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Sample records for superfluid liquid helium

  1. The influence of superfluidity on impurities condensation in liquid helium

    NASA Astrophysics Data System (ADS)

    Gordon, E. B.

    2012-11-01

    All major aspects of the influence of superfluidity in He II on the processes of condensation of impurities suspended in it have been analyzed. Particular attention is given to the recently discovered phenomenon of impurities coalescence catalysis by quantized vortices in superfluid helium. The presence of quantized vortices not only tremendously accelerates the condensation process for any substance introduced into liquid helium but also gives rise to a completely new product—long and thin nanowires. The role of local overheating, which accompanies coalescence of particles inside superfluid helium, in formation of morphology and structure of impurity-helium condensates, including molecular crystals containing stabilized active atoms, is elucidated.

  2. Liquid acquisition devices for superfluid helium transfer

    NASA Technical Reports Server (NTRS)

    Dipirro, M. J.

    1990-01-01

    To transfer superfluid helium (He II) in the milli-g or micro-g environment in orbit, it is necessary to provide a reasonably steady supply of liquid to the inlet of the pump in the supply dewar. To accomplish this without providing an artificial gravity through acceleration requires a liquid acquisition device. Fluid swirl and electrostatic devices have been proposed to orientate the fluid. However, the simplest mechanisms appear to be the use of surface tension or the thermomechanical effect. This paper examines four concepts for providing He II to the inlet of a thermomechanical pump. The devices are a distributed thermomechanical pump, a distributed pump with a main thermomechanical pump, a screened channel system and a vane/sponge combination. Calculations on the efficiency of these types of liquid acquisition devices are made using laboratory data from tests involving small scale devices where applicable. These calculations show that the latter two types of liquid acquisition devices are the most efficient. Questions as to the probability of cavitation and the effect of the residual shuttle acceleration on their operation remain to be answered, however.

  3. Liquid acquisition devices for superfluid helium transfer

    NASA Technical Reports Server (NTRS)

    Dipirro, M. J.

    1990-01-01

    To transfer superfluid helium (He II) in the milli-g or micro-g environment in orbit, it is necessary to provide a reasonably steady supply of liquid to the inlet of the pump in the supply dewar. To accomplish this without providing an artificial gravity through acceleration requires a liquid acquisition device. Fluid swirl and electrostatic devices have been proposed to orientate the fluid. However, the simplest mechanisms appear to be the use of surface tension or the thermomechanical effect. This paper examines four concepts for providing He II to the inlet of a thermomechanical pump. The devices are a distributed thermomechanical pump, a distributed pump with a main thermomechanical pump, a screened channel system and a vane/sponge combination. Calculations on the efficiency of these types of liquid acquisition devices are made using laboratory data from tests involving small scale devices where applicable. These calculations show that the latter two types of liquid acquisition devices are the most efficient. Questions as to the probability of cavitation and the effect of the residual shuttle acceleration on their operation remain to be answered, however.

  4. Design and testing of a superfluid liquid helium cooling loop

    SciTech Connect

    Gavin, L.M.; Green, M.A.; Levin, S.M.; Smoot, G.F.; Witebsky, C.

    1989-07-01

    This paper describes the design and preliminary testing of a cryogenic cooling loop that uses a thermomechanical pump to circulate superfluid liquid helium. The cooling loop test apparatus is designed to prove forced liquid helium flow concepts that will be used on the Astromag superconducting magnet facility. 3 refs., 2 figs.

  5. Cavitation in flowing superfluid helium

    NASA Technical Reports Server (NTRS)

    Daney, D. E.

    1988-01-01

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

  6. Design and Testing of a Superfluid Liquid Helium CoolingLoop

    SciTech Connect

    Gavin, L.M.; Green, M.A.; Levin, S.M.; Smoot, George F.; Witebsky, C.

    1989-07-24

    This paper describes the design and preliminary testing of a cryogenic cooling loop that uses a thermomechanical pump to circulate superfluid liquid helium. The cooling loop test apparatus is designed to prove forced liquid helium flow concepts that will be used on the Astromag superconducting magnet facility.

  7. Study of Cryogenic Plasma in Superfluid Liquid Helium

    DTIC Science & Technology

    2005-08-23

    Virial coefficient will be calculated. And the equation of state will give us a clue to the study of the critical phenomenon in the complex plasma...is satisfied by the presence of electrons, ions, and the charged fine particles. With the explicit formulation of the interaction energy, the second ...on the order of micro seconds in an X-band mode cylindrical cavity filled with Liquid helium. Although the transmission signals through the cavity

  8. Crystals, liquid crystals and superfluid helium on curved surfaces

    NASA Astrophysics Data System (ADS)

    Vitelli, Vincenzo

    In this thesis we study the ground state of ordered phases grown as thin layers on substrates with smooth spatially varying Gaussian curvature. The Gaussian curvature acts as a source for a one body potential of purely geometrical origin that controls the equilibrium distribution of the defects in liquid crystal layers, thin films of He4 and two dimensional crystals on a frozen curved surface. For superfluids, all defects are repelled (attracted) by regions of positive (negative) Gaussian curvature. For liquid crystals, charges between 0 and 4pi are attracted by regions of positive curvature while all other charges are repelled. As the thickness of the liquid crystal film increases, transitions between two and three dimensional defect structures are triggered in the ground state of the system. Thin spherical shells of nematic molecules with planar anchoring possess four short 12 disclination lines but, as the thickness increases, a three dimensional escaped configuration composed of two pairs of half-hedgehogs becomes energetically favorable. Finally, we examine the static and dynamical properties that distinguish two dimensional crystals constrained to lie on a curved substrate from their flat space counterparts. A generic mechanism of dislocation unbinding in the presence of varying Gaussian curvature is presented. We explore how the geometric potential affects the energetics and dynamics of dislocations and point defects such as vacancies and interstitials.

  9. Superfluid helium 2 liquid-vapor phase separation: Technology assessment

    NASA Technical Reports Server (NTRS)

    Lee, J. M.

    1984-01-01

    A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

  10. Production of Zero-Energy Radioactive Nuclear Beams through Extraction from the Liquid-Vapour Interface of Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Huang, W. X.; Dendooven, P.; Gloos, K.; Pekola, J. P.; ńystö, J.

    2004-04-01

    A new approach has been investigated to create an ultra-cold radioactive beam from high-energy ions. A 223Ra alpha-decay recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling 219Rn ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface has been possible thanks to the high sensitivity of radioactive ion detection. An efficiency of 36 % has been obtained for the ion extraction out of liquid helium.

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

    PubMed

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

    2014-08-22

    Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets. Copyright © 2014, American Association for the Advancement of Science.

  12. Radioactive Ions and Atoms in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Dendooven, P.; Purushothaman, S.; Gloos, K.; ńystö, J.; Takahashi, N.; Huang, W. X.

    2006-04-01

    We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve the extraction. Evaporating a thin surface layer of the liquid using second-sound pulses gave an extraction efficiency of 7.2 %.

  13. Superfluid Helium Tanker (SFHT) study

    NASA Technical Reports Server (NTRS)

    Eberhardt, Ralph N.; Dominick, Sam M.; Anderson, John E.; Gille, John P.; Martin, Tim A.; Marino, John S.; Paynter, Howard L.; Traill, R. Eric; Herzl, Alfred; Gotlib, Sam

    1988-01-01

    Replenishment of superfluid helium (SFHe) offers the potential of extending the on-orbit life of observatories, satellite instruments, sensors and laboratories which operate in the 2 K temperature regime. A reference set of resupply customers was identified as representing realistic helium servicing requirements and interfaces for the first 10 years of superfluid helium tanker (SFHT) operations. These included the Space Infrared Telescope Facility (SIRTF), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (Astromag), and the Microgravity and Materials Processing Sciences Facility (MMPS)/Critical Point Phenomena Facility (CPPF). A mixed-fleet approach to SFHT utilization was considered. The tanker permits servicing from the Shuttle cargo bay, in situ when attached to the OMV and carried to the user spacecraft, and as a depot at the Space Station. A SFHT Dewar ground servicing concept was developed which uses a dedicated ground cooling heat exchanger to convert all the liquid, after initial fill as normal fluid, to superfluid for launch. This concept permits the tanker to be filled to a near full condition, and then cooled without any loss of fluid. The final load condition can be saturated superfluid with any desired ullage volume, or the tank can be totally filed and pressurized. The SFHT Dewar and helium plumbing system design has sufficient component redundancy to meet fail-operational, fail-safe requirements, and is designed structurally to meet a 50 mission life usage requirement. Technology development recommendations were made for the selected SFHT concept, and a Program Plan and cost estimate prepared for a phase C/D program spanning 72 months from initiation through first launch in 1997.

  14. Effective mass of a charged carrier in a nonpolar liquid: Snowball effect in superfluid helium

    SciTech Connect

    Chikina, I.; Varlamov, A. A.

    2007-05-01

    The problem of a correct definition of the charged carrier effective mass in superfluid helium is revised. It is shown that the effective mass of such a quasiparticle can be introduced without Atkins's idea about the solidification of liquid He{sup 4} in the close vicinity of an ion (the so-called ''snowball'' model). Moreover, in addition to the generalization of Atkins's model, the charged carrier effective mass formation is considered within the framework of the two-fluid scenario. The physical reasons of the normal-fluid contribution divergency and the way of the corresponding regularization procedure are discussed. Agreement between the theory and the available experimental data is found in a wide range of temperatures.

  15. The Effective Mass of a Charged Carrier in a Nonpolar Liquid:. Applications to Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Varlamov, Andrei; Chikina, Ioulia; Shikin, Valeriy

    The problem of a correct definition of the charged carrier effective mass in superfluid helium is revised. It is shown that the effective mass of such a quasi-particle can be introduced without Atkins's idea about the solidification of liquid He4 in the close vicinity of an ion (the so-called “snowball” model). Moreover, in addition to generalization of the Atkins's model, the charged carrier effective mass formation is considered within the framework of the two-fluid scenario. The physical reasons of the normal fluid contribution divergency and the way of corresponding regularization procedure are discussed. Agreement between the theory and the available experimental data is found in a wide range of temperatures.

  16. Effective mass of a charged carrier in a nonpolar liquid: Snowball effect in superfluid helium

    NASA Astrophysics Data System (ADS)

    Chikina, I.; Shikin, V.; Varlamov, A. A.

    2007-05-01

    The problem of a correct definition of the charged carrier effective mass in superfluid helium is revised. It is shown that the effective mass of such a quasiparticle can be introduced without Atkins’s idea about the solidification of liquid He4 in the close vicinity of an ion (the so-called “snowball” model). Moreover, in addition to the generalization of Atkins’s model, the charged carrier effective mass formation is considered within the framework of the two-fluid scenario. The physical reasons of the normal-fluid contribution divergency and the way of the corresponding regularization procedure are discussed. Agreement between the theory and the available experimental data is found in a wide range of temperatures.

  17. The Effective Mass of a Charged Carrier in a Nonpolar Liquid:. Applications to Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Varlamov, Andrei; Chikina, Ioulia; Shikin, Valeriy

    2009-12-01

    The problem of a correct definition of the charged carrier effective mass in superfluid helium is revised. It is shown that the effective mass of such a quasi-particle can be introduced without Atkins's idea about the solidification of liquid He4 in the close vicinity of an ion (the so-called "snowball" model). Moreover, in addition to generalization of the Atkins's model, the charged carrier effective mass formation is considered within the framework of the two-fluid scenario. The physical reasons of the normal fluid contribution divergency and the way of corresponding regularization procedure are discussed. Agreement between the theory and the available experimental data is found in a wide range of temperatures.

  18. Superfluid Helium Heat Pipe

    NASA Astrophysics Data System (ADS)

    Gully, P.

    This paper reports on the development and the thermal tests of three superfluid helium heat pipes. Two of them are designed to provide a large transport capacity (4 mW at 1.7 K). They feature a copper braid located inside a 6 mm outer diameter stainless tube fitted with copper ends for mechanical anchoring. The other heat pipe has no copper braid and is designed to get much smaller heat transport capacity (0.5 mW) and to explore lower temperature (0.7 - 1 K). The copper braid and the tube wall is the support of the Rollin superfluid helium film in which the heat is transferred. The low filling pressure makes the technology very simple with the possibility to easily bend the tube. We present the design and discuss the thermal performance of the heat pipes tested in the 0.7 to 2.0 K temperature range. The long heat pipe (1.2 m with copper braid) and the short one (0.25 m with copper braid) have similar thermal performance in the range 0.7 - 2.0 K. At 1.7 K the long heat pipe, 120 g in weight, reaches a heat transfer capacity of 6.2 mW and a thermal conductance of 600 mW/K for 4 mW transferred power. Due to the pressure drop of the vapor flow and Kapitza thermal resistance, the conductance of the third heat pipe dramatically decreases when the temperature decreases. A 3.8 mW/K is obtained at 0.7 K for 0.5 mW transferred power.

  19. Superfluid helium leak sealant study

    NASA Technical Reports Server (NTRS)

    Vorreiter, J. W.

    1981-01-01

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

  20. Rotons, Superfluidity, and Helium Crystals

    SciTech Connect

    Balibar, Sebastien

    2006-09-07

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

  1. Superfluid helium-4 in one dimensional channel

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  2. Low gravity thermal stratification of liquid helium on SHOOT. [Superfluid Helium On-Orbit Transfer

    NASA Technical Reports Server (NTRS)

    Shirron, P. J.; Dipirro, M. J.

    1992-01-01

    Estimates of the extent and impact of thermal stratification are presented as well as predictions of the behavior of the HeI/HeII boundary. Although thermal stratification of cryogens can be problematic and lead to their inefficient use in low gravity, for SHOOT the occurrence is beneficial both during ground hold and in orbit and presents no hazards. On the ground the parasitic heat load is both reduced and more efficiently removed. In orbit the pumpdown proceeds at a much more rapid rate, allowing orbital operations to begin earlier. The thermal conductivity of the aluminum tank and the normal liquid plus cooling at the liquid/vapor interface as the vapor bubble grows are sufficient to prevent undesirably high vapor pressures in the tank.

  3. Resource Letter SH-1: Superfluid Helium.

    ERIC Educational Resources Information Center

    Hallock, Robert B.

    1982-01-01

    Provides an annotated list of books, textbooks, and films on superfluid helium. Also lists research reports/reviews arranged by category, including among others, early history, microscopic understanding, ions in helium, helium in rotation, vortices and quantization, helium films and constricted geometrics, persistence flow, and superfluid helium…

  4. Resource Letter SH-1: Superfluid Helium.

    ERIC Educational Resources Information Center

    Hallock, Robert B.

    1982-01-01

    Provides an annotated list of books, textbooks, and films on superfluid helium. Also lists research reports/reviews arranged by category, including among others, early history, microscopic understanding, ions in helium, helium in rotation, vortices and quantization, helium films and constricted geometrics, persistence flow, and superfluid helium…

  5. Vorticity matching in superfluid helium

    NASA Astrophysics Data System (ADS)

    Samuels, David C.

    1991-12-01

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

  6. Particle-Vortex Interaction in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Barenghi, Carlo F.

    2008-11-01

    The application of the classical Particle Image Velocimetry (PIV) technique in liquid helium has opened the way to better visualization of superfluid turbulence. To interpret the data, it is necessary to understand the interaction between micron-size tracer particles and vortex lines. This talk summarizes current understanding of this interaction resulting from theoretical and numerical calculations. In collaboration with Yuri A. Sergeev, Newcastle University.

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

    NASA Astrophysics Data System (ADS)

    Huang, W. X.; Dendooven, P.; Gloos, K.; Takahashi, N.; Arutyunov, K.; Pekola, J. P.; Äystö, J.

    2003-05-01

    A new approach to convert a high energy beam to a low energy one, which is essential for the next generation radioactive ion beam facilities, has been proposed and tested at Jyväskylä, Finland. An open 223Ra alpha-decay-recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling 219Rn ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface was possible thanks to the high sensitivity of radioactivity detection. An efficiency of 36% was obtained for the ion extraction out of liquid helium.

  8. Progress on Study of Electric Breakdown in Superfluid Liquid Helium for the SNS nEDM Experiment

    NASA Astrophysics Data System (ADS)

    Wei, Wanchun; Beck, Douglas; Bouman, Nathaniel; Cianciolo, Vince; Clayton, Steven; Crawford, Christopher; Currie, Scott; Griffith, William; Ito, Takeyasu; Ramsey, John; Schmid, Richardo; Seidel, George; Stanislaus, Shirvel; Tang, Zhaowen; Wagner, Daniel; Williamson, Steven; Yao, Weijun; SNS nEDM Collaboration

    2016-09-01

    The SNS nEDM collaboration is developing an experiment to search for the neutron's electric dipole moment (EDM) to be run at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. As the experimental sensitivity depends linearly on the strength of applied electric field, it is of critical importance to achieve a strong and stable electric field in the storage region of ultracold neutrons (UCN) in superfluid helium. However, the phenomenon of electric breakdown in liquid helium is poorly understood, and as such a major R&D effort is under way. We have developed an apparatus to test various coating materials on electrodes of 12 cm diameter and study breakdown in liquid helium at temperatures as low as 0.4 K and pressures between saturated vapor pressure and 1 atm. Meanwhile, a small test apparatus has been used to study various aspects of breakdown phenomenon. In this talk, the present status of our effort, implication of findings on the SNS nEDM experiment and future plans will be presented.

  9. Development of Toroidal Magnetic Thermometry to Study New Phenomena Associated with the Superfluid Transition in Liquid HELIUM-4

    NASA Astrophysics Data System (ADS)

    Duncan, Robert Vance

    A new type of paramagnetic susceptibility thermometry called toroidal magnetic thermometry (TMT) has been developed. These TMT thermometers have a thermal resolution of five nanoKelvin near the ^4He superfluid transition temperature T_lambda = 2.172K, making TMT roughly a factor of fifty times better in resolution than conventional germanium resistance thermometry which is commercially available. The dramatic improvement in thermal resolution provided by TMT has been used to observe new phenomena associated with the superfluid transition in pure liquid ^4He. Such phenomena include a component of the thermal boundary (Kapitza) resistance R_{rm K} which is singular at the superfluid transition temperature T_lambda. In addition to the singularity, measurements of R _{rm K} exhibit a strong dependence on the heat current Q used to make the measurements for reduced temperature t equiv 1 - T/T_lambda<=ss than t_{rm c}(Q). This t_{rm c} was observed to be approximately proportional to Q. For t < t_{rm c} the initial value of the derivative dR_ {rm K}/dQ was observed to be approximately proportional to 1/t. In addition to the boundary effects described above, these TMT thermometers have been used to detect the depression of T_lambda by a heat current Q flowing through the liquid helium. Due to the ultrahigh resolution of the TMT thermometers this effect has been studied using values of Q < 10 muW/cm^2 where superfluid thermal gradients have been observed to be very small. When these values of Delta T_lambda(Q) were used to calculate the depression of the superfluid density Deltarho_{ rm s}(Q) the results agreed well with a prediction based on the theory of Ginzburg and Pitaevskii. The calibration of the TMT thermometers provide high-resolution measurements of the a.c. paramagnetic susceptibility of their magnetic salt: Copper ammonium bromide (CAB). These calibration parameters, together with power dissipation data near the CAB Curie temperature T_{rm c} = 1.795K, provide

  10. Superfluid Helium Tanker (SFHT) study

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The accomplishments and recommendations of the two-phase Superfluid Helium Tanker (SFHT) study are presented. During the first phase of the study, the emphasis was on defining a comprehensive set of user requirements, establishing SFHT interface parameters and design requirements, and selecting a fluid subsystem design concept. During the second phase, an overall system design concept was constructed based on appropriate analyses and more detailed definition of requirements. Modifications needed to extend the baseline for use with cryogens other than SFHT have been determined, and technology development needs related to the recommended design have been assessed.

  11. Detection of charged particles in superfluid helium

    SciTech Connect

    Bandler, Simon R.

    1994-12-01

    This thesis is concerned with the use of a large superfluid helium detector for the detection of solar neutrinos. A small-scale prototype of this type of detector has been constructed and tested. In this thesis the author discussed in detail the design of the apparatus, the experiments which have been carried out, and what has been learned about the important physical processes involved in this type of detector. These processes include the anisotropic generation of phonons and rotons by the recoiling particle, the propagation of the phonons and rotons in the liquid, the evaporation process at the liquid surface, and the adsorption of the helium atoms onto the wafers. In addition he discusses the generation and detection of fluorescent photons from recoiling particles. The implications of these results to the design of a full-scale detector of neutrinos are discussed.

  12. Electric response in superfluid helium

    NASA Astrophysics Data System (ADS)

    Chagovets, Tymofiy V.

    2016-05-01

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

  13. Development of a motorized cryovalve for the control of superfluid liquid helium

    NASA Technical Reports Server (NTRS)

    Lorell, K. R.; Aubrun, J-N.; Zacharie, D. F.; Frank, D. J.

    1988-01-01

    Recent advances in the technology of infrared detectors have made possible a wide range of scientific measurements and investigations. One of the requirements for the use of sensitive IR detectors is that the entire instrument be cooled to temperatures approaching absolute zero. The cryogenic cooling system for these instruments is commonly designed as a large dewar containing liquid helium which completely surrounds the apparatus. Thus, there is a need for a remotely controlled, motorized cryovalve that is simple, reliable, and compact and can operate over extended periods of time in cryo-vac conditions. The design, development, and test of a motorized cryovalve with application to a variety of cryogenic systems currently under development is described.

  14. Three Dimensional Particle Tracking in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Megson, Peter

    2016-11-01

    Superfluid helium is a macroscopic quantum state which exhibits exotic physical properties, such as flow without friction and ballistic heat transport. Superfluid flow is irrotational except about line-like topological phase defects with quantized circulation, known as quatized vortices. The presence of these vortices and their dynamics is the dominating factor of turbulence in superfluid flows. One commonly studied regime of superfluid turbulence is thermal counterflow, where a local heat flux drives the formation and growth of a tangle of vortices. This talk will present experimental studies of counterflow turbulence performed using a multi-camera three-dimensional imaging apparatus with micron-sized ice tracer particles as well as fluorescent nanoparticles. In particular, we will discuss the measurement of three-dimensional velocties and their autocorrelations. Additionally, we are developing new techniques for optical studies of bulk superfluid helium, with particular focus on characterizing tracer particles and particle dispersal mechanisms. Funding from NSF DMR-1407472.

  15. Substrate Effects in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Steel, Stephen Chris

    1990-01-01

    The self emptying beaker technique was used to study the superfluid properties of ^3He confined in the van der Waals film adsorbed on the surface of a metal beaker. The experimental cell was designed to minimize thermal gradients along the ^3 He film. In contrast to the results of an earlier experiment by Sachrajda et al, which suggested that film flow occurred at temperatures as high as 3.5 mK (SACH-85), no flow was observed above the bulk transition temperature T_sp{rm c}{rm B} = 0.93 mK. The transition temperatures measured using round rim beakers agreed with theory, giving the predicted normal-superfluid phase boundary 2 delta/xi(T) = pi, where delta is the film thickness and xi(T) is the temperature dependent coherence length. The ^3He film thickness was inferred from Atkins' oscillation measurements of ^4He films on the same substrate. When a ^4He monolayer was adsorbed on the surface of a copper beaker, it suppressed the diffuse scattering of ^3He quasiparticles at the copper wall, an effect first observed by Freeman et al using a mylar substrate (FRMN-88). With the ^4He monolayer in place, there was no measurable suppression of the transition temperature, even for films as thin as 100 nm. This suggests that the ^3 He quasiparticle scattering at the free liquid surface as well as the ^4He covered substrate was specular. This is the first evidence of the nature of the scattering at the free surface. After the ^3He level in the beaker had dropped between 15 and 85 mu m, the flow rate abruptly dropped by a factor to ten or more. This may be associated with the transition between the superfluid B-phase, expected in thick films, and the superfluid A-phase, expected in thin films. The observed critical currents are roughly an order of magnitude smaller than predicted by the pair breaking limit, suggesting some other dissipation mechanism is responsible for limiting the current.

  16. Superfluid Helium from the Macroscopic to the Microscopic

    SciTech Connect

    Van Sciver, Steven W. (Florida State University

    2004-02-11

    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.

  17. Germanium resistance thermometer calibration at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1985-01-01

    The rapid increase in resistance of high purity semi-conducting germanium with decreasing temperature in the superfluid helium range of temperatures makes this material highly adaptable as a very sensitive thermometer. Also, a germanium thermometer exhibits a highly reproducible resistance versus temperature characteristic curve upon cycling between liquid helium temperatures and room temperature. These two factors combine to make germanium thermometers ideally suited for measuring temperatures in many cryogenic studies at superfluid helium temperatures. One disadvantage, however, is the relatively high cost of calibrated germanium thermometers. In space helium cryogenic systems, many such thermometers are often required, leading to a high cost for calibrated thermometers. The construction of a thermometer calibration cryostat and probe which will allow for calibrating six germanium thermometers at one time, thus effecting substantial savings in the purchase of thermometers is considered.

  18. Germanium resistance thermometer calibration at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1985-01-01

    The rapid increase in resistance of high purity semi-conducting germanium with decreasing temperature in the superfluid helium range of temperatures makes this material highly adaptable as a very sensitive thermometer. Also, a germanium thermometer exhibits a highly reproducible resistance versus temperature characteristic curve upon cycling between liquid helium temperatures and room temperature. These two factors combine to make germanium thermometers ideally suited for measuring temperatures in many cryogenic studies at superfluid helium temperatures. One disadvantage, however, is the relatively high cost of calibrated germanium thermometers. In space helium cryogenic systems, many such thermometers are often required, leading to a high cost for calibrated thermometers. The construction of a thermometer calibration cryostat and probe which will allow for calibrating six germanium thermometers at one time, thus effecting substantial savings in the purchase of thermometers is considered.

  19. Pump performance requirement for the liquid helium orbital resupply tanker

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Ng, Y. S.

    1988-01-01

    The Liquid Helium Orbital Resupply Tanker (currently renamed to Superfluid Helium Tanker) will greatly enhance the lifetime of the space missions which require superfluid helium. The Superfluid Helium Tanker pump performance requirement is driven by the superfluid helium replenishment needs of the Space Infrared Telescope Facility (SIRTF). SIRTF is one of the space missions which will require on-orbit superfluid helium resupply in the 1990s. The Superfluid Helium Tanker will carry at least 10,000 L of superfluid helium and provide a minimum pump head of 170 torr (0 to 200 L/h) to cool SIRTF from 150 to 2 K. When the SIRTF tank starts to collect liquid, a minimum flow rate of 300 L/h with a pump head of 60 torr is required to fill the 4000-liter tank.

  20. Cosmological experiments in superfluid helium?

    NASA Astrophysics Data System (ADS)

    Zurek, W. H.

    1985-10-01

    Symmetry breaking phase transitions occurring in the early Universe are expected to leave behind long-lived topologically stabel structures such as monopoles, strings or domain walls. The author discusses the analogy between cosmological strings and vortex lines in the superfluid, and suggests a cryogenic experiment which tests key elements of the cosmological scenario for string formation. In a superfluid obtained through a rapid pressure quench, the phase of the Bose condensate wavefunction - the 4He analogue of the broken symmetry of the field-theoretic vacuum - will be chosen randomly in domains of some characteristic size d. When the quench is performed in an annulus of circumference C the typical value of the phase mismatch around the loop will be ≡(C/d)1/2. The resulting phase gradient can be sufficiently large to cause the superfluid to flow with a measurable, randomly directed velocity.

  1. Experiments on the properties of superfluid helium in zero gravity

    NASA Technical Reports Server (NTRS)

    Mason, P.; Collins, D.; Petrac, D.; Yang, L.; Edeskuty, F.; Williamson, K.

    1976-01-01

    The paper describes a research program designed to study the behavior of superfluid liquid helium in low and zero gravity in order to determine the properties which are critically important to its use as a stored cryogen for cooling scientific instruments aboard spacecraft for periods up to several months. The experiment program consists of a series of flights of an experiment package on a free-fall trajectory both on an aircraft and on a rocket. The objectives are to study thickness of thin films of helium as a function of acceleration, heat transfer in thin films, heat transfer across copper-liquid helium interfaces, fluid dynamics of bulk helium in high and low accelerations and under various conditions of rotations, alternate methods of separation of liquid and vapor phases and of efficient venting of the vapor, and undesirable thermomechanical oscillations in the vent pipes. Preliminary results from aircraft tests are discussed.

  2. Fiber-Cavity Optomechanics with Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Flowers-Jacobs, Nathan E.; Kashkanova, Anna D.; Shkarin, Alexey B.; Hoch, Scott W.; Deutsch, Christian; Reichel, Jakob; Harris, Jack G. E.

    2014-03-01

    In a typical optomechanical device, the resonance frequency of a cavity is coupled to mechanical motion through the radiation pressure force. To date, experimental cavities have predominately coupled to a resonant mechanical mode of a solid structure, often a lithographically-defined beam or membrane. We will describe our progress towards realizing an optomechanical device in which an optical fiber-cavity couples to the acoustic modes of superfluid helium. In this system, the optical modes and the acoustic modes of the superfluid are co-located between the mirrored ends of two fiber optic cables. Changes in the density of the superfluid change the effective length of the cavity which results in a standard, linear optomechanical coupling between the 300 MHz acoustic resonances and the 200 THz optical resonances. This type of device is motivated by the self-aligning nature of the acoustic and optical modes (which eases the difficulties of operating at cryogenic temperatures) and by the low optical and mechanical losses of superfluid helium. Although we expect the mechanical quality factor to be limited by acoustic radiation into the glass fiber, we will describe a proposal to realize a dual-band Bragg mirror to confine the optical and acoustic modes more efficiently. Supported by NSF Grant #1106110, ARO Grant #W911NF-13-1-0104, and the DARPA/MTO ORCHID program through a grant from AFOSR.

  3. Tkachenko waves in rotating superfluid helium

    SciTech Connect

    Andereck, C.D.; Chalupa, J.; Glaberson, W.I.

    1980-01-07

    The resonant response of a stack of disks driven into torsional oscillation within a container of rotating superfluid helium has been observed. It is shown that the oscillation modes excited are related to Tkachenko waves, that is, vortex displacement waves in the vortex array propagating in a direction transverse to the vortex lines. In particular, the resonances occur at peaks in the vortex wave density of states.

  4. Dynamics of Superfluid Helium in Low-Gravity

    NASA Technical Reports Server (NTRS)

    Frank, David J.

    1997-01-01

    This report summarizes the work performed under a contract entitled 'Dynamics of Superfluid Helium in Low Gravity'. This project performed verification tests, over a wide range of accelerations of two Computational Fluid Dynamics (CFD) codes of which one incorporates the two-fluid model of superfluid helium (SFHe). Helium was first liquefied in 1908 and not until the 1930s were the properties of helium below 2.2 K observed sufficiently to realize that it did not obey the ordinary physical laws of physics as applied to ordinary liquids. The term superfluidity became associated with these unique observations. The low temperature of SFHe and it's temperature unifonrmity have made it a significant cryogenic coolant for use in space applications in astronomical observations with infrared sensors and in low temperature physics. Superfluid helium has been used in instruments such as the Shuttle Infrared Astronomy Telescope (IRT), the Infrared Astronomy Satellite (IRAS), the Cosmic Background Observatory (COBE), and the Infrared Satellite Observatory (ISO). It is also used in the Space Infrared Telescope (SIRTF), Relativity Mission Satellite formally called Gravity Probe-B (GP-B), and the Test of the Equivalence Principle (STEP) presently under development. For GP-B and STEP, the use of SFHE is used to cool Superconducting Quantum Interference Detectors (SQUIDS) among other parts of the instruments. The Superfluid Helium On-Orbit Transfer (SHOOT) experiment flown in the Shuttle studied the behavior of SFHE. This experiment attempted to get low-gravity slosh data, however, the main emphasis was to study the low-gravity transfer of SFHE from tank to tank. These instruments carried tanks of SFHE of a few hundred liters to 2500 liters. The capability of modeling the behavior of SFHE is important to spacecraft control engineers who must design systems that can overcome disturbances created by the movement of the fluid. In addition instruments such as GP-B and STEP are very

  5. Growing metal nanoparticles in superfluid helium.

    PubMed

    Yang, Shengfu; Ellis, Andrew M; Spence, Daniel; Feng, Cheng; Boatwright, Adrian; Latimer, Elspeth; Binns, Chris

    2013-12-07

    Helium droplets provide a cold and confined environment where atomic and/or molecular dopants can aggregate into clusters and nanoparticles. In particular, the sequential addition of different materials to helium droplets can lead to the formation of a wide range of nanoparticles, including core-shell nanoparticles, which can then be deposited onto a surface. Here we briefly discuss the fundamental properties of helium droplets and then address their implications for the formation of clusters and nanoparticles. Several key experiments on atomic and molecular clusters will be highlighted and new results obtained for nanoparticles formed in this way will be presented. Finally, the versatility, the limitations and new possibilities provided by superfluid helium droplets in nanoscience and nanotechnology will be addressed.

  6. Stabilization of Multi-electron Bubbles in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Silvera, Isaac F.; Fang, Jieping; Tempere, Jacques

    2014-12-01

    Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes and the difficulty to localize them. We report the observation of long- lived MEBs in a novel cell filled with superfluid helium at static negative pressures. MEBs were extracted from the electron filled vapor sheath of a heated filament loop embedded in the superfluid helium and observed by high-speed photography. MEBs are 2D electron gases on the 3D surface of hollow helium bubbles. Diameters can range from nanometers to millimeters, depending on the number of enclosed electrons. Electrons move in angular momentum states; deformations of the surface are called spherical ripplons. The attractive electron-ripplon interaction leads to an unusual form of superconductivity. If they can be compressed, Wigner crystallization and quantum melting can be observed, as well as a new phase for localization called the ripplo- polaron lattice. MEBs are unstable to tunneling discharge when pressed against a surface. Just as Bose gases are captured in a trap for study, MEBs must also be localized away from walls. We shall discuss methods of capturing them in an electromagnetic trap embedded in the liquid helium.

  7. Infrared Astronomical Satellite (IRAS) superfluid helium tank temperature control

    NASA Technical Reports Server (NTRS)

    Petrac, D.; Mason, P. V.

    1984-01-01

    The infrared detectors on the Infrared Astronomical Satellite (IRAS), which was placed into a polar orbit in January 1983, are cooled to a temperature of less than 3 K by thermal coupling to the main cryogenic tank (MCT) containing superfluid helium. A porous plug built into the vent line entrance acts as a superfluid helium liquid/vapor separator in zero gravity. A description of the IRAS MCT flight porous plug is presented, and tests of the plug in situ are discussed, taking into account submerged plug tests, a restart test, and a cold vapor flow test. Aspects of flow rate determination in the case of an unavailability of flight flow rate data are also considered.

  8. Characterization of reconnecting vortices in superfluid helium

    PubMed Central

    Bewley, Gregory P.; Paoletti, Matthew S.; Sreenivasan, Katepalli R.; Lathrop, Daniel P.

    2008-01-01

    When two vortices cross, each of them breaks into two parts and exchanges part of itself for part of the other. This process, called vortex reconnection, occurs in classical and superfluids, and in magnetized plasmas and superconductors. We present the first experimental observations of reconnection between quantized vortices in superfluid helium. We do so by imaging micrometer-sized solid hydrogen particles trapped on quantized vortex cores and by inferring the occurrence of reconnection from the motions of groups of recoiling particles. We show that the distance separating particles on the just-reconnected vortex lines grows as a power law in time. The average value of the scaling exponent is approximately ½, consistent with the self-similar evolution of the vortices. PMID:18768790

  9. Superfluidity of Dense ^4Helium in Vycor

    NASA Astrophysics Data System (ADS)

    Khairallah, Saad; Ceperley, David

    2005-03-01

    We calculate properties of a model of ^4He in Vycor using the Path Integral Monte Carlo method to understand the recent experiments of Kim and Chan. In particular we calculate both the density and the superfluid response in the layers immediately above a rough vycor surface. In the second and third layers above the vycor, there is small but not insignificant delocalization caused by the strong density gradient and resulting incommensurate lattice structure. We also find that ^3He impurities tend to populate these layers, which reduces the superfluid density as is found in the experiment. Our results are consistent with the persistent liquid layer model to explain the observations.

  10. Shapes of rotating superfluid helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Bernando, Charles; Tanyag, Rico Mayro P.; Jones, Curtis; Bacellar, Camila; Bucher, Maximilian; Ferguson, Ken R.; Rupp, Daniela; Ziemkiewicz, Michael P.; Gomez, Luis F.; Chatterley, Adam S.; Gorkhover, Tais; Müller, Maria; Bozek, John; Carron, Sebastian; Kwok, Justin; Butler, Samuel L.; Möller, Thomas; Bostedt, Christoph; Gessner, Oliver; Vilesov, Andrey F.

    2017-02-01

    Rotating superfluid He droplets of approximately 1 μm in diameter were obtained in a free nozzle beam expansion of liquid He in vacuum and were studied by single-shot coherent diffractive imaging using an x-ray free electron laser. The formation of strongly deformed droplets is evidenced by large anisotropies and intensity anomalies (streaks) in the obtained diffraction images. The analysis of the images shows that in addition to previously described axially symmetric oblate shapes, some droplets exhibit prolate shapes. Forward modeling of the diffraction images indicates that the shapes of rotating superfluid droplets are very similar to their classical counterparts, giving direct access to the droplet angular momenta and angular velocities. The analyses of the radial intensity distribution and appearance statistics of the anisotropic images confirm the existence of oblate metastable superfluid droplets with large angular momenta beyond the classical bifurcation threshold.

  11. A superfluid helium system for an LST IR experiment

    NASA Technical Reports Server (NTRS)

    Breckenridge, R. W., Jr.; Moore, R. W., Jr.

    1975-01-01

    The results are presented of a study program directed toward evaluating the problems associated with cooling an LST instrument to 2 K for a year by using superfluid helium as the cooling means. The results include the parametric analysis of systems using helium only, and systems using helium plus a shield cryogen. A baseline system, using helium only is described. The baseline system is sized for an instrument heat leak of 50 mw. It contains 71 Kg of superfluid helium and has a total, filled weight of 217 Kg. A brief assessment of the technical problems associated with a long life, spaceborne superfluid helium storage system is also made. It is concluded that a one year life, superfluid helium cooling system is feasible, pending experimental verification of a suitable low g vent system.

  12. Temperature rise in superfluid helium pumps

    SciTech Connect

    Kittel, P.

    1988-07-01

    The temperature rise of a fountain effect pump (FEP) and of a centrifugal pump (CP) are compared. Calculations and estimates presented here show that under the operating conditions expected during the resupply of superfluid helium in space, a centrifugal pump will produce a smaller temperature rise than will a fountain effect pump. The temperature rise for the FEP is calculated assuming an ideal pump, while the temperature rise of the CP is estimated from the measured performance of a prototype pump. As a result of this smaller temperature rise and of the different operating characteristics of the two types of pumps, transfers will be more effective using a centrifugal pump.

  13. Temperature rise in superfluid helium pumps

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1988-01-01

    The temperature rise of a fountain effect pump (FEP) and of a centrifugal pump (CP) are compared. Calculations and estimates presented here show that under the operating conditions expected during the resupply of superfluid helium in space, a centrifugal pump will produce a smaller temperature rise than will a fountain effect pump. The temperature rise for the FEP is calculated assuming an ideal pump, while the temperature rise of the CP is estimated from the measured performance of a prototype pump. As a result of this smaller temperature rise and of the different operating characteristics of the two types of pumps, transfers will be more effective using a centrifugal pump.

  14. Cryogenic system for X-ray Compton scattering measurements of superfluid helium below 2 K

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroyuki; Yamaguchi, Akira; Koizumi, Akihisa; Kawasaki, Ikuto; Sumiyama, Akihiko; Itou, Masayoshi; Sakurai, Yoshiharu

    2017-07-01

    A cryostat was constructed for high-resolution X-ray Compton scattering measurements at temperature down to 1.7 K, in order to investigate superfluid helium-4. Compton profiles of helium were measured using synchrotron X-rays for gas and liquid phases, respectively. In the measurement of the liquid phase, we succeeded in measuring the Compton profile of the superfluid helium at 1.7 K. Comparison of the results with theoretical calculation reveals importance of many-body effects beyond the mean-field treatment of electron systems.

  15. Particle Image Velocimetry in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Fuzier, Sylvie

    2008-11-01

    The Particle Image Velocimetry (PIV) technique has been expanded recently to the very low temperature environment to study the unique behavior of superfluid helium. Superfluid helium (He II) is a peculiar fluid with apparent zero viscosity and extraordinary heat transfer capabilities. The model that is traditionally used to explain this behavior considers He II to be made of two interpenetrating fluid components, one being viscous and the other being non-viscous. Recently, the PIV technique has been introduced to He II experimentation in an attempt to visualize the unique transport properties. As part of this effort, appropriate particles and seeding techniques have been developed for this low temperature fluid in order to measure the velocities of these internal flows. Initially, it was expected that the particles would track the viscous fluid component of He II, but several recent experiments have demonstrated their interaction with the non viscous fluid component as well. In order to fully benefit from the PIV technique to increase our knowledge and understanding of this unique fluid, the motion of the particles needs to be understood in terms of the motion of the two fluid components. An experiment combining heat transfer and forced flow allows one to independently vary these two component velocities and correlate them with the velocity of the seeded particles. In collaboration with Ernesto Bosque, Ting Xu, and Steven Van Sciver, NHMFL / Florida State University.

  16. On charged impurity structures in liquid helium

    NASA Astrophysics Data System (ADS)

    Pelmenev, A. A.; Krushinskaya, I. N.; Bykhalo, I. B.; Boltnev, R. E.

    2016-03-01

    The thermoluminescence spectra of impurity-helium condensates (IHC) submerged in superfluid helium have been observed for the first time. Thermoluminescence of impurity-helium condensates submerged in superfluid helium is explained by neutralization reactions occurring in impurity nanoclusters. Optical spectra of excited products of neutralization reactions between nitrogen cations and thermoactivated electrons were rather different from the spectra observed at higher temperatures, when the luminescence due to nitrogen atom recombination dominates. New results on current detection during the IHC destruction are presented. Two different mechanisms of nanocluster charging are proposed to describe the phenomena observed during preparation and warm-up of IHC samples in bulk superfluid helium, and destruction of IHC samples out of liquid helium.

  17. Acquisition system testing with superfluid helium. [cryopumping for space

    NASA Technical Reports Server (NTRS)

    Anderson, John E.; Fester, Dale A.; Dipirro, Michael J.

    1988-01-01

    Minus one-g outflow tests were conducted with superfluid helium in conjunction with a thermomechanical pump setup in order to study the use of capillary acquisition systems for NASA's Superfluid Helium On-Orbit Transfer (SHOOT) flight experiment. Results show that both fine mesh screen and porous sponge systems are capable of supplying superfluid helium to the thermomechanical pump inlet against a one-g head up to 4 cm, fulfilling the SHOOT requirements. Sponge results were found to be reproducible, while the screen results were not.

  18. Acquisition system testing with superfluid helium. [cryopumping for space

    NASA Technical Reports Server (NTRS)

    Anderson, John E.; Fester, Dale A.; Dipirro, Michael J.

    1988-01-01

    Minus one-g outflow tests were conducted with superfluid helium in conjunction with a thermomechanical pump setup in order to study the use of capillary acquisition systems for NASA's Superfluid Helium On-Orbit Transfer (SHOOT) flight experiment. Results show that both fine mesh screen and porous sponge systems are capable of supplying superfluid helium to the thermomechanical pump inlet against a one-g head up to 4 cm, fulfilling the SHOOT requirements. Sponge results were found to be reproducible, while the screen results were not.

  19. Observation of a superfluid component within solid helium.

    PubMed

    Lauter, H; Apaja, V; Kalinin, I; Kats, E; Koza, M; Krotscheck, E; Lauter, V V; Puchkov, A V

    2011-12-23

    We demonstrate by neutron scattering that a localized superfluid component exists at high pressures within solid helium in aerogel. Its existence is deduced from the observation of two sharp phonon-roton spectra which are clearly distinguishable from modes in bulk superfluid helium. These roton excitations exhibit different roton gap parameters than the roton observed in the bulk fluid at freezing pressure. One of the roton modes disappears after annealing the samples. Comparison with theoretical calculations suggests that the model that reproduces the observed data best is that of superfluid double layers within the solid and at the helium-substrate interface.

  20. Transient heat transfer in superfluid helium

    SciTech Connect

    Dresner, L.

    1981-01-01

    According to the Goerter-Mellink law, the heat flux in superfluid helium is proportional to the cube root of the temperature gradient. If we use this proportionality in place of Fourier's linear law to derive an equation of heat conduction, we obtain a non-linear partial differential equation. Such equations are usually difficult to solve because we cannot superpose solutions to obtain others. In spite of this, the problem of this paper, the constant-flux problem, can be solved because its temperature profiles are self-similar. Self-similarity means that the temperature profile at one time can be obtained from that at a different time by suitable (different) stretching of the distance and temperature axes of the latter profle. The self-similarity of the temperature profiles is connected with the invariance of the non-linear partial differential equation to certain groups of transformations. We reduce the partial differential equation of heat conduction to an ordinary differential equation, the appropriate solution of which we find without extensive computation. The reduction involves the similarity variables ..delta..T/..sqrt..t and z/..sqrt..t, where ..delta..T is the temperature rise at a distance z from the heated face at a time t after the (constant) heating has begun. Use of these variables should, and does, reduce all of the experimental temperature profiles reported by van Sciver to a single, universal curve. We obtain this curve as well by solving the differential equation; agreement is excellent. In fact agreement with all the experimental data reported by van Sciver is excellent, so that the Goerter-Mellink law seems to be a very successful basis for describing transient heat transfer in superfluid helium.

  1. Acquisition and transfer of superfluid helium in space

    NASA Astrophysics Data System (ADS)

    Martin, T. A.; Gille, J. P.; Anderson, J. E.

    1990-03-01

    The unique physical properties of superfluid helium (SFHe) or He II strongly influence the design of a system for transfer of this fluid in space. Conventional methods of pumping, particularly pressure difference transfer and centrifugal pumping, are ineffective because of the inability to pressurize SFHe with helium vapor, either to provide the transfer force or to provide a suction head for a pump. The thermomechanical (TM) pump, however, relying on the two-fluid characteristics of SFHe, provides a viable approach for pumping the fluid. Examination of the functioning of a TM pump shows that the flow in the liquid acquistion device is unconventional. Only the superfluid component defined in the two-fluid model of SFHe flows into the pump and, therefore, from the liquid source to the pump inlet via the acquisition device. Experiments have been conducted to characterize this 'superflow' in small tubes, and results are extrapolated to show the effects of this unique flow mechanism on a typical full scale transfer system.

  2. Theoretical Studies of Liquid He-4 Near the Superfluid Transition

    NASA Technical Reports Server (NTRS)

    Manousakis, Efstratios

    2002-01-01

    We performed theoretical studies of liquid helium by applying state of the art simulation and finite-size scaling techniques. We calculated universal scaling functions for the specific heat and superfluid density for various confining geometries relevant for experiments such as the confined helium experiment and other ground based studies. We also studied microscopically how the substrate imposes a boundary condition on the superfluid order parameter as the superfluid film grows layer by layer. Using path-integral Monte Carlo, a quantum Monte Carlo simulation method, we investigated the rich phase diagram of helium monolayer, bilayer and multilayer on a substrate such as graphite. We find excellent agreement with the experimental results using no free parameters. Finally, we carried out preliminary calculations of transport coefficients such as the thermal conductivity for bulk or confined helium systems and of their scaling properties. All our studies provide theoretical support for various experimental studies in microgravity.

  3. Taylor cone and electrospraying at a free surface of superfluid helium charged from below

    NASA Astrophysics Data System (ADS)

    Moroshkin, P.; Leiderer, P.; Möller, Th. B.; Kono, K.

    2017-05-01

    Electrically charged metallic micro- and nanoparticles are trapped under a free surface of superfluid He in a vertical static electric field. We observe a static deformation of the charged liquid surface in the form of a Taylor cone and the emission of a charged liquid helium jet (electrospray). Our numeric calculations reproduce the static shape of the cone.

  4. Robust Ferromagnetism of Chromium Nanoparticles Formed in Superfluid Helium.

    PubMed

    Yang, Shengfu; Feng, Cheng; Spence, Daniel; Al Hindawi, Aula M A A; Latimer, Elspeth; Ellis, Andrew M; Binns, Chris; Peddis, Davide; Dhesi, Sarnjeet S; Zhang, Liying; Zhang, Yafei; Trohidou, Kalliopi N; Vasilakaki, Marianna; Ntallis, Nikolaos; MacLaren, Ian; de Groot, Frank M F

    2017-01-01

    Chromium nanoparticles are formed using superfluid helium droplets as the nanoreactors, which are strongly ferromagnetic. The transition from antiferromagentism to ferromagnetism is attributed to atomic-scale disorder in chromium nanoparticles, leading to abundant unbalanced surface spins. Theoretical modeling confirms a frustrated aggregation process in superfluid helium due to the antiferromagnetic nature of chromium. © 2016 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Negative ions in liquid helium

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  6. Thermal resistance at a solid/superfluid helium interface

    NASA Astrophysics Data System (ADS)

    Ramiere, Aymeric; Volz, Sebastian; Amrit, Jay

    2016-05-01

    Kapitza in 1941 discovered that heat flowing across a solid in contact with superfluid helium (<2 K) encounters a strong thermal resistance at the interface. Khalatnikov demonstrated theoretically that this constitutes a general phenomenon related to all interfaces at all temperatures, given the dependence of heat transmission on the acoustic impedance (sound velocity × density) of each medium. For the solid/superfluid interface, the measured transmission of heat is almost one hundred times stronger than the Khalatnikov prediction. This discrepancy could be intuitively attributed to diffuse scattering of phonons at the interface but, despite several attempts, a detailed quantitative comparison between theoretical and experimental findings to explain the occurrence of scattering and its contribution to heat transmission had been lacking. Here we show that when the thermal wavelength λ of phonons of the less dense medium (liquid 4He) becomes comparable to the r.m.s. surface roughness σ, the heat flux crossing the interface is amplified; in particular when σ ~ 0.33λ, a spatial resonant mechanism occurs, as proposed by Adamenko and Fuks. We used a silicon single crystal whose surface roughness was controlled and characterized. The thermal boundary resistance measurements were performed from 0.4 to 2 K at different superfluid pressures ranging from saturated vapour pressure (SVP) to above 4He solidification, to eliminate all hypothetical artefact mechanisms. Our results demonstrate the physical conditions necessary for resonant phonon scattering to occur at all interfaces, and therefore constitute a benchmark in the design of nanoscale devices for heat monitoring.

  7. Microscopic dynamics of superfluid Helium confined in mesopores

    NASA Astrophysics Data System (ADS)

    Prisk, Timothy R.

    This dissertation reports an inelastic neutron scattering study of superfluid helium confined within FSM-16, a high surface area, porous silica glass. Its tubular pores are monodisperse, only a few nanometers in diameter, and ordered in a regular triangular lattice structure. The neutron scattering data clearly distinguishes between three different pore filling regimes. First, close to monolayer coverage, the adsorbed helium forms an amorphous, inert solid which neither displays superflow nor supports well-defined, low energy excitations. Second, when the adsorbed helium forms a thin fluid film approximately one atomic layer thick on top of the solid layer, it supports a dramatically modified phonon-roton spectrum as well as a compressed layer roton. The energies of these modified phonon-roton modes are consistent with those of a dilute, low-density film, one in which the average interatomic spacing is greater than the average interatomic spacing within the bulk liquid. These dilute layer modes correspond to the excitations of the bulk liquid under negative absolute pressure. Finally, when the pores are completely saturated with liquid, the modified phonon-roton spectrum disappears altogether. Instead, bulk-like modes coexist with the compressed layer mode. The qualitative difference between these three pore-filling regimes is reflected in their effective vibrational density of states.

  8. Superfluid helium-4 interferometers: construction and experiments

    NASA Astrophysics Data System (ADS)

    Joshi, Aditya Ajit

    This dissertation has two main goals: to highlight some new results in the field of superfluid 4He interferometry and to provide an in-depth, "hands-on" guide to the physics, design, construction, testing and operation of a continuously operating, fluxlocked 4 He dc-SHeQUID (Superfluid Helium Quantum Interference Device). Many of these topics haven't really been addressed in writing and the hapless new experimenter seeking to develop a SHeQUID is generally forced to reinvent the wheel rather than start at the frontier and push it forward. We would like to prevent that by making this a comprehensive guide to building and operating SHeQUIDs. We have optimized the fabrication of the nanoscale aperture arrays that are the very heart of the SHeQUID and resolved long-standing issues with their durability and long-term usability. A detailed report on this should assist in avoiding the many pitfalls that await those who fabricate and use these aperture arrays. We have constructed a new, modular SHeQUID that is designed to be easily adaptable to a wide array of proposed experiments without the necessity of rebuilding and reassembling key components like the displacement transducer. We have automated its working as a continuously operating, linearized (flux-locked) interferometer by using the so-called "chemical potential battery" in conjunction with a feedback system. We have also constructed a new reorientation system that is several orders of magnitude quieter than its predecessors. Together, these developments have allowed us to measure a changing rotation field in real time, a new development for this kind of device. We have also developed a module that allows control of the reorientation stage by automated data-taking software for investigating long-term drifts (by safely sweeping the stage back and forth). We have also investigated the chemical potential battery in further detail and report some fascinating nonlinear mode locking phenomena that have important

  9. Interaction of infrared light with impurity gels in superfluid helium

    NASA Astrophysics Data System (ADS)

    Izotov, A. N.; Efimov, V. B.

    2011-05-01

    Rapid cooling of an impurity-helium mixture into superfluid helium produces a distinctive soft matter—impurity-helium gel, clusters of which coagulate into nanoparticles. The sizes of the particles and their mutual interaction depend on the nature of the impurity atoms and the impurity-helium coupling. Here we describe the setup of and preliminary results from an experiment to study infrared absorption by a water-helium gel. Comparisons of the infrared absorption spectra of the gel and of water and ice suggests a peculiar interaction among water molecules in a water-helium gel.

  10. Decay of Finite Temperature Superfluid Helium-4 Turbulence

    NASA Astrophysics Data System (ADS)

    Kivotides, Demosthenes

    2015-10-01

    A mesoscopic model of superfluid helium-4, that describes the dynamics of individual topological defects of the ground state (superfluid vortices) and their (self-consistent) interactions with its quasi-particle excitations (normal-fluid), is solved numerically in order to analyse the physics of decaying homogeneous, isotropic turbulence. The calculations predict several temporal decay regimes not present in classical turbulence decay, the corresponding superfluid and normal-fluid energy spectra, and the experimentally observed scaling for the superfluid vortex line density at large times. The results demonstrate that the origin of this scaling is the energy spent by the superfluid in order to sustain a fluctuating low Reynolds number flow in the normal-fluid, and not the locking of turbulent superfluid and normal-fluid vorticities.

  11. Characterization of quantum vortex dynamics in superfluid helium

    NASA Astrophysics Data System (ADS)

    Meichle, David P.

    Liquid helium obtains superfluid properties when cooled below the Lambda transition temperature of 2.17 K. A superfluid, which is a partial Bose Einstein condensate, has many exotic properties including free flow without friction, and ballistic instead of diffusive heat transport. A superfluid is also uniquely characterized by the presence of quantized vortices, dynamical line-like topological phase defects around which all circulation in the flow is constrained. Two vortices can undergo a violent process called reconnection when they approach, cross, and retract having exchanged tails. With a numerical examination of a local, linearized solution near reconnection we discovered a dynamically unstable stationary solution to the Gross-Pitaevskii equation, which was relaxed to a fully non-linear solution using imaginary time propagation. This investigation explored vortex reconnection in the context of the changing topology of the order parameter, a complex field governing the superfluid dynamics at zero temperature. The dynamics of the vortices can be studied experimentally by dispersing tracer particles into a superfluid flow and recording their motions with movie cameras. The pioneering work of Bewley et al. provided the first visualization technique using frozen gases to create tracer particles. Using this technique, we experimentally observed for the first time the excitation of helical traveling waves on a vortex core called Kelvin waves. Kelvin waves are thought to be a central mechanism for dissipation in this inviscid fluid, as they provide an efficient cascade mechanism for transferring energy from large to microscopic length scales. We examined the Kelvin waves in detail, and compared their dynamics in fully self-similar non-dimensional coordinates to theoretical predictions. Additionally, two experimental advances are presented. A newly invented technique for reliably dispersing robust, nanometer-scale fluorescent tracer particles directly into the

  12. Catalysis of impurities coalescence by quantized vortices in superfluid helium with nanofilament formation

    NASA Astrophysics Data System (ADS)

    Gordon, E. B.; Okuda, Y.

    2009-03-01

    A dramatic effect of quantized vortices in superfluid helium on the rate of coalescence of suspended impurities has been predicted; such a catalytic process should result in the formation of fiber-like structures having primarily nanothickness. That should be valid for any impurity and it may be used as a basis for a universal method of producing nanowires and nanotubes. Experiments on the imbedding of molecular hydrogen into liquid helium have supported these conclusions. They showed that: (i) in normal liquid He the coalescence led to the formation of spherical microparticles carried by turbulent motion of the liquid; (ii) in the superfluid only very long filaments were observed, which behaved as quantized vortices should do. These filaments are fiber-like hydrogen crystals and survive the transition of the liquid helium to the normal state. The promises for using this phenomenon in basic and applied sciences are outlined.

  13. Superfluid helium cryogenic systems for superconducting RF cavities at KEK

    SciTech Connect

    Nakai, H.; Hara, K.; Honma, T.; Hosoyama, K.; Kojima, Y.; Nakanishi, K.; Kanekiyo, T.; Morita, S.

    2014-01-29

    Recent accelerator projects at KEK, such as the Superconducting RF Test Facility (STF) for R and D of the International Linear Collider (ILC) project and the compact Energy Recovery Linac (cERL), employ superconducting RF cavities made of pure niobium, which can generate high gradient acceleration field. Since the operation temperature of these cavities is selected to be 2 K, we have developed two 2 K superfluid helium cryogenic systems for stable operation of superconducting RF cavities for each of STF and cERL. These two 2 K superfluid helium cryogenic systems are identical in principle. Since the operation mode of the cavities is different for STF and cERL, i.e. the pulse mode for STF and the continuous wave mode for cERL, the heat loads from the cavities are quite different. The 2 K superfluid helium cryogenic systems mainly consists of ordinary helium liquefiers/refrigerators, 2 K refrigerator cold boxes, helium gas pumping systems and high-performance transfer lines. The 2 K refrigerators and the high-performance transfer lines are designed by KEK. Some superconducting RF cavity cryomodules have been already connected to the 2 K superfluid helium cryogenic systems for STF and cERL respectively, and cooled down to 2 K successfully.

  14. A quantitative experiment on the fountain effect in superfluid helium

    NASA Astrophysics Data System (ADS)

    Amigó, M. L.; Herrera, T.; Neñer, L.; Peralta Gavensky, L.; Turco, F.; Luzuriaga, J.

    2017-09-01

    Superfluid helium, a state of matter existing at low temperatures, shows many remarkable properties. One example is the so called fountain effect, where a heater can produce a jet of helium. This converts heat into mechanical motion; a machine with no moving parts, but working only below 2 K. Allen and Jones first demonstrated the effect in 1938, but their work was basically qualitative. We now present data of a quantitative version of the experiment. We have measured the heat supplied, the temperature and the height of the jet produced. We also develop equations, based on the two-fluid model of superfluid helium, that give a satisfactory fit to the data. The experiment has been performed by advanced undergraduate students in our home institution, and illustrates in a vivid way some of the striking properties of the superfluid state.

  15. Pressure dependent line shifts of atoms in superfluid helium

    NASA Astrophysics Data System (ADS)

    Putlitz, Gisbert Zu; Baumann, I.; Foerste, M.; Jungmann, K.; Tabbert, B.; Wiebe, J.; Zühlke, C.

    1998-05-01

    Defect atoms and ions in superfluid helium open the possibility to study the nature of the defect with respect to its environment. Depending on the electronic structure and charge of the foreign particles two forms of defects are built: so-called "bubbles" and "snowballs"(B. Tabbert, H. Günther and G. zu Putlitz, J. Low. Temp. Phys.) 109, 653 (1997). Defect ions are produced by laser sputtering, they can recombine with electrons from a field emission tip(I. Baumann, M. Foerste, K. Layer, G. zu Putlitz, B. Tabbert and C. Zühlke, J. Low. Temp. Phys.) 110, 213 (1998). The spectral lines observed are shifted and broadened compared to the free atomic transitions. The radius and the shape of the defect structure are supposed to be pressure dependent. Consequently we employ a pressure cell which allows for the spectroscopic measurements up to external pressures of 40 bar. Since liquid helium solidifies above 25 bar a study of the phase transition from the liquid to the solid can be made.

  16. The Creation of Long-Lived Multielectron Bubbles in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Fang, Jieping; Tempere, J.; Silvera, Isaac F.

    2017-04-01

    Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes. MEBs in liquid helium are predicted to have dynamic instabilities for zero or positive pressures, and stability for negative pressures. We report the production of long-lived MEBs in a novel cell filled with helium at static negative pressures. MEBs were extracted from the vapor sheath of a heated filament loop embedded in the superfluid helium and were observed by high-speed photography as they rose in the helium under buoyant forces. In earlier studies we found that MEBs created in this way had large amplitude oscillations and were unstable to decay. By creating MEBs at temperatures just under the lambda point, these oscillations are rapidly damped and the MEBs relax toward a spherical shape and stability as they rise in the helium.

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

    SciTech Connect

    Kivotides, Demosthenes

    2014-10-15

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

  18. Superfluid helium II as the QCD vacuum

    NASA Astrophysics Data System (ADS)

    Zhitnitsky, Ariel

    2017-03-01

    We study the winding number susceptibility in a superfluid system and the topological susceptibility in QCD. We argue that both correlation functions exhibit similar structures, including the generation of the contact terms. We discuss the nature of the contact term in superfluid system and argue that it has exactly the same origin as in QCD, and it is related to the long distance physics which cannot be associated with conventional microscopical degrees of freedom such as phonons and rotons. We emphasize that the conceptual similarities between superfluid system and QCD may lead, hopefully, to a deeper understanding of the topological features of a superfluid system as well as the QCD vacuum.

  19. Superfluid helium cryostat for the SIRTF cryogenic telescope assembly

    NASA Astrophysics Data System (ADS)

    Volz, Stephen M.; Schweickart, Russell B.; Heurich, Bruce

    2003-03-01

    The Space Infrared Telescope Facility (SIRTF) is the last of NASA's four great observatories, scheduled for launch in January 2003. At the heart of the SIRTF Observatory is the Cryogenic Telescope Assembly (CTA) that provides a 1.4 K heat sink for the SIRTF Science Instruments while cooling the telescope to as low as 5.5 K in order to achieve thea low photon background. This unique cryogenic/thermal system provides the necessary cooling through passive means combined with vapor cooling by the helium gas vented from a 360 liter superfluid helium cryostat. The passive cooling is made possible by the favorable thermal environment achieved in an Earth-trailing solar orbit, with the payload millions of miles from the Earth. The SIRTF Cryostat and integrated CTA have just completed an extended period of cryogenic system performance testing. This testing included mission lifetime assessment, luanch hold capability and in situ characterization and performance measurements of the porous plug liquid-vapor phase separator. We also encountered and recovered from an ice contamination incident within the cryostat. We report here the system and component test results. We also provide recommendations and lessons learned through the operations of the SIRTF system.

  20. Light dark matter in superfluid helium: Detection with multi-excitation production

    NASA Astrophysics Data System (ADS)

    Knapen, Simon; Lin, Tongyan; Zurek, Kathryn M.

    2017-03-01

    We examine in depth a recent proposal to utilize superfluid helium for direct detection of sub-MeV mass dark matter. For sub-keV recoil energies, nuclear scattering events in liquid helium primarily deposit energy into long-lived phonon and roton quasiparticle excitations. If the energy thresholds of the detector can be reduced to the meV scale, then dark matter as light as ˜MeV can be reached with ordinary nuclear recoils. If, on the other hand, two or more quasiparticle excitations are directly produced in the dark matter interaction, the kinematics of the scattering allows sensitivity to dark matter as light as ˜keV at the same energy resolution. We present in detail the theoretical framework for describing excitations in superfluid helium, using it to calculate the rate for the leading dark matter scattering interaction, where an off-shell phonon splits into two or more higher-momentum excitations. We validate our analytic results against the measured and simulated dynamic response of superfluid helium. Finally, we apply this formalism to the case of a kinetically mixed hidden photon in the superfluid, both with and without an external electric field to catalyze the processes.

  1. Positive ion extraction across the superfluid-vapor helium interface

    NASA Astrophysics Data System (ADS)

    Purushothaman, S.; Peräjärvi, K.; Ranjan, M.; Saastamoinen, A.; Gloos, K.; Takahashi, N.; Dendooven, P.

    2009-02-01

    The extraction efficiency of positive Rn ions across the superfluid-vapor helium interface above ~1.3 K indicates that extraction results from thermal activation across a barrier of about 20 K. Below ~1.3 K, the extraction efficiency is constant at about 0.7%. The evaporation of the superfluid surface by second sound pulses has a negative impact on the ion extraction, but not on the ions themselves. It takes 3.2(6) s at 1.60 K and 15(6) s at 1.15 K for the extraction process to recover from a disturbed state of yet unknown nature.

  2. Cold electrons in silicon and on superfluid helium

    NASA Astrophysics Data System (ADS)

    Bradbury, Forrest Riley

    Experiments presented herein are conducted in two material systems with the single motivation of understanding how to control quantum information. After introducing quantum information, we explain why these two material systems, donor electron spins in silicon and electron spins on the surface of superfluid helium, are strong candidates to become viable qubits, the building blocks of quantum information processing. Our experiments probe the relevant physical structure and demonstrate new techniques for qubit state control. We measure the Stark shift of 121Sb donor electron spins in silicon using pulsed electron spin resonance at 0.35 T. Interdigitated metal gates on top of an Sb-implanted 28Si epi-layer apply electric fields at donor sites. Two quadratic Stark effects are resolved: a decrease of the hyperfine coupling between electron and nuclear spins of the donor and a decrease in electron Zeeman g-factor. The hyperfine term prevails at our X-band magnetic fields of 0.35T, while the g-factor term is expected to dominate at higher magnetic fields. A significant linear Stark effect is also observed, which we suggest arises from strain. We discuss the results in the context of the Kane model quantum computer, confirming that Stark tuning is a convenient way to change the spin resonance energy of individual electrons, and thus provide addressability using electrostatic gates. We also measure the transport of surface electrons on liquid helium at 1.5K using micro-fabricated channel devices. The channels, which are filled with superfluid 4He by capillary action, have small underlying metal gates for electron control and detection. Initial studies with simple self-fabricated devices inspired the use of silicon devices for advantages in complexity and advanced processing capabilities. Our silicon device has 120 parallel channels and an intersecting perpendicular channel with 3 microm and 2.5 microm widths, respectively. Connected as in a 3-phase charge coupled device

  3. Verification testing of the superfluid helium on-orbit transfer (SHOOT) experiment

    NASA Astrophysics Data System (ADS)

    Volz, S.; Conaty, C.; Weintz, K.

    The Superfluid Helium On-Orbit Transfer (SHOOT) project is a secondary shuttle crossbay payload which flew on the STS-57/Endeavour mission. It was designed to develop and demonstrate the technologies required to resupply liquid helium containers in space, and to develop new technologies that may be used in other future space cryogenic systems. The SHOOT payload consists of two superfluid helium Dewars with helium management cryostats connected by a transfer line, and six avionics boxes for valve and heater control, temperature, pressure and fluid position monitoring and data processing and telemetry. The cryostats contain numerous specialized helium management components; including high and low flow phase separators, liquid/vapour discriminators, flowmeters, liquid level detectors, cryogenic mechanical valves and cryogenic relief valves and burst discs, and two varieties of fluid acquisition systems. To prepare the SHOOT payload for launch a series of functional, structural, thermal and reliability tests were conducted at every level of hardware assembly, from materials tests to system level thermal, structural and functional performance tests. We present here the verification tests and analyses developed and completed at each level of assembly. We discuss the trade-offs considered for, and the success (or failure) of, models and analyses to predict performance results. Finally, we present some lessons learned of potential interest to future cryogenic missions, whether on the Space Shuttle or on expendable launch vehicles.

  4. Pressure drop in the SHOOT superfluid helium acquisition system. [Superfluid Helium On-Orbit Transfer system

    NASA Technical Reports Server (NTRS)

    Nissen, J. A.; Maytal, B.; Van Sciver, S. W.

    1990-01-01

    Central to the upcoming Superfield Helium On-Orbit Transfer (SHOOT) demonstration is the fluid acquisition system. The main component of the system is a rectangular cross-section gallery area with one side fabricated from a fine mesh screen. He II enters through the screen and is delivered to a fountain effect pump. A model is proposed to predict the pressure drop as fluid flows through the screen and an expression is derived for the required gallery arm length as a function of flow rate demand. The model is compared with measurement of pressure drop in a full scale SHOOT gallery arm operated with flow rates of up to 850 cu dm/hr. The tests were conducted in the University of Wisconsin horizontal liquid helium flow facility to minimize gravitational effects.

  5. Defects in novel superfluids: Supersolid helium and cold gases

    NASA Astrophysics Data System (ADS)

    Dasbiswas, Kinjal

    We investigate the role played by various topological defects, especially crystal dislocations and superfluid vortices, in some novel superfluids - such as the putative supersolid phase in solid helium-4 (4He) and in dilute Bose-Einstein condensates (BEC) in traps. The first part of this work addresses recent experimental findings in solid helium, such as the period shift in resonant oscillators that has been interpreted to be a signature of superfluidity coexisting with crystalline order in solid helium. We use Landau's phenomenological theory for phase transitions to establish that crystal defects such as dislocation lines and grain boundaries can induce local superfluid order and show that a network of dislocation lines can give rise to bulk superfluid order within a crystal. Our findings are also relevant to other phase transitions in the presence of crystal defects. The second part concerns the stability and dynamics of a single vortex in a rotating trap of a Bose-Einstein condensate (BEC) and the possibility of the macroscopic quantum tunneling of such a vortex from a metastable minimum at the trap center. The complete dynamics of such a vortex is derived by integrating out the phonon modes from a hydrodynamic action, and estimates for the tunneling rate are obtained using a variety of semiclassical methods. This is analogous to the problem of tunneling of a charged particle through a potential barrier in the presence of a very high magnetic field, the Magnus force on the vortex being analogous to the Lorentz force on a charge. We conclude that the vortex action has a complicated nonlocal form and further, that the Magnus-dominated dynamics of the vortex tends to suppress tunneling.

  6. Laser cooling and control of excitations in superfluid helium

    NASA Astrophysics Data System (ADS)

    Harris, G. I.; McAuslan, D. L.; Sheridan, E.; Sachkou, Y.; Baker, C.; Bowen, W. P.

    2016-08-01

    Superfluidity is a quantum state of matter that exists macroscopically in helium at low temperatures. The elementary excitations in superfluid helium have been probed with great success using techniques such as neutron and light scattering. However, measurements of phonon excitations have so far been limited to average thermodynamic properties or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of phonon excitations in real time. Furthermore, strong light-matter interactions allow both laser cooling and amplification. This represents a new tool to observe and control superfluid excitations that may provide insight into phonon-phonon interactions, quantized vortices and two-dimensional phenomena such as the Berezinskii-Kosterlitz-Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including the prospect of femtogram masses, high mechanical quality factors, strong phonon-phonon and phonon-vortex interactions, and self-assembly into complex geometries with sub-nanometre feature size.

  7. Communication: Electron diffraction of ferrocene in superfluid helium droplets

    PubMed Central

    2016-01-01

    We report electron diffraction of ferrocene doped in superfluid helium droplets. By taking advantage of the velocity slip in our pulsed droplet beam using a pulsed electron gun, and by doping with a high concentration of ferrocene delivered via a pulsed valve, we can obtain high quality diffraction images from singly doped droplets. Under the optimal doping conditions, 80% of the droplets sampled in the electron beam are doped with just one ferrocene molecule. Extension of this size selection method to dopant clusters has also been demonstrated. However, incomplete separation of dopant clusters might require deconvolution and modeling of the doping process. This method can be used for studies of nucleation processes in superfluid helium droplets. PMID:27305988

  8. Noncavitating Pump For Liquid Helium

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  9. Detectability of Light Dark Matter with Superfluid Helium.

    PubMed

    Schutz, Katelin; Zurek, Kathryn M

    2016-09-16

    We show that a two-excitation process in superfluid helium, combined with sensitivity to meV energy depositions, can probe dark matter down to the ∼keV warm dark matter mass limit. This mass reach is 3 orders of magnitude below what can be probed with ordinary nuclear recoils in helium at the same energy resolution. For dark matter lighter than ∼100  keV, the kinematics of the process requires the two athermal excitations to have nearly equal and opposite momentum, potentially providing a built-in coincidence mechanism for controlling backgrounds.

  10. A thermodynamic model to predict electron mobility in superfluid helium.

    PubMed

    Aitken, Frédéric; Volino, Ferdinand; Mendoza-Luna, Luis Guillermo; Haeften, Klaus von; Eloranta, Jussi

    2017-06-21

    Electron mobility in superfluid helium is modeled between 0.1 and 2.2 K by a van der Waals-type thermodynamic equation of state, which relates the free volume of solvated electrons to temperature, density, and phase dependent internal pressure. The model is first calibrated against known electron mobility reference data along the saturated vapor pressure line and then validated to reproduce the existing mobility literature values as a function of pressure and temperature with at least 10% accuracy. Four different electron mobility regimes are identified: (1) Landau critical velocity limit (T ≈ 0), (2) mobility limited by thermal phonons (T < 0.6 K), (3) thermal phonon and discrete roton scattering ("roton gas") limited mobility (0.6 K < T < 1.2 K), and (4) the viscous liquid ("roton continuum") limit (T > 1.2 K) where the ion solvation structure directly determines the mobility. In the latter regime, the Stokes equation can be used to estimate the hydrodynamic radius of the solvated electron based on its mobility and fluid viscosity. To account for the non-continuum behavior appearing below 1.2 K, the temperature and density dependent Millikan-Cunningham factor is introduced. The hydrodynamic electron bubble radii predicted by the present model appear generally larger than the solvation cavity interface barycenter values obtained from density functional theory (DFT) calculations. Based on the classical Stokes law, this difference can arise from the variation of viscosity and flow characteristics around the electron. The calculated DFT liquid density profiles show distinct oscillations at the vacuum/liquid interface, which increase the interface rigidity.

  11. Using polycrystalline bismuth filter in an ultracold neutron source with superfluid helium

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Lyamkin, V. A.; Runov, V. V.; Ivanov, S. A.; Onegin, M. S.; Fomin, A. K.

    2015-10-01

    Placing polycrystalline bismuth filter in front of an ultracold neutron (UCN) source with superfluid helium at 1 K is shown to be effective. The use of this filter ensures a 30-fold decrease (down to 0.5 W) in the level of heat load in the UCN source, while reducing by 30% the flux of neutrons with 9-Å wavelength (which are converted into UCNs). The phenomenon of small-angle scattering on polycrystalline bismuth has been studied and shown to be insignificant. Cooling of the filter to liquid nitrogen temperature increases the transmission of 9-Å neutrons by only 8%; hence, creation of this cooling system is inexpedient. A project of a technological complex designed for the UCN source at the PIK reactor is presented, which ensures the removal of 1-W heat load from the UCN source with superfluid helium at a 1-K temperature level.

  12. Extraction of radioactive positive ions across the surface of superfluid helium: A new method to produce cold radioactive nuclear beams

    NASA Astrophysics Data System (ADS)

    Huang, W. X.; Dendooven, P.; Gloos, K.; Takahashi, N.; Pekola, J. P.; Äystö, J.

    2003-09-01

    Alpha-decay recoils 219Rn were stopped in superfluid helium and positive ions were extracted by electric field into the vapour phase. This first quantitative observation of extraction was successfully conducted using highly sensitive radioactivity detection. The efficiency for extraction across the liquid surface was 23 ± 4% at 1.60 K, the release time was 90 ± 10 ms at 1.50 K and the barrier for positive ions through a free superfluid-helium surface was 19.4 ± 4.5 K. The pulsed second sound proved to be effective in enhancing the extraction.

  13. Superfluid helium orbital resupply - The status of the SHOOT flight experiment and preliminary user requirements. [Superfluid Helium On-Orbit Transfer

    NASA Technical Reports Server (NTRS)

    Dipirro, Michael J.; Kittel, Peter

    1989-01-01

    The Superfluid Helium On-Orbit Transfer (SHOOT) flight experiment is designed to demonstrate the components and techniques necessary to resupply superfluid helium to satellites or Space Station based facilities. A top level description as well as the development status of the critical components to be used in SHOOT are discussed. Some of these components include the thermomechanical pump, the fluid acquisition system, the normal helium and superfluid helium phase separators, Venturi flow meter, cryogenic valves, burst disks, and astronaut-compatible EVA coupler and transfer line. The requirements for the control electronics and software are given. A preliminary description of the requirements that must be met by a satellite requiring superfluid helium servicing is given. In particular, minimum and optimum plumbing arrangements are shown, transfer line flow impedance and heat input impacts are assessed, instrumentation is described, and performance parameters are considered.

  14. Glass-to-Metal Seal Against Liquid Helium

    NASA Technical Reports Server (NTRS)

    Watkins, John L.; Gatewood, John R.

    1987-01-01

    Simple compression joint with indium gasket forms demountable seal for superfluids. Seal developed for metal lid on glass jar used in experiments on liquid helium. Glass container allows contents to be viewed for such purposes as calibration of liquid-level detectors and adjustments of displacement plungers. Seal contains liquid helium even when temperature drops below 2.19K. Made from inexpensive, commercially available materials and parts.

  15. Photochemistry of 3-hydroxyflavone inside superfluid helium nanodroplets

    SciTech Connect

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

    2009-11-21

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

  16. Performance of all-metal demountable cryogenic seals at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Kittel, Peter; Spivak, Alan L.

    1989-01-01

    Two all-metal demountable cryogenic seals with an outside diameter of 36.6 mm, inside diameter of 27.2 mm, and thickness of 0.51 mm were leak-tested at room temperature (300 K), liquid nitrogen temperature (21 cycles at 77 K), liquid helium temperature (9 cycles at 4.2 K), and superfluid helium temperature (4 cycles at 1.6 K). Each seal was mounted and demounted for 13 cycles. Thickness measurements at 90 deg intervals along the circumference showed a maximum seal compression of 0.038 mm. Leak-rate measurements at all temperatures showed no detectable leak above the helium background level, typically 0.1 x 10(-9) std-cc/sec, during testing.

  17. Performance of all-metal demountable cryogenic seals at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, L. J.; Kittel, P. L.; Spivak, A. L.

    1991-01-01

    Two all-metal demountable cryogenic seals with an outside diameter of 36.6 mm, inside diameter of 27.2 mm and thickness of 0.51 mm were leak-tested at room temperature (300 K), liquid nitrogen temperature (21 cycles at 77 K), liquid helium temperature (nine cycles at 4.2K) and superfluid helium temperature (four cycles at 1.6 K). Each seal was mounted and demounted for 13 cycles. Thickness measurements at 90 deg intervals along the circumference showed a maximum seal compression of 0.038 mm. Leak rate measurements at all temperatures showed no detectable leak above the helium background level, typically 0.1 x 10 exp -9 std cu cm/s, during testing.

  18. Helium, from He3 Superfluid to Alpha-spin

    NASA Astrophysics Data System (ADS)

    Hidajatullah-Widastra, Fatahillah; Hidajatullah-Maksoed, Widastra

    2015-04-01

    Accompanying helium-using of ``Two Eagles'' balloon group 2015 World record pacificballoon.com@Flight-Status.php, superfluid He3 offers a unique ``testing ground'' for rapid phase transitions. Recent experiments where a rotating superfluid He3 was locally heated well above the critical temperature by absorption of neutrons [4,5] receved vortex formation under a rapid 2nd order phase transition-I.S. Aranson, et al., Physica C, ``Vortex Matter in Superconductors at Extreme SCALES and Conditions'', v 332, n 1-4, May 2000, h 129. Further for ``alpha-spin resembles the vortex formed as a consequence of the interaction of 4 vortexes'' sought the ``it will be sufficient to calculate the energy shift with the singlet & triplet m = 0-S Gasiorowics: ``Quantum Physics'',2003, h 220 Great acknowledgements to HE. Mr. Drs. P. SWANTORO/Kompas-Gramedia Group.

  19. Probing the A-B interface of superfluid helium-3

    NASA Astrophysics Data System (ADS)

    Haley, Richard

    2015-03-01

    At temperatures around 1 mK helium-3 forms a BCS spin triplet condensate. The order parameter is sufficiently complex that more than one superfluid phase exists, each exhibiting a different broken symmetry, and there is a model first order transition between the two most stable phases, labeled A and B. The Lancaster Ultra-Low Temperature Group has developed techniques to probe the properties of the A-B interface in the deep sub-mK regime where the superfluid is in the pure condensate limit. Shaped and controllable magnetic fields are used to induce the transition, and to stabilize and move the A-B phase boundary inside the experimental volume. The latent heat of the transition has been measured, and the nucleation behavior shown to be incompatible with conventional thermodynamic models. Since superfluid helium-3 is inherently pure, and the order parameter transforms continuously across the A-B interface, it is the most coherent two-dimensional structure to which we have experimental access. It has been proposed that this 2D surface in the surrounding 3D bulk volume is a good analog of a cosmological brane separating two distinct quantum vacuum states; experiments that simulate brane annihilation and the creation of topological defects have been carried out at Lancaster. Other investigations have included measurements of the surface tension and wetting behavior of the interface. During these studies it was discovered that a large, unpredicted frictional force was acting on the interface even though it is moving through a pure superfluid. Recent breakthrough work on the dynamics of the A-B interface has finally solved this puzzle. Current experiments include a setup where the interface region is probed directly using quartz tuning fork resonators that couple to the local density of broken Cooper pair quasiparticle excitations and thus give insight into the order parameter energy gap structure as A transforms to B.

  20. Formation of Au and tetrapyridyl porphyrin complexes in superfluid helium.

    PubMed

    Feng, Cheng; Latimer, Elspeth; Spence, Daniel; Al Hindawi, Aula M A A; Bullen, Shem; Boatwright, Adrian; Ellis, Andrew M; Yang, Shengfu

    2015-07-14

    Binary clusters containing a large organic molecule and metal atoms have been formed by the co-addition of 5,10,15,20-tetra(4-pyridyl)porphyrin (H2TPyP) molecules and gold atoms to superfluid helium nanodroplets, and the resulting complexes were then investigated by electron impact mass spectrometry. In addition to the parent ion H2TPyP yields fragments mainly from pyrrole, pyridine and methylpyridine ions because of the stability of their ring structures. When Au is co-added to the droplets the mass spectra are dominated by H2TPyP fragment ions with one or more Au atoms attached. We also show that by switching the order in which Au and H2TPyP are added to the helium droplets, different types of H2TPyP-Au complexes are clearly evident from the mass spectra. This study suggests a new route for the control over the growth of metal-organic compounds inside superfluid helium nanodroplets.

  1. Liquid Helium 3 and Solid Helium at Yale and Beyond

    NASA Astrophysics Data System (ADS)

    Lee, D. M.

    2006-03-01

    Many of the foundations of low temperature physics in the latter half of the twentieth century were built at Yale University under the leadership of Professor Cecil T. Lane who came to Yale in 1932 and Henry A. Fairbank who obtained his Ph.D. at Yale in 1944 under Lane's guidance. This discussion will mainly treat the contributions of Henry Fairbank and his students during the period between 1954 and 1963, when Henry Fairbank left Yale to become chairman of the Physics Dept. at Duke University. Following World War II small amounts of helium three became available to low temperature experimenters. Henry Fairbank’s graduate students were provided with the opportunity to investigate second sound in dilute and later concentrated mixtures of helium three in superfluid helium four. These measurements showed strong effects of the phase separation in helium 3 - helium 4 mixtures previously discovered in the laboratory of William Fairbank (a student of Lane and a brother of Henry Fairbank). As more helium three became available, studies of pure helium three were performed, including measurements of the thermal conductivity, the density and the specific heat. Early evidence for the melting curve minimum was found. The main emphasis in this work was to search for Fermi liquid behavior. Much of the later work in this area was performed by the group of John Wheatley at the University of Illinois. In studies of solid helium four at Yale, a surprising observation was made. Hitherto it had been thought that hcp was the stable phase throughout the low temperature part of the phase diagram. It was found via ultrasound experiments that a small silver of bcc solid existed at the lowest pressures. While this author was a graduate student at Yale, Henry Fairbank pointed out to him the possibility of cooling helium three via adiabatic compression from the liquid into the solid phase. (Pomeranchuk Cooling). A brief discussion is given of the use of this technique in the discovery of

  2. Turbulent Flow Around an Oscillating Body in Superfluid Helium: Dissipation Characteristics of the Nonlinear Regime

    NASA Astrophysics Data System (ADS)

    Zemma, E.; Luzuriaga, J.

    2013-08-01

    By examining the resonance curves of an oscillator submerged in superfluid liquid helium, it is found that their shape is affected by two distinct dissipation regimes when the amplitude is large enough to generate turbulence in the liquid. In a resonance curve, the central part close to resonance, may be in a turbulent regime, but the response is of much lower amplitude away from the resonance frequency, so that the oscillation can still be in the linear regime for frequencies not exactly at resonance. This introduces an ambiguity in estimating the inverse quality factor Q -1 of the oscillator. By analyzing experimental data we consider a way of matching the two ways of estimating Q -1 and use the information to evaluate the frictional force as a function of velocity in a silicon paddle oscillator generating turbulence in the superfluid.

  3. Influence of Quantum Turbulence on the Processes of Heat Transfer and Boiling in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Kondaurova, Luiza; Efimov, Victor; Tsoi, Alexey

    2017-04-01

    We demonstrate that in a wide range of heat fluxes the dynamics of heat transfer in superfluid helium is determined by the existence of remanent quantized vortices. The vortex density dynamics determines the rise of temperature near the heater and the boiling-up of superfluid helium. It permits to understand the results of the experiments of several groups.

  4. The Hydraulic Jump in Liquid Helium

    SciTech Connect

    Rolley, Etienne; Guthmann, Claude; Chevallier, Christophe; Pettersen, Michael S.

    2006-09-07

    We present the results of some experiments on the circular hydraulic jump in normal and superfluid liquid helium. The radius of the jump and the depth of the liquid outside the jump are measured through optical means. Although the scale of the apparatus is rather small, the location of the jump is found to be consistent with the assumption that the jump can be treated as a shock, if the surface tension is taken into account. The radius of the jump does not change when going down in temperature through the lambda point; we think that the flow is supercritical. A remarkable feature of the experiment is the observation of stationary ripples within the jump when the liquid is superfluid.

  5. Effective Mass of an Electron Bubble in Superfluid Helium-4

    NASA Astrophysics Data System (ADS)

    Huang, Yunhu; Maris, Humphrey J.

    2017-02-01

    We present the results of computer simulations of the motion of an electron bubble through superfluid helium-4 when acted upon by an electric field. The simulations are based on an extended version of the Gross-Pitaevskii equation. The temperature is assumed to be sufficiently low for the drag exerted on the bubble by thermal excitations to be negligible, and the calculations are made for velocities below the critical velocitie for nucleation of vortices and roton production. We calculate the effective mass m* of the bubble and obtain results in excellent agreement with the measurements of Poitrenaud and Williams, and Ellis, McClintock, and Bowley.

  6. Mechanical pumps for superfluid helium transfer in space

    NASA Technical Reports Server (NTRS)

    Izenson, M. G.; Swift, W. L.

    1988-01-01

    Two alternate mechanical pump concepts have been identified for the transfer of superfluid helium in space. Both pumps provide flow at sufficient head and have operating characteristics suitable for the Space Infrared Telescope Facility (SIRTF) refill mission. One pump operates at a relatively low speed and utilizes mechanical roller bearings, while the other operates at a higher rotational speed using either electromagnetic or tilting pad gas-dynamic bearings. The use of gas bearings requires transfer of normal helium so that the gas pressure within the pump casing is high enough to operate the bearings. The operating characteristics of both pumps are predicted, the dimensions are estimated and major technology issues are identified. The major issues for each pump design are cavitation performance and bearing development. Roller bearings require quantified reliability for operation in space while electromagnetic bearings require basic development as well as a complex control system. The low speed pump has significantly poorer hydraulic efficiency than the high speed pump.

  7. Mechanical pumps for superfluid helium transfer in space

    NASA Technical Reports Server (NTRS)

    Izenson, M. G.; Swift, W. L.

    1988-01-01

    Two alternate mechanical pump concepts have been identified for the transfer of superfluid helium in space. Both pumps provide flow at sufficient head and have operating characteristics suitable for the Space Infrared Telescope Facility (SIRTF) refill mission. One pump operates at a relatively low speed and utilizes mechanical roller bearings, while the other operates at a higher rotational speed using either electromagnetic or tilting pad gas-dynamic bearings. The use of gas bearings requires transfer of normal helium so that the gas pressure within the pump casing is high enough to operate the bearings. The operating characteristics of both pumps are predicted, the dimensions are estimated and major technology issues are identified. The major issues for each pump design are cavitation performance and bearing development. Roller bearings require quantified reliability for operation in space while electromagnetic bearings require basic development as well as a complex control system. The low speed pump has significantly poorer hydraulic efficiency than the high speed pump.

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

    SciTech Connect

    Pentlehner, D.; Slenczka, A.

    2015-01-07

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

  9. An Ultracold Neutron Source using Superfluid Helium at TRIUMF

    NASA Astrophysics Data System (ADS)

    Matsumiya, Ryohei; Kawasaki, Shinsuke; Canada-Japan UCN Collaboration Collaboration

    2016-09-01

    An Ultracold Neutrons (UCN) are an extremely slow neutrons with a kinetic energy in the order of 100 neV. As a consequence, UCNs are totally reflected at surface of certain materials and can be confined in a material bottle. Using this unique property, UCNs are used for various experiments such as neutron electric dipole moment searches, neutron lifetime measurements, gravity experiments, and other. A UCN source has been developed at the Research Center for Nuclear Physics (RCNP), in Osaka Japan. The UCN source is composed of a combination of a spallation neutron source and a superfluid helium UCN converter. Spallation neutrons are thermalized first by warm and cold D2O moderators. After that they give their kinetic energy to a phonon (single- phonon excitation) or phonons (multi-phonon excitation) in superfluid helium to result in UCNs. The UCN source achieved 26 UCN/cm3 at 1 μA proton current at RCNP. Now, the source is adapted to a new, dedicated proton beam line at TRIUMF for use at higher proton beam currents up to 40 μA. The developments at RCNP and future prospects at TRIUMF will be discussed.

  10. Discharge characteristics in liquid helium, liquid nitrogen and pure water preparatory to fabrication of carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Kawasaki, Hiroharu; Shigematsu, Toshinobu; Imasaka, Kiminobu; Ohshima, Tamiko; Yagyu, Yoshihito; Suda, Yoshiaki

    2012-12-01

    Discharge characteristics and emission spectra of the discharges in low-temperature liquid such as liquid helium have been measured to investigate the conditions for fabrication of carbon nanomaterial by arc discharge in low-temperature liquid. Measurements of the discharge characteristics of the resulting plasma and observation of the associated optical emission spectra show that the behaviour of discharge current over time and the associated spectra depend strongly on discharge voltage and both may be related to the temperature of the carbon target. However, discharge voltage and current with time are almost the same regardless of whether the liquid is pure water, liquid nitrogen, liquid helium and superfluid liquid helium

  11. Helium mass flow through a solid-superfluid-solid junction.

    PubMed

    Cheng, Zhi Gang; Beamish, John; Fefferman, Andrew D; Souris, Fabien; Balibar, Sébastien; Dauvois, Vincent

    2015-04-24

    We report the results of flow experiments in which two chambers containing solid ^{4}He are connected by a superfluid Vycor channel. At low temperatures and pressures, mechanically squeezing the solid in one chamber produced a pressure increase in the second chamber, a measure of mass transport through our solid-superfluid-solid junction. This pressure response is very similar to the flow seen in recent experiments at the University of Massachusetts: it began around 600 mK, increased as the temperature was reduced, then decreased dramatically at a temperature, T_{d}, which depended on the ^{3}He impurity concentration. Our experiments indicate that the flow is limited by mass transfer across the solid-liquid interface near the Vycor ends, where the ^{3}He collects at low temperature, rather than by flow paths within the solid ^{4}He.

  12. Thermal performance of a five year lifetime superfluid helium dewar for SIRTF

    NASA Technical Reports Server (NTRS)

    Lee, J. H.

    1990-01-01

    The Space Infrared Telescope Facility (SIRTF) is a 1 m class cryogenically cooled observatory for infrared astronomy. The SIRTF cryogenic system has to satisfy the five year mission lifetime requirement as well as to provide sufficient cooling for the science instruments and optical system. A 4000 cu dm superfluid helium dewar has been selected for the current baseline cryogenic system which represents the largest superfluid helium dewar proposed to date for a long lifetime space-borne application. This paper discusses the design and predicted performance of the current cryogenic system, as well as its comparison with IRAS and other space-borne superfluid helium dewars currently under development.

  13. Analysis of dewar and transfer line cooldown in Superfluid Helium On-Orbit Transfer Flight Experiment (SHOOT)

    NASA Technical Reports Server (NTRS)

    Ng, Y. S.; Lee, J. H.

    1989-01-01

    The Superfluid Helium On-Orbit Transfer Flight Experiment (SHOOT) is designed to demonstrate the techniques and components required for orbital superfluid (He II) replenishment of observatories and satellites. One of the tasks planned in the experiment is to cool a warm cryogen tank and a warm transfer line to liquid helium temperature. A math model, based on single-phase vapor flow heat transfer, has been developed to predict the cooldown time, component temperature histories, and helium consumption rate, for various initial conditions of the components and for the thermomechanical pump heater powers of 2 W and 0.5 W. This paper discusses the model and the analytical results, which can be used for planning the experiment operations and determining the pump heater power required for the cooldown operation.

  14. Analysis of dewar and transfer line cooldown in Superfluid Helium On-Orbit Transfer Flight Experiment (SHOOT)

    NASA Technical Reports Server (NTRS)

    Ng, Y. S.; Lee, J. H.

    1989-01-01

    The Superfluid Helium On-Orbit Transfer Flight Experiment (SHOOT) is designed to demonstrate the techniques and components required for orbital superfluid (He II) replenishment of observatories and satellites. One of the tasks planned in the experiment is to cool a warm cryogen tank and a warm transfer line to liquid helium temperature. A math model, based on single-phase vapor flow heat transfer, has been developed to predict the cooldown time, component temperature histories, and helium consumption rate, for various initial conditions of the components and for the thermomechanical pump heater powers of 2 W and 0.5 W. This paper discusses the model and the analytical results, which can be used for planning the experiment operations and determining the pump heater power required for the cooldown operation.

  15. Effective doping of low energy ions into superfluid helium droplets

    PubMed Central

    Zhang, Jie; Chen, Lei; Freund, William M.; Kong, Wei

    2015-01-01

    We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 104 ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 105/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies. PMID:26298127

  16. Visualization of two-fluid flows of superfluid helium-4

    PubMed Central

    Guo, Wei; La Mantia, Marco; Lathrop, Daniel P.; Van Sciver, Steven W.

    2014-01-01

    Cryogenic flow visualization techniques have been proved in recent years to be a very powerful experimental method to study superfluid turbulence. Micron-sized solid particles and metastable helium molecules are specifically being used to investigate in detail the dynamics of quantum flows. These studies belong to a well-established, interdisciplinary line of inquiry that focuses on the deeper understanding of turbulence, one of the open problem of modern physics, relevant to many research fields, ranging from fluid mechanics to cosmology. Progress made to date is discussed, to highlight its relevance to a wider scientific community, and future directions are outlined. The latter include, e.g., detailed studies of normal-fluid turbulence, dissipative mechanisms, and unsteady/oscillatory flows. PMID:24704871

  17. Effective doping of low energy ions into superfluid helium droplets.

    PubMed

    Zhang, Jie; Chen, Lei; Freund, William M; Kong, Wei

    2015-08-21

    We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10(4) ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10(5)/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.

  18. Effective doping of low energy ions into superfluid helium droplets

    SciTech Connect

    Zhang, Jie; Chen, Lei; Freund, William M.; Kong, Wei

    2015-08-21

    We report a facile method of doping cations from an electrospray ionization (ESI) source into superfluid helium droplets. By decelerating and stopping the ion pulse of reserpine and substance P from an ESI source in the path of the droplet beam, about 10{sup 4} ion-doped droplets (one ion per droplet) can be recorded, corresponding to a pickup efficiency of nearly 1 out of 1000 ions. We attribute the success of this simple approach to the long residence time of the cations in the droplet beam. The resulting size of the doped droplets, on the order of 10{sup 5}/droplet, is measured using deflection and retardation methods. Our method does not require an ion trap in the doping region, which significantly simplifies the experimental setup and procedure for future spectroscopic and diffraction studies.

  19. Transient heat transfer in superfluid helium. Part II

    SciTech Connect

    Dresner, L.

    1983-01-01

    Three classical problems associated with the ordinary diffusion equation concern the temperature in: (1) a half-space with clamped heat flux at the free face, (2) a half-space with clamped temperature at the free face, and (3) an infinite medium with a pulsed plane heat source. These problems are also important for the nonlinear diffusion equation based on the Gorter-Mellink relation, which describes heat transport in superfluid helium. A similarity solution to problem (1), the clamped-flux problem, has already been found and compared, with good agreement, with experimental data of van Sciver. (A similarity solution is one in which the profiles of temperature rise ..delta..T versus distance Z at different times t can be obtained from one another by suitable (different) stretching of the temperature and distance axes.) In this paper, similarity solutions are given in analytic form to problems (2) and (3), the clamped-temperature and pulsed-source problems.

  20. New calorimetric AC loss measurement technique involving superfluid helium

    SciTech Connect

    Baudouy, B.J.P.; Bartholomew, K.; Van Sciver, S.W.

    1996-12-31

    The authors have developed a new calorimetric AC loss measurement facility involving superfluid helium (He II). At present, the Test of AC Loss (TACL) facility performs AC loss measurements on Cable-in-Conduit Conductors (CICC) under development for the NHMFL 45 Tesla hybrid superconducting outsert magnet. TACL can handle large scale conductors up to one meter in length. Measurements utilize the exceptional high heat conductivity of He II, which provides an isothermal environment and is the dominant enthalpy in the system. The test conductors are placed in an independent cryostat containing He II which is inserted in a superconducting dipole magnet producing a transverse magnetic field up to 7 T. For a change of the magnetic field and associated AC loss, the temperature variation of the He II surrounding the conductor is measured and directly converted to enthalpy variation of the He II. This paper describes the measurement technique and compares its resolution to that of more conventional calorimetric AC loss measurements.

  1. Transient heat transfer in superfluid helium, part 2

    NASA Astrophysics Data System (ADS)

    Dresner, L.

    Three classical problems associated with the ordinary diffusion equation concern the temperature in: (1) a half-space with clamped heat flux at the free face; (2) a half-space with clamped temperature at the free face; and (3) an infinite medium with a pulsed plane heat source. These problems are also important for the nonlinear diffusion equation based on the Gorter-Mellink relation, which describes heat transport in superfluid helium. A similarity solution to problem (1), the clamped-flux problem, was found and compared, with good agreement, with experimental data of van Sciver. (A similarity solution is one in which the profiles of temperataure rise (RADICAL)T versus distance Z at different times t can be obtained from one another by suitable (different) stretching of the temperature and distance axes.) Similarity solutions are given in analytic form to problems (2) and (3), the clamped-temperature and pulsed-source problems.

  2. Visualization of two-fluid flows of superfluid helium-4.

    PubMed

    Guo, Wei; La Mantia, Marco; Lathrop, Daniel P; Van Sciver, Steven W

    2014-03-25

    Cryogenic flow visualization techniques have been proved in recent years to be a very powerful experimental method to study superfluid turbulence. Micron-sized solid particles and metastable helium molecules are specifically being used to investigate in detail the dynamics of quantum flows. These studies belong to a well-established, interdisciplinary line of inquiry that focuses on the deeper understanding of turbulence, one of the open problem of modern physics, relevant to many research fields, ranging from fluid mechanics to cosmology. Progress made to date is discussed, to highlight its relevance to a wider scientific community, and future directions are outlined. The latter include, e.g., detailed studies of normal-fluid turbulence, dissipative mechanisms, and unsteady/oscillatory flows.

  3. Stability measurements on cored cables in normal and superfluid helium

    SciTech Connect

    Ghosh, A.K.; Sampson, W.B.; Kim, S.W.; Leroy, D.; Oberli, L.R.; Wilson, M.N.

    1998-07-01

    The relative stability of LHC type cables has been measured by the direct heating of one of the individual strands with a short duration current pulse. The minimum energy required to initiate a quench has been determined for a number of cables which have a central core to increase the effective inter-strand cross-over resistance. Experiments were performed in both normal helium at 4.4 K and superfluid at 1.9 K. Conductors in general are less stable at the lower temperature when measured at the same fraction of critical current. Results show that the cored-cables, even when partially filled with solder or with a porous-metal filler exhibit a relatively low stability at currents close to the critical current. It is speculated that the high inter-strand electrical and thermal resistance inherent in these cables may effect the stability at high currents.

  4. STABILITY MEASUREMENTS ON CORED CABLES IN NORMAL AND SUPERFLUID HELIUM

    SciTech Connect

    GHOSH,A.K.; SAMPSON,W.B.; KIM,S.W.; LEROY,D.; OBERLI,L.R.; WILSON,M.N.

    1998-05-10

    The relative stability of LHC type cables has been measured by the direct heating of one of the individual strands with a short duration current pulse. The minimum energy required to initiate a quench has been determined for a number of cables which have a central core to increase the effective inter-strand cross-over resistance. Experiments were performed in both normal helium at 4.4 K and superfluid at 1.9 K. Conductors in general are less stable at the lower temperature when measured at the same fraction of critical current. Results show that the cored-cables, even when partially filled with solder or with a porous-metal filler exhibit a relatively low stability at currents close to the critical current. It is speculated that the high inter-strand electrical and thermal resistance inherent in these cables may effect the stability at high currents.

  5. Scintillation and quantum evaporation generated by single monoenergetic electrons stopped in superfluid helium

    SciTech Connect

    Adams, J.S.; Kim, Y.H.; Lanou, R.E.; Maris, H.J.; Seidel, G.M.

    1998-12-01

    For several years the authors have been studying the energy deposition in liquid helium at low temperatures by energetic charged particles. This work is motivated by interest in developing a detector for neutrinos emanating from the p-p reaction in the sun. An electron stopped in superfluid helium generates phonons and rotons in the liquid as well as uv photons via scintillation. They report recent measurements with single 364 keV electrons. A sapphire wafer with a superconducting transition-edge sensor is mounted above the liquid and can measure energy and timing information of individual events. The authors observe both uv photons and the quantum evaporation of helium atoms resulting from phonons and rotons generated by the ionizing particle in the liquid. The production of photons and rotons is strikingly different for an electron and for an alpha particle. The origin of the differences is associated with the different density of excitations along the tracks of an alpha particle and an electron.

  6. Imaging Anisotropic Nanoplasma Dynamics in Superfluid Helium Droplets

    NASA Astrophysics Data System (ADS)

    Bacellar, Camila; Chatterley, Adam; Lackner, Florian; Pemmaraju, Sri; Tanyag, Rico; Bernando, Charles; Verma, Deepak; O'Connell, Sean; Osipiv, Timur; Ray, Dipanwita; Ferguson, Kenneth; Gorkhover, Tais; Swiggers, Michele; Bucher, Maximilian; Vilesov, Andrey; Bostedt, Christoph; Gessner, Oliver

    2016-05-01

    The dynamics of strong-field induced nanoplasmas inside superfluid helium droplets are studied using single-shot, single-particle femtosecond time-resolved X-ray coherent diffractive imaging (CDI) at the Linac Coherent Light Source (LCLS). Intense (~ 1015 W/ cm2, ~ 50 fs) 800 nm laser pulses are employed to initiate nanoplasma formation in sub-micron (200 nm - 600 nm) sized helium droplets. The dynamics of the nanoplasma formation and subsequent droplet evolution are probed by x-rays pulses (~ 100 fs, 600 eV) that are delayed with respect to the near-infrared (NIR) pulses by 10's of femtoseconds to hundreds of picoseconds. Pump-probe time-delay dependent effects in the CDI patterns reveal distinct dynamics evolving on multiple timescales. Very fast (<100 fs) appearing features are possibly indicative of electronic dynamics, while slower (>= 1 ps) dynamics are likely associated with structural changes correlated to nuclear motion including droplet disintegration. In particular, the CDI images exhibit strong indications for anisotropic dynamics governed by the NIR polarization axis, providing previously inaccessible insight into the mechanisms of nanoplasma formation and evolution.

  7. Oscillating-grid experiments in water and superfluid helium

    NASA Astrophysics Data System (ADS)

    Honey, Rose E.; Hershberger, Robert; Donnelly, Russell J.; Bolster, Diogo

    2014-05-01

    Passing a fluid through a grid is a well-known mechanism used to study the properties of turbulence. Oscillating a horizontal grid vertically in a tank has also been used extensively and is considered to be a source of almost homogenous isotropic turbulence. When the oscillating grid is turned on a turbulent flow is induced. A front translates into the experimental tank, behind which the flow is highly turbulent. Long predicted that the growth of such a front would grow diffusively as the square root of time (i.e., d ˜√t ) and Dickinson and Long presented experimental evidence for the diffusive result at a low mesh Reynolds number of 555. This paper revisits these experiments and attempts a set of two models for the advancing front in both square and round tanks. We do not observe significant differences between runs in square and round tanks. The experiments in water reach mesh Reynolds numbers of order 30000. Using some data from superfluid helium experiments we are able to explore mesh Reynolds numbers to about 43000. We find the power law for the advancing front decreases weakly with the mesh Reynolds number. Using a very long tank we find that the turbulent front stops completely at a certain depth and attempt a simple explanation for that behavior. We study the propagation of the turbulent front into tubes of different diameters inserted into the main tank. We show that these tubes exclude wavelengths much larger than the tube diameter. We explore the variation of the position of the steady-state boundary H on tube diameter D and find that H =cD with c ˜2. We suggest this may be explained by saturation of the energy-containing length scale ℓe. We also report on the effect of plugging up just one hole of the grid. Finally, we recall some earlier oscillating grid experiments in superfluid 4He in the light of the present results.

  8. Oscillating-grid experiments in water and superfluid helium.

    PubMed

    Honey, Rose E; Hershberger, Robert; Donnelly, Russell J; Bolster, Diogo

    2014-05-01

    Passing a fluid through a grid is a well-known mechanism used to study the properties of turbulence. Oscillating a horizontal grid vertically in a tank has also been used extensively and is considered to be a source of almost homogenous isotropic turbulence. When the oscillating grid is turned on a turbulent flow is induced. A front translates into the experimental tank, behind which the flow is highly turbulent. Long predicted that the growth of such a front would grow diffusively as the square root of time (i.e., d ∼ sqrt[t]) and Dickinson and Long presented experimental evidence for the diffusive result at a low mesh Reynolds number of 555. This paper revisits these experiments and attempts a set of two models for the advancing front in both square and round tanks. We do not observe significant differences between runs in square and round tanks. The experiments in water reach mesh Reynolds numbers of order 30000. Using some data from superfluid helium experiments we are able to explore mesh Reynolds numbers to about 43000. We find the power law for the advancing front decreases weakly with the mesh Reynolds number. Using a very long tank we find that the turbulent front stops completely at a certain depth and attempt a simple explanation for that behavior. We study the propagation of the turbulent front into tubes of different diameters inserted into the main tank. We show that these tubes exclude wavelengths much larger than the tube diameter. We explore the variation of the position of the steady-state boundary H on tube diameter D and find that H = cD with c ∼ 2. We suggest this may be explained by saturation of the energy-containing length scale ℓ(e). We also report on the effect of plugging up just one hole of the grid. Finally, we recall some earlier oscillating grid experiments in superfluid (4)He in the light of the present results.

  9. Motion of metallic microparticles in superfluid helium in the presence of space charge

    NASA Astrophysics Data System (ADS)

    Moroshkin, P.; Leiderer, P.; Kono, K.

    2017-04-01

    We report an experimental and theoretical study of the motion of metallic micro- and nanoparticles in cryogenic superfluid helium in the presence of a static electric field. Depending on the polarity of the applied field, the system is charged with a large number of positive ions or free electrons. For the electrons, we observe the formation of a negative charge layer above the free surface of liquid He and a shuttle-like motion of metallic particles between this layer and the positively charged bottom electrode. For the positive ions, the positive space charge is created in the liquid and the particle motion resembles bouncing off the (negatively charged) bottom electrode. The observations are explained by a theoretical model based on classical electrostatics and hydrodynamics.

  10. Design considerations for a micro-g superfluid helium fluid acquisition system

    NASA Technical Reports Server (NTRS)

    Lee, J. M.

    1989-01-01

    The general description, the operation, and the design of a superfluid helium (SFHe) fluid acquisition system (FAS) for use under microgravity conditions is presented. For the type of FAS considered here, where fine-mesh woven screens are used to retain flowing SFHe within a gallery arm (flow) channel, those forces which determine the flow dynamics are the micro-g accelerations, liquid surface tension, and tensile strength and cumulative pressure drops along a flow path that begins at the bulk liquid and ends at the entrance to a pump. For this case, the dimensionless number, N(T) is written as the ratio between the pressure drop across the screen and the surface tension forces at the screen for low fluid velocities. Static Bond number measurements have bene taken for SFHe using 325 x 2300 twilled Dutch screen and have indicated a screen pore hydraulic radius of 0.00031 cm.

  11. Dynamics and Morphology of Superfluid Helium Drops in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Seidel, George M.; Maris, Humphrey J.

    2001-01-01

    We developed an apparatus that makes it possible to observe and study magnetically levitated drops of superfluid helium. The force on a diamagnetic substance in a magnetic field is proportional to the gradient of the square of the magnetic field B. For the magnetic force on helium to be equal to the gravitational force on Earth, it is necessary for the product of B with the field gradient dB/d z to be 21.5 T(exp 2)/cm. In addition, in order for the magnetic field to provide a stable trap, the value of B(exp 2) must increase in all directions in the horizontal plane that passes through the point where the field/field gradient product in the vertical direction has the critical value of 21.5 T(exp 2)/cm. A specially designed superconducting magnet that meets these specifications has been installed in a large helium dewar with optical access. Helium drops levitated by the magnet can be viewed along the axis of the solenoid. The sample chamber within the bore of the magnet is thermally isolated from the magnet and helium reservoir. Its temperature can be varied between 4 and 0.5 K, the lower part of the range being reached using a He-3 refrigerator. Liquid helium can be injected into the magnetic trap using a small capillary. Once a drop is contained in the trap it can be held there indefinitely. With this apparatus we have conducted a number of different types of experiments on helium drops so as to gain information necessary for performing experiments in space. With magnetically levitated drops we are limited to working with drops of 1 cm. or less in diameter. The shape of the drops larger than a few mm diameter can be distorted by the profile of the magnetic field. The study of phenomena such as the initial motion of the surfaces of two drops as they just make contact, requires the use large drops to resolve the behavior of interest. We have performed a detailed investigation of the shape oscillations of superfluid drops.

  12. Electronic Spectroscopy of Phthalocyanine and Porphyrin Derivatives in Superfluid Helium Nanodroplets.

    PubMed

    Slenczka, Alkwin

    2017-07-25

    Phthalocyanine and porphyrin were among the first organic compounds investigated by means of electronic spectroscopy in superfluid helium nanodroplets. Superfluid helium nanodroplets serve as a very gentle host system for preparing cold and isolated molecules. The uniqueness of helium nanodroplets is with respect to the superfluid phase which warrants the vanishing viscosity and, thus, minimal perturbation of the dopant species at a temperature as low as 0.37 K. These are ideal conditions for the study of molecular spectra in order to analyze structures as well as dynamic processes. Besides the investigation of the dopant species itself, molecular spectroscopy in helium droplets provides information on the helium droplet and in particular on microsolvation. This article, as part of a special issue on phthalocyanines and porphyrins, reviews electronic spectroscopy of phthalocyanine and porphyrin compounds in superfluid helium nanodroplets. In addition to the wide variety of medical as well as technical and synthetical aspects, this article discusses electronic spectroscopy of phthalocyanines and porphyrins in helium droplets in order to learn about both the dopant and the helium environment.

  13. Persistent Currents in a Rotating Superleak Partially Filled with Superfluid Helium.

    DTIC Science & Technology

    1982-12-01

    inside a small nitrogen dewar. A small amount of the molecular sieve, Zeolite, was put in the bottom as a cold trap to keep the helium gas pure. In use...Study of Superfluid Helium, New Directions in Physical Acoustics, Soc. Italians di Fisica Italy, 1976 (Sen) D. Johnson, and P. Sen, Phys. Rev. B, Vol 2

  14. The tensile strength of liquid helium four

    NASA Astrophysics Data System (ADS)

    Nissen, Joel Alan

    1988-08-01

    It is well known that most liquids exhibit a tensile strength which is much smaller in magnitude than the tensile strength predicted by homogeneous nucleation theory. Liquid helium occupies a unique place among liquids for tensile strength measurements because all foreign gases are frozen out at liquid temperatures. Moreover, superfluid He-4 should fill all crevises on solid surfaces, eliminating the chance of heterogeneous nucleation on helium vapor pockets. A piezoelectric transducer in the form of a hemispherical shell was used to focus high intensity ultrasound into a small volume of He-4. The transducer was gated at its resonant frequency of 566 kHz with gate widths of less than 1 msec in order to minimize the effects of transducer heating and acoustic streaming. The onset of nucleation was detected from the absorption of acoustic energy and the scattering of laser light from microscopic bubbles. A theory for light diffraction from the focal zone of a spherical converging sound wave was developed to confirm calculations of the acoustic pressure amplitude at the focus of the transducer, calculations based on the acoustic power radiated into the liquid and nonlinear sound absorption.

  15. The role of vortices in the process of impurity nanoparticles coalescence in liquid helium

    NASA Astrophysics Data System (ADS)

    Gordon, E. B.; Karabulin, A. V.; Matyushenko, V. I.; Sizov, V. D.; Khodos, I. I.

    2012-01-01

    The process of condensation of metal atoms in superfluid helium was shown to occur mainly in the quantized vortices. Firstly the spherical nanocrystals were grown there. At low metal content in liquid they fused then into long cylindrical nanowires. At higher metal content the spherical microparticles were formed instead with their size terminated by mutual repulsion arisen in vortex core. Small number of zigzag-shaped nanowires was found to be formed in usual vortices of normal liquid helium as well. The production of ideal 1-D structures such as long polymer chains was predicted for non-metallic material condensation in superfluid helium.

  16. UCN source with superfluid helium at WWR-M reactor

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Lyamkin, V. A.; Fomin, A. K.; Prudnikov, D. V.; Samodurov, O. Yu; Kanin, A. S.

    2017-01-01

    The WWR-M reactor at PNPI is going to be equipped with an ultracold neutron source of high density. Method of UCN production is based on their accumulation in the super fluid helium due to particular qualities of that quantum liquid. The satisfying storage time of UCN at WWR-M reactor in the super fluid helium exists at a temperature below 1.2 K. Our source aims at obtaining a density of UCN equals to 104 n/cm3, two orders of magnitude exceeding that in existing sources presently available in the world. Increase in the density of UCN will raise the accuracy of the measurement of the neutron electric dipole moment (EDM) of an order of magnitude, which is fundamentally important for the problem of CP violation. The most intense sources of UCN allows PNPI become the centre of fundamental researches with ultracold neutrons.

  17. Thermoluminescence Dynamics During Destructions of Porous Structures Formed by Nitrogen Nanoclusters in Bulk Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Meraki, Adil; Mao, Shun; McColgan, Patrick T.; Boltnev, Roman E.; Lee, David M.; Khmelenko, Vladimir V.

    2016-11-01

    We studied the dynamics of thermoluminescence during destruction of porous structures formed by nanoclusters of nitrogen molecules containing high concentrations of stabilized nitrogen atoms. The porous structures were formed in bulk superfluid helium by injection of the products of discharges in nitrogen-helium gas mixtures through the liquid helium surface. Fast recombination of nitrogen atoms during warming-up led to explosive destruction of the porous structures accompanied by bright flashes. Intense emissions from the α -group of nitrogen atoms, the β -group of oxygen atoms and the Vegard-Kaplan bands of N_2 molecules were observed at the beginning of destruction. At the end of destruction the M- and β -bands of NO molecules as well as bands of O_2 molecules were also observed. Observation of the emissions from NO molecules at the end of destruction was explained by processes of accumulation of NO molecules in the system due to the large van der Waals interaction of NO molecules. For the first time, we observed the emission of the O_2 molecules at the end of destruction of the porous nitrogen structures as a result of the (NO)_2 dimer formation in solid nitrogen and subsequent processes leading to the appearance of excited O_2 molecules.

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

    NASA Technical Reports Server (NTRS)

    Hildebrandt, A. F.

    1964-01-01

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

  19. Putting in operation a full-scale ultracold-neutron source model with superfluid helium

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Lyamkin, V. A.; Prudnikov, D. V.; Keshishev, K. O.; Boldarev, S. T.; Vasil'ev, A. V.

    2017-02-01

    A project of the source of ultracold neutrons for the WWR-M reactor based on superfluid helium for ultracold-neutron production has been developed. The full-scale source model, including all required cryogenic and vacuum equipment, the cryostat, and the ultracold-neutron source model has been created. The superfluid helium temperature T = 1.08 K without a heat load and T = 1.371 K with a heat load on the simulator of P = 60 W has been achieved in experiments at a technological complex of the ultracold-neutron source. The result proves the feasibility of implementing the ultracold-neutron source at the WWR-M reactor and the possibility of applying superfluid helium in nuclear engineering.

  20. Liquid helium fluid dynamics studies

    SciTech Connect

    Van Sciver, S.W.

    1989-01-01

    The main focus of the first three year period of this research program was to set up our liquid helium flow facility and begin experiments on the flow of liquid helium within this system. The first task of our experimental program involved the set up and check out of the liquid helium flow facility (LHFF). This facility is the centerpost of our fluid dynamics experiments. The LHFF is designed to allow a variety of experiments which test important helium fluid dynamics behavior on a scale close to that involved in large scale applications. To achieve this goal, we chose a horizontal dewar configuration with a cold bore access on either end. A nominal length of five meters was selected with a sufficiently large inner diameter to allow insertion of various tubing configurations, flow metering devices and heat exchangers. Further, to minimize consumption of liquid helium, the dewar design includes two actively cooled shields; one cooled by LN/sub 2/ to 77 K and one at 4.5 K maintained by a closed cycle helium refrigerator. Helium flow is to be provided by a cold centrifugal pump. 4 refs., 2 figs.

  1. Particle Detection in Superfluid Helium: R&D for Low Energy Solar Neutrinos

    SciTech Connect

    Lanou, Robert E., Jr.

    2006-03-31

    This report presents a summary of the results from R&D conducted as a feasibility study in the Department of Physics of Brown University for detection of low energy solar neutrinos utilizing a superfluid helium target. The report outlines the results in several areas: 1) development of experimental facilities, 2) energy deposition by electrons and alphas in superfluid helium, 3) development of wafer and metallic magnetic calorimeters, 4) background studies, 5) coded apertures and conceptual design, 6) Detection of single electrons and 7) a simulation of expected performance of a full scale device. Recommendations for possible future work are also presented. A bibliography of published papers and unpublished doctoral theses is included.

  2. Discrete liquid/vapor detectors for use in liquid helium

    NASA Technical Reports Server (NTRS)

    Dipirro, M. J.; Serlemitsos, A. T.

    1990-01-01

    Simple devices have been constructed and tested which can discriminate between liquid helium and its vapor. The devices are 0.25-mm doped silicon cubes suspended from 0.05-mm-diameter stainless steel and manganin wires. A small current is passed through the device heating it and lowering its resistance. The degree of self-heating is dependent on whether the device is immersed in liquid or is surrounded by vapor. The voltage across the device then indicates the presence of liquid or vapor. The devices are meant to operate in the milligravity environment of space. Tests simulating thick superfluid films which would be present in this case indicate less than 0.3 milliwatt per detector is sufficient to boil away these thick films. The detector response time under these conditions is less than 50 milliseconds.

  3. On the mechanism of electromagnetic microwave absorption in superfluid helium

    SciTech Connect

    Pashitskii, E. A. Pentegov, V. I.

    2012-08-15

    In experiments on electromagnetic (EM) wave absorption in the microwave range in superfluid (SF) helium [1-3], a narrow EM field absorption line with a width on the order of (20-200) kHz was observed against the background of a wide absorption band with a width of 30-40 GHz at frequencies f{sub 0} Almost-Equal-To 110-180 GHz corresponding to the roton gap energy {Delta}{sub r}(T) in the temperature range 1.4-2.2 K. Using the so-called flexoelectric mechanism of polarization of helium atoms ({sup 4}He) in the presence of density gradients in SF helium (HeII), we show that nonresonance microwave absorption in the frequency range 170-200 GHz can be due to the existence of time-varying local density gradients produced by roton excitations in the bulk HeII. The absorption bandwidth is determined by the roton-roton scattering time in an equilibrium Boltzmann gas of rotons, which is t{sub r-r} Almost-Equal-To 3.4 Multiplication-Sign 10{sup -11} s at T = 1.4 K and decreases upon heating. We propose that the anomalously narrow microwave resonance absorption line in HeII at the roton frequency f{sub 0}(T) = {Delta}r(T)/2{pi}h appears due to the following two factors: (i) the discrete structure of the spectrum of the surface EM resonator modes in the form of a periodic sequence of narrow peaks and (ii) the presence of a stationary dipole layer in HeII near the resonator surface, which forms due to polarization of {sup 4}He atoms under the action of the density gradient associated with the vanishing of the density of the SF component at the solid wall. For this reason, the relaxation of nonequilibrium rotons generated in such a surface dipole layer is strongly suppressed, and the shape and width of the microwave resonance absorption line are determined by the roton density of states, which has a sharp peak at the edge of the roton gap in the case of weak dissipation. The effective dipole moments of rotons in the dipole layer can be directed either along or across the normal to

  4. Flow visualization in superfluid helium-4 using He2 molecular tracers

    NASA Astrophysics Data System (ADS)

    Guo, Wei

    Flow visualization in superfluid helium is challenging, yet crucial for attaining a detailed understanding of quantum turbulence. Two problems have impeded progress: finding and introducing suitable tracers that are small yet visible; and unambiguous interpretation of the tracer motion. We show that metastable He2 triplet molecules are outstanding tracers compared with other particles used in helium. These molecular tracers have small size and relatively simple behavior in superfluid helium: they follow the normal fluid motion at above 1 K and will bind to quantized vortex lines below about 0.6 K. A laser-induced fluorescence technique has been developed for imaging the He2 tracers. We will present our recent experimental work on studying the normal-fluid motion by tracking thin lines of He2 tracers created via femtosecond laser-field ionization in helium. We will also discuss a newly launched experiment on visualizing vortex lines in a magnetically levitated superfluid helium drop by imaging the He2 tracers trapped on the vortex cores. This experiment will enable unprecedented insight into the behavior of a rotating superfluid drop and will untangle several key issues in quantum turbulence research. We acknowledge the support from the National Science Foundation under Grant No. DMR-1507386 and the US Department of Energy under Grant No. DE-FG02 96ER40952.

  5. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams.

    PubMed

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M; Kong, Wei

    2015-08-01

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2(+) and He4(+), which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)(n)C(+), (He)(n)Cl(+), and (He)(n)CCl(+). Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

  6. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

    SciTech Connect

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei

    2015-08-15

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He{sub 2}{sup +} and He{sub 4}{sup +}, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl{sub 4} doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He){sub n}C{sup +}, (He){sub n}Cl{sup +}, and (He){sub n}CCl{sup +}. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

  7. Microsolvation of molecules in superfluid helium nanodroplets revealed by means of electronic spectroscopy.

    PubMed

    Premke, Tobias; Wirths, Eva-Maria; Pentlehner, Dominik; Riechers, Ricarda; Lehnig, Rudolf; Vdovin, Alexander; Slenczka, Alkwin

    2014-01-01

    The empirical model explaining microsolvation of molecules in superfluid helium droplets proposes a non-superfluid helium solvation layer enclosing the dopant molecule. This model warrants an empirical explanation of any helium induced substructure resolved for electronic transitions of molecules in helium droplets. Despite a wealth of such experimental data, quantitative modeling of spectra is still in its infancy. The theoretical treatment of such many-particle systems dissolved into a quantum fluid is a challenge. Moreover, the success of theoretical activities relies also on the accuracy and self-critical communication of experimental data. This will be elucidated by a critical resume of our own experimental work done within the last ten years. We come to the conclusion that spectroscopic data and among others in particular the spectral resolution depend strongly on experimental conditions. Moreover, despite the fact that none of the helium induced fine structure speaks against the empirical model for solvation in helium droplets, in many cases an unequivocal assignment of the spectroscopic details is not possible. This ambiguity needs to be considered and a careful and critical communication of experimental results is essential in order to promote success in quantitatively understanding microsolvation in superfluid helium nanodroplets.

  8. Microsolvation of molecules in superfluid helium nanodroplets revealed by means of electronic spectroscopy

    PubMed Central

    Premke, Tobias; Wirths, Eva-Maria; Pentlehner, Dominik; Riechers, Ricarda; Lehnig, Rudolf; Vdovin, Alexander; Slenczka, Alkwin

    2014-01-01

    The empirical model explaining microsolvation of molecules in superfluid helium droplets proposes a non-superfluid helium solvation layer enclosing the dopant molecule. This model warrants an empirical explanation of any helium induced substructure resolved for electronic transitions of molecules in helium droplets. Despite a wealth of such experimental data, quantitative modeling of spectra is still in its infancy. The theoretical treatment of such many-particle systems dissolved into a quantum fluid is a challenge. Moreover, the success of theoretical activities relies also on the accuracy and self-critical communication of experimental data. This will be elucidated by a critical resume of our own experimental work done within the last ten years. We come to the conclusion that spectroscopic data and among others in particular the spectral resolution depend strongly on experimental conditions. Moreover, despite the fact that none of the helium induced fine structure speaks against the empirical model for solvation in helium droplets, in many cases an unequivocal assignment of the spectroscopic details is not possible. This ambiguity needs to be considered and a careful and critical communication of experimental results is essential in order to promote success in quantitatively understanding microsolvation in superfluid helium nanodroplets. PMID:25077143

  9. Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

    PubMed Central

    He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei

    2015-01-01

    We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He2+ and He4+, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl4 doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He)nC+, (He)nCl+, and (He)nCCl+. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets. PMID:26329210

  10. (abstract) Production and Levitation of Free Drops of Liquid Helium

    NASA Technical Reports Server (NTRS)

    Paine, C. G.; Petrac, D.; Rhim, W. K.

    1995-01-01

    We are interested in the nucleation and behavior of quantized vorticies and surface excitations in free drops of superfluid helium. We have constructed an apparatus to maintain liquid helium drops isolated from any material container in the Earth's gravitational field, and have investigated two techniques for generating and introducing liquid drops into the region of confinement. The levitation apparatus utilizes the electrostatic force acting upon a charged liquid drop to counteract the gravitational force, with drop position stability provided by a static magnetic field acting upon the helium diamagnetic moment. Electrically neutral superfluid drops have been produced with a miniature thermomechanical pump; for a given configuration the liquid initial velocity has been varied up to several centimeters per second. Liquid drops carrying either net positive or negative charge are produced by an electrode which generates a flow of ionized liquid from the bulk liquid surface. Potentials of less than one thousand volts to several thousand volts are required. The mass flow is controlled by varying duration of the ionizing voltage pulse; drops as small as 30 micrometers diameter, charged to near the Rayleigh limit, have been observed.

  11. Electron impact ionization and multiphoton ionization of doped superfluid helium droplets: A comparison.

    PubMed

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-02-28

    We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped superfluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI directly ionizes helium atoms in a droplet therefore has higher yields for bigger droplets (within a limited size range), MPI is insensitive to the helium in a droplet and is only dependent on the number of dopant molecules. The optimal timing of the ionization pulse also varies with the doping pressure, implying a velocity slip among different sized droplets. Calculations of the doping statistics and ionization probabilities qualitatively agree with the experimental data. Our results offer a word of caution in interpreting the pressure and timing dependence of superfluid helium droplets, and we also devise a scheme in achieving a high degree of doping while limiting the contribution of dopant clusters.

  12. Electron impact ionization and multiphoton ionization of doped superfluid helium droplets: A comparison

    PubMed Central

    2016-01-01

    We compare characteristics of electron impact ionization (EI) and multiphoton ionization (MPI) of doped superfluid helium droplets using the same droplet source. Selected dopant ion fragments from the two ionization schemes demonstrate different dependence on the doping pressure, which could be attributed to the different ionization mechanisms. While EI directly ionizes helium atoms in a droplet therefore has higher yields for bigger droplets (within a limited size range), MPI is insensitive to the helium in a droplet and is only dependent on the number of dopant molecules. The optimal timing of the ionization pulse also varies with the doping pressure, implying a velocity slip among different sized droplets. Calculations of the doping statistics and ionization probabilities qualitatively agree with the experimental data. Our results offer a word of caution in interpreting the pressure and timing dependence of superfluid helium droplets, and we also devise a scheme in achieving a high degree of doping while limiting the contribution of dopant clusters. PMID:26931697

  13. Temperature dependent mobility measurements of alkali earth ions in superfluid helium

    NASA Astrophysics Data System (ADS)

    Putlitz, Gisbert Zu; Baumann, I.; Foerste, M.; Jungmann, K.; Riediger, O.; Tabbert, B.; Wiebe, J.; Zühlke, C.

    1998-05-01

    Mobility measurements of impurity ions in superfluid helium are reported. Alkali earth ions were produced with a laser sputtering technique and were drawn inside the liquid by an electric field. The experiments were carried out in the temperature region from 1.27 up to 1.66 K. The temperature dependence of the mobility of Be^+-ions (measured here for the first time) differs from that of the other alkali earth ions Mg^+, Ca^+, Sr^+ and Ba^+, but behaves similar to that of He^+ (M. Foerste, H. Günther, O. Riediger, J. Wiebe, G. zu Putlitz, Z. Phys. B) 104, 317 (1997). Theories of Atkins (A. Atkins, Phys. Rev.) 116, 1339 (1959) and Cole (M.W. Cole, R.A. Bachmann Phys. Rev. B) 15, 1388 (1977) predict a different defect structure for He^+ and the alkali earth ions: the helium ion is assumed to form a snowball like structure whereas for the alkali earth ions a bubble structure is assumed. If the temperature dependence is a characteristic feature for the different structures, then it seems likely that the Be^+ ion builds a snowball like structure.

  14. Effect of an electric field on superfluid helium scintillation produced by α-particle sources

    NASA Astrophysics Data System (ADS)

    Ito, T. M.; Clayton, S. M.; Ramsey, J.; Karcz, M.; Liu, C.-Y.; Long, J. C.; Reddy, T. G.; Seidel, G. M.

    2012-04-01

    We report a study of the intensity and time dependence of scintillation produced by weak α-particle sources in superfluid helium in the presence of an electric field (0-45 kV/cm) in the temperature range of 0.2 to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40% of the scintillation results from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the α track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.

  15. Optical and mechanical properties of electron bubbles in superfluid helium-4

    SciTech Connect

    Xie, Z.; Wei, W.; Yang, Y.; Maris, H. J.

    2014-12-15

    A series of experiments has revealed the existence of a large number (about 18) of different types of negative ions in superfluid helium-4. Despite much effort, the physical nature of these “exotic ions” has still not been determined. We discuss possible experiments which may be able to help determine the structure of these objects.

  16. Magnetic trapping of superconducting submicron particles produced by laser ablation in superfluid helium

    NASA Astrophysics Data System (ADS)

    Takahashi, Yuta; Suzuki, Junpei; Yoneyama, Naoya; Tokawa, Yurina; Suzuki, Nobuaki; Matsushima, Fusakazu; Kumakura, Mitsutaka; Ashida, Masaaki; Moriwaki, Yoshiki

    2017-02-01

    We produced spherical superconducting submicron particles by laser ablation of their base metal tips in superfluid helium, and trapped them using a quadrupole magnetic field owing to the diamagnetism caused by the Meissner effect. We also measured their critical temperatures of superconductivity, by observing the threshold temperatures for the confinement of superconducting submicron particles in the trap.

  17. Ordinary SQUID interferometers and superfluid helium matter wave interferometers: The role of quantum fluctuations

    SciTech Connect

    Golovashkin, A. I.; Zherikhina, L. N. Tskhovrebov, A. M.; Izmailov, G. N.; Ozolin, V. V.

    2010-08-15

    When comparing the operation of a superfluid helium matter wave quantum interferometer (He SQUID) with that of an ordinary direct-current quantum interferometer (dc SQUID), we estimate their resolution limitation that correspond to quantum fluctuations. An alternative mode of operation of the interferometer as a unified macroquantum system is considered.

  18. On the electric activity of superfluid helium at the excitation of first and second sound waves

    SciTech Connect

    Pashitskii, E. A. Gurin, A. A.

    2010-01-15

    We show that the electric activity of superfluid helium (HeII) observed in the experiments [3] during the excitation of standing second sound waves in an acoustic resonator can be described in terms of the phenomenological mechanism of the inertial polarization of atoms in a dielectric, in particular, in HeII, when the polarization field induced in the medium is proportional to the mechanical acceleration, by analogy with the Stewart-Tolman effect. The variable relative velocity w = v{sub n} - v{sub s} of the normal and superfluid HeII components that emerges in the second sound wave determines the mean group velocity of rotons, V{sub g} Almost-Equal-To w, with the density of the normal component related to their equilibrium number density in the temperature range 1.3 K {<=} T {<=} 2 K. Therefore, the acceleration of the 4He atoms involved in the formation of a roton excitation is proportional to the time derivative of the relative velocity.w. In this case, the linear local relations between the variable values of the electric induction, electric field strength, and polarization vector should be taken into account. As a result, the variable displacement current induced in the bulk of HeII and the corresponding potential difference do not depend on the anomalously low polarizability of liquid helium. This allows the ratio of the amplitudes of the temperature and potential oscillations in the second sound wave, which is almost independent of T in the above temperature range, consistent with experimental data to be obtained. At the same time, the absence of an electric response during the excitation of first sound waves in the linear regime is related to an insufficient power of the sound oscillations. Based on the experimental data on the excitation of first and second sounds, we have obtained estimates for the phenomenological coefficient of proportionality between the polarization vector and acceleration and for the drag coefficient of helium atoms by rotons in the

  19. Knowledge based and interactive control for the Superfluid Helium On-orbit Transfer Project

    NASA Technical Reports Server (NTRS)

    Castellano, Timothy P.; Raymond, Eric A.; Shapiro, Jeff C.; Robinson, Frank A.; Rosenthal, Donald A.

    1989-01-01

    NASA's Superfluid Helium On-Orbit Transfer (SHOOT) project is a Shuttle-based experiment designed to acquire data on the properties of superfluid helium in micro-gravity. Aft Flight Deck Computer Software for the SHOOT experiment is comprised of several monitoring programs which give the astronaut crew visibility into SHOOT systems and a rule based system which will provide process control, diagnosis and error recovery for a helium transfer without ground intervention. Given present Shuttle manifests, this software will become the first expert system to be used in space. The SHOOT Command and Monitoring System (CMS) software will provide a near real time highly interactive interface for the SHOOT principal investigator to control the experiment and to analyze and display its telemetry. The CMS software is targeted for all phases of the SHOOT project: hardware development, pre-flight pad servicing, in-flight operations, and post-flight data analysis.

  20. Solvation of triplet Rydberg states of molecular hydrogen in superfluid helium

    NASA Astrophysics Data System (ADS)

    Kiljunen, Toni; Lehtovaara, Lauri; Kunttu, Henrik; Eloranta, Jussi

    2004-01-01

    We report ab initio interaction potentials, transition dipole moments, and radiative lifetimes for the four lowest triplet states of H2: b 3Σ+u, c 3Πu, a 3Σ+g, and e 3Σ+u, and their response to the perturbation due to approaching ground state He atom. Hybrid density functional quantum Monte Carlo calculations employing the ab initio interaction potentials are then used for calculating the liquid structure around the molecular excimers in bulk superfluid 4He. Calculations demonstrate a wide variety of possible solvation structures, both spherical and highly anisotropic in geometry, depending on the electronic state of H2. The experimentally observed H2 (3e3a) emission bands [Trottier et al., Phys. Rev. A 61, 052504 (2000)] are simulated and the origins of the line shifts discussed. Absorption spectra of the same system are predicted to be broader and more blue shifted compared to the gas phase. Feasibility of the metastable 3c state for absorption experiments in liquid helium is proposed.

  1. Study of an all SFHE SIRTF cryogenic system. [SuperFluid HElium

    NASA Technical Reports Server (NTRS)

    Urbach, A. R.; Kelly, T. K.; Poley, R.

    1986-01-01

    The Space Infrared Telescope Facility (SIRTF) is a superfluid helium cooled, 85-cm telescope with three infrared instruments at the focal plane. SIRTF will establish in space a long-term-maintainable infrared observatory for the region of 2-700 microns. The cryogenic system can be designed to last up to six years with 1280 kg of superfluid, and can function in either a 28.5 deg or 98 deg inclination orbit by exchanging the sunshade. The lifetime is primarily a function of instrument heat load rather than parasitic heat to the cryogen system.

  2. Controlled evaporation of superfluid helium in a porous plug phase separator

    NASA Astrophysics Data System (ADS)

    Lages, Christopher R.

    1998-12-01

    regime beyond the critical mass flow rate separating this regime from the unpredictable and hysteretic 'choked' flow regime of the plug. The mass flow increase is stable, and all heat utilized in heating the downstream surface goes into evaporation of liquid helium. Data show the mass flow increase can be obtained while the thermodynamic conditions on either side of the plug are measurably unchanged. This indicates the mechanism providing the additional mass flow of liquid helium is decoupled from counterflow of its normal and superfluid components. This is consistent with the effects of parasitic heat leaking into the downstream side of a porous plug. Further results presented in this thesis include thermodynamic-based computations of liquid helium phase separation in capillaries and discussion of how computational models can be used to bind the flow regimes of porous plugs. These computational models coupled with the controlled evaporation technique simplify the flight porous plug selection process for a mission. (Abstract shortened by UMI.)

  3. Development of a superfluid helium-4 phase slip gyroscope

    NASA Astrophysics Data System (ADS)

    Bruckner, Niels

    2002-04-01

    This dissertation describes experiments with superfluid 4He diaphragm-aperture oscillators that have been configured to act as sensitive detectors of rotation. The goal of this thesis was to increase the rotational sensitivity of the newly developed superfluid 4He phase slip gyroscope in an effort to understand the intrinsic mechanisms that might ultimately limit the sensitivity of this class of device. Four separate devices were built and tested using two different methods of analysis. Two of these experimental cells demonstrated a sensitivity to rotation, culminating with a large area multi-turn device with a sensing loop area that is 2 orders of magnitude larger than our original proof-of-principle prototype. The sensitivity of this device exceeds any other superfluid 4He gyroscope by a factor of ˜25. In addition, this rotation sensor has excellent long term stability and we have found no fundamental mechanisms that will prevent even further improvements. On the other hand, the two devices that failed as gyroscopes provided useful insight into the characteristics that make certain apertures better suited than others for these phase slip experiments. Detailed numerical simulations were used to interpret and analyze our data within the framework of the thermal nucleation theory for the creation of vortices. The formulism developed here also provides a methodology for characterizing the sensitivity of future devices operating in a noisy rotational environment.

  4. Lab tests of a thermomechanical pump for shoot. [Superfluid Helium On-Orbit Transfer

    NASA Technical Reports Server (NTRS)

    Dipirro, Michael J.; Boyle, Robert F.

    1988-01-01

    Laboratory tests of a thermomechanical (TM) pump utilizing a commercially available porous disk have been conducted. Various size disks, heater configurations, and outlet flow impedances have been used to characterize scale models of the pump proposed for the Superfluid Helium On-Orbit Transfer (SHOOT) Flight Experiment. The results yield the scalability of the TM pump to larger diameters, and hence larger pumping rates, the dependence of flow rate on back pressure and heater power, and the limits of pumping speed due to internal losses within the porous disk due to mutual and superfluid friction. Analysis indicates that for low back pressures the flow rate is limited by the superfluid friction rather than the mutual friction. For the porous plug used in the early tests this amounts to a practical limit of 4.4 liters per hour per square centimeter. For a baselined flight plug area of 180 sq cm this yields 790 liters per hour.

  5. Superfluid helium testing of a stainless steel to titanium piping transition joint

    SciTech Connect

    Soyars, W.; Basti, A.; Bedeschi, F.; Budagov, J.; Foley, M.; Harms, E.; Klebaner, A.; Nagaitsev, S.; Sabirov, B.; Dubna, JINR

    2009-11-01

    Stainless steel-to-titanium bimetallic transitions have been fabricated with an explosively bonded joint. This novel joining technique was conducted by the Russian Federal Nuclear Center, working under contract for the Joint Institute for Nuclear Research. These bimetallic transitions are being considered for use in future superconducting radio-frequency cavity cryomodule assemblies. This application requires cryogenic testing to demonstrate that this transition joint remains leak-tight when sealing superfluid helium. To simulate a titanium cavity vessel connection to a stainless steel service pipe, bimetallic transition joints were paired together to fabricate piping assemblies. These piping assemblies were then tested in superfluid helium conditions at Fermi National Accelerator Laboratory test facilities. The transition joint test program will be described. Fabrication experience and test results will be presented.

  6. An ETF TF-coil concept employing NbTi alloy, bath cooled with superfluid helium

    NASA Astrophysics Data System (ADS)

    Hsu, Y.-H.; Purcell, J. R.; Alcorn, J. S.; Homeyer, W.

    1981-01-01

    A preliminary study has been performed to assess the feasibility and engineering consideration of employing NbTi alloy conductor, bath cooled with superfluid helium (He II), in an Engineering Test Facility (ETF) toroidal field (TF) coil. This study indicates that saturated superfluid helium (He II) merits serious consideration as an alternative to the use of He I for high field (11-12 tesla) NbTi alloy TF-coils, which require bath temperatures below 4 K. The primary advantages of He II over reduced temperature (2.5-3 K) He I are two: (1) Due to the extremely high thermal conductivity of He II, almost all of the sub-lambda enthalpy is available to absorb local or transient heat loads; and (2) the relatively high surface heat transfer results in substantially improved conductor stability characteristics. The disadvantages of He II relative to reduced temperature He I are increased refrigeration power and pumping requirements, and some additional system complexity.

  7. Production of zero energy radioactive beams through extraction across superfluid helium surface

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Huang, W. X.; Gloos, K.; Dendooven, P.; Pekola, J. P.; Äystö, J.

    2003-05-01

    A radioactive 223Ra source was immersed in superfluid helium at 1.2- 1.7 K. Electric fields transported recoiled 219Rn ions in the form of snowballs to the surface and further extracted them across the surface. The ions were focussed onto an aluminium foil and alpha particle spectra were taken with a surface barrier spectrometer. This enabled us to determine the efficiency for each process unambiguously. The pulsed second sound wave proved effective in enhancing the extraction of positive ions from the surface. Thus we offer a novel method for study of impurities in superfluid helium and propose this method for production of zero energy nuclear beams for use at radioactive ion beam facilities.

  8. Semiclassical dynamics of vortices in superfluid helium thin films

    NASA Astrophysics Data System (ADS)

    Li, Xiao; Cheng, Ran; Niu, Qian

    2011-03-01

    Based on the Berry phase theory, we consider the case of two vortices in Bosonic superfluids and try to extract the interaction between them. Under the adiabatic approximation, we use semiclassical Lagrangian formalism to describe the system and found that in addition to the universal background ``magnetic field'' which results in the Magnus force, there exists a new interaction mediated by the density profile of the background fluid due to its finite compressibility. Finally, numerical solutions from the nonlinear Schrodinger equation were employed to gain better insight into this problem.

  9. Interactive remote control for an STS-based superfluid helium transfer demonstration

    NASA Technical Reports Server (NTRS)

    Shapiro, Jeff C.; Robinson, Frank A.

    1989-01-01

    NASA's superfluid helium on-orbit transfer (SHOOT) experiment, which is a Shuttle-based demonstration of the technology required to service cryogenically cooled satellites in space, is described. The SHOOT Command and Monitoring System software, developed on Macintosh II, will provide a near-real-time highly interactive interface making it possible to control the experiment and to analyze and display its telemetry. User interface is discussed as well as conversion functions, and hardware.

  10. Detecting scintillations in liquid helium

    NASA Astrophysics Data System (ADS)

    Huffman, P. R.; McKinsey, D. N.

    2013-09-01

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

  11. Molecular rotation and dynamics in superfluid helium-4 nanodroplets

    NASA Astrophysics Data System (ADS)

    Callegari, Carlo

    2000-11-01

    Cavity-enhanced laser radiation, coupled to molecular- beam bolometric detection has been used to study the spectroscopy of acetylenic molecules embedded in helium nanodroplets. The 2ν1 transition (CH stretch overtone) of HCN, DCCH, NCCCH, CH3CCH, CF3CCH, (CH 3)3CCCH, (CH3)3SiCCH, has been investigated in the 1.5 μm spectral region by means of a color center laser coupled to a resonant build-up cavity, which enhances the laser power experienced by the molecules in the beam by up to a factor of 400, thus overcoming the weakness of the (dipole forbidden) transitions. All molecules are observed to rotate freely in the liquid cluster environment, with strongly enhanced moments of inertia, but with negligible matrix induced shifts (less than 1 cm-1). We show that this enhancement is largely accounted for by hydrodynamic effects, which we have modeled and numerically calculated. While in the gas phase the rotational lines have instrument-limited widths (a few MHZ), in the droplets we have observed linewidths ranging from 600 MHz for (CH3)3SiCCH to 2.8GHz for (CH3) 3CCCH. To investigate the nature of the broadening (which was widely believed to be homogeneous), we have performed a series of infrared (IR) saturation experiments on the 2ν1 transition. We have also thoroughly investigated NCCCH by means of microwave (MW) single-resonance experiments (on rotational transitions) and double-resonance (MW-MW and MW-IR) experiments. The results demonstrate that the spectral features of molecules in He droplets are inhomogeneously broadened, and allow an estimate of the importance of the different broadening contributions. In particular, MW-IR measurements show that the size of the cluster greatly affects the way rotational energy is relaxed. Large clusters seem to follow a ``strong collision model'' where memory of the initial rotational state is completely lost after each ``relaxation'' event, while for smaller clusters relaxation rates are probably affected by the lower

  12. Coupling an Ensemble of Electrons on Superfluid Helium to a Superconducting Circuit

    NASA Astrophysics Data System (ADS)

    Yang, Ge; Fragner, A.; Koolstra, G.; Ocola, L.; Czaplewski, D. A.; Schoelkopf, R. J.; Schuster, D. I.

    2016-01-01

    The quantized lateral motional states and the spin states of electrons trapped on the surface of superfluid helium have been proposed as basic building blocks of a scalable quantum computer. Circuit quantum electrodynamics allows strong dipole coupling between electrons and a high-Q superconducting microwave resonator, enabling such sensitive detection and manipulation of electron degrees of freedom. Here, we present the first realization of a hybrid circuit in which a large number of electrons are trapped on the surface of superfluid helium inside a coplanar waveguide resonator. The high finesse of the resonator allows us to observe large dispersive shifts that are many times the linewidth and make fast and sensitive measurements on the collective vibrational modes of the electron ensemble, as well as the superfluid helium film underneath. Furthermore, a large ensemble coupling is observed in the dispersive regime during experiment, and it shows excellent agreement with our numeric model. The coupling strength of the ensemble to the cavity is found to be ≈1 MHz per electron, indicating the feasibility of achieving single electron strong coupling.

  13. Coupling an Ensemble of Electrons on Superfluid Helium to a Superconducting Circuit

    SciTech Connect

    Yang, Ge; Fragner, Andreas; Koolstra, Gerwin; Ocola, Leonidas E.; Czaplewski, David A.; Schoelkopf, Robert J.; Schuster, David I.

    2016-03-21

    The quantized lateral motional states and the spin states of electrons trapped on the surface of superfluid helium have been proposed as basic building blocks of a scalable quantum computer. Circuit quantum electrodynamics allows strong dipole coupling between electrons and a high-Q superconducting microwave resonator, enabling such sensitive detection and manipulation of electron degrees of freedom. Here, we present the first realization of a hybrid circuit in which a large number of electrons are trapped on the surface of superfluid helium inside a coplanar waveguide resonator. The high finesse of the resonator allows us to observe large dispersive shifts that are many times the linewidth and make fast and sensitive measurements on the collective vibrational modes of the electron ensemble, as well as the superfluid helium film underneath. Furthermore, a large ensemble coupling is observed in the dispersive regime during experiment, and it shows excellent agreement with our numeric model. The coupling strength of the ensemble to the cavity is found to be approximate to 1 MHz per electron, indicating the feasibility of achieving single electron strong coupling.

  14. Energy spectrum of thermal counterflow turbulence in superfluid helium-4

    NASA Astrophysics Data System (ADS)

    Gao, J.; Varga, E.; Guo, W.; Vinen, W. F.

    2017-09-01

    Recent preliminary experiments [A. Marakov et al., Phys. Rev. B 91, 094503 (2015)., 10.1103/PhysRevB.91.094503] using triplet-state He2 excimer molecules as tracers of the motion of the normal fluid have shown that, in thermal counterflow turbulence in superfluid 4He, small-scale turbulence in the superfluid component is accompanied, above a critical heat flux, by partially coupled large-scale turbulence in both fluids, with an energy spectrum proportional to k-m, where m is greater than the Kolmogorov value of 5/3. Here we report the results of a more detailed study of this spectrum over a range of temperatures and heat fluxes using the same experimental technique. We show that the exponent m varies systematically with heat flux but is always greater than 5/3. We interpret this as arising from the steady counterflow, which causes large-scale eddies in the two fluids to be pulled in opposite directions, giving rise to dissipation by mutual friction at all wave numbers, mutual friction tending also to oppose the effect of the counterflow. Comparison of the experimental results with a simple theory suggests that this process may be more complicated than we might have hoped, but experiments covering a wider range of heat fluxes, which are technically very difficult, will probably be required before we can arrive at a convincing theory.

  15. Laser ionization and spectroscopy of Cu in superfluid helium nanodroplets

    PubMed Central

    Lindebner, Friedrich; Kautsch, Andreas; Koch, Markus; Ernst, Wolfgang E.

    2014-01-01

    Mass and optical spectroscopic methods are used for the analysis of copper (Cu) atoms and clusters doped to helium nanodroplets (HeN). A two-color resonant two-photon ionization scheme is applied to study the Cu 2P1/2,3/2∘←2S1/2 ground state transition. The absorption is strongly broadened for Cu atoms submerged inside helium nanodroplets and a comparison with computed literature values is provided. An observed ejection of the dopant from the droplet is triggered upon excitation, populating energetically lower states. The formation of Cun clusters up to Cu7 inside helium nanodroplets was observed by means of electron impact ionization mass spectroscopy. PMID:25844053

  16. Helium Saturation of Liquid Propellants

    NASA Technical Reports Server (NTRS)

    Yavrouian, A. H.; Moran, Clifford M.

    1990-01-01

    The research is in three areas which are: (1) techniques were devised for achieving the required levels of helium (He) saturation in liquid propellants (limited to monomethylhydrazine (MMH) and nitrogen tetroxide (NTO)); (2) the values were evaluated for equilibrium solubilities of He in liquid propellants as currently used in the industry; and (3) the He dissolved in liquid propellants were accurately measured. Conclusions drawn from these studies include: (1) Techniques for dissolving He in liquid propellants depending upon the capabilities of the testing facility (Verification of the quantity of gas dissolved is essential); (2) Until greater accuracy is obtained, the equilibrium solubility values of He in MMH and NTO as cited in the Air Force Propellant Handbooks should be accepted as standard (There are still enough uncertainties in the He saturation values to warrant further basic experimental studies); and (3) The manometric measurement of gas volume from a frozen sample of propellant should be the accepted method for gas analysis.

  17. Characterisation of Aerogel Inner Structure with Superfluid Helium Flow

    SciTech Connect

    Coleman, S.; Vassilicos, J. C.

    2006-09-07

    We have developed a numerical technique that firstly obtains the shape of an adsorbed film on a fractal structure via minimisation of the grand potential functional of the system. This film shape is then used to define the geometry of a potential flow problem, which models the flow of the superfluid film due to an external pressure gradient, with the assumption that the flow velocities are so small so as not to alter the shape of the film. Using a microscopic definition of tortuosity, it is found that in 2D, tortuosity scales with the amount of fluid condensed on the substrate, with an exponent {epsilon} = -1.5. These results are in qualitative agreement with previous experimental results using aerogel as the substrate. Our results also show that {epsilon} is a function of the fractal dimension, Df, and the random walk dimension, Dw of the aerogel, in contrast with previous theories.

  18. Rydberg States of Alkali Metal Atoms on Superfluid Helium Droplets - Theoretical Considerations

    NASA Astrophysics Data System (ADS)

    Pototschnig, Johann V.; Lackner, Florian; Hauser, Andreas W.; Ernst, Wolfgang E.

    2017-06-01

    The bound states of electrons on the surface of superfluid helium have been a research topic for several decades. One of the first systems treated was an electron bound to an ionized helium cluster. Here, a similar system is considered, which consists of a helium droplet with an ionized dopant inside and an orbiting electron on the outside. In our theoretical investigation we select alkali metal atoms (AK) as central ions, stimulated by recent experimental studies of Rydberg states for Na, Rb, and Cs attached to superfluid helium nanodroplets. Experimental spectra , obtained by electronic excitation and subsequent ionization, showed blueshifts for low lying electronic states and redshifts for Rydberg states. In our theoretical treatment the diatomic AK^+-He potential energy curves are first computed with ab initio methods. These potentials are then used to calculate the solvation energy of the ion in a helium droplet as a function of the number of atoms. Additional potential terms, derived from the obtained helium density distribution, are added to the undisturbed atomic pseudopotential in order to simulate a 'modified' potential felt by the outermost electron. This allows us to compute a new set of eigenstates and eigenenergies, which we compare to the experimentally observed energy shifts for highly excited alkali metal atoms on helium nanodroplets. A. Golov and S. Sekatskii, Physica B, 1994, 194, 555-556 E. Loginov, C. Callegari, F. Ancilotto, and M. Drabbels, J. Phys. Chem. A, 2011, 115, 6779-6788 F. Lackner, G. Krois, M. Koch, and W. E. Ernst, J. Phys. Chem. Lett., 2012, 3, 1404-1408 F. Lackner, G. Krois, M. Theisen, M. Koch, and W. E. Ernst, Phys. Chem. Chem. Phys., 2011, 13, 18781-18788

  19. Observation of superfluidity in solid helium and solid hydrogen

    NASA Astrophysics Data System (ADS)

    Clark, Anthony

    2006-03-01

    A torsional oscillator technique is used to search for non-classical rotational inertia of solid helium^1 and solid hydrogen. Several important experimental details already observed will be reviewed for both systems. Some of these include the transition temperature, supersolid fraction, and dependencies on oscillation speed and impurities. Comparisons will be made in order to demonstrate the similarities and/or differences between helium and hydrogen. With further work currently underway, we will also report on recent experimental progress. This work is done in collaboration with Eunseong Kim, Xi Lin and Moses Chan and is supported by the NSF under grant 0207071. [1] E. Kim and M. H. W. Chan, Nature 427, 225 (2004); Science 305, 1941(2004); J. Low Temp. Phys. 138, 859 (2005).

  20. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction

    NASA Astrophysics Data System (ADS)

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-01

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  1. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction

    PubMed Central

    2016-01-01

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules. PMID:27448887

  2. Electron diffraction of CBr4 in superfluid helium droplets: A step towards single molecule diffraction.

    PubMed

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-07-21

    We demonstrate the practicality of electron diffraction of single molecules inside superfluid helium droplets using CBr4 as a testing case. By reducing the background from pure undoped droplets via multiple doping, with small corrections for dimers and trimers, clearly resolved diffraction rings of CBr4 similar to those of gas phase molecules can be observed. The experimental data from CBr4 doped droplets are in agreement with both theoretical calculations and with experimental results of gaseous species. The abundance of monomers and clusters in the droplet beam also qualitatively agrees with the Poisson statistics. Possible extensions of this approach to macromolecular ions will also be discussed. This result marks the first step in building a molecular goniometer using superfluid helium droplet cooling and field induced orientation. The superior cooling effect of helium droplets is ideal for field induced orientation, but the diffraction background from helium is a concern. This work addresses this background issue and identifies a possible solution. Accumulation of diffraction images only becomes meaningful when all images are produced from molecules oriented in the same direction, and hence a molecular goniometer is a crucial technology for serial diffraction of single molecules.

  3. High-resolution electronic spectroscopy of the BODIPY chromophore in supersonic beam and superfluid helium droplets.

    PubMed

    Stromeck-Faderl, Anja; Pentlehner, Dominik; Kensy, Uwe; Dick, Bernhard

    2011-07-11

    We present the fluorescence excitation and dispersed emission spectra of the parent compound of the boron dipyrromethene (BODIPY) dye class measured in a supersonic beam and isolated in superfluid helium nanodroplets. The gas-phase spectrum of the isolated molecules displays many low-frequency transitions that are assigned to a symmetry-breaking mode with a strongly nonharmonic potential, presumably the out-of-plane wagging mode of the BF(2) group. The data are in good agreement with transition energies and Franck-Condon factors calculated for a double minimum potential in the upper electronic state. The corresponding transitions do not appear in the helium droplet. This is explained with the quasi-rigid first layer of helium atoms attached to the dopant molecule by van der Waals forces. The spectral characteristics are those of a cyanine dye rather than that of an aromatic chromophore. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Formation of cold ion-neutral clusters using superfluid helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Falconer, Travis M.; Lewis, William K.; Bemish, Raymond J.; Miller, Roger E.; Glish, Gary L.

    2010-05-01

    A strategy for forming and detecting cold ion-neutral clusters using superfluid helium nanodroplets is described. Sodium cations generated via thermionic emission are directed toward a beam of helium droplets that can also pick up neutral molecules and form a cluster with the captured Na+. The composition of the clusters is determined by mass spectrometric analysis following a desolvation step. It is shown that the polar molecules H2O and HCN are picked up and form ion-neutral clusters with sizes and relative abundances that are in good agreement with those predicted by the statistics used to describe neutral cluster formation in helium droplets. [Na(H2O)n]+ clusters containing six to 43 water molecules were observed, a size range of sodiated water clusters difficult to access in the gas phase. Clusters containing N2 were in lower abundance than expected, suggesting that the desolvation process heats the clusters sufficiently to dissociate those containing nonpolar molecules.

  5. The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

    NASA Astrophysics Data System (ADS)

    Zhelev, N.; Abhilash, T. S.; Smith, E. N.; Bennett, R. G.; Rojas, X.; Levitin, L.; Saunders, J.; Parpia, J. M.

    2017-07-01

    The influence of confinement on the phases of superfluid helium-3 is studied using the torsional pendulum method. We focus on the transition between the A and B phases, where the A phase is stabilized by confinement and a spatially modulated stripe phase is predicted at the A-B phase boundary. Here we discuss results from superfluid helium-3 contained in a single 1.08-μm-thick nanofluidic cavity incorporated into a high-precision torsion pendulum, and map the phase diagram between 0.1 and 5.6 bar. We observe only small supercooling of the A phase, in comparison to bulk or when confined in aerogel, with evidence for a non-monotonic pressure dependence. This suggests that an intrinsic B-phase nucleation mechanism operates under confinement. Both the phase diagram and the relative superfluid fraction of the A and B phases, show that strong coupling is present at all pressures, with implications for the stability of the stripe phase.

  6. The A-B transition in superfluid helium-3 under confinement in a thin slab geometry

    PubMed Central

    Zhelev, N.; Abhilash, T. S.; Smith, E. N.; Bennett, R. G.; Rojas, X.; Levitin, L.; Saunders, J.; Parpia, J. M.

    2017-01-01

    The influence of confinement on the phases of superfluid helium-3 is studied using the torsional pendulum method. We focus on the transition between the A and B phases, where the A phase is stabilized by confinement and a spatially modulated stripe phase is predicted at the A–B phase boundary. Here we discuss results from superfluid helium-3 contained in a single 1.08-μm-thick nanofluidic cavity incorporated into a high-precision torsion pendulum, and map the phase diagram between 0.1 and 5.6 bar. We observe only small supercooling of the A phase, in comparison to bulk or when confined in aerogel, with evidence for a non-monotonic pressure dependence. This suggests that an intrinsic B-phase nucleation mechanism operates under confinement. Both the phase diagram and the relative superfluid fraction of the A and B phases, show that strong coupling is present at all pressures, with implications for the stability of the stripe phase. PMID:28671184

  7. Towards the in-situ detection of a single He2 * excimer in superfluid helium

    NASA Astrophysics Data System (ADS)

    Carter, Faustin; Hertel, Scott; Rooks, Michael; Prober, Daniel; McKinsey, Daniel

    2014-03-01

    Incident radiation can excite superfluid helium into a diatomic He2* excimer, which decays through the emission of a 15 eV photon. Such excimers have been used as tracers to measure the superfluid's quantum turbulence, thanks partly to the long half-life of the He2* triplet state (13 seconds). However, the efficient detection of these excimers remains a challenge. We present a detector capable of in-situ detection of the He2* excimers either directly (the excimer collides with the detector), or by collecting the 15 eV photon emission upon decay. This detector is based on a tungsten superconducting transition edge sensor and is designed to operate near 100 mK in a dilution refrigerator. We will discuss operating characteristics and present preliminary data with an aim towards the detection of a single excimer.

  8. Single-Photon-Sensitive Superconducting TES Sensors for EUV Photons in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Carter, Faustin; Hertel, Scott; Prober, Daniel; McKinsey, Daniel

    2013-03-01

    Incident radiation can excite superfluid helium into a diatomic He2* excimer, which decays through the emission of a 15 eV photon. Such excimers have been used as tracers to measure the superfluid's quantum turbulence, thanks partly to the long half-life of the He2* triplet state (~13 seconds). However, the efficient detection of these excimers remains a challenge. This work presents two different detector designs capable of in-situ detection of the He2* excimers either directly, or by collecting the 15 eV emission upon decay. Both detectors are based on the superconducting transition edge sensor. One is designed to operate near 2 K, while the other is designed for ~100 mK operation in a dilution refrigerator. We will discuss operating characteristics of both, and present preliminary data from the 2 K detector.

  9. Thermodynamics and Zero Sound Properties of Superfluid HELIUM-3

    NASA Astrophysics Data System (ADS)

    Israelsson, Ulf Egil

    The phase diagram of the A(,1) phase of superfluid ('3)He was deter- mined using zero sound as a detector. Measurements were done for pressures between 0 bar and 33 bar, and in magnetic fields up to 3 Tesla. From these measurements we obtain new information about certain parameters in the Ginzburg-Landau free energy expansion. The up splitting (T(,1)-T(,c))/H is found to decrease from a value of 40.7 (mu)K/T at 33 bar to 7.1 (mu)K/T at 0 bar. The up/down ratio -(T(,1)-T(,c))/(T(,2)-T(,c)), which is solely determined by strong coupling corrections, is found to decrease from 1.74 at 33 bar to the weak coupling value 1.0 at zero bar. Measurements of the clapping mode frequency (omega)(,cL ) in the A(,1) and A(,2) phases were performed at pressures from 11 bar to 33 bar using a sound frequency of 21.3 MHz. The ratio (omega)(,cL)/(DELTA)(,0), where (DELTA)(,0) is the maximum amplitude of the energy gap, is found to be substantially smaller than the value 1.23 expected for the pure p-wave axial state. We show that this ratio is lowered by finite f-wave pair interactions and obtain agreement with our experiment if the ratio of the f-wave to p-wave coupling strength is V(,3)/V(,1) (DBLTURN) 0.8. Experimental attenuation versus temperature line shapes are compared to the p-wave theory of Wolfle and Koch, which includes the effects of collisions. We find that the experiment shows progres- sively more excess attenuation as the pressure is reduced. It is not clear if allowing for a finite f-wave interaction into the theory of Wolfle and Koch will bring it closer to experiment. We also see more excess attenuation in the A(,1) phase than in the A(,2) phase. A possible expla- nation for this could be that there exists a small interaction between the up and down spin Cooper pairs. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089 -0182.).

  10. A superconductor to superfluid phase transition in liquid metallic hydrogen.

    PubMed

    Babaev, Egor; Sudbø, Asle; Ashcroft, N W

    2004-10-07

    Although hydrogen is the simplest of atoms, it does not form the simplest of solids or liquids. Quantum effects in these phases are considerable (a consequence of the light proton mass) and they have a demonstrable and often puzzling influence on many physical properties, including spatial order. To date, the structure of dense hydrogen remains experimentally elusive. Recent studies of the melting curve of hydrogen indicate that at high (but experimentally accessible) pressures, compressed hydrogen will adopt a liquid state, even at low temperatures. In reaching this phase, hydrogen is also projected to pass through an insulator-to-metal transition. This raises the possibility of new state of matter: a near ground-state liquid metal, and its ordered states in the quantum domain. Ordered quantum fluids are traditionally categorized as superconductors or superfluids; these respective systems feature dissipationless electrical currents or mass flow. Here we report a topological analysis of the projected phase of liquid metallic hydrogen, finding that it may represent a new type of ordered quantum fluid. Specifically, we show that liquid metallic hydrogen cannot be categorized exclusively as a superconductor or superfluid. We predict that, in the presence of a magnetic field, liquid metallic hydrogen will exhibit several phase transitions to ordered states, ranging from superconductors to superfluids.

  11. A PISO-like algorithm to simulate superfluid helium flow with the two-fluid model

    NASA Astrophysics Data System (ADS)

    Soulaine, Cyprien; Quintard, Michel; Allain, Hervé; Baudouy, Bertrand; Van Weelderen, Rob

    2015-02-01

    This paper presents a segregated algorithm to solve numerically the superfluid helium (He II) equations using the two-fluid model. In order to validate the resulting code and illustrate its potential, different simulations have been performed. First, the flow through a capillary filled with He II with a heated area on one side is simulated and results are compared to analytical solutions in both Landau and Gorter-Mellink flow regimes. Then, transient heat transfer of a forced flow of He II is investigated. Finally, some two-dimensional simulations in a porous medium model are carried out.

  12. Superfluid-helium-cooled rocket-borne far-infrared radiometer.

    PubMed

    Blair, A G; Edeskuty, F; Hiebert, R D; Jones, D M; Shipley, J P; Williamson, K D

    1971-05-01

    A far-infrared radiometer, cooled to 1.6 K by superfluid helium, has been flown in a Terrier-Sandhawk rocket. The instrument was designed to measure night-sky radiation in three wavelength passbands between 6 mm and 0.1 mm at altitudes between 120 km and 350 km. A failure in the rocket nose cone separation system prevented the measurement of this radiation, but the performance of the instrument during flight was generally satisfactory. Design features and operational characteristics of the cryogenic, optical, detection, and electronic systems are presented.

  13. Applicability of the Atkins model to the ion behavior in superfluid helium

    NASA Astrophysics Data System (ADS)

    Leiderer, P.; Shikin, V.

    2009-02-01

    The properties of ion clusters in superfluid helium are usually treated within the model proposed by Atkins (the snowball model). However, although a solid sphere of radius Ra around the seed ion can actually exist, it is vitally important to which extent it really governs the scattering mechanisms of various thermal excitations at the cluster. Detailed analysis of available data on the phonon as well as the impurity and Stokes mobilities reveals that the true unifying factor in the discussed picture is a power-law density enhancement in the vicinity of the seed charged particle caused by the polarization forces rather than the radius Ra

  14. Parametric self-enhancement of the spontaneous decay of sound in superfluid helium

    SciTech Connect

    Foster, J.S.; Putterman, S.

    1985-04-22

    The spontaneous decay of coherent monochromatic sound is dramatically self-enhanced by parametric amplification. We observed this effect for the first time with 3.25-GHz sound in superfluid helium at 85 mK. Starting with a typical intensity of 10 W/m/sup 2/ the sound beam is depleted by more than 99.9% over just 1 mm of propagation distance. In addition we observed, in contrast to Landau-Rumer processes, an exponential decay coefficient proportional to the square root of the initial intensity.

  15. SHOOT flowmeter and pressure transducers. [for Superfluid Helium On-Orbit Transfer system

    NASA Technical Reports Server (NTRS)

    Kashani, A.; Wilcox, R. A.; Spivak, A. L.; Daney, D. E.; Woodhouse, C. E.

    1990-01-01

    A venturi flowmeter has been designed and constructed for the Superfluid Helium On-Orbit Transfer (SHOOT) experiment. The calibration results obtained from the SHOOT venturi demonstrate the ability of the flowmeter to meet the requirements of the SHOOT experiment. Flow rates as low as 20 cu dm/h and as high as 800 cu dm/h have been measured. Performances of the SHOOT differential and absolute pressure transducers, which have undergone calibration and vibration tests, are also included. Throughout the tests, the responses of the transducers remained linear and repeatable to within + or - 1 percent of the full scales of the transducers.

  16. A study of the thermal conductivity of composite material Cu-epoxide resin at superfluid helium temperatures

    NASA Astrophysics Data System (ADS)

    Wang, H. L.; Wu, T. H.; Guo, F. Z.

    1994-02-01

    The influence of Kapitza thermal resistance of the composite material at superfluid helium temperatures is studied from the point of view of the heat transfer theory of cryogenics. A numerical model is developed for calculating the effective thermal conductivity coefficient of Cu-epoxide resin with the wires arranged in a square or crosswise. Experimental investigations have also been made at superfluid helium temperatures. The effective thermal conductivity coefficient of this kind of composite material measured by experiment is λ e=0.5929W/m·K.

  17. Optomechanics in superfluid helium coupled to a fiber-based cavity

    NASA Astrophysics Data System (ADS)

    Kashkanova, A. D.; Shkarin, A. B.; Brown, C. D.; Flowers-Jacobs, N. E.; Childress, L.; Hoch, S. W.; Hohmann, L.; Ott, K.; Reichel, J.; Harris, J. G. E.

    2017-03-01

    Presented in this paper are measurements of an optomechanical device in which various acoustic modes of a sample of superfluid helium couple to a fiber-based optical cavity. In contrast with recent work on the paraxial acoustic mode confined by the cavity mirrors (Kashkanova et al Nat. Phys. 2016 (https://doi.org/10.1038/NPHYS3900)), we focus specifically on the acoustic modes associated with the helium surrounding the cavity. This paper provides a framework for understanding how the acoustic modes depend on device geometry. The acoustic modes are observed using the technique of optomechanically induced transparency/amplification. The optomechanical coupling to these modes is found to be predominantly photothermal.

  18. A Report on Superfluid Helium Flow Through Porous Plugs for Space Science Applications

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1983-01-01

    As a background for the study of the nature of superfluid helium flow through porous plugs for other space science uses, preliminary tests on various plugs of a given material, diameter, height, and filtration grade have been performed. Two characteristics of the plugs, pore size and number of channels, have been determined by the bubble test and warm flow test of helium gas through the plugs, respectively. Tests on the flow of He II through the plugs have also been performed. An obvious feature of the results of these tests is that for isothermal measurements of pressure versus mass flow rate below approximately 2.10 K, the flow is separated into two different regimes, indicative of the occurrence of a critical phenomenon.

  19. A Report on Superfluid Helium Flow Through Porous Plugs for Space Science Applications

    NASA Technical Reports Server (NTRS)

    Mason, F. C.

    1983-01-01

    As a background for the study of the nature of superfluid helium flow through porous plugs for other space science uses, preliminary tests on various plugs of a given material, diameter, height, and filtration grade have been performed. Two characteristics of the plugs, pore size and number of channels, have been determined by the bubble test and warm flow test of helium gas through the plugs, respectively. Tests on the flow of He II through the plugs have also been performed. An obvious feature of the results of these tests is that for isothermal measurements of pressure versus mass flow rate below approximately 2.10 K, the flow is separated into two different regimes, indicative of the occurrence of a critical phenomenon.

  20. Hyperfine structure measurement of 87Rb atoms injected into superfluid helium as highly energetic ion beam

    NASA Astrophysics Data System (ADS)

    Imamura, Kei; Furukawa, Takeshi; Yang, Xiaofei; Fujita, Tomomi; Wakui, Takashi; Mitsuya, Yousuke; Hayasaka, Miki; Ichikawa, Yuichi; Hatakeyama, Atsushi; Kobayashi, Tohru; Odashima, Hitoshi; Ueno, Hideki; Matsuo, Yukari; Orochi Collaboration

    2014-09-01

    We have developed a new nuclear laser spectroscopy technique that is called OROCHI (Optical RI-atoms Observation in Condensed Helium as Ioncatcher). In OROCHI, highly energetic ion beam is injected into superfluid helium (He II) and is trapped as atoms. Hyperfine structure (HFS) and Zeeman splitting of trapped atoms is measured using laser-microwave (MW)/radiofrequency (RF) double resonance method. We deduce nuclear moments and spin values from the measured splittings, respectively So far, we measured Zeeman splitting of 84-87Rb atoms To evaluate the validity of the OROCHI method, it is necessary to investigate the following two points not only for Zeeman but also for HFS splitings. (i) What is the accuracy in frequency in our measurement? (ii) How high beam intensity is necessary to observe resonance spectra? For this purpose we conducted online experiment using 87Rb beam and measured the HFS splitting of injected 87Rb atoms in He II.

  1. Superfluid Brillouin optomechanics

    NASA Astrophysics Data System (ADS)

    Kashkanova, A. D.; Shkarin, A. B.; Brown, C. D.; Flowers-Jacobs, N. E.; Childress, L.; Hoch, S. W.; Hohmann, L.; Ott, K.; Reichel, J.; Harris, J. G. E.

    2017-01-01

    Optomechanical systems couple an electromagnetic cavity to a mechanical resonator which typically is a solid object. The range of phenomena accessible in these systems depends on the properties of the mechanical resonator and on the manner in which it couples to the cavity fields. In both respects, a mechanical resonator formed from superfluid liquid helium offers several appealing features: low electromagnetic absorption, high thermal conductivity, vanishing viscosity, well-understood mechanical loss, and in situ alignment with cryogenic cavities. In addition, it offers degrees of freedom that differ qualitatively from those of a solid. Here, we describe an optomechanical system consisting of a miniature optical cavity filled with superfluid helium. The cavity mirrors define optical and mechanical modes with near-perfect overlap, resulting in an optomechanical coupling rate ~3 kHz. This coupling is used to drive the superfluid and is also used to observe the thermal motion of the superfluid, resolving a mean phonon number as low as eleven.

  2. Andreas Acrivos Dissertation Prize Lecture: Quantum Mechanics meets Fluid Dynamics: Visualization of Vortex Reconnection in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Paoletti, Matthew

    2010-11-01

    Long-range quantum order underlies a number of related physical phenomena including superfluidity, superconductivity and Bose-Einstein condensation. While superfluidity in helium-4 was one of the earliest discovered, it is not the best understood, owing to the strong interactions present (making theoretical progress difficult) and the lack of local experimental probes. Quantum fluids, such as superfluid helium-4, are typically described as a mixture of two interpenetrating fluids with distinct velocity fields: a viscous normal fluid akin to water and an inviscid superfluid exhibiting long-range quantum order. In this "two-fluid model," there is no conventional viscous dissipation in the superfluid component and vorticity is confined to atomically-thin vortices with quantized circulation. Turbulence may occur in either fluid component with turbulence in the superfluid exhibiting a complex tangle of quantized vortices, as first envisioned by Feynman. Approximately five years ago, our group discovered that micron-sized hydrogen particles may be used for flow visualization in superfluid helium-4. The particles can trace the motions of the normal fluid or be trapped by the quantized vortices, which enables one to characterize the dynamics of both the normal fluid and superfluid components for the first time. By directly observing and tracking these particles, we have directly confirmed the two-fluid model, observed vortex rings and quantized vortex reconnection, characterized thermal counterflows, and observed the very peculiar nature of quantum turbulence. One of many surprising observations is the existence of power-law tails in the probability distribution of velocities in quantum turbulence, which are in stark contrast to the Gaussian distributions typical of classical fluid turbulence.

  3. Universality of the Phonon-Roton Spectrum in Liquids and Superfluidity of 4He

    NASA Astrophysics Data System (ADS)

    Bobrov, Viktor; Trigger, Sergey; Litinski, Daniel

    2016-06-01

    Based on numerous experimental data on inelastic neutron and X-ray scattering in liquids, we assert that the phonon-roton spectrum of collective excitations, predicted by Landau for superfluid helium, is a universal property of the liquid state. We show that the existence of the roton minimum in the spectrum of collective excitations is caused by the short-range order in liquids. Using the virial theorem, we assume that one more branch of excitations should exist in He II, whose energy spectrum differs from the phonon-roton spectrum. Such excitations are associated with the pole of single-particle Green function, which can have a gap at small values of momenta.

  4. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Zhang, Jie; Freund, William M.; Kong, Wei

    2015-07-01

    We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs+ is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs+-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 106 helium atoms when the source temperature is between 14 K and 17 K.

  5. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets

    SciTech Connect

    Chen, Lei; Zhang, Jie; Freund, William M.; Kong, Wei

    2015-07-28

    We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs{sup +} is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs{sup +}-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10{sup 6} helium atoms when the source temperature is between 14 K and 17 K.

  6. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets.

    PubMed

    Chen, Lei; Zhang, Jie; Freund, William M; Kong, Wei

    2015-07-28

    We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs(+) is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs(+)-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 10(6) helium atoms when the source temperature is between 14 K and 17 K.

  7. Effect of kinetic energy on the doping efficiency of cesium cations into superfluid helium droplets

    PubMed Central

    Chen, Lei; Zhang, Jie; Freund, William M.; Kong, Wei

    2015-01-01

    We present an experimental investigation of the effect of kinetic energy on the ion doping efficiency of superfluid helium droplets using cesium cations from a thermionic emission source. The kinetic energy of Cs+ is controlled by the bias voltage of a collection grid collinearly arranged with the droplet beam. Efficient doping from ions with kinetic energies from 20 eV up to 480 V has been observed in different sized helium droplets. The relative ion doping efficiency is determined by both the kinetic energy of the ions and the average size of the droplet beam. At a fixed source temperature, the number of doped droplets increases with increasing grid voltage, while the relative ion doping efficiency decreases. This result implies that not all ions are captured upon encountering with a sufficiently large droplet, a deviation from the near unity doping efficiency for closed shell neutral molecules. We propose that this drop in ion doping efficiency with kinetic energy is related to the limited deceleration rate inside a helium droplet. When the source temperature changes from 14 K to 17 K, the relative ion doping efficiency decreases rapidly, perhaps due to the lack of viable sized droplets. The size distribution of the Cs+-doped droplet beam can be measured by deflection and by energy filtering. The observed doped droplet size is about 5 × 106 helium atoms when the source temperature is between 14 K and 17 K. PMID:26233132

  8. Nucleation of bubbles in liquid helium

    SciTech Connect

    Maris, H.J. ); Balibar, S.; Pettersen, M.S. )

    1993-12-01

    The authors give a brief survey of experiments that have been performed to study the nucleation of bubbles (cavitation) in liquid helium at negative pressures. There have been two principal motivations for research in this field. Because all impurities (except [sup 3]He) freeze out of the liquid at low temperatures, it is possible to prepare helium with a much higher purity than ordinary classical liquids. In any study of a nucleation process this is an important advantage because impurities introduce the complication of heterogeneous nucleation. The second reason for interest in helium is that at low enough temperatures nucleation is expected to be dominated by quantum tunnelling rather than thermal activation.

  9. Stability and structure of nanowires grown from silver, copper and their alloys by laser ablation into superfluid helium.

    PubMed

    Gordon, Eugene; Karabulin, Alexander; Matyushenko, Vladimir; Sizov, Vyacheslav; Khodos, Igor

    2014-12-14

    Nanowires with 5 nm diameter made of silver, copper, and their alloys were grown in superfluid helium. The silver nanowires being heated to 300 K disintegrated into individual clusters. In contrast, copper nanowires were stable at room temperature, and nanowires made of alloys were also stable despite their low melting temperature.

  10. Pressure driven flows of superfluid helium-4 through a single nanopipe

    NASA Astrophysics Data System (ADS)

    Velasco, Angel; Siwy, Zuzanna; Taborek, Peter

    2015-03-01

    We have measured flow rates of helium-4 through a single etched nanopore of 31 nm diameter in mica with a mass spectrometer. Flow rates were measured as a function of pressure at constant temperature and at saturated vapor pressures along the coexistence curve between 0.5 K and 3.5 K. Due to the constraint of the mass spectrometer the low pressure side was maintained at P =0 creating an intrinsic superfluid/vapor interface which forms inside the pipe or at its exit. We observed two flow regimes at low temperatures with velocities in the range of 6 and 11 m/s consistent with Feynman's vortex critical velocity and a thermal vortex nucleation model respectively. The velocity in a laminar, viscous flow is proportional to the pressure drop while in superfluid flows to zeroth order the velocity is independent of the pressure. A first order correction shows a linear dependence on the pressure with the slope continuously varying from a positive to a negative value near the lambda point. We have also measured flow rates in the normal state and found rates in exact agreement with conventional viscous theory that incorporates the Laplace pressure and a zero slip length. Supported by NSF DMR-0907495.

  11. Ultracold neutron accumulation in a superfluid-helium converter with magnetic multipole reflector

    NASA Astrophysics Data System (ADS)

    Zimmer, O.; Golub, R.

    2015-07-01

    We analyze the accumulation of ultracold neutrons (UCNs) in a superfluid-helium converter vessel surrounded by a magnetic multipole reflector. We solved the spin-dependent rate equation, employing formulas valid for adiabatic spin transport of trapped UCNs in mechanical equilibrium. Results for saturation UCN densities are obtained in dependence of order and strength of the multipolar field. The addition of magnetic storage to neutron optical potentials can increase the density and energy of the low-field-seeking UCNs produced and serves to mitigate the effects of wall losses on the source performance. It also can provide a highly polarized sample of UCNs without need to polarize the neutron beam incident on the converter. This work was performed in preparation of the UCN source project SuperSUN at the Institut Laue-Langevin.

  12. Argon Nanoclusters with Fivefold Symmetry in Supersonic Gas Jets and Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Danylchenko, O. G.; Boltnev, R. E.; Khmelenko, V. V.; Kiryukhin, V.; Konotop, O. P.; Lee, D. M.; Krainyukova, N. V.

    2017-04-01

    In this study argon nanoclusters (800 to ˜ 6500 atoms) formed in supersonic gas jets are compared to the nanoclusters stabilized in superfluid helium. High-energy electron and X-ray diffraction methods are utilized. Both techniques allow investigation of isolated clusters. It is shown that the theoretical prediction of the so-called multiply twinned particles with fivefold symmetry, such as icosahedra (ico) and decahedra (dec) is valid in the investigated cluster size interval. Around the point of the expected ico-to-dec size-dependent transformation at a cluster size of ˜ 2000 atoms, hexagonal ico and the statistical distribution of structures with a tendency for dec to replace ico are observed. Kinetic reasons, as well as temperature-related effects, could be responsible for the latter observations.

  13. Formation of bimetallic clusters in superfluid helium nanodroplets analysed by atomic resolution electron tomography

    PubMed Central

    Haberfehlner, Georg; Thaler, Philipp; Knez, Daniel; Volk, Alexander; Hofer, Ferdinand; Ernst, Wolfgang E.; Kothleitner, Gerald

    2015-01-01

    Structure, shape and composition are the basic parameters responsible for properties of nanoscale materials, distinguishing them from their bulk counterparts. To reveal these in three dimensions at the nanoscale, electron tomography is a powerful tool. Advancing electron tomography to atomic resolution in an aberration-corrected transmission electron microscope remains challenging and has been demonstrated only a few times using strong constraints or extensive filtering. Here we demonstrate atomic resolution electron tomography on silver/gold core/shell nanoclusters grown in superfluid helium nanodroplets. We reveal morphology and composition of a cluster identifying gold- and silver-rich regions in three dimensions and we estimate atomic positions without using any prior information and with minimal filtering. The ability to get full three-dimensional information down to the atomic scale allows understanding the growth and deposition process of the nanoclusters and demonstrates an approach that may be generally applicable to all types of nanoscale materials. PMID:26508471

  14. Structure and Properties of Platinum, Gold and Mercury Nanowires Grown in Superfluid Helium.

    PubMed

    Gordon, Eugene B; Karabulin, Alexander V; Morozov, Andrey A; Matyushenko, Vladimir I; Sizov, Vyacheslav D; Khodos, Igor I

    2014-04-03

    Webs consisting of nanowires made of gold, platinum and mercury were produced by the technique based on laser ablation of metals inside superfluid helium. Their morphology and structure as well as their electrical conductivity have been studied. Diameters of gold and platinum nanowires are 4.5 and 3 nm, respectively. Fortunately, they are close to diameters of nanospheres made of these metals, which, as known from the literature, possess anomalous catalytic activity. Web resistivities for all metals up to room temperature are controlled by conductive electron scattering on a wire surface, thus they are almost independent of T. Nanowires in the webs are electrically interconnected, and therefore the web can be used as a catalyst without any support. Possible advantages of this type of nanocatalyst are outlined.

  15. Formation of bimetallic clusters in superfluid helium nanodroplets analysed by atomic resolution electron tomography

    NASA Astrophysics Data System (ADS)

    Haberfehlner, Georg; Thaler, Philipp; Knez, Daniel; Volk, Alexander; Hofer, Ferdinand; Ernst, Wolfgang E.; Kothleitner, Gerald

    2015-10-01

    Structure, shape and composition are the basic parameters responsible for properties of nanoscale materials, distinguishing them from their bulk counterparts. To reveal these in three dimensions at the nanoscale, electron tomography is a powerful tool. Advancing electron tomography to atomic resolution in an aberration-corrected transmission electron microscope remains challenging and has been demonstrated only a few times using strong constraints or extensive filtering. Here we demonstrate atomic resolution electron tomography on silver/gold core/shell nanoclusters grown in superfluid helium nanodroplets. We reveal morphology and composition of a cluster identifying gold- and silver-rich regions in three dimensions and we estimate atomic positions without using any prior information and with minimal filtering. The ability to get full three-dimensional information down to the atomic scale allows understanding the growth and deposition process of the nanoclusters and demonstrates an approach that may be generally applicable to all types of nanoscale materials.

  16. Superfluid-Helium Converter for Accumulation and Extraction of Ultracold Neutrons

    SciTech Connect

    Zimmer, O.; Baumann, K.; Fertl, M.; Franke, B.; Wirth, H.-F.; Mironov, S.; Plonka, C.; Rich, D.; Schmidt-Wellenburg, P.; Brandt, B. van den

    2007-09-07

    We report the first successful extraction of accumulated ultracold neutrons (UCN) from a converter of superfluid helium, in which they were produced by downscattering neutrons of a cold beam from the Munich research reactor. Windowless UCN extraction is performed in vertical direction through a mechanical cold valve. This prototype of a versatile UCN source is comprised of a novel cryostat designed to keep the source portable and to allow for rapid cooldown. We measured time constants for UCN storage and extraction into a detector at room temperature, with the converter held at various temperatures between 0.7 and 1.3 K. The UCN production rate inferred from the count rate of extracted UCN is close to the theoretical expectation.

  17. Production of ultrathin nanowires from refractory metals (Nb, Re, W, Mo) by laser ablation in superfluid helium

    NASA Astrophysics Data System (ADS)

    Gordon, E. B.; Karabulin, A. V.; Matyushenko, V. I.; Sizov, V. D.; Khodos, I. I.

    2015-09-01

    The ablation of targets in superfluid helium with a short-pulse laser allows introducing into liquid the atoms and small clusters of any metal. The metal is then concentrated in the core of 1D quantized vortices nucleating in the laser focus and expanding into the liquid. Subsequent metal coagulation within the vortex results in the formation of thin nanowires with perfect shape and structure. For refractory metals these wires are expected to be especially thin. The diameters of nanowires grown from niobium, molybdenum and tungsten are indeed 4.0, 2.0 and 2.5 nm, respectively. Unfortunately, under ablation of unannealed rhenium the main product is flat ‘flakes’ having irregular shape and 20-50 nm size. Short nanowires (with a 1.5 nm diameter) were present in small amounts. The wires produced by this method contain no additional impurities and have a free lateral surface. By using a diode-pumped Nd:LSB microlaser (1.06 μm wavelength, 0.4 ns pulse duration, 100 μJ pulse energy and 4 kHz repetition rate) the amounts of nanoweb sufficient for many physical and chemical applications could be produced in a single low-temperature experiment. Ultrathin wires of molybdenum and tungsten show promise for creating ‘cold’ cathodes whereas a niobium nanoweb should be an excellent catalyst.

  18. Self-trapping of electrons in vortex rings in liquid helium

    NASA Astrophysics Data System (ADS)

    Khrapak, A. G.; Bronin, S. Ya.

    2017-06-01

    A model according to which "fast" and "exotic" negative ions in superfluid helium are the localized states of electrons in vortex rings has been presented. The quantization of radial and longitudinal motions of electrons inside the vortex core and the quantization of the vortex motion of liquid helium lead to the existence of a whole family of excited states of electron vortices, in qualitative agreement with the experiments on the mobility of exotic ions. The possibility of the verification of conclusions of the model in optical experiments has been considered.

  19. GIRL cryotechnics and preparation of a TEXUS experiment on superfluid helium dynamics

    NASA Astrophysics Data System (ADS)

    Denner, Hans-Dietrich; Gradt, Thomas; Klipping, Gustav; Klipping, Ingrid; Ruppert, Udo; Szuecs, Zsolt; Walter, Harry

    1987-11-01

    Technological requirements for the handling of superfluid He2 at zero-g in the German infrared telescope GIRL (Refrigerated Infrared Laboratory) are analyzed. The separation of gas and liquid phase, temperature control, and heat transfer during the continuous evaporation of the coolant are studied. An active phase separator together with the necessary cryocomponents, displacement transducer, actuator, and penetration cables are developed. The system is tested under critical laboratory conditions and on zero-g flights under variation of the acceleration between 2g and 0g. By integrating different safety circuits the reliability of the system is achieved.

  20. Performance of all-metal demountable cryogenic seals at superfluid helium temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, Louis J.; Spivak, Alan L.; Kittel, Peter

    1989-01-01

    Two all-metal demountable cryogenic seals with an outside diameter of 36.6 mm, inside diameter of 27.2 mm, and thickness of 0.51 mm were leak-tested at room temperature (300 K), liquid nitrogen temperature (21 cycles at 77 K), liquid helium temperature (9 cycles at 4.2 K), and susperfluid helium temperature (4 cycles at 1.6 K). Each seal was mounted and demounted for 13 cycles. Thickness measurements at 90 deg intervals along the circumference showed a maximum seal compression of 0.038 mm. Leak-rate measurements at all temperatures showed no detectable leak above the helium background level, typically 0.1 x 10(-9) std-cc/sec, during testing.

  1. Electric breakdown and ionization detection in normal liquid and superfluid 4He for the SNA nEDM experiment

    NASA Astrophysics Data System (ADS)

    Karcz, Maciej

    Helium throughout the pressure-temperature phase space, between 1 bar and the saturation curve and between 4.2 K and 1.7 K. A new breakdown hysteresis in liquid helium was discovered and is attributed to the suppression of heterogeneous nucleation sites inside the liquid. A phenomenological model involving the Townsend breakdown mechanism and Paschen's Law in liquid helium is proposed. In addition, the many challenges faced by efficient scintillation detection in the cryogenic environment of the nEDM experiment motivated additional studies at CEEM. To test the effect of an electric field on scintillation in superfluid, a SF test cell was constructed inside a dilution refrigerator and it was found that the scintil- lation intensity from a 241Am source in the cell, is reduced at high electric fields. Alternatives to scintillation detection for the nEDM experiment were also explored and the test cell was reconfigured to operate as a superfluid ionization chamber. The superfluid ionization chamber was tested with 241Am in pulse mode and current mode configurations. While the pulse mode in superfluid, which relies on the drift velocity of charges, is hindered by quasi-particle excitations in superfluid, results of current mode measurements appear promising. To further explore the prospect of cryogenic ionization detection, a detector cryo-stat capable of detecting neutrons using a 10B converter was also constructed at CEEM and tested at the Indiana University Low Energy Neutron Source (LENS). The neutron detector cryostat has the benefit of being able to modulate the ioniza- tion source which was not possible with the superfluid ionization chamber. Tests with argon gas led to the development of more efficient boron targets. The cryogenic test of ionization detection in current mode will be discussed.

  2. Chemical reactions studied at ultra-low temperature in liquid helium clusters

    SciTech Connect

    Huisken, Friedrich; Krasnokutski, Serge A.

    2012-11-27

    Low-temperature reaction rates are important ingredients for astrophysical reaction networks modeling the formation of interstellar matter in molecular clouds. Unfortunately, such data is difficult to obtain by experimental means. In an attempt to study low-temperature reactions of astrophysical interest, we have investigated relevant reactions at ultralow temperature in liquid helium droplets. Being prepared by supersonic expansion of helium gas at high pressure through a nozzle into a vacuum, large helium clusters in the form of liquid droplets constitute nano-sized reaction vessels for the study of chemical reactions at ultra-low temperature. If the normal isotope {sup 4}He is used, the helium droplets are superfluid and characterized by a constant temperature of 0.37 K. Here we present results obtained for Mg, Al, and Si reacting with O{sub 2}. Mass spectrometry was employed to characterize the reaction products. As it may be difficult to distinguish between reactions occurring in the helium droplets before they are ionized and ion-molecule reactions taking place after the ionization, additional techniques were applied to ensure that the reactions actually occurred in the helium droplets. This information was provided by measuring the chemiluminescence light emitted by the products, the evaporation of helium atoms by the release of the reaction heat, or by laser-spectroscopic identification of the reactants and products.

  3. Nonlinear Interaction of Zero Sound with the Order Parameter Collective Modes in Superfluid HELIUM-3-BORON.

    NASA Astrophysics Data System (ADS)

    McKenzie, Ross Hugh

    A brief overview of past experimental and theoretical investigations of the linear and nonlinear interaction of zero sound with the order parameter collective modes in superfluid ^3He-B is given before introducing the quasiclassical (QC) theory of superfluid ^3He. A new approach to calculating the linear and nonlinear response is presented. The QC propagator is calculated by expanding the low energy Dyson's equation in powers of the nonequilibrium self energy. The expression given for the expansion coefficients, involving products of pairs of equilibrium Green's functions, has a simple diagrammatic representation, and establishes a connection between the QC theory and other theoretical formalisms which have been used to investigate the collective modes. It is shown that the expansion coefficients satisfy Onsager-like relations and some identities required by gauge and galilean invariance. Consequently, this new approach to deriving dynamical equations for the collective modes is more efficient and transparent than solving the QC transport equations. This new approach is used to investigate the linear coupling of zero sound to the order parameter collective modes in weakly inhomogeneous superfluid ^3 He. It makes tractable the treatment of (nonlinear) parametric processes involving zero sound and the collective modes. It is shown that the approximate particle-hole symmetry of the ^3He Fermi liquid determines important selection rules for nonlinear acoustic processes, just as it is well known to do for linear processes. Analogues with nonlinear optics guide the derivation, solution and interpretation of the dynamical equations for a three-wave resonance between two zero sound waves and the J = 2 ^+ order parameter collective mode. It is shown that stimulated Raman scattering and two phonon absorption of zero sound by the J = 2^+ collective mode should be observable when the pump sound wave has energy density larger than about one percent of the superfluid

  4. Implementation of the superfluid helium phase transition using finite element modeling: Simulation of transient heat transfer and He-I/He-II phase front movement in cooling channels of superconducting magnets

    NASA Astrophysics Data System (ADS)

    Bielert, E. R.; Verweij, A. P.; Ten Kate, H. H. J.

    2013-01-01

    In the thermal design of high magnetic field superconducting accelerator magnets, the emphasis is on the use of superfluid helium as a coolant and stabilizing medium. The very high effective thermal conductivity of helium below the lambda transition temperature significantly helps to extract heat from the coil windings during steady state and transient heat deposition. The layout and size of the helium channels have a strong effect on the maximum amount of heat that can be extracted from the porously insulated superconducting cables. To better understand the behavior of superfluid helium penetrating the magnet structure and coil windings, simulation based on a three dimensional finite element model can give valuable insight. The 3D geometries of interest can be regarded as a complex network of coupled 1D geometries. The governing physics is thus similar for both geometries and therefore validation of several and different 1D models is performed. Numerically obtained results and published experimental data are compared. Once the viability of the applied methods is proven, they can be incorporated into the 3D geometries. Not only the transport properties in the bulk of the helium are of interest, but also the strong non-linear behavior at the interfaces between solids and superfluid helium (Kapitza conductance) is important from an engineering point of view, since relatively large temperature jumps may occur here. In this work it is shown how He-II behavior in magnet windings can be simulated using COMSOL Multiphysics. 1D models are validated by experimental results taken from literature in order to improve existing 2D and 3D models with more complete physics. The examples discussed include transient heat transfer in 1D channels, Kapitza conductance and sub-cooling of normal liquid helium to temperatures below the lambda transition in long channels (phase front movement).

  5. Liquid helium pumps for in-orbit transfer

    NASA Technical Reports Server (NTRS)

    Kittel, P.

    1986-01-01

    Both mechanical and fountain-effect pumps are being considered for use in the in-orbit resupply of superfluid helium to a number of scientific instrument systems. This paper presents a review of the operating characteristics of these pumps. Particular emphasis will be given to the different methods of evaluating the efficiency of these pumps and their effectiveness in a transfer system.

  6. Magnetic Levitation and Noncoalescence of Liquid Helium

    SciTech Connect

    Weilert, M.; Whitaker, D.; Maris, H.; Seidel, G.

    1996-12-01

    We describe experiments in which drops of liquid helium-4, as large as 2cm in diameter, are magnetically levitated. We have found that, when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. It appears that this effect is caused by the slow evaporation of liquid from the drops. {copyright} {ital 1996 The American Physical Society.}

  7. Liquid vapour spinodal of pure helium 4

    NASA Astrophysics Data System (ADS)

    Imre, Attila R.; Kraska, Thomas

    2008-10-01

    Unlike gases, liquids can be overheated or stretched only up to a limit. The determination of the mean-field thermodynamic stability limit-the so-called spinodal-is a very difficult theoretical and a more-or-less impossible experimental task. Based on a recent semi-empirical method, the spinodal pressure of helium-4 at given temperature is determined, using liquid-vapour surface tension, interface thickness and vapour pressure data.

  8. Solvation of molecules in superfluid helium enhances the “interaction induced localization” effect

    SciTech Connect

    Walewski, Łukasz Forbert, Harald; Marx, Dominik

    2014-04-14

    Atomic nuclei become delocalized at low temperatures as a result of quantum effects, whereas they are point-like in the high temperature (classical) limit. For non-interacting nuclei, the delocalization upon lowering the temperature is quantitatively described in terms of the thermal de Broglie wavelength of free particles. Clearly, light non-interacting nuclei – the proton being a prominent one – are much more delocalized at low temperatures compared to heavy nuclei, such as non-interacting oxygen having water in mind. However, strong interactions due to chemical bonding in conjunction with ultra-low temperatures characteristic to superfluid helium nanodroplets change this common picture substantially for nuclei in molecules or clusters. It turns out that protons shared in hydrogen bonds undergo an extreme “interaction induced localization” at temperatures on the order of 1 K, which compresses the protonic spatial distributions to the size of the much heavier donor or acceptor atoms, such as O or Cl nuclei, corresponding to about 0.1% of the volume occupied by a non-interacting proton at the same temperature. Moreover, applying our recently developed hybrid ab initio path integral molecular dynamics/bosonic path integral Monte Carlo quantum simulation technique to a HCl/water cluster, HCl(H{sub 2}O){sub 4}, we find that helium solvation has a significant additional localizing effect of up to about 30% in volume. In particular, the solvent-induced excess localization is the stronger the lesser the given nucleus is already localized in the gas phase reference situation.

  9. Interaction-induced localisation of protons in hydrogen bonds at superfluid helium temperatures

    NASA Astrophysics Data System (ADS)

    Walewski, Łukasz; Forbert, Harald; Marx, Dominik

    2013-09-01

    It is common wisdom to expect that protons are more delocalised than much heavier nuclei due to quantum effects, for instance, in hydrogen bonds D-H⋆ ṡ ṡ ṡ A, where the shared proton H⋆ is suspended in between the donor and acceptor heavy sites. Here, we demonstrate that this simple quasi-classical perspective fails at sufficiently low temperatures as a result of intramolecular covalent bonding accompanied by the non-covalent intermolecular interactions which induce strong localisation in the deep quantum regime. Using the water dimer as well as H2O ṡ ṡ ṡ HCl as generic models, path integral simulations at temperatures characteristic to superfluid helium conditions (about 1 K) reveal that the shared proton in such hydrogen bonds gets extremely confined to a spatial region that is comparable to - or even smaller than - that of the heavy atoms. This counter-intuitive so-called interaction-induced localisation phenomenon is also effective for the heavier nuclei, although to a much lesser extent. It is the elevated temperature (about 100 K) that restores the familiar quasi-classical picture, in which atomic spread follows the usual mass dependence of de Broglie wavelength.

  10. TFCX-S toroidal field coil design using a superfluid helium-cooled winding

    SciTech Connect

    Kalsi, S.S.; Coffman, L.; Hooper, R.J.

    1983-01-01

    This paper discusses the design and performance of the toroidal field (TF) coils for one of the possible options for the Tokamak Fusion Core Experiment (TFCX). TFCX is a proposed long-pulse, ignited next-step tokamak to follow the Tokamak Fusion Test Reactor (TFTR). In the TFCX option considered here, designated TFCX-S, there are 16 superconducting TF coils which produce 4.3 T at a plasma major radius of 3.75 m. Each of the TF coils is rated at 5.06 MAT, and operates at a peak field of 9.8 T at the winding. Several winding/cooling approaches have been considered for the TFCX-S TF coils. A NbTi winding, cooled by superfluid helium (He/sub II/) at 1.8 K, is discussed here. The conductor is similar to that being developed by GA Technologies as part of the Department of Energy (DOE) 12 T conductor development program. Use of either sub-cooled atmospheric pressure He/sub II/ or saturated sub-atmospheric pressure He/sub II/ has been considered; both cooling schemes appear feasible.

  11. Flow visualization in superfluid helium-4 using a thin line of He2 excimer tracers

    NASA Astrophysics Data System (ADS)

    Marakov, Alex; Gao, Jian; Guo, Wei; van Sciver, Steven; Ihas, Gary; McKinsey, Daniel; Vinen, William

    2014-03-01

    Cryogenic flow visualization techniques have been proven in recent years to be a very powerful experimental method to study turbulence in superfluid helium-4 (He II). In order to extract quantitative information of the flow field, we developed a new technique based on the generation of a thin line of He2 excimer tracers via femtosecond-laser field ionization. These tracers move solely with the normal-fluid component in He II and can be imaged using a laser-induce fluorescence technique. Studying the drift and distortion of the tracer line in a turbulent flow shall allow us to measure the instantaneous flow velocity field and hence determine the structure functions and the energy spectrum of the turbulence. We discuss the preliminary results obtained that for the first time visually reveal the existence of a laminar-to-turbulent transition in the normal fluid in thermal counterflow. W.G. acknowledges the startup support from Florida State University and the National High Magnetic Field Laboratory.

  12. Design and Testing of a 2K Superfluid Helium Heat Station

    SciTech Connect

    William Hicks; Edward Daly; Joseph Preble; Mark Wiseman; Claus Rode

    2005-08-29

    Three transitional cryomodules (SL21, FEL03, Renascence) have been constructed as part of an energy upgrade effort at Thomas Jefferson National Accelerator Facility (JLab). Each transitional cryomodule contains eight superconducting radio-frequency (SRF) cavities. Within the vacuum vessel, waveguides transmit up to 13 kW of RF power to the superconducting niobium cavities. The waveguides also provide the thermal transition between the room temperature ceramic RF window and the niobium fundamental power coupler (FPC), a 300K temperature gradient across {approx}20cm. The thermal performance of the waveguides is determined in part by the placement of heat stations and bellows. The original 13 kW waveguide design incorporated a single 60 K heat station and two bellows resulting in a total heat load (static + dynamic) to the FPC of {approx}3W per waveguide. To minimize this heat load and stabilize the FPC temperatures, a 2K superfluid helium heat station design was incorporated into the second transitional cryomodule, FEL03, installed in the JLab Free Electron Laser (FEL). The designed heat station is capable of removing up to 1.12W, with a bath temperature of 2.05K, while remaining sub-lambda. This paper describes the design, analysis and testing of the heat station.

  13. A method for the three-dimensional simulation of superfluid helium

    SciTech Connect

    Bottura, L.; Darve, C.; Patankar, N.A.; Van Sciver, S.; /Natl. High Mag. Field Lab.

    2008-01-01

    Transport phenomena in superfluid helium can be described using the two-fluid Landau-Khalatnikov model and the Gorter-Mellink mutual friction. Here we discuss a mathematical formulation of the two-fluid model that uses macroscopic conservation balances of mass, momentum and energy of each species, and assumes local thermodynamic equilibrium. A particularity of this model is that it describes the state of He II as well as that of each of the two-fluid components in terms of pressure p and temperature T, which is convenient for stable numerical solution. The equations of the model form a system of partial differential equations (PDE) that can be written in matrix form for convenience. On this base, a three-dimensional numerical model using a complete and consistent, while still practical, system of PDEs was developed. In the form described, the PDE can be solved using three-dimensional Lagrangian finite element in space supplemented by a Beam-Warming time-2marching algorithm. Once validated, this solver will allow to simulate He II thermal counterflow applied to arbitrary geometry.

  14. Charge collection in Si detectors irradiated in situ at superfluid helium temperature

    NASA Astrophysics Data System (ADS)

    Verbitskaya, Elena; Eremin, Vladimir; Zabrodskii, Andrei; Dehning, Bernd; Kurfürst, Christoph; Sapinski, Mariusz; Bartosik, Marcin R.; Egorov, Nicolai; Härkönen, Jaakko

    2015-10-01

    Silicon and diamond detectors operated in a superfluid helium bath are currently being considered for the upgrade of the LHC beam loss monitoring system. The detectors would be installed in immediate proximity of the superconducting coils of the triplet magnets. We present here the results of the in situ irradiation test for silicon detectors using 23 GeV protons while keeping the detectors at a temperature of 1.9 K. Red laser (630 nm) Transient Current Technique and DC current measurements were used to study the pulse response and collected charge for silicon detectors irradiated to a maximum radiation fluence of 1×1016 p/cm2. The dependence between collected charge and irradiation fluence was parameterized using the Hecht equation and assumption of a uniform electric field distribution. The collected charge was found to degrade with particle fluence for both bias polarities. We observed that the main factor responsible for this degradation was related to trapping of holes on the donor-type radiation-induced defects. In contrast to expectations, along with formation of donors, acceptor-type defects (electron traps) are introduced into the silicon bulk. This suggests that the current models describing charge collection in irradiated silicon detectors require an extension for taking into account trapping at low temperatures with a contribution of shallow levels. New in situ irradiation tests are needed and planned now to extend statistics of the results and gain a deeper insight into the physics of low temperature detector operation in harsh radiation environment.

  15. Particle dynamics in wall-bounded thermal counterflow of superfluid helium

    NASA Astrophysics Data System (ADS)

    La Mantia, M.

    2017-06-01

    The motions of relatively small particles in wall-bounded thermal counterflow of superfluid helium are experimentally investigated, above 1 K, by using the particle tracking velocimetry technique. The effect of a solid boundary on this quantum flow has received little attention to date, and the focus here is on the corresponding flow-induced particle dynamics. The velocity and velocity difference statistical distributions of the particles are computed at length scales straddling two orders of magnitude across the mean distance between quantized vortices, the quantum length scale of the flow. The imposed counterflow velocity ranges between about 2 and 7 mm/s, resulting in suitably defined Reynolds numbers up to 20 000. The distributions are found to be wider in the bulk than close to the solid boundary, at small enough scales, and this suggests that the mean distance between the vortices increases with the distance from the wall. The outcome reinforces the view, supported to date solely by numerical simulations, that in thermal counterflow quantized vortices are not homogenously distributed in the channel and that they preferentially concentrate close to its walls. Boundary layers might therefore also exist in quantum flows, although some of their features appear to be significantly different from those attributed to wall-bounded flows of viscous fluids, due to the presence of quantized vortices.

  16. Particle trajectories in thermal counterflow of superfluid helium in a wide channel of square cross section

    SciTech Connect

    La Mantia, Marco

    2016-02-15

    The motion of micrometer-sized solid hydrogen particles in thermal counterflow of superfluid helium is studied experimentally by using the particle tracking velocimetry technique. The investigated quantum flow occurs in a square channel of 25 mm sides and 100 mm length, appreciably wider than those employed in previous related experiments. Flow velocities up to 10 mm/s are obtained, corresponding to temperatures between about 1.3 K and 2.1 K, and applied heat fluxes between ca. 50 W/m{sup 2} and 500 W/m{sup 2}. The character of the obtained particle trajectories changes significantly as the imposed mean flow velocity increases. At thermal counterflow velocities lower than approximately 1 mm/s, the particle tracks appear straighter than at larger velocities. On the basis of the current understanding of the underlying physics, it is argued that the outcome is most likely due to the transition to the turbulent state of the investigated flow as, for narrower channels, this transition was reported to occur at larger velocities. The present results confirm that, at least in the parameter ranges investigated to date, the transition to turbulence in thermal counterflow depends on the geometry of the channel where this quantum flow develops.

  17. Liquid helium in disorder and boson localization

    NASA Astrophysics Data System (ADS)

    Albergamo, Francesco; Pearce, Jonathan; Glyde, Henry; Daughton, David; Mulders, Norbert; Bossy, Jacques; Schober, Helmut

    2005-03-01

    Neutron scattering measurements of the excitations of liquid ^4He confined in three porous media focusing on temperatures around the superfluid-normal fluid critical temperature Tc are presented and discussed. The three porous media are Vycor (Tc= 2.05 K at SVP), 44 å pore diameter gelsil (Tc= 1.92 K at SVP) and 25 å pore diameter gelsil (Tc 1.0 K at SVP) ^[1,2]. In all these media, liquid ^4He supports well-defined phonon-roton excitations above Tc, in the "normal" phase (up Tλ= 2.17 K at SVP). Since well-defined excitations are associated with Bose-Einstein condensation (BEC), this suggests that there is BEC in the "normal" phase. Also, since there is no superflow, this BEC is apparently localized in the media separated by regions of normal fluid. In this picture, the superfluid-normal transition in disorder is associated with an extended-localized BEC crossover with localized BEC remaining above Tc ^[3]. ^[1]F. Albergamo et al., Phys. Rev. B 69, 014514 (2004) ^[2]J. V. Pearce et al., Phys. Rev. Lett. 93, 145303 (2004)) ^[3]H. R. Glyde et al., Phys. Rev. Lett. 84, 2646 (2000)

  18. Experiments with single electrons in liquid helium

    SciTech Connect

    Guo, W.; Jin, D.; Seidel, G. M.; Maris, H. J.

    2009-02-01

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

  19. Measurements of the Complex Permittivity of Liquid Helium-4 in the Millimeter Wave Range by a Whispering Gallery Mode Resonator

    NASA Astrophysics Data System (ADS)

    Smorodin, A. V.; Rybalko, A. S.; Konstantinov, D.

    2017-02-01

    We report an experimental study of the electrical properties of liquid helium-4 in the temperature range 1.2-3 K. The experiment is carried out in the millimeter wave range using a whispering gallery mode dielectric resonator, and the complex permittivity of liquid helium is extracted from the data using the resonant perturbation method. The results for the temperature dependence of the dielectric constant are consistent with the previous studies. In addition, we find strong enhancement of the loss tangent around the superfluid transition temperature.

  20. Measurements of the Complex Permittivity of Liquid Helium-4 in the Millimeter Wave Range by a Whispering Gallery Mode Resonator

    NASA Astrophysics Data System (ADS)

    Smorodin, A. V.; Rybalko, A. S.; Konstantinov, D.

    2017-06-01

    We report an experimental study of the electrical properties of liquid helium-4 in the temperature range 1.2-3 K. The experiment is carried out in the millimeter wave range using a whispering gallery mode dielectric resonator, and the complex permittivity of liquid helium is extracted from the data using the resonant perturbation method. The results for the temperature dependence of the dielectric constant are consistent with the previous studies. In addition, we find strong enhancement of the loss tangent around the superfluid transition temperature.

  1. Neutron-scattering investigation of the excitation spectrum of liquid helium

    SciTech Connect

    Kalinin, I. V. Lauter, H.; Puchkov, A. V.

    2007-07-15

    The results of the investigation of the temperature evolution of the scattering law S(Q, {omega}) of superfluid helium measured in the wave-vector range 0.3 < Q < 0.8 A{sup -1} and helium temperatures from 1.0 to 2.2 K are reported. The investigations have been performed on the high-flux reactor at the Institut Laue-Langevin (France) with the IN6 neutron inelastic-scattering spectrometer. The deviation of the experimental scattering law of liquid helium from the damping harmonic oscillator model, which was previously observed independently in the experiments with the IN6 spectrometer and with the DIN-2PI spectrometer (at the IBR-2 reactor, Dubna, Russia) and were more recently called extrapeak, has been corroborated. The temperature dependence of the extrapeak parameters has been determined. This dependence makes it possible to propose hypotheses on the nature of the extrapeak.

  2. Quantum vortices and thermally induced luminescence of nitrogen nanoclusters immersed in liquid helium

    NASA Astrophysics Data System (ADS)

    Meraki, A.; McColgan, P. T.; Rentzepis, P. M.; Li, R. Z.; Lee, D. M.; Khmelenko, V. V.

    2017-03-01

    We performed investigations of ensembles of molecular nitrogen nanoclusters, containing stabilized nitrogen atoms, immersed in liquid helium by electron spin resonance and optical spectroscopy. We observed thermoluminescence of nitrogen atoms and molecules via increasing temperature from 1.25 to 4.4 K. Two thermoluminescence maxima were observed, one in superfluid helium (HeII) at T ˜1.9 K and another in normal helium (HeI) at T ˜3.2 K . We explain appearance of luminescence in HeII by chemical reactions of nitrogen atoms on surfaces of nanoclusters which might be initiated by quantum vortices. Thermoluminescence in HeI occurs due to the process of nanocluster association resulting in thermal explosions of a small fraction of nanoclusters. This research might open new possibilities for studying a broad range of chemical reactions initiated by quantum vortices in HeII.

  3. New light on the intriguing history of superfluidity in liquid (4)He.

    PubMed

    Griffin, Allan

    2009-04-22

    Surprisingly, it was 30 years after the first liquefaction of (4)He in 1908 that the discovery that liquid (4)He is not just a 'cold' liquid was made. Below T = 2.18 K, it is a 'quantum' liquid which exhibits spectacular macroscopic quantum behaviour that can be seen with the naked eye. Since the observation of superfluidity in liquid (4)He is one of the greatest discoveries in modern physics, we present a day-to-day chronology of the tangled events which preceded the seminal discovery of zero viscosity in 1938 by Kapitza in Moscow and by Allen and Misener in Cambridge. On the theory side, London argued in 1938 that the microscopic basis for this new superfluid phase was the forgotten phenomenon of Bose-Einstein condensation (BEC) first suggested by Einstein in 1925. In 1941, Landau developed a very successful theory of superfluid (4)He, but it was not anchored in a microscopic theory of interacting atoms. It took another 20 years for theorists to unify the two seemingly different theories of Landau and London. Experiments on trapped superfluid atomic gases since 1995 have shone new light on superfluid (4)He. In the mid-1930s, London had emphasized that superconductivity in metals and superfluidity in liquid (4)He were similar. Experiments on trapped two-component Fermi gases in the last five years have shown that a Bose condensate is indeed the basis of both of these superfluid phases. This confirms the now famous Bardeen-Cooper-Schrieffer-BEC crossover scenario developed for superfluidity by Leggett and Nozières in the early 1980s but largely ignored until a few years ago. The study of superfluid (4)He will increasingly overlap with strongly interacting dilute quantum gases, perhaps opening up a new era of research on this most amazing liquid.

  4. Measurement of the charge transfer efficiency of electrons clocked on superfluid helium

    SciTech Connect

    Sabouret, G.; Lyon, S.A.

    2006-06-19

    Electrons floating on the surface of liquid helium are possible qubits for quantum information processing. Varying electric potentials do not modify spin states, which allows their transport on helium using a charge-coupled device (CCD)-like array of underlying gates. This scheme depends on an efficient intergate electron transfer and on the absence of electron traps. We will present a measurement of the charge transfer efficiency (CTE) of electrons clocked back and forth above a short CCD-like structure. The CTE obtained at low clocking frequencies is 0.999 with an electron density of about 4 electrons/{mu}m{sup 2}. We find no evidence for deep electron trapping.

  5. Top-off procedure for space-bound superfluid helium cryostats

    NASA Technical Reports Server (NTRS)

    Petrac, D.

    1982-01-01

    Tests have been carried out on the transfer of pressurized liquid helium, slightly above the lambda temperature, in order to determine the optimum transfer parameters for a ground-based top-off just prior to launch. It is shown that the maximum mass fill of a spaceborne cryostat can be accomplished with the low-pressure top-off after initial fill with normal helium. The realistic maximum fill at temperatures below the lambda temperature can be expected to be at least 90 percent, which results in about 40 to 50 percent more mass at launch than without the top-off. In each case, specific ground support equipment is required to satisfy the individual cryostat requirements and extreme care is necessary during the transfer procedure.

  6. Microsolvation in superfluid helium droplets studied by the electronic spectra of six porphyrin derivatives and one chlorine compound.

    PubMed

    Riechers, R; Pentlehner, D; Slenczka, A

    2013-06-28

    After almost two decades of high resolution molecular spectroscopy in superfluid helium droplets, the understanding of microsolvation is still the subject of intense experimental and theoretical research. According to the published spectroscopic work including microwave, infrared, and electronic spectroscopy, the latter appears to be particularly promising to study microsolvation because of the appearance of pure molecular transitions and spectrally separated phonon wings. Instead of studying the very details of the influence of the helium environment for one particular dopant molecule as previously done for phthalocyanine, the present study compares electronic spectra of a series of non-polar porphyrin derivatives when doped into helium droplets consisting of 10(4)-10(5) helium atoms. Thereby, we focus on the helium-induced fine structure, as revealed most clearly at the corresponding electronic origin. The interpretation and the assignment of particular features obtained in the fluorescence excitation spectra are based on additional investigations of dispersed emission spectra and of the saturation behavior. Besides many dopant-specific results, the experimental study provides strong evidence for a particular triple peak feature representing the characteristic signature of helium solvation for all seven related dopant species.

  7. Measurements of Thermal Conductivity of Superfluid Helium Near its Transition Temperature T(sub lambda) in a 2D Confinement

    NASA Technical Reports Server (NTRS)

    Jerebets, Sergei

    2004-01-01

    We report our recent experiments on thermal conductivity measurements of superfluid He-4 near its phase transition in a two-dimensional (2D) confinement under saturated vapor pressure. A 2D confinement is created by 2-mm- and 1-mm-thick glass capillary plates, consisting of densely populated parallel microchannels with cross-sections of 5 x 50 and 1 x 10 microns, correspondingly. A heat current (2 < Q < 400 nW/sq cm) was applied along the channels long direction. High-resolution measurements were provided by DC SQUID-based high-resolution paramagnetic salt thermometers (HRTs) with a nanokelvin resolution. We might find that thermal conductivity of confined helium is finite at the bulk superfluid transition temperature. Our 2D results will be compared with those in a bulk and 1D confinement.

  8. Laser-Induced Breakdown in Liquid Helium

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  9. Correlation of Helium Solubility in Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.; Zimmerli, Gregory A.

    2012-01-01

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

  10. Linear dichroism spectroscopy of gas phase biological molecules embedded in superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Kong, Wei; Pei, Linsen; Zhang, Jie

    This article presents the current status of gas phase linear dichroism (LD) spectroscopy, including the theoretical background, the experimental technique, and a few examples in the UV/VIS and IR. Orientation and alignment of gas phase samples are achieved using a DC electric field. To reach the necessary degree of alignment, biological molecules vaporized from a heated oven need to be embedded in superfluid helium droplets. Excitation under different polarization directions of the light source relative to the alignment field can then be used to derive the direction of the transition dipole, or the size of the permanent dipole, or both. For biological molecules that have no resonance lines or too many resonance lines, LD offers an additional parameter for spectroscopic assignment and tautomeric and conformational identification. The direction of the vibrational transition dipole is proven more reliable for vibrational and tautomeric assignment than the energy or frequency information, which is often problematic because of its sensitivity to basis sets and calculation methods. Several examples of vibrational LD of nucleic acid bases will be discussed. On the other hand, if a chromophore with a known electronic transition dipole is attached to a biological molecule, as demonstrated in the case of tryptamine, the permanent dipole determined from LD is then representative of the molecular conformation. This method of conformational determination does not rely on detailed spectroscopic assignment, thus it is applicable to molecules that do not have resolvable vibronic bands. However, its application is currently limited to the availability of an effective chromophore, and the search for such a chromophore is an on-going effort.

  11. Subharmonic phonon-ripplon coupling in the 2D Wigner solid on superfluid helium

    NASA Astrophysics Data System (ADS)

    Monarkha, Yuriy

    2017-06-01

    The nonlinear response of the liquid-helium surface to the oscillating motion of a two-dimensional electron solid is analyzed. In the nonlinear regime, we found that the effective mass of surface dimples formed under electrons behaves as a singular odd function near subharmonics of the frequency of a ripplon whose wave vector coincides with a reciprocal-lattice vector. This unexpected behavior of the dimple mass is shown to lead to the appearance of new longitudinal phonon-ripplon coupled modes. It also affects in a nontrivial way positions of conventional phonon-ripplon coupled modes. Both these theoretical results explain experimental observations reported previously.

  12. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, Vladimir

    1986-01-01

    This invention teaches a nuclear fission reactor having a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200.degree.-1800.degree. C. range, and even higher to 2500.degree. C., limited only by the thermal effectiveness of the structural materials, increasing the efficiency of power generation from the normal 30-35% with 300.degree.-500.degree. C. upper limit temperature to 50-65%. Irradiation of the circulating liquid fuel, as contrasted to only localized irradiation of a solid fuel, provides improved fuel utilization.

  13. The superfluid helium flow in the channel with porous insert at the presence of longitudinal heat flux

    NASA Astrophysics Data System (ADS)

    Korolyov, P. V.; Kryukov, A. P.; Puzina, Yu Yu

    2016-10-01

    The processes of heat and mass transfer during the flow of helium-II (He-II) in a channel with porous backfilling placed in a particular section of its length are studied. Heat flux is directed along the axis of the channel in such a way that on one side of the backfilling vapor plug is formed. Calculation of steady-state transport processes at vapor-He-II interfaces is carried out using methods of molecular-kinetic theory. The normal fluid flow in the pores in laminar and turbulent regimes is described by equations taking into account features of heat and mass transfer in superfluid helium. The relationships between the length of the porous insert and the velocities of fluids for different flow regimes are formulated. The results of the calculations are analyzed by comparison with previous data for the flow of He-II in the individual capillary.

  14. Quartz Tuning Fork Pressure Gauge for High-Pressure Liquid Helium

    NASA Astrophysics Data System (ADS)

    Botimer, J.; Velasco, A.; Taborek, P.

    2017-01-01

    We have measured the quality factor Q and the frequency f of a 32-kHz quartz tuning fork immersed in liquid ^4He between 0.9 and 3.0 K, over pressures ranging from the saturated vapor pressure to ≈ 25 atm. At constant pressure, as a function of temperature, the quality factor and frequency have strong features related to the temperature dependence of the superfluid fraction. At constant temperature, Q depends on the superfluid fraction, while the frequency is a smooth function of pressure. The behavior is explained using a simple hydrodynamic model. The liquid helium viscosity is obtained from measured values of Q, and together with tabulated values of the helium density as a function of pressure and temperature, the frequency shift can be parameterized as a function of temperature and pressure. The observed sensitivity is ≈ 7.8 Hz/atm. The quartz tuning fork provides a compact low power method of measuring the pressure in the bulk liquid.

  15. Working model of the London moment readout system. [the study of super fluid plug operation using liquid helium

    NASA Technical Reports Server (NTRS)

    Hendricks, J. B.; Karr, G. R.

    1975-01-01

    The operating characteristics of a porous plug which has liquid helium on one side and which is pumped on under vacuum on the other side are discussed. The system investigated consists of a container of liquid helium which is well isolated, and the only means for mass flow out of the container is through a plug mode of porous material. The plug was assumed to have liquid helium on the container side while the other side of the plug is evacuated. Three cases were considered: (1) perfect evacuation with zero pressure, (2) evacuation through a chocked orifice, and (3) evacuation through a long, small diameter pipe with heating. Mass flow rates were determined along with mass flow at temperature above the lambda point temperature. Solutions were obtained for normal and superfluid velocity.

  16. Liquid uranium alloy-helium fission reactor

    DOEpatents

    Minkov, V.

    1984-06-13

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

  17. Cryogenic helium 2 systems for space applications

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  18. Cryogenic helium 2 systems for space applications

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

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

    SciTech Connect

    WANG,L.; JIA,L.

    2002-07-22

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

  20. From Liquid Helium to Granular Materials

    NASA Astrophysics Data System (ADS)

    Behringer, Robert P.

    2016-11-01

    This article provides a brief history of work that I have either carried out with Horst Meyer, or that was connected in some way with experiences reaching back to the laboratory known as LTM for low temperature [physics] Meyer, at Duke University. It is not intended as a complete review of all relevant work, but rather to hit highlights. My work with Horst started with studies of critical phenomena in liquid helium. This system provided an extremely rich and diverse testing ground for then newly emerging theories of static and dynamic critical phenomena. A key aspect of the experimental work with Horst was high-precision measurements of temperature and pressure. The ability to measure thermal properties with exceptional precision was at the core of this work. It also provided a natural springboard for entirely different investigations of Rayleigh-Bénard convection, which had just been initiated by Guenter Ahlers. My postdoc with Guenter provided a whole new set of experiences involving convection, dynamical instabilities, and chaos, where again the special properties, measurement techniques, and creative approaches to research associated with liquid helium were critical. In fact, later, knowledge of these techniques allowed me to start a whole new research direction in granular materials, which is a primary focus of my current research.

  1. Neutrons on a surface of liquid helium

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  2. Second virial coefficient of helium adsorbed on liquid hydrogen

    SciTech Connect

    Paine, C.G.; Seidel, G.M. )

    1994-08-01

    The nonlinear dependence of the surface energy of liquid hydrogen as a function of the density of helium gas in equilibrium with the liquid surface has been used to determine the second virial coefficient of the two-dimensional gas of helium atoms adsorbed on the surface. The surface energy of both liquid hydrogen and liquid deuterium has been measured in the presence of [sup 4]He and [sup 3]He. The experimental results are in rough agreement with theoretical prediction.

  3. Neutron studies of liquid and solid helium

    SciTech Connect

    Glyde, H.R.

    1987-04-01

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

  4. Superfluidity of Bose—Einstein condensates in ultracold atomic gases

    NASA Astrophysics Data System (ADS)

    Zhu, Qi-Zhong; Wu, Biao

    2015-05-01

    Liquid helium 4 had been the only bosonic superfluid available in experiments for a long time. This situation was changed in 1995, when a new superfluid was born with the realization of the Bose-Einstein condensation in ultracold atomic gases. The liquid helium 4 is strongly interacting and has no spin; there is almost no way to change its parameters, such as interaction strength and density. The new superfluid, Bose-Einstein condensate (BEC), offers various advantages over liquid helium. On the one hand, BEC is weakly interacting and has spin degrees of freedom. On the other hand, it is convenient to tune almost all the parameters of a BEC, for example, the kinetic energy by spin-orbit coupling, the density by the external potential, and the interaction by Feshbach resonance. Great efforts have been devoted to studying these new aspects, and the results have greatly enriched our understanding of superfluidity. Here we review these developments by focusing on the stability and critical velocity of various superfluids. The BEC systems considered include a uniform superfluid in free space, a superfluid with its density periodically modulated, a superfluid with artificially engineered spin-orbit coupling, and a superfluid of pure spin current. Due to the weak interaction, these BEC systems can be well described by the mean-field Gross-Pitaevskii theory and their superfluidity, in particular critical velocities, can be examined with the aid of Bogoliubov excitations. Experimental proposals to observe these new aspects of superfluidity are discussed. Project supported by the National Basic Research Program of China (Grant Nos. 2013CB921903 and 2012CB921300) and the National Natural Science Foundation of China (Grant Nos. 11274024, 11334001, and 11429402).

  5. Investigating Electrical Breakdown in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Bouman, Nathaniel; SNS nEDM Collaboration

    2016-09-01

    The SNS nEDM experiment at Oak Ridge National Laboratory aims to search for the electric dipole moment of the neutron (nEDM) at the 3x10-28 level. The experiment is currently in the critical component demonstration phase. The design of the experiment calls for an electric field of 75 kV/cm across the experimental cells between electrodes within a bath of liquid helium (LHe). However, the electric breakdown phenomenon in LHe is poorly understood. Experiments investigating the breakdown of LHe were carried out at Los Alamos National Laboratory using a small-scale high voltage (SSHV) test apparatus at temperatures from 1.7K to 4K. Effects of varying temperature, pressure, and electrode surface conditions on LHe breakdown were investigated. Results and their implications to the SNS nEDM experiment will be presented.

  6. Carbon Nanotubes Immersed in Superfluid Helium: The Impact of Quantum Confinement on Wetting and Capillary Action.

    PubMed

    Hauser, Andreas W; de Lara-Castells, María Pilar

    2016-12-01

    A recent experimental study [ Ohba, Sci. Rep. 2016, 6, 28992 ] of gas adsorption on single-walled carbon nanotubes at temperatures between 2 and 5 K reported a quenched propagation of helium through carbon nanotubes with diameters below 7 Å despite the small kinetic diameter of helium atoms. After assessing the performance of a potential model for the He-nanotube interaction via ab initio calculations with density functional theory-based symmetry adapted perturbation theory, we apply orbital-free helium density functional theory to show that the counterintuitive experimental result is a consequence of the exceptionally high zero-point energy of helium and its tendency to form spatially separated layers of helium upon adsorption at the lowest temperatures. Helium filling factors are derived for a series of carbon nanotubes and compared to the available experimental data.

  7. A titanium transition-edge sensor for the in-situ detection of individual He2 excimers in superfluid helium

    NASA Astrophysics Data System (ADS)

    Carter, Faustin; Hertel, Scott; Matulis, Catherine; Rooks, Michael; McKinsey, Daniel; Prober, Daniel

    2015-03-01

    Incident radiation can excite superfluid helium into a diatomic He2* excimer, which decays through the emission of a 15 eV photon. Such excimers have been used as tracers to measure the superfluid's quantum turbulence, thanks in part to the long half-life of the He2* triplet state (~ 13 seconds). However, the efficient detection of single or a few excimers remains a challenge. We present a detector capable of in-situ detection of the He2* excimers either directly (the excimer collides with the detector), or by collecting the 15 eV photon emission upon decay. This detector is based on a titanium superconducting transition-edge sensor (TES), with an energy resolution of 1.5 eV fwhm, coupled to an aluminum absorber. The TES is designed to operate from 20-300 mK in a dilution refrigerator. We will discuss operating characteristics of the detector and present preliminary data for detection of individual excimers. We acknowledge support from YINQE, NSF MRSEC DMR-1119826, and NSF DMR-1007974.

  8. Design, Project Execution, and Commissioning of the 1.8 K Superfluid Helium Refrigeration System for SRF Cryomodule Testing

    DOE PAGES

    Treite, P.; Nuesslein, U.; Jia, Yi; ...

    2015-07-15

    The Fermilab Cryomodule Test Facility (CMTF) provides a test bed to measure the performance of superconducting radiofrequency (SRF) cryomodules (CM). These SRF components form the basic building blocks of future high intensity accelerators such as the International Linear Collider (ILC) and a Muon Collider. Linde Kryotechnik AG and Linde Cryogenics have designed, constructed and commissioned the superfluid helium refrigerator needed to support SRF component testing at the CMTF Facility. The hybrid refrigerator is designed to operate in a variety of modes and under a wide range of boundary conditions down to 1.8 Kelvin set by CM design. Special features ofmore » the refrigerator include the use of warm and cold compression and high efficiency turbo expanders.This paper gives an overview on the wide range of the challenging cooling requirements, the design, fabrication and the commissioning of the installed cryogenic system.« less

  9. Design, Project Execution, and Commissioning of the 1.8 K Superfluid Helium Refrigeration System for SRF Cryomodule Testing

    SciTech Connect

    Treite, P.; Nuesslein, U.; Jia, Yi; Klebaner, A.; Theilacker, J.

    2015-07-15

    The Fermilab Cryomodule Test Facility (CMTF) provides a test bed to measure the performance of superconducting radiofrequency (SRF) cryomodules (CM). These SRF components form the basic building blocks of future high intensity accelerators such as the International Linear Collider (ILC) and a Muon Collider. Linde Kryotechnik AG and Linde Cryogenics have designed, constructed and commissioned the superfluid helium refrigerator needed to support SRF component testing at the CMTF Facility. The hybrid refrigerator is designed to operate in a variety of modes and under a wide range of boundary conditions down to 1.8 Kelvin set by CM design. Special features of the refrigerator include the use of warm and cold compression and high efficiency turbo expanders.This paper gives an overview on the wide range of the challenging cooling requirements, the design, fabrication and the commissioning of the installed cryogenic system.

  10. Superfluid helium sloshing dynamics induced oscillations and fluctuations of angular momentum, force and moment actuated on spacecraft driven by gravity gradient or jitter acceleration associated with slew motion

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1994-01-01

    The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by the gravity gradient and jitter accelerations associated with slew motion for the purpose to perform scientific observation during the normal spacecraft operation are investigated. An example is given with the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) for slew motion which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid-vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers have also been derived. Examples are also given for cases applicable to the AXAF-S spacecraft sloshing dynamics associated with slew motion.

  11. Development of a transferline connecting a helium liquefier coldbox and a liquid helium Dewar

    NASA Astrophysics Data System (ADS)

    Menon, Rajendran S.; Rane, Tejas; Chakravarty, Anindya; Joemon, V.

    2017-02-01

    A helium liquefier with demonstrated capacity of 32 1/hr has been developed by BARC. Mumbai. A transferline for two way flow of helium between the helium liquefier coldbox and receiver Dewar has been developed in-house at BARC. Further, a functionally similar, but structurally improved transferline has been developed through a local fabricator. This paper describes and discusses issues related to the development of these cryogenic transferlines. The developed transferlines have been tested with a flow of liquid nitrogen and successfully utilised later in the helium liquefier plant.

  12. A 3-D model of superfluid helium suitable for numerical analysis

    SciTech Connect

    Darve, C.; Patankar, N.A.; Van Sciver, S.W.; /Natl. High Mag. Field Lab.

    2008-01-01

    The two-fluid description is a very successful phenomenological representation of the properties of Helium II. A 3-D model suitable for numerical analysis based on the Landau-Khalatnikov description of Helium II is proposed. In this paper we introduce a system of partial differential equations that is both complete and consistent as well as practical, to be used for a 3-D solution of the flow of Helium II. The development of a 3-D numerical model for Helium II is motivated by the need to validate experimental results obtained by observing the normal component velocity distribution in a Helium II thermal counter-flow using the Particle Image Velocimetry (PIV) technique.

  13. Creation evidence of the second non-dispersive Zakharenko wave by helium atomic beams in superfluid helium-II at low temperatures

    NASA Astrophysics Data System (ADS)

    Zakharenko, A. A.

    2007-10-01

    In this work, the experimental results of the creation of the second non-dispersive Zakharenko wave (C_{ph}=C_{g} ≠ 0) in the negative roton branch (the so-called second sound) of the bulk elementary excitations (BEEs) energy spectra are introduced. Several BEE signals detected by a bolometer situated in the isotopically pure liquid helium-II at low temperatures ˜100 mK are shown, which give evidence of negative roton creation in the liquid by helium atomic beams striking the liquid surface. The negative roton signals were clearly distinguished by the following ways: the negative roton signal created by helium atomic beams appeared earlier than the positive roton signal created by the beams, and presence of both positive and negative roton signals together. It is natural that the negative roton creation by the beams requires the ^{4}He-atom energies ˜12 K, while the positive roton creation by the atomic beams requires energies ˜35 K. Therefore, successive increase in the heater power resulting in an increase in the ^{4}He-atom energies gives solid evidence that the negative rotons are first created in the liquid by the helium atomic beams.

  14. Quantum interferences in the photodissociation of Cl2(B) in superfluid helium nanodroplets ((4)He)N.

    PubMed

    Vilà, Arnau; González, Miguel; Mayol, Ricardo

    2015-12-28

    Quantum interferences are probably one of the most fascinating phenomena in chemical physics and, particularly, in reaction dynamics, where they are often very elusive from an experimental perspective. Here, we have theoretically investigated, using a hybrid method recently proposed by us, the dynamics of the formation of confinement quantum interferences in the photodissociation of a Cl2 molecule (B ← X electronic excitation) embedded in a superfluid helium nanodroplet of different sizes (50-500 (4)He atoms), which is to the best of our knowledge the first time that this type of interference is described in reaction dynamics. Thus, we have widely extended a recent contribution of our group, where interferences were not the main target, identifying the way they are formed and lead to the production of strongly oscillating velocity distributions in the Cl dissociating atoms, and also paying attention to the energy transfer processes involved. This probably corresponds to a rather general behavior in the photodissociation of molecules in helium nanodroplets. We hope that the present study will encourage the experimentalists to investigate this captivating phenomenon, although the technical difficulties involved are very high.

  15. Design of a Superconducting Magnetic Suspension System for a Liquid Helium Flow Experiment

    NASA Technical Reports Server (NTRS)

    Smith, Michael R.; Eyssa, Yehia M.; VanSciver, Steven W.

    1996-01-01

    We discuss a preliminary design for a superconducting magnetic suspension system for measurement of drag on rotationally symmetric bodies in liquid helium. Superconducting materials are a natural choice for liquid helium studies, since temperatures are well below most critical temperatures, so that the resulting heat load is negligible. Also, due to its diamagnetic properties, a superconducting model (for example made or coated with Nb) is inherently stable against disturbances. Issues which we consider include model placement during initial cool-down, maintaining placement during anticipated drag and lift forces, and force measurement. This later can be achieved by a passive technique, where the body is allowed to deflect under the influence of drag from its neutral position. The resulting shift in flux is detected via a superconducting pickup coil. The pickup coil may be connected either to a SQUID, or a secondary loop wound around a Hall probe. Both options are discussed. The objective of this work is to gain a better understanding of the nature of turbulent fields in normal and superfluid helium for potential application to problems in classical high Reynolds number turbulence.

  16. Liquid Oxygen Thermodynamic Vent System Testing with Helium Pressurization

    NASA Technical Reports Server (NTRS)

    VanDresar, Neil T.

    2014-01-01

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

  17. The effect of confinement on liquid helium near the lambda line

    SciTech Connect

    Larson, M.E.

    1993-12-31

    This thesis is the compilation of several projects relevant to the behavior of confined liquid helium near the {lambda}-line. The first project described is the development of two new high resolution thermometers optimized for specific heat studies of helium confined in pores. One of the thermometers is a superconductive transition thermometer (STT). The STT has a temperature resolution of about 5nK. The other high resolution thermometer described is a magnetic susceptibility thermometer. This thermometer measures the magnetization of copper ammonium bromide (CAB) using a SQUID magnetometer. The CAB thermometer has an observed sensitivity of about 20nK. Suggestions for improvements in both thermometers are made. Simulation work on the temperature profile of a thermal conductivity cell near T{lambda} is described. The simulations are compared with the experimental results, and a careful study of the stability of the numerics is described. The study of helium confined into pores and films is described next. Both previous theoretical and experimental work on finite size effects in liquid helium are described. The geometry provided by glass capillary arrays is analyzed to determine what would be observed when the specific heat of helium confined to the arrays is measured. Finally, I describe my measurements of the isobaric thermal expansion coefficient {beta}{sub P} of 4He confined in an aerogel for several isobars along the {lambda}-line. {beta}{sub P} is an asymptotically linear function of C{sub P} near the superfluid transition temperature {Tc}. Therefore, fits to power laws in t {triple_bond} T/{Tc} - 1 give the specific heat exponents {alpha} and {alpha}{prime} and amplitude ratio A{prime}/A. Such fits gave different exponents {alpha} {approx} -0.6 and {alpha}{prime} {approx} -1.0 above and below {Tc}.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  20. Renormalization-group study of superfluidity and phase separation of helium mixtures immersed in a nonrandom aerogel

    SciTech Connect

    Lopatnikova, A.; Berker, A.N.

    1997-02-01

    Superfluidity and phase separation in {sup 3}He-{sup 4}He mixtures immersed in a jungle-gym (nonrandom) aerogel are studied by renormalization-group theory. Phase diagrams are calculated for a variety of aerogel concentrations. Superfluidity at very low {sup 4}He concentrations and a depressed tricritical temperature are found at the onset of superfluidity. A superfluid-superfluid phase separation, terminating at an isolated critical point, is found entirely within the superfluid phase. These phenomena and trends with respect to aerogel concentration are explained by the connectivity and tenuousness of a jungle-gym aerogel. {copyright} {ital 1997} {ital The American Physical Society}

  1. Renormalization-group study of superfluidity and phase separation of helium mixtures immersed in a nonrandom aerogel

    NASA Astrophysics Data System (ADS)

    Lopatnikova, Anna; Nihat Berker, A.

    1997-02-01

    Superfluidity and phase separation in 3-4He mixtures immersed in a jungle-gym (nonrandom) aerogel are studied by renormalization-group theory. Phase diagrams are calculated for a variety of aerogel concentrations. Superfluidity at very low 4He concentrations and a depressed tricritical temperature are found at the onset of superfluidity. A superfluid-superfluid phase separation, terminating at an isolated critical point, is found entirely within the superfluid phase. These phenomena and trends with respect to aerogel concentration are explained by the connectivity and tenuousness of a jungle-gym aerogel.

  2. Renormalization-Group Theory Study of Superfluidity and Phase Separation of Helium Mixtures Immersed in Jungle-Gym Aerogel

    NASA Astrophysics Data System (ADS)

    Lopatnikova, Anna; Berker, A. Nihat

    1997-03-01

    Superfluidity and phase separation in ^3He-^4He mixtures immersed in jungle-gym (non-random) aerogel are studied by renormalization-group theory.(Phys. Rev. B, in press (1996)) Phase diagrams are calculated for a variety of aerogel concentrations. Superfluidity at very low ^4He concentrations and a depressed tricritical temperature are found at the onset of superfluidity. A superfluid-superfluid phase separation, terminating at an isolated critical point, is found entirely within the superfluid phase. These phenomena, and trends with respect to aerogel concentration, are explained by the connectivity and tenuousness of jungle-gym aerogel.

  3. Surface Region of Superfluid Helium as an Inhomogeneous Bose-Condensed Gas

    NASA Astrophysics Data System (ADS)

    Griffin, A.; Stringari, S.

    1996-01-01

    We present arguments that the low density surface region of self-bounded superfluid 4He systems is an inhomogeneous dilute Bose gas, with almost all of the atoms occupying the same single-particle state at T = 0. Numerical evidence for this complete Bose-Einstein condensation was first given by the many-body variational calculations of 4He droplets by Lewart, Pandharipande, and Pieper in 1988 [Phys. Rev. B 37, 4950 (1988)]. We show that the low density surface region can be treated rigorously using a generalized Gross-Pitaevskii equation for the Bose order parameter.

  4. Path integral Monte Carlo simulation of global and local superfluidity in liquid 4He reservoirs separated by nanoscale apertures

    NASA Astrophysics Data System (ADS)

    Volkoff, Tyler; Kwon, Yongkyung; Whaley, K. Birgitta

    2016-10-01

    We present a path integral Monte Carlo study of the global superfluid fraction and local superfluid density in cylindrically symmetric reservoirs of liquid 4He separated by nanoaperture arrays. The superfluid response to both translations along the axis of symmetry (longitudinal response) and rotations about the cylinder axis (transverse response) are computed, together with radial and axial density distributions that reveal the microscopic inhomogeneity arising from the combined effects of the confining external potential and the 4He-4He interatomic potentials. We make a microscopic determination of the length scale of decay of superfluidity at the radial boundaries of the system by analyzing the local superfluid density distribution to extract a displacement length that quantifies the superfluid mass displacement away from the boundary. We find that the longitudinal superfluid response is reduced in reservoirs separated by a septum containing sufficiently small apertures compared to a cylinder with no intervening aperture array, for all temperatures below Tλ. For a single aperture in the septum, a significant drop in the longitudinal superfluid response is seen when the aperture diameter is made smaller than twice the empirical temperature-dependent 4He healing length, consistent with the formation of a weak link between the reservoirs. Increasing the diameter of a single aperture or the number of apertures in the array results in an increase of the superfluid density toward the expected bulk value.

  5. Using second-sound shock waves to probe the intrinsic critical velocity of liquid helium II

    NASA Technical Reports Server (NTRS)

    Turner, T. N.

    1983-01-01

    A critical velocity truly intrinsic to liquid helium II is experimentally sought in the bulk fluid far from the apparatus walls. Termed the 'fundamental critical velocity,' it necessarily is caused by mutual interactions which operate between the two fluid components and which are activated at large relative velocities. It is argued that flow induced by second-sound shock waves provides the ideal means by which to activate and isolate the fundamental critical velocity from other extraneous fluid-wall interactions. Experimentally it is found that large-amplitude second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically manifested as a limit to the maximum attainable shock strength. This breakdown is shown to be caused by a fundamental critical velocity. Secondary effects include boiling for ambient pressures near the saturated vapor pressure or the formation of helium I boundary layers at higher ambient pressures. When compared to the intrinsic critical velocity discovered in highly restricted geometries, the shock-induced critical velocity displays a similar temperature dependence and is the same order of magnitude.

  6. Using second-sound shock waves to probe the intrinsic critical velocity of liquid helium II

    NASA Technical Reports Server (NTRS)

    Turner, T. N.

    1983-01-01

    A critical velocity truly intrinsic to liquid helium II is experimentally sought in the bulk fluid far from the apparatus walls. Termed the 'fundamental critical velocity,' it necessarily is caused by mutual interactions which operate between the two fluid components and which are activated at large relative velocities. It is argued that flow induced by second-sound shock waves provides the ideal means by which to activate and isolate the fundamental critical velocity from other extraneous fluid-wall interactions. Experimentally it is found that large-amplitude second-sound shock waves initiate a breakdown in the superfluidity of helium II, which is dramatically manifested as a limit to the maximum attainable shock strength. This breakdown is shown to be caused by a fundamental critical velocity. Secondary effects include boiling for ambient pressures near the saturated vapor pressure or the formation of helium I boundary layers at higher ambient pressures. When compared to the intrinsic critical velocity discovered in highly restricted geometries, the shock-induced critical velocity displays a similar temperature dependence and is the same order of magnitude.

  7. Quantum turbulence—from superfluid helium to atomic Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Tsubota, Makoto

    2009-04-01

    This paper reviews recent developments in the physics of quantum turbulence (QT). QT was discovered in superfluid 4He in the 1950s, while the research has taken a new direction since the middle of the 1990s. QT is comprised of quantized vortices that are definite topological defects and expected to give a prototype of turbulence much simpler than usual classical turbulence. We give a general introduction and brief review of classical turbulence followed by a description of the dynamics of quantized vortices. After mentioning the modern research trends in QT, we discuss the energy spectra, the energy cascade and the possible dissipation mechanism of QT at very low temperatures. The last part is devoted to QT in atomic Bose-Einstein condensates.

  8. A helium-3 refrigerator employing capillary confinement of liquid cryogen

    NASA Technical Reports Server (NTRS)

    Ennis, D. J.; Kittel, P.; Brooks, W.; Miller, A.; Spivak, A. L.

    1983-01-01

    A condensation refrigerator suitable for operation in a zero gravity space environment was constructed. The condensed liquid refrigerant is confined by surface tension inside a porous metal matrix. Helium-4 and helium-3 gases were condensed and held in a copper matrix. Evaporative cooling of confined liquid helium-4 resulted in a temperature of 1.4K. Using a zeolite adsorption pump external to the cryostat, a temperature of 0.6 K was achieved through evaporative cooling of liquid helium-3. The amount of time required for complete evaporation of a controlled mass of liquid helium-4 contained in the copper matrix was measured as a function of the applied background power. For heating powers below 18 mW the measured times are consistent with the normal boiling of the confined volume of liquid refrigerant. At background powers above 18 mW the rapid rise in the temperature of the copper matrix the signature of the absence of confined liquid occurs in a time a factor of two shorter than that expected on the basis of an extrapolation of the low power data.

  9. Heat transfer through cyanate ester epoxy mix and epoxy TGPAP - DETDA electrical insulations at superfluid helium temperature

    NASA Astrophysics Data System (ADS)

    Pietrowicz, Slawomir; Four, Aurelian; Canfer, Simon; Jones, Stephanie; Baudouy, Bertrand

    2012-06-01

    A high magnetic field accelerator magnet of 13 T is being developed in Work Package 7 of the European Union FP7 project EuCARD. The application is to enable higher luminosities and energies for accelerators such as the LHC. The high magnetic field demands superconductors that require a heat treatment step such as Nb3Sn. This paper reports thermal tests on conventional composite electrical insulation with pressurized superfluid helium at atmospheric pressure as a coolant. Two composite insulation systems composed of cyanate ester epoxy mix or a tri-functional epoxy (TGPAP-DETDA) with Sglass fiber, have been chosen as candidate materials. The knowledge of their thermal properties is necessary for the thermal design and therefore samples have been tested in pressurized He II where heat is applied perpendicularly to the fibers between 1.6 K and 2.0 K. Overall thermal resistance is determined as a function of temperature and the results are compared with other electrical insulation systems used for accelerator magnets.

  10. High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets

    SciTech Connect

    Volk, Alexander; Thaler, Philipp; Koch, Markus; Ernst, Wolfgang E.; Fisslthaler, Evelin; Grogger, Werner

    2013-06-07

    We present a first investigation of structural properties of Ag clusters with a diameter of up to 5.5 nm grown inside superfluid helium nanodroplets (He{sub N}) and deposited on an amorphous C surface. With high resolution transmission electron microscope images we are able to show that in addition to the crystalline face centered cubic (fcc) structure, noncrystalline icosahedral (Ih), and decahedral (Dh) morphologies are grown. Relative abundances (56% fcc, 31% Dh, and 13% Ih) as well as the size distribution of each morphology (mean diameters d{sub fcc}=2.62(5) nm, d{sub Dh}=3.34(7) nm, and d{sub Ih}=3.93(2) nm) do not reflect the situation expected from pure energetic considerations, where small Ihs should be followed by medium sized Dhs and large fccs. Instead, kinetic factors seem to play an important role in the formation of these structures, as it appears to be the case for clusters formed by inert gas aggregation. Considering the low temperatures (0.37 K) and extremely high cooling rates, we discuss basic ideas that might lead to a qualitative picture of the cluster formation process inside He{sub N}.

  11. High resolution electron microscopy of Ag-clusters in crystalline and non-crystalline morphologies grown inside superfluid helium nanodroplets.

    PubMed

    Volk, Alexander; Thaler, Philipp; Koch, Markus; Fisslthaler, Evelin; Grogger, Werner; Ernst, Wolfgang E

    2013-06-07

    We present a first investigation of structural properties of Ag clusters with a diameter of up to 5.5 nm grown inside superfluid helium nanodroplets (He(N)) and deposited on an amorphous C surface. With high resolution transmission electron microscope images we are able to show that in addition to the crystalline face centered cubic (fcc) structure, noncrystalline icosahedral (Ih), and decahedral (Dh) morphologies are grown. Relative abundances (56% fcc, 31% Dh, and 13% Ih) as well as the size distribution of each morphology (mean diameters d(fcc)=2.62(5) nm, d(Dh)=3.34(7) nm, and d(Ih)=3.93(2) nm) do not reflect the situation expected from pure energetic considerations, where small Ihs should be followed by medium sized Dhs and large fccs. Instead, kinetic factors seem to play an important role in the formation of these structures, as it appears to be the case for clusters formed by inert gas aggregation. Considering the low temperatures (0.37 K) and extremely high cooling rates, we discuss basic ideas that might lead to a qualitative picture of the cluster formation process inside He(N).

  12. Stabilization of He2(A(sup 3)Sigma(sub u)(+)) molecules in liquid helium by optical pumping for vacuum UV laser

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J. S. (Inventor)

    1978-01-01

    A technique is disclosed for achieving large populations of metastable spin-aligned He2(a 3 Sigma u +) molecules in superfluid helium to obtain lasing in the vacuum ultraviolet wavelength regime around 0.0800 micron m by electronically exciting liquid (superfluid) helium with a comparatively low-current electron beam and spin aligning the metastable molecules by means of optical pumping with a modestly-powered (100mW) circularly-polarized continuous wave laser operating at, for example, 0.9096 or 0.4650 micron m. Once a high concentration of spin-aligned He2 (a 3 Sigma u +) is achieved with lifetimes of a few milliseconds, a strong microwave signal destroys the spin alignment and induces a quick collisional transition of He2 (a 3 Sigma u +) molecules to the a 1 Sigma u + state and thereby a lasing transition to the X 1 Sigma g + state.

  13. Liquid helium management for Gravity Probe-B

    NASA Technical Reports Server (NTRS)

    Schafer, C. F.

    1982-01-01

    The Gravity Probe-B (GP-B) experiment will be degraded if accelerations at a proof mass become larger than one ten billionth g. This makes necessary the management of the configuration and dynamical behavior of the large amount of liquid helium present in the GP-B spacecraft dewar. Three approaches to the solution of this problem are discussed. It is concluded that the most promising technique involves the use of baffles into which the liquid helium can be forced during a relatively high spacecraft rotation period, and in which the liquid helium will be held by capillary forces during the operational period when the rotation rate is much lower. Some likely baffle configurations are suggested.

  14. Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Douberly, Gary E.; Jäger, Wolfgang

    2014-07-01

    Methanol is one of the simplest molecules that undergo torsional oscillations, and so it has been extensively studied in the gas phase by various spectroscopic techniques. At 300 K, a large number of rotational, torsional, and vibrational energy levels is populated, and this makes for a rather complicated spectrum, which is still not fully understood. It is expected that in going from 300 K to 0.4 K (the temperature of helium nanodroplets) the population distribution of methanol will mainly collapse into two states; the JK = 00 state for the A1 nuclear spin symmetry species (with ICH3 = 3/2), and the JK = 1-1 state for the E species (ICH3 = 1/2). This results in a simplified spectrum that consists of narrow a-type (ΔK = 0) lines and broader b- and c-type (ΔK = ±1) lines. We have recorded the rotovibrational spectrum of CH3OH in the OH stretching, CH3 stretching and bending, CH3 rocking, and CO stretching regions, and have firmly assigned five bands (v1, v2, v3, v7, and v8), and tentatively assigned five others (v9, 2v4, v4 + v10, 2v10, and v4 + v5). To our knowledge, the transitions we have assigned within the v4 + v10, 2v10, and v4 + v5 bands have not yet been assigned in the gas phase, and we hope that considering the very small "matrix" shift in helium nanodroplets (<1 cm-1 for most subband origins of CH3OH), those made here can aid in their gas phase identification. Microwave-infrared double resonance spectroscopy was used to confirm the initially tentative a-type infrared assignments in the OH stretching (v1) band of A1 species methanol, in addition to revealing "warm" b-type lines. From a rotovibrational analysis, the B rotational constant is found to be reduced quite significantly (56%) with respect to the gas phase, and the torsional tunneling splittings are relatively unaffected and are at most reduced by 16%. While most rovibrational peaks are Lorentzian shaped, and those which are significantly perturbed by vibrational coupling in the gas phase are

  15. Pressure driven flow studies of superfluid helium-4 through single, high aspect ratio nanopipes

    NASA Astrophysics Data System (ADS)

    Botimer, Jeffrey; Taborek, Peter

    We have measured flow rates of helium-4 through high aspect ratio (>10,000) single glass nanopipes and etched nanopores under the influence of a pressure drop. The initial diameter of the glass pipes is 200nm while the initial diameter of the nanopores is approximately 80nm; the diameter of both types of nanopipe were reduced using atomic layer deposition(ALD) of Al2O3. Flow rates were measured for a wide range of temperatures (0.8K to 3.0K), pressures (up to 40 atm), and pipe lengths (0.8 mm to 30 mm). We observed flow velocities in the range of 1-6 m/s which has a power law dependence on pressure. Flow appears to be governed by turbulence at low temperatures. We have found evidence for a critical pressure above which turbulent flow is eliminated. This critical pressure appears to depend on temperature.

  16. Optical and Electron Spin Resonance Studies of Destruction of Porous Structures Formed by Nitrogen-Rare Gas Nanoclusters in Bulk Superfluid Helium

    NASA Astrophysics Data System (ADS)

    McColgan, Patrick T.; Meraki, Adil; Boltnev, Roman E.; Lee, David M.; Khmelenko, Vladimir V.

    2016-11-01

    We studied optical and electron spin resonance spectra during destruction of porous structures formed by nitrogen-rare gas (RG) nanoclusters in bulk superfluid helium containing high concentrations of stabilized nitrogen atoms. Samples were created by injecting products of a radio frequency discharge of nitrogen-rare gas-helium gas mixtures into bulk superfluid helium. These samples have a high energy density allowing the study of energy release in chemical processes inside of nanocluster aggregates. The rare gases used in the studies were neon, argon, and krypton. We also studied the effects of changing the relative concentrations between nitrogen and rare gas on thermoluminescence spectra during destruction of the samples. At the beginning of the destructions, α -group of nitrogen atoms, Vegard-Kaplan bands of N_2 molecules, and β -group of O atoms were observed. The final destruction of the samples were characterized by a series bright flashes. Spectra obtained during these flashes contain M- and β -bands of NO molecules, the intensities of which depend on the concentration of molecular nitrogen in the gas mixture as well as the type of rare gas present in the gas mixture.

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

    NASA Astrophysics Data System (ADS)

    Lebrun, Philippe; Parma, Vittorio; Tavian, Laurent

    2014-01-01

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

  18. Optical and Electron Spin Resonance Studies of Destruction of Porous Structures Formed by Nitrogen-Rare Gas Nanoclusters in Bulk Superfluid Helium

    NASA Astrophysics Data System (ADS)

    McColgan, Patrick T.; Meraki, Adil; Boltnev, Roman E.; Lee, David M.; Khmelenko, Vladimir V.

    2017-04-01

    We studied optical and electron spin resonance spectra during destruction of porous structures formed by nitrogen-rare gas (RG) nanoclusters in bulk superfluid helium containing high concentrations of stabilized nitrogen atoms. Samples were created by injecting products of a radio frequency discharge of nitrogen-rare gas-helium gas mixtures into bulk superfluid helium. These samples have a high energy density allowing the study of energy release in chemical processes inside of nanocluster aggregates. The rare gases used in the studies were neon, argon, and krypton. We also studied the effects of changing the relative concentrations between nitrogen and rare gas on thermoluminescence spectra during destruction of the samples. At the beginning of the destructions, α -group of nitrogen atoms, Vegard-Kaplan bands of N_2 molecules, and β -group of O atoms were observed. The final destruction of the samples were characterized by a series bright flashes. Spectra obtained during these flashes contain M- and β -bands of NO molecules, the intensities of which depend on the concentration of molecular nitrogen in the gas mixture as well as the type of rare gas present in the gas mixture.

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

    SciTech Connect

    Lebrun, Philippe; Parma, Vittorio; Tavian, Laurent

    2014-01-29

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

  20. Design and operation of a horizontal liquid helium flow facility

    SciTech Connect

    Van Sciver, S.W.; Wiesend, J.G. II

    1988-01-01

    The University of Wisconsin horizontal liquid helium flow facility (LHFF) consists of a five meter long 20 cm ID horizontal dewar connected to two end boxes. Several heat exchanger inserts have been built to allow variable temperature operation of 1.6 K less than or equal to T less than or equal to 4.2 K. A centrifugal pump is installed at one end of the facility permitting experiments in forced flow liquid helium up to 100 gm/s. The horizontal design allows experimentation on long straight test sections which may be used either to study fundamental properties of heat and mass transfer in helium or prototype cryogenic components under realistic conditions. A detailed description of the design and operating experience of the LHFF is presented. 5 refs., 5 figs.

  1. Single and double resonance spectroscopy of methanol embedded in superfluid helium nanodroplets

    SciTech Connect

    Raston, Paul L.; Douberly, Gary E.; Jäger, Wolfgang

    2014-07-28

    Methanol is one of the simplest molecules that undergo torsional oscillations, and so it has been extensively studied in the gas phase by various spectroscopic techniques. At 300 K, a large number of rotational, torsional, and vibrational energy levels is populated, and this makes for a rather complicated spectrum, which is still not fully understood. It is expected that in going from 300 K to 0.4 K (the temperature of helium nanodroplets) the population distribution of methanol will mainly collapse into two states; the J{sub K} = 0{sub 0} state for the A{sub 1} nuclear spin symmetry species (with I{sub CH{sub 3}} = 3/2), and the J{sub K} = 1{sub −1} state for the E species (I{sub CH{sub 3}} = 1/2). This results in a simplified spectrum that consists of narrow a-type (ΔK = 0) lines and broader b- and c-type (ΔK = ±1) lines. We have recorded the rotovibrational spectrum of CH{sub 3}OH in the OH stretching, CH{sub 3} stretching and bending, CH{sub 3} rocking, and CO stretching regions, and have firmly assigned five bands (v{sub 1}, v{sub 2}, v{sub 3}, v{sub 7}, and v{sub 8}), and tentatively assigned five others (v{sub 9}, 2v{sub 4}, v{sub 4} + v{sub 10}, 2v{sub 10}, and v{sub 4} + v{sub 5}). To our knowledge, the transitions we have assigned within the v{sub 4} + v{sub 10}, 2v{sub 10}, and v{sub 4} + v{sub 5} bands have not yet been assigned in the gas phase, and we hope that considering the very small “matrix” shift in helium nanodroplets (<1 cm{sup −1} for most subband origins of CH{sub 3}OH), those made here can aid in their gas phase identification. Microwave-infrared double resonance spectroscopy was used to confirm the initially tentative a-type infrared assignments in the OH stretching (v{sub 1}) band of A{sub 1} species methanol, in addition to revealing “warm” b-type lines. From a rotovibrational analysis, the B rotational constant is found to be reduced quite significantly (56%) with respect to the gas phase, and the torsional tunneling

  2. The Ethyl Radical in Superfluid Helium Nanodroplets: Rovibrational Spectroscopy and AB Initio Calcluations

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Moradi, Christopher P.; Agarwal, Jay; Turney, Justin. M.; Schaefer, Henry F. Schaefer, Iii; Douberly, Gary E.

    2013-06-01

    The ethyl radical has been isolated and spectroscopically characterized in ^4He nanodroplets. The five fundamental CH stretch bands are observed near 3 μm and have band origins shifted < 1 wn from those reported for the gas phase species. The symmetric CH_2 stretching band (ν_1) is rotationally resolved, revealing nuclear spin statistical weights predicted by G_{12} permutation-inversion group theory. A permanent electric dipole moment of 0.28 (2) D is obtained via the Stark spectrum of the ν_1 band. The four other CH stretch fundamental bands are broadened in helium droplets and lack rotational fine structure. The approximately 1-2 wn line widths for these bands are attributed to the homogeneous broadening associated with solvent-mediated rovibrational relaxation dynamics. In addition to these five fundamentals, three A_1' overtone/combination bands are observed and have resolved rotational substructure. These are assigned to the 2ν_{12}, ν_4+ν_6, and 2ν_6 bands through comparisons to anharmonic frequency computations at the CCSD(T)/cc-pVTZ level of theory. S. Davis, D. Uy, D. J. Nesbitt. J. Chem. Phys. 112, 1823-1834 (2000). T. Haber, A. C. Blair, D. J. Nesbitt, M. D. Schuder. J. Chem. Phys. 124, 054316 (2006).

  3. Electronic Relaxation after Resonant Laser Excitation of Cr in Superfluid Helium Nanodroplets

    PubMed Central

    2013-01-01

    Chromium (Cr) atoms embedded into helium nanodroplets (HeN) are ejected from the droplets upon photoexcitation. During ejection they undergo electronic relaxation resulting in bare Cr atoms in various excited states. In a study of the relaxation process we present absorption spectra observed via laser induced fluorescence and beam depletion as well as dispersed fluorescence spectra and time-resolved fluorescence measurements. Broad and shifted absorption structures were found for the strong z7P° ← a7S3 and y7P° ← a7S3 excitations from the ground state. Emission lines are, in contrast, very narrow, which indicates that fluorescence is obtained from bare excited Cr atoms after ejection. Upon excitation into the y7P2,3,4° states we observed fluorescence from y7P2°, z5P1,2,3°, and z7P2,3,4°, indicating that these states are populated by electronic relaxation during the ejection processes. Relative population ratios are obtained from the intensities of individual spectral lines. Excitation into the z7P2,3,4° states resulted in fluorescence only from z7P2°. Estimates of the time duration of the ejection process are obtained from time-resolved measurements. PMID:23410146

  4. A demountable nonmagnetic multiconductor feedthrough suitable for use in liquid helium applications

    NASA Astrophysics Data System (ADS)

    Bass, Christopher D.

    2008-05-01

    A superfluid-helium-tight nonmagnetic electrical feedthrough has been developed by using brass pins embedded within an epoxy resin plug and mounted on a beryllium copper Conflat flange. A method for building these feedthroughs is discussed, and their performance history is described.

  5. Microscopic molecular superfluid response: theory and simulations

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Roy, Pierre-Nicholas

    2014-04-01

    Since its discovery in 1938, superfluidity has been the subject of much investigation because it provides a unique example of a macroscopic manifestation of quantum mechanics. About 60 years later, scientists successfully observed this phenomenon in the microscopic world though the spectroscopic Andronikashvili experiment in helium nano-droplets. This reduction of scale suggests that not only helium but also para-H2 (pH2) can be a candidate for superfluidity. This expectation is based on the fact that the smaller number of neighbours and surface effects of a finite-size cluster may hinder solidification and promote a liquid-like phase. The first prediction of superfluidity in pH2 clusters was reported in 1991 based on quantum Monte Carlo simulations. The possible superfluidity of pH2 was later indirectly observed in a spectroscopic Andronikashvili experiment in 2000. Since then, a growing number of studies have appeared, and theoretical simulations have been playing a special role because they help guide and interpret experiments. In this review, we go over the theoretical studies of pH2 superfluid clusters since the experiment of 2000. We provide a historical perspective and introduce the basic theoretical formalism along with key experimental advances. We then present illustrative results of the theoretical studies and comment on the possible future developments in the field. We include sufficient theoretical details such that the review can serve as a guide for newcomers to the field.

  6. Formation of Positively Charged Liquid Helium Clusters in Supercritical Helium and their Solidification upon Compression.

    PubMed

    Tarchouna, Hejer Gharbi; Bonifaci, Nelly; Aitken, Frédéric; Mendoza Luna, Luis Guillermo; von Haeften, Klaus

    2015-08-06

    Positively charged ions were produced in supercritical helium at temperatures from 6 to 10 K and up to 2 MPa using a corona discharge. Their mobility was measured via current-voltage curves, and the hydrodynamic radius was derived using Stokes law. An initial increase and subsequent decrease of hydrodynamic radius was observed and interpreted in terms of growth, compression and solidification of ion clusters. The mobility was modeled using a van der Waals-type thermodynamic state equation for the ion-in-helium mixed system and a temperature-dependent Millikan-Cunningham factor, describing experimental data both in the Knudsen and the Stokes flow region. Regions of maximum hydrodynamic radius and large compressibility were interpreted as boiling points. These points were modeled over a large range of pressures and found to match the Frenkel line of pure helium up to 0.7 MPa, reflecting similarity of density fluctuations in pure supercritical helium and gas-liquid phase transitions of ionic helium clusters.

  7. Heat transfer to liquid and supercritical helium in superconducting rotors

    SciTech Connect

    Nakajima, R.; Sato, K.; Miyaike, K.; Kumagai, M. ); Kobayashi, Y. )

    1992-12-01

    This paper reports on cooling designs of superconducting generator rotors which are quite important for maintaining a stable superconducting state of field windings, and it is essential to comprehend the heat transfer characteristics of helium in rotating fields. Experiments were carried out using a large-scale rotating cryostat with a cold rotor diameter of approximately 800 mm. The heat transfer characteristics of liquid and supercritical helium under conditions of gravitational and centrifugal acceleration fields (maximum: approx. 3000 g at the refrigerant outer side in the rotor) with heat-transfer surfaces horizontal upward facing and perpendicular to such fields, radial and axial channels, and dummy winding cooling surfaces were obtained.

  8. Spectroscopy of barium atoms in liquid and solid helium matrices

    NASA Astrophysics Data System (ADS)

    Lebedev, V.; Moroshkin, P.; Weis, A.

    2011-08-01

    We present an exhaustive overview of optical absorption and laser-induced fluorescence lines of Ba atoms in liquid and solid helium matrices in visible and near-infrared spectral ranges. Due to the increased density of isolated atoms, we have found a large number of spectral lines that were not observed in condensed helium matrices before. We have also measured the lifetimes of metastable states. The lowest 3D1 metastable state has lifetime of 2.6 s and can be used as an intermediate state in two-step excitations of high-lying states. Various matrix-induced radiationless population transfer channels have been identified.

  9. Microscopic Superfluidity of Small 4He and Para-He2 Clusters Inside Helium Droplets

    NASA Astrophysics Data System (ADS)

    Toennies, J. P.

    The present review describes recent molecular beam experiments in which large 4He or 3He liquid droplets consisting typically of 103 to 104 atoms are produced and doped by pick-up of single atomic or molecular chromophores. The spectroscopy of these single particles has led to new detailed insight into the elementary microscopic interactions of the probe particles with their environment. In the visible the spectral features are unusually sharp with line widths comparable to those of the free molecules. The phonon wings of vibronic transitions give direct evidence that the droplets are supernuid. In the infra-red well defined rotational lines appear that indicate that the molecules rotate freely inside the Uquid. From the intensities of the sharp lines temperatures of 0.37 K and about 0.14 K are determined for 4He and 3He droplets, respectively. These experiments demonstrate that supernuid 4He droplets provide a new ultra cold uniquely gentle matrix for high resolution spectroscopy. At the same time the molecular spectra contribute new microscopic insight into the intriguing phenomenon of superfluidity. This last aspect will be emphasized in this review. Several reviews which emphasize more the new opportunities for high resolution spectroscopy, 1 - 4 an introductory overview 5 and a special issue of the Journal of Chemical Physics have recently been published. 6 - 8

  10. Superconducting cable cooling system by helium gas and a mixture of gas and liquid helium

    DOEpatents

    Dean, John W.

    1977-01-01

    Thermally contacting, oppositely streaming cryogenic fluid streams in the same enclosure in a closed cycle that changes from a cool high pressure helium gas to a cooler reduced pressure helium fluid comprised of a mixture of gas and boiling liquid so as to be near the same temperature but at different pressures respectively in go and return legs that are in thermal contact with each other and in thermal contact with a longitudinally extending superconducting transmission line enclosed in the same cable enclosure that insulates the line from the ambient at a temperature T.sub.1. By first circulating the fluid in a go leg from a refrigerator at one end of the line as a high pressure helium gas near the normal boiling temperature of helium; then circulating the gas through an expander at the other end of the line where the gas becomes a mixture of reduced pressure gas and boiling liquid at its boiling temperature; then by circulating the mixture in a return leg that is separated from but in thermal contact with the gas in the go leg and in the same enclosure therewith; and finally returning the resulting low pressure gas to the refrigerator for compression into a high pressure gas at T.sub.2 is a closed cycle, where T.sub.1 >T.sub.2, the temperature distribution is such that the line temperature is nearly constant along its length from the refrigerator to the expander due to the boiling of the liquid in the mixture. A heat exchanger between the go and return lines removes the gas from the liquid in the return leg while cooling the go leg.

  11. Development of a Novel Method for the Exploration of the Thermal Response of Superfluid Helium Cooled Superconducting Cables to Pulse Heat Loads

    NASA Astrophysics Data System (ADS)

    Winkler, T.; Koettig, T.; van Weelderen, R.; Bremer, J.; ter Brake, H. J. M.

    Management of transient heat deposition in superconducting magnets and its extraction from the aforementioned is becoming increasingly important to bring high energy particle accelerator performance to higher beam energies and intensities. Precise knowledge of transient heat deposition phenomena in the magnet cables will permit to push the operation of these magnets as close as possible to their current sharing limit, without unduly provoking magnet quenches. With the prospect of operating the Large Hadron Collider at CERN at higher beam energies and intensities an investigation into the response to transient heat loads of LHC magnets, operating in pressurized superfluid helium, is being performed. The more frequently used approach mimics the cable geometry by resistive wires and uses Joule-heating to deposit energy. Instead, to approximate as closely as possible the real magnet conditions, a novel method for depositing heat in cable stacks made out of superconducting magnet-cables has been developed. The goal is to measure the temperature difference as a function of time between the cable stack and the superfluid helium bath depending on heat load and heat pulse length. The heat generation in the superconducting cable and precise measurement of small temperature differences are major challenges. The functional principle and experimental set-up are presented together with proof of principle measurements.

  12. Superfluidity, Bose-Einstein condensation and dimensions of liquid 4He in nanopores

    NASA Astrophysics Data System (ADS)

    Vranješ Markić, Leandra; Glyde, Henry

    Path integral Monte Carlo (PIMC) calculations of the superfluid fraction, ρS / ρ , and the one-body density matrix (OBDM) (Bose-Einstein condensation (BEC)) of liquid 4He confined in nanopores are presented. The goal is to determine the effective dimensions of the liquid in the nanopore. We simulate a cylinder of liquid of diameter dL surrounded by 5 Åof inert solid 4He in a nanopore of diameter d; d = dL + 10 Å. The PIMC ρS (T) / ρ and OBDM scales as a 1D Luttinger Liquid at extremely small liquid pore diameters only, dL = 6 Åwhere the liquid atoms form a 1D line at the center of the pore. In the range 8 <=dL <= 22 Åthe PIMC ρS (T) / ρ scales as a 2D liquid. In this dL range the liquid fills the pores in cylindrical layers. There is a cross over from 2D to 3D scaling at larger dL ~= 22 Å. In the range 8 <=dL <= 22 Å, the TC predicted using the Kosterlitz-Thouless 2D scaling criterion of the OBDM agrees well with the TC obtained from ρS (T) / ρ . Superflow observed in pores of diameter (18 < d < 32 Å) is apparently standard static superflow with the low TC arising from its 2D character. Supported by Office of Basic Energy Sciences, USDOE, ER46680.

  13. Design concept of cryogenic falling liquid film helium separator

    SciTech Connect

    Kinoshita, M.; Yamanishi, T.; Bartlit, J.R.; Sherman, R.H.

    1986-07-01

    A design concept is developed for a cryogenic falling liquid film helium separator by clarifying the differences between this process and a cryogenic distillation column. The process characteristics are greatly improved by the idea of adding an H/sub 2/ gas flow to a point near the upper end of the packed section. The flow rate of tritium lost from the top is kept extremely low with an adequately short packed section, and the column pressure is reduced to 1 atm. The addition causes no appreciable increase in the protium percentage (approx. =1%) in the bottom liquid flow. A design procedure applying the Colburn-Hougen method is proposed for determining specifications of the refrigerated section. It is shown that the presence of noncondensible helium requires a significantly larger heat transfer area mainly because the mass transfer resistance increases enormously as the condensation of hydrogen isotopes proceeds. Control schemes are also proposed: The tritium concentration in the top gas is controlled by the H/sub 2/ gas flow rate. The pressure rise caused by an increase of the helium percentage within the refrigerated section, which cannot readily be eliminated by changing input specifications of the refrigerant gas, is avoided by increasing the top gas flow rate to release more helium from the top.

  14. Numerical studies of the surface tension effect of cryogenic liquid helium

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1994-01-01

    The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose of performing scientific observation during the normal spacecraft operation is investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics has been based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers, have been derived.

  15. Development of a Cryogenic Capability for Shock Compression of Liquid Helium on the Z machine

    NASA Astrophysics Data System (ADS)

    Lopez, Andrew; Root, Seth; Shelton, Keegan; Villalva, Jose; Hanson, David

    2015-06-01

    A cryogenic system has been developed to generate liquid helium (LHe) samples at 2.1 K for high precision equation-of-state (EOS) and isentropic compression measurements using the Z machine. Accurate data on He properties at Mbar pressures are critical to understanding gas giant planetary interiors and for validating first principles density functional simulations; however, limited high pressure He EOS data exist due to difficulty in condensing LHe samples (<3.5 K) for gas guns, magnetic and explosive devices and laser facilities. To address this need, we have developed and demonstrated a cryogenic system to generate quiescent superfluid LHe samples (2.1 K). The cryostat system utilizes a conduction refrigerator with a pumped LHe reservoir to cool the cryocell. The cryostat design produces stable, controlled temperatures resulting in well-characterized initial states of liquid He samples, which is key for precision EOS measurements. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.

  16. Mathematical Model of Bubble Sloshing Dynamics for Cryogenic Liquid Helium in Orbital Spacecraft Dewar Container

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Pan, H. L.

    1995-01-01

    A generalized mathematical model is investigated of sloshing dynamics for dewar containers, partially filled with a liquid of cryogenic superfluid helium 2, driven by both gravity gradient and jitter accelerations applicable to two types of scientific spacecrafts, which are eligible to carry out spinning motion and/or slew motion to perform scientific observations during normal spacecraft operation. Two examples are given for the Gravity Probe-B (GP-B) with spinning motion, and the Advanced X-Ray Astrophysics Facility-Spectroscopy (AXAF-S) with slew motion, which are responsible for the sloshing dynamics. Explicit mathematical expressions for the modelling of sloshing dynamics to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics will be based on the noninertial frame spacecraft bound coordinate, and we will solve the time-dependent three-dimensional formulations of partial differential equations subject to initial and boundary conditions. Explicit mathematical expressions of boundary conditions lo cover capillary force effects on the liquid-vapor interface in microgravity environments are also derived. Results of the simulations of the mathematical model are illustrated.

  17. Emergency relief venting of the infrared telescope liquid helium dewar

    NASA Technical Reports Server (NTRS)

    Urban, E. W.

    1980-01-01

    An analysis is made of the emergency relief venting of the liquid helium dewar of the Spacelab 2 infrared telescope experiment in the event of a massive failure of the dewar guard vacuum. Such a failure, resulting from a major accident, could cause rapid heating and pressurization of the liquid helium in the dewar and lead to relief venting through the emergency relief system. The heat input from an accident is estimated for various fluid conditions in the dewar and the relief process as it takes place through one or both of the emergency relief paths is considered. It is shown that under all reasonable circumstances the dewar will safely relieve itself, and the pressure will not exceed 85 percent of the proof pressure or 63 percent of the burst pressure.

  18. Shock compression of liquid helium and helium-hydrogen mixtures : development of a cryogenic capability for shock compression of liquid helium on Z, final report for LDRD Project 141536.

    SciTech Connect

    Lopez, Andrew J.; Knudson, Marcus D.; Shelton, Keegan P.; Hanson, David Lester

    2010-10-01

    This final report on SNL/NM LDRD Project 141536 summarizes progress made toward the development of a cryogenic capability to generate liquid helium (LHe) samples for high accuracy equation-of-state (EOS) measurements on the Z current drive. Accurate data on He properties at Mbar pressures are critical to understanding giant planetary interiors and for validating first principles density functional simulations, but it is difficult to condense LHe samples at very low temperatures (<3.5 K) for experimental studies on gas guns, magnetic and explosive compression devices, and lasers. We have developed a conceptual design for a cryogenic LHe sample system to generate quiescent superfluid LHe samples at 1.5-1.8 K. This cryogenic system adapts the basic elements of a continuously operating, self-regulating {sup 4}He evaporation refrigerator to the constraints of shock compression experiments on Z. To minimize heat load, the sample holder is surrounded by a double layer of thermal radiation shields cooled with LHe to 5 K. Delivery of LHe to the pumped-He evaporator bath is controlled by a flow impedance. The LHe sample holder assembly features modular components and simplified fabrication techniques to reduce cost and complexity to levels required of an expendable device. Prototypes have been fabricated, assembled, and instrumented for initial testing.

  19. Superfluid Boundary Layer

    NASA Astrophysics Data System (ADS)

    Stagg, G. W.; Parker, N. G.; Barenghi, C. F.

    2017-03-01

    We model the superfluid flow of liquid helium over the rough surface of a wire (used to experimentally generate turbulence) profiled by atomic force microscopy. Numerical simulations of the Gross-Pitaevskii equation reveal that the sharpest features in the surface induce vortex nucleation both intrinsically (due to the raised local fluid velocity) and extrinsically (providing pinning sites to vortex lines aligned with the flow). Vortex interactions and reconnections contribute to form a dense turbulent layer of vortices with a nonclassical average velocity profile which continually sheds small vortex rings into the bulk. We characterize this layer for various imposed flows. As boundary layers conventionally arise from viscous forces, this result opens up new insight into the nature of superflows.

  20. Liquid to gas leak ratios with liquid nitrogen and liquid helium

    SciTech Connect

    Batzer, T.H.; Call, W.R.

    1985-02-26

    To predict the leak rates of liquid helium and liquid nitrogen containers at operating conditions we need to know how small leaks (10/sup -8/ to 10/sup -5/ atm-cm/sup 3/ air/s), measured at standard conditions, behave when flooded with these cryogens. Two small leaks were measured at ambient conditions (approx.750 Torr and 295 K), at the normal boiling points of LN/sub 2/ and LHe, and at elevated pressures above the liquids. The ratios of the leak rates of the liquids at ambient pressure to the gases (G) at ambient pressure and room temperature were: GN/sub 2/(1), LN/sub 2/(18), GHe(1), and LHe(172). The leak rate ratio of LN/sub 2/ at elevated pressure was linear with pressure. The leak rate ratio of LHe at elevated pressure was also linear with pressure.

  1. Communication: Dopant-induced solvation of alkalis in liquid helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Renzler, Michael; Daxner, Matthias; Kranabetter, Lorenz; Kaiser, Alexander; Hauser, Andreas W.; Ernst, Wolfgang E.; Lindinger, Albrecht; Zillich, Robert; Scheier, Paul; Ellis, Andrew M.

    2016-11-01

    Alkali metal atoms and small alkali clusters are classic heliophobes and when in contact with liquid helium they reside in a dimple on the surface. Here we show that alkalis can be induced to submerge into liquid helium when a highly polarizable co-solute, C60, is added to a helium nanodroplet. Evidence is presented that shows that all sodium clusters, and probably single Na atoms, enter the helium droplet in the presence of C60. Even clusters of cesium, an extreme heliophobe, dissolve in liquid helium when C60 is added. The sole exception is atomic Cs, which remains at the surface.

  2. 136. VIEW OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN LIQUID NITROGEN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    136. VIEW OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN LIQUID NITROGEN CONTROL ROOM (115), LSB (BLDG. 770), FROM FUEL APRON WITH BAY DOOR OPEN - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 West, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

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

    NASA Technical Reports Server (NTRS)

    Kogut, Alan; James, Bryan; Fixsen, Dale

    2013-01-01

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

  4. Relativistic superfluidity and vorticity from the nonlinear Klein-Gordon equation

    NASA Astrophysics Data System (ADS)

    Xiong, Chi; Good, Michael R. R.; Guo, Yulong; Liu, Xiaopei; Huang, Kerson

    2014-12-01

    We investigate superfluidity, and the mechanism for creation of quantized vortices, in the relativistic regime. The general framework is a nonlinear Klein-Gordon equation in curved spacetime for a complex scalar field, whose phase dynamics gives rise to superfluidity. The mechanisms discussed are local inertial forces (Coriolis and centrifugal), and current-current interaction with an external source. The primary application is to cosmology, but we also discuss the reduction to the nonrelativistic nonlinear Schrödinger equation, which is widely used in describing superfluidity and vorticity in liquid helium and cold-trapped atomic gases.

  5. Hysteresis in a quantized superfluid 'atomtronic' circuit.

    PubMed

    Eckel, Stephen; Lee, Jeffrey G; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W; Lobb, Christopher J; Phillips, William D; Edwards, Mark; Campbell, Gretchen K

    2014-02-13

    Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits-it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose-Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices).

  6. Hysteresis in a quantized superfluid `atomtronic' circuit

    NASA Astrophysics Data System (ADS)

    Eckel, Stephen; Lee, Jeffrey G.; Jendrzejewski, Fred; Murray, Noel; Clark, Charles W.; Lobb, Christopher J.; Phillips, William D.; Edwards, Mark; Campbell, Gretchen K.

    2014-02-01

    Atomtronics is an emerging interdisciplinary field that seeks to develop new functional methods by creating devices and circuits where ultracold atoms, often superfluids, have a role analogous to that of electrons in electronics. Hysteresis is widely used in electronic circuits--it is routinely observed in superconducting circuits and is essential in radio-frequency superconducting quantum interference devices. Furthermore, it is as fundamental to superfluidity (and superconductivity) as quantized persistent currents, critical velocity and Josephson effects. Nevertheless, despite multiple theoretical predictions, hysteresis has not been previously observed in any superfluid, atomic-gas Bose-Einstein condensate. Here we directly detect hysteresis between quantized circulation states in an atomtronic circuit formed from a ring of superfluid Bose-Einstein condensate obstructed by a rotating weak link (a region of low atomic density). This contrasts with previous experiments on superfluid liquid helium where hysteresis was observed directly in systems in which the quantization of flow could not be observed, and indirectly in systems that showed quantized flow. Our techniques allow us to tune the size of the hysteresis loop and to consider the fundamental excitations that accompany hysteresis. The results suggest that the relevant excitations involved in hysteresis are vortices, and indicate that dissipation has an important role in the dynamics. Controlled hysteresis in atomtronic circuits may prove to be a crucial feature for the development of practical devices, just as it has in electronic circuits such as memories, digital noise filters (for example Schmitt triggers) and magnetometers (for example superconducting quantum interference devices).

  7. Helium II level measurement techniques

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

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

  8. Crystallization of electrons on the surface of liquid helium

    NASA Astrophysics Data System (ADS)

    Grimes, C. C.; Adams, G.

    1980-08-01

    The classical, two-dimensional Coulomb system formed by a monolayer of electrons trapped on the surface of liquid helium has been observed to crystallize into a triangular lattice. Measured melting temperatures range from 0.37 to 0.65 K for areal densities of electrons from 3 × 10 8 cm -2 to 9 × 10 8 cm -2. Melting occurs at Γ = 131 ± 7 where Γ is a measure of the ratio of potential energy to kinetic energy per electron. The measured value of Γ at melting is consistent with dislocation mediated melting of a two-dimensional crystal.

  9. Fission of Multielectron Bubbles in Liquid Helium Under Electric Fields

    NASA Astrophysics Data System (ADS)

    Vadakkumbatt, V.; Ghosh, A.

    2017-06-01

    Multielectron bubbles (MEBs) are cavities in liquid helium which contain a layer of electrons trapped within few nanometres from their inner surfaces. These bubbles are promising candidates to probe a system of interacting electrons in curved geometries, but have been subjected to limited experimental investigation. Here, we report on the observation of fission of MEBs under strong electric fields, which arises due to fast rearrangement of electrons inside the bubbles, leading to their deformation and eventually instability. We measured the electrons to be distributed unequally between the daughter bubbles which could be used to control the charge density inside MEBs.

  10. Exploding and Imaging of Electron Bubbles in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Yadav, Neha; Vadakkumbatt, Vaisakh; Maris, Humphrey J.; Ghosh, Ambarish

    2016-11-01

    An electron bubble in liquid helium-4 under the saturated vapor pressure becomes unstable and explodes if the pressure becomes more negative than -1.9 bars. In this paper, we use focused ultrasound to explode electron bubbles. We then image at 30,000 frames per second the growth and subsequent collapse of the bubbles. We find that bubbles can grow to as large as 1 mm in diameter within 2 ms after the cavitation event. We examine the relation between the maximum size of the bubble and the lifetime and find good agreement with the experimental results.

  11. Collapse of Vapor-Filled Bubbles in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Pal, Anustuv; Joseph, Emil; Vadakkumbatt, Vaisakh; Yadav, Neha; Srinivasan, Vinod; Maris, Humphrey J.; Ghosh, Ambarish

    2017-08-01

    Multielectron bubbles (MEBs) are charged cavities in liquid helium which provide an interesting platform for the study of electrons on curved surfaces. Very recently, we have reported an experiment to trap these objects in a two-dimensional Paul trap, where they could be observed from ten to hundreds of milliseconds. During this time, the vapor inside the bubble condensed which resulted in a steady reduction in their size such that beyond a certain time the MEBs could no longer be detected. In this paper, we present experimental data on the lifetime of the bubbles as a function of their initial radius and compare the results with a theoretical model.

  12. Superconducting AC motor for centrifugal liquid helium pump

    SciTech Connect

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

    1982-01-01

    The behavior of flowmeters in liquid and supercritical helium is studied. A description is given of the motor and experimental apparatus. The initial results (torque vs. efficiency and power vs. slip) are chartered. The results obtained with an external rotating shield (torque vs. efficiency and power vs. slip) are also charted. One rotor provided a higher power particularly at the highest frequencies, provided that the critical point is not exceeded. Another rotor gives a better efficiency, particularly at the lowest frequencies. Recommendations for adopting a rotor design are given.

  13. Hot-wire anemometry for superfluid turbulent coflows.

    PubMed

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

    2015-02-01

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

  14. Hot-wire anemometry for superfluid turbulent coflows

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  16. Lars Onsager Prize Talk: Quantum fluids: from liquid helium to cold atoms

    NASA Astrophysics Data System (ADS)

    Pethick, Christopher

    2008-03-01

    The study of quantum liquids has led to ideas and concepts of broad applicability. I shall illustrate this by examples from the physics of liquid helium-3, heavy-fermion compounds, quark-gluon plasmas and cold atomic gases.

  17. The liquid helium thermosyphon for the GEM detector magnet

    SciTech Connect

    Warren, R.P.

    1993-05-04

    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.

  18. Advanced helium purge seals for Liquid Oxygen (LOX) turbopumps

    NASA Technical Reports Server (NTRS)

    Shapiro, Wilbur; Lee, Chester C.

    1989-01-01

    Program objectives were to determine three advanced configurations of helium buffer seals capable of providing improved performance in a space shuttle main engine (SSME), high-pressure liquid oxygen (LOX) turbopump environment, and to provide NASA with the analytical tools to determine performance of a variety of seal configurations. The three seal designs included solid-ring fluid-film seals often referred to as floating ring seals, back-to-back fluid-film face seals, and a circumferential sectored seal that incorporated inherent clearance adjustment capabilities. Of the three seals designed, the sectored seal is favored because the self-adjusting clearance features accommodate the variations in clearance that will occur because of thermal and centrifugal distortions without compromising performance. Moreover, leakage can be contained well below the maximum target values; minimizing leakage is important on the SSME since helium is provided by an external tank. A reduction in tank size translates to an increase in payload that can be carried on board the shuttle. The computer codes supplied under this program included a code for analyzing a variety of gas-lubricated, floating ring, and sector seals; a code for analyzing gas-lubricated face seals; a code for optimizing and analyzing gas-lubricated spiral-groove face seals; and a code for determining fluid-film face seal response to runner excitations in as many as five degrees of freedom. These codes proved invaluable for optimizing designs and estimating final performance of the seals described.

  19. Evidence of Bose-Einstein Condensation in solid helium

    NASA Astrophysics Data System (ADS)

    Chan, Moses H. W.

    2005-03-01

    The onset of superfluidity in liquid He-4 below 2.176K is associated with Bose-Einstein condensation where He-4 atoms condensed into a single momentum state and acquire quantum mechanical coherence over macroscopic length scales. Bose- Einstein condensation of alkali atoms in the vapor phase was achieved in 1995 and there is strong evidence for superfluidity in these systems. Perhaps counter to intuition, superfluid-like behavior is thought possible even in solid helium. Recent high Q torsional oscillator measurements found evidence of superflow in solid helium confined in porous media (1) and in bulk solid helium (2), indicating Bose-Einstein condensation very likely occurs in all three phases of matter. (1) E. Kim and M. H. W. Chan, Nature 427, 225 (2004) (2) E. Kim and M. H. W. Chan, Science 305, 1941 (2004).

  20. Infrared spectrum of the electron bubble in liquid helium

    NASA Astrophysics Data System (ADS)

    Grimes, C. C.; Adams, G.

    1990-04-01

    The energy of the ground-state-to-first-excited-state electronic transition in the electron bubble in liquid helium has been measured at 1.3 K and found to be 0.122 eV at a pressure of 1.1 atm and increasing to 0.209 eV at 18.3 atm. The spherical-square-well model of the electron bubble accounts well for the transition energies if the effective surface tension is taken to be independent of pressure. This model also yields improved values for the electron bubble radius as a function of pressure. The position of a line in the P-T plane where the photoconductivity signal vanishes indicates that trapping of electron bubbles on vorticity plays a role in the detection mechanism.

  1. Thermal conductance of pressed brass contacts at liquid helium temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, L. J.; Kittel, P.; Brooks, W. F.; Spivak, A. L.; Marks, W. G., Jr.

    1986-01-01

    An apparatus has been designed and fabricated which will measure the thermal conductance of pressed contacts at liquid helium temperatures as a function of applied force, with surface finish as a parameter. The apparatus is automated and was used to measure thermal conductance at temperatures from 1.5 to 6.5 K at applied forces up to 700 N for brass sample pairs having surface finishes from 0.1 to 1.6 micron rms. The experimental data were found to fit a simple power law where the thermal conductance is given by k = alpha T exp n, where k is the thermal conductance, T is the absolute temperature, and alpha and n are empirically determined constants.

  2. Thermal conductance of pressed contacts at liquid helium temperatures

    NASA Technical Reports Server (NTRS)

    Salerno, L. J.; Kittel, P.; Spivak, A. L.

    1983-01-01

    It is pointed out that the optimum design of cryogenic instruments requires accurate thermal models. The present models are limited by a lack of knowledge of the low temperature thermal conductance of the bolted joints which are typically used in the instrument-to-system interface. In connection with studies of pressed contacts, it has been found that the thermal conductance does not obey the Wiedemann-Franz law. The present investigation is concerned with the characterization of the thermal conductance of pressed contacts at liquid helium-4 temperatures, taking into account the dependence of thermal contact conductance on applied force and temperature. It is shown that for the 0.4 micron OFHC copper pressed contact pair, the thermal conductance varies roughly as the second power of the temperature, and increases with increasing applied force.

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

    SciTech Connect

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

    2014-03-31

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

  4. Superfluidity of a Fermi liquid from the viewpoint of a hierarchy of equations for reduced density matrices

    NASA Astrophysics Data System (ADS)

    Golovko, V. A.

    2004-04-01

    The hierarchy of equations for reduced density matrices relevant to thermodynamic equilibrium with account taken of the spin obtained earlier is modified in order to describe the state of a Fermi system with a condensate. Although the procedure is to some extent analogous with the one carried out by the author earlier for a Bose liquid peculiarities relevant to Fermi statistics complicate considerably the treatment. As in the case of the Bose liquid the condensate phase can be superfluid as well as nonsuperfluid, the physical causes of superfluidity being identical. A new mechanism of fermion pairing that acts even in the case of a purely repulsive Hamiltonian is pointed out. Special attention is given to the thermodynamics of a superfluid Fermi system. The example of a hard-sphere system is used to find out the form of phase diagrams, the character of the phase transition to a condensate phase and the properties of the last. Noticeable dissimilarities from a Bose system with the same Hamiltonian are revealed. Application of the present approach to superconductivity is discussed as well.

  5. Thermal characteristics of a low-loss liquid-helium dewar

    SciTech Connect

    Cha, Y.S.; Niemann, R.C.; Hull, J.R.

    1994-05-01

    A liquid helium dewar has been designed, fabricated, and operated successfully with a minimum background heat-loss rate of only a few milliwatts. The objective is to provide a facility that can be used to measure relatively low heat-loss rate (1--100 milliwatts) in a liquid helium environment. The experimental system consists mainly of an inner helium reservoir within an outer helium reservoir that is thermally shielded from the room-temperature environment by multiple insulation layers in a vacuum environment and a liquid nitrogen reservoir. The inner helium reservoir has a reduced cross-sectional (neck) area to minimize radiative and convective heat transfer to the liquid helium in the lower portion of the reservoir. Experimental results indicate that it takes a long time (>16 hours) for the system to cool down and reach the minimum heat-loss condition. Strong thermal interactions were observed between the inner and the outer reservoirs above the reduced cross-sectional area of the inner reservoir which is separated from the outer reservoir by a cylindrical stainless steel wall. Temperature measurements showed stratification in the vapor space above the liquid helium in the inner reservoir. Temperature distributions in the vapor space are not one-dimensional, and horizontal temperature gradients exist; this strongly suggests that natural convection may have persisted in the vapor space above the liquid helium in the inner reservoir. To alleviate the problem of strong thermal interactions between the inner and the outer reservoirs, we have since redesigned and tested an improved inner helium reservoir. The new reservoir has a heat intercept, an extended vacuum insulating space between the two helium reservoirs above the heat intercept, and an upper portion made of a thermally insulating epoxy fiberglass composite. Testing showed that interaction between the inner and the outer helium reservoirs of the new system is significantly lower than the original system.

  6. Superfluid interfaces in liquid He-3: Superconducting cosmic domain walls in the laboratory

    NASA Astrophysics Data System (ADS)

    Salomaa, M. M.

    The interface between superfluid He-3-A and He-3-B, as the most novel surface known to exist in condensed matter physics, was studied. The most important (and most surprising) finding is the discovery of completely new classes of A-A interphasons displaying a fractional quantum jump in the phase psi of the superfluid condensate: for these novel interphasons, the phase difference delta(psi) between the left and the right A-phase vacua, is only pi/2 (or -pi/2 congruence 3pi/2), not pi. These half soliton vacuum interfaces provide the most elementary possible processes of phase slippage in superfluid He-3-A. Symmetry analysis and numerical calculations have revealed that the number of superfluid A-B interfaces is doubled in the presence of an external magnetic field. In particular, the rotating A-B interface is intriguing, since it is theoretically predicted to contain a plenitude of different hedgehogs: Dirac monopoles with fractional charge.

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

    SciTech Connect

    Rodriguez-Gomez, J.R.

    1983-01-01

    An independent calculation of the condensate fraction and the ground state energy of liquid helium is given. The Froehlich ansatz for the second reduced density matrix in conjunction with the ODLORO hypothesis for liquid helium below the critical temperature is used. Froehlich's ansatz is shown to be consistent with numerical calculations of the ground state properties of liquid helium. The ground state energy was -5.10/sup 0/K, close to the experimental value. The condensate fraction turned out to be about 10% which is within the margin of error of recent neutron scattering experiments and agrees with other theoretical calculations.

  8. Apparatus to measure liquid helium boil-off from low-loss superconducting current leads

    SciTech Connect

    Cha, Y.S.; Niemann, R.C.; Hull, J.R.

    1995-06-01

    A low-loss liquid helium dewar was constructed to measure the liquid helium boil-off rate from high-temperature superconducting current leads. The dewar has a measured background heat leakage rate of 12 mW. Equations calculating the heat leakage rate from the measured vapor mass flow rate in liquid helium boil-off experiments are derived. Parameters that affect the experiments, such as density ratio, absolute pressure, and rate of pressure variation, are discussed. This study is important as superconducting current leads may be used in superconducting magnetic energy storage systems.

  9. Design and Use of a Large-Scale Liquid Helium Conversion System

    NASA Technical Reports Server (NTRS)

    Knudsen, P. N.

    1999-01-01

    A large-scale liquid helium (LHe) to high-pressure (HP) gas conversion system has been implemented at the John F. Kennedy Space Center (KSC). Helium is used by the Space Shuttle, Titan, Atlas, and Delta programs for prelaunch processing, during launch count-down, and for postlaunch securing. The first phase of modifications to the Compressor Converter Facility (CCF), operational in April 1998, allowed the facility to accept bulk liquid helium from tanker containers and to off-load the helium at super-critical pressures. The second phase of modifications, planned to be operational by January 2001, will implement a 227-cubic-meter (m(sup 3)) on-site liquid helium storage system. This paper describes the design and operation of the current system and discusses the design and implementation for the second phase system.

  10. Cryogenic design of the liquid helium experiment ``critical dynamics in microgravity``

    SciTech Connect

    Moeur, W.A.; Adriaans, M.J.; Boyd, S.T.; Strayer, D.M.; Duncan, R.V. |

    1995-10-01

    Although many well controlled experiments have been conducted to measure the static properties of systems near criticality, few experiments have explored the transport properties in systems driven far away from equilibrium as a phase transition occurs. The cryogenic design of an experiment to study the dynamic aspect of critical phenomena is reported here. Measurements of the thermal gradient across the superfluid (He II) -- normal fluid (He I) interface in helium under microgravity conditions will be performed as a heat flux holds the system away from equilibrium. New technologies are under development for this experiment, which is in the definition phase for a space shuttle flight.

  11. Design and Test of a Liquid Oxygen / Liquid Methane Thruster with Cold Helium Pressurization Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Melcher, John C.; Morehead, Robert L.; Atwell, Matthew J.; Hurlbert, Eric A.

    2015-01-01

    A liquid oxygen / liquid methane 2,000 lbf thruster was designed and tested in conjuction with a nozzle heat exchanger for cold helium pressurization. Cold helium pressurization systems offer significant spacecraft vehicle dry mass savings since the pressurant tank size can be reduced as the pressurant density is increased. A heat exchanger can be incorporated into the main engine design to provide expansion of the pressurant supply to the propellant tanks. In order to study the systems integration of a cold-helium pressurization system, a 2,000 lbf thruster with a nozzle heat exchanger was designed for integration into the Project Morpheus vehicle at NASA Johnson Space Center. The testing goals were to demonstrate helium loading and initial conditioning to low temperatures, high-pressure/low temperature storage, expansion through the main engine heat exchanger, and propellant tank injection/pressurization. The helium pressurant tank was an existing 19 inch diameter composite-overwrap tank, and the targert conditions were 4500 psi and -250 F, providing a 2:1 density advantage compared to room tempatrue storage. The thruster design uses like-on-like doublets in the injector pattern largely based on Project Morpheus main engine hertiage data, and the combustion chamber was designed for an ablative chamber. The heat exchanger was installed at the ablative nozzle exit plane. Stand-alone engine testing was conducted at NASA Stennis Space Center, including copper heat-sink chambers and highly-instrumented spoolpieces in order to study engine performance, stability, and wall heat flux. A one-dimensional thermal model of the integrated system was completed. System integration into the Project Morpheus vehicle is complete, and systems demonstrations will follow.

  12. Observation of electron spin resonance of negative ions in liquid helium

    NASA Technical Reports Server (NTRS)

    Reichert, J. F.; Dahm, A. J.

    1973-01-01

    Electron spin resonance signals of negative ions in liquid helium were observed. The line width and g-value were measured. Electrons injected into helium by field emission from ferromagnetic tips are shown to be polarized. A new technique for the measurement of electron spin polarization is presented.

  13. Construction of an ultra low temperature cryostat and transverse acoustic spectroscopy in superfluid helium-3 in compressed aerogels

    NASA Astrophysics Data System (ADS)

    Bhupathi, Pradeep

    An ultra low temperature cryostat is designed and implemented in this work to perform experiments at sub-millikelvin temperatures, specifically aimed at understanding the superfluid phases of 3He in various scenarios. The cryostat is a combination of a dilution refrigerator (Oxford Kelvinox 400) with a base temperature of 5.2 mK and a 48 mole copper block as the adiabatic nuclear demagnetization stage with a lowest temperature of ≈ 200 muK. With the various techniques implemented for limiting the ambient heat leak to the cryostat, we were able to stay below 1 mK for longer than 5 weeks. The details of design, construction and performance of the cryostat are presented. We measured high frequency shear acoustic impedance in superfluid 3He in 98% porosity aerogel at pressures of 29 bar and 32 bar in magnetic fields upto 3 kG with the aerogel cylinder compressed along the symmetry axis to generate global anisotropy. With 5% compression, there is an indication of a supercooled A-like to B-like transition in aerogel in a wider temperature width than the A phase in the bulk, while at 10% axial compression, the A-like to B-like transition is absent on cooling down to ≈ 300 muK in zero magnetic field and in magnetic fields up to 3 kG. This behavior is in contrast to that in 3He in uncompressed aerogels, in which the supercooled A-like to B-like transitions have been identified by various experimental techniques. Our result is consistent with theoretical predictions. To characterize the anisotropy in compressed aerogels, optical birefringence is measured in 98% porosity silica aerogel samples subjected to various degrees of uniaxial compression up to 15% strain, with wavelengths between 200 to 800 nm. Uncompressed aerogels exhibit no or a minimal degree of birefringence, indicating the isotropic nature of the material over the length scale of the wavelength. Uniaxial compression of aerogel introduces global anisotropy, which produces birefringence in the material. We

  14. Second sound shock waves and critical velocities in liquid helium 2. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Turner, T. N.

    1979-01-01

    Large amplitude second-sound shock waves were generated and the experimental results compared to the theory of nonlinear second-sound. The structure and thickness of second-sound shock fronts are calculated and compared to experimental data. Theoretically it is shown that at T = 1.88 K, where the nonlinear wave steepening vanishes, the thickness of a very weak shock must diverge. In a region near this temperature, a finite-amplitude shock pulse evolves into an unusual double-shock configuration consisting of a front steepened, temperature raising shock followed by a temperature lowering shock. Double-shocks are experimentally verified. It is experimentally shown that very large second-sound shock waves initiate a breakdown in the superfluidity of helium 2, which is dramatically displayed as a limit to the maximum attainable shock strength. The value of the maximum shock-induced relative velocity represents a significant lower bound to the intrinsic critical velocity of helium 2.

  15. Is solid helium a supersolid?

    SciTech Connect

    Hallock, Robert

    2015-05-15

    Recent experiments suggest that helium-4 atoms can flow through an experimental cell filled with solid helium. But that incompletely understood flow is quite different from the reported superfluid-like motion that so excited physicists a decade ago.

  16. Note: Control of liquid helium supply to cryopanels of Kolkata superconducting cyclotron

    SciTech Connect

    Bhattacharyya, T. K. Pal, G.

    2015-02-15

    The Kolkata superconducting cyclotron utilises liquid helium to cool the main magnet niobium-titanium (NbTi) coil and the cryopanels. Three liquid helium cooled cryopanels, placed inside the dees of the radio-frequency system, maintain the high vacuum in the acceleration region of the superconducting cyclotron. The small cryostat placed inside the cryogenic distribution manifold located at the basement of the superconducting cyclotron building supplies liquid helium in parallel branches to three cold heads, used for cooling their associated cryopanels. The level in the cryostat has to be maintained at an optimum value to ensure uninterrupted flow of liquid helium to these three cold heads. This paper describes the transfer function of the overall system, its tuning parameters, and discusses the actual control of cryostat level by using these parameters.

  17. Successful vitrification of bovine immature oocyte using liquid helium instead of liquid nitrogen as cryogenic liquid.

    PubMed

    Yu, Xue-Li; Xu, Ya-Kun; Wu, Hua; Guo, Xian-Fei; Li, Xiao-Xia; Han, Wen-Xia; Li, Ying-Hua

    2016-04-01

    The objectives of this study were to compare the effectiveness of liquid helium (LHe) and liquid nitrogen (LN2) as cryogenic liquid for vitrification of bovine immature oocytes with open-pulled straw (OPS) system and determine the optimal cryoprotectant concentration of LHe vitrification. Cumulus oocyte complexes were divided into three groups, namely, untreated group (control), LN2 vitrified with OPS group, and LHe vitrified with OPS group. Oocyte survival was assessed by morphology, nuclear maturation, and developmental capability. Results indicated that the rates of normal morphology, maturation, cleavage, and blastocyst (89.3%, 52.8%, 42.7%, and 10.1%, respectively) in the LHe-vitrified group were all higher than those (79.3%, 43.4%, 34.1%, and 4.7%) in the LN2-vitrified group (P < 0.05) although the corresponding rates in both treated groups decreased compared with the control group (100%, 75.0%, 64.9%, and 40.8%; P < 0.05). Normal calves were obtained after the transfer of blastocysts derived from LHe- and LN2-vitrified oocytes. The effects of the different vitrification solutions (EDS30, EDS35, EDS40, EDS45, and EDS50) in LHe vitrification for bovine immature oocytes vitrification were examined. No difference was found in the rates of morphologically normal oocytes among the EDS30 (87.9%), EDS35 (90.1%), EDS40 (89.4%), and EDS45 (87.2%) groups (P > 0.05). The maturation rate of the EDS35 group (65.0%) was higher than those of the EDS30 (51.3%), EDS40 (50.1%), EDS45 (52.1%), and EDS50 groups (36.9%; P < 0.05). No significant differences were observed in the cleavage and blastocyst rates between the EDS35 (49.0% and 12.1%) and EDS40 (41.7% and 10.2%) groups. However, the cleavage and blastocyst rates in the EDS35 group were higher (P < 0.05) than those of the EDS30 (36.2% and 6.8%), EDS45 (35.9% and 5.8%), and EDS50 (16.6% and 2.2%) groups. In conclusion, LHe can be used as a cryogenic liquid for vitrification of bovine immature oocytes, and it is more

  18. Electron Spin Resonance of Positive Ions in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Herold, George Sutton

    ESR from the positive ion in liquid helium were recorded as a function of temperature from 1.3 K to 7.5 K, and as a function of isotopic ^3He concentration from 4% ^3He to 96% ^3He. The ESR signals of the positive ion are g-shifted up-field 0.443 +/- 0.002 Gauss from the free electron g-value of the negative ion. The g-shift was independent of all externally controllable parameters. The relaxation times T_1 and T_2 were extracted from the ESR data. The relaxation times were found to change exponentially with the reciprocal of the temperature. Changes in the relaxation times as a function of temperature and ^3He concentration are interpreted in terms of Atkins' "snowball" model for the positive ion. A theoretical calculation of the local ^3He concentration as a function of the distance from the ion center, temperature, and bulk ^3He concentration is carried out. There is good agreement between the measured values of T_2 and those predicted from the theoretical calculation. We interpret the measured T_2's as resulting from the presence of ^3He atoms in the solid "snowball". Relatively short T_1's are measured for the positive ion. We interpret the measured T_1 's as resulting from the motion of ^3 He atoms on the "surface" of the positive ion "snowball". The motion of ^3He atoms in the proposed "surface" region of the "snowball" is different from the motion of the atoms in the liquid or solid state. ESR signals from the negative ion at external pressures very near the freezing pressure have been reinterpreted as resulting from the formation of a similar "surface" region around the electron "bubble" at high pressures.

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

    SciTech Connect

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

    1992-06-30

    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.

  20. Observation of dynamic atom-atom correlation in liquid helium in real space

    NASA Astrophysics Data System (ADS)

    Dmowski, W.; Diallo, S. O.; Lokshin, K.; Ehlers, G.; Ferré, G.; Boronat, J.; Egami, T.

    2017-05-01

    Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.

  1. Observation of dynamic atom-atom correlation in liquid helium in real space

    DOE PAGES

    Dmowski, W.; Diallo, S. O.; Lokshin, K.; ...

    2017-05-04

    Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom–atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose–Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDFmore » peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom–atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.« less

  2. Observation of dynamic atom-atom correlation in liquid helium in real space.

    PubMed

    Dmowski, W; Diallo, S O; Lokshin, K; Ehlers, G; Ferré, G; Boronat, J; Egami, T

    2017-05-04

    Liquid (4)He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that (4)He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.

  3. Observation of dynamic atom-atom correlation in liquid helium in real space

    PubMed Central

    Dmowski, W.; Diallo, S. O.; Lokshin, K.; Ehlers, G.; Ferré, G.; Boronat, J.; Egami, T.

    2017-01-01

    Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom–atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose–Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom–atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon. PMID:28469252

  4. Cold Helium Pressurization for Liquid Oxygen/Liquid Methane Propulsion Systems: Fully-Integrated Hot-Fire Test Results

    NASA Technical Reports Server (NTRS)

    Morehead, R. L.; Atwell, M. J.; Melcher, J. C.; Hurlbert, E. A.

    2016-01-01

    Hot-fire test demonstrations were successfully conducted using a cold helium pressurization system fully integrated into a liquid oxygen (LOX) / liquid methane (LCH4) propulsion system (Figure 1). Cold helium pressurant storage at near liquid nitrogen (LN2) temperatures (-275 F and colder) and used as a heated tank pressurant provides a substantial density advantage compared to ambient temperature storage. The increased storage density reduces helium pressurant tank size and mass, creating payload increases of 35% for small lunar-lander sized applications. This degree of mass reduction also enables pressure-fed propulsion systems for human-rated Mars ascent vehicle designs. Hot-fire test results from the highly-instrumented test bed will be used to demonstrate system performance and validate integrated models of the helium and propulsion systems. A pressurization performance metric will also be developed as a means to compare different active pressurization schemes.

  5. Theoretical interpretation of the vacuum ultraviolet reflectance of liquid helium and of the absorption spectra of helium microbubbles in aluminum

    NASA Astrophysics Data System (ADS)

    Lucas, A. A.; Vigneron, J. P.; Donnelly, S. E.; Rife, J. C.

    1983-09-01

    The position and width of the helium resonance line 11S0-->21P1 are calculated for a high-density helium fluid. The theory aims at understanding the reflectivity data of Surko et al. for the low-temperature liquid-vapor interface and the absorption data of Rife et al. for room-temperature, high-pressure helium bubbles in aluminum. The theoretical ingredients of the model are (i) the long-range dipole interaction of an excited 2P atom with the rest of the fluid and with the metal substrate; (ii) the short-range Pauli pseudorepulsion arising from orthogonalization of the 2p-electron wave function with the 1s ground-state orbital of neighboring atoms; (iii) a statistical treatment of the high-density fluid based either on the experimentally measured radial pair distribution function of low-T liquid He, or on the Percus-Yevick distribution function of hard spheres and the theoretical equation of state of Young et al. for the He fluid in the bubbles; (iv) the standard static line-broadening theory to calculate the effect of Pauli repulsion on the line shapes. The theory provides a reasonably accurate understanding of the observed spectra in both the liquid and high-density gas, and can serve as a sound basis for interpretation of vacuum ultraviolet spectra in other gas-metal combinations.

  6. Developmental competence and gene expression of immature oocytes following liquid helium vitrification in bovine.

    PubMed

    Chen, Jun-Yi; Li, Xiao-Xia; Xu, Ya-Kun; Wu, Hua; Zheng, Jun-Jun; Yu, Xue-Li

    2014-12-01

    The objective of this study was to develop an effective ultra-rapid vitrification method and evaluate its effect on maturation, developmental competence and development-related gene expression in bovine immature oocytes. Bovine cumulus oocyte complexes were randomly allocated into three groups: (1) controls, (2) liquid nitrogen vitrification, and (3) liquid helium vitrification. Oocytes were vitrified and then warmed, the percentage of morphologically normal oocytes in liquid helium group (89.0%) was significantly higher (P<0.05) than that of the liquid nitrogen group (81.1%). When the vitrified-thawed oocytes were matured in vitro for 24h, the maturation rate in liquid helium group (50.6%) was higher (P<0.05) than liquid nitrogen group (42.6%). Oocytes of liquid helium vitrification had higher cleavage and blastocyst rates (41.1% and 10.0%) than that of liquid nitrogen vitrification (33.0% and 4.5%; P<0.05) after in vitro fertilization. Moreover, the expression of GDF9 (growth/differentiation factor-9), BAX (apoptosis factor) and ZAR1 (zygote arrest 1) was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) when the vitrified-thawed oocytes were matured 24h. The expression of these genes was altered after vitrification. Expression of GDF9 and BAX in the liquid helium vitrification group was not significantly different from that of the control, however there were significant differences between the liquid nitrogen vitrification group and control. In conclusion, it was feasible to use liquid helium for vitrifying bovine immature oocytes. There existed an association between the compromised developmental competence and the altered expression levels of these genes for the vitrified oocytes. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Probing quantum and classical turbulence analogy in von Kármán liquid helium, nitrogen, and water experiments

    NASA Astrophysics Data System (ADS)

    Saint-Michel, B.; Herbert, E.; Salort, J.; Baudet, C.; Bon Mardion, M.; Bonnay, P.; Bourgoin, M.; Castaing, B.; Chevillard, L.; Daviaud, F.; Diribarne, P.; Dubrulle, B.; Gagne, Y.; Gibert, M.; Girard, A.; Hébral, B.; Lehner, Th.; Rousset, B.

    2014-12-01

    We report measurements of the dissipation in the Superfluid helium high REynold number von Kármán flow experiment for different forcing conditions. Statistically steady flows are reached; they display a hysteretic behavior similar to what has been observed in a 1:4 scale water experiment. Our macroscopical measurements indicate no noticeable difference between classical and superfluid flows, thereby providing evidence of the same dissipation scaling laws in the two phases. A detailed study of the evolution of the hysteresis cycle with the Reynolds number supports the idea that the stability of the steady states of classical turbulence in this closed flow is partly governed by the dissipative scales. It also supports the idea that the normal and the superfluid components at these temperatures (1.6 K) are locked down to the dissipative length scale.

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

    SciTech Connect

    Ju, Y. L.; Dodd, J. R.; Willis, W. J.

    2006-04-27

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

  9. Measurements of the Critical Casimir Effect and Superfluid Density in Saturated Helium-4 Films near T(lambda)

    NASA Astrophysics Data System (ADS)

    Abraham, John Bishoy Sam

    Saturated thick films of 4Helium adsorbed on a copper substrate are studied experimentally. The film thickness is measured with an ultra-sensitive capacitance bridge capable of resolving sub-Angstrom changes in film thickness. Through the use of this capacitance bridge, the critical Casimir effect in the films is studied in the vicinity of the lambda transition. Additionally, the copper substrate assembly is used to generate and detect third sound in the film. Measurements are made of the third sound speed and attenuation in thick film from 1.6 K to the Kosterlitz-Thouless transition in the films. The position of the Kosterlitz-Thouless transition relative to the critical Casimir effect in the films is identifieded. It is discovered that the Kosterlitz-Thouless transition occurs at the beginning of the dip in film thickness due to the critical Casimir effect. When the temperature of the system is swept extremely slowly across the lambda transition, a step in film thickness is observed. This step is possibly a non-universal critical Casimir effect. A model of thermal second sound excitations is developed to describe this new observation.

  10. Squeezing superfluid from a stone: Coupling superfluidity and elasticity in a supersolid

    NASA Astrophysics Data System (ADS)

    Dorsey, Alan

    2007-03-01

    Superfluidity---the ability of liquid ^4He, when cooled below 2.176 K, to flow without resistance through narrow pores---has long served as a paradigm for the phenomenon of ``off-diagonal long-range order'' (ODLRO) in quantum liquids and superconductors. Supersolidity---the coexistence of ODLRO with the crystalline order of a solid---was proposed theoretically over 35 years ago as an even more exotic phase of solid ^4He, but it has eluded detection. Recently, Kim and Chan [1,2] have reported an anomalous decoupling transition of solid ^4He in a torsional oscillator measurement, and interpret their results as evidence for non-classical rotational inertia and a possible supersolid phase of ^4He. In this talk I will give brief historical review of the theory of and experimental searches for supersolidity. I will then discuss a phenomenological Landau theory of the normal solid to supersolid (NS-SS) transition in which superfluidity is coupled to the elasticity of the crystalline ^4He lattice, and underscore the implications of this theory for experimental searches for supersolidity [3]. I will also discuss a hydrodynamic model for supersolids, in which the additional broken gauge symmetry in the supersolid phase produces a collective mode that is analogous to second sound in superfluid helium. [1] E. Kim and M. H. W. Chan, Nature (London) 427, 225 (2004). [2] E. Kim and M. H. W. Chan, Science 305, 1941 (2004). [3] A. T. Dorsey, P. M. Goldbart, and J. Toner, ``Squeezing superfluid from a stone: Coupling superfluidity and elasticity in a supersolid,'' Phys. Rev. Lett. 96, 055301 (2006).

  11. Berkeley Experiments on Superfluid Macroscopic Quantum Effects

    SciTech Connect

    Packard, Richard

    2006-09-07

    This paper provides a brief history of the evolution of the Berkeley experiments on macroscopic quantum effects in superfluid helium. The narrative follows the evolution of the experiments proceeding from the detection of single vortex lines to vortex photography to quantized circulation in 3He to Josephson effects and superfluid gyroscopes in both 4He and 3He.

  12. Cryogenic Design and Operation of Liquid Helium in Electron Bubble Chamber

    SciTech Connect

    Ju, Y. L.; Dodd, J. R.; Willis, W. J.; Jia, L. X.

    2006-04-27

    We are developing a new cryogenic neutrino detector: electron bubble chamber, using liquid helium as the detecting medium, for the detection of low-energy neutrinos (<1 MeV), from the Sun. The program focuses in particular on the interactions of neutrinos scattering off atomic electrons in the detecting medium of liquid helium, resulting in recoil electrons which can be measured. We designed and constructed a small test chamber with 1.5L active volume to start the detector R and D, and performed experimental proofs of the operation principle. The test chamber is a stainless steel cylinder equipped with five optical windows and ten high voltage cables. To shield the liquid helium chamber against the external heat loads, the chamber is made of double-walled jacket cooled by a pumped helium bath and is built into a LN2/LHe cryostat, equipped with 80 K and 4 K radiation shields. A needle valve for vapor helium cooling was used to provide a 1.7{approx}4.5 K low temperature environments. The paper gives an introduction to the liquid helium solar neutrino detector, presents the cryogenic design and operation of the small test chamber.

  13. Design of a horizonal liquid helium cryostat for refrigerating a flying superconducting magnet in a wind tunnel

    NASA Technical Reports Server (NTRS)

    Wu, Y. Y.

    1982-01-01

    The design of a horizontal liquid helium cryostat for refrigerating a flying superconducting magnet in a wind tunnel is presented. The basic principles of magnetic suspension theory are described and theoretical calculations of the superconducting magnet are provided. The experimental results of the boil-off of liquid nitrogen and liquid helium in the cryostat are reported.

  14. Compact bath cryostat filled with liquid helium inside an ordinary storage Dewar

    NASA Astrophysics Data System (ADS)

    Klimov, A. E.

    2001-09-01

    An economical bath cryostat for optical and galvano-magnetic measurements is described. The small overall diameter of the cryostat allows filling with liquid helium directly upon immersion into an ordinary storage Dewar vessel. As a result, it needs no more than 0.2 l of liquid helium for a single cycle of low-temperature measurements outside the storage Dewar lasting 1.5-4 h. Simplicity and low cost are other advantages of the cryostat. The basic ideas used in this device are the mobility of a helium can relative to the external body of the cryostat and the essential increase of the helium boiling point if pressure increases up to 0.5-1.5 atm over atmospheric pressure.

  15. Liquid helium-free cryostat and hermetically sealed cryogenic microwave cavity for hyperfine spectroscopy of antiprotonic helium

    PubMed Central

    Massiczek, O.; Friedreich, S.; Juhász, B.; Widmann, E.; Zmeskal, J.

    2011-01-01

    The design and properties of a new cryogenic set-up for laser–microwave–laser hyperfine structure spectroscopy of antiprotonic helium – an experiment performed at the CERN-Antiproton Decelerator (AD), Geneva, Switzerland – are described. Similar experiments for 4He have been performed at the AD for several years. Due to the usage of a liquid helium operated cryostat and therefore necessary refilling of coolants, a loss of up to 10% beamtime occurred. The decision was made to change the cooling system to a closed-circuit cryocooler. New hermetically sealed target cells with minimised 3He gas volume and different dimensions of the microwave resonator for measuring the 3He transitions were needed. A new set-up has been designed and tested at Stefan Meyer Institute in Vienna before being used for the 2009 and 2010 beamtimes at the AD. PMID:22267883

  16. Liquid helium-free cryostat and hermetically sealed cryogenic microwave cavity for hyperfine spectroscopy of antiprotonic helium.

    PubMed

    Massiczek, O; Friedreich, S; Juhász, B; Widmann, E; Zmeskal, J

    2011-12-11

    The design and properties of a new cryogenic set-up for laser-microwave-laser hyperfine structure spectroscopy of antiprotonic helium - an experiment performed at the CERN-Antiproton Decelerator (AD), Geneva, Switzerland - are described. Similar experiments for (4)He have been performed at the AD for several years. Due to the usage of a liquid helium operated cryostat and therefore necessary refilling of coolants, a loss of up to 10% beamtime occurred. The decision was made to change the cooling system to a closed-circuit cryocooler. New hermetically sealed target cells with minimised (3)He gas volume and different dimensions of the microwave resonator for measuring the (3)He transitions were needed. A new set-up has been designed and tested at Stefan Meyer Institute in Vienna before being used for the 2009 and 2010 beamtimes at the AD.

  17. Use of FLUORINE-19 NMR Thermometry in the Investigation of Magnetic Textures in Superfluid HELIUM-3A

    NASA Astrophysics Data System (ADS)

    Mossavati, Ruzbeh

    Available from UMI in association with The British Library. Requires signed TDF. A ^{19}F NMR thermometer for measuring temperatures below 20 mK has been designed, developed and tested in a nuclear demagnetisation cryostat. It was calibrated against the phase diagram of liquid ^3He at 29.34 bar using the second order transition at T_{ rm c} and the ^3He -B to ^3He-A transition temperature as calibration points, and found to be consistent with Curie's law. An attempt was also made to experimentally determine the textural phase diagram of ^3He -A using a torsional oscillator with the nominal slab spacing of 25mum. We did not observe any nonuniform textures which can be explained by the fact that the experimental data indicate an actual spacing of about 15mum. An alternative method for obtaining the required cell spacing is suggested which should prove more reliable.

  18. Operating experience using venturi flow meters at liquid helium temperature

    SciTech Connect

    Wu, K.C.

    1992-06-01

    Experiences using commercial venturi to measure single phase helium flow near 4 K (degree Kelvin) for cooling superconducting magnets have been presented. The mass flow rate was calculated from the differential pressure and the helium density evaluated from measured pressure and temperature. The venturi flow meter, with a full range of 290 g/s (0.29 Kg/s) at design conditions, has been found to be reliable and accurate. The flow measurements have been used, with great success, for evaluating the performance of a cold centrifugal compressor, the thermal acoustic heat load of a cryogenic system and the cooling of a superconducting magnet after quench.

  19. Operating experience using venturi flow meters at liquid helium temperature

    SciTech Connect

    Wu, K.C.

    1992-01-01

    Experiences using commercial venturi to measure single phase helium flow near 4 K (degree Kelvin) for cooling superconducting magnets have been presented. The mass flow rate was calculated from the differential pressure and the helium density evaluated from measured pressure and temperature. The venturi flow meter, with a full range of 290 g/s (0.29 Kg/s) at design conditions, has been found to be reliable and accurate. The flow measurements have been used, with great success, for evaluating the performance of a cold centrifugal compressor, the thermal acoustic heat load of a cryogenic system and the cooling of a superconducting magnet after quench.

  20. Advantages of cryopumping with liquid hydrogen instead of helium refrigerators

    NASA Technical Reports Server (NTRS)

    Anderson, J. W.; Tueller, J. E.

    1972-01-01

    Open loop hydrogen vaporizers and helium refrigerators are compared for operational complexity, installation and operating cost, and safety requirements. Data from two vacuum chambers using helium refrigerators are used to provide comparative data. In general, the use of hydrogen is attractive in the larger systems, even when extra safety precautions are taken. Emotional resistance to the use of hydrogen because of safety requirements is considered great. However, the experience gained in the handling of large quantities of cryogenics, particularly hydrogen and liquefied natural gases, should be considered in the design of open loop hydrogen cooling systems.

  1. Hydrodynamic boundary condition for superfluid flow

    SciTech Connect

    Pomeau, Yves; Roberts, David C.

    2008-04-01

    We discuss the hydrodynamic boundary condition for a superfluid moving tangentially to a rough surface. Specifically, we argue that the scattering of quantum fluctuations off surface roughness affects the nature of the boundary condition, and that this has important consequences including a theorized critical speed and the presence of normal fluid at any nonzero speed, even if the boundary is held at zero temperature (i.e., a moving superfluid flow creates a sustained temperature difference between the superfluid and the boundary). This hydrodynamic boundary condition is relevant not only for superfluid helium experiments but also for experiments with trapped dilute Bose-Einstein condensates, in particular, those involving atomic waveguides near surfaces.

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

    SciTech Connect

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

    1992-06-30

    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.

  3. Optomechanics with superfluid He4 thin films

    NASA Astrophysics Data System (ADS)

    Baker, Christopher; Harris, Glen; McAuslan, David; Sachkou, Yauhen; He, Xin; Sheridan, Eoin; Bowen, Warwick

    Cavity optomechanics focuses on the interaction between confined light and a mechanical degree of freedom. Vibrational modes of superfluid helium-4 have recently been identified as an attractive mechanical element for cavity optomechanics, thanks to their ultra-low dissipation arising from superfluid's viscosity free flow. Here we propose and demonstrate an approach to superfluid optomechanics based on femtogram thin films of superfluid helium condensed on the surface of a microscale microtoroid optical whispering gallery mode resonator. Excitations within the film, known as third sound, manifest as surface waves with a restoring force provided by the van der Waals interaction. We experimentally probe the thermodynamics of these superfluid excitations in real-time, and demonstrate both laser cooling and amplification of the thermal motion. In addition, we propose and demonstrate an entirely new approach to optical forcing based on the atomic recoil of superfluid helium-4. This technique utilizes the thermomechanical effect of superfluids, whereby frictionless fluid flow is generated in response to a local heat source. Using this technique, we achieve superfluid forces on a microtoroid mechanical mode an order of magnitude greater than the equivalent radiation pressure force.

  4. Photogalvanic current in electron gas over a liquid helium surface

    NASA Astrophysics Data System (ADS)

    Entin, M. V.; Magarill, L. I.

    2014-02-01

    We study the stationary surface photocurrent in 2D electron gas near the helium surface. Electron gas is assumed to be attracted to the helium surface due to the image attracting force and an external stationary electric field. The alternating electric field has both vertical and in-plane components. The photogalvanic effect originates from the periodic transitions of electrons between quantum subbands in the vertical direction caused by a normal component of the alternating electric field accompanied by synchronous in-plane acceleration/deceleration due to the electric field in-plane component. The effect needs vertical asymmetry of the system. The problem is considered taking into account a friction caused by the electron-ripplon interaction. The photocurrent resonantly depends on the field frequency. The resonance occurs at field frequencies close to the distance between well subbands. The resonance is symmetric or antisymmetric depending on the kind (linear or circular) of polarization.

  5. Cold Helium Pressurization for Liquid Oxygen / Liquid Methane Propulsion Systems: Fully-Integrated Initial Hot-Fire Test Results

    NASA Technical Reports Server (NTRS)

    Morehead, R. L.; Atwell, M. J.; Melcher, J. C.; Hurlbert, E. A.

    2016-01-01

    A prototype cold helium active pressurization system was incorporated into an existing liquid oxygen (LOX) / liquid methane (LCH4) prototype planetary lander and hot-fire tested to collect vehicle-level performance data. Results from this hot-fire test series were used to validate integrated models of the vehicle helium and propulsion systems and demonstrate system effectiveness for a throttling lander. Pressurization systems vary greatly in complexity and efficiency between vehicles, so a pressurization performance metric was also developed as a means to compare different active pressurization schemes. This implementation of an active repress system is an initial sizing draft. Refined implementations will be tested in the future, improving the general knowledge base for a cryogenic lander-based cold helium system.

  6. Helium tube separates nitrogen gas from liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.

    1964-01-01

    To prevent a boiloff problem, liquid nitrogen flowing from a storage tank to a container, is separated into liquid and gaseous components. This is accomplished by centrifugal and venting action, using a section of perforated helical aluminum tubing.

  7. Investigating Superfluid ^4He Using Commercially Available Quartz Tuning Forks

    NASA Astrophysics Data System (ADS)

    Wiman, Joshua; Deserio, Robert; Sullivan, Neil; Lee, Yoonseok

    2010-03-01

    Mechanical oscillators such as vibrating wire oscillators, torsional oscillators, and acoustic transducers have been widely used to measure the properties of cryogenic liquids. Commercial quartz tuning forks, which can be found in almost every electronic device, have shown promise as viscometers and thermometers for low temperature experiments. These devices are inexpensive, easy to install, and insensitive to magnetic fields. Before a fork can be used, it must be calibrated against a hydrodynamic model. We measured changes in the frequency and width of the fork's resonance response in superfluid ^4He down to 1.5 K. Analysis of the tuning fork's response as a function of temperature shows that its behavior is well-described by the hydrodynamic model for superfluid helium. We will also discuss our future plans.

  8. A Superfluid Clock

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin

    2004-01-01

    The performance of clocks is limited by the characteristics of the underlying oscillator. Both the quality factor of the oscillator and the signal-to-noise ratio for the resonator state measurement are important. A superfluid helium Helmholtz resonator operating at approx.100mK temperatures has the potential of maintaining frequency stability of 5x10(exp -15)/t(exp 1/2) on the time scale of a few months. The high dynamic range of lossless SQUID position displacement measurement, and low losses associated with the superfluid flow, combined with high mechanical stability of cryogenic assemblies, contribute to the projected stability. Low overall mass of the assembly allows for multiple stages of vibration isolation.

  9. 147. EAST END OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN FUEL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    147. EAST END OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN FUEL CONTROL ROOM (215), LSB (BLDG. 751), WITH ASSOCIATED PIPING AND VALVES - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  10. 145. VIEW OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN FUEL CONTROL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    145. VIEW OF LIQUID NITROGEN/HELIUM HEAT EXCHANGER IN FUEL CONTROL ROOM (215), LSB (BLDG. 751), FROM FUEL APRON WITH BAY DOOR OPEN - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA

  11. Characterization and Modeling of Superconducting Josephson Junction Arrays at Low Voltage and Liquid Helium Temperatures

    DTIC Science & Technology

    2016-09-01

    technical report demonstrates the capabilities to measure Niobium-based Josephson junction arrays at liquid helium temperatures at less than 50 mV. We find...2 3. Measurements of the array in the resistive state with temperature greater than the... Measurements of the array in the cryogenic conditions near the critical temperature (i.e., 7 to 8

  12. Low frequency anomalies of the effective mass of charged clusters in liquid helium

    NASA Astrophysics Data System (ADS)

    Shikin, V.

    2013-10-01

    The dynamic behavior of charged clusters in liquid helium is discussed in detail. The matter is their added mass which has ideal, Msass, and normal, Mnass, components. The normal component has a number of interesting features of viscous origin. Some of them were found in recent experiments.

  13. Dynamics of liquid helium boil-off experiments with a step change in pressure

    NASA Astrophysics Data System (ADS)

    Cha, Y. S.; Niemann, R. C.; Hull, J. R.

    The results of dynamic analysis of the effect of pressure variations during helium boil-off experiments are presented. A general solution of the diffusion equation with a time-dependent boundary condition is employed to describe the dynamic response of the liquid helium system under variable pressure conditions, and a solution is obtained for the special case when the system is subjected to a step change in pressure. The calculated temperature response of the liquid indicates that most of the experiments were not likely to have reached equilibrium as a result of the low thermal diffusivity of liquid helium. The initial rate of evaporation or condensation is large, and the rate decreases sharply with time. A method is proposed to account for the transient effect that is observed during calculation of the heat loss rate from a helium boil-off experiment. By assuming that there is no mixing at all, the present analysis provides an estimate of the upper (condensation) or lower (evaporation) bound of the heat loss rate as a result of a pressure increase or decrease in the system. A previously reported equilibrium analysis is expected to apply to situations where complete mixing occurred in the bulk liquid and provides the opposite limits.

  14. Liquid helium cryopump and reliable opening device for a balloon-borne mass spectrometer.

    PubMed

    Ingels, J; Arijs, E; Nevejans, D; Forth, H J; Schäfer, G

    1978-06-01

    The design, technical characteristics, and test and flight results of a liquid helium cryopump and an opening device operating on board a balloon-borne mass spectrometer combining a cryopump and a quadrupole mass filter are reported. The gas inlet of this mass spectrometer is opened through a simple and reliable remote-controlled system, which is also described.

  15. Modeling the pressure increase in liquid helium cryostats after failure of the insulating vacuum

    SciTech Connect

    Heidt, C.; Grohmann, S.; Süßer, M.

    2014-01-29

    The pressure relief system of liquid helium cryostats requires a careful design, due to helium's low enthalpy of vaporization and due to the low operating temperature. Hazard analyses often involve the failure of the insulating vacuum in the worst-case scenario. The venting of the insulating vacuum and the implications for the pressure increase in the helium vessel, however, have not yet been fully analyzed. Therefore, the dimensioning of safety devices often requires experience and reference to very few experimental data. In order to provide a better foundation for the design of cryogenic pressure relief systems, this paper presents an analytic approach for the strongly dynamic process induced by the loss of insulating vacuum. The model is based on theoretical considerations and on differential equation modeling. It contains only few simplifying assumptions, which will be further investigated in future experiments. The numerical solutions of example calculations are presented with regard to the heat flux into the helium vessel, the helium pressure increase and the helium flow rate through the pressure relief device. Implications concerning two-phase flow and the influence of kinetic energy are discussed.

  16. Cantilever anemometer based on a superconducting micro-resonator: application to superfluid turbulence.

    PubMed

    Salort, J; Monfardini, A; Roche, P-E

    2012-12-01

    We present a new type of cryogenic local velocity probe that operates in liquid helium (1 K < T < 4.2 K) and achieves a spatial resolution of ≈ 0.1 mm. The operating principle is based on the deflection of a micro-machined silicon cantilever which reflects the local fluid velocity. Deflection is probed using a superconducting niobium micro-resonator sputtered on the sensor and used as a strain gauge. We present the working principle and the design of the probe, as well as calibration measurements and velocity spectra obtained in a turbulent helium flow above and below the superfluid transition.

  17. Paramagnetic Attraction of Impurity-Helium Solids

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  18. Blow-down analysis of helium from a cryogenic dewar

    NASA Technical Reports Server (NTRS)

    Khan, H. J.; Zhang, Q. Q.; Rhee, M.; Figueroa, O.

    1992-01-01

    NASA is currently developing Space Shuttle-based refilling of helium using superfluid helium on-orbit transfer (SHOOT). All the critical components of SHOOT need to be developed through ground-based tests. The helium dewar is one of these components. The Dewar consists of a vacuum vessel enclosing a superinsulated tank. The space between the vacuum vessel and the liquid tank is considered a common vacuum space. In the event that the vacuum is lost, the heat transfers to the dewar and the pressure inside the dewar increases rapidly, resulting in rupture of the dewar due to excessive pressure. Therefore, an emergency vent line is required for release of helium to prevent the dewar from rupturing. The study describes a numerical model for blow-down analysis in an emergency. This qualifies the design of the emergency vent line to be adequate for the assumed heat loads to the helium dewar.

  19. Blow-down analysis of helium from a cryogenic dewar

    NASA Astrophysics Data System (ADS)

    Khan, H. J.; Zhang, Q. Q.; Rhee, M.; Figueroa, O.

    NASA is currently developing Space Shuttle-based refilling of helium using superfluid helium on-orbit transfer (SHOOT). All the critical components of SHOOT need to be developed through ground-based tests. The helium dewar is one of these components. The Dewar consists of a vacuum vessel enclosing a superinsulated tank. The space between the vacuum vessel and the liquid tank is considered a common vacuum space. In the event that the vacuum is lost, the heat transfers to the dewar and the pressure inside the dewar increases rapidly, resulting in rupture of the dewar due to excessive pressure. Therefore, an emergency vent line is required for release of helium to prevent the dewar from rupturing. The study describes a numerical model for blow-down analysis in an emergency. This qualifies the design of the emergency vent line to be adequate for the assumed heat loads to the helium dewar.

  20. Blow-down analysis of helium from a cryogenic dewar

    NASA Technical Reports Server (NTRS)

    Khan, H. J.; Zhang, Q. Q.; Rhee, M.; Figueroa, O.

    1992-01-01

    NASA is currently developing Space Shuttle-based refilling of helium using superfluid helium on-orbit transfer (SHOOT). All the critical components of SHOOT need to be developed through ground-based tests. The helium dewar is one of these components. The Dewar consists of a vacuum vessel enclosing a superinsulated tank. The space between the vacuum vessel and the liquid tank is considered a common vacuum space. In the event that the vacuum is lost, the heat transfers to the dewar and the pressure inside the dewar increases rapidly, resulting in rupture of the dewar due to excessive pressure. Therefore, an emergency vent line is required for release of helium to prevent the dewar from rupturing. The study describes a numerical model for blow-down analysis in an emergency. This qualifies the design of the emergency vent line to be adequate for the assumed heat loads to the helium dewar.

  1. Optical investigation of impurities in superfluid {sup 4}He

    SciTech Connect

    Tabbert, B.; Guenther, H.; Putlitz, G. zu

    1997-12-01

    This review is devoted to optical studies of foreign particles in superfluid {sup 4}He. Starting with single excess electrons, helium ions and metastable helium atoms, various methods for the implantation of these species into the quantum fluid are summarized. Continuing with neutral and charged atoms, molecules, and clusters implantation techniques like laser ablation, gas discharges, or atomic beams are discussed. The implanted particles act as micro-probes for the liquid helium and form complex defect structures-known as bubbles and snowballs. The behavior of the impurities, their defect structures in the liquid, and their optical spectra are discussed. The treatment is mainly focused on the manifold of atoms and ions from nearly all groups of the periodic table of elements which became available for optical experiments in liquid {sup 4}He in the recent ten years. It includes theoretical description of the impurities by the standard bubble model (SBM). Extensions and limitations of the SBM are discussed regarding non-radiative transitions and the dynamic Jahn-Teller effect. The review is concluded by a discussion of applications of `the presented experimental methods such as spin physics and motion studies in liquid helium.

  2. Calibrating the Helium Pressurization System for the Space Shuttle Liquid-Hydrogen Tank

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Analysis of the results from the STS-114 tanking tests and subsequent launch called into question existing thermal and mass models of helium pressurization of the liquid hydrogen tank. This hydrogen tank, which makes up the bottom two-thirds of the External Tank, is pressurized prior to launch to avoid cavitation in the Shuttle Main Engine pumps. At about 2 minutes prior to launch, the main vent valve is closed, and pressurized helium flows into the tank ullage space to achieve set point pressure. As the helium gas cools, its pressure drops, calling for additional helium. Subsequent helium flows are provided in short, timed pulses. The number of pulses is taken as a rough leak indicator. An analysis of thermal models by Marshall Space Flight Center showed considerable uncertainty in the pressure-versus-time behavior of the helium ullage space and the ability to predict the number of pulses normally expected. Kennedy Space Center proposed to calibrate the dime-sized orifice, which together with valves, controls the helium flow quantity (Figure 1). Pressure and temperature sensors were installed to provide upstream and downstream measurements necessary to compute flow rate based on the orifice discharge coefficient. An assessment of flow testing with helium indicated an extremely costly use of this critical resource. In order to reduce costs, we proposed removing the orifices from each Mobile Launcher Platform (MLP) and asking Colorado Engineering Experiment Station Inc. (CEESI) to calibrate the flow. CEESI has a high-pressure air flow system with traceable flow meters capable of handling the large flow rates. However, literature research indicated that square-edged orifices of small diameters often exhibit significant hysteresis and nonrepeatability in the vicinity of choked or sonic flow. Fortunately, the MLP orifices behaved relatively well in testing (Figure 2). Using curve fitting of the air-flow data, in conjunction with ASME orifice modeling equations, a

  3. A transition-edge-sensor-based instrument for the measurement of individual He2* excimers in a superfluid 4He bath at 100 mK

    NASA Astrophysics Data System (ADS)

    Carter, Faustin Wirkus

    This dissertation is an account of the first calorimetric detection of individual He*2 excimers within a bath of superfluid 4He. When superfluid helium is subject to ionizing radiation, diatomic He molecules are created in both the singlet and triplet states. The singlet He molecules decay within nanoseconds, but due to a forbidden spin-flip the triplet molecules have a relatively long lifetime of 13 seconds in superfluid He. When He* 2 molecules decay, they emit a ~15 eV photon. Nearly all matter is opaque to these vacuum-UV photons, although they do propagate through liquid helium. The triplet state excimers propagate ballistically through the superfluid until they quench upon a surface; this process deposits a large amount of energy into the surface. The prospect of detecting both excimer states is the motivation for building a detector immersed directly in the superfluid bath. The detector used in this work is a single superconducting titanium transition edge sensor (TES). The TES is mounted inside a hermetically sealed chamber at the baseplate of a dilution refrigerator. The chamber contains superfluid helium at 100 mK. Excimers are created during the relaxation of high-energy electrons, which are introduced into the superfluid bath either in situ via a sharp tungsten tip held above the field-emission voltage, or by using an external gamma-ray source to ionize He atoms. These excimers either propagate through the LHe bath and quench on a surface, or decay and emit vacuum-ultraviolet photons that can be collected by the detector. This dissertation discusses the design, construction, and calibration of the TES-based excimer detecting instrument. It also presents the first spectra resulting from the direct detection of individual singlet and triplet helium excimers.

  4. Fermion Superfluidity

    NASA Technical Reports Server (NTRS)

    Strecker, Kevin; Truscott, Andrew; Partridge, Guthrie; Chen, Ying-Cheng

    2003-01-01

    Dual evaporation gives 50 million fermions at T = 0.1 T(sub F). Demonstrated suppression of interactions by coherent superposition - applicable to atomic clocks. Looking for evidence of Cooper pairing and superfluidity.

  5. Study of helium transfer technology for STICCR: Fluid management

    NASA Technical Reports Server (NTRS)

    Frank, D. J.; Yuan, S. W. K.; Grove, R. K.; Lheureux, J. M.

    1987-01-01

    The Space Infrared Telescope Facility (SIRTF) is a long life cryogenically cooled space based telescope for infrared astronomy from 2 to 700 microns currently under study and planned for launch in the mid 90's. SIRTF will operate as a multi-user facility, initially carrying 3 instruments at the focal plane. It will be cooled to below 2 K by superfluid liquid helium to achieve radiometric sensitivity limited only by the statistical fluctuations in the natural infrared background radiation over most of its spectral range. The lifetime of the mission will be limited by the lifetime of the liquid helium supply, and is currently baselined to be 2 years. Candidates are reviewed for a liquid management device to be used in the resupply of liquid helium, and for the selection of an appropriate candidate.

  6. Studying electrons on curved surfaces by trapping and manipulating multielectron bubbles in liquid helium.

    PubMed

    Vadakkumbatt, Vaisakh; Joseph, Emil; Pal, Anustuv; Ghosh, Ambarish

    2014-08-01

    Investigations of two-dimensional electron systems (2DES) have been achieved with two model experimental systems, covering two distinct, non-overlapping regimes of the 2DES phase diagram, namely the quantum liquid phase in semiconducting heterostructures and the classical phases observed in electrons confined above the surface of liquid helium. Multielectron bubbles in liquid helium offer an exciting possibility to bridge this gap in the phase diagram, as well as to study the properties of electrons on curved flexible surfaces. However, this approach has been limited because all experimental studies have so far been transient in nature. Here we demonstrate that it is possible to trap and manipulate multielectron bubbles in a conventional Paul trap for several hundreds of milliseconds, enabling reliable measurements of their physical properties and thereby gaining valuable insight to various aspects of curved 2DES that were previously unexplored.

  7. Effects of liquid helium bubble formation in a superconducting cavity cryogenic system

    SciTech Connect

    Chang, X.; Wang, E.; Xin, T.

    2011-03-01

    We constructed a simple prototype model based on the geometry of the 56 MHz superconducting cavity for RHIC. We studied the formation, in this prototype, of bubbles of liquid helium and their thermal effects on the cavity. We found that due to the low viscosity of the liquid helium, and its small surface tension, no large bubbles formed. The tiny bubbles, generated from most of the area, behaved like light gas travelling in a free space and escaped from the trapping region. The bubbles that were generated in the trapping area, due to its descending geometry, are much bigger than the other bubbles, but due to the liquid flow generated by heating, they still are negligible compared to the size of the trapping region. We expected that the effects of bubbles in our 56 MHz cavity during operation might well be negligible.

  8. Absorption spectrum of atomic impurities in isotopic mixtures of liquid helium

    NASA Astrophysics Data System (ADS)

    Mateo, David; Hernando, Alberto; Barranco, Manuel; Mayol, Ricardo; Pi, Martí

    2011-05-01

    We theoretically describe the absorption spectrum of atomic impurities in isotopic mixtures of liquid helium within a zero-temperature density functional approach. Two situations are considered. In the first one, the absorption spectrum of Na atoms attached to He41000-He3N3 droplets with N3 values from 100 to 3000 is presented as a case study of an impurity that does not dissolve into helium droplets. In the second one, the absorption spectrum of Mg atoms in liquid He3-He4 mixtures is presented as a case study of an impurity dissolved into liquid helium. We have found that the absorption spectrum of the impurity is rather insensitive to the isotopic composition because the line shift is mostly affected by the total He density around the impurity, not by its actual composition. For bulk liquid mixtures, results are presented as a function of pressure at selected values of the He3 concentration. The results for isotopically pure He3 and He4 liquids doped with Mg are compared with available experimental data.

  9. Mechanics of liquid helium in a partially filled rotating dewar in low gravity with application to Gravity Probe-B

    NASA Technical Reports Server (NTRS)

    Schafer, C. F.; Lowry, S. A.

    1983-01-01

    The Gravity Probe-B spacecraft is composed largely of a liquid helium dewar containing an experiment package. It is shown that an unsymmetric liquid helium distribution in the dewar can cause unacceptably high forces, gravitational and gravity gradient forces, at the experiment location. It is further shown that for the planned spacecraft configuration and operational parameters, it is very likely that the liquid helium distribution in the dewar will be unsymmetric. The required symmetry can be attained by using higher operational spacecraft rotation rates.

  10. Liquid-drop-like model for cylindrical helium systems

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek

    2000-08-01

    Free liquid 4He at T=0 K with cylindrical symmetry is studied. The ground-state energy and chemical potential are computed by using a density functional approach. A liquid-drop-like model is formulated for analyzing the behavior of these observables as a function of the size of the systems. It is shown that such a model allows to get precise information about the asymptotic values of the energy per particle and surface tension.

  11. Superfluidity of grain boundaries and supersolid behavior

    NASA Astrophysics Data System (ADS)

    Balibar, Sebastien

    2007-03-01

    We have found that, at the liquid-solid equilibrium pressure Pm, supersolid behavior is due to the superfluidity of grain boundaries in solid helium [1]. After describing this experiment and reviewing some of the related theoretical work [2], we discuss the possibility that , at larger pressure (P > Pm), grain boundaries could also explain the supersolid behavior which was observed with torsional oscillators [3-6]. [1] S. Sasaki, R. Ishiguro, F. Caupin, H.J. Maris, and S. Balibar, Science 313, 1098 (2006)[2] E. Burovski, E. Kozik, A. Kuklov, N. Prokof'ev, and B. Svistunov, Phys. Rev. Lett. 94, 165301 (2005)[3] E. Kim and M.H. Chan, Nature 427, 225 (2004)[4] E. Kim and M.H. Chan, Science 305, 1941 (2004)[5] A.S.C. Rittner and J.D. Reppy, Phys. Rev. Lett. 97, 165301 (2006)[6] K. Shirahama, Bull. Am. Phys. Soc. 51, 302 (2006)

  12. Design and development of a helium injection system to improve external leakage detection during liquid nitrogen immersion tests

    NASA Astrophysics Data System (ADS)

    Townsend, Andrew; Mishra, Rakesh

    2016-10-01

    The testing of assemblies for use in cryogenic systems commonly includes evaluation at or near operating (therefore cryogenic) temperature. Typical assemblies include valves and pumps for use in liquid oxygen-liquid hydrogen rocket engines. One frequently specified method of cryogenic external leakage testing requires the assembly, pressurized with gaseous helium (GHe), be immersed in a bath of liquid nitrogen (LN2) and allowed to thermally stabilize. Component interfaces are then visually inspected for leakage (bubbles). Unfortunately the liquid nitrogen will be boiling under normal, bench-top, test conditions. This boiling tends to mask even significant leakage. One little known and perhaps under-utilized property of helium is the seemingly counter-intuitive thermodynamic property that when ambient temperature helium is bubbled through boiling LN2 at a temperature of -195.8 °C, the temperature of the liquid nitrogen will reduce. This paper reports on the design and testing of a novel proof-of-concept helium injection control system confirming that it is possible to reduce the temperature of an LN2 bath below boiling point through the controlled injection of ambient temperature gaseous helium and then to efficiently maintain a reduced helium flow rate to maintain a stabilized liquid temperature, enabling clear visual observation of components immersed within the LN2. Helium saturation testing is performed and injection system sizing is discussed.

  13. Significant structure theory applied to liquid helium-3

    PubMed Central

    Oh, Youngie; Jhon, Mu Shik; Eyring, Henry

    1977-01-01

    The significant structure theory of liquids is successfully applied to the quantum liquid 3He. The partition function uses the Debye partition function for the solid-like molecules and the Fermi-Dirac partition function for the gas-like degrees of freedom. To evaluate the gas-like partition function, numerical calculations are performed and some integral functions appearing in the equation of state of the ideal Fermi-Dirac gas are tabulated. In the solid-like molecules, the molar volume Vs depends on the temperature, and a linear dependence is used. The thermodynamic properties, such as molar volume, vapor pressure, entropy, heat capacity, and the critical constants as well as the surface tension of liquid 3He are calculated. The agreement between theory and experiment is satisfactory. PMID:16592463

  14. Process model and capacity upgrades of the CTI-4000 liquid helium coldbox

    NASA Astrophysics Data System (ADS)

    Hansen, Benjamin; Quack, Hans; Klebaner, Arkadiy

    2014-01-01

    Fermi National Accelerator Laboratory (FNAL) is in the process of re-commissioning a vintage CTI-4000 liquid helium coldbox, initially supplied by CTI-Cryogenics/Sulzer to Los Alamos in 1979. The coldbox was originally designed as a liquid helium refrigerator with capacity of ˜1200 W at nominal 4-K. The process utilized LN2 precooling, in-series operation of two centrifugal gas bearing turboexpanders and final Joule-Thomson (J-T) expansion. At FNAL, the coldbox will be utilized as a liquefier to support 2-K operations. A process model was developed to aid in the upgrade decisions and used to determine the nominal capacity of the liquefier. Capacity upgrades are achieved by safely utilizing the internal LN2 precooler, the addition of a 3-inch reciprocating wet expansion engine and increasing the overall process pressure by recertifying two limiting pressure vessels to a higher MAWP.

  15. Large volume liquid helium relief device verifacation apparatus for the alpha magnetic spectrometer

    NASA Astrophysics Data System (ADS)

    Klimas, Richard John; McIntyre, P.; Colvin, John; Zeigler, John; Van Sciver, Steven; Ting, Samual

    2012-06-01

    Here we present details of an experiment for verifying the liquid helium vessel relief device for the Alpha Magnetic Spectrometer-02 (AMS-02). The relief device utilizes a series of rupture discs designed to open in the event of a vacuum failure of the AMS-02 cryogenic system. A failure of this type is classified to be a catastrophic loss of insulating vacuum accident. This apparatus differs from other approaches due to the size of the test volumes used. The verification apparatus consists of a 250 liter vessel used for the test quantity of liquid helium that is located inside a vacuum insulated vessel. A large diameter valve is suddenly opened to simulate the loss of insulating vacuum in a repeatable manner. Pressure and temperature vs. time data are presented and discussed in the context of the AMS-02 hardware configuration.

  16. Process model and capacity upgrades of the CTI-4000 liquid helium coldbox

    SciTech Connect

    Hansen, Benjamin; Klebaner, Arkadiy; Quack, Hans

    2014-01-29

    Fermi National Accelerator Laboratory (FNAL) is in the process of re-commissioning a vintage CTI-4000 liquid helium coldbox, initially supplied by CTI-Cryogenics/Sulzer to Los Alamos in 1979. The coldbox was originally designed as a liquid helium refrigerator with capacity of ∼1200 W at nominal 4-K. The process utilized LN{sub 2} precooling, in-series operation of two centrifugal gas bearing turboexpanders and final Joule-Thomson (J-T) expansion. At FNAL, the coldbox will be utilized as a liquefier to support 2-K operations. A process model was developed to aid in the upgrade decisions and used to determine the nominal capacity of the liquefier. Capacity upgrades are achieved by safely utilizing the internal LN2 precooler, the addition of a 3-inch reciprocating wet expansion engine and increasing the overall process pressure by recertifying two limiting pressure vessels to a higher MAWP.

  17. A Liquid-Helium-Cooled Absolute Reference Cold Load forLong-Wavelength Radiometric Calibration

    SciTech Connect

    Bensadoun, M.; Witebsky, C.; Smoot, George F.; De Amici,Giovanni; Kogut, A.; Levin, S.

    1990-05-01

    We describe a large (78-cm) diameter liquid-helium-cooled black-body absolute reference cold load for the calibration of microwave radiometers. The load provides an absolute calibration near the liquid helium (LHe) boiling point, accurate to better than 30 mK for wavelengths from 2.5 to 25 cm (12-1.2 GHz). The emission (from non-LHe temperature parts of the cold load) and reflection are small and well determined. Total corrections to the LHe boiling point temperature are {le} 50 mK over the operating range. This cold load has been used at several wavelengths at the South Pole and at the White Mountain Research Station. In operation, the average LHe loss rate was {le} 4.4 l/hr. Design considerations, radiometric and thermal performance and operational aspects are discussed. A comparison with other LHe-cooled reference loads including the predecessor of this cold load is given.

  18. A liquid-helium-cooled absolute reference cold load for long-wavelength radiometric calibration

    NASA Technical Reports Server (NTRS)

    Bensadoun, Marc; Witebsky, Chris; Smoot, George; De Amici, Giovanni; Kogut, AL; Levin, Steve

    1992-01-01

    Design, radiometric and thermal performance, and operation of a large diameter (78 cm) liquid-helium-cooled blackbody absolute reference cold load (CL) for the calibration of microwave radiometers is described. CL provides an absolute calibration near the liquid-helium (LHe) boiling point, with total uncertainty in the radiometric temperature of less than 30 mK over the 2.5-23 cm wavelength operating range. CL was used at several wavelengths at the South Pole, Antarctica and the White Mountain Research Center, California. Results show that, for the instruments operated at 20-, 12-, 7.9-, and 4.0 cm wavelength at the South Pole, the total corrections to the LHe boiling-point temperature (about 3.8 K) were 48 +/-23, 18 +/-10, 10 +/-18, and 15 +/-mK.

  19. Stability of precessing superfluid neutron stars.

    PubMed

    Glampedakis, K; Andersson, N; Jones, D I

    2008-02-29

    We discuss a new superfluid instability occurring in the interior of mature neutron stars with implications for free precession. This instability is similar to the instability which is responsible for the formation of turbulence in superfluid helium. We demonstrate that the instability is unlikely to affect slowly precessing systems with weak superfluid coupling. In contrast, fast precession in systems with strong coupling appears to be generically unstable. This raises serious questions about our understanding of neutron star precession and complicates attempts to constrain neutron star interiors using such observations.

  20. Calculation of the Shape of S-State Electron Bubbles in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Maris, Humphrey J.; Guo, Wei

    2007-08-01

    We consider the shape of electron bubbles in liquid helium. Grinfeld and Kojima (Phys. Rev. Lett. 91, 105301, 2003) have shown that the in a certain pressure range the 2S electron bubble is unstable against small distortions with l=3 and loses its spherical symmetry. We report more detailed calculations of this effect and also study the behavior of the 3S and 2P bubbles.

  1. Possible quantum liquid crystal phases of helium monolayers

    NASA Astrophysics Data System (ADS)

    Nakamura, S.; Matsui, K.; Matsui, T.; Fukuyama, Hiroshi

    2016-11-01

    The second-layer phase diagrams of 4He and 3He adsorbed on graphite are investigated. Intrinsically rounded specific-heat anomalies are observed at 1.4 and 0.9 K, respectively, over extended density regions in between the liquid and incommensurate solid phases. They are identified to anomalies associated with the Kosterlitz-Thouless-Halperin-Nelson-Young type two-dimensional melting. The prospected low temperature phase (C2 phase) is a commensurate phase or a quantum hexatic phase with quasi-bond-orientational order, both containing zero-point defectons. In either case, this would be the first atomic realization of the quantum liquid crystal, a new state of matter. From the large enhancement of the melting temperature over 3He, we propose to assign the observed anomaly of 4He-C 2 phase at 1.4 K to the hypothetical supersolid or superhexatic transition.

  2. Atomically resolved phase transition of fullerene cations solvated in helium droplets

    NASA Astrophysics Data System (ADS)

    Kuhn, M.; Renzler, M.; Postler, J.; Ralser, S.; Spieler, S.; Simpson, M.; Linnartz, H.; Tielens, A. G. G. M.; Cami, J.; Mauracher, A.; Wang, Y.; Alcamí, M.; Martín, F.; Beyer, M. K.; Wester, R.; Lindinger, A.; Scheier, P.

    2016-11-01

    Helium has a unique phase diagram and below 25 bar it does not form a solid even at the lowest temperatures. Electrostriction leads to the formation of a solid layer of helium around charged impurities at much lower pressures in liquid and superfluid helium. These so-called `Atkins snowballs' have been investigated for several simple ions. Here we form HenC60+ complexes with n exceeding 100 via electron ionization of helium nanodroplets doped with C60. Photofragmentation of these complexes is measured by merging a tunable narrow-bandwidth laser beam with the ions. A switch from red- to blueshift of the absorption frequency of HenC60+ on addition of He atoms at n=32 is associated with a phase transition in the attached helium layer from solid to partly liquid (melting of the Atkins snowball). Elaborate molecular dynamics simulations using a realistic force field and including quantum effects support this interpretation.

  3. Atomically resolved phase transition of fullerene cations solvated in helium droplets

    PubMed Central

    Kuhn, M.; Renzler, M.; Postler, J.; Ralser, S.; Spieler, S.; Simpson, M.; Linnartz, H; Tielens, A. G. G. M.; Cami, J.; Mauracher, A.; Wang, Y.; Alcamí, M.; Martín, F.; Beyer, M. K.; Wester, R.; Lindinger, A.; Scheier, P.

    2016-01-01

    Helium has a unique phase diagram and below 25 bar it does not form a solid even at the lowest temperatures. Electrostriction leads to the formation of a solid layer of helium around charged impurities at much lower pressures in liquid and superfluid helium. These so-called ‘Atkins snowballs' have been investigated for several simple ions. Here we form HenC60+ complexes with n exceeding 100 via electron ionization of helium nanodroplets doped with C60. Photofragmentation of these complexes is measured by merging a tunable narrow-bandwidth laser beam with the ions. A switch from red- to blueshift of the absorption frequency of HenC60+ on addition of He atoms at n=32 is associated with a phase transition in the attached helium layer from solid to partly liquid (melting of the Atkins snowball). Elaborate molecular dynamics simulations using a realistic force field and including quantum effects support this interpretation. PMID:27874002

  4. UNIQUE METHOD FOR LIQUID NITROGEN PRECOOLING OF A PLATE FIN HEAT EXCHANGER IN A HELIUM REFRIGERATION CYCLE.

    SciTech Connect

    Weber, T

    2004-06-02

    Precooling of helium by means of liquid nitrogen is one the oldest and most common process features used in helium refrigerators. The principal tasks are to permit a rapid cool down to 80 K of the plant, to increase the cooling power of the plant in low temperature operation and to increase the rate of pure liquid production. The advent of aluminum plate fin heat exchangers in the design of helium refrigerators has made this task more complicated because of the potential damage to these heat exchangers.

  5. Vortices in rotating superfluid 3He

    PubMed Central

    Lounasmaa, Olli V.; Thuneberg, Erkki

    1999-01-01

    In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe. PMID:10393895

  6. Vortices in rotating superfluid 3He.

    PubMed

    Lounasmaa, O V; Thuneberg, E

    1999-07-06

    In this review we first present an introduction to 3He and to the ROTA collaboration under which most of the knowledge on vortices in superfluid 3He has been obtained. In the physics part, we start from the exceptional properties of helium at millikelvin temperatures. The dilemma of rotating superfluids is presented. In 4He and in 3He-B the problem is solved by nucleating an array of singular vortex lines. Their experimental detection in 3He by NMR is described next. The vortex cores in 3He-B have two different structures, both of which have spontaneously broken symmetry. A spin-mass vortex has been identified as well. This object is characterized by a flow of spins around the vortex line, in addition to the usual mass current. A great variety of vortices exist in the A phase of 3He; they are either singular or continuous, and their structure can be a line or a sheet or fill the whole liquid. Altogether seven different types of vortices have been detected in 3He by NMR. We also describe briefly other experimental methods that have been used by ROTA scientists in studying vortices in 3He and some important results thus obtained. Finally, we discuss the possible applications of experiments and theory of 3He to particle physics and cosmology. In particular, we report on experiments where superfluid 3He-B was heated locally by absorption of single neutrons. The resulting events can be used to test theoretical models of the Big Bang at the beginning of our universe.

  7. Computer simulations of helium-solvated ions: solid-like versus liquid-like defect structures

    NASA Astrophysics Data System (ADS)

    Paolini, Stefano; Ancilotto, Francesco; Toigo, Flavio

    2007-03-01

    The local order around several alkali (Li^+ and Na^+) and alkali-earth (Be^+, Mg^+ and Ca^+) ions in ^4He clusters has been studied using ground-state path integral Monte Carlo simulations. We apply a criterion based on multipole dynamical correlations to discriminate between solid-like versus liquid-like behavior of the He solvent surrounding the impurity-ion. In agreement with existing experimental measurements in bulk helium, our findings suggest that Be^+ produces a solid-(``snowball'')-like structure, similarly to alkali ions and in contrast to heavier alkali-earth ones, for which a liquid-like environment is predicted.

  8. Stick-Slip Motion of the Wigner Solid on Liquid Helium

    NASA Astrophysics Data System (ADS)

    Rees, David G.; Beysengulov, Niyaz R.; Lin, Juhn-Jong; Kono, Kimitoshi

    2016-05-01

    We present time-resolved transport measurements of a Wigner solid (WS) on the surface of liquid helium confined in a micron-scale channel. At rest, the WS is "dressed" by a cloud of quantized capillary waves (ripplons). Under a driving force, we find that repeated WS-ripplon decoupling leads to stick-slip current oscillations, the frequency of which can be tuned by adjusting the temperature, pressing electric field, or electron density. The WS on liquid He is a promising system for the study of polaronlike decoupling dynamics.

  9. Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium

    NASA Astrophysics Data System (ADS)

    Guo, Wei

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron bubbles and experiments on imaging individual electron bubbles in liquid helium. We studied the effect of zero-point and thermal fluctuations on the shape of ground state electron bubbles in liquid helium. The results are used to determine the line shape for the 1S to 1P optical transition. The calculated line shape is in very good agreement with the experimental measurements of Grimes and Adams. For 1S to 2P transition, the obtained transition line width agrees well with the measured data of Zipfel over a range of pressure up to 15 bars. Fluctuations in the bubble shape also make other "unallowed" transitions possible. The transition cross-sections from the 1S state to the 1D and 2D states are calculated with magnitude approximately two orders smaller than that of the 1S to 1P and 2P transitions. In our electron bubble imaging experiments, a planar ultrasonic transducer was used to generate strong sound wave pulse in liquid helium. The sound pulse passed through the liquid so as to produce a transient negative pressure over a large volume (˜ 1 cm3). An electron bubble that was passed by the sound pulse exploded for a fraction of a microsecond and grew to have a radius of around 10 microns. While the bubble had this large size it was illuminated with a flash lamp and its position was recorded. In this way, we can determine its position. Through the application of a series of sound pulses, we can then take images along the track of individual electrons. The motion of individual electron bubbles has been successfully monitored. Interesting bubble tracks that may relate to electrons

  10. A Ring with a Spin: Superfluidity in a toroidal Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Ramanathan, Anand Krishnan

    2011-12-01

    Superfluidity is a remarkable phenomenon. Superfluidity was initially characterized by flow without friction, first seen in liquid helium in 1938, and has been studied extensively since. Superfluidity is believed to be related to, but not identical to Bose-Einstein condensation, a statistical mechanical phenomena predicted by Albert Einstein in 1924 based on the statistics of Satyendra Nath Bose, where bosonic atoms make a phase transition to form a Bose-Einstein condensate (BEC), a gas which has macroscopic occupation of a single quantum state. Developments in laser cooling of neutral atoms and the subsequent realization of Bose-Einstein condensates in ultracold gases have opened a new window into the study of superfluidity and its relation to Bose-Einstein condensation. In our atomic sodium BEC experiment, we studied superfluidity and dissipationless flow in an all-optical toroidal trap, constructed using the combination of a horizontal "sheet"-like beam and vertical "ring"-like beam, which, like a circuit loop, allows flow around the ring. On inducing a single quantum of circulation in the condensate, the smoothness and uniformity of the toroidal BEC enabled the sustaining of a persistent current lasting 40 seconds, limited by the lifetime of the BEC due to background gas pressure. This success set the stage for further experiments studying superfluidity. In a first set of experiments, we studied the stability of the persistent current by inserting a barrier in the flow path of the ring. The superflow stopped abruptly at a barrier strength such that the local flow velocity at the barrier exceeded a critical velocity, which supported decay via the creation of a vortex-antivortex pair. Our precise control in inducing and arresting superflow in the BEC is a first step toward studying other aspects of superfluidity, such as the effect of temperature and dimensionality. This thesis discusses these experiments and also details partial-transfer absorption imaging, an

  11. Producing and imaging a thin line of He*₂ molecular tracers in helium-4.

    PubMed

    Gao, J; Marakov, A; Guo, W; Pawlowski, B T; Van Sciver, S W; Ihas, G G; McKinsey, D N; Vinen, W F

    2015-09-01

    Cryogenic helium-4 has long been recognized as a useful material in fluids research. The unique properties of helium-4 in the gaseous phase and the normal liquid phase allow for the generation of turbulent flows with exceptionally high Reynolds and Rayleigh numbers. In the superfluid phase, helium-4 exhibits two-fluid hydrodynamics and possesses fascinating properties due to its quantum nature. However, studying the flows in helium-4 has been very challenging largely due to the lack of effective visualization and velocimetry techniques. In this article, we discuss the development of novel instrumentation for flow-visualization in helium based on the generation and imaging of thin lines of metastable He*₂ tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. By observing the displacement and distortion of the tracer lines in helium, quantitative information about the flow field can be extracted. We present experimental results in the study of thermal counterflow in superfluid helium that validate the concept of this technique. We also discuss anticipated future developments of this powerful visualization technique.

  12. Liquid helium free mechanical property test system with G-M cryocoolers

    NASA Astrophysics Data System (ADS)

    Zhang, Hengcheng; Xu, Dong; Huang, Rongjin; Huang, Chuanjun; Liu, Huiming; Han, Yemao; Li, Laifeng

    2017-07-01

    In the present work, a cryogenic mechanical property testing system conduction-cooled by two G-M cryocoolers was developed. The testing sample can be cooled from room temperature to 2.7 K within 7.5 h. The sample was first cooled down to 11.1 K directly by the two G-M cryocoolers and then cooled down to 2.7 K by decompressing the chamber. Instead of liquid helium, the cooling process is characterized by cooling with recycled helium gas as heat transfer medium. The heat load of the system was analyzed and optimizations were adopted in terms of material selections and design. The static load capacity of the system reaches 200 kN and the fatigue load capacity can reach 50 kN. This system can be installed onto an electronic universal testing machine or a fatigue testing machine to characterize static tension, fracture mechanics or fatigue properties at tunable low temperatures. Tensile properties of 316L austenitic stainless steels at 4.2 K were tested with the system and the results were compared with those obtained by cooled using liquid helium, which demonstrates high reliability.

  13. Point-contact transport properties of strongly correlated electrons on liquid helium.

    PubMed

    Rees, D G; Kuroda, I; Marrache-Kikuchi, C A; Höfer, M; Leiderer, P; Kono, K

    2011-01-14

    We present transport measurements of a nondegenerate two-dimensional electron system on the surface of liquid helium at a point constriction. The constriction is formed in a microchannel by a split gate beneath the helium surface. The electrostatic energy of the electron system, which depends in part on the electron density, determines the split-gate voltage threshold of current flow through the constriction. Steplike increases in conductance are observed as the confinement strength is reduced. As the Coulomb interaction between electrons is strong, we attribute this effect to the increase in the number of electrons that can pass simultaneously through the constriction. Close to the threshold, single-electron transport is observed.

  14. Construction and testing of a general purpose 50 liter liquid helium cryovessel

    SciTech Connect

    Schubert, J.; Blosser, H.; Stork, G.; Zeller, A.

    1996-12-31

    The authors have built and are operating a 50 liter liquid helium vessel with an access port for easy insertion of experiments. The vessel is primarily used to test components of superconducting magnet systems, such as cryogenic current leads. The access port is set at a 45{degrees} angle and the entire vessel may be tilted 45{degrees} in either direction so that current leads may be tested in any orientation from horizontal to vertical. The vessel was designed to be easily disassembled so that experimental apparatus too large for the access port may be mounted directly in the helium can. This way devices 40 cm in diameter may be tested. The heat load of the vessel has been measured under a variety of experimental conditions. A few devices tested so far in the cryovessel are briefly described.

  15. Two-phase flow of solid hydrogen particles and liquid helium

    NASA Astrophysics Data System (ADS)

    Xu, J.; Rouelle, A.; Smith, K. M.; Celik, D.; Hussaini, M. Y.; Van Sciver, S. W.

    2004-06-01

    Atomic hydrogen propellant feed systems may require transporting solid hydrogen particles containing atomic species from storage tanks to the engines using liquid helium as the carrier fluid. In this paper, a three-dimensional two-phase mixture model, along with the standard k- ɛ mixture turbulence model is employed to study the turbulent mixing of the fluid-particle slurry system. Numerical results show that turbulent flow is required to keep the hydrogen particles in suspension, which otherwise form a sliding layer of particles on top of the helium layer. Hydrogen particle concentration profiles in the slurry system are functions of particle size, flow velocity, and influx volume fraction of hydrogen particles. Particle dispersion at different Stokes numbers, different Kolmogorov length scales, and different time scales are discussed.

  16. Room-temperature superfluidity in a polariton condensate

    NASA Astrophysics Data System (ADS)

    Lerario, Giovanni; Fieramosca, Antonio; Barachati, Fábio; Ballarini, Dario; Daskalakis, Konstantinos S.; Dominici, Lorenzo; de Giorgi, Milena; Maier, Stefan A.; Gigli, Giuseppe; Kéna-Cohen, Stéphane; Sanvitto, Daniele

    2017-09-01

    Superfluidity--the suppression of scattering in a quantum fluid at velocities below a critical value--is one of the most striking manifestations of the collective behaviour typical of Bose-Einstein condensates. This phenomenon, akin to superconductivity in metals, has until now been observed only at prohibitively low cryogenic temperatures. For atoms, this limit is imposed by the small thermal de Broglie wavelength, which is inversely related to the particle mass. Even in the case of ultralight quasiparticles such as exciton-polaritons, superfluidity has been demonstrated only at liquid helium temperatures. In this case, the limit is not imposed by the mass, but instead by the small binding energy of Wannier-Mott excitons, which sets the upper temperature limit. Here we demonstrate a transition from supersonic to superfluid flow in a polariton condensate under ambient conditions. This is achieved by using an organic microcavity supporting stable Frenkel exciton-polaritons at room temperature. This result paves the way not only for tabletop studies of quantum hydrodynamics, but also for room-temperature polariton devices that can be robustly protected from scattering.

  17. Superfluid thermodynamic cycle refrigerator

    DOEpatents

    Swift, Gregory W.; Kotsubo, Vincent Y.

    1992-01-01

    A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.

  18. Superfluid thermodynamic cycle refrigerator

    DOEpatents

    Swift, G.W.; Kotsubo, V.Y.

    1992-12-22

    A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of [sup 3]He in a single phase [sup 3]He-[sup 4]He solution. The [sup 3]He in superfluid [sup 4]He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid [sup 3]He at an initial concentration in superfluid [sup 4]He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of [sup 4]He while restricting passage of [sup 3]He. The [sup 3]He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K. 12 figs.

  19. Ballistic Evaporation and Solvation of Helium Atoms at the Surfaces of Protic and Hydrocarbon Liquids.

    PubMed

    Johnson, Alexis M; Lancaster, Diane K; Faust, Jennifer A; Hahn, Christine; Reznickova, Anna; Nathanson, Gilbert M

    2014-11-06

    Atomic and molecular solutes evaporate and dissolve by traversing an atomically thin boundary separating liquid and gas. Most solutes spend only short times in this interfacial region, making them difficult to observe. Experiments that monitor the velocities of evaporating species, however, can capture their final interactions with surface solvent molecules. We find that polarizable gases such as N2 and Ar evaporate from protic and hydrocarbon liquids with Maxwell-Boltzmann speed distributions. Surprisingly, the weakly interacting helium atom emerges from these liquids at high kinetic energies, exceeding the expected energy of evaporation from salty water by 70%. This super-Maxwellian evaporation implies in reverse that He atoms preferentially dissolve when they strike the surface at high energies, as if ballistically penetrating into the solvent. The evaporation energies increase with solvent surface tension, suggesting that He atoms require extra kinetic energy to navigate increasingly tortuous paths between surface molecules.

  20. The viscosity and the thermal conductivity of normal liquid Helium 3 in the LOCV frame-work

    NASA Astrophysics Data System (ADS)

    Modarres, M.; Rahmat, M.

    2017-01-01

    The lowest order constrained variational (LOCV) method is used to evaluate the transport properties of normal liquid Helium-3 (3 He) within the Landau-Abrikosov-Khalatnikov (LAK) formalism. The LOCV effective two-body interaction of the liquid Helium 3 is used to calculate the differential cross-section and the scattering probability, which is needed to solve the LAK equations. It is shown that, the choice of effective mass has crucial role on the resulting viscosity and thermal conductivity of normal liquid 3 He. Our LOCV-LAK calculations are compared with the other theoretical and experimental results.

  1. Research and development of a helium-4 based solar neutrino detector. Progress report, November 1, 1991--April 30, 1993

    SciTech Connect

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

    1993-05-01

    Superfluid helium possesses unique properties that enable it to be used as the major component of a very sensitive calorimetric detector: it is extremely pure, and the energy deposited in it is carried out by elementary excitations of the liquid which can produce quantum evaporation of He atoms at a free surface. It has a major advantage of being able to achieve very low background levels. Experimental results presented on the development of helium-4 detector include sensitivity, heat capacity of wafer-calorimeters, coincidence measurements, spectrum of alpha particles in helium, and quantum evaporation: angular dependence and efficiency. 29 refs., 16 figs., 1 tab.

  2. Fluidization of granular media wetted by liquid 4He.

    PubMed

    Huang, K; Sohaili, M; Schröter, M; Herminghaus, S

    2009-01-01

    We explore experimentally the fluidization of vertically agitated polymethylmethacrylate spheres wetted by liquid 4He . By controlling the temperature around the lambda point, we change the properties of the wetting liquid from a normal fluid (helium I) to a superfluid (helium II). For wetting by helium I, the critical acceleration for fluidization (Gamma_{c}) shows a steep increase close to the saturation of the vapor pressure in the sample cell. For helium II wetting, Gamma_{c} starts to increase at about 75% saturation, indicating that capillary bridges are enhanced by the superflow of the unsaturated helium film. Above saturation, Gamma_{c} enters a plateau regime where the capillary force between particles is independent of the bridge volume. The plateau value is found to vary with temperature and shows a peak at 2.1K , which we attribute to the influence of the specific heat of liquid helium.

  3. Performance Study on ST/JT Hybrid Cryocoolers Working at Liquid Helium Temperature

    NASA Astrophysics Data System (ADS)

    Dongli, Liu; Xuan, Tao; Xiao, Sun; Zhihua, Gan

    The ST/JT hybridcryocooler consists of a Stirling-typecryocooler and a J-T loop. The common process of steady-state operation is given. Pressure-Enthalpy map analysis and thermodynamic calculation showhow the precooling temperature, high pressure and recuperator effectiveness affect thecooling powerat liquid helium temperature. Applying the current performance level of the Stirling cooler,the overall COP of the hybrid cryocooleris roughly optimized. This performance study shows that the hybrid cryocooler can develop its performance potential with improved J-T compressors with larger pressure ratio and aprecooler working at lower temperature.

  4. Liquid helium centrifugal pump characteristics from 80 g/s to 1200 g/s

    NASA Astrophysics Data System (ADS)

    Pengo, R.; Junker, S.; ten Kate, H. H. J.

    2010-01-01

    The large amount of data collected from three different centrifugal liquid helium pumps tested, namely with 80, 600 and 1200 g/s nominal mass flow are reviewed. The data include the analysis of the characteristic curves, their total efficiencies, their Net Positive Suction Head (NPSH) and the slip factor. The 1200 g/s pumps tested are of the full emission type, with curved blades, whilst the other pumps have straight blades. The pumps were also tested at different rotary speeds. The pumps were manufactured by Barber & Nichols (Denver, USA).

  5. Nitrogen gas propagation in a liquid helium cooled vacuum tube following a sudden vacuum loss

    NASA Astrophysics Data System (ADS)

    Dhuley, R. C.; Van Sciver, S. W.

    2017-02-01

    We present experimental measurements and analysis of propagation of the nitrogen gas that was vented to a high vacuum tube immersed in liquid helium (LHe). The scenario resembles accidental venting of atmospheric air to a SRF beam-line and was investigated to understand how the in-flowing air would propagate in such geometry. The gas front propagation speed in the tube was measured using pressure probes and thermometers installed at regular intervals over the tube length. The experimental data show the front speed to decrease along the vacuum tube. The empirical and analytical models developed to characterize the front deceleration are summarized.

  6. Plasma excitation dispersion in non-degenerate quantum wire over liquid helium

    NASA Astrophysics Data System (ADS)

    Antsygina, Tatiana N.; Chishko, Konstantin A.; Degtyaryov, Igor A.; Poltavsky, Igor I.; Sokolov, Sviatoslav S.; Studart, Nelson

    2017-05-01

    We calculate the dispersion laws of plasma oscillations for the quasi-one-dimensional multisubband non-degenerate charge system realized in a conducting electron channel over the surface of liquid helium. The influence on plasma dispersion from an external magnetic field is considered. A novel two-subband approach within the random-phase approximation is employed for both intra- and intersubband plasmons. Our results are compared with those obtained previously in quasi-crystalline approach; despite being qualitatively similar, there are quantitative differences, especially at high wave numbers.

  7. Epoxy encapsulation of the Cernox™ SD thermometer for measuring the temperature of surfaces in liquid helium

    NASA Astrophysics Data System (ADS)

    Dhuley, R. C.; Van Sciver, S. W.

    2016-07-01

    We describe a procedure to pot a Cernox™ thermometer with the SD package in Stycast epoxy. The potting adapts the thermometer for measuring the temperature of a surface immersed in liquid helium (LHe) and other cryogens. The technique thermally insulates the sensor chip from the cryogen while preserving the surface mounting capability of the SD package. The potting introduced <1% shift in the resistance, <0.5% shift in the calibration at 4.2 K and 77 K, and provided repeatable measurements during thermal cycles between room temperature and 4.2 K.

  8. Flight model performance test results of a helium dewar for the soft X-ray spectrometer onboard ASTRO-H

    NASA Astrophysics Data System (ADS)

    Yoshida, Seiji; Miyaoka, Mikio; Kanao, Ken'ichi; Tsunematsu, Shoji; Otsuka, Kiyomi; Hoshika, Shunji; Mitsuda, Kazuhisa; Yamasaki, Noriko; Takei, Yoh; Fujimoto, Ryuichi; Sato, Yoichi; DiPirro, Mike; Shirron, Peter

    2016-03-01

    ASTRO-H is a Japanese X-ray astronomy satellite, scheduled to be launched in fiscal year 2015. The mission includes a soft X-ray spectrometer instrument (SXS), which contains an X-ray micro calorimeter operating at 50 mK by using an adiabatic demagnetization refrigerator (ADR). The heat sink of the ADR is superfluid liquid helium below 1.3 K. The required lifetime of the superfluid helium is 3 years or more. In order to realize this lifetime, we have improved the thermal performance from the engineering model (EM) while maintaining the mechanical performance. Then, we have performed a thermal test of the flight model (FM). The results were that the heat load to the helium tank was reduced to below 0.8 mW in the FM from 1.2 mW in the EM. Therefore, the lifetime of the superfluid helium is more than 3 years with 30 L of liquid helium. In this paper, the thermal design and thermal test results are described.

  9. Design and construction of a prototype superfluid helium cryostat for the short straight sections of the CERN Large Hadron Collider (LHC)

    SciTech Connect

    Cameron, W.; Jenny, B.; Riddone, G.; Rohmig, P.; Weelderen, R. van

    1994-12-31

    The lattice of the CERN Large Hadron Collider (LHC) will contain 384 Short Straight Section (SSS) units, one in every 51 m half-cell. A Short Straight Section is composed of a twin aperture high-field superconducting quadrupole, two combined-function corrector magnets, and quench protection diodes, all operating in pressurised helium II at 1.9 K. The SSS cryostat also contains a barrier for sectoring the insulation vacuum, and a Technical Service Module housing beam diagnostics, current feedthroughs and instrumentation capillaries, as well as cryogenic valves and pipework serving the local half-cell cooling loop. The helium vessel with its magnets, weighing about 6000 kg, stands on two low heat leak supports. Separate vacuum manifolds permit pumping the beam pipes every 51 m. Two thermal insulation systems, the radiative insulation and a gaseous helium cooled thermal shield, intercept incoming radiative and conductive heat. All these components must be arranged to perform without interference and within the tight constraints of minimum transverse and longitudinal space occupancy. The design and function of the prototype SSS and its main features, covering mechanical and thermal aspects as well a construction details, are described.

  10. Simplified Methodology to Estimate the Maximum Liquid Helium (LHe) Cryostat Pressure from a Vacuum Jacket Failure

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Richards, W. Lance

    2015-01-01

    The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared astronomical observation experiments. These experiments carry sensors cooled to liquid helium temperatures. The liquid helium supply is contained in large (i.e., 10 liters or more) vacuum-insulated dewars. Should the dewar vacuum insulation fail, the inrushing air will condense and freeze on the dewar wall, resulting in a large heat flux on the dewar's contents. The heat flux results in a rise in pressure and the actuation of the dewar pressure relief system. A previous NASA Engineering and Safety Center (NESC) assessment provided recommendations for the wall heat flux that would be expected from a loss of vacuum and detailed an appropriate method to use in calculating the maximum pressure that would occur in a loss of vacuum event. This method involved building a detailed supercritical helium compressible flow thermal/fluid model of the vent stack and exercising the model over the appropriate range of parameters. The experimenters designing science instruments for SOFIA are not experts in compressible supercritical flows and do not generally have access to the thermal/fluid modeling packages that are required to build detailed models of the vent stacks. Therefore, the SOFIA Program engaged the NESC to develop a simplified methodology to estimate the maximum pressure in a liquid helium dewar after the loss of vacuum insulation. The method would allow the university-based science instrument development teams to conservatively determine the cryostat's vent neck sizing during preliminary design of new SOFIA Science Instruments. This report details the development of the simplified method, the method itself, and the limits of its applicability. The simplified methodology provides an estimate of the dewar pressure after a loss of vacuum insulation that can be used for the initial design of the liquid helium dewar vent stacks. However, since it is not an exact

  11. Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S.; Tucker, S.

    2006-01-01

    In support of the development of a zero gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray bar thermodynamic vent system (TVS). Fourteen days of testing was performed in August - September 2005, with an ambient heat leak of about 70-80 watts and tank fill levels of 90%, 50%, and 25%. The TVS successfully controlled the tank pressure within a +/- 3.45 kPa (+/- 0.5 psi) band with various helium concentration levels in the ullage. Relative to pressure control with an "all hydrogen" ullage, the helium presence resulted in 10 to 30 per cent longer pressure reduction durations, depending on the fill level, during the mixing/venting phase of the control cycle. Additionally, the automated control cycle was based on mixing alone for pressure reduction until the pressure versus time slope became positive, at which time the Joule-Thomson vent was opened. Testing was also conducted to evaluate thermodynamic venting without the mixer operating, first with liquid then with vapor at the recirculation line inlet. Although ullage stratification was present, the ullage pressure was successfully controlled without the mixer operating. Thus, if vapor surrounded the pump inlet in a reduced gravity situation, the ullage pressure can still be controlled by venting through the TVS Joule Thomson valve and heat exchanger. It was evident that the spray bar configuration, which extends almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the mixer operating. Details regarding the test setup and procedures are presented in the paper. 1

  12. Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S.; Tucker, S.

    2006-01-01

    In support of the development of a zero gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray bar thermodynamic vent system (TVS). Fourteen days of testing was performed in August - September 2005, with an ambient heat leak of about 70-80 watts and tank fill levels of 90%, 50%, and 25%. The TVS successfully controlled the tank pressure within a +/- 3.45 kPa (+/- 0.5 psi) band with various helium concentration levels in the ullage. Relative to pressure control with an "all hydrogen" ullage, the helium presence resulted in 10 to 30 per cent longer pressure reduction durations, depending on the fill level, during the mixing/venting phase of the control cycle. Additionally, the automated control cycle was based on mixing alone for pressure reduction until the pressure versus time slope became positive, at which time the Joule-Thomson vent was opened. Testing was also conducted to evaluate thermodynamic venting without the mixer operating, first with liquid then with vapor at the recirculation line inlet. Although ullage stratification was present, the ullage pressure was successfully controlled without the mixer operating. Thus, if vapor surrounded the pump inlet in a reduced gravity situation, the ullage pressure can still be controlled by venting through the TVS Joule Thomson valve and heat exchanger. It was evident that the spray bar configuration, which extends almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the mixer operating. Details regarding the test setup and procedures are presented in the paper. 1

  13. Helium Nanodroplet Isolation of Ionic Liquid Vapor: Inrared Laser Spectroscopy of [EMIM][Tf_2N

    NASA Astrophysics Data System (ADS)

    Flynn, Steven D.; Douberly, Gary E.

    2012-06-01

    The Infrared spectrum of the vapor produced upon thermal vaporization of the [emim][Tf_2N] ionic liquid has been obtained using the helium nanodroplet isolation method. Despite the low vapor pressure of [emim][Tf_2N], sufficient gas phase densities are produced, allowing for efficient helium nanodroplet pick-up. The mass spectrum of the emim[Tf_2N] doped droplet beam shows signatures that have been attributed in gas phase measurements to the presence of isolated, intact [emim][Tf_2N] ion-pairs. Furthermore, the mass spectrometry results indicate that emim[Tf_2N] does not undergo thermal decomposition at 410 K. Comparisons are made between the experimental measurements and ab initio calculations (mp2/6-311++g(d,p)) of the CH stretch vibrational bands and permanent electric dipole moments for several [emim][Tf_2N] low energy isomers. The helium nanodroplet infrared spectrum of this species provides rather definitive support to the previously suggested vaporization mechanism of ionic liquids. [emim][Tf_2N] is defined as 1-ethyl-3-methylimidazolium[bis(trifluoromethylsulfonyl)imide] Armstrong, J.P.; Hurst, C.; Jones, R. G.; Licence, P.; Lovelock, K. R. J.; Satterley, C. J.; Villar-Garcia, I. J. Physical Chemistry Chemical Physics 2007, 9, 982. Strasser, D.; Goulay, F.; Belau, L.; Kostko, O.; Koh, C.; Chambreau, S. D.; Vaghjiani, G. L.; Ahmed, M.; Leone, S. R. Journal of Physical Chemistry A 2010, 114, 879. Strasser, D.; Goulay, F.; Kelkar, M. S.; Maginn, E. J.; Leone, S. R. Journal of Physical Chemistry A 2007, 111, 3191. Chambreau, S. D.; Vaghjiani, G. L.; To, A.; Koh, C.; Strasser, D.; Kostko, O.; Leone, S. R. Journal of Physical Chemistry B 2010, 114, 1361. Maginn, E. J.; Kelkar, M. S. Journal of Physical Chemistry B 2007, 111, 9424.

  14. Improved operation of graded-channel SOI nMOSFETs down to liquid helium temperature

    NASA Astrophysics Data System (ADS)

    Pavanello, Marcelo Antonio; de Souza, Michelly; Ribeiro, Thales Augusto; Martino, João Antonio; Flandre, Denis

    2016-11-01

    This paper presents the operation of Graded-Channel (GC) Silicon-On-Insulator (SOI) nMOSFETs at low temperatures down to liquid helium temperature in comparison to standard uniformly doped transistors. Devices from two different technologies have been measured and show that the mobility increase rate with temperature for GC SOI transistors is similar to uniformly doped devices for temperatures down to 90 K. However, at liquid helium temperature the rate of mobility increase is larger in GC SOI than in standard devices because of the different mobility scattering mechanisms. The analog properties of GC SOI devices have been investigated down to 4.16 K and show that because of its better transconductance and output conductance, an intrinsic voltage gain improvement with temperature is also obtained for devices in the whole studied temperature range. GC devices are also capable of reducing the impact ionization due to the high electric field in the drain region, increasing the drain breakdown voltage of fully-depleted SOI MOSFETs at any studied temperature and the kink voltage at 4.16 K.

  15. Main components and performances of the IMGC calibration facilities for liquid helium flow rate measurements

    NASA Astrophysics Data System (ADS)

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

    Within the framework of a National Project on superconductivity two facilities have been designed and built at the Istituto di Metrologia 'G. Colonnetti' (IMGC) with the purpose of studying and calibrating liquid helium flowmeters in the range 1-20 g s -1 of liquid helium (LHe). After a brief description of these set-ups, this Paper examines in detail the solutions adopted in the design of the main calibration facility, particularly with regard to the circulating pump and the submerged driving motor. The latter has been devised for working only at LHe temperature, having an a.c. three-phase stator winding made of thin superconducting wire. The construction characteristics and operation conditions are discussed. As a flow rate reference, a new turbine flowmeter with its rotor magnetically suspended by the Meissner effect (described in another paper presented at the workshop), is used. A LHe flow rate transducer, based upon the measurement of the transit time of short thermal pulses, has been designed and tested with these facilities: the good results obtained using commercial low cost diodes as ΔT sensors are reported.

  16. Fatigue crack growth properties of a cryogenic structural steel at liquid helium temperature

    SciTech Connect

    Konosu, Shinji; Kishiro, Tomohiro; Ivano, O.; Nunoya, Yoshihiko; Nakajima, Hideo; Tsuji, Hiroshi

    1996-01-01

    The structural materials of the coils of superconducting magnets utilized in thermonuclear fusion reactors are used at liquid helium (4.2 K) temperatures and are subjected to repeated thermal stresses and electromagnetic forces. A high strength, high toughness austenitic stainless steel (12Cr-12Ni-10Mn-5Mo-0.2N) has recently been developed for large, thick-walled components used in such environments. This material is non-magnetic even when subjected to processing and, because it is a forging material, it is advantageous as a structural material for large components. In the current research, a large forging of 12Cr-12Ni-10Mn-5Mo-0.2N austenitic stainless steel, was fabricated to a thickness of 250 mm, which is typical of section thicknesses encountered in actual equipment. The tensile fatigue crack growth properties of the forging were examined at liquid helium temperature as a function of specimen location across the thickness of the forging. There was virtually no evidence of variation in tensile strength or fatigue crack growth properties attributable to different sampling locations in the thickness direction and no effect of thickness due to the forging or solution treatment associated with large forgings was observed.

  17. Effect of heat treatment in atmosphere on mechanical properties of pure titanium at liquid helium temperature

    SciTech Connect

    Konosu, S.; Nakaniwa, T.; Ivano, O.

    1998-05-12

    Due to their extreme friability, nuclear fusion superconductivity coil materials (NbTi, Nb{sub 3}Sn, Nb{sub 3}Al) are placed in pure titanium rectangular parallelepiped sleeves called conduits, of about 1 mm in wall thickness, and subjected to sintering heat treatment (50 to 200 hours at 923 to 1,023K) to produce superconductive materials. In use, the superconductive coil is immersed in liquid helium (4.2K) and as immense currents flow through the coil, the conduit is subjected to very large electromagnetic forces. As pure titanium is a highly active material, oxided scale forms on the surface when it is heated to high temperatures under atmospheric conditions, together with the formation, beneath the oxided scale, of an oxygen-rich layer possessing intense oxygen solubility. While oxided scale, because of its ability to reduce hydrogen absorption, is being actively used as a means to prevent the hydrogen embrittlement of titanium, it is believed that this leads to a deterioration of the mechanical properties because the oxygen-rich layer is deficient in ductility. The current research is intended to clarify the effect on the tensile test properties at liquid helium temperature (4.2K) of pure titanium and the oxygen-rich layer which forms thereon as a result of the heat treatment under atmospheric conditions.

  18. Emergency relief venting of the infrared telescope liquid helium dewar, second edition

    NASA Astrophysics Data System (ADS)

    Urban, E. W.

    1981-04-01

    An updated analysis is made of the emergency relief venting of the liquid helium dewar of the Spacelab 2 Infrared Telescope experiment in the event of a massive failure of the dewar guard vacuum. Such a failure, resulting from a major accident, could cause rapid heating and pressurization of the liquid helium in the dewar and lead to relief venting through the emergency relief system. The heat input from an accident is estimated for various fluid conditions in the dewar and the relief process considered as it takes place through one or both of the emergency relief paths. It was previously assumed that the burst diaphragms in the dewar relief paths would rupture at a pressure of 65 psi differential or 4.4 atmospheres. In fact, it has proved necessary to use burst diaphragms in the dewar which rupture at 115 psid or 7.8 atmospheres. An analysis of this case was carried out and shows that when the high pressure diaphragm rupture occurs, the dewar pressure falls within 8 s to below the 4.4 atmospheres for which the original analysis was performed, and thereafter it remains below that level.

  19. Emergency relief venting of the infrared telescope liquid helium dewar, second edition

    NASA Technical Reports Server (NTRS)

    Urban, E. W.

    1981-01-01

    An updated analysis is made of the emergency relief venting of the liquid helium dewar of the Spacelab 2 Infrared Telescope experiment in the event of a massive failure of the dewar guard vacuum. Such a failure, resulting from a major accident, could cause rapid heating and pressurization of the liquid helium in the dewar and lead to relief venting through the emergency relief system. The heat input from an accident is estimated for various fluid conditions in the dewar and the relief process considered as it takes place through one or both of the emergency relief paths. It was previously assumed that the burst diaphragms in the dewar relief paths would rupture at a pressure of 65 psi differential or 4.4 atmospheres. In fact, it has proved necessary to use burst diaphragms in the dewar which rupture at 115 psid or 7.8 atmospheres. An analysis of this case was carried out and shows that when the high pressure diaphragm rupture occurs, the dewar pressure falls within 8 s to below the 4.4 atmospheres for which the original analysis was performed, and thereafter it remains below that level.

  20. Design of 12-T Yin-Yang magnets operating in subcooled, superfluid helium. [Nb-Ti and Nb/sub 3/Sn

    SciTech Connect

    Cornish, D.N.; Hoard, R.W.; Baldi, R.

    1981-10-09

    A conceptual design study of a large 12-T yin-yang pair of coils, typical of the plug coils envisioned for a tandem-mirror facility to follow MFTF, has been completed. Because of its larger size and field strength, the magnetic forces are much greater than those experienced on MFTF. The main purpose of this study, therefore, is to assess the feasibility of such a device, paying particular attention to mechanical stress and conductor strain. The conductor proposed operates at 15.6 kA and consists of a rectangular half-hard copper stabilizer with a Nb-Ti insert in the low-field regions and Nb/sub 3/Sn in the high field. The coil is divided into four sections in the longitudinal direction, with steel substructure to limit the winding stress to an acceptable level. The conductor is cryostatically stabilized in superfluid He at 1.8K and 1.2 atm, with an operating heat flux of 0.8 W.cm/sup -2/.

  1. Superfluidity in ultracold gases

    NASA Astrophysics Data System (ADS)

    Campbell, Gretchen

    2016-05-01

    The study of superfluidity has a long and rich history. In Bose-Einstein condensate, superfluidity gives rise to a number of interesting effects, including quantized vortices and persistent currents. In this seminar I will give an introduction to superfluidity in ultracold atoms, including a discussion of the critical velocity and the spectrum of elementary excitations in superfluid systems.

  2. Critical flow and dissipation in a quasi–one-dimensional superfluid

    PubMed Central

    Duc, Pierre-François; Savard, Michel; Petrescu, Matei; Rosenow, Bernd; Del Maestro, Adrian; Gervais, Guillaume

    2015-01-01

    In one of the most celebrated examples of the theory of universal critical phenomena, the phase transition to the superfluid state of 4He belongs to the same three-dimensional (3D) O(2) universality class as the onset of ferromagnetism in a lattice of classical spins with XY symmetry. Below the transition, the superfluid density ρs and superfluid velocity vs increase as a power law of temperature described by a universal critical exponent that is constrained to be identical by scale invariance. As the dimensionality is reduced toward 1D, it is expected that enhanced thermal and quantum fluctuations preclude long-range order, thereby inhibiting superfluidity. We have measured the flow rate of liquid helium and deduced its superfluid velocity in a capillary flow experiment occurring in single 30-nm-long nanopores with radii ranging down from 20 to 3 nm. As the pore size is reduced toward the 1D limit, we observe the following: (i) a suppression of the pressure dependence of the superfluid velocity; (ii) a temperature dependence of vs that surprisingly can be well-fitted by a power law with a single exponent over a broad range of temperatures; and (iii) decreasing critical velocities as a function of decreasing radius for channel sizes below R ≃ 20 nm, in stark contrast with what is observed in micrometer-sized channels. We interpret these deviations from bulk behavior as signaling the crossover to a quasi-1D state, whereby the size of a critical topological defect is cut off by the channel radius. PMID:26601177

  3. Theoretical framework for thin film superfluid optomechanics: towards the quantum regime

    NASA Astrophysics Data System (ADS)

    Baker, Christopher G.; Harris, Glen I.; McAuslan, David L.; Sachkou, Yauhen; He, Xin; Bowen, Warwick P.

    2016-12-01

    Excitations in superfluid helium represent attractive mechanical degrees of freedom for cavity optomechanics schemes. Here we numerically and analytically investigate the properties of optomechanical resonators formed by thin films of superfluid 4He covering micrometer-scale whispering gallery mode cavities. We predict that through proper optimization of the interaction between film and optical field, large optomechanical coupling rates {g}0> 2π × 100 {kHz} and single photon cooperativities {C}0> 10 are achievable. Our analytical model reveals the unconventional behaviour of these thin films, such as thicker and heavier films exhibiting smaller effective mass and larger zero point motion. The optomechanical system outlined here provides access to unusual regimes such as {g}0> {{{Ω }}}M and opens the prospect of laser cooling a liquid into its quantum ground state.

  4. Electronic absorption spectroscopy of PAHs in supersonic jets and ultracold liquid helium droplets

    NASA Astrophysics Data System (ADS)

    Huisken, Friedrich; Staicu, Angela; Krasnokutski, Serge; Henning, Thomas

    Neutral and cationic polycyclic aromatic hydrocarbons (PAHs) are discussed as possible carriers of the diffuse interstellar bands (DIBs), still unassigned astrophysical absorption features observed in the spectra of reddened stars (Salama et al. 1999). Despite the importance of this class of molecules for astrophysics and nanophysics (PAHs can be regarded as nanoscale fragments of a sheet of graphite), the spectroscopic characterization of PAHs under well-defined conditions (low temperature and collision-free environment) has remained a challenge. Recently we have set up a cavity ring-down spectrometer combined with a pulsed supersonic jet expansion to study neutral and cationic PAHs under astrophysical conditions. PAHs studied so far include the neutral molecules anthracene (Staicu et al. 2004) and pyrene (Rouillé et al. 2004) as well as the cationic species naphthalene+ and anthracene+ (Sukhorukov et al. 2004). Employing another molecular beam apparatus, the same molecules (except of the cationic species) were also studied in liquid helium droplets (Krasnokutski et al. 2005, Rouillé et al. 2004). This novel technique combines several advantages of conventional matrix spectroscopy with those of gas phase spectroscopy. Notable advantages are the possibility to study molecules with low vapor pressure and to use a mass spectrometer facilitating spectral assignments. The most recent studies were devoted to phenanthrene and the more complicated (2,3)-benzofluorene. These molecules were investigated in the gas phase by cavity ring-down spectroscopy and in liquid helium droplets using depletion spectroscopy. For benzofluorene the present studies constitute the first reported measurements both in the gas phase and in helium droplets. The origin of the S1 ← S0 gas phase transition could be located at 29 894.3 cm-1, and a series of vibronic bands was recorded below 31 500 cm-1. In contrast to previously studied PAHs, the shift induced by the helium droplets was very

  5. Nucleation of Quantized Vortices from Rotating Superfluid Drops

    NASA Technical Reports Server (NTRS)

    Donnelly, Russell J.

    2001-01-01

    The long-term goal of this project is to study the nucleation of quantized vortices in helium II by investigating the behavior of rotating droplets of helium II in a reduced gravity environment. The objective of this ground-based research grant was to develop new experimental techniques to aid in accomplishing that goal. The development of an electrostatic levitator for superfluid helium, described below, and the successful suspension of charged superfluid drops in modest electric fields was the primary focus of this work. Other key technologies of general low temperature use were developed and are also discussed.

  6. Superfluid Black Holes

    NASA Astrophysics Data System (ADS)

    Hennigar, Robie A.; Mann, Robert B.; Tjoa, Erickson

    2017-01-01

    We present what we believe is the first example of a "λ -line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid 4He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

  7. Superfluid Black Holes.

    PubMed

    Hennigar, Robie A; Mann, Robert B; Tjoa, Erickson

    2017-01-13

    We present what we believe is the first example of a "λ-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid ^{4}He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.

  8. Transition from a 2D Degenerate Bose Liquid to 3D Superfluid in 4He Films Formed in Nanopores

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Hieda, Mitsunori; Toda, Ryo; Inagaki, Shinji; Wada, Nobuo

    2017-10-01

    The phase transition mechanism in a new dimensional condition was studied for the 4He film formed in 3D nanopore where pores of 2.7 nm diameter are connected in 3D with a period of 5.5 nm. In the case of a very low superfluid onset temperature TSF at a low coverage, a sharp and large peak of the specific heat indicates the typical 3D transition of the 4He film. This is understood by comparing the relative lengths among the 3D and 2D mean atomic distances and the 3D connection length of the film. When the coverage is increased, these length relations are changed to a new dimensional condition. We observed a sharp peak at TSF of the 3D transition up to 1.1 K. For a thick film, we also observed a hump at TB, which is higher than TSF. The hump is attributed to a phase change to a 2D degenerate state with a finite amplitude but without a long range order in the phase of superfluid order parameters. This indicates a new type of transition at TSF from the 2D degenerate state to the 3D superfluid, which is essentially different from the Kosterlitz-Thouless transition.

  9. Experimental Studies of the Growth Kinetics of Methane Clathrate Hydrates & Superfluid Hydrodynamics on the Nanoscale

    NASA Astrophysics Data System (ADS)

    Botimer, Jeffrey David

    This thesis details the experimental findings of three distinct research projects. The first studies the growth kinetics of methane clathrate hydrates grown under the influence of multiple factors including surfactants, porous media, substrate wetting properties, and salt content. The second investigates the flow behaviors of superfluid helium through single, high aspect ratio nanopipes. The third models the frequency response of a quartz tuning fork in high pressure normal and superfluid helium and demonstrates how quartz tuning forks can be used as cheap, small, in situ, cryogenic pressure gauges. The first project reports studies of the kinetics of growth of methane hydrates from liquid water containing small amounts of surfactant (<500 ppm of sodium dodecyl sulfate, SDS). The kinetics are monitored using simultaneous measurements of the uptake of methane detected by a pressure drop in the gas phase, and either visual observations of the amount of liquid water and solid phase in the reaction vessel, or in situ micro-Raman measurements or in situ NMR measurements. These diagnostics show that the uptake of methane and the conversion of liquid water to a solid phase do not occur simultaneously; the uptake of gas always lags the visual and spectroscopic signatures of the disappearance of liquid water and the formation of solid. The evidence suggests that the SDS causes water to form an intermediate immobile solid-like state before combining with the methane to form hydrate. The growth mechanism is related to the surfactant and disappears for low SDS concentrations (<25 ppm). Also reported are studies of the growth rates of methane hydrates as a function of substrate wetting properties, driving force, and growth media. The second project studies pressure driven flow of superfluid helium through single high aspect ratio glass nanopipes into a vacuum has been studied for a wide range of pressure drop (0--30 atm), reservoir temperature (0.8--2.5K), pipe lengths (1-30mm

  10. Two phase liquid helium flow testing to simulate the operation of a cryocondensation pump in the DIII-D tokamak

    SciTech Connect

    Laughon, G.J.; Baxi, C.B.; Campbell, G.L.; Mahdavi, M.A.; Makariou, C.C.; Smith, J.P.; Schaffer, M.J.; Schaubel, K.M.; Menon, M.M.

    1994-06-01

    A liquid helium-cooled cryocondensation pump has been installed in the DIII-D tokamak fusion energy research experiment at General Atomics. The pump is located within the tokamak vacuum chamber beneath the divertor baffle plates and is utilized for plasma density and contamination control. Two-phase helium flows through the pump at 5 to 10 g/s utilizing the heat transfer and constant temperature characteristics of boiling liquid . helium. The pump is designed for a pumping speed of 32,000 1/s. Extensive testing was performed with a prototypical pump test fixture. Several pump geometries (simple tube, coaxial flow plug, and coaxial slotted insert) were tested, in an iterative process, to determine which was the most satisfactory for stable cryocondensation pumping. Results from the different tests illustrating the temperature distribution and flow characteristics for each configuration are presented.

  11. Testing the Effects of Helium Pressurant on Thermodynamic Vent System Performance with Liquid Hydrogen

    NASA Astrophysics Data System (ADS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S. L.; Tucker, S.

    2008-03-01

    In support of the development of a micro-gravity pressure control capability for liquid hydrogen, testing was conducted at the Marshall Space Flight Center (MSFC) with the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the effects of helium pressurant on the performance of a spray-bar thermodynamic vent system (TVS). The testing, with an ambient heat leak of about 70 W and tank fill levels of 90, 50, and 25%, was performed for 14 days during August and September 2005. The TVS successfully controlled the tank pressure within a ±3.45 kPa band with various gaseous helium (GHe) masses in the ullage. Relative to pressure control with an "all hydrogen" ullage, the GHe presence resulted in 37 to 68% longer pressure reduction cycle durations, depending on the fill level, during the mixing/venting phase of the control cycle. Testing was also conducted to evaluate thermodynamic venting without the recirculation pump operating, at a very low fill level. Although ullage stratification was present, the ullage pressure was successfully controlled without the pump. It was evident that the spray-bar and heat exchanger configuration, which extended almost the entire length of the tank, enabled significant thermal energy removal from the ullage even without the pump operating.

  12. Integration of a Cryocooler into a SQUID Magnetospinography System for Reduction of Liquid Helium Consumption

    NASA Astrophysics Data System (ADS)

    Adachi, Yoshiaki; Oyama, Daisuke; Kawai, Jun; Ogata, Hisanao; Uehara, Gen

    We are currently developing a magnetospinography (MSG) system for noninvasive functional imaging of the spinal cord. The MSG system is a device for observing a weak magnetic field accompanied by the neural activity of the spinal cord by using an array of low-temperature superconducting quantum interference device (SQUID) magnetic flux sensors. As in the case of other biomagnetic measurement systems such as the magnetoencephalography (MEG) system, the running cost of the MSG system is mainly dependent on the liquid helium (LHe) consumption of a dewar vessel. We integrated a cryocooler into the MSG system to reduce LHe consumption. A pulse tube cryocooler with a cooling power of 0.5Wat 4 K was placed adjacent to a magnetically shielded room and was directly connected to the thermal radiation shield of the dewar by an electrically isolated transfer tube. Cold helium gas was circulated between the cryocooler and the radiation shield. Consequently, the temperature of the radiation shield decreased below 40 K. Previous studies have shown that the detection of a weak magnetic field is often hindered by severe low-frequency band noise from the cryocooler. However, the band of the MSG signals is much higher than that of the cryocooler noise. Therefore, the noise can be filtered out and has a less detrimental effect on MSG measurement than on other biomagnetic field measurements such as MEG measurement. As a result, LHe consumption was reduced by 46%, with no increase in the noise floor.

  13. Characterisation and optimisation of flexible transfer lines for liquid helium. Part II: Thermohydraulic modelling

    NASA Astrophysics Data System (ADS)

    Dittmar, N.; Haberstroh, Ch.; Hesse, U.; Krzyzowski, M.

    2016-10-01

    In part one of this publication experimental results for a single-channel transfer line used at liquid helium (LHe) decant stations are presented. The transfer of LHe into mobile dewars is an unavoidable process since the places of storage and usage are generally located apart from each other. The experimental results have shown that reasonable amounts of LHe evaporate due to heat leak and pressure drop. Thus, generated helium cold gas has to be collected and reliquefied, demanding a huge amount of electrical energy. Although this transfer process is common in cryogenic laboratories, no existing code could be found to model it. Therefore, a thermohydraulic model has been developed to model the LHe flow at operating conditions using published heat transfer and pressure drop correlations. This paper covers the basic equations used to calculate heat transfer and pressure drop, as well as the validation of the thermohydraulic code, and its application within the optimisation process. The final transfer line design features reduced heat leak and pressure drop values based on a combined measurement and modelling campaign in the range of 0.112 < pin < 0.148 MPa, 190 < G < 450 kg/(m2 s), and 0.04 < xout < 0.12.

  14. Infrared absorptivities of transition metals at room and liquid-helium temperatures.

    NASA Technical Reports Server (NTRS)

    Jones, M. C.; Palmer, D. C.; Tien, C. L.

    1972-01-01

    Evaluation of experimental data concerning the normal spectral absorptivities of the transition metals, nickel, iron, platinum, and chromium, at both room and liquid-helium temperatures in the wavelength range from 2.5 to 50 microns. The absorptivities were derived from reflectivity measurements made relative to a room-temperature vapor-deposited gold reference mirror. The absorptivity of the gold reference mirror was measured calorimetrically, by use of infrared laser sources. Investigation of various methods of sample-surface preparation resulted in the choice of a vacuum-annealing process as the final stage. The experimental results are discussed on the basis of the anomalous-skin-effect theory modified for multiple conduction bands. As predicted, the results approach a single-band model toward the longer wavelengths. Agreement between theory and experiment is considerably improved by taking into account the modification of the relaxation time due to the photon-electron-phonon interaction proposed by Holstein (1954) and Gurzhi (1958); but, particularly at helium temperatures, the calculated curve is consistently below the experimental results.

  15. Saturation region of helium ionization detector for gas-solid and gas-liquid chromatography

    SciTech Connect

    Andrawes, F.F.; Brazell, R.S.; Gibson, E.K.

    1980-05-01

    In the saturation region of the helium detector field intensity, the detector response is independent of the electrical field. In this region (at applied potential between 200 to 2000 volts per centimeter of electrode surface) the detector is operated at a low background current, and a low noise level, but it still exhibits a stable and sensitive response. The detector in this region can be operated with high purity grade helium without any further elaborate purification processes to yield a positive response to all compounds and gases tested. The operation of the detector in this mode has been adapted to both gas-solid and gas-liquid chromatography, with temperature programming. A sample can be introduced to the column via a gas sampling injection valve or via a syringe by direct injection into a modified injection port. The detector response is linear over a range of 10/sup 6/ units with a detection limit in the picogram range for organic compounds. 11 figures.

  16. Thermodynamic Vent System Performance Testing with Subcooled Liquid Methane and Gaseous Helium Pressurant

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S. L.; Tucker, S. P.

    2007-01-01

    Due to its high specific impulse and favorable thermal properties for storage, liquid methane (LCH4) is being considered as a candidate propellant for exploration architectures. In order to gain an -understanding of any unique considerations involving micro-gravity pressure control with LCH4, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the performance of a spray-bar thermodynamic vent system (TVS) with subcooled LCH4 and gaseous helium (GHe) pressurant. Thirteen days of testing were performed in November 2006, with total tank heat leak conditions of about 715 W and 420 W at a fill level of approximately 90%. The TVS system was used to subcool the LCH4 to a liquid saturation pressure of approximately 55.2 kPa before the tank was pressurized with GHe to a total pressure of 165.5 kPa. A total of 23 TVS cycles were completed. The TVS successfully controlled the ullage pressure within a prescribed control band but did not maintain a stable liquid saturation pressure. This was likely. due to a TVS design not optimized for this particular propellant and test conditions, and possibly due to a large artificially induced heat input directly into the liquid. The capability to reduce liquid saturation pressure as well as maintain it within a prescribed control band, demonstrated that the TVS could be used to seek and maintain a desired liquid inlet temperature for an engine (at a cost of propellant lost through the TVS vent). One special test was conducted at the conclusion of the planned test activities. Reduction of the tank ullage pressure by opening the Joule-Thomson valve (JT) without operating the pump was attempted. The JT remained open for over 9300 seconds, resulting in an ullage pressure reduction of 30 kPa. The special test demonstrated the feasibility of using the JT valve for limited ullage pressure reduction in the event of a pump failure.

  17. Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

    DOE PAGES

    Vanhille, Christian; Pantea, Cristian; Sinha, Dipen N.

    2017-01-01

    In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium couldmore » be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.« less

  18. Gas propagation in a liquid helium cooled vacuum tube following a sudden vacuum loss

    NASA Astrophysics Data System (ADS)

    Dhuley, Ram C.

    This dissertation describes the propagation of near atmospheric nitrogen gas that rushes into a liquid helium cooled vacuum tube after the tube suddenly loses vacuum. The loss-of-vacuum scenario resembles accidental venting of atmospheric air to the beam-line of a superconducting radio frequency particle accelerator and is investigated to understand how in the presence of condensation, the in-flowing air will propagate in such geometry. In a series of controlled experiments, room temperature nitrogen gas (a substitute for air) at a variety of mass flow rates was vented to a high vacuum tube immersed in a bath of liquid helium. Pressure probes and thermometers installed on the tube along its length measured respectively the tube pressure and tube wall temperature rise due to gas flooding and condensation. At high mass in-flow rates a gas front propagated down the vacuum tube but with a continuously decreasing speed. Regression analysis of the measured front arrival times indicates that the speed decreases nearly exponentially with the travel length. At low enough mass in-flow rates, no front propagated in the vacuum tube. Instead, the in-flowing gas steadily condensed over a short section of the tube near its entrance and the front appeared to `freeze-out'. An analytical expression is derived for gas front propagation speed in a vacuum tube in the presence of condensation. The analytical model qualitatively explains the front deceleration and flow freeze-out. The model is then simplified and supplemented with condensation heat/mass transfer data to again find the front to decelerate exponentially while going away from the tube entrance. Within the experimental and procedural uncertainty, the exponential decay length-scales obtained from the front arrival time regression and from the simplified model agree.

  19. Copper dimer interactions on a thermomechanical superfluid {sup 4}He fountain

    SciTech Connect

    Popov, Evgeny; Eloranta, Jussi

    2015-05-28

    Laser induced fluorescence imaging and frequency domain excitation spectroscopy of the copper dimer (B{sup 1}Σ{sub g}{sup +}←X{sup 1}Σ{sub u}{sup +}) in thermomechanical helium fountain at 1.7 K are demonstrated. The dimers penetrate into the fountain provided that their average propagation velocity is ca. 15 m/s. This energy threshold is interpreted in terms of an imperfect fountain liquid-gas interface, which acts as a trap for low velocity dimers. Orsay-Trento density functional theory calculations for superfluid {sup 4}He are used to characterize the dynamics of the dimer solvation process into the fountain. The dimers first accelerate towards the fountain surface and once the surface layer is crossed, they penetrate into the liquid and further slow down to Landau critical velocity by creating a vortex ring. Theoretical lineshape calculations support the assignment of the experimentally observed bands to Cu{sub 2} solvated in the bulk liquid. The vibronic progressions are decomposed of a zero-phonon line and two types of phonon bands, which correlate with solvent cavity interface compression (t < 200 fs) and expansion (200 < t < 500 fs) driven by the electronic excitation. The presented experimental method allows to perform molecular spectroscopy in bulk superfluid helium where the temperature and pressure can be varied.

  20. Soft or hard ionization of molecules in helium nanodroplets? An electron impact investigation of alcohols and ethers.

    PubMed

    Yang, Shengfu; Brereton, Scott M; Wheeler, Martyn D; Ellis, Andrew M

    2005-12-21

    Electron impact (70 eV) mass spectra of a series of C1-C6 alcohols encased in large superfluid liquid helium nanodroplets (approximately 60,000 helium atoms) have been recorded. The presence of helium alters the fragmentation patterns when compared with the gas phase, with some ion product channels being more strongly affected than others, most notably cleavage of the C(alpha)-H bond in the parent ion to form the corresponding oxonium ion. Parent ion intensities are also enhanced by the helium, but only for the two cyclic alcohols studied, cyclopentanol and cyclohexanol, is this effect large enough to transform the parent ion from a minor product (in the gas phase) into the most abundant ion in the helium droplet experiments. To demonstrate that these findings are not unique to alcohols, we have also investigated several ethers. The results obtained for both alcohols and ethers are difficult to explain solely by rapid cooling of the excited parent ions by the surrounding superfluid helium, although this undoubtedly takes place. A second factor also seems to be involved, a cage effect which favors hydrogen atom loss over other fragmentation channels. The set of molecules explored in this work suggest that electron impact ionization of doped helium nanodroplets does not provide a sufficiently large softening effect to be useful in analytical mass spectrometry.

  1. Hydrogen-Free Liquid-Helium Recovery Plants: The Solution for Low-Temperature Flow Impedance Blocking

    NASA Astrophysics Data System (ADS)

    Gabal, M.; Arauzo, A.; Camón, A.; Castrillo, M.; Guerrero, E.; Lozano, M. P.; Pina, M. P.; Sesé, J.; Spagna, S.; Diederichs, J.; Rayner, G.; Sloan, J.; Galli, F.; van der Geest, W.; Haberstroh, C.; Dittmar, N.; Oca, A.; Grau, F.; Fernandes, A.; Rillo, C.

    2016-08-01

    The blocking of fine-capillary tubes used as flow impedances in 4H3 evaporation cryostats to achieve temperatures below 4.2 K is generally attributed to nitrogen or air impurities entering these tubes from the main bath. The failure of even the most rigorous low-temperature laboratory best practices aimed at eliminating the problem by maintaining the cleanliness of the helium bath and preventing impurities from entering the capillary tubes suggests that a different cause is responsible for the inexplicable reduction of impedance flow. Many low-temperature research laboratories around the world have suffered this nuisance at a considerable financial cost due to the fact that the affected systems have to be warmed to room temperature in order to recover their normal low-temperature operation performance. Here, we propose an underlying physical mechanism responsible for the blockages based upon the freezing of molecular H2 traces present in the liquid-helium bath. Solid H2 accumulates at the impedance low-pressure side, and, after some time, it produces a total impedance blockage. The presence of H2 traces is unavoidable due its occurrence in the natural gas wells where helium is harvested, forcing gas suppliers to specify a lower bound for impurity levels at about 100 ppb even in high-grade helium. In this paper, we present a simple apparatus to detect hydrogen traces present in liquid helium and easily check the quality of the liquid. Finally, we propose a solution to eliminate the hydrogen impurities in small- and large-scale helium recovery plants. The solution has been implemented in several laboratories that previously experienced a chronic occurrence of blocking, eliminating similar occurrences for more than one year.

  2. Observation of thermal fluctuations in a superfluid optomechanical system

    NASA Astrophysics Data System (ADS)

    Kashkanova, A. D.; Shkarin, A. B.; Brown, C. D.; Flowers-Jacobs, N. E.; Childress, L.; Hoch, S. W.; Hohmann, L.; Ott, K.; Garcia, S.; Reichel, J.; Harris, J. G. E.

    2017-02-01

    In cavity optomechanics the state of a mechanical element can be manipulated by interfacing it with light via radiation pressure, electrostriction, or related phenomena. The majority of mechanical elements employed in optomechanical systems to date are solid objects (membranes, nanowires, mirrors, etc); however fluids can also be used as a mechanical element. Compared to solids, fluids have an advantage: they readily achieve precise alignment with the optical cavity, as the fluid can conformally fill or coat the optical cavity. However, almost all optomechanical systems need to be cooled to sub-Kelvin temperatures in order for quantum effects to be observed. Liquid helium is the only fluid that doesn't solidify under its own pressure at these temperatures. Additionally, helium has almost no optical absorption, high thermal conductivity and very low acoustic loss at cryogenic temperatures. We have developed an optomechanical system in which the mechanical mode is a standing density wave in superfluid helium inside a 70 μm long Fabry-Perot cavity. The optical mode is also a mode of the same cavity. Thus, the system is completely self-aligned. In this system, we used electrostriction to drive the mechanical mode with light by modulating the optical intensity. We also observed the mode's undriven Brownian motion and from that extracted it mean phonon number. We measured phonon number as low as nac=11. The optomechanical effects of optical spring and optical damping were observed, and agreed well with the predictions of conventional optomechanical theory.

  3. Helium cryogenics

    SciTech Connect

    Van Sciver, S.W.

    1986-01-01

    The goal of this work is to bridge the gap between physics and engineering aspects of helium fluids to encourage their use and enhance their usefulness in low-temperature systems. Topics covered include thermodynamic laws, electrical and thermal conductivities, spin systems, virial expansion, liquid He I, transport properties, density of helium as a quantum fluid, vortices and turbulence in He II, Kapitza conductance, acoustic mismatch theory, nucleate boiling heta transfer, surface effects, general considerations of internal flow, ideal liquefaction, stirling cycle, and the helium-3 isotope.

  4. Motion of a helical vortex filament in superfluid 4He under the extrinsic form of the local induction approximation

    NASA Astrophysics Data System (ADS)

    Van Gorder, Robert A.

    2013-08-01

    Very recently, Shivamoggi ["Vortex motion in superfluid 4He: Reformulation in the extrinsic vortex-filament coordinate space," Phys. Rev. B 84, 012506 (2011)], 10.1103/PhysRevB.84.012506 studied the extrinsic form of the local induction approximation (LIA) for the motion of a Kelvin wave on a vortex filament in superfluid 4He, and obtained some results in a cubic approximation. Presently, we study the motion of helical vortex filaments in superfluid 4He under the exact fully nonlinear LIA considered in potential form by Van Gorder ["Fully nonlinear local induction equation describing the motion of a vortex filament in superfluid 4He," J. Fluid Mech. 707, 585 (2012)], 10.1017/jfm.2012.308 and obtained from the Biot-Savart law through the equations of Hall and Vinen ["The rotation of liquid helium II. I. Experiments on the propagation of second sound in uniformly rotating helium II," Proc. R. Soc. London, Ser. A 238, 204 (1956)], 10.1098/rspa.1956.0214 including superfluid friction terms. Nonlinear dispersion relations governing the helical Kelvin wave on such a vortex filament are derived in exact form, from which we may exactly calculate the phase and group velocity of the Kelvin wave. With this, we classify the motion of a helical Kelvin wave on a vortex filament under the LIA. The dispersion relations and results, which follow are exact in nature, in contrast to most results in the literature, which are usually numerical approximations. As such, our results accurately capture the qualitative behavior of the Kelvin waves under the LIA. Extensions to other frameworks are discussed.

  5. Numerical Studies of Properties of Confined Helium

    NASA Technical Reports Server (NTRS)

    Manousakis, Efstratios

    2003-01-01

    We carry out state of the art simulations of properties of confined liquid helium near the superfluid transition to a degree of accuracy which allows to make predictions for the outcome of fundamental physics experiments in microgravity. First we report our results for the finite-size scaling behavior of heat capacity of superfluids for cubic and parallel-plate geometry. This allows us to study the crossover from zero and two dimensions to three dimensions. Our calculated scaling functions are in good agreement with recently measured specific heat scaling functions for the above mentioned geometries. We also present our results of a quantum simulation of submonolayer of molecular hydrogen deposited on an ideal graphite substrate using path-integral quantum Monte Carlo simulation. We find that the monolayer phase diagram is rich and very similar to that of helium monolayer. We are able to uncover the main features of the complex monolayer phase diagram, such as the commensurate solid phases and the commensurate to incommensurate transition, in agreement with the experiments and to find some features which are missing from the experimental analysis.

  6. Electrical breakdown in helium cells at low temperature

    NASA Astrophysics Data System (ADS)

    Sethumadhavan, Bhaskar

    2007-05-01

    We have encountered a new phenomenon in the development of a prototype detector of solar neutrinos using liquid helium in which recoil electrons from neutrino scattering are to be detected by extracting them from the liquid and accelerating them in the vacuum by an electric field. In order to understand the possible constraints on such a particle detector using superfluid helium, we have studied the currents produced by a radioactive source in a helium cell having a liquid/vacuum interface at 100 mK. A number of phenomena have been observed that have not been described in the literature. These include the following. (1) The current at very low voltages, V ˜ 0, in a cell having a free surface can be up to 100 times greater than in a filled cell. (2) There is a large amplification of current in modest electric fields with a free surface present in the cell. (3) The amplification becomes sufficiently large such that a breakdown occurs at potential differences across the vacuum on the order of 1000 V. The results for a partially filled cell can be understood in terms of Penning ionization of excimers on the surface of the helium and the subsequent acceleration of electrons across the vacuum. Triplet excimers are created in the liquid by the radioactive source. These excimers propagate with a mean free path that is determined by scattering from 3He atoms and quasiparticles in the superfluid He. If an excimer reaches the surface, it is bound there but is free to move in the plane of the surface. Once bound to the surface these mobile excimers become distributed uniformly over all surfaces (bulk liquid and the film). They move about and annihilate in pairs through the Penning ionization process to create electrons and positive helium ions in the vacuum. An electron in the vacuum in the presence of an electric field is always destined to hit liquid helium, either the bulk liquid or the film on the top surface of the cell. If the energy of the electron is sufficient to

  7. Liquid Hydrogen Propellant Tank Sub-Surface Pressurization with Gaseous Helium

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Cartagena, W.

    2015-01-01

    A series of tests were conducted to evaluate the performance of a propellant tank pressurization system with the pressurant diffuser intentionally submerged beneath the surface of the liquid. Propellant tanks and pressurization systems are typically designed with the diffuser positioned to apply pressurant gas directly into the tank ullage space when the liquid propellant is settled. Space vehicles, and potentially propellant depots, may need to conduct tank pressurization operations in micro-gravity environments where the exact location of the liquid relative to the diffuser is not well understood. If the diffuser is positioned to supply pressurant gas directly to the tank ullage space when the propellant is settled, then it may become partially or completely submerged when the liquid becomes unsettled in a microgravity environment. In such case, the pressurization system performance will be adversely affected requiring additional pressurant mass and longer pressurization times. This series of tests compares and evaluates pressurization system performance using the conventional method of supplying pressurant gas directly to the propellant tank ullage, and then supplying pressurant gas beneath the liquid surface. The pressurization tests were conducted on the Engineering Development Unit (EDU) located at Test Stand 300 at NASA Marshall Space Flight Center (MSFC). EDU is a ground based Cryogenic Fluid Management (CFM) test article supported by Glenn Research Center (GRC) and MSFC. A 150 ft3 propellant tank was filled with liquid hydrogen (LH2). The pressurization system used regulated ambient helium (GHe) as a pressurant, a variable position valve to maintain flow rate, and two identical independent pressurant diffusers. The ullage diffuser was located in the forward end of the tank and was completely exposed to the tank ullage. The submerged diffuser was located in the aft end of the tank and was completely submerged when the tank liquid level was 10% or greater

  8. Long and high conductance helium heat pipe

    NASA Astrophysics Data System (ADS)

    Gully, Philippe

    2014-11-01

    This paper reports on the development and the thermal tests of two superfluid helium heat pipes. They feature a copper braid located inside a 6 mm outer diameter stainless tube fitted with copper ends for mechanical anchoring. The copper braid is the support of the Rollin superfluid helium film which is essential in the heat transfer. The extremely low thickness of the liquid film allows for a low filling pressure, making the technology very simple without the need for any external hot reservoir and with the possibility to easily bend the tube. We present the design and discuss the thermal performance of two heat pipes tested for several filling pressures, adverse tilt angles and in 1.4-2.0 K temperature range. A minimum filling pressure (0.6 MPa) is needed to get significant transport capacity. A 12 mW transport capacity is achieved for 3.0 MPa filling pressure. It is shown that the long heat pipe (1.2 m) and the short one (0.25 m) have similar thermal performance in adverse tilt. At 1.7 K the long heat pipe, 120 g in weight, reaches a transport capacity of 5.7 mW/4.2 mW for a tilt angle of 0 / 60° and a thermal conductance of 600 mW/K for 4 mW transferred power. When the condenser reaches the super-fluid transition temperature, the Rollin film accelerates the cool down of the evaporator down to 1.7 K with a heating power applied to the evaporator.

  9. Computation of the properties of liquid neon, methane, and gas helium at low temperature by the Feynman-Hibbs approach.

    PubMed

    Tchouar, N; Ould-Kaddour, F; Levesque, D

    2004-10-15

    The properties of liquid methane, liquid neon, and gas helium are calculated at low temperatures over a large range of pressure from the classical molecular-dynamics simulations. The molecular interactions are represented by the Lennard-Jones pair potentials supplemented by quantum corrections following the Feynman-Hibbs approach. The equations of state, diffusion, and shear viscosity coefficients are determined for neon at 45 K, helium at 80 K, and methane at 110 K. A comparison is made with the existing experimental data and for thermodynamical quantities, with results computed from quantum numerical simulations when they are available. The theoretical variation of the viscosity coefficient with pressure is in good agreement with the experimental data when the quantum corrections are taken into account, thus reducing considerably the 60% discrepancy between the simulations and experiments in the absence of these corrections.

  10. A high-resolution NMR probe in which the coil and preamplifier are cooled with liquid helium

    NASA Astrophysics Data System (ADS)

    Styles, P.; Soffe, N. F.; Scott, C. A.; Crag, D. A.; Row, F.; White, D. J.; White, P. C. J.

    In a well designed NMR spectrometer, the noise originates predominantly from the resistance of the receiver coil. Significant improvements in sensitivity can be achieved by cooling the coil to cryogenic temperatures, provided that a preamplifier can be designed to match the coil's performance. A probe is described in which the coil and preamplifier are cooled with liquid helium, but the sample is maintained at room temperature. Carbon-13 spectra at 45 MHz demonstrate improved sensitivity over conventional probes at the same field.

  11. Charged snowball in nonpolar liquid

    NASA Astrophysics Data System (ADS)

    Chikina, I.; Shikin, V.; Varlamov, A.

    2007-09-01

    The problem of correct definition of the charge carrier effective mass in superfluid helium is revised. It is demonstrated that the effective mass M of such a quasiparticle can be introduced without use of Atkins' idea concerning the solidification of liquid He in the close vicinity of an ion. The two-liquid scenario of the "snowball" mass formation is investigated. The normal fluid contribution to the total snowball effective mass, the physical causes of its singularity, and a way to do the corresponding regularization procedure are discussed. Within the two-liquid model, two different effective snowball radii exist: Rid for superfluid flow component and Rn for the normal one, Rn>Rid is demonstrated. Agreement of the theory with the available experimental data is found.

  12. Staircase pattern in a superfluid He-II torsional-oscillator analog of the radio-frequency SQUID

    SciTech Connect

    Bonaldi, M. ); Cerdonio, M.; Dolesi, R.; Vitale, S. Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Trento, Sezione di Padova, I-38050, Povo, Trento )

    1994-01-01

    We are developing a superfluid [sup 4]He analog of the rf SQUID. A thin partition with a micrometric orifice is placed inside a toroidal container filled with liquid helium; ac and dc superflows through the orifice are induced by rotating the whole torus, which is the inertial member of a torsional oscillator. The torus oscillation amplitude vs drive curve shows a small but reproducible staircase pattern, which is detectable between 1.4 and 2.05 K, but is not modulated by a superimposed steady rotation. We discuss this behavior in terms of the occurrence of multiple phase slips.

  13. Characteristics of a liquid-helium-free calibration apparatus for cryogenic thermometers

    SciTech Connect

    Shimazaki, T.

    2013-09-11

    Closed-cycle Joule-Thomson (JT) cryocoolers have been developed at National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) with the aim of realizing a liquid-helium-free calibration apparatus for cryogenic thermometers between 0.65 K and 25 K. The latest JT cryocooler at NMIJ/AIST consists of a {sup 3}He JT cooling circuit and a pulse tube mechanical refrigerator. The characteristics of the apparatus including a residual gas analysis of the JT cooling circuit are presented in this paper. Currently the initial cool-down is performed using a heat-exchange gas. It normally takes about 30 h to reduce the temperature from room temperature to 5 K at the thermometer comparison block of the apparatus. The correct timing of the removal of the heatexchange gas is important for the efficient operation of the apparatus. Incomplete removal of the heat-exchange gas induces excess heat load on the apparatus and thermal disturbances. Some examples of abrupt temperature bursts are discussed in this paper. Mechanical refrigerators generate cyclic mechanical vibrations, and precision resistance thermometers are usually very sensitive to a mechanical vibration. The measured vibration level of the developed apparatus is reported. The damage to the apparatus due to the magnitude 9.0 earthquake on March 11, 2011, and possible countermeasures in the case of future earthquakes are also discussed.

  14. Infrared-absorption spectrum of the electron bubble in liquid helium

    NASA Astrophysics Data System (ADS)

    Grimes, C. C.; Adams, G.

    1992-02-01

    The energy of the electronic transition from the ground state to the first excited state in the electron bubble in liquid helium has been measured by direct infrared absorption at pressures from zero to the solidification pressure and at temperatures from 1.3 to 4.2 K. At 1.3 K the 1s-1p splitting varies from 0.102 eV at P=0 to 0.227 eV at P=25 atm. At intermediate pressures a simple spherical-square-well model calculation fits the measured splittings within a few percent if the surface tension is taken to be independent of pressure. This model, when extended to allow for dilation and elongation of bubbles trapped on vorticity and dilation of rapidly drifting bubbles, agrees well with the observed transition energies at all pressures. The measured linewidths are larger by at least a factor of 2 than those calculated, which may indicate heating of rapidly drifting bubbles.

  15. Mapping of Ambient Magnetic Fields within Liquid Helium Dewar for Testing of a DC SQUID Magnetometer

    SciTech Connect

    Newhouse, Randal

    2003-09-05

    In an effort to explore the cavity lights phenomenon, Experimental Facilities Department at SLAC is testing a DC SQUID magnetometer. Due to the nature of the SQUID magnetometer and the intended tests, the earth's magnetic field must be negated. It is proposed to reduce ambient fields using bucking coils. First, however, an accurate map of the magnetic field inside the liquid helium Dewar where the experiment is going to take place needed to be made. This map was made using a three-axis fluxgate magnetometer mounted on a 3D positioning device made for this purpose. A ten inch tall volume within the Dewar was measured at data points approximately an inch from each other in all three axes. A LabVEIW program took readings from the magnetometer at 2 ms intervals for 1000 readings in such a way as to eliminate any ambient 60 Hz signals that may be present in the data. This data was stored in spreadsheet format and was analyzed to determine how the magnetic field within the Dewar was changing as a function of position.

  16. Towards liquid-helium-free, persistent-mode MgB2 MRI magnets: FBML experience

    NASA Astrophysics Data System (ADS)

    Iwasa, Yukikazu

    2017-05-01

    In this article I present our experience at the Magnet Technology Division of the MIT Francis Bitter Magnet Laboratory on liquid-helium (LHe)-free, persistent-mode MgB2 MRI magnets. Before reporting on our MgB2 magnets, I first summarize the basic work that we began in the late 1990s to develop LHe-free, high-temperature superconductor (HTS) magnets cooled in solid cryogen—I begin by discussing the enabling feature, particularly of solid nitrogen (SN2), for adiabatic HTS magnets. The next topic is our first LHe-free, SN2-HTS magnet, for which we chose Bi2223 because in the late 1990s Bi2223 was the only HTS available to build an HTS magnet. I then move on to two MgB2 magnets, I and II, developed after discovery of MgB2 in 2000. The SN2-MgB2 Magnet II—0.5 T/240 mm, SN2-cooled, and operated in persistent mode—was completed in January 2016. The final major topic in this article is a tabletop LHe-free, persistent-mode 1.5 T/70 mm SN2-MgB2 ‘finger’ MRI magnet for osteoporosis screening—we expect to begin this project in 2017. Before concluding this article, I present my current view on challenges and prospects for MgB2 MRI magnets.

  17. Safety issues of space liquid-helium and solid-cryogen systems

    NASA Astrophysics Data System (ADS)

    Mason, Peter V.

    2002-05-01

    Safety of hardware and personnel is a major concern in space programs. Space cryogenic systems are particularly prone to risk because of their complexity and because of the potential for overpressurization resulting from blockage of vent paths during the integration and test process. A number of space flight programs with liquid-helium and solid-cryogen systems have had incidents which resulted in risk or actual damage to flight hardware, or in risk to personnel. Since such incidents typically occur late in the development cycle, costs due to delays are extremely high. A second major of area of risk is the use of cooling loops in solid cryogen systems. When cooling is performed, the cryogen contracts and cryogen from warmer locations vaporizes and is deposited in the voids. This can lead to rupture of tankage and plumbing. Risk reduction measures include two-fault tolerant design, systematic use of burst disks and relief valves, careful analysis of possible risks, detailed and well-reviewed procedures and redundancy of critical systems, such as valves and valve drive circuitry. We will discuss the design and operation of space cryogenics systems from a safety point of view. We will also describe a number of incidents, their causes, the corrective steps taken and lessons learned.

  18. Characteristics of a liquid-helium-free calibration apparatus for cryogenic thermometers

    NASA Astrophysics Data System (ADS)

    Shimazaki, T.

    2013-09-01

    Closed-cycle Joule-Thomson (JT) cryocoolers have been developed at National Metrology Institute of Japan (NMIJ)/National Institute of Advanced Industrial Science and Technology (AIST) with the aim of realizing a liquid-helium-free calibration apparatus for cryogenic thermometers between 0.65 K and 25 K. The latest JT cryocooler at NMIJ/AIST consists of a 3He JT cooling circuit and a pulse tube mechanical refrigerator. The characteristics of the apparatus including a residual gas analysis of the JT cooling circuit are presented in this paper. Currently the initial cool-down is performed using a heat-exchange gas. It normally takes about 30 h to reduce the temperature from room temperature to 5 K at the thermometer comparison block of the apparatus. The correct timing of the removal of the heatexchange gas is important for the efficient operation of the apparatus. Incomplete removal of the heat-exchange gas induces excess heat load on the apparatus and thermal disturbances. Some examples of abrupt temperature bursts are discussed in this paper. Mechanical refrigerators generate cyclic mechanical vibrations, and precision resistance thermometers are usually very sensitive to a mechanical vibration. The measured vibration level of the developed apparatus is reported. The damage to the apparatus due to the magnitude 9.0 earthquake on March 11, 2011, and possible countermeasures in the case of future earthquakes are also discussed.

  19. Fracture behaviour of the 14Cr ODS steel exposed to helium and liquid lead

    NASA Astrophysics Data System (ADS)

    Hojna, Anna; Di Gabriele, Fosca; Hadraba, Hynek; Husak, Roman; Kubena, Ivo; Rozumova, Lucia; Bublikova, Petra; Kalivodova, Jana; Matejicek, Jiri

    2017-07-01

    This work describes the fracture behaviour of the 14Cr ODS steel produced by mechanical alloying process, after high temperature exposures. Small specimens were exposed to helium gas in a furnace at 720 °C for 500 h. Another set of specimens was exposed to flowing liquid lead in the COLONRI II loop at 650 °C for 1000 h. All specimens were tested for the impact and tensile behaviour. The impact test results are compared to other sets of specimens in the as received state and after isothermal annealing at 650 °C for 1000 h. The impact curves of the exposed materials showed positive shifts on the transition temperature. While the upper shelf value did not change in the Pb exposed ODS steel, it significantly increased in the He exposed one. The differences are discussed in terms of surface and subsurface microscopy observation. The embrittlement can be explained as the effect of a slight change in the grain boundary and size distribution combined with the depletion of sub-surface region from alloying elements forming oxide scale on the surface.

  20. Description of a sample holder for ion channeling near liquid-helium temperature

    NASA Astrophysics Data System (ADS)

    Daudin, B.; Dubus, M.; Viargues, F.

    1990-01-01

    Ion channeling is sensitive to very small shifts (10 -2 nm) of the atomic equilibrium positions. As a consequence, this technique appears to be suitable to study lattice dynamics, in particular when a displacive phase transition occurs. As many phase transitions of interest are observed at low temperature, we developed a three-axis goniometer in order to perform channeling experiments between 5 and 30 K. As no thermal screen could be placed between the sample and the ion beam, the quantity of heat radiated onto the sample holder was very large. The technical solutions which were chosen to overcome this difficulty and ensure both an efficient cooling and a good rotational mobility of the sample are described in detail. A liquid-helium flow of ˜ 6.5 1/h was found to be necessary to achieve a continuous refrigeration of the sample at 5 K. To conclude, proton channeling experiments in the blue bronze, K 0.3MoO 3, are presented as an illustration of the device possibilities.