CERN Multimedia

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

Gruehagen, Henning

2005-01-01

17

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

International Nuclear Information System (INIS)

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

1983-01-01

18

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

UK PubMed Central (United Kingdom)

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

Edwards AA; Lloyd DC; Prosser JS; Finnon P; Moquet JE

1986-07-01

19

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

At low magnetic field, metastability exchange optical pumping of helium-3 is known to provide high nuclear polarizations for pressures around 1 mbar. In a recent paper, we demonstrated that operating at 1.5 T can significantly improve the results of metastability exchange optical pumping at high pre...

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

20

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

We perform metastability exchange optical pumping of helium-3 in a strong magnetic field of 1.5 T. The achieved nuclear polarization, from 80% at 1.33 mbar to 25% at 67 mbar, shows a substantial improvement at high pressures with respect to standard low-field optical pumping. The specific mechanisms...

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

 
 
 
 
21

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-04-01

22

Effect of helium and fission neutrons on the tensile properties of v-5Ti  

International Nuclear Information System (INIS)

Tensile specimens of vanadium alloy V-5Ti, doped with 100 appm 10B, were irradiated to a fast fluence of 4.2 x 1025 m-2 (E > 0.1 MeV), corresponding to 4.5 dpa, and a thermal fluence of 1.9 x 1025 m-2. During irradiation, the specimens were exposed to Na at the temperatures 490, 580 and 6700C. Reference specimens were also exposed to Na at these temperatures. Results of tensile tests, performed at temperatures equal to the respective annealing and irradiation temperatures, showed that at 580 and 6700C neither displacement damage nor the generated He, due to transmutation of 10B, had much influence on the tensile properties of the alloy. At 4900C irradiation produced defects increased, the strength properties and decreased the ductility by about 50%

1987-01-01

23

Evaluation helium release behavior in MOX fuel  

International Nuclear Information System (INIS)

The amount of helium gas released from MOX fuel pellets was measured by a puncturing test and the amount of helium gas generation in MOX fuel irradiated in the fast reactor 'Joyo' was calculated. We evaluated the helium gas release behavior and the influence of helium gas on internal pressure in MOX fuel using on the above data. In the case of MOX fuel, the influence of helium gas on internal pressure of the fuel pins was estimated at 5% at burn-up of around 150 GWd/t. Minor actinides fuels contained about 5 wt% 241Am, but helium gas was estimated at 20 - 30% of all the gases in the fuel pin because the amount of helium gas generated by TRU's a decay was increased. Therefore, the influence of helium gas release should be taken into consideration for designing the fuel pin. (author)

1999-01-01

24

Small scale helium liquefaction systems  

International Nuclear Information System (INIS)

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

2009-02-01

25

Helium production in natural gas reservoirs  

Energy Technology Data Exchange (ETDEWEB)

About 11,000 published natural gas analyses of helium are used in the estimation of the average global scale accumulation and concentration of radiogenic helium in sediments. Simple lognormal statistics is employed to derive a net accumulation rate between 1dagger10/sup 5/ to 6.7dagger10/sup 5/ helium atoms per cubic meter of reservoir rock per second. This acccumulation rate permitted to infer an average helium concentration of nonreservoir sediments of about 67 ppm. By assuming a simple closed system model it is shown that deep seated sources of helium are not necessary to explain the present regime of helium in sediments on a global scale. Helium accumulation rates and concentrations obtained by this method are in close agreement with existing fundamental geochemical estimates of uranium and thorium in rather average type sediments.

Pereira, E.B.; Adams, J.A.S.

1982-01-01

26

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

International Nuclear Information System (INIS)

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

1976-01-01

27

Helium cooled nuclear reactors  

International Nuclear Information System (INIS)

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

1976-01-01

28

Primitive helium in diamonds.  

UK PubMed Central (United Kingdom)

Thirteen diamond stones from various unspecified mines in South Africa were analyzed for the isotopic ratio of helium-3 to helium-4. Values of the ratio ranged from less than 10(-7) to (3.2 +/- 0.25) x 10(-4). The latter value is higher than the primordial helium-3/helium-4 ratio in meteorites and close to the ratio for solar-type helium. Such extremely high values may represent primitive helium that evolved very little (that is, showed very little increase in radiogenic helium-4) since the formation of the earth.

Ozima M; Zashu S

1983-03-01

29

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

CERN Document Server

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

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

2010-01-01

30

Ionized helium afterglow study  

International Nuclear Information System (INIS)

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

1976-01-01

31

Helium behaviour in nuclear glasses  

International Nuclear Information System (INIS)

[en] The present thesis focuses on the study of helium behavior in R7T7 nuclear waste glass. Helium is generated by the minor actinides alpha decays incorporated in the glass matrix. Therefore, four types of materials were used in this work. These are non radioactive R7T7 glasses saturated with helium under pressure, glasses implanted with 3He+ ions, glasses doped with curium and glasses irradiated in nuclear reactor. The study of helium solubility in saturated R7T7 glass has shown that helium atoms are inserted in the glass free volume. The results yielded a solubility of about 1016 at. cm-3 atm.-1. The incorporation limit of helium in this type of glass has been determined; its value amounted to about 2*1021 at. cm-3, corresponding to 2.5 at.%. Diffusion studies have shown that the helium migration is controlled by the single population dissolved in the glass free volume. An ideal diffusion model was used to simulate the helium release data which allowed to determine diffusion coefficients obeying to the following Arrhenius law: D = D0exp(-Ea/kBT), where D0 = 2.2*10-2 and 5.4*10-3 cm2 s-1 and Ea = 0.61 eV for the helium saturated and the curium doped glass respectively. These results reflect a thermally activated diffusion mechanism which seems to be not influenced by the glass radiation damage and helium concentrations studied in the present work (up to 8*1019 at. g-1, corresponding to 0.1 at.%). Characterizations of the macroscopic, structural and microstructural properties of glasses irradiated in nuclear reactor did not reveal any impact associated with the presence of helium at high concentrations. The observed modifications i.e. a swelling of 0.7 %, a decrease in hardness by 38 %, an increase between 8 and 34 % of the fracture toughness and a stabilization of the glass structure under irradiation, were attributed to the glass nuclear damage induced by the irradiation in reactor. Characterizations by SEM and TEM of R7T7 glasses implanted with helium at high concentrations, doped with curium and irradiated in nuclear reactor showed a homogeneous microstructure free of helium bubbles, pores or cracking. The results of the present work were used to develop a long-term diffusion model of helium in an industrial R7T7 nuclear waste glass. The model considers the thermal history, the fracturing and the alpha activity of the glass. (author)[fr] Cette these s'interesse au comportement de l'helium dans le verre nucleaire de type R7T7, l'helium etant genere par les desintegrations alpha des actinides mineurs incorpores dans la matrice vitreuse. Pour cela, quatre types de materiaux ont ete utilises dans ce travail, a savoir des verres R7T7 inactifs infuses par de l'helium sous pression, des verres implantes par des ions 3He+, des verres dopes au curium et des verres irradies en reacteur. L'etude de la solubilite de l'helium par infusion dans le verre R7T7 a permis de montrer que l'helium s'insere dans le volume libre du verre et indique une valeur d'environ 1016 at. cm-3 atm.-1. La limite d'incorporation de l'helium dans ce type de verre a egalement ete determinee; sa valeur s'eleve a environ 2*1021 at. cm-3, soit 2.5 %at. Les etudes de diffusion ont montre que la migration de l'helium est controlee par la seule population d'helium dissoute dans le volume libre du verre. Les donnees de relachement qui ont pu etre traitees par un modele de diffusion classique, indiquent des coefficients de diffusion obeissant a la loi d'Arrhenius suivante: D = D0exp(-Ea/kBT), avec D0 = 2,2*10-2 et 5,4*10-3 cm2 s-1 et Ea = 0,61 eV pour les verres infuses et les verres dopes au curium respectivement. Ces resultats traduisent un mecanisme de diffusion thermiquement active qui ne semble pas etre influence par l'endommagement du verre ni par les fortes teneurs en helium etudiees dans ce travail (jusqu'a 8*1019 at. g-1 soit 0,1 %at.). Les caracterisations des proprietes macroscopiques, structurales et microstructurales des verres irradies en reacteur n'ont pas revele d'impact lie a la presence d'helium a fortes teneurs. Les modifications o

2011-01-01

32

Standard Guide for Simulation of Helium Effects in Irradiated Metals  

CERN Document Server

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

American Society for Testing and Materials. Philadelphia

1996-01-01

33

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

International Nuclear Information System (INIS)

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

2000-01-01

34

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

International Nuclear Information System (INIS)

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

2005-01-01

35

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

Energy Technology Data Exchange (ETDEWEB)

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

ARD, K.E.

2000-04-19

36

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

International Nuclear Information System (INIS)

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

1996-01-01

37

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

International Nuclear Information System (INIS)

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

1998-01-01

38

Counting Individual Electrons on Liquid Helium  

CERN Document Server

We show that small numbers of electrons, including a single electron, can be held in a novel electrostatic trap above the surface of superfluid helium. A potential well is created using microfabricated electrodes in a 5 micron diameter pool of helium. Electrons are injected into the trap from an electron reservoir on a helium microchannel. They are individually detected using a superconducting single-electron transistor (SET) as an electrometer. A Coulomb staircase is observed as electrons leave the trap one-by-one until the trap is empty. A design for a scalable quantum information processor using arrays of electron traps is presented

Papageorgiou, G

2004-01-01

39

Metal tritides helium emission  

International Nuclear Information System (INIS)

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

1980-01-01

40

Helium-3 from the mantle: primordial signal or cosmic dust?  

UK PubMed Central (United Kingdom)

Helium-3 in hotspot magmas has been used as unambiguous evidence for the existence of a primordial, undegassed reservoir deep in the Earth's mantle. However, a large amount of helium-3 is delivered to the Earth's surface by interplanetary dust particles (IDPs). Recycling of deep-sea sediments containing these particles to the mantle, and eventual incorporation in magma, can explain the high helium-3/helium-4 ratios of hotspot magmas. Basafts with high helium-3/helium-4 ratios may represent degassing of helium introduced by ancient (probably 1.5 to 2.0 billion years old) pelagic sediments rather than degassing of primordial lower mantle material brought to the surface in plumes. Influx of IDPs can also explain the neon and siderophile compositions of mantle samples.

Anderson DL

1993-07-01

 
 
 
 
41

Helium dilution refrigerator  

International Nuclear Information System (INIS)

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

1973-01-01

42

Helium purification system  

Energy Technology Data Exchange (ETDEWEB)

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

Asahara, Kazuhiko; Taneda, Masanobu (Kobe Steel Ltd. (Japan))

1989-07-01

43

The Primordial Helium Abundance  

CERN Multimedia

I present a brief review on the determination of the primordial helium abundance by unit mass, Yp. I discuss the importance of the primordial helium abundance in: (a) cosmology, (b) testing the standard big bang nucleosynthesis, (c) studying the physical conditions in H II regions, (d) providing the initial conditions for stellar evolution models, and (e) testing the galactic chemical evolution models.

Peimbert, Manuel

2008-01-01

44

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

International Nuclear Information System (INIS)

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

1989-01-01

45

Line ratio diagnostics in helium and helium seeded argon plasmas  

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-08-15

46

The diffusion of helium in bcc and hexagonal metals  

International Nuclear Information System (INIS)

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

1990-01-01

47

The helium purification system of the HTR-10  

Energy Technology Data Exchange (ETDEWEB)

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

Yao, M.S. E-mail: yaoms@mail.tsinghua.edu.cn; Wang, R.P.; Liu, Z.Y.; He, X.D.; Li, J

2002-10-01

48

Superfluid helium IV hydrodynamics  

International Nuclear Information System (INIS)

[en] Various experiments on the hydrodynamics of superfluid helium IV are presented: study of persistent currents, flow through a small hole, superfluid and normal fluid turbulence in a heat flow experiment[fr] Presentation de quelques experiences sur l'hydrodynamique de l'helium IV superfluide: etude des courants permanents, ecoulements a travers un petit trou, turbulence du superfluide et du fluide normal dans une experience d'ecoulement de chaleur

1975-06-30

49

High-resolution measurements of the pressure broadening and shift of the rubidium 5 2S1/2-6 2P3/2 line by argon and helium  

International Nuclear Information System (INIS)

We present results of the pressure broadening and shift of the rubidium 5s 2S1/2-6p 2P3/2 (420.2 nm) spectral line by argon and helium buffer gases at pressures below 10 torr. High-resolution absorption measurements were performed with a single-mode external cavity diode laser, having 20-GHz tuning range and a linewidth of about 1 MHz. Pressure broadening and shift parameters of Lorentzian hyperfine components have been determined. We obtained the redshift of hyperfine spectral lines for He and the blueshift for Ar.

2004-01-01

50

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

Energy Technology Data Exchange (ETDEWEB)

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

LEW, B.S.

2000-03-27

51

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

International Nuclear Information System (INIS)

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

2000-01-01

52

THERMAL UNIFORMITY OF LIQUID HELIUM IN ELECTRON BUBBLE CHAMBER.  

Energy Technology Data Exchange (ETDEWEB)

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.

WANG,L.; JIA,L.

2002-07-22

53

Superfluid helium acoustic microscopy  

Energy Technology Data Exchange (ETDEWEB)

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

Foster, J.S.

1984-01-01

54

Tritium/Helium-3 Dating  

Science.gov (United States)

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

55

Structure of helium and neon in zeolite  

Energy Technology Data Exchange (ETDEWEB)

We have measured the structure of helium and neon adsorbed in zeolite 13X at temperatures in the range 5.5--80 K. No evidence for bulklike liquid or solid behavior is observed for the temperatures studied. Instead, both the He and Ne atoms adsorb into well-defined sites in the zeolite structure. The sites occupied appear to be the same for He and Ne and are consistent with the adsorption sites previously identified for {ital D}{sub 2} in 13X. We have also measured the dependence of the structure on pore filling for helium over a limited range of filling.

Fang, M.P.; Sokol, P.E. [Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

1995-11-01

56

Helium solubility and bubble growth in metals under high pressure  

International Nuclear Information System (INIS)

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

1985-01-01

57

Helium-refrigeration system  

Energy Technology Data Exchange (ETDEWEB)

The design, procurement, and preliminary construction was completed for adding two more wet expansion engines to two helium refrigerators. These will be added in mid-year FY 1995. In addition a variable speed drive will be added to an existing helium compressor. This is part of an energy conservation upgrade project to reduce operating costs from the use of electricity and liquid nitrogen. This project involves the replacement of Joule-Thompson valves in the refrigerators with expansion engines resulting in system efficiency improvements of about 30% and improved system reliability.

Specht, J.R.; Millar, B.; Sutherland, A.

1995-08-01

58

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

International Nuclear Information System (INIS)

The High Temperature Helium Loop (HTHL) is an experimental device for simulation of VHTR helium coolant conditions. The purpose of the HTHL is structural materials testing and helium coolant chemistry investigation. In the HTHL pure helium will be used as working medium and its main physical parameters are 7 MPa, max. temperature in the test section 900 °C and flow rate 37.8 kg/h. The HTHL consists of an active channel, the helium purification system, the system of impurities dosage (e.g. CO, CO2, H2, H2O, O2, N2, and CH4) and the helium chemistry monitoring system (sampling and on-line analysis and determination of impurities in the helium flow). The active channel is planned to be placed into the core of the experimental reactor LVR-15 which will serve as a neutron flux source (max. 2.5 × 1018 n/m2 s for fast neutrons). The HTHL is now under construction. Some of its main parts are finished, some are still being produced (active channel internals, etc.), some should be improved to work correctly (the helium circulatory compressor); certain sub-systems are planned to be integrated to the loop (systems for the determination of moisture and other impurities in helium, etc.). The start of the HTHL operation is expected during 2011 and the integration of the active channel into the LVR-15 core during 2012.

2012-01-01

59

Physics of helium 4, helium 3 and their mixtures  

International Nuclear Information System (INIS)

The knowledo.e is summed up on the physical properties of helium isotopes. The most significant property of helium II is its superfluidity. The so-called two-component theory of helium II may be formalized from the energy spectra shape and using the Bose-Einstein distribution function. At temperatures less than 0.05 K liquid helium 3 has properties quantitatively analogic to the Fermi ideal gas. At temperatures lower than 2.6 mK superfluid helium 3 phases were discovered whose existence was proved by the measurement of specific heat, viscosity, and thermal resistance. A liquid mixture of helium 3 and helium 4 increases the heat capacity of He 4 and increases the number of centres therein for excitations. Solid helium 4 was investigated up to pressures of 1,414 MPa and temperatures of 77.3 K, solid helium 3 was investigated up to pressures of 350 HPa and temperatures of 30.533 K. The phase diagrams of the two isotopes in the solid state are very similar. The Debye temperature changes within 15 and 100 K depending on the molar volume. The helium 4 minimum on the melting curve is at a temperature of 0.775 K while that of helium 3 at 0.318 K. The study of He 3 and He 4 solid mixtures is very important for the general theory of quantum crystals. (J.B.)

1974-09-02

60

Helium leak finding plant  

International Nuclear Information System (INIS)

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

1986-05-15

 
 
 
 
61

Liquid helium level detector  

Energy Technology Data Exchange (ETDEWEB)

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

Charrier, G.; Dupont, H. (C.E.A. D.A.M., 92 - Montrouge (France))

1984-04-01

62

Cosmological helium production simplified  

International Nuclear Information System (INIS)

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

1988-01-01

63

Helium Neon Laser  

Science.gov (United States)

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

Group, Kansas S.; Zollman, Dean A.

2004-03-05

64

Helium refrigerator for 'SULTAN'  

International Nuclear Information System (INIS)

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

1984-01-01

65

Laser Spectroscopic Measurement of Helium Isotope Ratios  

CERN Document Server

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

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

2003-01-01

66

Helium ion bombardment of thin aluminium films  

Energy Technology Data Exchange (ETDEWEB)

A study is presented of the effect of 5 keV helium ion bombardment on thin (about 2000 A) aluminium films using proton backscattering, scanning and transmission electron microscopy and ..cap alpha.. particle energy loss spectroscopy. Measurements of helium content after irradiation using proton backscattering indicate low below-saturation retention for both room temperature and low temperature implantations (19% and 24% respectively). Electron microscopy examination of the films reveals a severe deformation in the form of coarse and fine-scale wrinkling whose amplitude increases with increasing helium dose. This deformation does not appear to be the result of bubble swelling. An attempt has been made to quantify the wrinkling by measuring the energy loss spectrum of ..cap alpha.. particles transmitted through irradiated films and the combination of these measurements with a simple sinusoidal deformation model indicates an increase in film area of up to 20%.

Donnelly, S.E.; Bodart, F. (Facultes Universitaires Notre-Dame de la Paix, Namur (Belgium)); Barfoot, K.M.; Werz, R. (Commission of the European Communities, Geel (Belgium). Central Bureau for Nuclear Measurements); Webb, R.P. (Salford Univ. (UK))

1982-08-27

67

Superfluid helium as a dark matter detector  

International Nuclear Information System (INIS)

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

1988-01-01

68

Helium Background in the D0 Detector Related to the Photomultiplier Tubes  

Energy Technology Data Exchange (ETDEWEB)

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

Rucinski, R.; /Fermilab

1998-04-09

69

Helium stars as supernova progenitors  

CERN Multimedia

We follow the evolution of helium stars of initial mass $(2.2 - 2.5) M_\\odot$, and show that they undergo off-center carbon burning, which leaves behind ${\\mathbf \\sim 0.01 M_\\odot}$ of unburnt carbon in the inner part of the core. When the carbon-oxygen core grows to Chandrasekhar mass, the amount of left-over carbon is sufficient to ignite thermonuclear runaway. At the moment of explosion, the star will possess an envelope of several $0.1 M_{\\odot}$, consisting of He, C, and possibly some H, perhaps producing a kind of peculiar SN. Based on the results of Waldman and Barkat (2007) for accreting white dwarfs, we expect to get thermonuclear runaway at a broad range of $\\rho_c \\approx (1 - 6) \\times 10^9 \\mathrm{g cm^{-3}}$, depending on the amount of residual carbon. We verified the feasibility of this scenario by showing that in a close binary system with initial masses $(8.5 + 7.7) M_{\\odot}$ and initial period of 150 day the primary produces a helium remnant of $2.3 M_{\\odot}$ that evolves further like the...

Waldman, Roni; Barkat, Zalman

2007-01-01

70

Direct determination of the helium 3 content of atmospheric air by mass spectrometry  

International Nuclear Information System (INIS)

The Bureau of Mines, Helium Field Operations, in Amarillo, Texas, has developed a method for direct measurement of the helium 3 content of air by mass spectrometry. The helium is preconcentrated by passing samples of air through a charcoal trap at liquid nitrogen temperature. Sample measurements are compared with identically made measurements of gravimetrically prepared standards. The helium 3 content of near-surface atmospheric air is determined to be 7.27 ± 0.20 parts per trillion by volume (pptv). The accuracy of 0.20 pptv is at the 68% confidence level. The helium 4 content of near-surface atmospheric air has recently been determined at this facility to be 5.2204 ± 0.0041 parts per million by volume (ppmv). The helium 3/helium 4 ratio for atmospheric helium, RA, is established as 1.393 x 10-6 by independent measurements of the separate components

1990-03-20

71

Helium White Dwarfs in Cataclysmic Variables  

CERN Multimedia

Binary evolution predicts a population of helium core (M 1000 yr) stable burning phase occurs after the CN outburst, potentially explaining enigmatic short orbital period supersoft sources like RX J0537-7034 (P_orb = 3.5 hr) and 1E 0035.4-7230 (P_orb = 4.1 hr).

Shen, Ken J; Bildsten, Lars

2009-01-01

72

Detrapping of implanted helium and nitrogen in Mo  

Energy Technology Data Exchange (ETDEWEB)

Detrapping of implanted 60 keV helium and 40 keV nitrogen in polycrystalline molybdenum has been investigated using the (p, ..gamma..) resonance broadening method to probe the depth profiles of self-trapped nitrogen and of nitrogen helium-vacancy complexes. The helium and nitrogen doses were 0.7 x 10/sup 15/ and 1 x 10/sup 16/ ions/cm/sup 2/, respectively. Based on isochronal annealing measurements for 1-2 h the detrapping of helium and nitrogen from vacancies and nitrogen from helium-vacancy complexes was observed to center at 950, 550 and 800/sup 0/C, respectively, and to be total. The values 3.6 +- 0.4, 2.8 +- 0.2 and 2.5 +- 0.2 eV, respectively, were obtained for activation energies of the dissociations.

Hautala, M.; Anttila, A.; Hirvonen, J. (Helsinki Univ. (Finland). Dept. of Physics)

1982-02-01

73

Helium bubbles in molybdenum investigated by positron annihilation spectroscopy  

International Nuclear Information System (INIS)

Positron lifetime and Doppler broadening measurements have been performed in homogeneously helium implanted (715 appm) molybdenum. A new stage beyond the temperature range of stability of voids has been observed. The shorter lifetime component ?1 = 158±2 ps of 60% intensity is assigned to the positron state in helium-decorated dislocation loops while the longer lifetime component ?2=408±5 ps of 40% intensity is explained in terms of positron trapping at voids with a small percentage of helium associated with them. Dissociation of helium from loops is observed in the range 300-800 K followed by loop annealing above 900 K. A sharp reduction of ?2 around 1300 K is assigned to multiple helium occupancy of voids, resulting in their transformation into stable bubbles. Helium retention in bubbles is found stable up to the highest annealing temperature of 1700 K. The bubble parameters deduced from the positron lifetime results reveal that the pressure in the bubbles is maintained at the near-equilibrium value and that the vacancy mode of bubble growth is operative, in contrast to the reported growth of athermal bubbles in molybdenum following very low energy helium implantation where loop punching mechanism seems to control the excess pressure in bubbles. A brief comparison is also made between the observed behaviour of helium with that of hydrogen in molybdenum and the differences are discussed. (author).

74

Helium accumulation in groundwater. Pt. 3  

International Nuclear Information System (INIS)

[en] The groundwaters of the Great Artesian Basin (Australia) have been previously shown to be accumulating in-situ production helium for groundwaters ages 100 kyr. New helium isotope measurements show that the observed in-situ production helium (3He/4He ? 1.6x10-8) is isotopically distinct from the crustal degassing helium flux (3He/4He ? 6.6x10-8). Furthermore, the crustal degassing helium isotope ratio is marginally in excess of the whole crustal production ratio (3He/4He = 3.5x10-8) and the production ratio in a variety of continental rock types. This suggests that the upper limit on volatile transport across the mantle-crust boundary beneath the (relatively) stable and 'complacent' Australian continent can be characterized by a 'conductive-diffusive' helium/heat flux ratio of 6 4He atoms mW-1s-1 which is two orders of magnitude less than the 'intrusive-volcanic' ratio of 2.9x108 4He atoms mW-1s-1 measured at the Galapagos. These results constrain the transcrustal mantle degassing fluxes of 4He and 40Ar to be much less than the mid-ocean ridge degassing fluxes; which are much less than the degassing of 4He and 40Ar from continental crust. Thus, the degassing of the Earth's interior is dominated by magmatic processes but the dominant fluxes of 4He and 40Ar to the atosphere must come from the continental crust. (orig.)

1987-01-01

75

Welding of niobium alloys in helium with different oxygen content  

International Nuclear Information System (INIS)

Experimentally determined has been the dependence of the oxygen transition from the helium atmosphere into the joint metal during the welding of the niobium and its alloys (Nb-W-Mo-Zr and Nb-Zr-C system). Researched has been the distribution of oxygen on the welded joint surface during the alternation of its content in the helium atmosphere from 8x10-5% up to 5x10-1vol%. The rise of the oxygen content in helium over 1x10-2 vol% causes a sharp reduction of the joint impact strength

1978-01-01

76

Helium-3 from the moon  

International Nuclear Information System (INIS)

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

1992-01-01

77

Photodissociation of alkyl iodides in helium nanodroplets. II. Solvation dynamics.  

Science.gov (United States)

The solvation dynamics of nonthermal species in liquid helium has been investigated by photolyzing alkyl iodide molecules, CH3I, C2H5I, and CF3I, embedded in helium nanodroplets. Iodine and CH3 fragments are found to leave the droplets solvated by a finite number of helium atoms, this in contrast to C2H5 and CF3 fragments. The speed distributions of the IHeN and CH3HeN complexes show a prominent correlation with the degree of solvation N. It is argued that this correlation is caused by a dynamical adjustment of the solvation structure size to the relative speed of the traveling fragments as they pass through the helium bath. The absence of C2H5HeN and CF3HeN complexes is attributed to the large internal energy of these alkyl fragments which leads to a rapid destruction of any possibly formed complexes. PMID:17887834

Braun, Andreas; Drabbels, Marcel

2007-09-21

78

Development of 18 K helium refrigeration system for CERN  

CERN Multimedia

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).

CERN. Geneva

2004-01-01

79

Scintillation of Liquid Helium for Low-Energy Nuclear Recoils  

CERN Document Server

The scintillation properties of liquid helium upon the recoil of a low energy helium atom are discussed in the context of the possible use of this medium as a detector of dark matter. It is found that the prompt scintillation yield in the range of recoil energies from a few keV to 100 keV is somewhat higher than that obtained by a linear extrapolation from the measured yield for an 5 MeV alpha particle. A comparison is made of both the scintillation yield and the charge separation by an electric field for nuclear recoils and for electrons stopped in helium.

Ito, T M

2013-01-01

80

Orbital electron capture of hydrogen- and helium-like ions  

Science.gov (United States)

Corrections to the ratio of electron capture (EC) rates in hydrogen- and helium-like ions are calculated. We find that the most significant contribution is the electron screening effect. The correction has a simple form (1-5/16Z)3(1-?3) which ranges from almost 50% in helium to 1% in heavier nuclei. We discuss also EC in helium-like ions accompanied by an emission of the remaining electron into the continuum, a new decay channel, for which we calculate the decay probability. It is a very exotic type of Auger electron emission.

Siegie?-Iwaniuk, Katarzyna; Winckler, Nicolas; Bosch, Fritz; Geissel, Hans; Litvinov, Yuri A.; Patyk, Zygmunt

2011-07-01

 
 
 
 
81

Liquid-helium scintillation detection with germanium photodiodes  

Energy Technology Data Exchange (ETDEWEB)

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

Luke, P.N.; Haller, E.E.; Steiner, H.M.

1982-05-01

82

Simulation of liquid helium  

International Nuclear Information System (INIS)

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

1985-08-03

83

Simulation of liquid helium  

Energy Technology Data Exchange (ETDEWEB)

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

Ceperley, D.M.

1985-07-01

84

Performance of an efficient Helium Circulation System on a MEG  

International Nuclear Information System (INIS)

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

2009-02-01

85

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

CERN Multimedia

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

Davide Vitè

2002-01-01

86

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

CERN Document Server

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

Davide Vitè

2002-01-01

87

Helium exhaust studies in the DIII-D tokamak  

International Nuclear Information System (INIS)

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

1994-01-01

88

Quantum cavitation in liquid helium  

CERN Document Server

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

Guilleumas, M; Jezek, D M; Lombard, R J; Pi, M

1996-01-01

89

Quantum cavitation in liquid helium  

Energy Technology Data Exchange (ETDEWEB)

Using a functional-integral approach, we have determined the temperature below which cavitation in liquid helium is driven by thermally assisted quantum tunneling. For both helium isotopes, we have obtained the crossover temperature in the whole range of allowed negative pressures. Our results are compatible with recent experimental results on {sup 4}He. {copyright} {ital 1996 The American Physical Society.}

Guilleumas, M. [Dipartimento di Fisica, Universita di Trento, 38050 Povo (Italy); Barranco, M. [Departament d`Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, E-08028 Barcelona (Spain); Jezek, D.M. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, RA-1428 Buenos Aires (Argentina); Lombard, R.J. [Institut de Physique Nucleaire, Division de Physique Theorique. 91406 Orsay (France); Pi, M. [Departament d`Estructura i Constituents de la Materia, Facultat de Fisica, Universitat de Barcelona, E-08028 Barcelona (Spain)

1996-12-01

90

Helium dilution refrigeration system  

Energy Technology Data Exchange (ETDEWEB)

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

Roach, Patrick R. (Darien, IL); Gray, Kenneth E. (Naperville, IL)

1988-01-01

91

Evaluation of helium cooling for fusion divertors  

International Nuclear Information System (INIS)

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

1993-01-01

92

Evaluation of helium cooling for fusion divertors  

Energy Technology Data Exchange (ETDEWEB)

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.

Baxi, C.B.

1993-09-01

93

Helium in near Earth orbit  

CERN Multimedia

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).

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

94

Ultrasensitive leak testing: helium accumulation  

International Nuclear Information System (INIS)

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

1976-09-27

95

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

International Nuclear Information System (INIS)

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

1994-01-01

96

Arc welding of vanadium alloys in helium with oxygen additions  

International Nuclear Information System (INIS)

The reqularities are studied in vanadium oxidation in the course of arc welding in a chamber with different partial oxygen pressure in a protective helium atmosphere, and also the effect of oxygen on the mechanical properties of the weld metal. The results of bending and impact tests show that the oxygen content up to 5 x 10-3% in helium during welding in a controlled atmosphere does not affect the plasticity and viscosity of the joint

1977-01-01

97

Central helium density measurements in PLT  

International Nuclear Information System (INIS)

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

1981-01-01

98

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-10-15

99

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-10-01

100

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

International Nuclear Information System (INIS)

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

1995-01-01

 
 
 
 
101

Helium dimers and trimers within carbon nanotubes  

International Nuclear Information System (INIS)

[en] Helium dimers and trimers in infinite carbon nanotubes are described by wave function constructed as a product of Jastrow-Feenberg (JF) pair correlation and one-particle functions. One-particle functions are the ground state eigenfunctions of one helium atom in the tube; their analytic form is derived by fitting the corresponding numerical solution. Using this function in the Monte Carlo (MC) calculations in two successive stages, VMC (simple variational MC) and DMC (diffusion MC), it is found that binding strongly depends on the tube radius. Among armchair nanotubes binding is the strongest for the (7,7) nanotube. In that case the average distance between helium atoms in dimers and trimers is between 5 and 10 Angst. For larger radii the energies of 3He dimers and trimers are the same within the errorbars, indicating the possible dimerized structure. In the (5,5) nanotube, the binding energies of boson 4He3 and fictitious fermion trimer, which has the same mass as 4He3 and spin ((1)/(2)), are within the errorbars

2004-06-15

102

Helium dimers and trimers within carbon nanotubes  

Energy Technology Data Exchange (ETDEWEB)

Helium dimers and trimers in infinite carbon nanotubes are described by wave function constructed as a product of Jastrow-Feenberg (JF) pair correlation and one-particle functions. One-particle functions are the ground state eigenfunctions of one helium atom in the tube; their analytic form is derived by fitting the corresponding numerical solution. Using this function in the Monte Carlo (MC) calculations in two successive stages, VMC (simple variational MC) and DMC (diffusion MC), it is found that binding strongly depends on the tube radius. Among armchair nanotubes binding is the strongest for the (7,7) nanotube. In that case the average distance between helium atoms in dimers and trimers is between 5 and 10 Angst. For larger radii the energies of {sup 3}He dimers and trimers are the same within the errorbars, indicating the possible dimerized structure. In the (5,5) nanotube, the binding energies of boson {sup 4}He{sub 3} and fictitious fermion trimer, which has the same mass as {sup 4}He{sub 3} and spin ((1)/(2)), are within the errorbars.

Vranjes, Leandra; Antunovic, Zeljko; Kilic, Srecko

2004-06-15

103

Photoionization of helium dimers  

International Nuclear Information System (INIS)

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

2010-01-01

104

Helium, hydrogen, and oxygen velocities observed on isee-3  

Energy Technology Data Exchange (ETDEWEB)

The velocities of hydrogen, helium, and oxygen ions over a full range of solar wind conditions were recorded by the ion composition instrument and Los Alamos National Laboratory plasma instrument aboard the International Sun Earth Explorer. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s(-1) the helium velocity exceeded the hydrogen velocity by 5 km s(-1) the average difference was 14 km s(-1), however no evidence was found for a nonzero average velocity difference between helium and oxygen ions even at the higher velocities. Velocity differences were examined in a number of streams and across a number of interplanetary shocks. Generally helium hydrogen velocity differences are bounded by the Alfven speed. Velocity differences show abrupt changes across interplanetary discontinuities, presumably tangential. The electrostatic potential change across a shock produces differences between the velocities of ions having different charges.

Ogilvie, K.W. (Maryland Univ., College Park); Coplan, M.A. (LASL)

1982-03-01

105

Phase separation in hydrogen-helium mixtures at Mbar pressures.  

UK PubMed Central (United Kingdom)

The properties of hydrogen-helium mixtures at Mbar pressures and intermediate temperatures (4000 to 10000 K) are calculated with first-principles molecular dynamics simulations. We determine the equation of state as a function of density, temperature, and composition and, using thermodynamic integration, we estimate the Gibbs free energy of mixing, thereby determining the temperature, at a given pressure, when helium becomes insoluble in dense metallic hydrogen. These results are directly relevant to models of the interior structure and evolution of Jovian planets. We find that the temperatures for the demixing of helium and hydrogen are sufficiently high to cross the planetary adiabat of Saturn at pressures approximately 5 Mbar; helium is partially miscible throughout a significant portion of the interior of Saturn, and to a lesser extent in Jupiter.

Morales MA; Schwegler E; Ceperley D; Pierleoni C; Hamel S; Caspersen K

2009-02-01

106

Electronic properties of physisorbed helium  

Energy Technology Data Exchange (ETDEWEB)

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.

Kossler, Sarah

2011-09-22

107

Electronic properties of physisorbed helium  

International Nuclear Information System (INIS)

[en] 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.

2011-01-01

108

Energy of helium dissolved in metals  

International Nuclear Information System (INIS)

An explanation for the large negative heat of solution of helium in metals, in terms of the strong repulsive helium pseudopotential interacting with the metal conduction electrons is proposed. Calculations for helium in aluminium and magnesium show that this mechanism indeed generates the expected negative heats. It is expected that the helium atoms will always seek out the site of lowest charge density. (author)

1976-01-01

109

Cycle design for the ISABELLE helium refrigerator  

International Nuclear Information System (INIS)

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

1981-08-14

110

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

1997-03-01

111

Operating Manual of Helium Refrigerator (Rev. 2)  

Energy Technology Data Exchange (ETDEWEB)

A helium refrigerator was installed as a supplier of 20K cold helium to the cryogenic distillation system of WTRF pilot plant. The operating procedures of the helium refrigerator, helium compressor and auxiliary apparatus are described for the safety and efficient operation in this manual. The function of the helium refrigerator is to remove the impurities from the compressed helium of about 250psig, to cool down the helium from ambient temperature to 20K through the heat exchanger and expansion engine and to transfer the cold helium to the cryogenic distillation system. For the smoothly operation of helium refrigerator, the preparation, the start-up, the cool-down and the shut-down of the helium refrigerator are described in this operating manual. (author). 3 refs., 14 tabs.

Song, K.M.; Son, S.H.; Kim, K.S.; Lee, S.K.; Kim, M.S. [Korea Electric Power Research Institute, Taejon (Korea)

2002-07-01

112

ITER helium ash accumulation  

International Nuclear Information System (INIS)

Many studies have shown the importance of the ratio ?He/?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 ?He/?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 ?8%. We find 1He/?E

1990-01-01

113

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

International Nuclear Information System (INIS)

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

1995-01-01

114

High temperature creep of a helium-implanted titanium aluminide alloy  

International Nuclear Information System (INIS)

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

2011-09-01

115

High temperature creep of a helium-implanted titanium aluminide alloy  

Energy Technology Data Exchange (ETDEWEB)

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

Magnusson, Per, E-mail: per.magnusson@psi.ch [Paul Scherrer Institut, Nuclear Energy and Safety, 5232 Villigen PSI (Switzerland); Chen Jiachao; Hoffelner, Wolfgang [Paul Scherrer Institut, Nuclear Energy and Safety, 5232 Villigen PSI (Switzerland)

2011-09-01

116

Performance of the Helium Circulation System on a Commercialized MEG  

Science.gov (United States)

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.

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

2012-12-01

117

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

Energy Technology Data Exchange (ETDEWEB)

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

Fukumoto, K.; Matsui, H. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Chung, H.M.; Gazda, J.; Smith, D.L. [Argonne National Lab., IL (United States)

1996-12-31

118

Features of wide-aperture glow discharge in helium  

International Nuclear Information System (INIS)

[en] The characteristics of wide-aperture discharge in helium have been studied for a cathode diameter of 19.5 cm and a cathode - grid anode distance of 3 cm. It is established that the properties of discharge in this system are substantially different from those of an abnormal discharge. The difference is manifested in the bending of current-voltage characteristics, their pronounced dependence on the helium pressure, a nonmonotonic dependence of the electron beam generation efficiency ? on the discharge voltage U, and an anomalously high efficiency (? ? 100%) in the range of U ? 350...1000 V[ru] ??????????? ?????????????? ????????????????? ??????? ? ????? ? ????????? ?????? 19.5 ?? ? ??????????? ????? - ???????? ???? 3 ??. ??????????, ??? ???????? ??????? ?????? ?????????? ?? ??????? ??????????? ???????. ??? ??????? ?????????? ? ??????? ????????? ? ???, ?? ?????? ??????????? ?? ???????? ?????, ?????????????? ??????????? ????????????? ????????? ???????????? ????? ? ?? ?????????? ??????? U, ? ????? ? ?????????? ????????????? ????????? ? ? 100% ? ????????? U ? 350...1000 ?

2007-10-12

119

Superfluid phases of helium-3  

International Nuclear Information System (INIS)

A comprehensive treatment of the theory of superfluid helium-3 is presented in this book. This treatment also illustrates many of the principal themes of theoretical condensed matter physics over the past two decades. The generalized BCS (Barden-Cooper-Schrieffer) pairing theory and the experimental properties of superfluid helium-3 are treated in detail. Extensive treatment of broken symmetries and their relation to macroscopic order and of the closely related topics of superflow and texture, defects in the order parameter field, and the dynamics of the nuclear spins as probed by nuclear magnetic resonance is included. This book should serve as a valuable reference for anyone working on superfluid helium-3 or on the closely related topics of unconventional superconductivity in heavy-electron metals and superfluidity of neutron star interiors

1991-01-01

120

Superfluid phases of helium-3  

Energy Technology Data Exchange (ETDEWEB)

A comprehensive treatment of the theory of superfluid helium-3 is presented in this book. This treatment also illustrates many of the principal themes of theoretical condensed matter physics over the past two decades. The generalized BCS (Barden-Cooper-Schrieffer) pairing theory and the experimental properties of superfluid helium-3 are treated in detail. Extensive treatment of broken symmetries and their relation to macroscopic order and of the closely related topics of superflow and texture, defects in the order parameter field, and the dynamics of the nuclear spins as probed by nuclear magnetic resonance is included. This book should serve as a valuable reference for anyone working on superfluid helium-3 or on the closely related topics of unconventional superconductivity in heavy-electron metals and superfluidity of neutron star interiors.

Vollhardt, D.; Wolfle, P.

1991-01-01

 
 
 
 
121

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

Energy Technology Data Exchange (ETDEWEB)

We demonstrate the conduction of free electrons along an array of microchannels of liquid helium, 30 {mu}m wide, 1 {mu}m deep and 1.5 mm long, held by surface tension between conducting ribs. No perpendicular conduction occurs until the bulk helium level rises above the channels. (orig.) 8 refs.

Haren, R.J.F. van; Fozooni, P.; Kristensen, A.; Lea, M.J.; Richardson, P.J. [London Univ. (United Kingdom). Dept. of Physics; Acres, G. [Department of Computer Science and Electronics, University of, Southampton, SO17 1BJ (United Kingdom); Valkering, A.M.C.; Heijden, R.W. van der [Department of Physics, Eindhoven University of Technology, P.O.Box 513, 5600 MB, Eindhoven (Netherlands)

1998-06-01

122

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

International Nuclear Information System (INIS)

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

1998-01-01

123

Calculations of line absorption for the Voigt profile and some specific lines of helium  

Energy Technology Data Exchange (ETDEWEB)

Calculations of the line absorption for the 396.5- , 361.4- , 318.7- , 492.2- , 587.6- , and 447.1-nm lines of helium have been performed for the Voigt profile. These results can be used to measure the absolute concentration of helium metastable atoms and several other excited atoms by the reabsorption method.

Kato, I.; Yonehara, A.

1980-07-01

124

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

Science.gov (United States)

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

Moore, Kevin; Townsley, Dean M.; Bildsten, Lars

2013-10-01

125

Direct current insulation breakdown characteristics of supercritical helium  

Energy Technology Data Exchange (ETDEWEB)

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

Ito, Daisuke; Nakayama, Shigeo (Toshiba Corp., Kawasaki, Kanagawa (Japan). Research and Development Center)

1983-10-01

126

Direct current insulation breakdown characteristics of supercritical helium  

International Nuclear Information System (INIS)

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

1983-01-01

127

Magnetically insulated helium ion diode  

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-01-01

128

Energy Levels of Helium Nucleus  

Directory of Open Access Journals (Sweden)

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

Cvavb Chandra Raju

2013-01-01

129

Helium reionization and the thermal proximity effect  

CERN Multimedia

We examine the temperature structure of the intergalactic medium IGM) surounding a hard radiation source, such as a Quasi-Stellar Object (QSO), as it responds to the onset of helium reionization by the source. We model the reionization using a radiative transfer (RT) code coupled to a particle-mesh (PM) N-body code. Neutral hydrogen and helium are initially ionized by a starburst spectrum, which is allowed to gradually evolve into a power law spectrum (fnu ~ nu^(-0.5)). Multiple simulations were performed with different times for the onset and dominance of the hard spectrum, with onset redshifts ranging from z = 3.5 to 5.5. The source is placed in a high-density region to mimic the expected local environment of a QSO. Simulations with the source placed in a low-density environment were also performed as control cases to explore the role of the environment on the properties of the surrounding IGM. We find in both cases that the IGM temperature within the HeIII region produced exceeds the IGM temperature before...

Meiksin, Avery; Brown, Calum K; 10.1111/j.1365-2966.2009.15667.x

2010-01-01

130

Is the Sun helium-deficient  

International Nuclear Information System (INIS)

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

1980-12-11

131

Central helium density measurements in PLT  

Energy Technology Data Exchange (ETDEWEB)

The central helium density in PLT has been deduced from measurements of the ratio of d-/sup 3/He to d-d fusion reactions during deuterium neutral beam injection. The inward transport time for /sup 3/He puffed at the edge plasma was 10 ..-->.. 30 msec. The decay time of the central /sup 3/He density increased with electron density, varying from 0.3 sec to greater than 1.0 sec over the density range of (1 ..-->.. 5) x 10/sup 13/ cm/sup -3/.

Chrien, R.E.; Eubank, H.P.; Meade, D.M.; Strachan, J.D.

1981-07-01

132

Linde standard helium plant of medium capacity  

International Nuclear Information System (INIS)

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

1991-01-01

133

Calcium fluoride crystal coloring initiated by helium  

International Nuclear Information System (INIS)

The work is devoted to ascertaining the mechanism of alkaline-earth fluoride thermostimulated luminescence (TSL) amplification and the role of helium in improving radiation defect formation efficiency. CaF2 monocrystals saturated with helium are used for measurements. It is shown that the crystal radiation colouring efficiency increases under CaF2 monocrystal saturation with helium for which a new optical center (?=535 mm) linked with helium is responsible

1988-05-12

134

Fermilab Central Helium Liquefier system upgrade  

International Nuclear Information System (INIS)

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

1994-01-01

135

Fermilab Central Helium Liquefier system upgrade  

Energy Technology Data Exchange (ETDEWEB)

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

Makara, J.; Barnes, T.; Bossert, R.; Geynisman, M.; Hodge, G.; Kolar, R.; Walker, R. [Fermi National Accelerator Lab., Batavia, IL (United States)

1994-12-31

136

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

International Nuclear Information System (INIS)

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

1985-01-01

137

Helium distribution functions in tokamak plasmas  

International Nuclear Information System (INIS)

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

1995-01-01

138

Diffraction of an atomic helium beam  

International Nuclear Information System (INIS)

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

1988-01-01

139

Helium distribution functions in tokamak plasmas  

Energy Technology Data Exchange (ETDEWEB)

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

Maas, A.C.

1995-04-12

140

Helium line detections from ELDWIM at 1.4 GHz  

CERN Document Server

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

Baddi, Raju

2012-01-01

 
 
 
 
141

Helium partial pressure measurement in a deuterium environment  

International Nuclear Information System (INIS)

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

1996-01-01

142

Modification of the grain boundary microstructure of the austenitic PCA stainless steel to improve helium embrittlement resistance. [14Cr-16Ni-2. 5Mo-. 25Ti-. 4Si-. 05C  

Energy Technology Data Exchange (ETDEWEB)

Grain boundary MC precipitation was produced by a modified thermal-mechanical pretreatment in 25% cold worked (CW) austenitic prime candidate alloy (PCA) stainless steel prior to HFIR irradiation. Postirradiation tensile results and fracture analysis showed that the modified material (B3) resisted helium embrittlement better than either solution annealed (SA) or 25% CW PCA irradiated at 500 to 600/sup 0/C to approx.21 dpa and 1370 at. ppM He. PCA SA and 25% CW were not embrittled at 300 to 400/sup 0/C. Grain boundary MC survives in PCA-B3 during HFIR irradiation at 500/sup 0/C but dissolves at 600/sup 0/C; it does not form in either SA or 25% CW PCA during similar irradiation. The grain boundary MC appears to play an important role in the helium embrittlement resistance of PCA-B3.

Maziasz, P.J.; Braski, D.N.

1986-01-01

143

Shock waves in superfluid helium  

Energy Technology Data Exchange (ETDEWEB)

Exact solutions of the equations of motion of liquid helium II can be compared to experiments to test Landau's two-fluid theory. The best flows with which to conduct such tests are those in which amplitudes and gradients are large and in which the calculations and measurements are free from wall effects, e.g., shock waves. The four fundamental conservation equations of superfluid mechanics have been integrated across a one-dimensional discontinuity (shock wave) propagating into undisturbed helium II to yield a set of four algebraic equations (jump conditions) which, when supplemented by thermodynamic state information, establish the equilibrium flow state behind the shock wave for a given wave speed and undisturbed flow state ahead of the shock. These jump conditions have been solved numerically for 19 points on the helium II p-T diagram with upstream Mach number as the independent parameter. Representative results of the calculations are presented for pressure shocks, temperature raising shocks, and temperature lowering shocks. The results are compared to previous analytical approximate solutions to test the validity of those approximations. They are also compared to experimental data for shock waves in helium II as a means of testing the correctness of the full nonlinear two-fluid equations.

Moody, D.M.; Sturtevant, B.

1984-05-01

144

Structure of atomic helium trimers  

International Nuclear Information System (INIS)

[en] The structure of the bound states of the atomic helium trimers is calculated by use of hyperspherical coordinates and an adiabatic expansion of the Faddeev equations. The ground state of 4He3 has a triangular shape, the excited state is an Efimov state and the 3He4He2 bound state is a halo state. Refs. 6, figs. 3 (author)

1999-01-01

145

Recombining helium--neon plasma  

Energy Technology Data Exchange (ETDEWEB)

Recombining helium-neon plasmas are studied theoretically for free electron densities N/sub e/ = 10/sup 13/--10/sup 17/ cm/sup -3/, electron temperatures T/sub e/ = 0.05--0.50 eV, and heavy particle densities N<10/sup 18/ cm/sup -3/. The populations of the helium and neon levels are calculated in the steady sink approximation. It is shown that pure neon plasmas are not well suited as laser media. However, a large stable Ne(4s)-Ne(3p) population inversion can be achieved in a recombining neon--helium plasma. Optimum concentration ratios in the ranges N/sub Ne//N/sub He/< or =10/sup -3/ and N/sub Ne//N/sub e/ = 10/sup 1/--10/sup 3/ are determined, and simple formulas are derived for the Ne(4s) level populations. Inversion is shown to occur both in a recombining He--Ne plasma and when a recombining pure helium plasma is mixed with neon atoms in the ground state.

Belyaev, A.K.

1985-03-01

146

Helium approach to leak detection  

Energy Technology Data Exchange (ETDEWEB)

Locating a tiny leak in a 70,000-tube condenser can be like looking for a needle in a haystack. A faster, more-sensitive method that uses helium as a tracer gas is now in service at over 100 utilities. 1 figure.

McKee, C.; Kolar, M.; Mundis, J.; Coit, R.

1983-09-01

147

Kaonic Helium X-rays  

Science.gov (United States)

The long-standing "Kaonic-helium puzzle", i.e., the discrepancy between the measured and calculated 2p-level strong-interaction shift of kaonic helium 4, has been solved by the KEK E570 experiment; the measured 2p-level shift was 2 ± 2(stat) ± 2(syst) eV, thus agreeing with a majority of the theoretical calculations in contradiction to the previous average of 3 experiments of -43 ± 8eV. The smallness of the kaonic helium-4 2p-level shift has recently been confirmed by the SIDDHARTA collaboration at DA?NE. Both of these experiments used silicon drift X-ray detectors (SDDs), and have used elaborate in-situ calibration methods. In order to further study the low-energy kaon-nucleus interaction, the J-PARC E17 experiment will soon measure the kaonic helium-3 2p-level shift to high precision. I also briefly discuss the status of kaonic hydrogen x-ray spectroscopy.

Hayano, Ryugo S.

2011-09-01

148

Simplicity works for superfluid helium  

Energy Technology Data Exchange (ETDEWEB)

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)

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

2000-02-01

149

Mott and helium polarimetry of a spin polarized electron source  

International Nuclear Information System (INIS)

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

1992-01-01

150

Mott and helium polarimetry of a spin polarized electron source  

Energy Technology Data Exchange (ETDEWEB)

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

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

1992-09-01

151

Controlled Chemistry Helium High Temperature Materials Test Loop  

Energy Technology Data Exchange (ETDEWEB)

A system to test aging and environmental effects in flowing helium with impurity content representative of the Next Generation Nuclear Plant (NGNP) has been designed and assembled. The system will be used to expose microstructure analysis coupons and mechanical test specimens for up to 5,000 hours in helium containing potentially oxidizing or carburizing impurities controlled to parts per million levels. Impurity levels in the flowing helium are controlled through a feedback mechanism based on gas chromatography measurements of the gas chemistry at the inlet and exit from a high temperature retort containing the test materials. Initial testing will focus on determining the nature and extent of combined aging and environmental effects on microstructure and elevated temperature mechanical properties of alloys proposed for structural applications in the NGNP, including Inconel 617 and Haynes 230.

Richard N. WRight

2005-08-01

152

Helium Refrigeration System for BNL Colliding-Beam Accelerator  

Energy Technology Data Exchange (ETDEWEB)

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

Brown, D.P.; Farah, Y.; Gibbs, R.J.; Schlafke, A.P.; Schneider, W.J.; Sondericker, J.H.; Wu, K.C.

1983-01-01

153

Study of the Helium Enrichment in Globular Clusters  

CERN Document Server

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

Valcarce, A A R

2009-01-01

154

Effect of helium on tensile properties of vanadium alloys  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1997-08-01

155

Helium Refrigeration System for BNL Colliding-Beam Accelerator  

International Nuclear Information System (INIS)

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

1983-01-01

156

Welding of niobium alloys in helium with nitrogen additions  

International Nuclear Information System (INIS)

Experimentally determined is the dependence of nitrogen penetration into a weld metal from the controlled helium atmosphere when welding non-alloyed niobium and alloys of the following systems: Nb-W-Mo-Zr and Nb-Zr-C. The influence of nitrogen on the fracture mechanism of cast structure of the weld metal has been investigated. Nitrogen content in helium which does not change the impact strength of weld metal, ranges for various alloys from 1.5x10sup(-2) to 1x10sup(-20) vol.%

1978-01-01

157

Helium embrittlement of a lamellar titanium aluminide  

Science.gov (United States)

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

Magnusson, P.; Chen, J.; Jung, P.; Sauvage, T.; Hoffelner, W.; Spätig, Ph.

2013-03-01

158

The antimicrobial effects of helium and helium-air plasma on Staphylococcus aureus and Clostridium difficile.  

UK PubMed Central (United Kingdom)

UNLABELLED: Healthcare-associated infections (HCAI) affect 5-10% of acute hospital admissions. Environmental decontamination is an important component of all strategies to prevent HCAI as many bacterial causes survive and persist in the environment, which serve as ongoing reservoirs of infection. Current approaches such as cleaning with detergents and the use of chemical disinfectant are suboptimal. We assessed the efficacy of helium and helium-air plasma in killing Staphylococcus aureus and Clostridium difficile on a glass surface and studied the impact on bacterial cells using atomic force microscopy (AFM). Both plasma types exhibited bactericidal effects on Staph. aureus (log3·6 - >log7), with increased activity against methicillin-resistant strains, but had a negligible effect on Cl. difficile spores (<1log). AFM demonstrated cell surface disruption. The addition of air increased the microbicidal activity of the plasma and decreased the exposure time required for an equivalent log reduction. Further evaluation of cold plasma systems is warranted with, for example, different bacteria and on surfaces more reminiscent of the health care environment as this approach has potential as an effective decontaminant. SIGNIFICANCE AND IMPACT OF THE STUDY: Many bacterial causes of healthcare infection can survive in the inanimate environment for lengthy periods and be transmitted to patients. Furthermore, current methods of environmental decontamination such as detergents, chemical disinfectants or gaseous fumigation are suboptimal for a variety of reasons. We assessed the efficacy of helium and helium-air plasma as a decontaminant and demonstrated a significant reduction in bacterial counts of Staphylococcus aureus on a glass surface. Atomic force microscopy morphologically confirmed the impact on bacterial cells. This approach warrants further study as an alternative to current options for hospital hygiene.

Galvin S; Cahill O; O'Connor N; Cafolla AA; Daniels S; Humphreys H

2013-08-01

159

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

Directory of Open Access Journals (Sweden)

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

D. Rucinski; M. Bzowski; H. J. Fahr

0000-01-01

160

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

Science.gov (United States)

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.

Rucinski, D.; Bzowski, M.; Fahr, H. J.

2003-06-01

 
 
 
 
161

HeREF-2003 : Helium Refrigeration Techniques  

CERN Multimedia

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 ...

2003-01-01

162

HeREF-2003: Helium Refrigeration Techniques  

CERN Document Server

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...

2003-01-01

163

Internally-cooled cabled superconductors cooled with helium II  

International Nuclear Information System (INIS)

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

1981-01-01

164

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

International Nuclear Information System (INIS)

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

1966-01-01

165

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

Energy Technology Data Exchange (ETDEWEB)

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

Akiyama, Y. (Electrotechnical Lab., Sakura, Ibaraki (Japan))

1980-10-01

166

Vanadium alloys with improved resistance to helium embrittlement  

Energy Technology Data Exchange (ETDEWEB)

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

Braski, D.N.

1990-01-01

167

Cycle design for the ISABELLE helium refrigerator  

Energy Technology Data Exchange (ETDEWEB)

The superconducting magnets for the ISABELLE storage ring/accelerator are designed to be operated at 3.8/sup 0/K using a forced-flow supercritical helium cooling system. The ISABELLE refrigerator has been designed subject to these special requirements. The design output is 13.65 KW of refrigeration below 4.2/sup 0/K (for cooling the magnet and distribution system), 55 KW at 55/sup 0/K (to cool heat shields for the whole system) and 100 g/s of liquefaction (for magnet power leads cooling). The system incorporates a subcooler section that produces liquid helium at 5.3 atm and 2.6 K and circulates it through the loads, and a Claude-type main refrigerator section. The main refrigerator section has five stages of cooling, with four of them below liquid nitrogen temperature. Liquid nitrogen precooling is not used. With 60% isothermal compressors the efficiency of the refrigerator system will be about 26% of Carnot.

Brown, D.P.; Schlafke, A.P.; Wu, K.C.; Moore, R.W.

1981-01-01

168

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

Energy Technology Data Exchange (ETDEWEB)

Groundwater contains various types of dissolved gases, which are considered to provide information about the geoenvironment. Especially, the dissolved noble gases have been used to survey groundwater movement as natural tracers. In this study, we revealed the groundwater origins and the size and position of groundwater basins by investigating a trend of groundwater evolution deduced from the increase in dissolved helium content and change in helium isotopes ratio. The study area is a typical volcanic aquifer in Japan that was formed 10{sup 5} years ago by piling up four layers of pyroclastic flow that erupted from the active volcano, Mt Aso, located on the east fringe of the Kumamoto Plain. We measured the dissolved helium content and ratio of isotopes to evaluate the origin and the mixing process of groundwater, and to distinguish the groundwater basins. Shallow groundwater in the basin was recharged by rainwater and was characterised by accumulating helium components distinguished from differences in helium isotope ratio along the flow paths in the basins. The sources of excess helium accumulated in shallow groundwater were categorized into two groups having a high {sup 3}He/{sup 4}He ratio of 4.0 - 5.1x10{sup -6} found in waters collected at hot-spas inside the caldera of Mt Aso, and one having a low of 0.8 {approx} 1.9x10{sup -6} found in hot springs outside the caldera. Dissolved helium was categorized into three groups: a small amount of excess helium content with {sup 3}He/{sup 4}He ratio equivalent to the dissolved atmospheric helium, high excess helium content with {sup 3}He/{sup 4}He ratio up to 2x10{sup -6}, and small excess helium with high {sup 3}He/{sup 4}He ratio up to 4.4x10{sup -6}. Consequently, the groundwater basin was split into four small basins by the combining characteristics of content and isotopic ratio of dissolved helium with information on the geohydrological formation, and the mixing process of groundwater was deduced from the change in the {sup 3}He/{sup 4}He ratio of helium in groundwater samples, which was supplied from two helium sources with a greatly different {sup 3}He/{sup 4}He ratio. (authors) 3 refs., 1 tab., 4 figs.

Mahara, Y.; Igarashi, T. [Central Research Institute of Electric Power Industry, Chibe (Japan). Abiko Research Laboratory; Kudo, A. [Kyoto University, Kumatori (Japan). Environmental Radionuclide Science, Research Reactor Institute

1997-10-01

169

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

Energy Technology Data Exchange (ETDEWEB)

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

Villard, B

1999-07-15

170

Helium circulator design and testing  

Energy Technology Data Exchange (ETDEWEB)

The helium circulator is a key component of the 10 MW high temperature gas-cooled reactor (HTR-10), which assures the thermal energy transfer from the reactor core to the steam generator and operates at 3.0 MPa, 250 deg. C helium condition. At the rated condition, the mass flow rate is 4.32 kg s{sup -1} and the pressure rise can reach 51.7 kPa at the rotational speed of 5000 rpm. In fact, the pressure rise required for the HTR-10 is only 14.7 kPa with a rotational speed of 3052 rpm. Thus, the layout of the blower contains a considerable margin. This paper presents the design procedures of the circulator during its development. Test results both in the factory and in the HTR-10 are given. Furthermore, the circulator design features and aerodynamic performance are highlighted.

Zhou, H.Z.; Wang, J. E-mail: wangj@d103.inet.tsinghua.edu.cn

2002-10-01

171

The helium detector, ch. 8  

International Nuclear Information System (INIS)

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

1976-01-01

172

On positron annihilation in helium  

International Nuclear Information System (INIS)

Numerical calculations of the positron annihilation decay rate in helium gas have been made over a wide range of electric (0-50 Vcm-1) and magnetic (0-20 KG) fields at various temperatures. Two models of positron-atom interaction have been considered. The computations indicate that the positron life-time decreases with the magnetic field at given electric/temperature fields. When the electric field is zero, magnetic field has no effect on the life-time. (Auth.)

1982-04-07

173

Helium embrittlement in austenitic steel  

International Nuclear Information System (INIS)

For examination of the mechanism of helium high-temperature embrittlement occuring on structural materials, simulation experiments on He-loaded samples were carried through. For this, foils of the austenitic steel No. 1.4970, with a thickness of 105 ? and a grain size of 20 ? were used. Helium implantation was performed by means of ?-particles coming from a cyclotron. Tensile tests (at 7500 and 8000C), creep tests as a function of the applied stress (at 7000 and 8000C), and annealing treatments without stress (at 7000 up to 1,0000C) were made with He-implanted samples and with unimplanted reference samples in a high vacuum of 10-6 torr. The surfaces of fracture and the microstructure were studied using SEM and TEM, respectively. The comparison between the He-implanted and unimplanted samples shows that helium causes a strengthening of the matrix, a reduction of the ductility and a weakening of the grain boundaries. All these effects are obtained even at He-concentrations of 10-20 at ppm and do not change any more at higher He-contents (saturation behaviour). (IHOE)

1977-03-11

174

Hyperfine structure of helium three  

Energy Technology Data Exchange (ETDEWEB)

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

Druzbick, J.

1982-01-01

175

Hyperfine structure of helium three  

International Nuclear Information System (INIS)

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

1982-01-01

176

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

CERN Multimedia

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

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

2002-01-01

177

Helium diffusion in nickel at high temperatures  

International Nuclear Information System (INIS)

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

1980-01-01

178

Interaction of helium with a metal surface  

Energy Technology Data Exchange (ETDEWEB)

A theory is given for the interaction of a helium atom with a metal surface. The basic theory is a generalisation of that used by Zaremba and Kohn for jellium surfaces, and relates the interaction to shifts of the band energies due to the presence of the helium. It is shown that these shifts can be determined via perturbation theory in the non-local helium pseudopotential. The first-order expression is particularly simple and demonstrates the physical origin of the interaction in terms of a balance between the kinetic energy cost when the Bloch tails orthogonalise to the helium ls orbital and the potential energy gained in the field of the helium atom. For jellium, higher-order corrections are shown to contribute only approximately 15% to the interaction. The first-order result should therefore give a reasonably accurate picture of the corrugation profiles probed by low-energy helium particles.

Harris, J.; Liebsch, A. (Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Festkoerperforschung)

1982-04-10

179

Helium in metals: effect on mechanical properties  

International Nuclear Information System (INIS)

Helium is produced in solids under irradiation by reactions of the type (n,?), (p,?), etc. or by ?-implantation. Because of its vanishingly small solubility, helium precipitates into bubbles which in turn can cause drastic changes in the mechanical properties of solids, particularly at high temperatures. In this review, typical examples of high temperature embrittlement by helium under static (creep) and cyclic (fatigue) loads are presented with emphasis on austenitic and martensitic steels for fusion application. The experimental results (lifetime, ductility and helium bubble microstructure as functions of stress, temperature, helium content, etc.) are discussed in the light of theoretical models treating the sequence of processes which lead from the production of helium via the formation of bubbles and their stable and unstable growth to the final failure of the materials

1992-01-01

180

Helium isotopic abundance variation in nature  

Energy Technology Data Exchange (ETDEWEB)

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

Holden, N.E.

1993-08-01

 
 
 
 
181

Energy, helium, and the future: II  

Energy Technology Data Exchange (ETDEWEB)

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

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

1980-01-01

182

Helium transport studies on DIII-D  

Energy Technology Data Exchange (ETDEWEB)

The measurement of Helium density profiles in tokamak plasmas is necessary for helium transport studies. These studies are important in predicting the helium ash transport properties for ITER and win have important implications for the design. Poor helium transport in reactors could lead to a buildup of fusion ash, causing fuel dilution and increased radiation that will result in degraded fusion power and possibly quench ignition altogether. Present estimates indicate that He concentrations in the core must be kept below 10% in order to maintain continuous reactor operation. Helium transport studies have begun on the DM-D tokamak using charge exchange recombination (CER) spectroscopy for helium density measurements. Helium transport behavior has been observed by injecting helium gas puffs into DM-D plasmas and measuring the He density profile evolution. The profiles are used to calculate the relevant helium transport properties. This paper covers the results obtained from puffing He gas into L-mode plasmas of various electron densities. The results obtained in DIII-D L-mode plasmas are similar to measurements made at TEXTOR and JT-60.

Finkenthal, D.F. (California Univ., Berkeley, CA (United States)); Hillis, D.L.; Wade, M.R.; Hogan, J.T.; Klepper, C.C.; Mioduszewski, P.K. (Oak Ridge National Lab., TN (United States)); West, W.P.; Burrell, K.H.; Seraydarian, R.P.; Groebner, R.J.; Gohil, P. (General Atomics, San Diego, CA (United States))

1992-05-01

183

Helium-3 emission related to volcanic activity  

Energy Technology Data Exchange (ETDEWEB)

The helium-3/helium-4 ratio in bubbling gases from ten hot springs located around Mount Ontake, an active volcano in central Japan, ranges from 1.71 R/sub atm/ (1.71 times the atmospheric ratio of 1.40 x 10/sup -6/) to 6.15 R/sub atm/. The value of the ratio decreases with distance from the central cone of the volcano. Such a tendency may be a characteristic of helium-3 emission in volcanic areas and suggests more primitive helium-3 is carried with fluid flowing through a conduit during volcanic activity. 6 references, 1 figure, 1 table.

Sano, Y.; Nakamura, Y.; Wakita, H.; Urabe, A.; Tominaga, T.

1984-04-13

184

Exposure of Pershore CR39 and Kodak LR115 films to helium ions  

International Nuclear Information System (INIS)

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

1991-01-01

185

The Liquefaction of Hydrogen and Helium Using Small Coolers  

International Nuclear Information System (INIS)

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

2006-01-01

186

The Liquefaction of Hydrogen and Helium Using Small Coolers  

Energy Technology Data Exchange (ETDEWEB)

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

Green, Michael A.

2006-02-12

187

Controls on helium solubility in olivine at low pressures  

Science.gov (United States)

Experiments on the solubility of helium in olivine have been conducted over a range of conditions to evaluate the thermodynamic controls on helium partitioning during melting. The experiments were performed at 1 to 150 atm. total pressure at temperatures between 1350 and 1550° C. Helium partial pressures ranged from 0.5 to 150 atm. The effect of oxygen fugacity was examined by running experiments at both the QFM and Ni-NiO buffer, and by using both Fe-bearing and Fe-free olivines. Temperature: Experiments at 1350, 1450 and 1550° C (Ni-NiO buffer) show a clear decreasing solubility of helium with temperature, as expected for a gas dissolving in a solid. In contrast, previous experiments on basaltic melts show little change of helium solubility with temperature. Therefore the olivine-melt D value decreases steadily with temperature. Linear regression yields the equation DHe=-8.8e-6T+ 0.014 (with R2 > 0.999), where T is in degrees C. Using the van't Hoff equation, this implies an enthalpy of solution of -2.0 kJ/mole and an entropy of solution of -1.97 J/mole K. Pressure: Experiments on powdered samples at helium partial pressures of 0.5 and 150 atmospheres suggest a Henry's law constant between 1e-6 and 3e-6 STP cc/g/atm. This value is around 2 orders of magnitude lower than the Henry's law constant for basaltic melts, consistent with the higher density of olivine. Note that these values should be taken as preliminary as only two helium partial pressures have been studied so far and there are large uncertainties in analyzing powdered samples. Oxygen Fugacity: Experiments on Fe-bearing and Fe-free olivine as well as at varying oxygen fugacity indicate that at least some He is located in vacancies associated with Fe3+ in the olivine crystal lattice. A single experiment at the QFM buffer suggests a DHe at 1 atm. of ~0.001, a factor of 2-3 lower than at Ni-NiO. Assuming that the measured Henry's law constant is valid at high pressure, that mantle melting takes place between temperatures of 1200 and 1450° C and that fO2 conditions are near the QFM buffer, our experiments suggest D values during mantle melting of 0.001 to 0.002.

Parman, S. W.; Kurz, M. D.; Hart, S. R.; Grove, T. L.

2005-12-01

188

Electron impact ionization of helium isoelectronic systems  

International Nuclear Information System (INIS)

The electron impact single ionization cross sections, on the helium isoelectronic He, Li1+, B3+, C4+ N5+ O6+ Ne8+, Na9+. Ar+16, Fe24+, Mo41+ Ag45+, and U90+ 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)

2008-01-01

189

Cryogenic turbomachines for helium refrigeration system  

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-09-01

190

Helium stratification in HD 145792: a new Helium strong star  

CERN Multimedia

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...

Catanzaro, G

2007-01-01

191

Ultra-cold neutron production with superfluid helium and spallation neutrons  

CERN Multimedia

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

Masuda, Y

2000-01-01

192

Persistent currents in a rotating superleak partially filled with superfluid helium. Interim report  

Energy Technology Data Exchange (ETDEWEB)

Persistent currents in a partially helium II filled rotating super-leak have been investigated. Measurements were made using the acoustic doppler shift of the thickness wave in the helium II film which covers the alumina powder grains (1 micron) of the superleak. The existence of a potential flow region (Landau region) was established and measured at low rotational speeds (below 0.5 Hz). The decay rates of persistant current velocities were measured over almost five decades of time. We found a one-to-one correspondence with our system and that of a helium II filled superleak and also to the analogous quantities in an irreversible type-II superconductor.

Marcus, J.S.

1982-12-01

193

Schemes for reduction of helium ash in a fusion reactor  

Energy Technology Data Exchange (ETDEWEB)

For the reduction of helium ash in a fusion reactor, several methods have been proposed. These methods are systematically discussed based upon the density balance of heliums, e.g. the term of the helium flow from the divertor to the core plasma. In addition, it is shown that the emission of heliums retained in the wall may largely enhance the helium ash level. Then, the helium retention in the wall during the plasma discharge shot has to be sufficiently reduced. (author).

Hino, Tomoaki [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering

1995-10-01

194

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

Energy Technology Data Exchange (ETDEWEB)

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

Kato, D.; Saji, N.; Ohya, H.; Asakura, H.; Kubota, M.; Kaneko, Y.; Nagai, S. [Ishikawajima-Harima Heavy Industries Co., Ltd., Tokyo (Japan)

1994-12-31

195

Anomalous effects involving excess power, radiation, and helium production during D2O electrolysis using palladium cathodes  

International Nuclear Information System (INIS)

Previous experiments showed that eight electrolysis gas samples collected during episodes of excess power production in two identical cells contained measurable amounts of 4He while six control samples gave no evidence for helium. However, the detection limit for helium could not be defined clearly. This study of helium diffusion into the Pyrex glass sample flasks establishes a minimum helium detection limit of 3 x 1013 atom/ 500 ml (3 ppb) for these experiments. New D2O and H2O control experiments involving helium measurements of electrolysis gas samples collected in metal flasks support this conclusion. This places the 4He production rate at 1011 and 1012 atom/s per watt of excess power, which is the correct magnitude for typical fusion reactions that yield helium as a product. Simultaneous evidence for excess power, helium production, and anomalous radiation was present in these experiments. Completely new experiments with more precise helium measurements are reported that again show simultaneous evidence for excess power, helium production, and anomalous radiation. 22 refs., 5 figs., 4 tabs.

1994-01-01

196

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

International Nuclear Information System (INIS)

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

1977-01-01

197

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

International Nuclear Information System (INIS)

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

1997-01-01

198

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-10-01

199

Helium-3 blankets for tritium breeding in near-term fusion devices  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this paper is to propose a novel blanket concept for in-situ tritium breeding in a near-term device such as ITER. In this concept terrestrial supplies of helium-3, rather than lithium, are used for tritium breeding. In order to assess the key characteristics of this concept, a reference configuration was adopted based on minor modifications to the helium-cooled blanket concepts considered in the Blanket Comparison and Selection Study. The chosen configuration assumes a ferritic steel for structure and cladding and beryllium for neutron multiplication. The helium-3 is contained in a loop separate from the helium-4 coolant loop and flows within the beryllium. The helium-3 blanket exhibits good tritium breeding potential and low tritium inventories and leakage rates. The helium-3 requirements are 25-50 kg of inventory and 3.4-8.5 kg makeup/yr, 95% of which is due to burnup. It is estimated that there is sufficient helium-3 from decay of present military tritium stockpiles to meet this requirement. (orig.).

Steiner, D.; Embrechts, M.J.; Varsamis, G.; Vesey, R. (Rensselaer Polytechnic Inst., Troy, NY (USA). Dept. of Nuclear Engineering and Engineering Physics); Gierszewski, P. (Canadian Fusion Fuels Technology Project (CFFTP), Mississauga, ON (Canada)); Wong, C.P.C. (GA Technologies, Inc., San Diego, CA (USA))

1989-04-01

200

Helium Release from Radioisotope Heat Sources.  

Science.gov (United States)

Diffusion of helium in exp 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 spectrome...

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

1984-01-01

 
 
 
 
201

Power for the Fermilab Tevatron helium liquefier  

International Nuclear Information System (INIS)

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

1979-01-01

202

Properties and problems of helium stars  

International Nuclear Information System (INIS)

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

1975-01-01

203

Helium Speech: An Application of Standing Waves  

Science.gov (United States)

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

Wentworth, Christopher D.

2011-01-01

204

Helium solubility and behaviour in uranium dioxide  

International Nuclear Information System (INIS)

A set of devices was developed in order to infuse UO2 disks with helium, at high temperature and pressure, to measure the helium infused quantity and from these data to calculate the helium solubility in the UO2 matrix. Samples of UO2 single crystal and UO2 polycrystal were infused at a temperature of 1473 and 1743 K in a helium atmosphere ranging between 50 and 100 MPa. These samples were then annealed and the helium released was measured with a mass spectrometer. From the obtained spectra it was possible to give an interpretation of the helium release mechanism and to calculate its solubility in the UO2 lattice in these specific thermodynamic conditions. Additionally to the helium solubility measurement from infused samples, a 37 years old sample of 238PuO2, retrieved from an old 242Cm radioisotope thermoelectric generator (RTG), containing radiogenic helium, was also measured to widen perspectives of this kind of measurements to damaged sample more representative of spent fuel.

2009-03-31

205

Helium abundances and the helium isotope anomaly of sdB stars  

CERN Document Server

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.

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

2011-01-01

206

Relativistic calculations of transition amplitudes in the helium isoelectronic sequence  

International Nuclear Information System (INIS)

The helium atom and helium-like ions occupy a special position in atomic physics as the simplest multielectron systems. Unlike atoms and ions with many electrons, the fact that only two electrons are present allows calculations of extremely high accuracy to be carried out in the nonrelativistic case. At low Z, the leading relativistic and QED corrections can be calculated as perturbations. However, at higher Z it is desirable to start from a completely relativistic formalism. A well-known problem of any such formalism is the correct treatment of negative-energy states, which, if included improperly, lead to the continuum dissolution problem discussed by Sucher. This problem can be avoided by using the no-pair Hamiltonian, which excludes negative-energy states. Configuration interaction (CI) techniques were used to carry out accurate calculations of energies of n = 1 and n = 2 states along the helium isoelectronic sequence, starting from the no-pair Hamiltonian. Similar calculations were carried out in using interactive techniques. It is the purpose of this chapter to extend these calculations to evaluate transition amplitudes along the helium isoelectronic sequence. Specifically, we present highly accurate theoretical calculations of single-photon transition amplitudes and transition rates for 2-2 and 2-1 transitions in helium-like ions with charges in the range Z = 2-100. Amplitudes for the electric-dipole (E1) transitions 21P1 ? 1 1So, 21P1 ? 21So, 23Po,1,2 ? 23S1, w1P1 ?, and 23P1 ? 11So are calculated in length form and in velocity form. Amplitudes for the magnetic-dipole M1 transitions 23S1? 1 1So and the magnetic-quadrupole (M2) transitions 23P2 ? 1 1So are evaluated in velocity form. 78 refs., 5 figs., 16 tabs

1995-01-01

207

Helium-cooled lithiuim compound suspension blanket concept for ITER  

International Nuclear Information System (INIS)

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

1988-01-01

208

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1992-06-30

209

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

Science.gov (United States)

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

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

1992-06-01

210

Equation of state of fluid helium at high temperatures and densities  

Science.gov (United States)

Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2, and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., the D ? u relation, D= C 0+? u ( u18000 K and the ionization degree of the shocked gas helium reaches 10-3.

Cai, Lingcang; Chen, Qifeng; Gu, Yunjun; Zhang, Ying; Zhou, Xianming; Jing, Fuqian

2005-03-01

211

Photochemistry inside superfluid helium nano droplets  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2007-07-01

212

Synergistic effects in hydrogen-helium bubbles.  

UK PubMed Central (United Kingdom)

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

Hayward E; Deo C

2012-07-01

213

Cellular effects of helium in different organs.  

UK PubMed Central (United Kingdom)

Experimental research in cardiac and neuronal tissue has shown that besides volatile anesthetics and xenon, the nonanesthetic noble gas helium also reduces ischemia-reperfusion damage. Even though the distinct mechanisms of helium-induced organ protection are not completely unraveled, several signaling pathways have been identified. Beside the protective effects on heart and brain that are mainly obtained by different pre- and postconditioning protocols, helium also exerts effects in the lungs, the immune system, and the blood vessels. Obviously, this noble gas is biochemically not inert and exerts biologic effects, although until today the question remains open on how these changes are mediated. Because of its favorable characteristics and the lack of hemodynamic side effects, helium is suitable for use also in critically ill patients. This review covers the cellular effects of helium, which may lead to new clinical strategies of tissue salvage in ischemia-reperfusion situations, both within and outside the perioperative setting.

Oei GT; Weber NC; Hollmann MW; Preckel B

2010-06-01

214

Primordial helium and the cosmic background radiation  

Science.gov (United States)

The products of primordial nucleosynthesis, along with the cosmic microwave background (CMB) photons, are relics from the early evolution of the Universe whose observations probe the standard model of cosmology and provide windows on new physics beyond the standard models of cosmology and of particle physics. According to the standard, hot big bang cosmology, long before any stars have formed a significant fraction ( ~ 25%) of the baryonic mass in the Universe should be in the form of helium-4 nuclei. Since current observations of 4He are restricted to low redshift regions where stellar nucleosynthesis has occurred, an observation of high redshift, prestellar, truly primordial 4He would constitute a fundamental test of the hot, big bang cosmology. At recombination, long after big bang nucleosynthesis (BBN) has ended, the temperature anisotropy spectrum imprinted on the CMB depends on the 4He abundance through its connection to the electron density and the effect of the electron density on Silk damping. Since the relic abundance of 4He is relatively insensitive to the universal density of baryons, but is sensitive to a non-standard, early Universe expansion rate, the primordial mass fraction of 4He, Yp, offers a test of the consistency of the standard models of BBN and the CMB and, provides constraints on non-standard physics. Here, the WMAP seven year data (supplemented by other CMB experiments), which lead to an indirect determination of Yp at high redshift, are compared to the BBN predictions and to the independent, direct observations of 4He in low redshift, extragalactic HII regions. At present, given the very large uncertainties in the CMB-determined primordial 4He abundance (as well as for the helium abundances inferred from HII region observations), any differences between the BBN predictions and the CMB observations are small, at a level lap1.5?.

Steigman, Gary

2010-04-01

215

Helium/radon precursory signals of Chamoli Earthquake, India  

International Nuclear Information System (INIS)

The Bhagirthi and Alaknanda valleys of Garhwal Himalaya, were rocked, respectively, by two major earthquakes: the Uttarkashi earthquake of magnitude mb=6.5, Ms=7.0 on October 20, 1991 and the Chamoli earthquake of mb=6.8, Ms=6.5 on March 29, 1999, during this decade. Both these seismic events are associated with ongoing deformation along the main central thrust of the Himalayas. Helium and radon anomalies on March 24 and March 27, 1999, respectively, were recorded at Palampur which is about 393 km from the Chamoli earthquake epicentre. A He/Rn ratio anomaly was recorded on March 20, 9 days before the Chamoli earthquake. The precursory nature of radon and helium anomalies is a strong indicator of the physical basis of earthquake prediction and a preliminary test for the proposed conceptual He/Rn ratio model.

2001-01-01

216

Helium/radon precursory signals of Chamoli Earthquake, India  

Energy Technology Data Exchange (ETDEWEB)

The Bhagirthi and Alaknanda valleys of Garhwal Himalaya, were rocked, respectively, by two major earthquakes: the Uttarkashi earthquake of magnitude m{sub b}=6.5, M{sub s}=7.0 on October 20, 1991 and the Chamoli earthquake of m{sub b}=6.8, M{sub s}=6.5 on March 29, 1999, during this decade. Both these seismic events are associated with ongoing deformation along the main central thrust of the Himalayas. Helium and radon anomalies on March 24 and March 27, 1999, respectively, were recorded at Palampur which is about 393 km from the Chamoli earthquake epicentre. A He/Rn ratio anomaly was recorded on March 20, 9 days before the Chamoli earthquake. The precursory nature of radon and helium anomalies is a strong indicator of the physical basis of earthquake prediction and a preliminary test for the proposed conceptual He/Rn ratio model.

Virk, H.S. E-mail: virkhs@yahoo.comhsvirk@excite.com; Walia, V

2001-06-01

217

Exotic helium molecules; Molecules exotiques d'helium  

Energy Technology Data Exchange (ETDEWEB)

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)

Portier, M

2007-12-15

218

Ground State Hyperfine Structure of Muonic Helium Atom  

CERN Multimedia

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

Krutov, A A

2007-01-01

219

Velocity distribution of H+ ions under runaway conditions in helium  

International Nuclear Information System (INIS)

The velocity distribution of H+ ions in helium has been obtained using the Monte Carlo method for ratios of the electric field to gas number density E/N from 5.65-56.6 Td. The discrepancies in the velocity distributions between runaway conditions and non-runaway conditions are considered. In the case of the runaway conditions, the velocity distribution has elongated tails in all directions and the tail in the direction of the electric field is especially elongated. (author).

1988-01-01

220

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

Science.gov (United States)

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

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

2013-02-28

 
 
 
 
221

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

UK PubMed Central (United Kingdom)

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

Timilsina R; Smith DA; Rack PD

2013-03-01

222

Shape of atomic lines emitted by cryoplasma in Helium  

International Nuclear Information System (INIS)

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

2012-12-06

223

Shape of atomic lines emitted by cryoplasma in Helium  

Science.gov (United States)

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

Bonifaci, N.; Aitken, F.; Van Nguyen, Hai; Atrazhev, V. M.; von Haeften, K.; Rincon, R.

2012-12-01

224

Helium two-phase instabilities  

International Nuclear Information System (INIS)

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

1979-01-01

225

Helium isotopes in an aurora  

International Nuclear Information System (INIS)

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

1976-01-01

226

Helium migration in alpha-irradiated beryllium  

International Nuclear Information System (INIS)

Mass-spectrometric investigation of the kinetics of helium emission from beryllium specimens has been carried on. Helium was introduced by means of specimen irradiation with alpha particles at the Van de Graaff accelerator. An equation of gaseous diffusion to vacuum from a plate with a limited and localized quantity of diffusing substance has been solved. It is shown by means of a model calculation using an electronic computer that the whole gas emission occurs practically through a surface which are the nearest to a saturation layer. Parameters o a temperature dependence of helium diffusion in beryllium in a wide temperature range (650-1150 deg) have been calculated from kicetic curves. It is concluded on the basis of a low value of helium diffusion activation energy in beryllium at annealing temperatures below 900 deg C that there is helium migration over interstitials or in the form of helium atom complexes with vacancies. Considerable increase of helium yield at temperatures above 900 deg C is attributed to increase in the yield surface and reduction of a diffusion path at the expense of ''irreversible'' structural changes in beryllium

1981-01-01

227

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

International Nuclear Information System (INIS)

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

1993-01-01

228

Trapping and diffusion of helium in lunar minerals  

Science.gov (United States)

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

Harris-Kuhlman, Kimberly Renae

229

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

International Nuclear Information System (INIS)

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

2011-10-01

230

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-08-01

231

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

International Nuclear Information System (INIS)

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

1999-01-01

232

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

Energy Technology Data Exchange (ETDEWEB)

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

SHERRELL, D.L.

1999-09-21

233

Characteristics of an activated carbon monolith for a helium adsorption compressor  

Energy Technology Data Exchange (ETDEWEB)

An activated carbon monolith (ACM) with a high helium adsorption/desorption capacity, high density, low pressure drop, low thermal expansion and good mechanical properties was prepared and applied successfully in a helium adsorption compressor as a part of a 4.5 K sorption cooler. The activated carbon (AC) used in the monolith preparation was selected from a series of ACs prepared from an anthracite and bituminous coals activated using KOH, NaOH and CO{sub 2}, and having a variety of surface areas, micropore size distributions and packing densities. The selected AC was combined with a binder to prepare an ACM with suitable mechanical properties for machining. The results of this study, related to an helium sorption compressor includes: packing density, mechanical properties (compression strength, vibration tests), thermal expansion, pressure-drop measurements and also helium adsorption isotherms measured at high pressure (up to 35 bar) and low temperatures (from 20 K up to 150 K).

Lozano-Castello, D.; Jorda-Beneyto, M.; Cazorla-Amoros, D.; Linares-Solano, A.; Burger, J.F.; ter Brake, H.J.M.; Holland, H.J. [University of Alicante, Alicante (Spain)

2010-01-15

234

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

Science.gov (United States)

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

Fradera, J.; Sedano, L.; Mas de Les Valls, E.; Batet, L.

2011-10-01

235

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-28

236

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

International Nuclear Information System (INIS)

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

2011-04-01

237

Helium transport and exhaust in tokamak experiments  

International Nuclear Information System (INIS)

[en] This workshop was devoted to updating the helium experiments and experimental planning conducted since the time of the previous workshop on this topic, and was sponsored jointly by Forschungszentrum Juelich and Oak Ridge National Laboratory. The main goals were to summarize work on helium problems presented at the 10th International Conference on Plasma-Surface Interactions, work done since the previous workshop, to introduce new helium issues, to discuss experiment planned for the next 1-2 years, to describe modelling advances and to discuss plans for future workshops on this topic. This report briefly summarizes the presentations during the workshop

1992-01-01

238

Kilohertz laser ablation for doping helium nanodroplets  

CERN Multimedia

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

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

2007-01-01

239

Helium thermodesorption mechanism from irradiated boron carbide  

International Nuclear Information System (INIS)

The boron carbide powder, the particle size whereof constitutes about 10 ?m, is used as the WWER-1000 reactor absorption core. The model of the helium atoms activation yield from the accumulation centers and their diffusion to the surface of the boron carbide powder spherical particle is proposed. The evaluation of the helium yield from the material in the process of annealing is obtained. The effect of the powder grains size and change in the material temperature velocity on the helium thermodesorption from the irradiated boron carbide is evaluated

2005-01-01

240

Gearbox Scheme in High Temperature Reactor Helium Gas Turbine System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Helium Turbine is used in High Temperature Reactor Helium Gas Turbine (HTR-GT) system, by which the direct helium circulation between the reactor and turbine generator system will come true. Between helium turbine and generator, there is gearbox device which reduces the turbine rotation speed to nor...

Sheng Liu; Xuanyu Sheng

 
 
 
 
241

Genetic changes in Mammalian cells transformed by helium cells  

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-11-01

242

Electrical heater for very-low pressure helium gas  

CERN Multimedia

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

Benda, V; Vuillierme, B

1996-01-01

243

Failure of choroidal melanoma to respond to helium ion therapy  

Energy Technology Data Exchange (ETDEWEB)

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

Char, D.H.; Crawford, J.B.; Castro, J.R.; Woodruff, K.H.

1983-02-01

244

Failure of choroidal melanoma to respond to helium ion therapy  

International Nuclear Information System (INIS)

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

1983-01-01

245

Neovascular glaucoma after helium ion irradiation for uveal melanoma  

Energy Technology Data Exchange (ETDEWEB)

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

Kim, M.K.; Char, D.H.; Castro, J.L.; Saunders, W.M.; Chen, G.T.; Stone, R.D.

1986-02-01

246

Neovascular glaucoma after helium ion irradiation for uveal melanoma  

International Nuclear Information System (INIS)

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

1986-01-01

247

LOCA analysis for Korean helium cooled solid breeder TBM  

International Nuclear Information System (INIS)

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

2009-01-01

248

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

International Nuclear Information System (INIS)

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

1985-07-22

249

Turbulence measurements in axisymmetric jets of air and helium  

Science.gov (United States)

Turbulent axisymmetric jets of air helium with the same nozzle momentum flux were studied experimentally using hot-wire probes. An X-wire hot-wire probe was used in the air jet and a composite probe consisting of an X-wire and an interference probe of the Way-Libby type was used in the helium jet to measure the helium concentration and two velocity components. Moments of turbulent fluctuations, up to fourth order, were calculated to characterize turbulent transport in the jet and to evaluate current models for triple moments that occur in the Reynolds stress equation. In the air jet, the momentum flux across the jet was found to be within +/- 5 percent of the nozzle input and the integral of the radial diffusive flux of the turbulent kinetic energy across the jet was found to be close to zero indicating consistency of measurements with the equations of motion. The fourth moments were very well described in terms of the second moments by the quasi-Gaussian approximation across the entire jet. Profiles of third moments were found to be significantly different from earlier measurements - (u(v exp 2)) (u(w exp 2)) and ((u exp 2)v) were found to be negative near the axis of the jet. The measurements in the helium jet were in the intermediate region between the non-buoyant jet and the plume regions. The helium mass flux across the jet was found to be within +/- 0 percent of the nozzle input. The far field behavior was in accord with the expected plume scalings. The near field behavior of the mean velocity along the axis of the jet follows the scaling expressed by the effective diameter but the mean concentration decay has a different density ratio dependence. The radical profiles of mean velocity and concentration indicate a turbulent Schmidt number of 0.7, the same as for passive scalars in round jets. Turbulent intensity of axial velocity fluctuations was significantly higher than that observed in the air jet while the radial and azimuthal intensities are virtually identical with the air jet when scaled with the half-widths. Two models for triple moments were evaluated with measurements in both air and helium jets.

Panchapakesan, N. R.

250

RAPID COMMUNICATION: Electron swarm parameters in ? and helium gas mixtures  

Science.gov (United States)

A new set of swarm data in 0022-3727/32/5/004/img2 and helium were experimentally determined by the pulsed Townsend method over the range 0022-3727/32/5/004/img3 Td (1 Td 0022-3727/32/5/004/img4 V 0022-3727/32/5/004/img5): the effective ionization coefficient 0022-3727/32/5/004/img6, the drift velocity 0022-3727/32/5/004/img7 and the longitudinal diffusion coefficient 0022-3727/32/5/004/img8. The limiting 0022-3727/32/5/004/img9 values of 0022-3727/32/5/004/img2-He gas mixtures were derived from the experiment and found to vary linearly with the 0022-3727/32/5/004/img2 concentration in the mixtures.

Xiao, D. M.; Zhu, L. L.; Chen, Y. Z.

1999-03-01

251

Helium cosmic ray flux measurements at Mars  

International Nuclear Information System (INIS)

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

2006-01-01

252

Helium cosmic ray flux measurements at Mars  

Energy Technology Data Exchange (ETDEWEB)

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

Lee, Kerry [University of Houston, 4800 Calhoun Rd. Houston, TX 77204 (United States)]. E-mail: ktlee@ems.jsc.nasa.gov; Pinsky, Lawrence [University of Houston, 4800 Calhoun Rd. Houston, TX 77204 (United States); Andersen, Vic [University of Houston, 4800 Calhoun Rd. Houston, TX 77204 (United States); Zeitlin, Cary [National Space Biomedical Research Institute, Baylor College of Medicine, Houston, TX (United States); Cleghorn, Tim [NASA Johnson Space Center, 2101 NASA Road 1, Houston, TX 77058 (United States); Cucinotta, Frank [NASA Johnson Space Center, 2101 NASA Road 1, Houston, TX 77058 (United States); Saganti, Premkumar [Prairie View A and M University, P.O. Box 519, Prairie View, TX 77446-0519 (United States); Atwell, William [The Boeing Company, Houston, TX (United States); Turner, Ron [Advancing National Strategies and Enabling Results (ANSER), Arlington, Virginia (United States)

2006-10-15

253

Anomalously long-lived antiprotonic helium atom  

International Nuclear Information System (INIS)

[en] Recently anomalously long-lived states of antiprotonic atoms in helium media have been discovered. The structure, formation/reaction and spectroscopy of these metastable atoms are discussed. (author)

1992-01-01

254

Failure analysis of welded helium tanks  

International Nuclear Information System (INIS)

[en] Two tanks, one, the helium recirculating tank and the other, the helium pump-up tank of a pressurised heavy water reactor tested at low pressure had shown a number of leaks at dished ends and nozzles. These two tanks were made of AISI type 304 stainless steel. This note briefly discusses the results of the detailed failure analysis of these tanks undertaken to assess the nature and the cause of failure. (orig./HOE)[de] Der Helium-Rezirkulationstank und der Helium-Pumptank eines Schwerwasser-Druckreaktors, die bei niedrigen Druekken getestet wurden, zeigten zahlreiche Undichtigkeiten an den gewoelbten Seitenflaechen und den Stutzen. Die Tanks bestanden aus dem rostfreien Stahl AISI 304. In dieser Arbeit werden die Ergebnisse einer genauen Schadensanalyse, die an diesen Tanks zur Klaerung der Schadensursache durchgefuehrt wurden, kurz diskutiert. (orig./HOE)

1983-01-01

255

Depolarized Rayleigh scattering in helium II  

International Nuclear Information System (INIS)

[en] Depolarized Rayleigh scattering in helium due to the fluctuations of the phonon distribution function is considered. The spectral and total extinction coefficients are calculated in the case of scattering of a linearly polarized wave

1984-01-01

256

Fluidization of granulates wetting by liquid helium  

Energy Technology Data Exchange (ETDEWEB)

To fluidize wet granulates by vertical vibration, extra force is necessary to overcome the capillary force. We explore experimentally the fluidization of a granulate wetted by liquid Helium, because of its special liquid properties. By varying temperature around the {gamma} point, we study how liquid Helium changes the dynamic properties of granulates. For superfluid wetting, the critical acceleration for fluidization increases almost linearly with film thickness. This indicates that superfluid starts to flow and forms liquid bridges. For wetting by normal fluid Helium, the critical acceleration shows a relatively steep increase close to saturation. Above saturation, both superfluid and normal fluid give rise to a plateau of the critical acceleration, because the capillary force depends only weakly on the volume of the bridge. The plateau value is found to vary with temperature and shows a peak around the {gamma} point, which indicates the influence of the specific heat of liquid Helium.

Huang, Kai; Sohaili, Masoud; Herminghaus, Stephan [Max Planck Institute for Dynamics and Self-Organization, Goettingen (Germany)

2008-07-01

257

Helium release from type 304 stainless steel  

International Nuclear Information System (INIS)

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

1975-10-01

258

Inelastic Scattering of Electrons by Helium.  

Science.gov (United States)

Bethe-Goldstone continuum equations for the scattering of electrons from helium are solved variationally in the energy range between the n = 2 and n = 3 thresholds. Polarization and correlation effects are included in the calculations by allowing for virt...

R. S. Oberoi R. K. Nesbet

1973-01-01

259

Helium pumping with liquid ring vacuum pump  

International Nuclear Information System (INIS)

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

1983-01-01

260

Photoelectron Spectroscopy of Doped Helium Nanodroplets  

International Nuclear Information System (INIS)

[en] The photoionization dynamics of aniline doped helium droplets has been investigated by photoelectron spectroscopy. The photoelectron spectra resemble closely that of gas phase aniline, except for a droplet-size-dependent shift. This shift is caused by lowering of the ionization threshold upon solvation and can be readily estimated. The individual peaks in the photoelectron spectrum are broadened towards lower kinetic energy which is attributed to the relaxation of the photoelectrons as they pass through the helium droplet

2005-10-14

 
 
 
 
261

Helium-propane as drift chamber gas  

International Nuclear Information System (INIS)

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

1985-01-01

262

Helium accumulation in groundwater. Pt. 3. Limits on helium transfer across the mante-crust boundary beneath Australia and the magnitude of mantle degassing  

Energy Technology Data Exchange (ETDEWEB)

The groundwaters of the Great Artesian Basin (Australia) have been previously shown to be accumulating in-situ production helium for groundwaters ages <50 kyr and an external helium flux equivalent to whole crustal production for groundwater ages >100 kyr. New helium isotope measurements show that the observed in-situ production helium (/sup 3/He//sup 4/He approx. = 1.6 x 10/sup -8/) is isotopically distinct from the crustal degassing helium flux (/sup 3/He//sup 4/He approx. = 6.6 x 10/sup -8/). Furthermore, the crustal degassing helium isotope ratio is marginally in excess of the whole crustal production ratio (/sup 3/He//sup 4/He = 3.5 x 10/sup -8/) and the production ratio in a variety of continental rock types. This suggests that the upper limit on volatile transport across the mantle-crust boundary beneath the (relatively) stable and 'complacent' Australian continent can be characterized by a 'conductive-diffusive' helium/heat flux ratio of < or approx.2.6 x 10/sup 6/ /sup 4/He atoms mW/sup -1/s/sup -1/ which is two orders of magnitude less than the 'intrusive-volcanic' ratio of 2.9 x 10/sup 8/ /sup 4/He atoms mW/sup -1/s/sup -1/ measured at the Galapagos. These results constrain the transcrustal mantle degassing fluxes of /sup 4/He and /sup 40/Ar to be much less than the mid-ocean ridge degassing fluxes; which are much less than the degassing of /sup 4/He and /sup 40/Ar from continental crust. Thus, the degassing of the Earth's interior is dominated by magmatic processes but the dominant fluxes of /sup 4/He and /sup 40/Ar to the atmosphere must come from the continental crust.

Torgersen, T.; Clarke, W.B.

1987-07-01

263

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

International Nuclear Information System (INIS)

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

1985-01-01

264

Sonic helium detectors in the Fermilab Tevatron  

Energy Technology Data Exchange (ETDEWEB)

In the Fermilab Tevatron cryogenic system there are many remotely located low-pressure plate relief valves that must vent large volumes of cold helium gas when magnet quenches occur. These valves can occasionally stick open or not reseat completely, resulting in a large helium loss. As such, the need exists for a detector to monitor the relief valve's discharge area for the presence of helium. Due to the quantity needed, cost is an important factor. A unit has been developed and built for this purpose that is quite inexpensive. Its operating principle is based on the speed of sound, where two closely matched tubes operate at their acoustic resonant frequency. When helium is introduced into one of these tubes, the resulting difference in acoustic time of flight is used to trigger an alarm. At present, there are 39 of these units installed and operating in the Tevatron. They have detected many minor and major helium leaks, and have also been found useful in detecting a rise in the helium background in the enclosed refrigerator buildings. This paper covers the construction, usage and operational experience gained with these units over the last several years.

Bossert, R.J.; /Fermilab

2006-01-01

265

The role of helium gas in medicine  

Science.gov (United States)

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

2013-01-01

266

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

International Nuclear Information System (INIS)

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

1989-01-01

267

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

International Nuclear Information System (INIS)

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

1990-01-01

268

The Green Bank Telescope H II Region Discovery Survey. IV. Helium and Carbon Recombination Lines  

Science.gov (United States)

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

Wenger, Trey V.; Bania, T. M.; Balser, Dana S.; Anderson, L. D.

2013-02-01

269

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

International Nuclear Information System (INIS)

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

1996-01-01

270

Constraints on hydrothermal processes and water exchange in Lake Vostok from helium isotopes.  

UK PubMed Central (United Kingdom)

Lake Vostok, the largest subglacial lake in Antarctica, is covered by the East Antarctic ice sheet, which varies in thickness between 3,750 and 4,100 m (ref. 1). At a depth of 3,539 m in the drill hole at Vostok station, sharp changes in stable isotopes and the gas content of the ice delineate the boundary between glacier ice and ice accreted through re-freezing of lake water. Unlike most gases, helium can be incorporated into the crystal structure of ice during freezing, making helium isotopes in the accreted ice a valuable source of information on lake environment. Here we present helium isotope measurements from the deep section of the Vostok ice core that encompasses the boundary between the glacier ice and accreted ice, showing that the accreted ice is enriched by a helium source with a radiogenic isotope signature typical of an old continental province. This result rules out any significant hydrothermal energy input into the lake from high-enthalpy mantle processes, which would be expected to produce a much higher 3He/4He ratio. Based on the average helium flux for continental areas, the helium budget of the lake leads to a renewal time of the lake of the order of 5,000 years.

Jean-Baptiste P; Petit JR; Lipenkov VY; Raynaud D; Barkov NI

2001-05-01

271

Helium, hydrogen, and oxygen velocities observed in ISEE 3  

Energy Technology Data Exchange (ETDEWEB)

The velocities of helium, oxygen, and hydrogen ions have been recorded over a full range of solar wind conditions by the ion composition instrument (ICI) and Los Alamos National Laboratory plasma instrument (LANLPI), respectively, aboard the ISEE 3 spacecraft between August 1978 and December 1979. Interspecie velocity differences were observed frequently. For solar wind velocities between 300 and 400 km s/sup -1/ the velocity exceeded the hydrogen velocity by 5 km s/sup -1/ on the average. For solar wind velocities between 400 and 500 km s/sup -1/ the average difference was 14 km s/sup -1/; however, no evidence was found for a systematic nonzero average difference between helium and oxygen ions even at the higher velocities. Velocity differences were examined in a number of streams and across a number of interplanetary shocks. Helium-hydrogen velocity differences are generally bounded by the Alfven speed. Velocity differences show abrupt changes across interplanetary discontinuities, persumably tangential. Differences between the speeds of differently charged minor ions appear also to result from the electrostatic potential differences across the interplanetary shocks. The potential difference, calculated from the energy jump condition for a perpendicular hydromagnetic shock, is of the correct magnitude to produce the observed effects.

Ogilvie, K.W.; Coplan, M.A.; Zwickl, R.D.

1982-09-01

272

Abundance analyses of helium-rich subluminous B stars  

CERN Document Server

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...

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

2010-01-01

273

Helium-neon laser improves skin repair in rabbits.  

UK PubMed Central (United Kingdom)

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

Peccin MS; Renno AC; de Oliveira F; Giusti PR; Ribeiro DA

2012-12-01

274

Helium-neon laser improves skin repair in rabbits.  

Science.gov (United States)

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

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

2012-12-01

275

Primordially produced helium-4 in the presence of neutrino oscillations  

International Nuclear Information System (INIS)

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

2001-01-01

276

Lung Function Measurement with Multiple-Breath-Helium Washout System  

CERN Multimedia

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

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

2011-01-01

277

Lung function measurement with multiple-breath-helium washout system.  

UK PubMed Central (United Kingdom)

Multiple-breath-washout (MBW) measurements are regarded as a sensitive technique which can reflect the ventilation inhomogeneity of respiratory airways. Typically nitrogen is used as the tracer gas and is washed out by pure oxygen in multiple-breath-nitrogen washout (MBNW) tests. In this study, instead of using nitrogen, (4)He is used as the tracer gas with smaller gas density which may be able to reach deeper into our lungs in a given time and the helium washout results may be more sensitive to the ventilation inhomogeneity in small airways. A multiple-breath-helium-washout (MBHW) system developed for the lung function study is also presented. Quartz tuning forks with a resonance frequency of 32,768Hz have been used for detecting the change of the respiratory gas density. The resonance frequency of the quartz tuning fork decreases linearly with increasing density of the surrounding gas. Knowing the CO2 concentration from the infrared carbon dioxide detector, the helium concentration can be determined. Results from 14 volunteers (3 mild asthmatics, 4 tobacco smokers, 1 with asthma history, 1 with COPD history, 5 normal) have shown that mild asthmatics have higher ventilation inhomogeneity in either conducting or acinar airways (or both). A feature has been found in washout curve of single breaths from 4 tobacco smokers with different length of smoking history which may indicate the early stage of respiratory ventilation inhomogeneity in acinar airways.

Wang JY; Suddards ME; Mellor CJ; Owers-Bradley JR

2013-04-01

278

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-10-31

279

Helium isotope ratios in Japan sea water. Nihonkai kaisuichu no helium doitai hi  

Energy Technology Data Exchange (ETDEWEB)

The three straits, Soya, Tsugaru and Tsushima connecting the Japan Sea and the Pacific Ocean are all shallow and the water in the deep part of the Pacific Ocean cannot come directly into the Japan Sea. It is considered that the deep part of the Japan Sea is occupied by an uniform water mass and altenation of this water and the surface water is done in a short time. On the other hand, helium is the only component established to be originated in the mantle in the deep part of the earth among various geochemical parameters. In this article, in order to measure precisely the isotopic ratio of helium, the existing system was modified for conducting basic experiments and the measured results of the isotopic ratio of helium as well as the helium/neon ratio of the distilled water agreed well with documented values. Then helium concentrations, helium isotopic ratios and helium/neon ratios in the sea water taken from respective predetermined depths of the eastern edge of the Japan Sea were measured and with regard to concentration, changes were observed between those above and below 1,500m through 2,000m in depth. Also concerning the bottom layer water, discharge of mantle helium from the bottom of the Japan Sea is suggested. 21 refs, 3 figs, 2 tabs.

Sano, Yuji; Wakita, Hiroshi; Ishibashi, Juneichiro; Gamo, Toshitaka; Sakai, Hitoshi (The Univ. of Tokyo, Faculty of Science, Tokyo (Japan) Ocean Research Inst., The Univ. of Tokyo, Tokyo (Japan))

1989-12-30

280

The application of a condensable gas theory to thermal properties of helium-4 and helium-3  

Energy Technology Data Exchange (ETDEWEB)

A theory of condensable gases that takes into account density fluctuations when attractive forces have a limited range has been applied in a simple approximation to predict pressure isotherms of helium-4 and helium-3. The hard sphere model of the repulsive force has been studied for both fluids. For helium-4, besides the critical compressibility factor Z{sub c}, two more parameters are used to improve the numerical prediction within the region 0-2.4 {rho}{sub c}, 0.8-1.7 T{sub c}, and 0-10 P{sub c}. Comparison of the results of the theory and the experimental results reported in the literature for the above range has been made for helium-4. For helium-3, data are lacking except in a more limited range about the critical point. Reasonably good agreement is obtained with the available data using just Z{sub c} plus one more parameter.

Sheng Zhang; White, J.A.

1993-04-01

 
 
 
 
281

Accuracy of helium accumulation fluence monitor  

Energy Technology Data Exchange (ETDEWEB)

A He accumulation fluence monitor (HAFM) has been developed for neutron dosimetry and the direct measurement of He production in structural component materials used for fast reactors. As to accuracy of measuring helium atoms by the HAFM measurement system, previous study using He ions implanted samples shows that this system could measure He atoms within 5% error. In order to confirm the measurement accuracy of neutron fluence in the fast reactor, the HAFM samples were irradiated to a total fluence of 10{sup 15} - 10{sup 17} n/cm{sup 2} in the standard fast neutron spectrum field of the Fast Neutron Source Reactor `YAYOI` at University of Tokyo. Irradiated samples were measured by the HAFM measurement system and the He Atoms Measurement System (HAMS) at Kyushu University, and the measured values were compared with the calculated He productions. The principle results are summarized as follows: (1) It was confirmed that He production in {sup 10}B could be measured within 5% error by the HAFM system at the reactor core center or the experimental hole through the blanket where He were produced by neutron of 10 keV - 1 MeV and at Fast Column where He were produced by neutron less than 10 keV. (2) It was also found that He production in {sup 9}Be could be measured within 5% at the experimental hole through the blanket. Thus it is expected that Be could be applied to measurements of fast neutron of its energy over 1 MeV. (3) The differences between the measured values by the HAFM measurement system and those by HAMS were less than the experimental error, therefore it was confirmed that the measured values was reliable. (author)

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

1998-01-01

282

Special operations in the helium system, III-4  

International Nuclear Information System (INIS)

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

1989-01-01

283

Hydrodynamic simulations of the core helium flash  

CERN Document Server

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...

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

2009-01-01

284

Helium release from radioisotope heat sources  

International Nuclear Information System (INIS)

[en] Diffusion of helium in 238PuO2 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

1984-01-01

285

Helium release from radioisotope heat sources  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1984-05-01

286

Helium effects on microstructural evolution in tempered martensitic steels: in situ helium implanter studies in HFIR  

International Nuclear Information System (INIS)

[en] Full text of publication follows: Understanding, modeling and managing the effects of high levels of He and dpa on microstructural evolution and properties changes is a primary objective of fusion materials research. A novel in-situ 59Ni(n,?) reaction helium-implanter technique was used to characterize the effect of the He/dpa ratio on microstructural evolution and changes in the flow properties of various materials at fusion relevant dpa, dose rates and irradiation temperatures (Ti). Irradiations in the High Flux Isotope reactor (HFIR) resulted in a-implantation from thin 1 to 5 ?m thick NiAl coatings on TEM discs, producing uniform helium concentration of 5 to 50 appm He/dpa to a depth of 5 to 8 ?m. In this study we specifically explore the effect of He/dpa and Ti on the microstructure of Eurofer97 and F82H in the as-received and cold worked conditions. Cross-section Eurofer97 TEM specimens were examined in a JOEL 2010FE microscope under a variety of imaging conditions. Bubbles were found in the He-implanted region at all three Ti, with estimated maximum diameters of 10, 6.5 and 2.5 nm at 500 deg. C (?10 dpa and 380 appm He), 400 deg. (?4.3 dpa and 90 appm He) and 300 deg. C (?4.3 dpa and 90 and appm He), respectively. At the 500 deg. C 10 nm faceted cavities were observed, that may actually be voids. The other irradiated microstructures were also characterized, with special emphasis on the association of bubbles with other features. The effects of He/dpa and starting microstructure are examined in detail. Low-load microhardness measurements were used to assess the effects of He/dpa and Ti on irradiation induced strength elevations. The results are analyzed with a multi-scale model described in a companion paper. Another companion paper describes the effects of similar He implantation in nano-structured ferritic alloy, MA957. (authors)

2007-01-01

287

Helium turbine power generation in high temperature gas reactor  

International Nuclear Information System (INIS)

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

1995-01-01

288

Helium behaviour in nuclear waste materials  

International Nuclear Information System (INIS)

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

2008-01-01

289

Density limits in helium plasmas at JET  

International Nuclear Information System (INIS)

Recently at JET a pure helium campaign has been performed. The exploration of the density limit in L-mode limiter as well as L-mode and H-mode diverted plasmas was one of the main objectives. In L-mode plasmas the density can be increased until the total radiated power equals the heating power, hence the density limit is determined by a radiative collapse. When compared to deuterium plasmas the L-mode density limit in helium is twice as high. In H-mode no significant difference in the density limit process has been observed. The pedestal density just before the H to L-mode back transition is the same in deuterium and helium plasmas. The H to L-mode back transition is followed by a development of a MARFE [] which eventually leads to a density limit disruption.

2003-01-01

290

Stress distribution in helium-ion implantations  

International Nuclear Information System (INIS)

[en] The stress introduced into a material in a monoenergetic helium-ion implantation is calculated for an ion beam with a gaussian intensity distribution. An effective beam spot of the order of several millimeters was chosen as typical of blistering experiments. The sample is assumed to be semi-infinite and isotropic. The ion distribution is cylindrically symmetric with a gaussian depth profile. The parameters defining the distribution are consistent with incident ion energies of approximately 40 and approximately 400 keV in both nickel and niobium. The volume expansion caused by the implanted ions is assumed to be proportional to the local helium concentration; the validity of this assumption is discussed. The maximum shear stress is calculated as a function of depth, and the volume expansion per helium atom required to produce plastic deformation at the experimentally observed critical doses in niobium is found to be of the order of one atomic volume

1976-02-16

291

Primary neutral helium in the heliosphere  

CERN Multimedia

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.

Mueller, Hans-Reinhard

2012-01-01

292

Hysteresis phenomena in a boiling helium flow  

International Nuclear Information System (INIS)

[en] Hysteresis phenomena in charnels with boiling helium are investigated. The upflow of liquid helium occurs in a vertical heated stainless steel tube. During tests the thermal load was increased in succession up to the nucleate boliling and then gradually reduced. The data are presented for the atmospheric pressure and mass flow rates of 84-140 kg/(m2 x s). As the tests have shown, the heat transfer at helium boiling depends not only on the thermal load but on the direction of its chang, which leads to hysteresis of the nucleate boiling curve. Stability of the developed nucleate boiling regime is also investigated. The intermediate level of heat transfer has been obtained at a heat flux reduced down to 12 W/m2 and at its further increase. The hydraulic resistance is noticed to increase with the heat flux reduction

1985-01-01

293

Helium behaviour in nuclear waste materials  

Energy Technology Data Exchange (ETDEWEB)

Waste conditioning matrices like synthetic zirconolite (CaZrTi{sub 2}O{sub 7}) were fabricated and doped with either the short-lived alpha-emitters {sup 238}Pu or {sup 244}Cm, or with {sup 239}Pu to generate various amounts of helium and of alpha-damage. The samples were annealed in a Knudsen cell, and the helium desorption profiles interpreted in conjunction with parallel radiation damage and previous annealing behaviour studies. To understand the long term behaviour of spent nuclear fuel, UO{sub 2} samples doped with the alpha-emitters {sup 233}U, {sup 238}Pu have been investigated by transmission electron microscopy (TEM), by XRD and by thermal desorption spectroscopy. The release of helium has been explained by the recrystallization of amorphized zirconolite on one hand and partially during alpha-damage recovery in the case of the spent fuel. This study mostly highlights the correlation between restructuring of damaged materials and gas release.

Wiss, T.; Hiernaut, J.P.; Colle, J.Y.; Maugeri, E.; Raison, P.; Konings, R.; Rondinella, V.V. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany); Roudil, D.; Deschanel, X.; Peuget, S. [Commissariat a l' Energie Atomique, Centre de VALRHO, B.P. 30207 Bagnols-sur-Ceze (France)

2008-07-01

294

Catching proteins in liquid helium droplets  

CERN Multimedia

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.

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

2010-01-01

295

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

International Nuclear Information System (INIS)

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

2010-08-05

296

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

Energy Technology Data Exchange (ETDEWEB)

The objective of this work is to determine void structure, distribution, and density changes of several vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18-31 dpa at 425-600{degrees}C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible. For specimens irradiated to {approx}18-31 dpa at 500-600{degrees}C with a helium generation rate of 0.4-4.2 appm He/dpa, only a few helium bubbles were observed at the interface of grain matrices and some of the Ti(O,N,C) precipitates, and no microvoids or helium bubbles were observed either in grain matrices or near grain boundaries. Under these conditions, dynamically produced helium atoms seem to be trapped in the grain matrix without significant bubble nucleation or growth, and in accordance with this, density changes from DHCE and non-DHCE (negligible helium generation) were similar for comparable fluence and irradiation temperature. Only for specimens irradiated to {approx}31 dpa at 425{degrees}C, when helium was generated at a rate of 0.4-0.8 appm helium/dpa, were diffuse helium bubbles observed in limited regions of grain matrices and near {approx}15% of the grain boundaries in densities significantly lower than those in the extensive coalescences of helium bubbles typical of other alloys irradiated in tritium-trick experiments. Density changes of specimens irradiated at 425{degrees}C in the DHCE were significantly higher than those from non-DHCE irradiation. Microstructural evolution in V-4Cr-4Ti was similar for DHCE and non-DHCE except for helium bubble number density and distribution. As in non-DHCE, the irradiation-induced precipitation of ultrafine Ti{sub 5}Si{sub 3} was observed for DHCE at >500{degrees}C but not at 425{degrees}C.

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

1995-03-01

297

Helium and neon isotope geochemistry of some ground waters from the Canadian Precambrian Shield  

Science.gov (United States)

Ground waters in a Precambrian granitic batholith at the Whiteshell Nuclear Research Establishment (WNRE) in Pinawa, Manitoba contain between 5 × 10 -5 and 10 -1 cc STP/g H 2 O of radiogenic helium-4 but have relatively uniform 3 He/ 4 He ratios of between 0.6 × 10 -8 and 2.3 × 10 3 . The highest helium samples also contain radiogenic 21,22 Ne produced by ( , n ) or ( n , ) reactions with other isotopes. As much as 1.8 × 10 -9 cc STP / g H 2 O of excess 21 Ne and 3.8 × 10 -9 cc STP / gH 2 O of excess 22 Ne have been measured. Helium and 21 Ne ages of these ground waters, calculated on the basis of known crustal production rates of 4 He and 21 Ne, are unreasonably high (up to 2 × 10 5 years) and incompatible with the 14 C ages and other isotopic and hydrogeologic data. Uranium enrichment in the flow porosity of the granite may dominate 4 He and 21,22 Ne production in this granite and mask the contributions from more typical U and Th concentrations in the rock matrix. At the Chalk River Nuclear Laboratories in Ontario helium concentrations in ground waters in a Precambrian monzonitic gneiss range from 1.5 × 10 -7 to 8.7 × 10 -4 cc STP / g H 2 O with the 3 He/ 4 He ratios ranging from 2.0 × 10 -3 to 1.5 × 10 -7 . The highest helium concentrations may be attributable to the presence of a thick uraniferous pegmatite vein and yield helium ages more than two orders of magnitude higher than the 14 C ages. Application of He age dating equations to ground waters from Precambrian granitic rocks requires knowledge of the nature of uranium and thorium enrichment in the subsurface in order to select appropriate values for porosity and uranium and thorium concentration in the rock.

Bottomley, D. J.; Ross, J. D.; Clarke, W. B.

1984-10-01

298

Defects of ultrathin Cu films on Mo(1 1 0) studied by thermal helium desorption spectrometry  

Energy Technology Data Exchange (ETDEWEB)

Defects of ultrathin Cu films (3-200 A) deposited on Mo(1 1 0) at room temperature by e-beam evaporation in ultra-high vacuum are investigated using thermal helium desorption spectrometry. The samples are analysed with both 75 and 1000 eV He{sup +} implantation. Cu films transform into islands on annealing and the temperature of this transformation is strongly thickness dependent. Helium release from defects close to the surface of the Cu films ({approx}450 K), from monovacancies in as-deposited Cu film (50-200 A), and from defects close to the interface (800-1050 K) are identified. Annealing of monovacancies is mainly responsible for reduction in helium trapping in a 20 A Cu film prior to film islanding. There is an indication of retrapping of helium released from the first 5 A layer of the film in the defects located in the overlayers (5-95 A). Helium in the Cu films survives until the desorption temperature of the film (1200-1300 K).

Venugopal, V; Thijsse, B J, E-mail: B.J.Thijsse@tudelft.n [Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands)

2009-08-21

299

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-04-01

300

Recent advances in heat transfer to helium 1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Conditions of thermal exchange in helium 1 are reviewed. Pool boiling thermosiphon boiling, forced convection heat transfer. Relations between critical nucleate flux and some parameters are given. Use of hypercritical helium.

Johannes, C.

 
 
 
 
301

Surface effects on neutron scattering in helium films  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report a neutron scattering experiment on thin helium films deposited on exfoliated graphite. The results can be explained by taking into account the effects of Van der Waals forces between the substrate and the helium atoms.

Lambert, B.; Salin, D.; Joffrin, J.; Scherm, R.

302

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-03-28

303

A helium isotope cross-section study through the San Andreas Fault at seismogenic depths  

Science.gov (United States)

We have analyzed noble gas isotopes in 19 mud gas samples from 116-3943 m borehole depth of the San Andreas Fault Observatory at Depth (SAFOD) Main Hole in the context of origin and spatial variability of fluids occurring at seismogenic depths. The measured 3He/4He ratios range between 0.40 and 1.02 Ra (Ra is the atmospheric 3He/4He ratio of 1.39 × 10-6), with 4He/20Ne values between 0.33 and 4.92, revealing a mixture of three components to the total helium: (1) atmospheric helium, (2) helium with a crustal signature, and (3) mantle-derived helium. The air-corrected 3He/4He ratios fall between 0.2 Ra and 0.9 Ra. Samples from the 2117-3196 m depth show a relatively constant helium isotope composition (0.35-0.46 Ra), indicating that ˜5% of the helium in this section the Pacific Plate is derived from the mantle. The contribution of mantle-derived helium increases slightly in the transition from the Pacific Plate to the North American Plate and reaches maximal values of ˜12% on the North American Plate (below ˜3500 m borehole depth). On the basis of our observations, we suggest that the San Andreas Fault plays a role for fluid flux from greater depths, but higher amounts of mantle-derived fluids rise up through other, more permeable faults, situated on the North American Plate of the San Andreas Fault Zone (SAFZ). Lateral fluid dispersion at shallow depths through permeable country rock of the North American Plate may explain the observed increase in 3He/4He ratios with increasing distance to the SAF.

Wiersberg, Thomas; Erzinger, JöRg

2007-01-01

304

Helium-induced cardioprotection of healthy and hypertensive rat myocardium in vivo.  

UK PubMed Central (United Kingdom)

Helium protects healthy myocardium against ischemia/reperfusion injury by early and late preconditioning (EPC, LPC) and postconditioning (PostC). We investigated helium-induced PostC of the hypertensive heart and enhancement by addition of LPC and EPC. We also investigated involvement of signaling kinases glycogen synthase kinase 3 beta (GSK-3?) and protein kinase C-epsilon (PKC-?). To assess myocardial cell damage, we performed infarct size measurements in healthy Wistar Kyoto (WKY rats, n=8-9) and Spontaneous Hypertensive rats (SHR, n=8-9) subjected to 25 min ischemia and 120 min reperfusion. Rats inhaled 70% helium for 15 min after index ischemia (PostC), combined with 15 min helium 24h prior to index ischemia (LPC+PostC), a triple intervention with additional 3 short cycles of 5 min helium inhalation shortly before ischemia (EPC+LPC+PostC), or no further treatment. In WKY rats, PostC reduced infarct size from 46 ± 2% (mean ± S.E.M) in the control group to 29 ± 2%. LPC+PostC or EPC+LPC+PostC reduced infarct sizes to a similar extent (30 ± 3% and 32 ± 2% respectively). In SHR, EPC+LPC+PostC reduced infarct size from 53 ± 3% in control to 39 ± 3%, while PostC or LPC+PostC alone were not protective; infarct size 48 ± 4% and 44 ± 4%, respectively. Neither PostC in WKY rats nor EPC+LPC+PostC in SHR was associated with an increase in phosphorylation of GSK-3? and PKC-? after 15 min of reperfusion. Concluding, a triple intervention of helium conditioning results in cardioprotection in SHR, whereas a single intervention does not. In WKY rats, the triple intervention does not further augment protection. Helium conditioning is not associated with a mechanism involving GSK-3? and PKC-?.

Oei GT; Huhn R; Heinen A; Hollmann MW; Schlack WS; Preckel B; Weber NC

2012-06-01

305

Post-giant evolution of helium stars  

International Nuclear Information System (INIS)

[en] Extremely hydrogen deficient stars (helium stars and R Coronae Borealis variables) are considered to be remnants of double shell source stars (of the asymptotic giant branch). The evolution of stars with a condensed C/O-core and a helium envelope is followed numerically from the red giant stage to the white dwarf domain, crossing the regions of R CrB- and helium stars (so far analyzed). They have typically masses M/M(sun) = 0.7 and luminosities log L/L(sun) = 4.1. The time for crossing the helium star domain is some 103 years. The corresponding times in the R CrB-region amounts up to several 104 years. The lower limit of the death rate of helium stars is estimated to be 4 x 10-14pc-3yr-1. This value is only a factor of ten lower than the birth rate of all non-DA white dwarfs. It is therefore possible that the helium stars are the precursors of helium rich white dwarfs. As a consequence, a significant fraction of all stars which end their lives as white dwarfs should pass through the helium star phase. (orig.)[de] Sterne mit extremer Wasserstoffdefizienz (Heliumsterne und R Coronae Borealis Variablen) werden als Ueberreste von Quellensternen mit Doppelhuelle (des asymptotischen Riesenzweigs) betrachtet. Die Entwicklung von Sternen mit kondensiertem C/O-Kern und Heliumhuelle vom Roten Riesen zum Weissen Zwerg wird numerisch verfolgt bei der Ueberschreitung der Bereiche von R CrB- und Heliumsternen (soweit bisher analysiert). Sie haben im typischen Fall eine Masse M/M(Sonne) = 0,7 und eine Leuchtkraft log L/L(Sonne) = 4,1. Die Zeit fuer den Durchgang durch die Heliumstern-Domaene betraegt etwa 103 Jahre, die entsprechende Zeit im R CrB-Bereich einige 104 Jahre. Die untere Grenze der Absterbegeschwindigkeit von Heliumsternen wird auf 4 x 10-14pc-3yr-1 geschaetzt. Dieser Wert liegt nur um einen Faktor 10 niedriger als die Geburtsrate aller nicht-DA Weissen Zwerge. Es ist daher moeglich, dass die Heliumsterne die Vorlaeufer von heliumreichen Weissen Zwergen sind. Das wuerde bedeuten, dass ein signifikanter Anteil aller Sterne, die als Weisse Zwerge enden, durch die Heliumsternphase hindurchgehen. (orig.)

1977-01-01

306

Polarizability of Helium and Gas Metrology  

International Nuclear Information System (INIS)

Using a quasispherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A? in the limit of zero density. We obtained (A?,meas-A?,theory)/A?=(-1.8±9.1)x10-6, where the standard uncertainty (9.1 ppm) is a factor of 3.3 smaller than that of the best previous measurement. If the theoretical value of A? is accepted, these data determine a value for the Boltzmann constant that is only 1.8±9.1 ppm larger than the accepted value. Our techniques will enable a helium-based pressure standard and measurements of thermodynamic temperatures.

2007-06-22

307

Helium burning in moderate-mass stars  

CERN Multimedia

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

Weiss, Achim

2011-01-01

308

Mechanisms of Alloy 800 corrosion in helium  

International Nuclear Information System (INIS)

Cr2O3 scales are found to form on Alloy 800 and a similar pure ternary alloy in air, and 1 and 50 atm. helium containing oxidizing impurities typical of those in an SGHTR. The strong temperature dependence and neglibible helium overpressure dependence indicate that gas transport through the scales is not rate controlling. Surface oxidation rates are therefore controlled by solid state diffusion and the low oxygen partial pressure dependence of the oxidation rate in Alloy 800 is ascribed to the presence of extrinsic defects in the Cr3O3 (due to doping by alloying elements) or to the presence of short circuit diffusion paths. (Auth.)

1978-03-16

309

Plastic dewar for pressurized superfluid helium  

Energy Technology Data Exchange (ETDEWEB)

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

Kobayashi, H.; Fukuda, H.; Tomioka, T.; Kuraoka, Y.

1987-06-01

310

Plastic dewar for pressurized superfluid helium  

International Nuclear Information System (INIS)

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

1987-01-01

311

Detection of solar neutrinos in superfluid helium  

International Nuclear Information System (INIS)

A new method for detecting solar neutrinos and other weakly interacting particles is proposed and described. The detector consists of a large mass of superfluid helium at low temperatures (20 mK). When a neutrino is scattered off an electron, the recoil energy of the electron (10-6 to 10-7 ergs) is deposited in the helium. This small amount of energy can be detected because of the unusual kinetics of rotons at low temperatures. It should be possible to construct a detector of sufficiently low background and large size to measure solar neutrino spectra. 29 refs., 2 figs.

1987-01-24

312

Helium isotopic evidence for recent subcrustal volcanism in eastern Australia  

Energy Technology Data Exchange (ETDEWEB)

A component with approx.6% mantle helium (/sup 3/He//sup 4/He = 5--9 x 10/sup -7/) has been identified in borewaters from the Great Artesian Basin, Australia that is isotopically distinct from previously identified in situ production (/sup 3/He//sup 4/He = 1.6 x 10/sup -8/) and a crustal degassing flux (/sup 3/He//sup 4/He = 6.75 x 10/sup -8/). The occurrence of this component is limited to three identified localities (approx.20.5 /sup 0/S 144 /sup 0/E; approx.25.5 /sup 0/S 146 /sup 0/E; approx.27 /sup 0/S 144.5 /sup 0/E) all within the region of high reduced heat flow in eastern Australia. No evidence for a mantle component was apparent in central Australia. This component is most probably the result of continued intrusive volcanism (<1 m.y.) associated with the Cainozoic lava flow fields in the region. Although the volcanic activity has no present-day surface manifestation, its mantle helium was probably carried to the near-surface by large-scale fluid transport processes in the crust. copyright American Geophysical Union 1987

Torgersen, T.; Clarke, W.B.; Habermehl, M.A.

1987-12-01

313

The hall Effect in 2D Electrons on Liquid Helium  

International Nuclear Information System (INIS)

The a.c. Hall effect has been measured directly in a 2D sheet of free electrons above the surface of liquid helium at frequencies from 1.5. to 35 kHz in a magnetic field B up to 4 T. For small B the normal Hall effect is observed but at higher fields finite frequency effects occur as the 2D skin depth becomes less than the sample size. Calculations using the magnetoconductivity tensor for a 2D transmission line agree well with experiment, except in the high-field limit as quantum effects become significant

1988-01-01

314

Hall Effect in 2D Electrons on Liquid Helium  

Energy Technology Data Exchange (ETDEWEB)

The a.c. Hall effect has been measured directly in a 2D sheet of free electrons above the surface of liquid helium at frequencies from 1.5. to 35 kHz in a magnetic field B up to 4 T. For small B the normal Hall effect is observed but at higher fields finite frequency effects occur as the 2D skin depth becomes less than the sample size. Calculations using the magnetoconductivity tensor for a 2D transmission line agree well with experiment, except in the high-field limit as quantum effects become significant.

Lea, M.J.; Stone, A.O.; Fozooni, P.

1988-12-01

315

Microwave saturation of the Rydberg States of electrons on helium.  

UK PubMed Central (United Kingdom)

We present measurements of the resonant microwave excitation of Rydberg energy levels for surface-state electrons on superfluid helium. The temperature-dependent contribution to the linewidth gamma(T) agrees with theoretical predictions and is very small below 700 mK, in the ripplon scattering regime. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency Omega was determined as a function of microwave power. High values of the ratio Omega/gamma confirm this system as an excellent candidate for creating qubits.

Collin E; Bailey W; Fozooni P; Frayne PG; Glasson P; Harrabi K; Lea MJ; Papageorgiou G

2002-12-01

316

Target wavefunctions in electron scattering from helium-like ions  

Energy Technology Data Exchange (ETDEWEB)

Target wavefunctions in calculations of ionization cross sections of helium-like ions by electron impact are obtained by using the variational method. Wavefunctions for twenty-five states in N{sup 5+}, O{sup 6+} and Ne{sup 8+} are represented with configuration interactions. Twelve orthogonal orbitals are used in the calculation, five spectroscopic (1s, 2s, 2p, 3s, 3p, 3d) and seven pseudo-orbitals, the later being included to allow for additional correlations. Present values for excitation energies are in good agreement with experimental results. (author)

Miyazaki, Munetoshi; Nakazaki, Shinobu [Miyazaki Univ., Miyazaki (Japan); Mateo, Z.F. [Central Luzon State Univ., Munoz, Nueva Ecija (Philippines)

2001-09-01

317

Ceramic BOT type blanket with poloidal helium cooling  

International Nuclear Information System (INIS)

This paper briefly describes the work done and results achieved over the past two years on the ceramic breeder BOT blanket with poloidal helium cooling. A conclusive remark on the brick/plate option described previously is followed by short descriptions of the low and high performance pebble bed options elaborated as alternatives for both NET and DEMO. The results show, togethre with those about the poloidal cooling of the First Wall, good prospects for this blanket type provided that the questions connected wiht an extensive use of beryllium find a satisfactor answer. (author). 5 refs.; 7 figs.; 1 tab.

1989-01-01

318

''Il Mantello'' - A helium cooled solid breeder blanket for NET  

International Nuclear Information System (INIS)

''Il Mantello'' is an engineering design study of a helium cooled blanket using solid, ceramic breeder materials, and solid, metallic neutron multipliers. This study was initiated in October 1983 and has now entered phase II. Results of the phase I work can be found in the Proc. of 13th Soft (Varese, 1984). This paper is concerned with phase II results. The design application for the blanket is the Next European Torus. However, the utility of the blanket design must extrapolate to a full-size power producing reactor. (author). 5 figs, 2 tabs.

1986-06-06

319

Accuracy of helium accumulation fluence monitor for fast reactor dosimetry  

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-03-01

320

Microwave saturation of the Rydberg states of electrons on helium  

CERN Multimedia

We present measurements of the resonant microwave excitation of the Rydberg energy levels of surface state electrons on superfluid helium. The temperature dependent linewidth agrees well with theoretical predictions and is very small below 300 mK. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency was determined as a function of microwave power. The high values of the ratio of the Rabi frequency to linewidth confirm this system as an excellent candidate for creating qubits.

Collin, E; Fozooni, P; Frayne, P G; Glasson, P H; Harrabi, K; Lea, M J; Papageorgiou, G

2002-01-01

 
 
 
 
321

Penning collisions of laser-cooled metastable helium atoms  

CERN Multimedia

We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient $\\beta$ on the excited state ($2^3P_2$) and metastable state ($2^3S_1$) populations is also investigated. From these results we infer a rather uniform rate constant $K_{sp}=(1{\\pm}0.4)\\times10^{-7}$ cm$^3$/s.

Dos Santos, F P; Léonard, J; Sinatra, A; Wang, J; Pavone, F S; Rasel, E; Unnikrishnan, C S; Leduc, M; Wang, Junmin

2001-01-01

322

Penning collisions of laser-cooled metastable helium atoms  

International Nuclear Information System (INIS)

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

2001-01-01

323

Accuracy of helium accumulation fluence monitor for fast reactor dosimetry  

International Nuclear Information System (INIS)

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

1998-01-01

324

Research and development of a helium-4 based solar neutrino detector. Progress report, 1 January 1991--30 June 1992  

Energy Technology Data Exchange (ETDEWEB)

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

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

1992-06-30

325

Energy harvesting in doped helium nano-droplets  

International Nuclear Information System (INIS)

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

2012-11-05

326

Uncertainty and the joint extraction of helium and natural gas  

Energy Technology Data Exchange (ETDEWEB)

In this paper a model of joint natural resources is developed in order to examine particular aspects of the helium industry. The importance of helium demand for the equilibria in the markets for natural gas and helium, the joint resources, is analyzed. This analysis is pursued under both conditions of certainty and helium demand uncertainty. A modified Hotelling rule is derived under conditions of uncertainty in the timing of demand for the residual resource. 11 refs., 4 figs.

Hughey, A.M. (Brooklyn College, New York (USA))

1989-03-01

327

Theory of quantum nucleation of bubbles in liquid helium  

Energy Technology Data Exchange (ETDEWEB)

The author calculates the rate at which bubbles form by quantum tunneling in liquid helium-3 and helium-4 at negative pressure. The author finds that quantum tunneling should be observable at temperatures below about 0.1 K in helium-3 and 0.2 K in helium-4, and at pressures close to the critical negative pressure at which the liquid becomes unstable against long wavelength density fluctuations.

Maris, H.J. [Brown Univ., Providence, RI (United States)

1995-03-01

328

Analysis of irradiated boron alloy pellets for entrapped helium  

International Nuclear Information System (INIS)

Helium gas trapped in the irradiated titanium boron samples was determined over a temperature range 1073-1923 K. It was observed that helium releases only above 1823 K and that helium content is more at peripheries compared to centre part of the pellets. (author)

2011-01-01

329

The weakest bond: Experimental observation of helium dimer  

International Nuclear Information System (INIS)

Helium dimer ion was observed after electron impact ionization of a supersonic expansion of helium with translational temperature near 1 mK. The dependence of the ion signal on source pressure, distance from the source, and electron kinetic energy was measured. The signal was determined to arise from ionization of neutral helium dimer.

1993-01-01

330

Existence of an Ericson regime in stretched helium  

Science.gov (United States)

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

Blümel, R.

1996-12-01

331

Existence of an Ericson regime in stretched helium  

International Nuclear Information System (INIS)

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

1996-01-01

332

Existence of an Ericson regime in stretched helium  

Energy Technology Data Exchange (ETDEWEB)

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

Bluemel, R. [Fakultaet fuer Physik, Albert-Ludwigs-Universitaet, D-79104 Freiburg (Germany)

1996-12-01

333

The role of dislocations in supersolid Helium-4  

Science.gov (United States)

Disorder and crystallographic defects play a major role in the supersolid phase of ^4He. Monte Carlo simulations addressed the physics of vacancies [1], grain boundaries [2] and dislocations [3], which are the focus of this talk. We find that certain types of edge and screw dislocations are superfluid while other remain insulating, depending on their orientation, Burgers vector and possible splitting of the core. The mechanism for superfluidity is provided by the strain near the core of the defect exceeding a threshold value [4]. Superfluid dislocations can build a network of phase coherent tubes (the so-called Shevchenko state) [3], which might lead to an observable mass decoupling in experiment. I will also look at the interactions between a Helium-3 impurity atom and a screw dislocation [5] and make contact with recent experiments. [4pt] [1] M. Boninsegni, A. Kuklov, L. Pollet, N. Prokof'ev, B. Svistunov and M. Troyer, The fate of vacancy-induced supersolidity in ^4He, Phys. Rev. Lett. 97, 080401 (2006).[0pt] [2] L. Pollet, M. Boninsegni, A. B. Kuklov, N. V. Prokof'ev, B. V. Svistunov, and M. Troyer, Superfluidity of Grain Boundaries in solid ^4He, Phys. Rev. Lett. 98, 135301 (2007).[0pt] [3] M. Boninsegni, A. B. Kuklov, L. Pollet, N. V. Prokof'ev, B. V. Svistunov, and M. Troyer, Luttinger Liquid in the Core of Screw Dislocation in Helium-4, Phys. Rev. Lett. 99, 035301 (2007).[0pt] [4] L. Pollet, M. Boninsegni, A. B. Kuklov, N. V. Prokofev, B. V. Svistunov, and M. Troyer, Local stress and superfluid properties of solid Helium-4, Phys. Rev. Lett. 101, 097202 (2008).[0pt] [5] P. Corboz, L. Pollet, N. V. Prokof'ev, and M. Troyer, Binding of a ^3He impurity to a screw dislocation in solid ^4He, Phys. Rev. Lett. 101, 155302 (2008).

Pollet, Lode

2009-03-01

334

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

International Nuclear Information System (INIS)

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

1989-01-01

335

Boron diffusion in presence of defects induced by helium implantation  

International Nuclear Information System (INIS)

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

2005-12-05

336

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

CERN Multimedia

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

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

2013-01-01

337

Ionization of hydrogen and helium atoms by static and microwave electric fields  

Energy Technology Data Exchange (ETDEWEB)

A series of experiments has investigated the interaction of strong static and microwave electric fields with highly excited hydrogen and helium atoms. To permit study of individual atomic substates, versatile techniques have been developed to Stark-shift energy levels of atoms in a fast beam into resonance with infrared laser light. The field-dependent ionization rates of hydrogen atoms prepared in selected substates of the n = 30 and n = 40 manifolds were measured over the range 10/sup 5/ - 10/sup 8/ sec/sup -1/. These results are in excellent agreement with the non-relativistic, numerical calculations of Damburg and Kolosov. The effects of wavefunction mixing on the ionization behavior of nonhydrogenic atoms near anticrossings of Stark energy levels were investigated with helium triplet Rydberg atoms. High resolution helium ionization data were successfully modeled with a density of states characterization of the Stark continuum. Measurements of the microwave (9.92 GHz) ionization of helium (1s (napprox.30)s /sup 3/S/sub 1/) atoms were explained, in part, by calculations based on a multilevel, quasistatic model. A complete, quantitative theory of this dynamic process, which would explain both the helium and hydrogen microwave ionization data, is an important goal for future work.

Mariani, D.R.

1983-01-01

338

Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel  

International Nuclear Information System (INIS)

The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwestern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites. (fusion engineering)

2009-04-01

339

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

International Nuclear Information System (INIS)

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

1993-10-14

340

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

Energy Technology Data Exchange (ETDEWEB)

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

LaVerne, J.A.; Yoshida, Hiroko (Univ. of Notre Dame, IN (United States) Oak Ridge National Lab., TN (United States))

1993-10-14

 
 
 
 
341

Superfluidity in a Doped Helium Droplet  

CERN Document Server

Path Integral Monte Carlo calculations of the superfluid density throughout ^4He droplets doped with linear impurities (HCN)_n are presented. After deriving a local estimator for the superfluid density distribution, we find a decreased superfluid response in the first solvation layer. This effective normal fluid exhibits temperature dependence similar to that of a two-dimensional helium system.

Draeger, E W

2002-01-01

342

Development of helium isotopic database in Japan  

International Nuclear Information System (INIS)

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

2012-01-01

343

HELIUM FLOW INDUCED ORBIT JITTER AT RHIC.  

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-05-16

344

Low-energy Antiproton Interaction with Helium  

CERN Document Server

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

Gibbs, W R

1997-01-01

345

Oscillator Strengths for the Helium Isoelectronic Sequence.  

Science.gov (United States)

Variational wavefunctions were computed for the 1(1)S, 2(1,3)S, 2(1,3)P, 3(1,3)P, and 3(1,3)D terms of ions in the helium isoelectronic sequence from He through Ne(+8). The trial functions are Hylleraas type expansions, explicitly involving r12, and with ...

A. W. Weiss

1966-01-01

346

Positron-impact excitation of helium  

Energy Technology Data Exchange (ETDEWEB)

The positron-impact excitation cross section for the n = 2 level of helium has been calculated in the energy range 20--200 eV. A distorted wave obtained by solving an adiabatic equation has been used in the initial channel. The results are compared with the other existing theoretical predictions and measured values.

Mandal, S.K.; Basu, M.; Ghosh, A.S.

1986-01-01

347

Messer to provide helium for LHC project  

CERN Multimedia

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.

2008-01-01

348

Messer to provide helium for LHC  

CERN Multimedia

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.

2008-01-01

349

Helium refrigerator for 'SULTAN'  

Energy Technology Data Exchange (ETDEWEB)

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

Arpagaus, M.; Erlach, H.; Quack, H. (Sulzer Bros. Ltd., Winterthur (Switzerland))

1984-01-01

350

Above-threshold ionization in helium  

Energy Technology Data Exchange (ETDEWEB)

We report the first high-resolution angle-resolved electron spectra of helium photoionized above threshold by intense, linear or circularly polarized 532-nm laser pulses. Quantitative comparisons are made to the Keldysh-Faisal-Reiss theory of photoionization in intense fields.

Bucksbaum, P.H.; Bashkansky, M.; Schumacher, D.W.

1988-05-01

351

Potential applications of high temperature helium  

Energy Technology Data Exchange (ETDEWEB)

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

Schleicher, R.W. Jr.; Kennedy, A.J.

1992-09-01

352

Potential applications of high temperature helium  

Energy Technology Data Exchange (ETDEWEB)

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

Schleicher, R.W. Jr.; Kennedy, A.J.

1992-09-01

353

Helium suspension of solids in FW cooling  

Energy Technology Data Exchange (ETDEWEB)

There are various FW design concepts with gaseous helium coolant. Calculations showed that FW cooling system with helium as coolant requires pressure level 100 atms and above, because of low helium volumetric heat capacity. Such pressures are high taking into account reactor safety concern. Thus it is desirable to use low pressure circuits in order to improve FW operating conditions and alleviate maintenance. One of the ways of coolant pressure reduction is the gaseous suspension use instead of pure helium. Heat transfer and hydrodynamics in gaseous suspensions and their application have been investigated since early 60`s (e.g. General Atomic). Relationships for heat transfer and pressure drop calculations were recommended for certain range of solid particle concentrations, sizes and channel diameters. Now the advanced relationships for calculations based on experimental data were developed in RF. These relationships were true in rather wide range of operating parameters. Calculations based on relationships mentioned above were performed for various FW ITER design options. Results were obtained for two coolant options: pure gas and gaseous suspension.

Razmerov, A.; Epinatjev, A.; Perevezencev, V. [ENTEK-RDIPE, Moscow (Russian Federation)

1994-12-31

354

Tritium and helium-3 in metals  

Energy Technology Data Exchange (ETDEWEB)

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

Lasser, R.

1989-01-01

355

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

Energy Technology Data Exchange (ETDEWEB)

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.

Claas, P.

2006-01-15

356

Accelerated mice skin acute wound healing in vivo by combined treatment of argon and helium plasma needle.  

UK PubMed Central (United Kingdom)

BACKGROUND AND AIMS: The efficacy of a direct application of plasma needle to in vivo wound healing was experimentally studied in mice. This kind of plasma has achieved considerable success in blood coagulation and tissue restoration in mice. In the development of the present study, an argon plasma needle was chosen for coagulation purposes, whereas for healing purposes, a helium plasma needle was used. METHODS: Treatment was applied with a plasma needle produced by argon and helium to a wound induced in laboratory mice. Tissue regeneration was carried out by three argon plasma treatments with 0.5 SLPM flow for 1 min and three treatments of helium with 1.5 SLPM flow. Intervals between each treatment were 5 min and 60 min for argon and helium plasmas, respectively, thus completing a total treatment time of 180 min. Histological sections were performed to corroborate the internal bleeding and tissue regeneration. RESULTS: After three treatments with argon plasma, the blood produced in the wound was coagulated and protein material appeared. By means of treatment with helium plasma, an approach of the wound edges was produced until the conclusion thereof. These results were corroborated histologically. CONCLUSIONS: This type of acceleration during the skin wound healing process can be attributed to the formation of reactive species such as NO, which were increased in the helium plasma needle with respect to the argon plasma needle.

García-Alcantara E; López-Callejas R; Morales-Ramírez PR; Peña-Eguiluz R; Fajardo-Muñoz R; Mercado-Cabrera A; Barocio SR; Valencia-Alvarado R; Rodríguez-Méndez BG; Muñoz-Castro AE; de la Piedad-Beneitez A; Rojas-Olmedo IA

2013-04-01

357

Determination of helium in beryl minerals  

International Nuclear Information System (INIS)

[en] In order to obtain the diffusion coefficients of helium in beryl and phenacite samples at various temperatures, helium leak rates were measured in these minerals at these temperatures. Mass spectrometry (MS) was used to obtain helium leak rates and the gas flow was plotted against time. The gas quantity determined by MS was first obtained at various temperatures until no helium leak rate was detected. After that, these samples were irradiated with fast neutrons to produce helium which was measured again. This procedure was used to estimate the experimental error. The quantity of helium produced by interaction of gamma radiation with beryl minerals was theoretically calculated from the amount of thorium-232 at the neighbourhood of the samples. The quantity of helium produced in the minerals due to uranium and thorium decay was calculated using the amount of these heavy elements, and the results were compared with the amounts determined by MS. The amount of potassium-40 was determined in order to derive the quantity of argonium-40, since some workers found argonium in excess in these minerals. The quantity of helium in the beryl samples (s) was determined in the center and in the surface of the samples in order to obtain informations about the effectiveness of the Be(?, ?) He reaction. Beryl and phenacite minerals were choosen in this research since they are opposite each other with respect to the helium contents. Both have beryllium in their compositon but beryl hold a large amount of helium while phenacite, in spite of having about three times more beryllium than beryl, do not hold the gas. (author)[pt] Estudam-se medidas de taxas de fuga de helio em amostras de fenacita e berilo, para a obtencao dos coeficientes de difusao de helio nos respectivos minerais a varias temperaturas. As medidas foram realizadas por espectrometria de massa e registradas em grafico de fluxo de gas ''versus'' tempo. A quantidade de gas determinada por espectrometria de massa foi comparada com a quantidade produzida por irradiacao de amostras isentas de helio. Primeiro, foram obtidas as quantidades de gas das amostras a varias temperaturas ate que todo o helio escapasse das amostras. Depois, estas foram irradiadas com neutrons rapidos, e o gas formado foi, novamente, medido com o espectrometro. Este procedimento foi utilizado para se obter uma estimativa do erro experimental. A quantidade de gas produzida por interacao de radiacao gama com minerais contendo berilio foi calculada teoricamente, a partir do teor de Th232 contido na vizinhanca da amostra. Determinam-se os teores de chumbo, uranio, torio e potassio. A quantidade de helio produzida nos minerais, devido ao decaimento do uranio e torio contidos, foi calculada com base nos teores desses elementos, e o resultado foi comparado com a quantidade determinada por espectrometria de massa. O teor de potassio-40 foi determinado, para o calculo da quantidade de argonio-40, gas que, segundo alguns pesquisadores, tambem existe em excesso nos minerais em estudo. Determinam-se no berilo, as quantidades de helio no centro e na superficia das amostras, para obtencao de informacoes sobre a efetividade da reacao Be (?, ?) He. Os minerais fenacita e berilo foram selecionados para o respectivo trabalho justamente por causa da situacao antagonica em que se encontram com relacao a teores de helio, isto e, ambos possuem berilio em sua composicao (estrutura), porem, enquanto o berilo apresenta grande excesso de helio, a fenacita, que possui cerca de tres vezes mais berilio, nao contem o gas ou dele apresenta teores extremamente baixos. (autor)

1985-01-01

358

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

CERN Document Server

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

Hayano, R S

2010-01-01

359

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

International Nuclear Information System (INIS)

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

1986-01-01

360

Re-Condensation and Liquefaction of Helium and Hydrogen Using Coolers  

International Nuclear Information System (INIS)

Coolers are used to cool cryogen free devices at temperatures from 5 to 30 K. Cryogen free cooling involves a temperature drop within the device being cooled and between the device and the cooler cold heads. Liquid cooling with a liquid cryogen distributed over the surface of a device combined with re-condensation can result in a much lower temperature drop between the cooler and the device being cooled. The next logical step beyond simple re-condensation is using a cooler to liquefy the liquid cryogen in the device. A number of tests of helium liquefaction and re-condensation of helium have been run using a pulse tube cooler in the drop-in mode. This report discusses the parameter space over which re-condensation and liquefaction for helium and hydrogen can occur.

2009-07-02

 
 
 
 
361

Influence of the methods of helium implantation on the blistering of stainless steel  

International Nuclear Information System (INIS)

[en] Implantation of helium is investigated in samples of the stainless steel 0Kh16N15M3B under conditions simulating the profile of the implantation in a thermonuclear reactor. The samples were bombarded with 1-MeV He/sup +/ ions at a current density of 5.10/sup 13/ ions/cm/sup 2/*sec. The results obtained give evidence that the broadened profiles of the implantation of helium may essentially influence the erosion of materials, as was noted earlier by the example of the implantation of helium in niobium. This circumstance must be taken into account in predicting the effects of implanted materials on the first wall of a thermonuclear reactor. 3 refs

1980-01-01

362

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

International Nuclear Information System (INIS)

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

1994-01-01

363

An automatic apparatus for the concentration of the neon-helium mixture  

International Nuclear Information System (INIS)

[en] The paper describes an apparatus providing enriched to 65-70 % neon-helium mixture from the ZhA-300 air separation facility. To ensure the normal operation of the facility it is necessary to evacuate the liquid nitrogen condensing during neon-helium mixture enrichment. A device has been developed that allows the liquid nitrogen level in the collection cavity of the dephlegmator, required for the normal operation of the apparatus, to be maintained automatically. The supply of liquid nitrogen to the vessel with the dephlegmator is also automatic. The apparatus provides the neon-helium mixture with a concentration of 65-70 % at a rate of 20 l/h, 5 l/h of liquid is nitrogen being used. The separation coefficient obtained is 0.85

1974-01-01

364

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

Energy Technology Data Exchange (ETDEWEB)

Positron lifetime spectra have been measured as a function of temperature in the range 10-295 K for aluminum single crystals irradiated with 0-40 MeV {alpha} particles to a total dose of {approx equal} 5x10{sup 17} cm{sup -2}. We present results for the temperature dependence of the lifetime component representing annihilations of the positrons trapped in helium-filled cavities. We discuss these results in terms of positron diffusion and helium physisorption on the internal surfaces of the irradiation-induced cavities. (orig.).

Hozhabri, N.; Ma, J.; Naidu, S.V.; Eom, C.I.; Sharma, S.C. (Dept. of Physics, Univ. of Texas at Arlington (USA)); Nambissan, P.M.G.; Sen, P. (Saha Inst. of Nuclear Physics, Calcutta (India))

1991-05-01

365

An efficient cooling loop for connecting cryocooler to a helium reservoir  

Energy Technology Data Exchange (ETDEWEB)

The magnet system of the VENUS ECR Ion Source at LBNL has two 1.5-watt cryocoolers suspended in the cryostat vacuum. Helium vapor from the liquid reservoir is admitted to a finned condenser bolted to the cryocooler 2nd stage and returns as liquid via gravity. Small-diameter flexible tubes allow the cryocoolers to be located remotely from the reservoir. With 3.1 watts load, the helium reservoir is maintained at 4.35 K, 0.05K above the cryocooler temperature. Design, analysis, and performance are presented.

Taylor, C.E.; Abbott, C.S.R.; Leitner, D.; Leitner, M.; Lyneis, C.M.

2003-09-21

366

The proton and helium rigidity spectra from 10 to 50 GV  

International Nuclear Information System (INIS)

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

1977-08-26

367

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

International Nuclear Information System (INIS)

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

1986-01-01

368

Measurements of cascade times of antiprotons in molecular hydrogen and helium  

CERN Multimedia

The OBELIX experiment at CERN collected samples of antiproton annihilations at rest in different gaseous targets, such as hydrogen, deuterium and helium. We analyze a set of the Obelix data using a new technique for measuring, for the first time, the cascade times independent of the capture energy and of the antiproton stopping power. We report on measurements of the cascade times for hydrogen at 3.4, 5.8, 9.8 and 150 mbar and for helium at 8.2, 50 and 150 mbar pressure. An estimate of the antiproton capture energy in hydrogen is also presented. (12 refs).

Bianconi, A; Corradini, M; Donzella, A; Gómez, G; Lodi-Rizzini, E; Venturelli, L; Vilar, R; Zenoni, A; Bertin, A; Bruschi, M; Capponi, M; De Castro, S; Donà, R; Galli, D; Giacobbe, B; Marconi, U; Massa, I; Piccinini, M; Semprini-Cesari, N; Spighi, R; Vagnoni, V M; Vecchi, S; Villa, M; Vitale, A; Zoccoli, A; Cicalò, C; De Falco, A; Masoni, A; Puddu, G; Serci, S; Usai, G L; Gorchakov, O E; Prakhov, S N; Rozhdestvensky, A M; Tretyak, V I; Poli, M; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Petrascu, C; Ableev, V G; Ricci, R A; Vannucci, Luigi; Filippini, V; Fontana, A; Montagna, P; Rotondi, A; Salvini, P; Mirfakhraee, N; Bussa, M P; Busso, L; Cerello, P G; Denisov, O Yu; Ferrero, L; Garfagnini, R; Grasso, A; Maggiora, A; Panzarasa, A; Panzieri, D; Tosello, F; Botta, E; Bressani, Tullio; Calvo, D; Costa, S; D'Isep, F; Feliciello, A; Filippi, A; Marcello, S; Agnello, M; Iazzi, F; Minetti, B; Tessaro, S; Santi, L

2000-01-01

369

An efficient cooling loop for connecting cryocooler to a helium reservoir  

International Nuclear Information System (INIS)

[en] The magnet system of the VENUS ECR Ion Source at LBNL has two 1.5-watt cryocoolers suspended in the cryostat vacuum. Helium vapor from the liquid reservoir is admitted to a finned condenser bolted to the cryocooler 2nd stage and returns as liquid via gravity. Small-diameter flexible tubes allow the cryocoolers to be located remotely from the reservoir. With 3.1 watts load, the helium reservoir is maintained at 4.35 K, 0.05K above the cryocooler temperature. Design, analysis, and performance are presented

2003-01-01

370

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

International Nuclear Information System (INIS)

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

1982-01-01

371

The future of helium as a natural resource  

CERN Document Server

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

Glowacki, Bartek A; Nuttall, William J

2012-01-01

372

Survey of helium in soil gases of Long Valley, Califorina  

Energy Technology Data Exchange (ETDEWEB)

Soil and water samples in and around the Long Valley geothermal area, Mono County, California, were collected and analyzed for helium by means of a modified mass spectrometer leak detector to see what relationship helium concentrations might have to geothermal features of the area, and to previously studied mercury anomalies in the area. Anomalously high concentrations of helium occurred over part of a major Sierra Nevada frontal fault and over other faults outside of the caldera. Anomalously low concentrations of helium occurred in several areas of high mercury concentrations, which were also areas of hydrothermal alteration. Quantities of helium exsolved from water samples did not fit any pattern.

Hinkle, M.E.; Kilburn, J.E.

1980-01-01

373

Method to control the amount of helium during leak testing  

International Nuclear Information System (INIS)

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

2002-01-01

374

Method to control the amount of helium during leak testing  

Energy Technology Data Exchange (ETDEWEB)

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

Frank E. Jurvic, Jr.

2002-03-29

375

Doubly excited helium. From strong correlation to chaos  

Energy Technology Data Exchange (ETDEWEB)

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

Jiang, Yuhai

2006-03-15

376

Helium measurements of pore-fluids obtained from SAFOD drillcore  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-04-15

377

Femtosecond laser micro-structuring of aluminium under helium  

Energy Technology Data Exchange (ETDEWEB)

The interaction of 180 fs, 775 nm laser pulses with aluminium under a flowing stream of helium at ambient pressure have been used to study the material re-deposition, ablation rate and residual surface roughness. Threshold fluence F{sub th}{approx}0.4 J cm{sup -2} and the volume ablation rate was measured to be 30helium avoids gas breakdown above the substrate and leads to improved surface micro-structure by minimising surface oxidation and debris re-deposition. At 1 kHz rep. rate, with fluence F>7 J cm{sup -2} and >85 W cm{sup -2} average power density, residual thermal effects result in melt and debris formation producing poor surface micro-structure. On the contrary, surface micro-machining at low fluence F{approx}1.4 J cm{sup -2} with low power density, {approx}3 W cm{sup -2} produces much superior surface micro-structuring with minimum melt and measured surface roughness R{sub a}{approx}1.1{+-}0.1 {mu}m at a depth D{approx}50 {mu}m. By varying the combination of fluence/scan speed during ultra-fast ablation of aluminium at 1 kHz rep. rate, results suggest that maintaining average scanned power density to <5 W cm{sup -2} combined with single pulse fluence <4 J cm{sup -2} produces near optimum micro-structuring. The debris under these conditions contains pure aluminium nanoparticles carried with the helium stream.

Perrie, W.; Gill, M.; Robinson, G.; Fox, P.; O' Neill, W

2004-05-31

378

The effect of helium from tritium decay on the gas-solid equilibrium constant for La-Ni-Al tritides  

Energy Technology Data Exchange (ETDEWEB)

Change in the equilibrium vapor pressure over LaNi/sub 4.25/ Al/sub 0.75/ tritide with helium in-growth has been observed for helium concentrations up to 10,000 appm. The change is a decrease in pressure from about 500 torr to 90 torr at 80/degree/C. This decrease is believed to be associated with a crystal lattice expansion due to helium, and is similar to the plateau pressure decrease as function of aluminum concentration for the family of LaNi/sub 5-x/Al/sub x/ alloys with O < x < 1. Subsequent tritium cycling recovers the plateau pressure. These data suggest that helium has very short range diffusion for the time of these observations. 18 refs., 4 figs., 2 tabs.

Walters, R.T.

1988-01-01

379

The liquid helium thermosyphon for the GEM Detector Magnet  

International Nuclear Information System (INIS)

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

1994-01-01

380

The liquid helium thermosyphon for the GEM detector magnet  

Energy Technology Data Exchange (ETDEWEB)

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

Warren, R.P.

1993-05-04

 
 
 
 
381

Helium retention and diffusivity in flowing liquid lithium  

International Nuclear Information System (INIS)

The flowing liquid surface retention experiment (FLIRE) has been designed to provide fundamental data on the retention and pumping of He, H and other species in flowing liquid surfaces. The FLIRE facility currently uses an ion beam source, which injects ions into a flowing stream of liquid lithium. Its design allows the liquid lithium to flow between two vacuum chambers that become isolated from each other when the lithium flows. Flow velocities between 0.5 and 3.0 m/s down two ramps inside the upper vacuum chamber can be achieved. The ramps and lines where the liquid lithium flows are heated to temperatures ranging from 250 to 500 deg. C to prevent any possible freezing. A dual residual gas analyzer system monitors the partial pressure of the implanted species in both vacuum chambers. The release rate of gas atoms in the second chamber is directly related to the mechanisms of transport within the metal bulk and also the process of desorption from the surface. For the case of helium, the diffusion coefficient was calculated to be 4.5x10-3 cm2/s at 250 deg. C, with an uncertainty of ±2x10-3 cm2/s. Helium retention coefficients on the order of 10-4 were obtained based on the experimental data.

2003-01-01

382

Reliability study of sheathed thermocouples in helium environment  

Energy Technology Data Exchange (ETDEWEB)

This paper describes reliability of sheathed thermocouples in helium environment in the temperature range of 1000 - 1200/sup 0/C in contact with graphite. Thermocouple wires of K, R and WRe 5 - 26%, and sheath materials of Inconel 600, Hastelloy X, PR 10% alloy and tantalum were tested at 1000 and 1200/sup 0/C for 1000 hours. Al/sub 2/O/sub 3/ and ZrO/sub 2/ coating with plasma spray method on sheath materials improved compatibility with graphite at 1200/sup 0/C. Vaporization of alloy elements of Inconel 600 sheath caused deterioration of K and R thermocouple wires at 1200/sup 0/C. R wires reacted with MgO insulator at 1200/sup 0/C, and this reaction was enhanced in tantalum sheath. Stability of electric potential of thermocouples was acceptable for K-Inconel 600 sheath at 1000/sup 0/C, and R-PR 10% sheath and WRe 5 - 26%-tantalum sheath at 1200/sup 0/C. Finally, reaction of sheath materials with CO (500 ppm in helium) was investigated at 1200/sup 0/C. Tantalum was severely reacted after 100 hours, whereas PR 10% sheath was sound even after 500 hours.

Kawakami, H.; Matsumoto, N.; Nakanishi, T. (Fuji Electric Co. Research and Development Ltd., Yokosuka, Kanagawa (Japan))

1982-05-01

383

Flow characteristics and redesign of highly loaded helium compressors  

International Nuclear Information System (INIS)

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

2009-01-01

384

Superfluid Helium from the Macroscopic to the Microscopic  

Energy Technology Data Exchange (ETDEWEB)

Superfluid helium, first discovered in the 1930s, continues to provide scientists with a fascinating physical system rich with phenomena that challenge experimental and theoretical investigators. Moreover, much of the recent interest in superfluid helium has emanated from the wide range of technical applications for the fluid. The combination of anomalous heat transport, low viscosity and low temperature makes superfluid helium an ideal medium for cooling technologies that range from particle accelerators such as the LHC to space infrared telescopes like the recently launched SIRTF. In turn, these applications have inspired new basic investigations of the fluid dynamic behavior of superfluid helium. The presentation will review some of the macroscopic applications for superfluid helium and the relevant superfluid phenomena that support these applications. With the audience sufficiently motivated, we will turn to recent research on the transport properties of superfluid helium culminating in microscale investigations that may provide new insight into the basic physics of superfluid helium.

Van Sciver, Steven W. (Florida State University

2004-02-11

385

Helium isotope effect in solution in water and seawater.  

UK PubMed Central (United Kingdom)

The isotope effect in the solution of helium in water from 0 degrees to 40 degrees C has been determined by microgasometric measurements of the solubilities of pure helium-3 and helium4. At 0 degrees C helium-3 is less soluble than helium-4 in both distilled water and sea-water by 1.2 percent. The observed fractionation factor is 0.988+/-0.002 at 0 degrees C and appears to decrease with increasing temperature at the rate of 0.0001 per degree Centigrade, although the existence of this trend is of limited statistical certainty. The measured isotope effect is in agreement with the ratio of helium-3 to helium-4 in surface ocean water reported by Clarke, Beg, and Craig.

Weiss RF

1970-04-01

386

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-03-01

387

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

International Nuclear Information System (INIS)

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

1998-01-01

388

Influence of oxygen and moisture content on electron life time in helium-isobutane gas mixtures  

Energy Technology Data Exchange (ETDEWEB)

The presented results refer to 90% helium and 10% isobutane gas mixture. Single electrons have been used to measure the attachment coefficient and drift velocity in homogeneous electric fields in the range from 100 to 1000 Vcm{sup -1}. Water vapor and oxygen concentrations varied from 350 ppm up 1.1%, and from 5 to 900 ppm, respectively.

Golovatyuk, V. E-mail: slava@le.infn.it; Grancagnolo, F.; Perrino, R

2001-04-01

389

Influence of oxygen and moisture content on electron life time in helium-isobutane gas mixtures  

International Nuclear Information System (INIS)

The presented results refer to 90% helium and 10% isobutane gas mixture. Single electrons have been used to measure the attachment coefficient and drift velocity in homogeneous electric fields in the range from 100 to 1000 Vcm-1. Water vapor and oxygen concentrations varied from 350 ppm up 1.1%, and from 5 to 900 ppm, respectively.

2001-04-01

390

Spectral data for doubly excited states of helium with non-zero total angular momentum  

CERN Document Server

A spectral approach is used to evaluate energies and widths for a wide range of singlet and triplet resonance states of helium. Data for total angular momentum $L=1,...,4$ is presented for resonances up to below the 5th single ionization threshold. In addition the expectation value of $\\cos(\\theta_{12})$ is given for the calculated resonances.

Eiglsperger, Johannes; Piraux, Bernard; Madroñero, Javier

2011-01-01

391

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

Energy Technology Data Exchange (ETDEWEB)

This is to certify that Beaird Industries, Inc. has done a white metal blast per SSPC-SP5 as required per specifications on the vessel internal. Following the blast, a black light inspection was performed by Beaird Quality Control personnel to assure that all debris, grease, etc. was removed and interior was clean prior to closing vessel for helium test.

Rucinski, Russ; /Fermilab

1996-11-11

392

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

International Nuclear Information System (INIS)

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

1994-07-01

393

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

International Nuclear Information System (INIS)

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

1984-01-01

394

Helium nano-bubble evolution in aging metal tritides  

International Nuclear Information System (INIS)

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

2004-01-01

395

Helium nano-bubble evolution in aging metal tritides.  

Energy Technology Data Exchange (ETDEWEB)

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

Cowgill, Donald F.

2004-05-01

396

Thermal compression of atomic hydrogen on helium surface  

CERN Multimedia

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

J"arvinen, J; Vasilev, S

2006-01-01

397

Study of heat transfer in superconducting cable electrical insulation of accelerator magnet cooled by superfluid helium; Etude des transferts de chaleur dans les isolations electriques de cables supraconducteurs d'aimant d'accelerateur refroidi par helium superfluide  

Energy Technology Data Exchange (ETDEWEB)

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

Baudouy, B

1996-10-04

398

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

International Nuclear Information System (INIS)

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

1991-01-01

399

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-03-01

400

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-03-01

 
 
 
 
401

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

Energy Technology Data Exchange (ETDEWEB)

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

Tsuji, Hirokazu; Suzuki, Tomio; Tsukada, Takashi; Nakajima, Hajime [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1991-09-01

402

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

International Nuclear Information System (INIS)

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

2000-01-01

403

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

Energy Technology Data Exchange (ETDEWEB)

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

YOUCHISON,DENNIS L.; NORTH,MART T.

2000-11-22

404

Optical breakdown of helium in Bessel laser radiation beams  

International Nuclear Information System (INIS)

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

1998-10-31

405

A <= 6 helium clusters using soft core potentials  

CERN Multimedia

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

Gattobigio, M; Viviani, M

2011-01-01

406

Temperature Bias and the Primordial Helium Abundance Determination  

CERN Multimedia

We study the effect that the temperature structure has on the determination of the primordial helium abundance, Yp. We provide an equation linking T(OIII), the temperature derived from the [OIII] lines, and T(HeII), the temperature of the He I lines, both for HII regions with O++ only and for HII regions where a fraction of O+ is present. By means of T(HeII), which is always smaller than T(OIII), we derive the helium abundances of 5 objects with low and very low metallicity (NGC 346, NGC 2363, Haro29, SBS 0335-052, and I Zw 18); these objects were selected from the literature because they include the 3 low metallicity objects with the best line determinations and the 2 objects with the lowest metallicity. From these abundances we obtain that Yp(nHc)=0.2356+-0.0020, a value 0.0088 lower than that derived by using T(OIII). We call this determination Yp(nHc) because the collisional contribution to the Balmer line intensities has not been taken into account. All the recent Yp determinations in the literature have...

Peimbert, A; Luridiana, V; Peimbert, Antonio; Peimbert, Manuel

2001-01-01

407

Evolution of Low-Mass Helium Stars in Semidetached Binaries  

CERN Document Server

We present results of a systematic investigation of the evolution of low-mass (0.35, 0.40, and 0.65 solar mass) helium donors in semidetached binaries with accretors - white dwarfs. In the initial models of evolutionary sequences abundance of helium in the center is between $\\simeq 0.1$ and 0.98. Results of computations may be applied to the study of the origin and evolutionary state of AM CVn stars. It is shown that the minimum orbital periods of the systems only weakly depend on the total mass of the system and evolutionary state of the donor at RLOF and are equal to 9-11 min. The scatter in the mass-exchange rates at a given orbital period in the range between period minimum and about 40 min. does not exceed $\\sim 2.5$. At orbital periods exceeding about 20 min. mass-losing stars are weakly degenerate homogeneous cooling objects and abundances of He, C, N, O, Ne in the matter lost by them depend on the extent of He-depletion at RLOF. For the systems which are currently considered as the most probable model...

Yungelson, L R

2008-01-01

408

Helium atom scattering investigation of the Sb(111) surface  

Science.gov (United States)

The Sb(111) surface was studied with helium atom scattering (HAS). Elastic HAS at different energies of the incident helium beam (15.3, 21.9, 28.4 meV) was applied for structural investigations. The lattice constants derived from the positions of the observed diffraction peaks up to third order were found to be in perfect agreement with previous structure determinations of Sb(111). The observed diffraction patterns with clear peaks up to second order were used to model the electronic surface corrugation with the GR method. As an estimation for the attractive part of the interaction potential a well depth of (4.0 ± 0.5) meV was found. Best fit results were obtained with a corrugation height of 12–13% of the lattice constant, which is rather large compared to other surfaces with metallic character. Intensity measurements of the specular peak as a function of incident energy were analysed to determine the distribution of terraces on the surface. The results show a quite flat Sb(111) surface and a step height of 3.81 Å of the remaining terraces.

Mayrhofer-Reinhartshuber, M.; Tamtögl, A.; Kraus, P.; Ernst, W. E.

2013-10-01

409

Supercritical helium circulation pump for Japan Atomic Energy Research Institute  

International Nuclear Information System (INIS)

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

1990-01-01

410

Helium atom scattering investigation of the Sb(111) surface.  

Science.gov (United States)

The Sb(111) surface was studied with helium atom scattering (HAS). Elastic HAS at different energies of the incident helium beam (15.3, 21.9, 28.4 meV) was applied for structural investigations. The lattice constants derived from the positions of the observed diffraction peaks up to third order were found to be in perfect agreement with previous structure determinations of Sb(111). The observed diffraction patterns with clear peaks up to second order were used to model the electronic surface corrugation with the GR method. As an estimation for the attractive part of the interaction potential a well depth of (4.0 ± 0.5) meV was found. Best fit results were obtained with a corrugation height of 12-13% of the lattice constant, which is rather large compared to other surfaces with metallic character. Intensity measurements of the specular peak as a function of incident energy were analysed to determine the distribution of terraces on the surface. The results show a quite flat Sb(111) surface and a step height of 3.81 ? of the remaining terraces. PMID:23969322

Mayrhofer-Reinhartshuber, M; Tamtögl, A; Kraus, P; Ernst, W E

2013-08-23

411

Double photoinonization of helium at high energies  

International Nuclear Information System (INIS)

The author discusses experiments on the double photoionization of helium. Such experiments are conducted in helium because it is a open-quotes simpleclose quotes 3-body system. In addition, in such a two electron system, it is possible to observe electron-electron correlation. Photons are used for such experiments because they transfer all of there energy into the atomic system, while collisions are able to transfer only a small fraction of the energy they carry. Such experiments are generally carried out at high energy for a number of reasons. These include: the theory is more tractable in this regime; it it then possible to compare results with charged particle interactions; one can examine which terms in MBPT are important; the question of asymptotic limits can be addressed

1993-10-04

412

THERMAL OSCILLATIONS IN LIQUID HELIUM TARGETS  

International Nuclear Information System (INIS)

[en] A liquid helium target for the high-energy physics was built and installed in the proton beam line at the Alternate Gradient Synchrotron of Brookhaven National Laboratory in 2001. The target flask has a liquid volume of 8.25 liters and is made of thin Mylar film. A G-M/J-T cryocooler of five-watts at 4.2K was used to produce liquid helium and refrigerate the target. A thermosyphon circuit for the target was connected to the J-T circuit by a liquid/gas separator. Because of the large heat load to the target and its long transfer lines, thermal oscillations were observed during the system tests. To eliminate the oscillation, a series of tests and analyses were carried out. This paper describes the phenomena and provides the understanding of the thermal oscillations in the target system

2001-01-01

413

Thermal oscillations in liquid helium targets  

Science.gov (United States)

A liquid helium target for the high-energy physics was built and installed in the proton beam line at the Alternate Gradient Synchrotron of Brookhaven National Laboratory in 2001. The target flask has a liquid volume of 8.25 liters and is made of thin Mylar film. A G-M/J-T cryocooler of five-watts at 4.2 K was used to produce liquid helium and refrigerate the target. A thermosyphon circuit for the target was connected to the J-T circuit by a liquid/gas separator. Because of the large heat load to the target and its long transfer lines, thermal oscillations were observed during the system tests. To eliminate the oscillation, a series of tests and analyses were carried out. This paper describes the phenomena and provides the understanding of the thermal oscillations in the target system. .

Wang, L.; Jia, L. X.

2002-05-01

414

THERMAL OSCILLATIONS IN LIQUID HELIUM TARGETS.  

Energy Technology Data Exchange (ETDEWEB)

A liquid helium target for the high-energy physics was built and installed in the proton beam line at the Alternate Gradient Synchrotron of Brookhaven National Laboratory in 2001. The target flask has a liquid volume of 8.25 liters and is made of thin Mylar film. A G-M/J-T cryocooler of five-watts at 4.2K was used to produce liquid helium and refrigerate the target. A thermosyphon circuit for the target was connected to the J-T circuit by a liquid/gas separator. Because of the large heat load to the target and its long transfer lines, thermal oscillations were observed during the system tests. To eliminate the oscillation, a series of tests and analyses were carried out. This paper describes the phenomena and provides the understanding of the thermal oscillations in the target system.

WANG,L.; JIA,L.X.

2001-07-16

415

High-order nonlinear susceptibilities of helium  

Energy Technology Data Exchange (ETDEWEB)

With the goal of providing critically evaluated atomic data for modeling high harmonic generation processes in noble gases, we present calculations of frequency-dependent nonlinear susceptibilities of the ground state of helium, within the framework of Rayleigh-Schr{umlt o}dinger perturbation theory at lowest applicable order. The nonrelativistic, infinite-nuclear-mass, atomic Hamiltonian is decomposed in terms of Hylleraas coordinates and spherical harmonics, and the hierarchy of inhomogeneous equations of perturbation theory is solved iteratively. The mixed Hylleraas and Frankowski basis functions are employed to represent accurately the ground-state and perturbed wave functions. We believe our results for nonlinear susceptibilities of helium are the most accurate (and in many cases, the only) available to date, and they are offered as benchmark data for design of future multiphoton experiments. {copyright} {ital 1997} {ital The American Physical Society}

Liu, W. [Electron and Optical Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)]|[Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States)

1997-12-01

416

High-order nonlinear susceptibilities of helium  

International Nuclear Information System (INIS)

With the goal of providing critically evaluated atomic data for modeling high harmonic generation processes in noble gases, we present calculations of frequency-dependent nonlinear susceptibilities of the ground state of helium, within the framework of Rayleigh-Schroedinger perturbation theory at lowest applicable order. The nonrelativistic, infinite-nuclear-mass, atomic Hamiltonian is decomposed in terms of Hylleraas coordinates and spherical harmonics, and the hierarchy of inhomogeneous equations of perturbation theory is solved iteratively. The mixed Hylleraas and Frankowski basis functions are employed to represent accurately the ground-state and perturbed wave functions. We believe our results for nonlinear susceptibilities of helium are the most accurate (and in many cases, the only) available to date, and they are offered as benchmark data for design of future multiphoton experiments. copyright 1997 The American Physical Society.

1997-01-01

417

Helium-cooling in fusion power plants  

International Nuclear Information System (INIS)

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

1994-10-01

418

Physical Properties of Laminar Helium Deflagrations  

Energy Technology Data Exchange (ETDEWEB)

The physical properties of laminar deflagrations propagating through helium-rich compositions are determined for a wide range of temperatures and densities. The speeds, thermal widths, reactive widths, density contrasts, critical temperatures, and trigger masses are analyzed, along with their sensitivity to the input thermal transport coefficients, nuclear reaction rates, nuclear reaction network employed, and equation of state. A simple fitting formula of modest accuracy for the laminar flame speed is given, as well as detailed tables that list all of the physical properties. These physical properties may be incorporated into hydrodynamic programs as subgrid models for flame-tracking algorithms, and have applications toward models of X-ray bursts and the thin-shell helium flash of intermediate-mass stars. (c) (c) 2000. The American Astronomical Society.

Timmes, F. X.

2000-01-10

419

Physical Properties of Laminar Helium Deflagrations  

International Nuclear Information System (INIS)

[en] The physical properties of laminar deflagrations propagating through helium-rich compositions are determined for a wide range of temperatures and densities. The speeds, thermal widths, reactive widths, density contrasts, critical temperatures, and trigger masses are analyzed, along with their sensitivity to the input thermal transport coefficients, nuclear reaction rates, nuclear reaction network employed, and equation of state. A simple fitting formula of modest accuracy for the laminar flame speed is given, as well as detailed tables that list all of the physical properties. These physical properties may be incorporated into hydrodynamic programs as subgrid models for flame-tracking algorithms, and have applications toward models of X-ray bursts and the thin-shell helium flash of intermediate-mass stars. (c) (c) 2000. The American Astronomical Society

2000-01-10

420

Safety in handling helium and nitrogen  

International Nuclear Information System (INIS)

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

1991-01-01

 
 
 
 
421

Broad helium emission in the galactic center  

Science.gov (United States)

An infrared (K band) spectrum taken with a 3.8 arcsec-diameter aperture centered on the galactic center source IRS 16 exhibits weak CO band absorption and emission by hydrogen Brackett-gamma (Br gamma) and a singlet helium line near 4857/cm. The helium emission profile is much broader (FWHM about 1500 + or - 300 km/sec) than any feature seen previously at the galactic center. The broadening is probably due to Doppler motion of gas either flowing through an ionizing layer or orbiting about a massive object. The absence of hydrogen Br gamma emission with a similar profile suggests the galactic center H/He abundance ratio is reduced by a factor greater than about 500 from normal cosmic values.

Hall, D. N. B.; Kleinmann, S. G.; Scoville, N. Z.

1982-09-01

422

High temperature embrittlement due to helium  

International Nuclear Information System (INIS)

The results of creep and fatigue tests on reactor irradiated and ?-implanted specimens (mainly austenitic stainless steels) show the following qualitative features: Helium embrittlement sets in at temperatures T > 0.45 T/sub M/ (T/sub M/ melting temperature, in steels this corresponds to T ? 5500C) and increases with increasing T; in some cases observed at helium concentrations as low as a few appm; occurs under both static (creep) and cyclic (fatigue) loads; increases with decreasing strain rate; is characterized by an intergranular fracture mode; leads to a reduction of life time and ductility; is in general different for in-pile (in-beam) and post-irradiation tests

1987-01-01

423

Energy Deposition By Electrons In Superfluid Helium  

CERN Multimedia

Measurements have been performed on the energy deposition of single monoenergetic electrons stopped in superfluid 4He at low temperatures. The passage of the charged particle through the helium generates excited He 2 dimers. The radiative decay of these dimers results in scintillation light in the extreme ultraviolet. The charged particle also generates a distribution of quasiparticles in the liquid. A single quasiparticle can eject a single helium atom from the bulk in a process known as quantum evaporation. Both the scintillation light and the ejected atoms from quantum evaporation were measured calorimetrically using a thin- film, superconducting transition-edge sensor evaporated on a sapphire wafer. The wafer was mounted above the liquid surface. The two signal components are separated by using the differences in their times-of-flight. Both components of the signal were measured using various source positions and liquid levels with respect to the wafer. Measurements of the energy deposition of 364 keV ele...

Adams, J S

2001-01-01

424

Mass spectrometric analysis of helium in stainless steel  

International Nuclear Information System (INIS)

[en] Vacuum fusion mass-spectrometry was adopted for the analysis of helium in stainless steel. Samples were heated in a vacuum crucible, and helium in the samples was extracted and collected into a reservoir tank. The gas was then introduced through an orifice into a mass spectrometer, where the amount of helium was determined. The maspeq 070 quadrupole type mass spectrometer made by Shimazu Seisakusho, Ltd. was used. The resolving power was 150, and the mass range of the apparatus was 0-150. The determination limit of helium was about 2 x 10-3 ?g when standard helium gas was analyzed, and was about 10-2 ?g when the helium in stainless steel was analyzed. The relative standard deviation of helium intensity in repetitive measurement was about 2% in the amount of helium of 0.05 ?g. Helium was injected into stainless steel by means of alpha particle irradiation with a cyclotron. The amount of helium in stainless steel was then determined. The energy of alpha particles was 34 MeV, and the beam area was 10 mm x 10 mm. The experimental data were higher than the expected value in one case, and were lower in the other case. This difference was attributable to the fluctuation of alpha particle beam, misplacement of sample plates, and unevenness of the alpha beam. (Fukutomi, T.)

1974-01-01

425

Zeeman Relaxation in Cold Aluminum--Helium and Antimony--Helium Collisions  

Science.gov (United States)

We present the combined experimental and theoretical study of aluminum--helium and antimony--helium collisions at 800mK. Zeeman relaxation in atom--helium collisions can serve as a probe of the atom--helium interaction potentials. The relaxation mechanisms are different for the two species. In the case of aluminum, due to a spherical electron distribution, Zeeman relaxation is expected to be slow in the pure ,2 P1/2 ground state. However, during a collision the anisotropic ,2 P3/2 excited state is mixed with the ground state, causing rapid relaxation. Our results further confirm the theoretical model previously developed for indium and gallium. In the case of antimony, despite being nominally a spherical S--state (,4 S3/2), spin--orbit coupling mixes states with nonzero angular moment into the ground state, and hence introduces electronic anisotropy into its interaction with helium. This work extends our understanding of cold collisions in pnictogens.

Au, Yat Shan; Connolly, Colin; Chae, Eunmi; Tscherbul, Timur; Doyle, John

2012-06-01