Science.gov

Sample records for superfluid liquid helium

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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. PMID:25146284

  7. 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.

  8. Magnetic Observations of the Superfluid-Superfluid Phase Transition in Liquid Helium Three

    NASA Astrophysics Data System (ADS)

    Boyd, Stephen Thomas

    We report observations of the first-order phase transition between the two superfluid phases of ^3He. We supercool a long cylindrical sample of the higher-temperature A phase in a magnetic field in a simple dc magnetometer. We then introduce B phase at one end of the sample and observe its growth into the supercooled A phase via the magnetometer signal. For temperatures above a certain value, rm T_{nom }, the phase interface travels up the tube at a fairly constant velocity, in reasonable agreement with the theory of Leggett and Yip. For temperatures below rm T_{nom} there arises a new interaction between the rapidly moving phase interface and the magnetization of the sample. Our observations allow some characterization of this new interaction.

  9. 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.

  10. 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.

  11. 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.

  12. Detection of Charged Particles in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Bandler, Simon Richard

    1995-01-01

    At the present time the measurement of the flux of neutrinos from the sun remains a challenging experimental problem. The ideal detector would be able to detect neutrinos at high rate, in real time, with good energy resolution and would have a threshold which is low enough for investigation of the entire solar neutrino spectrum. A new detection scheme using superfluid helium as a target has been proposed which has the potential to meet most of the criteria of the ideal detector. In this scheme a neutrino would be detected when it elastically scatters off an atomic electron in superfluid helium. The electron loses energy via a number of processes eventually leading to the generation of phonons and rotons in the liquid. At low temperatures these excitations propagate ballistically through the superfluid helium. When the excitations reach the free surface some of them are able to evaporate helium atoms. These atoms can be detected by an array of calorimeters suspended above the liquid surface. In this thesis, results are presented for a small -scale prototype of this type of detector. Experiments have been performed using various radioactive sources to generate energy depositions in the liquid. The results reveal details about the processes of generation of rotons and phonons, the propagation of these excitations through the superfluid, the evaporation of helium atoms and the adsorption of helium atoms onto the wafer. Results are also presented on the detection of fluorescent photons generated in the liquid. One source of energy depositions was 241{rm Am} which produces monoenergetic 5.5 MeV alpha particles. It was found that the ratio of the energy deposited in a calorimeter to the energy deposited in liquid helium was 0.084 when alpha's are emitted parallel to the liquid surface, and 0.020 for alpha's emitted perpendicular. The difference is due to the anisotropic distribution of helium excitations generated. A 113{rm Sn} source of 360 keV electrons stopped in

  13. 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…

  14. Superfluid helium on orbit transfer (SHOOT)

    NASA Technical Reports Server (NTRS)

    Dipirro, Michael J.

    1987-01-01

    A number of space flight experiments and entire facilities require superfluid helium as a coolant. Among these are the Space Infrared Telescope Facility (SIRTF), the Large Deployable Reflector (LDR), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (PAMF or Astromag), and perhaps even a future Hubble Space Telescope (HST) instrument. Because these systems are required to have long operational lifetimes, a means to replenish the liquid helium, which is exhausted in the cooling process, is required. The most efficient method of replenishment is to refill the helium dewars on orbit with superfluid helium (liquid helium below 2.17 Kelvin). To develop and prove the technology required for this liquid helium refill, a program of ground and flight testing was begun. The flight demonstration is baselined as a two flight program. The first, described in this paper, will prove the concepts involved at both the component and system level. The second flight will demonstrate active astronaut involvement and semi-automated operation. The current target date for the first launch is early 1991.

  15. 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.'

  16. Superfluid Helium On-Orbit Transfer (SHOOT) operatons

    NASA Technical Reports Server (NTRS)

    Kittel, P.; Dipirro, M. J.

    1988-01-01

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

  17. Progress on Electrode Designs and Tests to Generate High Electric Field in Superfluid Liquid Helium-4 for the SNS nEDM Experiment

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    The SNS nEDM experiment is aiming to search for the neutron electric dipole moment (EDM) with ultracold neutrons (UCNs) stored in superfluid liquid helium-4 at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory, with a goal sensitivity of 3×10-28e-cm, an improvement of two orders of magnitude over the current limit. To achieve the goal sensitivity of the EDM searches,it relies on the stable application of a 75 kV/cm electric field across the UCN storage space without breakdowns in superfluid liquid helium-4. The electrode designs and tests on various geometries and coating materials are undergoing. The high voltage tests in superfluid helium-4 are performed in a specially-designed apparatus at temperatures as low as 0.4 K and pressures between saturated vapor pressure (SVP) of liquid helium and 1 atm. These tests would help in a better understanding of the electric breakdown phenomenon in liquid helium-4. In this talk, we will present the latest progress on electrode designs and tests,and their implications of findings that affect the design of the SNS nEDM experiment.

  18. 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.

  19. Dynamics of superfluid helium in zero gravity. [Spacelab 2 investigation

    NASA Technical Reports Server (NTRS)

    Mason, P. V.

    1981-01-01

    The Spacelab 2 superfluid helium experiment was designed to: (1) examine the behavior of capillary waves and measure their velocity and dampling; (2) study the sloshing motion of bulk superfluid helium in near-zero gravity in order to determine its effects on sensors and attitude control systems for far infrared telescopes; and (3) determine the temperature distributions in the liquid and their correlation with bulk motion. The experiment system includes a helium cryostat with a sensor head and a microcomputer to provide electrical excitation and gather and transmit resultant responses to the experiment teams on the ground. Astronaut intervention is possible.

  20. 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.

  1. 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.

  2. Acoustics of the Lambda Transition in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Megson, Peter; Meichle, David; Lathrop, Daniel

    2014-11-01

    Liquid Helium undergoes a phase transition and becomes a quantum superfluid when cooled below the Lambda transition temperature of 2.17 Kelvin. The superfluid, which is a partial Bose Einstein Condensate, exhibits unique macroscopic properties such as flow without viscosity and ballistic temperature propagation. We have recorded striking audio-frequency sounds using a micro electromechanical microphone (MEMS) present as the Helium goes through the Lambda transition. Characterization of this sound, as well as its relevance to theories of the Lambda transition will be presented.

  3. Temperature Rises In Pumps For Superfluid Helium

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1990-01-01

    Report discusses increases in temperature of superfluid helium in centrifugal and fountain-effect pumps. Intended for use in transfers of superfluid helium in outer space. Increases in temperature significantly affect losses during transfers and are important in selection of temperatures of supply tanks. Purpose of study, increase in temperature in fountain-effect pump calculated on basis of thermodynamic considerations, starting from assumption of ideal pump. Results of recent tests of ceramic material intended for use in such pumps support this assumption. Overall, centrifugal pumps more effective because it produces smaller rise in temperature.

  4. Germanium resistance thermometer calibration at superfluid helium temperatures

    SciTech Connect

    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.

  5. Vortex reconnection in superfluid helium

    SciTech Connect

    Koplik, J. ); Levine, H. )

    1993-08-30

    A useful physical model for superfluid turbulence considers the flow to consist of a dense tangle of vortex lines which evolve and interact. It has been suggested that these vortex lines can dynamically reconnect upon close approach. Here, we consider the nonlinear Schroedinger equation model of superfluid quantum mechanics, and use numerical simulation to study this topology changing core-scale process. Our results support the idea that vortex reconnection will occur whenever filaments come within a few core lengths of one another.

  6. Hydrodynamics of superfluid helium in a single nanohole.

    PubMed

    Savard, M; Dauphinais, G; Gervais, G

    2011-12-16

    The flow of liquid helium through a single nanohole with radius smaller than 25 nm was studied. Mass flow was induced by applying a pressure difference of up to 1.4 bar across a 50 nm thick Si(3)N(4) membrane and was measured directly by means of mass spectrometry. In liquid He I, we experimentally show that the fluid is not clamped by the short pipe with diameter-to-length ratio D/L≃1, despite the small diameter of the nanohole. This viscous flow is quantitatively understood by making use of a model of flow in short pipes. In liquid He II, a two-fluid model for mass flow is used to extract the superfluid velocity in the nanohole for different pressure heads at temperatures close to the superfluid transition. These velocities compare well to existing data for the critical superflow of liquid helium in other confined systems. PMID:22243081

  7. Properties of Moving Electron Bubbles in Superfluid Helium

    SciTech Connect

    Guo Wei; Maris, Humphrey J.

    2006-09-07

    It is well known that the Bernoulli effect modifies the shape of gas bubbles moving through a liquid. In this paper we investigate the influence of the Bernoulli pressure on the shape of electron bubbles moving through superfluid helium. We show that an electron bubble moving through liquid at zero pressure becomes unstable when its velocity reaches approximately 47 m s-1. In addition, the change in shape contributes significantly to the variation of the bubble mobility with velocity.

  8. Electron Diffraction of Superfluid Helium Droplets

    PubMed Central

    2014-01-01

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

  9. Dynamics of vortex assisted metal condensation in superfluid helium.

    PubMed

    Popov, Evgeny; Mammetkuliyev, Muhammet; Eloranta, Jussi

    2013-05-28

    Laser ablation of copper and silver targets immersed in bulk normal and superfluid (4)He was studied through time-resolved shadowgraph photography. In normal fluid, only a sub-millimeter cavitation bubble is created and immediate formation of metal clusters is observed within a few hundred microseconds. The metal clusters remain spatially tightly focused up to 15 ms, and it is proposed that this observation may find applications in particle image velocimetry. In superfluid helium, the cavitation bubble formation process is distinctly different from the normal fluid. Due to the high thermal conductivity and an apparent lag in the breakdown of superfluidity, about 20% of the laser pulse energy was transferred directly into the liquid and a large gas bubble, up to several millimeters depending on laser pulse energy, is created. The internal temperature of the gas bubble is estimated to exceed 9 K and the following bubble cool down period therefore includes two separate phase transitions: gas-normal liquid and normal liquid-superfluid. The last stage of the cool down process was assigned to the superfluid lambda transition where a sudden formation of large metal clusters is observed. This is attributed to high vorticity created in the volume where the gas bubble previously resided. As shown by theoretical bosonic density functional theory calculations, quantized vortices can trap atoms and dimers efficiently, exhibiting static binding energies up to 22 K. This, combined with hydrodynamic Bernoulli attraction, yields total binding energies as high as 35 K. For larger clusters, the static binding energy increases as a function of the volume occupied in the liquid to minimize the surface tension energy. For heliophobic species an energy barrier develops as a function of the cluster size, whereas heliophilics show barrierless entry into vortices. The present theoretical and experimental observations are used to rationalize the previously reported metal nanowire assembly in

  10. Observation of a New Type of Electron Bubble in Superfluid Helium

    SciTech Connect

    Ghosh, Ambarish; Maris, Humphrey J.

    2005-12-31

    We report on the observation of a new type of electron bubble in superfluid helium-4. This object appears to be larger than the normal electron bubble and is associated with the presence of quantized vortices in the liquid.

  11. 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.

  12. 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

  13. The liquid/vapor boundary in a porous plug. [as separator for superfluid helium and its vapor

    NASA Technical Reports Server (NTRS)

    Dipirro, M. J.; Zahniser, J.

    1990-01-01

    Results are presented from measurements of pressure and temperature differences as a function of the flow rate and hydrostatic head for two types of porous plugs for phase separation of superfluid He and He vapor: (1) a plug made of sintered stainless steel, similar to that in the IRAS, IRT, and COBE dewars except for larger pores, and (2) a glass plug with pores of uniform cross section. Results show that a liquid/vapor phase boundary exists at the outer surface of the porous plug for low flows or large hydrostatic heads; as the flow increases or the hydrostatic head decreases, the boundary retreats into the plug. Some hysteresis near the phase boundary retreat was observed in the stainless steel plug.

  14. Characterization of reconnecting vortices in superfluid helium.

    PubMed

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

    2008-09-16

    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 1/2, consistent with the self-similar evolution of the vortices. PMID:18768790

  15. 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

  16. 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.

  17. Thermo-Mechanical Pumps for Superfluid Helium

    SciTech Connect

    Kaiser, G.; Schumann, B.; Stangl, R.; Binneberg, A.; Wobst, E.

    2004-06-23

    In Alpha Magnetic Spectrometer-02 (AMS-02) experiment a large scale superconducting magnet separates charged particles coming from cosmic radiation. Two thermo-mechanical pumps (TMP), operating by use of the Fountain-effect, will be used to supply the current leads and the magnet coil after quench with superfluid helium. These TMP are currently under development at ILK Dresden. Due to the applications the TMP are required to pump a mass flow of 0.2 g/s. After introduction into the basic principles essential for TMP function, we report on the development and tests of the TMP for AMS-02.

  18. 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.

  19. 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.

  20. Liquid helium-II counterflow in a tube packed with angular particles and application as a superfluid pump

    NASA Astrophysics Data System (ADS)

    Guenin, B. M.; Hess, G. B.

    1980-09-01

    Observations are reported on the operation of a recirculating superfluid 4He pump capable of driving a stable superfluid flow from subcritical continuously through a wide range of chemical potential head, ranging from very small to moderately large. The pump consists of a superfluid path shunting a thermal counterflow tube. The latter is packed with coarse angular particles, which generate quantized vorticity at a low and reproducible superfluid velocity in the tube, and so improve control of the superfluid flux in the shunt. We have made a limited study of the tube characteristic for conditions other than pure counterflow as a basis for analyzing the pump operation. Applied to a study of the onset of dissipation in an external sample, this pump has proved convinient and free of long relaxation times. Some precautions must be taken in matching the counterflow tube to the sample, to avoid regions of possible instability.

  1. Phase order in superfluid helium films

    NASA Astrophysics Data System (ADS)

    Bramwell, Steven T.; Faulkner, Michael F.; Holdsworth, Peter C. W.; Taroni, Andrea

    2015-12-01

    Classic experimental data on helium films are transformed to estimate a finite-size phase order parameter that measures the thermal degradation of the condensate fraction in the two-dimensional superfluid. The order parameter is found to evolve thermally with the exponent β = 3 π^2/128 , a characteristic, in analogous magnetic systems, of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. Universal scaling near the BKT fixed point generates a collapse of experimental data on helium and ferromagnetic films, and implies new experiments and theoretical protocols to explore the phase order. These results give a striking example of experimental finite-size scaling in a critical system that is broadly relevant to two-dimensional Bose fluids. This paper is dedicated to the memory of our friend and colleague Maxime Clusel, with whom we enjoyed many stimulating discussions on related topics.

  2. Production and storage of ultra cold neutrons in superfluid helium

    SciTech Connect

    Greene, G.L.; Lamoreaux, S.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL) concerning the investigation of a new method for the experimental exploitation of ultra-cold neutrons. The production and storage of ultra cold neutrons in superfluid helium has been suggested as a tool for the production of high densities of ultra cold neutrons for fundamental nuclear physics as well as for sensitive measurements for condensed matter. A particular application of this technique has been suggested by Doyle and Lamoreaux that involves the trapping of neutrons in a magnetic field within the superfluid helium volume. Neutron decays within the trap volume are detected by the scintillation light produced in the liquid helium. A cryostat and magnetic trap have been constructed as well as a prototype light detection system. This system was installed on a cold neutron beam line at the NIST Cold Neutron Research Facility in the summer of 1997. Preliminary results indicate the detection of helium scintillation light from the detection vessel.

  3. 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.

  4. Three Dimensional Observations of Quantum Vortex Dynamics in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Megson, Peter; Lathrop, Daniel

    Liquid helium, when cooled below 2.17 K, becomes a superfluid with exotic physical properties such as flow without friction. Superfluid flow is irrotational except about line-like topological phase defects with quantized circulation, known as quantum vortices. The dynamics of these vortices include events such as reconnection, wherein vortices meet and exchange tails, and Kelvin wave propagation, a possible mechanism for energy dissipation. We observe the dynamics of fluorescent nanoparticles trapped on the vortices using a newly developed 3D stereographic system. This talk will present new observations of reconnection events and analysis comparing vortex reconnection behavior in three dimensions to previous work that observed such events in two-dimensional projection. In particular, we discuss the power law scaling of vortex separation as a function of time and the effect of the initial angle of separation between the vortex filaments.

  5. 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.

  6. 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.

  7. Novel methods to create multielectron bubbles in superfluid helium.

    PubMed

    Fang, J; Dementyev, Anatoly E; Tempere, J; Silvera, Isaac F

    2011-03-01

    An equilibrium multielectron bubble (MEB) in liquid helium is a fascinating object with a spherical two-dimensional electron gas on its surface. We discuss two ways in which they have been created. For MEBs that have been observed in the dome of a cylindrical cell with an unexpectedly short lifetime, we show analytically why these MEBs can discharge by tunneling. Using a novel method, MEBs have been extracted from a vapor sheath around a hot filament in superfluid helium by applying electric fields up to 15 kV∕cm, and photographed with high-speed video. Charges as high as 1.6×10(-9) C (∼10(10) electrons) have been measured. The latter method provides a means of capture in an electromagnetic trap to allow the study of the extensive exciting properties of these elusive objects. PMID:21456760

  8. Possible Stimulation of Nuclear alpha Decay by Superfluid Helium

    SciTech Connect

    Barabanov, A. L.

    2009-08-28

    It is suggested that superfluid helium (condensate of {sup 4}He atoms) may stimulate nuclear alpha decay in a situation when an alpha emitter moves through superfluid helium with fine-tuned velocity, so that the backward-emitted alpha particle is at rest in the laboratory frame. It is shown that the probability of stimulated alpha decay in this case may be sizable enough to be detected.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Large quantum superpositions of a nanoparticle immersed in superfluid helium

    NASA Astrophysics Data System (ADS)

    Lychkovskiy, O.

    2016-06-01

    Preparing and detecting spatially extended quantum superpositions of a massive object comprises an important fundamental test of quantum theory. These quantum states are extremely fragile and tend to quickly decay into incoherent mixtures due to the environmental decoherence. Experimental setups considered up to date address this threat in a conceptually straightforward way—by eliminating the environment, i.e., by isolating an object in a sufficiently high vacuum. We show that another option exists: decoherence is suppressed in the presence of a strongly interacting environment if this environment is superfluid. Indeed, as long as an object immersed in a pure superfluid at zero temperature moves with a velocity below the critical one, it does not create, absorb, or scatter any excitations of the superfluid. Hence, in this idealized situation the decoherence is absent. In reality the decoherence will be present due to thermal excitations of the superfluid and impurities contaminating the superfluid. We examine various decoherence channels in the superfluid helium at 1 mK. Performing interference experiments in superfluid helium can provide certain practical advantages compared to conventional schemes, e.g., compensation of gravity by the buoyancy force and effective cooling.

  14. Imaging of quantum vortices in superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Vilesov, Andrey

    Helium nanodroplets are especially promising for exploring quantum hydrodynamics in self-contained, isolated superfluids. However, until very recently, the dynamic properties of individual droplets, such as vorticity, could not be assessed experimentally. Here we investigate the rotation of single superfluid 4-He droplets ranging from 200 to 2000 nm in diameter at T = 0.4 K via single-shot femtosecond X-ray coherent diffractive imaging. The droplets were produced by free jet expansion of liquid helium into vacuum. The angular velocities of the droplets were estimated from the centrifugal distortion and span a range from vanishing to those close to the disintegration limit. For visualization of vortices, Xe atoms were added to the droplets where they gather in cores forming nm-thin filaments. A newly developed phase retrieval technique enables the reconstruction of the instantaneous positions and shapes of the vortices from the diffraction images with about 20 nm resolution. The vorticity attainable in the nano-droplets was found to be about six orders of magnitude larger than achieved in previous experiments in the bulk. Stationary configurations of vortices are represented by triangular lattice in large (2 μm) droplets and symmetric arrangements of few vortices in smaller (200 nm) droplets. Evidence for non-stationary vortex dynamics comes from observation of asymmetric formations of vortices in some droplets. This collaborative work was performed at Linac Coherent Light Source, the free electron laser within SLAC National Accelerator Laboratory. The experiments and the full list of collaborators are reported in: L. F. Gomez et. al. Science, 345 (2014) 906.

  15. 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.

  16. 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.

  17. The design, construction and testing of floats for use in superfluid helium

    SciTech Connect

    Tew, W.L.; Bartlett, D.F.

    1994-12-31

    The authors employ a technique which uses superfluid {sup 4}He as a delicate, low noise suspension medium. The goal is to create a new type of torsion balance for earth based gravitational experiments requiring very high sensitivity. As a fluid bearing replacing the classical torsion fiber suspension, liquid helium II offers several unique advantages. Most notable are its extremely low viscosity, high thermal stability, inertness and small thermally driven fluctuations. The authors present the design and performance aspects of buoyant torsional oscillators and the cryogenic system used to maintain the superfluid medium.

  18. Cylindrical standing surface waves in superfluid helium

    SciTech Connect

    Atkin, R.J.; Fox, N.

    1987-02-01

    A theoretical analysis is given of the resonant frequencies of standing surface waves produced in a cylinder filled with superfluid /sup 4/He. In particular, it is shown that a heat transfer coefficient involved in a recently proposed empirical boundary condition can be related to the Kapitza resistance.

  19. Second Sound Scattering in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Rosgen, Thomas

    Focusing cavities are used to study the scattering of second sound in liquid helium II. The special geometries reduce wall interference effects and allow measurements in very small test volumes. In a first experiment, a double elliptical cavity is used to focus a second sound wave onto a small wire target. A thin film bolometer measures the side scattered wave component. The agreement with a theoretical estimate is reasonable, although some problems arise from the small measurement volume and associated alignment requirements. A second cavity is based on confocal parabolas, thus enabling the use of large planar sensors. A cylindrical heater produces again a focused second sound wave. Three sensors monitor the transmitted wave component as well as the side scatter in two different directions. The side looking sensors have very high sensitivities due to their large size and resistance. Specially developed cryogenic amplifiers are used to match them to the signal cables. In one case, a second auxiliary heater is used to set up a strong counterflow in the focal region. The second sound wave then scatters from the induced fluid disturbances. Attempts to observe scattering from quantized vortex lines in the rotating parabolic cavity ultimately did not succeed, although a theoretical estimate seems to indicate a basic feasibility.

  20. Superfluid helium in fully saturated porous media

    SciTech Connect

    Huang, K. ); Meng, H. )

    1993-09-01

    The flow of superfluid [sup 4]He through spongelike media at full saturation is modeled by the flow of current through an Ohmic network with random resistors. Solving Kirchhoff's equations leads to the conclusion that the superfluid critical point is a percolation threshold, with critical exponent 1.7. The fractal dimension of the percolating cluster is 2.6. These lead to a specific-heat exponent [alpha]=[minus]5.4, by the Josephson hyperscaling relation. Existing experiments apparently do not cover the critical region. Instead, they measure mean-field'' exponents, whose values for Vycor, aerogel, and xerogel can all be reproduced by choosing appropriate distribution functions for the resistors.

  1. Vacuum-ultraviolet laser uses superfluid helium

    NASA Technical Reports Server (NTRS)

    Zmuidzinas, J. S.

    1979-01-01

    Vacuum ultra violet laser in wavelength around 0.800 microns is produced by using optical pumping to increase lifetimes of excited metastable molecules in super fluid helium. In method, super fluid helium is pumped electronically to produce excited HE2, and then pumped by circularly polarized 0.9096 - micron radiation to aline excited HE2 molecular spins. High power ultraviolet radiation has potential applications in molecular reaction studies, power transmission in space, and biomedical research.

  2. 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.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    PubMed

    Zhang, Jie; He, Yunteng; Kong, Wei

    2016-06-14

    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

  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. Communication: Electron diffraction of ferrocene in superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; He, Yunteng; Kong, Wei

    2016-06-01

    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.

  9. Metastable Helium Molecules as Tracers in Superfluid {sup 4}He

    SciTech Connect

    Guo, W.; Wright, J. D.; Cahn, S. B.; Nikkel, J. A.; McKinsey, D. N.

    2009-06-12

    Metastable helium molecules generated in a discharge near a sharp tungsten tip immersed in superfluid {sup 4}He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He{sub 2}* molecules is produced. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the first excited vibrational level of the triplet ground state. Subsequent imaging of the tagged molecules with an expanded 925 nm probe laser pulse allows us to measure the flow velocity of the jet. The techniques we developed provide new tools in quantitatively studying the normal fluid flow in superfluid helium.

  10. Metastable helium molecules as tracers in superfluid 4He.

    PubMed

    Guo, W; Wright, J D; Cahn, S B; Nikkel, J A; McKinsey, D N

    2009-06-12

    Metastable helium molecules generated in a discharge near a sharp tungsten tip immersed in superfluid 4He are imaged using a laser-induced-fluorescence technique. By pulsing the tip, a small cloud of He(2*) molecules is produced. We can determine the normal-fluid velocity in a heat-induced counterflow by tracing the position of a single molecule cloud. As we run the tip in continuous field-emission mode, a normal-fluid jet from the tip is generated and molecules are entrained in the jet. A focused 910 nm pump laser pulse is used to drive a small group of molecules to the first excited vibrational level of the triplet ground state. Subsequent imaging of the tagged molecules with an expanded 925 nm probe laser pulse allows us to measure the flow velocity of the jet. The techniques we developed provide new tools in quantitatively studying the normal fluid flow in superfluid helium. PMID:19658945

  11. Superfluidity within a small helium-4 cluster: the microscopic andronikashvili experiment

    PubMed

    Grebenev; Toennies; Vilesov

    1998-03-27

    The infrared spectrum of single oxygen carbon sulfide (OCS) molecules was measured inside large superfluid pure helium-4 droplets and nonsuperfluid pure helium-3 droplets, both consisting of about 10(4) atoms. In the helium-4 droplets, sharp rotational lines were observed, whereas in helium-3 only a broad peak was found. This difference is interpreted as evidence that the narrow rotational lines, which imply free rotations, are a microscopic manifestation of superfluidity. Upon addition of 60 helium-4 atoms to the pure helium-3 droplets, the same sharp rotational lines were found; it appears that 60 is the minimum number needed for superfluidity. PMID:9516103

  12. 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.

  13. Three-dimensional nanoparticle dynamics in superfluid helium

    NASA Astrophysics Data System (ADS)

    Lathrop, Daniel

    Quantized vortices have been observed in superfluid 4He and AMO trapped atom systems, and have been infered in superfluid 3He and neutron stars. The dynamics of quantum fluids is substantially controlled by the motion of quantized vortices, which are topological phase defects analogous to crystalline dislocations. Long-range quantum order underlies a number of related physical phenomena, including superfluidity, trapped-atom Bose-Einstein condensates, superconductivity, ferromagnetism, antiferromagnetism, lasers, and the Higgs mechanism. While superfluidity in 4He is one of the first discovered of these, it is one of the least understood, given that the strongly interacting nature of helium makes theory difficult, and that development of local experimental probes is lagging. The advent of three-dimensional flow visualization of particles that trace quantized vortices provides new oportunities to investigate their creation and dynamics. We work to address the following questions using flow visualization in this system: What are field equations that express the coupling of the ordered and disordered parts of the flow? How does vortex reconnection lead to dissipation and breaking of time-reversal invariance? What are the similarities and differences between quantum and classical turbulence at small and large scales? How do quantized vortices form through the lambda transition? This work is supported by the National Science Foundation DMR CMP 1407472.

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

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

  15. Transformation of second sound into surface waves in superfluid helium

    SciTech Connect

    Khalatnikov, I.M.; Kolmakov, G.V.; Pokrovsky, V.L.

    1995-05-01

    The Hamiltonian theory of superfluid liquid with a free boundary is developed. Nonlinear amplitudes of parametric Cherenkov radiation of a surface wave by second sound and the inner decay of second sound waves are found. Threshold amplitudes of second sound waves for these two processes are determined. 4 refs.

  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. Critical velocity of superfluid helium flow in narrow pore filters

    NASA Astrophysics Data System (ADS)

    Hofmann, A.

    1990-05-01

    The flow rates of superfluid helium passing through a spongelike plug made from a stack of high-porosity cellulose-nitrate membrane filters were measured, comparing three grades of filters: 10, 50, and 200 nm. The critical flow rate was analyzed from the onset of nonzero difference in the chemical potential across the plug. The flow, driven by activating a heater, was measured with an acoustic flowmeter. It is shown that the critical flow rate increases with decreasing filtration grade and that the upper limit of the superfluid flow velocity can be predicted from the quoted filtration grade of the filter and from a shape factor derived from elementary geometric conditions of densely packed spheres. This model yields correct temperature dependence of the critical velocity.

  19. 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.

  20. Oscillatory motion: quantum whistling in superfluid helium-4.

    PubMed

    Hoskinson, E; Packard, R E; Haard, Thomas M

    2005-01-27

    Fundamental considerations predict that macroscopic quantum systems such as superfluids and the electrons in superconductors will undergo oscillatory motion when forced through a small constriction. Here we induce these oscillations in superfluid helium-4 (4He) by pushing it through an array of nanometre-sized apertures. The oscillations, which are detected as an audible whistling sound, obey the so-called Josephson frequency relation and occur coherently among all the apertures. The discovery of this property in 4He at the relatively high temperature of 2 K (2,000 times higher than the temperature at which a related but different phenomenon occurs in 3He) may pave the way for a new class of practical rotation sensors of unprecedented precision. PMID:15674281

  1. Heat Transfer through Porous Media in Static Superfluid Helium

    SciTech Connect

    Baudouy, B.; Juster, F.-P.; Allain, H.; Maekawa, R.

    2006-04-27

    Heat transfer through porous media in static saturated superfluid helium is investigated for porous media with different thickness, porosity and pore size. For large pore diameter, data are analyzed with the tortuosity concept in the pure Gorter-Mellink regime. It is shown that the tortuosity is constant over the temperature range investigated. For smaller pore diameter, the analysis reveals that the permeability is temperature-dependent in the Landau regime. In the intermediate regime, a model, including Landau and Gorter-Mellink regime, predicts a constant tortuosity within 10% but falls short predicting correctly the experimental data over the entire range of temperature.

  2. Reflection of hydrogen atoms from the surface of superfluid helium

    SciTech Connect

    Tiesinga, E.; Stoof, H.T.C.; Verhaar, B.J. )

    1990-05-01

    We propose a new method for studying the reflection of a hydrogen atom from a superfluid-helium film. Starting from the narrow width of the reflected angular distribution recently found experimentally, we tentatively extrapolate to the extreme limit of low ripplon wave numbers in which the adiabatic or degenerate-internal-states approximation becomes valid. We obtain simple closed expressions for single- and multiple-ripplon processes, which do not require the integration of a Schroedinger equation for their evaluation and do not depend on the specific form of the potential.

  3. Nonlinear optical effects of ultrahigh-Q silicon photonic nanocavities immersed in superfluid helium

    PubMed Central

    Sun, Xiankai; Zhang, Xufeng; Schuck, Carsten; Tang, Hong X.

    2013-01-01

    Photonic nanocavities are a key component in many applications because of their capability of trapping and storing photons and enhancing interactions of light with various functional materials and structures. The maximal number of photons that can be stored in silicon photonic cavities is limited by the free-carrier and thermo-optic effects at room temperature. To reduce such effects, we performed the first experimental study of optical nonlinearities in ultrahigh-Q silicon disk nanocavities at cryogenic temperatures in a superfluid helium environment. At elevated input power, the cavity transmission spectra exhibit distinct blue-shifted bistability behavior when temperature crosses the liquid helium lambda point. At even lower temperatures, the spectra restore to symmetric Lorentzian shapes. Under this condition, we obtain a large intracavity photon number of about 40,000, which is limited ultimately by the local helium phase transition. These new discoveries are explained by theoretical calculations and numerical simulations. PMID:23486445

  4. Mechanical pumps for superfluid helium transfer in space

    NASA Astrophysics Data System (ADS)

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

    1988-02-01

    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.

  5. Flow of superfluid helium in tubes with heated walls

    NASA Technical Reports Server (NTRS)

    Snyder, H. A.; Mord, A. J.

    1991-01-01

    The equations for superfluid helium flowing through a straight tube with heated walls are integrated. The model equations are based on those of Landau as modified for superfluid turbulence by Gorter and Mellink (1949). The model is implemented by the program SUPERFLOW which runs on a personal computer. The effect of the heating level on the mass flux, the energy flux, and the pressure and temperature profiles is investigated. The four types of profiles which occur without sidewall heating are also found with heated walls. The progression through these four types is shown to depend primarily on the dimensionless parameter, defined previously to characterize the unheated profiles, and a dimensionless ratio of heat fluxes. The pressure and temperature maxima which rise well above the boundary values increase significantly with sidewall heating. Approximate design equations for estimating the mass flux and the profiles are presented. The physical basis of the results is discussed. These results are useful in the design of optimal cooling loops and other superfluid flow systems.

  6. Holographic vortex liquids and superfluid turbulence.

    PubMed

    Chesler, Paul M; Liu, Hong; Adams, Allan

    2013-07-26

    Superfluid turbulence is a fascinating phenomenon for which a satisfactory theoretical framework is lacking. Holographic duality provides a systematic approach to studying such quantum turbulence by mapping the dynamics of a strongly interacting quantum liquid into the dynamics of classical gravity. We use this gravitational description to numerically construct turbulent flows in a holographic superfluid in two spatial dimensions. We find that the superfluid kinetic energy spectrum obeys the Kolmogorov -5/3 scaling law, with energy injected at long wavelengths undergoing a direct cascade to short wavelengths where dissipation by vortex annihilation and vortex drag becomes efficient. This dissipation has a simple gravitational interpretation as energy flux across a black hole event horizon. PMID:23888034

  7. 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.

  8. Effect of the permeability of the porous shell on the vapor film thickness during boiling of superfluid helium in microgravity

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    This paper presents a theoretically study of the boiling of superfluid helium on a cylindrical heater placed in a coaxial porous shell in microgravity. Steady-state transfer processes at the interface are studied using molecular-kinetic methods. The Boltzmann transport equation is solved by the moment method based on the four-moment approximation in the form of a two-sided Maxwellian. The obtained solution is used to calculate the heat flux density in film boiling on a cylindrical heating surface in the case where the film thickness is comparable to the diameter of the heater. The motion of the normal component of the superfluid liquid in pores is described by equations that take into account heat and mass transfer in superfluid helium. The relation between the vapor film thickness and the structural characteristics and geometrical dimensions of the porous shell is obtained. Analysis of the results of the calculations is given.

  9. NMR study of the magnetization of superfluid helium-3-boron and NMR of superfluid helium-3 in aerogel

    NASA Astrophysics Data System (ADS)

    Haard, Thomas Michael

    Pulsed NMR measurements of superfluid 3He confined in 98.2% porosity silica aerogel are reported. The aerogel suppressed the superfluid transition temperature TC and the order parameter magnitude from their bulk values in qualitative agreement with impurity scattering models. Magnetization measurements showed that the superfluid is an equal spin pairing state (ESP). The superfluid exhibited positive NMR frequency shifts with similar temperature dependence to those of the bulk A-phase, only smaller. TC was independent of the magnetic field for H < 1.8 kOe to within the experimental error. At 2.18 kOe an increased suppression of TC and the order parameter was observed. Two layers of solid 3He were adsorbed to the aerogel strands. When these were replaced with solid 4He a non-ESP superfluid state was observed. An experimental cell for measuring the heat capacity of 3He in aerogel was designed and fabricated. It was tested without aerogel by measuring the heat capacity of liquid 3He over a range of temperatures from 1 to 25 mK and at pressures of 7.0, 14.0, and 28.0 bar. The measurements in both the normal and superfluid phases were consistent with the data of Greywall. The discrepancy between static and dynamic measurements of the magnetization of superfluid 3He-B was characterized over a region of the phase diagram by comparison of nuclear magnetic resonance (NMR) data and recent SQUID data from other researchers. At the B- to A-phase transition, TAB, the discrepancy was absent at low pressure, but increased to 20% at 26.6 bar and 1.2 kOe. The NMR data were consistent with the weak-coupling-plus (wcp) theory at TAB for most pressures and fields. The Ginzburg-Landau strong-coupling parameter gz/( gz)wcp was determined from NMR results to equal 1.00 +/- 0.03 for all pressures. Combinations of the Ginzburg-Landau beta-parameters are reported that are consistent with this observation.

  10. 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.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  14. 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

  15. 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

  16. The Nanostructures Produced by Laser Ablation of Metals in Superfluid Helium

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    The coagulation of impurities in superfluid helium, in contrast to that in all other liquids where spherical colloid particles are usually produced, led to producing thin and long nanowires with regular internal structure. This is due to the presence in HeII of quasi one-dimensional quantized vortices serving as condensation nuclei and providing a catalyzing effect on the process of any impurities coagulation. The metal was introduced into superfluid helium by laser ablation of targets made of gold, copper, nickel, permalloy, indium, lead, tin and bismuth immersed in liquid HeII. For all of these metals, the formation of thin (about 8 nm in diameter), long high-quality nanowires was observed after laser ablation. The structure of nanowires as well as of micron-sized metallic spheres, appeared as products at high laser pulse energy, providing evidence that they were formed via molten state. The spheres are metastable, and under damage of their surface, thousands of nanoballs emerge from their interior. The hollow shells left after this event are similar to those found as the products of laser ablation in normal fluids. The metal ablation into HeII bulk from thin film was found much less effective then that from thick foils.

  17. Recurrences in rotational dynamics and experimental measurement of superfluidity in doped helium clusters

    SciTech Connect

    Xu Yunjie; Blinov, Nicholas; Jaeger, Wolfgang; Roy, Pierre-Nicholas

    2006-02-28

    We present the first experimental evidence of recurrences in the rotational dynamics of doped helium clusters. Using the dopant molecule as an experimental microscopic probe of superfluidity, we show that in small He{sub N}-N{sub 2}O complexes, superfluidity builds up in stages correlated with the filling and completion of a solvation shell.

  18. Selection of ionization paths of K2 on superfluid helium droplets by wave packet interference

    NASA Astrophysics Data System (ADS)

    Hild, Marek Bastian; Dufour, Adrien; Achazi, Georg; Patas, Alexander; Scheier, Paul; Lindinger, Albrecht

    2016-08-01

    We report on the control of wave packet dynamics for the ionization of K2 attached to the surface of superfluid helium droplets. The superfluid helium matrix acts as a heat sink and reduces the coherence time of molecular processes by dissipation. We use tailor-shaped pulses in order to activate or inhibit different ionization paths by constructive or destructive wave packet interference. A drastic change of the wave packet dynamics is observed by shifting the phase between the exciting sub pulses.

  19. 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.

  20. Detection of excited-state electron bubbles in superfluid helium.

    PubMed

    Konstantinov, Denis; Maris, Humphrey J

    2003-01-17

    We report on experiments in which the pressure oscillation associated with a sound wave is used to explode electron bubbles in liquid helium. Using this technique, we are able to detect the presence of electron bubbles in excited states. PMID:12570553

  1. Quantum transmission of atoms through a slab of superfluid helium.

    PubMed

    Williams, C D H; Wyatt, A F G

    2003-08-22

    We describe a measurement of the transmission probability of 4He atoms through a freely suspended slab of superfluid 4He at low temperatures. In our experiment the slab is realized by using an array of parallel cylindrical holes of diameter 51 microm in a glass disc of thickness 190 microm. By controlling the chemical potential, the holes can be made to fill or empty with liquid, and the surface curvature varied. We have measured the transmission of atom beams, generated by a thin-film heater and detected with a sensitive bolometer, through this structure. The results show that the dominant transmission channel is atom-R+ roton-atom with a probability p approximately 0.12 and that R+ rotons can undergo total internal reflection at the free liquid surfaces. PMID:14525250

  2. 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.

  3. 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.

  4. Linear electron chains on the surface of superfluid helium

    NASA Astrophysics Data System (ADS)

    Kovdrya, Yu. Z.; Nikolaenko, V. A.; Gladchenko, S. P.; Sokolov, S. S.

    1998-11-01

    A unique one-dimensional system of linear electron chains on the liquid helium surface is realized experimentally for the first time. This system is created by using the distortion of the helium surface and covering the profiled dielectric substrate in a confining electric field holding electrons in the liquid channels being formed. The carrier mobility in linear electric chains is measured in the temperature interval 0.5-1.8K in confining fields up to 1 kV/cm. It is shown that the electron mobility depends on the purity of the substrate surface. For clean substrates, the mobility increases with decreasing temperature in the entire investigated temperature range. The results of measurements are found to be in accord with the existing theory.

  5. 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.

    2016-03-01

    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.

  6. Implementation of the thermodynamic and phase transition equations of superfluid helium in CFD software

    NASA Astrophysics Data System (ADS)

    Bruce, R.; Pascali, S.; Vendramini, C.; Baudouy, B.

    2015-12-01

    The cryogenic design of the next generation of superconducting accelerator magnets depends on our ability to simulate the helium heat and mass transfer in the internal structure of these magnets. For that matter accurate tools must be developed such as numerical codes integrating the thermodynamic behavior and phase transition in superfluid helium. We have implemented in 2D and 3D, the He II conservation equations in Fluent© CFD software corresponding to a simplified two-fluid model. It consists of a conventional continuity equation, a modified momentum equation for the total fluid and an energy equation including the Gorter-Mellink internal convection term modeling the turbulence regime. The code is mainly suited to simulate transient and steady-state flow configurations. In addition, a new method has been developed to simulate the He II / He I transition in 2D based on a modified Volume Of Fluid method (VOF). The interface between the two states of liquid helium has been locally recreated in the corresponding cells to properly mimic the second order phase transition (no latent heat). Both steady and unsteady numerical simulation have been performed and compared with different experimental results.

  7. Superfluid turbulence

    NASA Technical Reports Server (NTRS)

    Samuels, David C.

    1993-01-01

    At low temperatures (below 5 Kelvin), helium is a liquid with a very low kinematic viscosity. It was proposed that wind tunnels could be built using liquid helium as the test fluid. The primary advantages of such wind tunnels would be a combination of large Reynolds numbers and a relatively small apparatus. It is hoped that this combination will allow the study of high Reynolds number flows in an academic setting. There are two basic types of liquid helium wind tunnels that can be built, corresponding to the two phases of liquid helium. The high temperature phase (between approximately 2 to 5 Kelvin) is called helium 1 and is a Navier-Stokes fluid. There are no unanswered scientific questions about the design or operation of a wind tunnel in the helium 1 phase. The low temperature phase (below approximately 2 Kelvin) of liquid helium is called helium 2. This is a quantum fluid, meaning that there are some properties of helium 2 which are directly due to quantum mechanical effects and which are not observed in Navier-Stokes fluids. The quantum effects that are relevant to this paper are: (1) helium 2 is well described as a superposition of two separate fluids called the superfluid and the normal fluid. The normal-fluid component is a Navier-Stokes fluid and the superfluid is an irrotational Euler fluid; and (2) circulation in the superfluid exists only in quantized vortex filaments. All quantized vortex filaments have identical circulations kappa and core size a. The objective of the research at CTR was to develop an understanding of the microscopic processes responsible for the observed Navier-Stokes behavior of helium 2 flows.

  8. Path Integral Quantum Monte Carlo Study of Coupling and Proximity Effects in Superfluid Helium-4

    NASA Astrophysics Data System (ADS)

    Graves, Max T.

    When bulk helium-4 is cooled below T = 2.18 K, it undergoes a phase transition to a superfluid, characterized by a complex wave function with a macroscopic phase and exhibits inviscid, quantized flow. The macroscopic phase coherence can be probed in a container filled with helium-4, by reducing one or more of its dimensions until they are smaller than the coherence length, the spatial distance over which order propagates. As this dimensional reduction occurs, enhanced thermal and quantum fluctuations push the transition to the superfluid state to lower temperatures. However, this trend can be countered via the proximity effect, where a bulk 3-dimensional (3d) superfluid is coupled to a low (2d) dimensional superfluid via a weak link producing superfluid correlations in the film at temperatures above the Kosterlitz-Thouless temperature. Recent experiments probing the coupling between 3d and 2d superfluid helium-4 have uncovered an anomalously large proximity effect, leading to an enhanced superfluid density that cannot be explained using the correlation length alone. In this work, we have determined the origin of this enhanced proximity effect via large scale quantum Monte Carlo simulations of helium-4 in a topologically non-trivial geometry that incorporates the important aspects of the experiments. We find that due to the bosonic symmetry of helium-4, identical particle permutations lead to correlations between contiguous spatial regions at a length scale greater than the coherence length. We show that quantum exchange plays a large role in explaining the anomalous experimental results while simultaneously showing how classical arguments fall short of this task.

  9. Thermal resistance at a solid/superfluid helium interface.

    PubMed

    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 (4)He) 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 (4)He 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. PMID:26928639

  10. 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.

  11. Repulsive gravitational effect of a quantum wave packet and experimental scheme with superfluid helium

    NASA Astrophysics Data System (ADS)

    Xiong, Hongwei

    2015-08-01

    We consider the gravitational effect of quantum wave packets when quantum mechanics, gravity, and thermodynamics are simultaneously considered. Under the assumption of a thermodynamic origin of gravity, we propose a general equation to describe the gravitational effect of quantum wave packets. In the classical limit, this equation agrees with Newton's law of gravitation. For quantum wave packets, however, it predicts a repulsive gravitational effect. We propose an experimental scheme using superfluid helium to test this repulsive gravitational effect. Our studies show that, with present technology such as superconducting gravimetry and cold atom interferometry, tests of the repulsive gravitational effect for superfluid helium are within experimental reach.

  12. (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.

  13. 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

  14. One-dimensional electron system over liquid helium

    NASA Astrophysics Data System (ADS)

    Kovdrya, Yu. Z.; Nikolaenko, V. A.; Gladchenko, S. P.

    2000-07-01

    A system close to a one-dimensional (1D) electron system on superfluid helium is realized in the experiments. A profiled substrate with a small dielectric constant is used to create a set of parallel channels on the surface of liquid helium. The mobility of carriers was measured in this system in the temperature range 0.5-1.8 K. For clean substrates the electron mobility increases with decreasing temperature and reaches high values at low temperatures. The results of experiments are found to be in a good agreement with the existing theory.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    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)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.

  17. 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

  18. 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.

  19. 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. PMID:26329210

  20. Superfluid-supercritical helium tradeoff analysis for the Shuttle Infrared Telescope Facility (SIRTF)

    NASA Technical Reports Server (NTRS)

    Gier, H. L.; Stoll, R.; Brooks, W. F.

    1982-01-01

    A comparative study is made of three methods for obtaining the required cooling of the SIRTF. The first is a supercritical helium system in which the 2 K temperatures are obtained by a Joule-Thomson expander; the second is a superfluid (He II) helium system; and the third is a hybrid system in which supercritical helium provides the major cooling and small He II reservoirs supply specific detector cooling. The superfluid helium system is found to offer superior performance; it would be the system to use if funding were available. The comparative study gives equal weight to performance, operations, and cost. From this point of view, the hybrid system is selected as the best compromise to obtain an operational SIRTF.

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

    NASA Astrophysics Data System (ADS)

    He, Yunteng; Zhang, Jie; Kong, Wei

    2016-02-01

    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.

  2. 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. PMID:26931697

  3. Pseudo- ɛ expansion and critical exponents of superfluid helium

    NASA Astrophysics Data System (ADS)

    Sokolov, A. I.; Nikitina, M. A.

    2016-02-01

    The pseudo- ɛ expansions (τ-series) for critical exponents of the three-dimensional XY model describing λ-transition in liquid helium are derived up to the τ6 terms. Numerical estimates extracted from the τ-series obtained using the Padé-Borel resummation technique, scaling relations and the seven-loop (τ7) estimate for the Fisher exponent η are presented including those for the exponents α and ν measured in experiments with a record accuracy. For the exponent α the procedure argued to be most reliable gives α = - 0.0117, the number that is very close to the most accurate experimental values. It signals that the pseudo- ɛ expansion approach is a powerful tool robust enough to evaluate critical exponents with small absolute errors. The arguments in favor of such a robustness are presented.

  4. A Low Power Photoemission Source for Electrons on Liquid Helium

    NASA Astrophysics Data System (ADS)

    Shankar, S.; Sabouret, G.; Lyon, S. A.

    2010-11-01

    Electrons on the surface of liquid helium are a widely studied system that may also provide a promising method to implement a quantum computer. One experimental challenge in these studies is to generate electrons on the helium surface in a reliable manner without heating the cryo-system. An electron source relying on photoemission from a zinc film has been previously described using a high power continuous light source that heated the low temperature system. This work has been reproduced more compactly by using a low power pulsed lamp that avoids any heating. About 5×103 electrons are collected on 1 cm2 of helium surface for every pulse of light. A time-resolved experiment suggests that electrons are either emitted over or tunnel through the 1 eV barrier formed by the thin superfluid helium film on the zinc surface. No evidence of trapping or bubble formation is seen.

  5. 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.

  6. 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.

  7. 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

  8. Quasiequilibrium distribution function of anisotropic phonon systems and the interaction of pulses of low-energy phonons in superfluid helium

    SciTech Connect

    Adamenko, I.N.; Kitsenko, Yu.A.; Nemchenko, K.E.; Slipko, V.A.; Wyatt, A.F.G.

    2005-08-01

    The phenomenon of a hot line forming in liquid helium was observed in experiments carried out in the University of Exeter (UK). It arises when two phonon pulses interact and this is theoretically investigated in this paper. To develop the theory we start from the exact quasiequilibrium distribution function that describes anisotropic phonon systems such as a phonon pulse in superfluid helium. This is related to the approximate distribution function, which is more physically intuitive and was used earlier. The local equilibrium distribution function for phonons in the region of a hot line is obtained from the distribution functions for the phonons in the two interacting pulses. In order to explain the results of experiments, we analyze the effect of different pressures when the angle between the two moving pulses in superfluid helium is constant and also the effect of different angles at the saturated vapor pressure. The conditions suitable for the creation of a hot line are found. The results of the calculations are compared with the experimental data.

  9. 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.

  10. Multipurpose top for liquid helium Dewar

    NASA Technical Reports Server (NTRS)

    Murphy, R. S.; Anderholm, J. R.

    1972-01-01

    Multipurpose top was fabricated for liquid helium Dewar flask which guards against flash vaporization of liquid helium and allows boiling temperature of liquid helium to be lowered by reduction of ambient pressure in Dewar flask. Device is rugged and simple, and does not require frequent calibrations or adjustments.

  11. A design and critical technology issues for on-orbit resupply of superfluid helium

    NASA Technical Reports Server (NTRS)

    Hopkins, Richard A.; Mord, Allan J.

    1990-01-01

    The issues of and the solutions to the critical design and technology areas of the Superfluid Helium On-Orbit Transfer (SHOOT) experiment, presently under development at the NASA Goddard Spaceflight Center, are discussed. Special attention is given to the SHOOT design requirements for the 10,000-liter superfluid He resupply tanker system, the concept details of the system, and the resupply operations and their analysis. A block diagram of the SHOOT system is included along with fluid management schematic and configuration diagrams of the system and its subsystems. A summary of the dewar performance is also presented.

  12. 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.

  13. 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.

  14. Superfluid Helium Testing of a Stainless Steel to Titanium Piping Transition Joint

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    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.

  15. 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.

  16. Specifications and Performances of Series Superfluid Helium Safety Relief Valves for the LHC

    NASA Astrophysics Data System (ADS)

    Perin, A.; Fontanive, V.

    2006-04-01

    Protecting the LHC magnets requires safety relief valves operating with 1.9 K pressurized superfluid helium at their inlet. Following the evaluation of prototype valves, a specification for the production of the 360 safety relief valves needed for the LHC was issued. The production of the safety valves was then awarded to an industrial contractor. The performances of pre-series valves were assessed for a variety of aspects including thermal performance, leak tightness in superfluid helium, dynamic behavior and resistance to intensive mechanical cycling. After the initial validation phase the series production was completed within the technical requirements of the specification. This paper describes the characteristics of the safety relief valves and the specifications for their industrial production. The performances of the pre-series valves are presented and an overview of the series production phase is given.

  17. In situ radiation test of silicon and diamond detectors operating in superfluid helium and developed for beam loss monitoring

    NASA Astrophysics Data System (ADS)

    Kurfürst, C.; Dehning, B.; Sapinski, M.; Bartosik, M. R.; Eisel, T.; Fabjan, C.; Rementeria, C. A.; Griesmayer, E.; Eremin, V.; Verbitskaya, E.; Zabrodskii, A.; Fadeeva, N.; Tuboltsev, Y.; Eremin, I.; Egorov, N.; Härkönen, J.; Luukka, P.; Tuominen, E.

    2015-05-01

    As a result of the foreseen increase in the luminosity of the Large Hadron Collider, the discrimination between the collision products and possible magnet quench-provoking beam losses of the primary proton beams is becoming more critical for safe accelerator operation. We report the results of ongoing research efforts targeting the upgrading of the monitoring system by exploiting Beam Loss Monitor detectors based on semiconductors located as close as possible to the superconducting coils of the triplet magnets. In practice, this means that the detectors will have to be immersed in superfluid helium inside the cold mass and operate at 1.9 K. Additionally, the monitoring system is expected to survive 20 years of LHC operation, resulting in an estimated radiation fluence of 1×1016 proton/cm2, which corresponds to a dose of about 2 MGy. In this study, we monitored the signal degradation during the in situ irradiation when silicon and single-crystal diamond detectors were situated in the liquid/superfluid helium and the dependences of the collected charge on fluence and bias voltage were obtained. It is shown that diamond and silicon detectors can operate at 1.9 K after 1×1016 p/cm2 irradiation required for application as BLMs, while the rate of the signal degradation was larger in silicon detectors than in the diamond ones. For Si detectors this rate was controlled mainly by the operational mode, being larger at forward bias voltage.

  18. Measurement of the lifetime of excited-state electron bubbles in superfluid helium

    SciTech Connect

    Ghosh, Ambarish; Maris, Humphrey J.

    2005-08-01

    We report on the measurement of the lifetime of bubbles in superfluid helium that contain an electron in the 1P state. The 1P bubbles are produced by laser excitation of ground-state bubbles, and are detected by ultrasonic cavitation. Our measurements show that the lifetime of these excited bubbles is much less than the calculated lifetime for radiative decay and, hence, is determined by a nonradiative mechanism.

  19. 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

  20. Electron bubbles in helium clusters. II. Probing superfluidity.

    PubMed

    Rosenblit, Michael; Jortner, Joshua

    2006-05-21

    In this paper we present calculations of electron tunneling times from the ground electronic state of excess electron bubbles in ((4)He)(N) clusters (N=6500-10(7), cluster radius R=41.5-478 A), where the equilibrium bubble radius varies in the range R(b)=13.5-17.0 A. For the bubble center located at a radial distance d from the cluster surface, the tunneling transition probability was expressed as A(0)phi(d,R)exp(-betad), where beta approximately 1 A(-1) is the exponential parameter, A(0) is the preexponential factor for the bubble located at the cluster center, and phi(d,R) is a correction factor which accounts for cluster curvature effects. Electron tunneling dynamics is grossly affected by the distinct mode of motion of the electron bubble in the image potential within the cluster, which is dissipative (i.e., tau(D)tau(0)) in superfluid ((4)He)(N) clusters, where tau(D) is the bubble motional damping time (tau(D) approximately 4 x 10(-12) s for normal fluid clusters and tau(D) approximately 10 s for superfluid clusters), while tau(0) approximately 10(-9)-10(-10) s is the bubble oscillatory time. Exceedingly long tunneling lifetimes, which cannot be experimentally observed, are manifested from bubbles damped to the center of the normal fluid cluster, while for superfluid clusters electron tunneling occurs from bubbles located in the vicinity of the initial distance d near the cluster boundary. Model calculations of the cluster size dependence of the electron tunneling time (for a fixed value of d=38-39 A), with lifetimes increasing in the range of 10(-3)-0.3 s for N=10(4)-10(7), account well for the experimental data [M. Farnik and J. P. Toennies, J. Chem. Phys. 118, 4176 (2003)], manifesting cluster curvature effects on electron tunneling dynamics. The minimal cluster size for the dynamic stability of the bubble was estimated to be N=3800, which represents the

  1. 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.

  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. PMID:27448887

  3. Grüneisen parameter for gases and superfluid helium

    NASA Astrophysics Data System (ADS)

    de Souza, Mariano; Menegasso, Paulo; Paupitz, Ricardo; Seridonio, Antonio; Lagos, Roberto E.

    2016-09-01

    The Grüneisen ratio (Γ), i.e. the ratio of the thermal expansivity to the specific heat at constant pressure, quantifies the degree of anharmonicity of the potential governing the physical properties of a system. While Γ has been intensively explored in solid state physics, very little is known about its behavior for gases. This is most likely due to the difficulties posed in carrying out both thermal expansion and specific heat measurements in gases with high accuracy as a function of pressure and temperature. Furthermore, to the best of our knowledge a comprehensive discussion about the peculiarities of the Grüneisen ratio is still lacking in the literature. Here we report on a detailed and comprehensive overview of the Grüneisen ratio. Particular emphasis is placed on the analysis of Γ for gases. The main findings of this work are: (i) for the van der Waals gas Γ depends only on the co-volume b due to interaction effects, it is smaller than that for the ideal gas (Γ = 2/3) and diverges upon approaching the critical volume; (ii) for the Bose–Einstein condensation of an ideal boson gas, assuming the transition as first-order, Γ diverges upon approaching a critical volume, similarly to the van der Waals gas; (iii) for 4He at the superfluid transition Γ shows a singular behavior. Our results reveal that Γ can be used as an appropriate experimental tool to explore pressure-induced critical points.

  4. A Structured Approach to Analyze the Influence of Channel Dimensions on Heat Extraction via Superfluid Helium

    NASA Astrophysics Data System (ADS)

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

    For the luminosity upgrade of the LHC at CERN, the final focusing quadrupole magnets will be exposed to an increased energy deposition in their coil windings. To have a higher heat transfer rate between cable and superfluid helium bath, the cable insulation has been subject of many studies. Improved cable insulation designs, making use of several layers of Kapton tape wound around Rutherford type cables, allow helium to penetrate via micro-channels, which are left open between adjacent Kapton tape sections. To better understand the thermal behaviour at operating temperatures below and some degrees above the helium lambda transition, besides experimental work, several numerical models have been developed to study the influence of the cable insulation. Here we present a new numerical model based on an earlier presented FEM model, which makes use of coupling variables such that the user can easily and quickly change the parameters of interest, giving the possibility to analyse new ideas effectively.

  5. Exotic Self-trapped States of an Electron in Superfluid Helium

    NASA Astrophysics Data System (ADS)

    Elser, Veit

    2015-09-01

    We explore the possibility that the fast and exotic negative ions in superfluid helium are electrons bound to quantized vortex structures, the simplest being a ring. In the states we consider, the electron energy is only slightly below the conduction band minimum of bulk helium. To support our proposal, we present two calculations. In the first, we show that the electron pressure on the vortex core is insufficient to cavitate the helium and form an electron bubble. In the second, we estimate the equilibrium radius of the vortex ring that would bind an electron and find it is much smaller than the electron bubble, about 7 Å. The many exotic ions reported in experiments might be bound states of an electron with more complex vortex structures.

  6. Thermionic emission and a novel electron collector in a liquid helium environment.

    PubMed

    Fang, J; Dementyev, Anatoly E; Tempere, Jacques; Silvera, Isaac F

    2009-04-01

    We study two techniques to create electrons in a liquid helium environment. One is thermionic emission of tungsten filaments in a low temperature cell in the vapor phase with a superfluid helium film covering all surfaces; the other is operating a glowing filament immersed in bulk liquid helium. We present both the steady state and rapid sweep I-V curves and the electron current yield. These curves, having a negative dynamic resistance region, differ remarkably from those of a vacuum tube filament. A novel low temperature vapor-phase electron collector for which the insulating helium film on the collector surface can be removed is used to measure emission current. We also discuss our achievement of producing multielectron bubbles in liquid helium by a new method. PMID:19405669

  7. Performance of the relativity mission superfluid helium flight dewar

    NASA Astrophysics Data System (ADS)

    Parmley, R. T.; Bell, G. A.; Frank, D. J.; Murray, D. O.; Whelan, R. A.

    2003-10-01

    The world's largest capacity helium flight dewar has been assembled for use on the Relativity Mission, also known as Gravity Probe-B (GP-B). Acceptance tests performed include (1) weight, (2) proof pressure and leak checks, (3) vacuum bakeout, (4) main tank fill with He I, (5) parasitic heat rate tests, (6) well fill with He I from both the main tank and an external supply dewar, (7) well depletion, (8) conditioning the main tank to He II, (9) porous plug tests, (10) heat pulse meter tests, (11) transferring He II from the main tank to the well with a fountain-effect pump, (12) guard tank fill with He I with a nonvented He II main tank simulating launch pad hold, and (13) guard tank emptying. The measured performance is compared to the previously launched IRAS, COBE, and ISO cryostats. The Relativity Mission spacecraft will be launched in the time span 1999 to 2000.

  8. 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.

  9. 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.

  10. A Continuous 4He Refrigerator for Use in a Superfluid Helium Bath

    SciTech Connect

    Wang, Suwen; Avaloff, D.; Nissen, J. A.; Stricker, D. A.; Lipa, J. A.

    2006-09-07

    In cryogenic applications in space, the base temperature, Tmin of the helium bath in the dewar is typically determined by the design of the porous plug and the associated plumbing. For certain experiments, the required operating temperature of the instrument is lower than the bath temperature. In the laboratory, temperatures below 1.2 K require very large pumps or the use of 3He systems. We have demonstrated a modified 4He refrigerator with a continuous fill from a superfluid helium bath with a base temperature more than 0.5 K below the bath temperature. We describe the operation as well as the mechanism of such a refrigerator. For operation in space the refrigerator would need to be equipped with a porous plug to retain the fluid.

  11. 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.

  12. 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.

  13. Numerical simulation of cavitating flow of liquid helium in venturi channel

    NASA Astrophysics Data System (ADS)

    Ishimoto, Jun; Kamijo, Kenjiro

    2003-01-01

    The fundamental characteristics of the two-dimensional cavitating flow of liquid helium through a venturi channel near the lambda point are numerically investigated to realize the further development and high performance of new multi-phase superfluid cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though venturi channel is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid-to-gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.

  14. Numerical Analysis of Cavitating Flow of Liquid Helium inHorizontal Converging-Diverging Channel

    NASA Astrophysics Data System (ADS)

    Ishimoto, Jun; Kamijo, Kenjiro

    The basic characteristics of the two-dimensional cavitating flow of liquid helium through a horizontal converging-diverging channel near the lambda point are numerically investigated to realize the further development and high performance of new multiphase superfluid cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multifluid model with generalized curvilinear coordinates system are presented, and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though horizontal converging-diverging channel is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermo mechanical effect is conspicuous in the large gas phase volume fraction region where the liquid- to gas-phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.

  15. Numerical simulation of cavitating flow of liquid helium in a pipe using multi-fluid model

    NASA Astrophysics Data System (ADS)

    Ishimoto, J.; Oike, M.; Kamijo, K.

    2002-05-01

    The two-dimensional characteristics of the cavitating flow of liquid helium in a pipe are numerically investigated to realize the further development and high performance of new cryogenic engineering applications. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model are presented and several flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the turbulent cavitating flow of liquid helium passing through the orifice is shown in detail, and it is also found that the phase transition of the normal fluid to the superfluid and the generation of superfluid counterflow against normal fluid flow are conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase. According to these theoretical results, the fundamental characteristics of the cryogenic cavitating flow are predicted.

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

    NASA Astrophysics Data System (ADS)

    Koettig, T.; Peters, B. J.; Avellino, S.; Junginger, T.; Bremer, J.

    2015-12-01

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

  17. Superfluid helium-4: On sin phi Josephson weak links and dissipation of third sound

    NASA Astrophysics Data System (ADS)

    Hoffman, Joan Audrey

    2005-11-01

    This dissertation reports on two different projects---the development of an experiment designed to study weak links in 4He with a sine-like current-phase relationship and a set of experiments exploring dissipation of third sound in thick films of superfluid 4He. Since Brian Josephson's proposals of phenomena in weakly-linked macroscopic quantum systems over 40 years ago, researchers have been searching for such effects in superfluid 4He. Until recently, it has been believed that technological barriers would prevent the observation of a sine-like current-phase relationship between two weakly linked volumes of superfluid 4He. In this dissertation we report on the fabrication of sub-15nm aperture arrays and preliminary measurements helium flow through the arrays below Tlambda . These measurements show the linear temperature dependence of critical velocity expected in the phase slip regime. Efforts to study the cross-over to the sin φ regime are ongoing. We measured the frequency and line shapes of third sound resonances at temperatures between 0.3 and 2.1K in saturated films approximately 30nm thick, and, from these measurements, calculated the attenuation of the third sound waves. In the past, such measurements have been inconsistent, within as well as among reported work. More recent theory, however, suggests that these variations may point toward vortex-driven dissipation mechanisms. Metastable vortex populations are known to permeate superfluid 4He. Our measurements indicate that attenuation is a strong function of the history of the film, affected by temperature excursions and physical perturbations. We also observe frequency shifting of resonances attributable to trapped circulation and a large increase in dissipation with the introduction of 3He impurities to the film. Taken together with our observation of a dissipation mechanism linear in amplitude, our results provide support for recent proposals of dissipation due to vortex-excitation interactions.

  18. 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.

  19. Magnetotransport in a quasi-one-dimensional electron system on superfluid helium

    NASA Astrophysics Data System (ADS)

    Nikolaenko, B. A.; Kovdrya, Yu. Z.; Gladchenko, S. P.

    2002-11-01

    Magnetotransport in a nondegenerate quasi-one-dimensional electron system on superfluid helium is investigated experimentally. The measurements are performed in perpendicular magnetic fields B⩽2.6 T in the temperature range 0.48-2.05 K with 100-400 nm wide conducting channels. In the region where the carriers are scattered by the helium atoms in the vapor (T>0.9 K) and in the region where the electrons are scattered by ripplons (T<0.9 K) the longitudinal component ρxx of the magnetoresistance of the conducting channels predominantly increases with B. The experimental data in the region of carrier scattering by helium atoms in the vapor agree with the classical Drude law, and in the quantum transport regime with ωcτ>1 (ωc is the cyclotron frequency and τ is the relaxation time of the electron system) the self-consistent Born approximation for a 2D electron system above helium gives a qualitative explanation of the data. It is conjectured that the quantitative differences between the experimental data and the theoretical calculations are due to the difference of the specific features between the experimentally studied and theoretically analyzed systems. The experimental values of the electron mobilities at low temperatures and in weak magnetic fields agree with theoretical calculations for a quasi-one-dimensional system. Weak carrier localization in the experimental electron system explains the negative magnetoresistance of the conducting channels, which was observed in the gas and ripplon carrier scattering regions.

  20. 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.

  1. Sintered plug flow modulation of a vapor-liquid phase separator for a helium II vessel

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Chuang, C.; Kamioka, Y.; Lee, J. M.; Yuan, S. W. K.

    1984-01-01

    Presented is a system for modulation of a superfluid (helium II) flow in a vapor-liquid phase separator, for use in cryogenic storage tanks in future space missions. The system consists of a semicircular mechanically operated shutter, downstream of the separator plug, rotated at 0.1 rpm to control the operational surface area of the separator. The mass flow rate was varied from 10 to 22 mg/s. Pressure gradients across the plug are also discussed.

  2. 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.

  3. 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

    2014-04-01

    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. PMID:26274451

  4. 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

  5. Photo-induced isomerization and chemical reaction dynamics in superfluid helium droplets

    NASA Astrophysics Data System (ADS)

    Merritt, Jeremy; Douberly, Gary; Miller, Roger

    2008-03-01

    Near threshold photo-induced isomerization and photo-induced chemical reactions have long been sough after as sensitive probes of the underlying potential energy surface. One of the most important questions asked is how the initially bright quantum state couples to the reaction coordinate, and thus relates to energy transfer in general. Helium droplets have now allowed us to stabilize entrance channel clusters behind very small reaction barriers such that vibrational excitation may result in reaction. Through two examples, namely the isomerization of the 2 binary complexes of HF-HCN Douberly et al. PCCP 2005, 7,463, and the induced reaction of the gallium-HCN complex Merritt et al. JPCA 2007, DOI:10.1021/jp074981e we will show how the branching ratios for reaction and predissociation can determined and the influence of the superfluid He solvent.

  6. Cryogenic Microjet Source for Orthotropic Beams of Ultralarge Superfluid Helium Droplets

    NASA Astrophysics Data System (ADS)

    Grisenti, Robert E.; Toennies, J. Peter

    2003-06-01

    Liquid 4He at pressures P0=0.5 30 bars and temperatures T0=1.5 4.2 K is discharged into vacuum through two different 2 μm nozzles. The velocities of the beam of particles obey the Bernoulli equation down to 15 m/sec. With decreasing T0 and increasing P0 the velocity and angular distributions become exceedingly narrow with Δv/v≲1% and Δϑ≲1 mrad. Optical observations indicate that the beam consists of micron-sized droplets (N≳109 atoms). This new droplet source provides opportunities for novel experimental studies of superfluid behavior.

  7. 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.

  8. 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.

  9. Visualization study of the normal-fluid motion in superfluid helium-4

    NASA Astrophysics Data System (ADS)

    Gao, Jian; Marokov, Alex; Guo, Wei; van Sciver, Steven W.; Ihas, Gary G.; McKinsey, Daniel N.; Vinen, William F.

    2014-03-01

    Flow visualization in superfluid 4He is challenging, yet crucial for attaining a detailed understandingof quantum turbulence. Two problems have impeded progress: finding and introducing suitable tracersthat are small yet visible; and unambiguous interpretation of the tracer motion. Metastable He2 triplet molecules form angstrom-sized bubbles in helium and can be imaged using a laser-induced-fluorescence technique. At temperatures above 1 K, helium molecules solely follow the motion of the normal-fluid component without being affected by quantized vortices. In our recent experiments on thermal counterflow, by tracing a thin molecular line created via femtosecond-laser field-ionization technique, we are able to measure the instantaneous normal-fluid velocity field. We show that the obtained velocity probability density function (PDF) obeys a Gaussian distribution. We also discuss the calculated structure function of the novel normal-fluid turbulence in thermal counterflow. The work is supported by the start-up grant of W.G. provided by the National High Magnetic Field Laboratory and Florida State University.

  10. The spin diffusion in normal and superfluid Fermi liquids

    SciTech Connect

    Einzel, D. )

    1991-09-01

    Spin diffusion in paramagnetic spin systems is a dissipative process that acts so as to remove all spatial variation of the magnetization. In normal and superfluid Fermi liquids its physical origin lies in the nonconservation property of the macroscopic magnetization current associated with the thermal excitations, the Landau and Bogolyubov quasi-particles, respectively. In the hydrodynamic limit, this dissipative process manifests itself in a constitutive relation connecting the decaying magnetization current with gradients in the magnetization density via a coefficient of spin diffusion. Exchange contributions to the quasi-particle interaction introduce, in addition, reactive processes, which can be associated with a rotation of the quasi-particle spin current about the direction of the spin polarization. This so-called spin current rotation - or Leggett-Rice effect - leads to nonhydrodynamic behavior of the spin diffusion whenever the exchange frequency becomes comparable to the inverse spin-current relaxation time. This article reviews the current understanding of diffusional spin transport, as influenced by nonhydrodynamic effects, in normal and superfluid Fermi systems.

  11. Low temperature uses of helium

    NASA Technical Reports Server (NTRS)

    Brown, G. V.

    1970-01-01

    Helium is used for purging and pressurizing cryogenic rocket propellants, welding, atmosphere control, leak detection, and refrigeration. It provides the lowest possible liquid-bath temperature and produces superconductivity in certain materials. Its superfluid effects are used in superconducting magnets.

  12. Numerical Simulation of Cavitating Flow of Liquid Helium in a Vertical Converging-Diverging Nozzle

    NASA Astrophysics Data System (ADS)

    Ishimoto, J.; Kamijo, K.

    2004-06-01

    The basic characteristics of the two-dimensional cavitating flow of liquid helium through a vertical converging-diverging nozzle near the lambda point are numerically investigated to realize the further development and high performance of new multiphase He II cooling systems. First, the governing equations of the cavitating flow of liquid helium based on the unsteady thermal nonequilibrium multi-fluid model with generalized curvilinear coordinates system are presented, and several multiphase flow characteristics are numerically calculated, taking into account the effect of superfluidity. Based on the numerical results, the two-dimensional structure of the cavitating flow of liquid helium though a vertical converging-diverging nozzle is shown in detail, and it is also found that the generation of superfluid counterflow against normal fluid flow based on the thermomechanical effect is conspicuous in the large gas phase volume fraction region where the liquid to gas phase change actively occurs. Furthermore, it is clarified that the mechanism of the He I to He II phase transition caused by the temperature decrease is due to the deprivation of latent heat for vaporization from the liquid phase.

  13. THERMAL OSCILLATIONS IN LIQUID HELIUM TARGETS.

    SciTech Connect

    WANG,L.; JIA,L.X.

    2001-07-16

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

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Huisken, Friedrich; Krasnokutski, Serge A.

    2012-11-01

    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 4He 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 O2. 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.

  17. 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).

  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. Superfluidity, BEC, and dimensions of liquid 4He in nanopores

    NASA Astrophysics Data System (ADS)

    Markić, L. Vranješ; Glyde, H. R.

    2015-08-01

    We present 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. Liquid 4He in nanopores represents a dense Bose liquid at reduced dimension and in disorder. The goal is to determine the effective dimensions of the liquid in the pores. It is to test whether observed properties, such as a very low onset temperature for superflow, Tc, can be predicted by a standard, static PIMC ρS/ρ . We simulate a cylinder of liquid of diameter dL surrounded by 5 Å of inert solid 4He in a nanopore of diameter d ; d =dL+10 Å . We find a PIMC ρS(T ) /ρ and OBDM that scales as a 1D fluid Luttinger liquid at extremely small liquid pore diameters only, dL=6 Å . At this dL, the liquid fills the pore in a 1D line at the center of the pore and there is no PIMC superflow. In the range 8 ≤dL≤22 Å the PIMC ρS(T ) /ρ scales as a 2D liquid. In this dL range the liquid fills the pores in 2D-like cylindrical layers. The crossover from no superflow at d =16 Å to superflow at d ≥18 Å agrees with experiment. There is a crossover 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 that obtained from ρS(T ) /ρ . These results suggest that the superflow observed in small pore media is standard static superflow with the low Tc arising from its 2D character. An operational onset temperature, TBEC, for BEC can be defined as the temperature at which there is a crossover from exponential to algebraic decay in the OBDM. This definition leads to a TBEC≥Tc as observed in larger pore media.

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

    NASA Astrophysics Data System (ADS)

    La Mantia, Marco

    2016-02-01

    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/m2 and 500 W/m2. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Separator plugs for liquid helium

    NASA Technical Reports Server (NTRS)

    Lee, J. M.; Yuan, S. W. K.; Hepler, W. A.; Frederking, T. H. K.

    1984-01-01

    Work performed during Summer 1984 (from June to Sept. 30) in the area of porous media for use in low temperature applications is discussed. Recent applications are in the area of vapor - liquid phase separation, pumping based on the fountain effect and related subsystems. Areas of potential applications of the latter are outlined in supplementary work. Experimental data have been developed. The linear equations of the two-fluid model are inspected critically in the light of forced convection evidence reported recently. It is emphasized that the Darcy permeability is a unique throughput quantity in the porous media application areas whose use will permit meaningful comparisons of data not only in one lab but also within a group of labs doing porous plug studies.

  5. Properties of slowly rotating helium II and the superfluidity of pulsars

    SciTech Connect

    Tsakadze, J.S.; Tsakadze, S.J.

    1980-06-01

    Results of an experimental study of superfluid He II properties in the nonstationary rotation regime are presented. On the basis of an analysis of the experimental data it is shown that the behavior of pulsar rotation (sudden jumps in speed, long relaxation processes) can be explained on the basis of the assumption of neutron superfluid in pulsars.

  6. Observation of a New Type of Negative Ion in Superfluid Helium

    SciTech Connect

    Ghosh, Ambarish; Maris, Humphrey J.

    2006-09-07

    In recent work, we have developed a new technique for the study of the properties of electron bubbles (negative ions) in liquid helium. We use ultrasound to measure the critical negative pressure Pc at which an electron bubble becomes unstable and explodes. The value of Pc is affected, for example, by the quantum state of the electron and is reduced if the bubble is attached to a quantized vortex. In the present experiments, we have discovered a new type of object that appears to be larger than the usual electron bubble. We will consider possible explanations of these observations.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We have measured the quality factor Q and the frequency f of a 32-kHz quartz tuning fork immersed in liquid ^4 He 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Simulation of temperature profiles at the superfluid to normal-fluid interface in helium-4 for prediction of temperature measurement accuracy

    SciTech Connect

    Hensinger, D.M.; Gianoulakis, S.E.; Duncan, R.V.

    1996-12-31

    The purpose of this work was to model the conditions in a test cell containing normal-fluid and superfluid helium-4 and to predict the accuracy of temperature measurements made on this system in the presence of non-ideal wall materials and probe geometries. A thermal model of helium-4 in the vicinity of its normal-fluid to superfluid transition temperature was used to calculate the temperature profiles within a helium-4 filled experimental test cell. Calculated temperature profiles were used to predict the temperature measurement accuracy which could be expected from a test cell and temperature probe design. The superfluid phase of helium-4 was represented as a highly-conductive, diffusive material to approximate a superconductor of heat. The thermal model included the influences of temperature, heat flux, and hydrostatic pressure on the properties of helium-4. The model was solved for quasi-static temperature profiles using a finite element method and employing a transformed and expanded temperature scale to allow resolution of nK/cm temperature gradients in the presence of a 2 K absolute temperature.

  14. Liquid?solid helium interface: some conceptual questions

    NASA Astrophysics Data System (ADS)

    Leggett, A. J.

    2003-12-01

    I raise, and discuss qualitatively, some conceptual issues concerning the interface between the crystalline solid and superfluid liquid phases of 4He emphasizing, in particular, the fact that the ground-state wave functions of the two phases are prima facie qualitatively quite different, in that the superfluid liquid phase possesses off-diagonal long-range order (ODLRO), while the crystalline solid does not. The fact that the statics and dynamics of the interface do not appear to be particularly sensitive to the presence of ODLRO in the liquid is tentatively explained by the fact that because of a subtlety associated with the Bose statistics obeyed by the atoms, the solid and liquid wave functions are not locally very different.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

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

    DOE PAGESBeta

    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 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

  18. 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.

  19. 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.

  20. 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

  1. Lambda Front Propagation in the Superfluid Helium Contained in the External Auxiliary Bus-Bar Line of the LHC

    NASA Astrophysics Data System (ADS)

    Capatina, O.; Poncet, A.; Skoczen, B.

    2004-06-01

    The array of the corrector magnets of the LHC arc, associated with the main and some dispersion suppressor quadrupoles are powered by a special line routed inside the cryostat, running alongside the cold mass of the half-cell. This line, composed of a 50 mm diameter stainless steel tube fixed to the cold mass, houses the superconducting multi-wire cable(s) carrying the 600 A and 6 kA current to the corrector magnets and special quadrupoles. It is cooled down to 1.9 K with pressurized superfluid helium provided by links to the cold-mass placed at regular intervals (one half-cell). The paper is focused on the process of sub-cooling the long channel from 4.5 K down to 1.9 K, including the propagation of the lambda front along the pipeline. The mechanism of sub-cooling is based on a zone of phase transformation traveling along the channel, with the heat transport both in helium and in the copper wires. A new 2-D model, including the radial heat exchange between copper and He II, has been used to study the process. A clamped temperature problem with a jump-like variable section of the channel has been solved. The model has been applied to the analysis of recovery of the line after a quench in the main magnets. A comparison with the measurements in the LHC prototype cell (String 2) is shown.

  2. 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}.

  3. 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.

  4. 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.

  5. 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.

  6. Infrared spectroscopy of HOCl embedded in superfluid helium nanodroplets: Probing the dynamical response of the solvent

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Kelloway, Donald D.; Jäger, Wolfgang

    2012-07-01

    The rotationally resolved depletion spectrum of hypochlorous acid embedded in helium nanodroplets in the 2.8 μm region is reported. The narrow a-type lines are asymmetrically skewed in the direction of the band origin, and an analysis of their line shapes based on the chirped damped oscillator function introduced by van Staveren and Apkarian [J. Chem. Phys. 133, 054506 (2010)., 10.1063/1.3469816] yields a response time of the helium solvent of 1 ns. The b-type lines are much broader due to the greater number of droplet states available for relaxation of the excited rotational states.

  7. 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.

  8. Effect of Kapitza resistance on standing surface waves in superfluid helium

    SciTech Connect

    Atkin, R.J.; Fox, N.

    1984-06-01

    We analyze theoretically the resonant frequencies of standing surface waves produced by second sound in /sup 4/He. In particular, we show that an empirical heat transfer coefficient involved in a recently proposed boundary condition can be related to Kapitza resistance. We also calculate the heat flux within the helium and deduce that the height of the surface waves is strongly frequency dependent.

  9. 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.

  10. Experiments on the rapid mechanical expansion of liquid 4He through its superfluid transition.

    PubMed

    Efimov, V B; Griffiths, O J; Hendry, P C; Kolmakov, G V; McClintock, P V E; Skrbek, L

    2006-11-01

    Phenomena following a rapid mechanical quench of liquid 4He from its normal to its superfluid phase are reported and discussed. The mechanical expansion apparatus is an improved version of that described previously. It uses a double-cell geometry to effect a partial separation of the sample from the convolutions of the bellows that form the outer wall of the cell. Consistent with earlier work, no evidence is found for the production of quantized vortices via the Kibble-Zurek (KZ) mechanism. Although the expansion is complete within 15ms , the second-sound velocity and attenuation continue to increase for a further approximately 60ms ; correspondingly the temperature decreases. Subsequently, the temperature rises again toward its final value as the second-sound velocity and attenuation decrease. It is shown that this unexpected behavior is apparently associated with a large-amplitude second-sound oscillation produced by the expansion, and it is suggested that the observed vortices are created by the normal fluid-superfluid counterflow that constitutes the second-sound wave. If production of large-amplitude second sound is inherent to the mechanical expansion of liquid 4He through the superfluid transition, as appears to be the case for final temperatures more than 3mK from the lambda transition, the phenomenon sets a lower bound on the density of KZ vortices that can be detected in this type of experiment. PMID:17279991

  11. 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.

  12. 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}.

  13. 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

    2013-06-01

    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). PMID:23758376

  14. 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.

  15. Density functional theory simulation of liquid helium-4 in aerogel

    NASA Astrophysics Data System (ADS)

    Lysogorskiy, Yu. V.; Tayurskii, D. A.

    2013-10-01

    The distribution of liquid 4He in different types of confinements—adsorbing and nonadsorbing aerogel on the basis of silicon dioxide SiO2 and an absorbing homogeneous strand—has been studied using the density functional theory. It has been demonstrated that the helium atoms tend to be adsorbed on the concave aerogel surface. It has been shown that, in the confinement with fractional mass dimension within certain scales, liquid helium also has a fractional mass dimension within these scales. The dependence of the energy of liquid helium on the number of atoms has been studied for different types of adsorbing surfaces. It has been established that the specific energy of liquid helium behaves differently in the cases of attractive and unattractive potentials with decreasing number of particles. This indicates that the system under consideration is nonextensive. Thus, the necessity of taking into account the surface effects and the fractional mass dimension in the studies of the properties of liquid helium in the restricted space geometry has been demonstrated.

  16. Ultrasonic Measurements on Superconducting Uranium -PLATINUM(3) and Superfluid HELIUM-3

    NASA Astrophysics Data System (ADS)

    Adenwalla, Shireen

    We present ultrasonic measurements on two highly correlated systems, UPt_3 and ^3He. We have measured the ultrasonic attenuation in superconducting UPt_3 as a function of field and temperature. An anomalous peak has been observed in the longitudinal ultrasonic attenuation in both field and temperature sweeps. We interpret this peak as a signature of a phase transition in the mixed state of UPt _3 which is strong evidence for unconventional superconductivity. We present phase diagrams in the field -temperature plane for different orientations of field. The peak shifts to lower fields as the temperature is increased, roughly tracking H_{c2} . The position of the peak in the field sweep is found to depend strongly on the orientation of the field relative to the c-axis. In contrast to the behavior of H_{c2}, we find that the phase line shifts to lower fields as the field is rotated away from the c-axis into the basal plane. The temperature dependence of the attenuation in zero field goes as T^2, unlike the expected exponential temperature dependence. The ultrasonic measurements on superfluid ^3He investigated the J = 2 collective modes. We have used a new technique involving alternate pressure and temperature sweeps. The results agree reasonably well with previously collected data.

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

    SciTech Connect

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

    1984-09-24

    The first shock-compression experiments on liquid helium are reported. With a two-stage light-gas gun, liquid He at 4.3 K and 1 atm was shocked to 16 GPa and 12 000 K and double shocked to 56 GPa and 21 000 K. Liquid perturbation theory has been used to determine an effective interatomic potential from which the equation of state of He can be obtained over a wide range of densities and temperatures.

  18. 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.

  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. 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

  1. Superconductive thin film makes convenient liquid helium level sensor

    NASA Technical Reports Server (NTRS)

    Becker, H. H.

    1968-01-01

    Sensor consisting of superconductive film mounted on a dipstick measures the level of liquid helium in a Dewar flask. The sensor is made by depositing a thin film of niobium metal to a thickness of 2000 angstroms on a quartz substrate, which is then mounted on a graduated dipstick.

  2. Microscopic molecular superfluid response: theory and simulations.

    PubMed

    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. PMID:24647079

  3. 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.

  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. Superfluid helium cryogenics for the large hadron collider project at CERN

    NASA Astrophysics Data System (ADS)

    Lebrun, Philippe

    The Large Hadron Collider (LHC) at CERN will be the next research instrument of high-energy physics. Colliding protons at 14 TeV center-of-mass energy and high luminosity, it will probe the structure of matter down to an unprecedentedly fine scale, thus allowing to reproduce in the laboratory phenomena which occurred in the very early universe. On the technological side, the LHC makes use of high-field superconducting magnets for guidance and focusing of the particle beams around the 26.7 km circumference of the machine, to be installed in the existing LEP tunnel. The nominal bending field of 8.65 T is produced in some 1300 twin-aperture dipoles, wound with small-filament Nb sbnd Ti conductor, and operated below 1.9 K in static baths of pressurized helium II, thus taking advantage of its specific properties as cooling fluid. We present the main technical challenges of the LHC cryogenic system, and review the actions of development and the preparatory work in progress.

  6. Photoinduced molecular dissociation and photoinduced recombination mediated by superfluid helium nanodroplets.

    PubMed

    Kautsch, Andreas; Koch, Markus; Ernst, Wolfgang E

    2015-05-14

    We have investigated photoinduced chemical reaction dynamics of cold, isolated Cr2 molecules in helium nanodroplets (HeN), exploiting the quantum state specific spatial separation of solvated and surface locations on the droplet. The molecules are excited to achieve dissociation to a ground state (a(7)S3) and a metastable state (a(5)S2) atom. State specific spatial separation, in combination with efficient translational cooling to avoid ejection, causes the ground state atom to be solvated inside the droplet while the metastable atom migrates to the surface. A barrier between the two reactants formed by the HeN prevents recombination. We apply a resonance-enhanced multiphoton ionization scheme including the y(5)P°(1,2,3) <-- a(5)S(2) transition of the surface atom as well as a two-laser scheme including the y(7)P°(2,3,4) <-- a(7)S(3) transition of the solvated atom in order to verify the locations and separation of the dissociation products. Furthermore, ionization of the a(5)S2 surface atom triggers solvation followed by geminate recombination with the a(7)S3 atom, which is verified by the detection of Cr2(+) molecular ions. For small Cr clusters, our results indicate that they may be composed of chromium dimers that exhibit the same dissociation behavior. PMID:25894482

  7. Optimized He 2 cooling systems for space application. Behavior and handling of superfluid helium at G = 0, phase 1

    NASA Astrophysics Data System (ADS)

    Denner, H. D.; Klipping, G.; Lueders, K.; Schotte, K. D.; Schotte, U.; Szuecs, Z.; Ruppert, U.

    1983-06-01

    Increased reliability of He2 cooling systems for space applications is considered. An active phase separator (APS) with annular flow gap of variable length which allows variation of the cooling capacity over a wide range, developed for zero-g tests is described. Helium-tight electrical leadthroughs, a displacement transducer for low temperature application, a ball closure for use in combination with the APS, and gas/liquid detectors were developed. For temperature and liquid level measurement in narrow slits in laboratory as well as flight experiments, temperature sensors were developed. Three thickness measurement methods for He2 films are proposed: optical (1/10 000 to 1/100 mm), crystal (1/10 to the 7th power to 1/10 mm) and capacitive (1/10 to the 6th power to some mm).

  8. 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

    2015-08-01

    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. PMID:26267199

  9. Temperature dependence of the accommodation coefficient of liquid-helium film.

    NASA Technical Reports Server (NTRS)

    Wang, T. G.; Elleman, D. D.; Olli, E. E.; Saffren, M. M.

    1973-01-01

    We have determined the accommodation coefficient, gamma, of a helium film from 1.15 to 4 K by measuring the time constant of a rotating superconducting Nb sphere levitated in vapor and covered with a saturated helium film. The conventional assumption of the phenomenological theory of superfluidity, that the order parameter psi vanishes at the free surface of helium II, implies that gamma, is unity and independent of temperature. We find that gamma, is nearly unity above the lambda point, suffers an abrupt drop close to T-lambda, and gradually levels off to the value of about 0.8 at lower temperatures.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Dynamic structure factor of liquid 4He across the normal-superfluid transition

    NASA Astrophysics Data System (ADS)

    Ferré, G.; Boronat, J.

    2016-03-01

    We have carried out a microscopic study of the dynamic structure factor of liquid 4He across the normal-superfluid transition temperature using the path integral Monte Carlo method. The ill-posed problem of the inverse Laplace transform, from the imaginary-time intermediate scattering function to the dynamic response, is tackled by stochastic optimization. Our results show a quasiparticle peak and a small and broad multiphonon contribution. In spite of the lack of strength in the collective peaks, we clearly identify the rapid dropping of the roton peak amplitude when crossing the transition temperature Tλ. Other properties such as the static structure factor, static response, and one-phonon contribution to the response are also calculated at different temperatures. The changes of the phonon-roton spectrum with the temperature are also studied. An overall agreement with available experimental data is achieved.

  16. 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.

  17. 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

  18. Dissipation in Nanoscale Superfluids

    NASA Astrophysics Data System (ADS)

    Del Maestro, Adrian; Rosenow, Bernd

    Pressure driven flow of a superfluid inside a narrow channel can be maintained by the nucleation of vortices and their resulting motion across the flow lines. The maximum velocity of the superfluid is set by a nucleation rate which crucially depends on the microscopic details of the vortices and flow profile. Within the kinetic vortex theory, we have determined the critical superfluid velocity inside a nanoscale constriction and obtain agreement with experimental results for superfluid helium-4 in nanopores. In the small pore limit, when the ratio of pore radius to correlation length is of order unity, we find a drastic suppression of the superfluid velocity that can be understood within the Langer-Ambegaokar-McCumber-Halperin theory of resistive fluctuations in thin superconducting wires.

  19. 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

  20. Heat transfer in a liquid helium cooled vacuum tube following sudden vacuum loss

    NASA Astrophysics Data System (ADS)

    Dhuley, R. C.; Van Sciver, S. W.

    2015-12-01

    Condensation of nitrogen gas rapidly flowing into a liquid helium (LHe) cooled vacuum tube is studied. This study aims to examine the heat transfer in geometries such as the superconducting RF cavity string of a particle accelerator following a sudden loss of vacuum to atmosphere. In a simplified experiment, the flow is generated by quickly venting a large reservoir of nitrogen gas to a straight long vacuum tube immersed in LHe. Normal LHe (LHe I) and superfluid He II are used in separate experiments. The rate of condensation heat transfer is determined from the temperature of the tube measured at several locations along the gas flow. Instantaneous heat deposition rates in excess of 200 kW/m2 result from condensation of the flowing gas. The gas flow is then arrested in its path to pressurize the tube to atmosphere and estimate the heat transfer rate to LHe. A steady LHe I heat load of ≈25 kW/m2 is obtained in this scenario. Observations from the He II experiment are briefly discussed. An upper bound for the LHe I heat load is derived based on the thermodynamics of phase change of nitrogen.

  1. 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.

  2. 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). PMID:24522597

  3. Ultracold-neutron production and up-scattering in superfluid helium between 1.1 K and 2.4 K

    NASA Astrophysics Data System (ADS)

    Leung, K. K. H.; Ivanov, S.; Piegsa, F. M.; Simson, M.; Zimmer, O.

    2016-02-01

    Ultracold neutrons (UCNs) were produced in superfluid helium using the PF1B cold-neutron beam facility at the Institut Laue-Langevin. A 4-liter beryllium-coated converter volume with a mechanical valve and windowless stainless-steel extraction system were used to accumulate and guide UCNs to a detector at room temperature. At a converter temperature of 1.08 K the total storage time constant in the vessel was (20.3 ±1.2 )s and the number of UCNs counted after accumulated was 91 700 ±300 . From this, we derive a volumetric UCN production rate of (6.9 ±1.7 ) cm-3s-1 , which includes a correction for losses in the converter during UCN extraction caused by the short storage time, but not accounting for UCN transport and detection efficiencies. The up-scattering rate of UCNs caused by excitations in the superfluid was studied by scanning the temperature between 1.2 K and 2.4 K . Using the temperature-dependent UCN production rate calculated from inelastic neutron scattering data, the only UCN up-scattering process found to occur was from two-phonon scattering. Our analysis for T <1.95 K rules out the contributions from roton-phonon scattering to <29 % (95% C.I.) and from one-phonon absorption to <47 % (95% C.I.) of their predicted levels.

  4. 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.

  5. Annihilation of an AB/BA interface pair in superfluid helium-3 as a simulation of cosmological brane interaction.

    PubMed

    Bradley, D Ian; Fisher, Shaun N; Guénault, Anthony M; Haley, Richard P; Kopu, Juha; Martin, Hazel; Pickett, George R; Roberts, John E; Tsepelin, Viktor

    2008-08-28

    This study presents measurements of the transport of quasiparticle excitations in the B phase of superfluid 3He at temperatures below 0.2Tc. We find that creating and then removing a layer of A-phase superfluid leads to a measurable increase in the thermal impedance of the background B phase. This increase must be due to the survival of defects created as the AB and BA interfaces on either side of the A-phase layer annihilate. We speculate that a new type of defect may have been formed. The highly ordered A-B interface may be a good analogy for branes discussed in current cosmology. If so, these experiments may provide insight into how the annihilation of branes can lead to the formation of topological defects such as cosmic strings. PMID:18534941

  6. Dramatic effect of superfluidity on the collapse of 4He vapor bubbles

    NASA Astrophysics Data System (ADS)

    Qu, An; Trimeche, A.; Jacquier, Ph.; Grucker, J.

    2016-05-01

    The lifetime of cavitation bubbles produced by an acoustic wave focused in liquid helium-4 is investigated. This lifetime is found to be different by orders of magnitude depending on whether the liquid is superfluid or not. We show that if the liquid is in the superfluid state, the bubble lifetime is well explained by a purely mechanical model, corresponding to the so-called Rayleigh regime. In the normal state, the Rayleigh-Plesset regime applies, in which heat diffusion plays a crucial role and dramatically increases the bubble lifetime.

  7. 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.

  8. Superfluidity, Bose condensation and neutron scattering in liquid {sup 4}He

    SciTech Connect

    Silver, R.N.

    1997-04-01

    The relation between superfluidity and Bose condensation in {sup 4}He provides lessons that may be valuable in understanding the strongly correlated electron system of high {Tc} superconductivity. Direct observation of a Bose condensate in the superfluid by deep inelastic neutron scattering measurements has been attempted over many years. But the impulse approximation, which relates momentum distributions to neutron scattering structure functions, is broadened by final state effects. Nevertheless, the excellent quantitative agreement between ab initio quantum many body theory and high precision neutron experiments provides confidence in the connection between superfluidity and Bose condensation.

  9. Measured ground performance and predicted orbital performance of the superfluid helium dewar for the Cosmic Background Explorer

    NASA Technical Reports Server (NTRS)

    Hopkins, Richard A.; Ryschkewitsch, M. G.

    1986-01-01

    A critical component of the Cosmic Background Explorer observatory, which is to be lifted to orbit in 1988, is the 650-l superfluid He dewar housing a far-IR absolute spectrophotometer and a diffuse IR background experiment. Attention is presently given to the results of a four-month-long test program encompassing dewar filling verification, vibration characteristics, thermal performance over orbital lifetime, and aperture cover ejection behavior. No significant flaws have been noted; the orbital cryogen lifetime is projected to be 14 months.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography.

    PubMed

    Iancu, Cristina V; Wright, Elizabeth R; Heymann, J Bernard; Jensen, Grant J

    2006-03-01

    The principal resolution limitation in electron cryomicroscopy of frozen-hydrated biological samples is radiation damage. It has long been hoped that cooling such samples to just a few kelvins with liquid helium would slow this damage and allow statistically better-defined images to be recorded. A new "G2 Polara" microscope from FEI Company was used to image various biological samples cooled by either liquid nitrogen or liquid helium to approximately 82 or approximately 12 K, respectively, and the results were compared with particular interest in the doses (10-200 e-/A2) and resolutions (3-8 nm) typical for electron cryotomography. Simple dose series revealed a gradual loss of contrast at approximately 12K through the first several tens of e-/A2, after which small bubbles appeared. Single particle reconstructions from each image in a dose series showed no difference in the preservation of medium-resolution (3-5 nm) structural detail at the two temperatures. Tomographic reconstructions produced with total doses between 10 and 350 e-/A2 showed better results at approximately 82 K than approximately 12 K for every dose tested. Thus disappointingly, cooling with liquid helium is actually disadvantageous for cryotomography. PMID:16427786

  16. 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.

  17. Second sound and the superfluid fraction in a Fermi gas with resonant interactions.

    PubMed

    Sidorenkov, Leonid A; Tey, Meng Khoon; Grimm, Rudolf; Hou, Yan-Hua; Pitaevskii, Lev; Stringari, Sandro

    2013-06-01

    Superfluidity is a macroscopic quantum phenomenon occurring in systems as diverse as liquid helium and neutron stars. It occurs below a critical temperature and leads to peculiar behaviour such as frictionless flow, the formation of quantized vortices and quenching of the moment of inertia. Ultracold atomic gases offer control of interactions and external confinement, providing unique opportunities to explore superfluid phenomena. Many such (finite-temperature) phenomena can be explained in terms of a two-fluid mixture comprising a normal component, which behaves like an ordinary fluid, and a superfluid component with zero viscosity and zero entropy. The two-component nature of a superfluid is manifest in 'second sound', an entropy wave in which the superfluid and the non-superfluid components oscillate with opposite phases (as opposed to ordinary 'first sound', where they oscillate in phase). Here we report the observation of second sound in an ultracold Fermi gas with resonant interactions. The speed of second sound depends explicitly on the value of the superfluid fraction, a quantity that is sensitive to the spectrum of elementary excitations. Our measurements allow us to extract the temperature dependence of the superfluid fraction, a previously inaccessible quantity that will provide a benchmark for theories of strongly interacting quantum gases. PMID:23676679

  18. 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).

  19. 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.

  20. 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.

  1. Novel cryogenic sources for liquid droplet and solid filament beams

    NASA Astrophysics Data System (ADS)

    Grams, Michael P.

    Two novel atomic and molecular beam sources have been created and tested consisting first of a superfluid helium liquid jet, and secondly a solid filament of argon. The superfluid helium apparatus is the second of its kind in the world and uses a modified liquid helium cryostat to inject a cylindrical stream of superfluid helium into vacuum through glass capillary nozzles with diameters on the order of one micron created on-site at Arizona State University. The superfluid beam is an entirely new way to study superfluid behavior, and has many new applications such as superfluid beam-surface scattering, beam-beam scattering, and boundary-free study of superfluidity. The solid beam of argon is another novel beam source created by flowing argon gas through a capillary 50 microns in diameter which is clamped by a small copper plate to a copper block kept at liquid nitrogen temperature. The gas subsequently cools and solidifies plugging the capillary. Upon heating, the solid plug melts and liquid argon exits the capillary and immediately freezes by evaporative cooling. The solid filaments may find application as wall-less cryogenic matrices, or targets for laser plasma sources of extreme UV and soft x-ray sources.

  2. 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.

  3. 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

  4. 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.

  5. Heat transfer characteristics of a plate-fin type supercritical/liquid helium heat exchanger

    NASA Astrophysics Data System (ADS)

    Kato, T.; Miyake, A.; Hiyama, T.; Kawano, K.; Iwamoto, S.; Ebisu, H.; Takahashi, T.; Hamada, K.; Tsuji, H.; Tsukamoto, N.; Yamaguchi, M.; Ishida, H.; Honda, T.; Yamanishi, A.; Ohmori, T.; Mori, M.

    A compact supercritical-helium/liquid-helium heat exchanger composed of a plate-fin type was studied. The heat exchange limit performance was determined through the experiment. The pulse heating performance was observed to apply the pulse heating by an electric heater. A numerical heat exchanger simulating calculation was carried out, which successfully expresses the experiment results.

  6. 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.

  7. 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.

  8. Sub-micron solid air tracers for quantum vortices and liquid helium flows

    NASA Astrophysics Data System (ADS)

    Fonda, Enrico; Sreenivasan, Katepalli R.; Lathrop, Daniel P.

    2016-02-01

    The dynamics of quantized vortices in superfluids has received increased attention recently because of novel techniques developed to visualize them directly. One of these techniques [G. P. Bewley et al., Nature 441, 588 (2006)] visualized quantized vortices and their reconnections in superfluid flows of 4He by using solid hydrogen tracers of micron-size or larger. The present work improves upon the previous technique by using substantially smaller particles created by injecting atmospheric air diluted in helium gas. These smaller particles are detectable thanks to the higher index of refraction of nitrogen compared to hydrogen and thanks to an improved visualization setup. The optical counting estimate, which agrees with terminal velocity estimates, suggests that the tracer diameter is typically 400 ± 200 nm and could be as small as 200 nm; being smaller, but not so small as to be influenced by thermal motion, the particles get trapped on the vortices faster, perturb the vortices less, possess smaller Stokes drag, and stay trapped on fast-moving vortices, as also on vortices generated closer to the superfluid transition temperature. Unlike the past, the ability to create particles in the superfluid state directly (instead of creating them above the λ-point and cooling the fluid subsequently), ensures greater temperature stability for longer periods, and enables the tracking of long and isolated vortices. These advantages have also led to the direct visualization of Kelvin waves. The use of other seed gases could lead to the visualization of even smaller tracers for quantized vortices. We discuss the visualization setup and provide suggestions for further improvement.

  9. Sub-micron solid air tracers for quantum vortices and liquid helium flows.

    PubMed

    Fonda, Enrico; Sreenivasan, Katepalli R; Lathrop, Daniel P

    2016-02-01

    The dynamics of quantized vortices in superfluids has received increased attention recently because of novel techniques developed to visualize them directly. One of these techniques [G. P. Bewley et al., Nature 441, 588 (2006)] visualized quantized vortices and their reconnections in superfluid flows of (4)He by using solid hydrogen tracers of micron-size or larger. The present work improves upon the previous technique by using substantially smaller particles created by injecting atmospheric air diluted in helium gas. These smaller particles are detectable thanks to the higher index of refraction of nitrogen compared to hydrogen and thanks to an improved visualization setup. The optical counting estimate, which agrees with terminal velocity estimates, suggests that the tracer diameter is typically 400 ± 200 nm and could be as small as 200 nm; being smaller, but not so small as to be influenced by thermal motion, the particles get trapped on the vortices faster, perturb the vortices less, possess smaller Stokes drag, and stay trapped on fast-moving vortices, as also on vortices generated closer to the superfluid transition temperature. Unlike the past, the ability to create particles in the superfluid state directly (instead of creating them above the λ-point and cooling the fluid subsequently), ensures greater temperature stability for longer periods, and enables the tracking of long and isolated vortices. These advantages have also led to the direct visualization of Kelvin waves. The use of other seed gases could lead to the visualization of even smaller tracers for quantized vortices. We discuss the visualization setup and provide suggestions for further improvement. PMID:26931890

  10. Heat and mass transfer of submerged helium injection in liquid oxygen vessel

    NASA Astrophysics Data System (ADS)

    Jung, Youngsuk; Cho, Namkyung; Baek, Seungwhan; Jeong, Sangkwon

    2014-11-01

    The submerged helium injection process results in the heat and mass transfer between the helium bubble and the cryogenic liquid. The objective of this paper is to analyze the dynamics of the heat and mass transfer process. It is observed that during the helium injection process the dynamics of mass transfer is dominant and the transient heat transfer is negligible. The helium bubble shape and rising patterns are observed with a visualization device that helps to discern the dominant process between heat transfer and mass transfer. The clustering patterns such as coalescence of helium bubbles are observed with the visualization device. The visualization results indicate that, it is very difficult to determine the representative size of bubbles due to the irregular shape of the helium bubbles. The shape and size of the helium bubbles are important parameters for evaluating the overall mass transfer coefficient (kGA) which is the essential parameter for calculating the evaporation rate of the bulk liquid into the helium bubbles. In this paper, the simplified lumped model is considered to fairly approximate the evaporation rate of the cryogenic liquid into the bubbles and the cooling rate of helium injection. The empirical correlation for the average concentration (C‾A) of evaporated cryogenic liquid into the helium bubbles is presented and the overall mass transfer coefficients (kGA) are calculated as the result of the lumped model. The proposed model and empirical correlations are compared with the experimental results, and the comparison result shows good agreement with differences that are less than ±0.4 K.

  11. 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.

  12. Laser spectroscopy of atoms in superfluid helium for the measurement of nuclear spins and electromagnetic moments of radioactive atoms

    NASA Astrophysics Data System (ADS)

    Fujita, T.; Furukawa, T.; Imamura, K.; Yang, X. F.; Hatakeyama, A.; Kobayashi, T.; Ueno, H.; Asahi, K.; Shimoda, T.; Matsuo, Y.

    2015-11-01

    A new laser spectroscopic method named "OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)" has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with 84-87Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes.

  13. Probing quantum and classical turbulence analogy in von Kármán liquid helium, nitrogen, and water experiments

    SciTech Connect

    Saint-Michel, B.; Herbert, E.; Salort, J.; Castaing, B.; Chevillard, L.; Daviaud, F.; Dubrulle, B.; Lehner, Th.

    2014-12-15

    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.

  14. Thermal Conductivity of Liquid He-4 near the Superfluid Transition in Restricted Geometries

    NASA Technical Reports Server (NTRS)

    Liu, Yuanming

    2003-01-01

    We present measurements of the thermal conductivity near the superfluid transition of He-4 in confined geometries. The confinements we have studied include: cylindrical geometries with radii L=.5 and 1.0 microns, and parallel plates with 5 micron spacing. For L=1.0 microns, measurements at six pressures were conducted, whereas only SVP measurements have been done for other geometries. For the 1-D confinement in cylinders, the data are consistent with a universal scaling for all pressures at and above T(sub lambda). There are indications of breakdown of scaling and universality below T(sub lambda). For the 2-D confinement between parallel plates, the preliminary results indicate that the thermal conductivity is finite at the bulk superfluid transition temperature. Further analyses are needed to compare the 2-D results with those in bulk and 1-D confinement.

  15. 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).

  16. An Investigation in the Dynamics of Polarized Helium-3 in Superfluid Helium-4 for the Spallation Neutron Source (SNS) neutron-electric-dipole-moment (nEDM) experiment

    NASA Astrophysics Data System (ADS)

    Swank, Christopher Mark

    To conserve CPT, charge conjugation-parity-time reversal symmetry, the last discrete symmetry believed to be conserved, there must exist T violation. A measurement of the neutron-electric-dipole-moment (nEDM) would be a direct observation of T violation. The measurement of a nEDM requires the detection of a small shift in the Larmor precession frequency due to an applied electric field. The most recent experiment trying to measure the nEDM has been restricted by a systematic effect termed the geometric phase, a frequency shift linear in the electric field of the experiment. A new nEDM experiment is being planned for the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. It will use spin-polarized 3He as a comagnetometer and detector, and is susceptible to the geometric phase. To investigate, quantify and find ways to reduce this systematic effect is the main goal of this work. The dynamics of polarized 3He in phonon dominated superfluid 4He is investigated. A theory that predicts relaxations and frequency shifts, and hence the geometric phase frequency shift, via correlation functions valid from the ballistic through to the diffuse regime for restricted geometries is presented. For the first time, the lower dimensional correlation functions are shown to be projections of the higher dimensional correlation functions with the proper velocity weighting. The correlation function was measured by gradient induced longitudinal relaxation. The presented theory is shown to adequately predict the data. A previous theory, termed the high frequency theory due to its accurate description of relaxation with spins precessing at approximately the same rate as gas collisions, is also valid in this region. The presented theory is shown to agree with the high frequency theory. The two theories diverge with slightly more ballistic motion than the experiment was able to produce. Diffusion theory is shown to be inadequate to describe the data for the longer scattering

  17. 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.

  18. Thermal conductivity and Kapitza resistance of cyanate ester epoxy mix and tri-functional epoxy electrical insulations at superfluid helium temperature

    NASA Astrophysics Data System (ADS)

    Pietrowicz, S.; Four, A.; Jones, S.; Canfer, S.; Baudouy, B.

    2012-02-01

    In the framework of the European Union FP7 project EuCARD, two composite insulation systems made of cyanate ester epoxy mix and tri-functional epoxy (TGPAP-DETDA) with S-glass fiber have been thermally tested as possible candidates to be the electrical insulation of 13 T Nb3Sn high field magnets under development for this program. Since it is expected to be operated in pressurized superfluid helium at 1.9 K and 1 atm, the thermal conductivity and the Kapitza resistance are the most important input parameters for the thermal design of this type of magnet and have been determined in this study. For determining these thermal properties, three sheets of each material with different thicknesses varying from 245 to 598 μm have been tested in steady-state condition in the temperature range of 1.6-2.0 K. The thermal conductivity for the tri-functional epoxy (TGPAP-DETDA) epoxy resin insulation is found to be k = [(34.2 ± 5.5)ṡT - (16.4 ± 8.2)] × 10-3 Wm-1 K-1 and for the cyanate ester epoxy k = [(26.8 ± 4.8)ṡT - (9.6 ± 5.2)] × 10-3 Wm-1 K-1. For the Kapitza resistance, Rk, the best curve fitting the experimental data is described by Rk = (3057 ± 593) × 10-6ṡT (-1.79 ± 0.34) m2 KW-1 for the TGPAP-DETDA insulation and Rk = (4114 ± 971) × 10-6ṡT (-1.73 ± 0.41) m2 KW-1 for the cyanate ester epoxy insulation. Our results are compared with other epoxy based composite electrical insulation found in the literature.

  19. 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.

  20. Is cold better ? - exploring the feasibility of liquid-helium-cooled optics.

    SciTech Connect

    Assoufid, L.; Mills, D.; Macrander, A.; Tajiri, G.

    1999-09-30

    Both simulations and recent experiments conducted at the Advanced Photon Source showed that the performance of liquid-nitrogen-cooled single-silicon crystal monochromators can degrade in a very rapid nonlinear fashion as the power and for power density is increased. As a further step towards improving the performance of silicon optics, we propose cooling with liquid helium, which dramatically improves the thermal properties of silicon beyond that of liquid nitrogen and brings the performance of single silicon-crystal-based synchrotrons radiation optics up to the ultimate limit. The benefits of liquid helium cooling as well as some of the associated technical challenges will be discussed, and results of thermal and structural finite elements simulations comparing the performance of silicon monochromators cooled with liquid nitrogen and helium will be given.

  1. 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.

  2. 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.

  3. On cavitation in liquid helium in a flow due to a vibrating quartz fork

    NASA Astrophysics Data System (ADS)

    Blažková, M.; Schmoranzer, D.; Skrbek, L.

    2008-04-01

    Cavitation in normal and superfluid liquid He4 at saturated vapor pressure and slightly elevated pressures has been experimentally studied in a flow due to quartz forks vibrating at high amplitudes. Above the temperature- and pressure-dependent critical velocity, heterogeneous cavitation is observed both visually and electrically, as a breakdown of the resonance response of the fork. We compare our results with available experimental and discuss them using existing theoretical models. In particular, we show that thermal effects leading to local overheating of the vicinity of the fork have to be taken into account, especially in normal liquid He4.

  4. Microwave experiments in He II. New features of undamped superfluid flows

    NASA Astrophysics Data System (ADS)

    Rybalko, A. S.; Rubets, S. P.; Rudavskiĭ, É. Ya.; Tikhiĭ, V. A.; Tarapov, S. I.; Golovashchenko, R. V.; Derkach, V. N.

    2008-07-01

    The stability and oscillatory properties of superfluid ring flow arising around the cylindrical surface of a disk-shaped dielectric resonator immersed in liquid helium are studied experimentally. The velocity of superfluid flow is controlled with special heat guns, placed in He II and generating counterflows of the normal and superfluid components, directed along the tangent to the cylindrical surface of the resonator. In the experiment the amplitude of the microwave signal passing through the resonator is measured and the effect of the phase and dynamic states of the liquid on the signal amplitude is studied. It is found that periodic oscillations of the signal are observed in the He II state, and each period starts with a sharp spike of the amplitude. It is proposed that this behavior signifies instability of superfluid ring flow due to a change in the number of circulation quanta of the superfluid velocity over a very short time. Another effect is due to the appearance of new periodically repeating resonance peaks, together with the ordinary whispering gallery modes, in the system. The effect is absent above λ point and is attributed to characteristic oscillatory modes of the undamped superfluid flow. Possible reasons for the observed features are analyzed.

  5. 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.

  6. Helium Refrigerator Liquid Nitrogen Pre-Cooler Component Parameter Sensitivity Analysis

    SciTech Connect

    Peter Knudsen, Venkatarao Ganni

    2010-04-01

    For helium refrigerators using liquid nitrogen (LN) pre-cooling it is not uncommon for the ambient helium refrigeration return stream(s) exiting the cold box to be significantly colder and for the cycle to use more nitrogen than estimated by the process studies. Often there is an emphasis on the length of 300 to 80-K helium-nitrogen heat exchangers to ensure the exiting nitrogen is as close to ambient as possible. However, it is really the size and flow distribution of the 300 to 80-K helium-helium heat exchangers which are the dominate influence of the nitrogen consumption. As such, an analysis was done to identify and quantify the sensitivity the key parameters in the refrigerator LN pre-cooler section affecting the LN consumption.

  7. 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

  8. Liquid helium-cooled MOSFET preamplifier for use with astronomical bolometer

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.

    1977-01-01

    A liquid helium-cooled p-channel enhancement mode MOSFET, the 3N167, is found to have sufficiently low noise for use as a preamplifier with helium-cooled bolometers that are used in infrared astronomy. Its characteristics at 300, 77, and 4.2 K are presented. It is also shown to have useful application with certain photoconductive and photovoltaic infrared detectors.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  10. Notch Effect on Tensile Deformation Behavior of 304L and 316L Steels in Liquid Helium and Hydrogen

    NASA Astrophysics Data System (ADS)

    Shibata, K.; Fujii, H.

    2004-06-01

    Tensile tests of type 304L and 316L steels were carried out using round bar specimens with a notch in liquid helium, hydrogen, liquid nitrogen and at ambient temperature. The obtained tensile strengths were compared with the tensile strengths of smooth specimens. For smooth specimens, tensile strength increased with a decrease in temperature and the strengths in liquid helium and hydrogen show similar values in both steels. For notched specimen of 304L steel, tensile strength (including fracture strength) increased noticeably from ambient to liquid nitrogen temperature but showed a large decrease in liquid helium and hydrogen. In liquid hydrogen and helium, the tensile strength is a little lower in liquid hydrogen than in liquid helium and both strengths are lower than tensile strengths of smooth specimens. For notched specimen of 316L steel, an increase in tensile strength from ambient to liquid nitrogen temperature was not so large and a decrease from liquid nitrogen to liquid hydrogen was small. The tensile strengths in liquid helium and hydrogen were nearly same and higher than those of smooth specimens. Different behavior of serration was observed between liquid helium and hydrogen, and between 304L and 316L steels. The reasons for these differences were discussed using computer simulation.

  11. Notch Effect on Tensile Deformation Behavior of 304L and 316L Steels in Liquid Helium and Hydrogen

    SciTech Connect

    Shibata, K.; Fujii, H.

    2004-06-28

    Tensile tests of type 304L and 316L steels were carried out using round bar specimens with a notch in liquid helium, hydrogen, liquid nitrogen and at ambient temperature. The obtained tensile strengths were compared with the tensile strengths of smooth specimens. For smooth specimens, tensile strength increased with a decrease in temperature and the strengths in liquid helium and hydrogen show similar values in both steels. For notched specimen of 304L steel, tensile strength (including fracture strength) increased noticeably from ambient to liquid nitrogen temperature but showed a large decrease in liquid helium and hydrogen. In liquid hydrogen and helium, the tensile strength is a little lower in liquid hydrogen than in liquid helium and both strengths are lower than tensile strengths of smooth specimens. For notched specimen of 316L steel, an increase in tensile strength from ambient to liquid nitrogen temperature was not so large and a decrease from liquid nitrogen to liquid hydrogen was small. The tensile strengths in liquid helium and hydrogen were nearly same and higher than those of smooth specimens. Different behavior of serration was observed between liquid helium and hydrogen, and between 304L and 316L steels. The reasons for these differences were discussed using computer simulation.

  12. 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.

  13. 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.

  14. 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.

  15. Creating Only Isotropic Homogeneous Turbulence in Liquid Helium near Absolute Zero

    NASA Astrophysics Data System (ADS)

    Ihas, G. G.; Thompson, K. J.; Labbe, G.; McClintock, P. V. E.

    2012-02-01

    Flow through a grid is a standard method to produce isotropic, homogeneous turbulence for laboratory study. This technique has been used to generate quantum turbulence (QT) above 1 K in superfluid heliumootnotetextS. R. Stalp, L. Skrbek, and R. J. Donnelly, Phys. Rev. Lett. 82, 4831 (1999). where QT seems to mimic classical turbulence. Efforts have been made recentlyootnotetextG. G. Ihas, G. Labbe, S-c. Liu, and K. J. Thompson, J. Low Temp. Phys. 150, 384 (2008). to make similar measurements near absolute zero, where there is an almost total absence of normal fluid and hence classical viscosity. This presents the difficulty that most motive force devices produce heat which overwhelms the phenomena being investigated. The process of designing and implimenting a ``dissipation-free'' motor for pulling a grid through superfluid helium at millikelvin temperatures has resulted in the development of new techniques which have broad application in low temperature research. Some of these, such as Meissner-affect magnetic drives, capacitive and inductive position sensors, and magnetic centering devices will be described. Heating results for devices which can move in a controlled fashion from very low speed up to 10 cm/s will be presented. Acknowledgement: We thank W.F. Vinen for many useful discussions.

  16. Programmable System-on-Chip (PSoC) Embedded Readout Designs for Liquid Helium Level Sensors.

    PubMed

    Parasakthi, C; Gireesan, K; Usha Rani, R; Sheela, O K; Janawadkar, M P

    2014-01-24

    This article reports the development of programmable system-on-chip (PSoC)-based embedded readout designs for liquid helium level sensors using resistive liquid vapor discriminators. The system has been built for the measurement of liquid helium level in a concave-bottomed, helmet-shaped, fiber-reinforced plastic cryostat for magnetoencephalography. This design incorporates three carbon resistors as cost-effective sensors, which are mounted at desired heights inside the cryostat and were used to infer the liquid helium level by measuring their temperature-dependent resistance. Localized electrical heating of the carbon resistors was used to discriminate whether the resistor is immersed in liquid helium or its vapor by exploiting the difference in the heat transfer rates in the two environments. This report describes a single PSoC chip for the design and development of a constant current source to drive the three carbon resistors, a multiplexer to route the sensor outputs to the analog-to-digital converter (ADC), a buffer to avoid loading of the sensors, an ADC for digitizing the data, and a display using liquid crystal display cum light-emitting diode modules. The level sensor readout designed with a single PSoC chip enables cost-effective and reliable measurement system design. PMID:24464811

  17. Depression of the Superfluid Transition Temperature in 4He by a Heat Flow

    NASA Astrophysics Data System (ADS)

    Yin, Liang; Lin, Peng; Qi, Xin

    2014-11-01

    The depression of the superfluid transition temperature Tλ in 4He by a heat flow Q is studied. A small sealed cell with a capillary is introduced and a stable and flat superfluid transition temperature plateau is easily obtained by controlling the temperature of the variable-temperature platform and the bottom chamber of the sealed cell. Owing to the depression effect of the superfluid transition temperature by the heat flow, the heat flow through the capillary is changed by the temperature control to obtain multiple temperature plateaus of different heat flows. The thermometer self-heating effect, the residual heat leak of the 4.2 K environment, the temperature difference on the He II liquid column, the Kapiza thermal resistance between the liquid helium and the copper surface of the sealed cell, the temperature gradient of the sealed cell, the static pressure of the He II liquid column and other factors have influence on the depression effect and the influence is analyzed in detail. Twenty experiments of the depression of the superfluid transition temperature in 4He by heat flow are made with four sealed cells in one year. The formula of the superfluid transition temperature pressured by the heat flow is Tλ (Q) = -0.00000103Q + 2.1769108, and covers the range 229 <= Q <= 6462 μW/cm2.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Modeling the pressure increase in liquid helium cryostats after failure of the insulating vacuum

    NASA Astrophysics Data System (ADS)

    Heidt, C.; Grohmann, S.; Süßer, M.

    2014-01-01

    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.

  4. 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.

  5. 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.

  6. Cantilever anemometer based on a superconducting micro-resonator: Application to superfluid turbulence

    SciTech Connect

    Salort, J.; Monfardini, A.; Roche, P.-E.

    2012-12-15

    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 Almost-Equal-To 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.

  7. 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

  8. Crystallization and melting of a system of charges in a liquid helium cluster

    SciTech Connect

    Livshits, A. M. Lozovik, Yu. E.

    2007-10-15

    A system of like (positive or negative) charges forming 'snowballs' or 'bubbles' in a three-dimensional liquid helium cluster is investigated. The charges are confined inside the cluster by an 'image potential' produced by the polarization of liquid helium. The stability of a multiply charged helium cluster is considered. Computer simulations are used to investigate the crystallization and melting of the system of charges depending on the dimensionless parameter T* = k{sub B}T{epsilon}R/e{sup 2}, where k{sub B} is the Boltzmann constant, T is the temperature, {epsilon} is the dielectric constant of liquid helium, R is the cluster radius, and e is a unit charge. Various characteristics, including symmetry groups and moments, have been found for equilibrium configurations of charges in a cluster with N = 1-100 charges. At small N {approx} 10, Thomson's model of successive filling of 'belts' of charges can be used to describe the structure of equilibrium configurations of charges. At large N, the description of the structure formed by charges using the idea of a quasi-two-dimensional 'closed triangular lattice' with topological defects is more adequate. Formally, this description is valid starting from N = 4. The melting of a 'lattice' of charges is described. A number of our conclusions can be generalized to clusters of other noble gases.

  9. 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.

  10. Studying electrons on curved surfaces by trapping and manipulating multielectron bubbles in liquid helium.

    PubMed

    Vadakkumbatt, Vaisakh; Joseph, Emil; Pal, Anustuv; Ghosh, Ambarish

    2014-01-01

    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. PMID:25081283

  11. Jet Pump for Liquid Helium Circulation Through the Fast Cycling Magnets of Nuclotron

    NASA Astrophysics Data System (ADS)

    Agapov, Nikolay; Emelianov, Nikita; Mitrofanova, Julia; Nikiforov, Dmitry

    Nuclotron is the first fast cycling superconducting synchrotron intended for the acceleration of high-energy nuclei and heavy ions. Its cryogenic system includes two helium refrigerators with a total capacity of 4000 W at 4.5 K. The 251.5 m long accelerator ring consists of 144 superconducting dipole and quadruple magnets. The magnets connected in parallel are refrigerated by a two-phase flow of boiling helium. In order to increase liquid helium flow directed to the superconducting magnets, jet pumps are used. We explain theoretical and experimental results that allow one to determinate main technical specifications and optimal geometric dimensions of the jet pumps. The experience of using this device and corresponding flow diagrams are described.

  12. 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)

  13. 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.

  14. 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.

  15. 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.

  16. Low gravity thermal stratification of liquid helium on SHOOT

    NASA Astrophysics Data System (ADS)

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

    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.

  17. 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.

  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. 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.

  20. Electron bubbles in liquid helium: Density functional calculations of infrared absorption spectra

    SciTech Connect

    Grau, Victor; Barranco, Manuel; Mayol, Ricardo; Pi, Marti

    2006-02-01

    Within density functional theory, we have calculated the energy of the transitions from the ground state to the first two excited states in the electron bubbles in liquid helium at pressures from zero to about the solidification pressure. For {sup 4}He at low temperatures, our results are in very good agreement with infrared absorption experiments. Above a temperature of {approx}2 K, we overestimate the energy of the 1s-1p transition. We attribute this to the break down of the Franck-Condon principle due to the presence of helium vapor inside the bubble. Our results indicate that the 1s-2p transition energies are sensitive not only to the size of the electron bubble, but also to its surface thickness. We also present results for the infrared transitions in the case of liquid {sup 3}He, for which we lack experimental data.

  1. 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.

  2. 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.

  3. Self-consistent Debye-Waller factors of the electron solid on liquid helium

    NASA Astrophysics Data System (ADS)

    Namaizawa, H.

    1980-05-01

    Based on the self-consistent field formalism we propose a shear-mode self-consistency for the high-frequency Debye-Waller factors (HFDWF) of the electron solid bound on a free surface of liquid helium. Our results are qualitatively in agreement with the empirical DW factor determined by Fisher, Halperin, and Platzman with the experiment of Grimes and Adams. We also report the analysis of the HFDWF according to the Lindemann law.

  4. Carrier transport and localization in a one-dimensional electronic system over liquid helium

    NASA Astrophysics Data System (ADS)

    Gladchenko, S. P.; Nikolaenko, V. A.; Kovdrya, Yu. Z.; Sokolov, S. S.

    2001-01-01

    The carrier mobility in a nearly one-dimensional electronic system over liquid helium is measured. One-dimensional conducting channels are created by using the curvature of the surface of liquid helium covering a profiled dielectric substrate and applying a clamping electric field, which holds the electrons on the bottom of the liquid troughs. Measurements are made in a temperature interval of 0.5-1.6 K at linear densities in the range (0.5-2.5)×104 cm-1 at a generator voltage of 2-200 mV. It is shown that for a clean substrate the mobility of the electrons is governed by their interaction with helium atoms in the vapor and with ripplons; the results of the measurements are in satisfactory agreement with a theoretical calculation that assumes no localization. It is found that for substrates carrying a charge or having defects on the surface, the electron mobility decreases in comparison with the value for a clean substrate, and at temperatures T<1 K is either practically independent of temperature or decreases slightly as the temperature is lowered. It is observed that the frequency of the plasma waves propagating in the system of conducting channels decreases as the electron mobility decreases. The observed effects can be explained by localization in the one-dimensional electronic system in a random potential and the diffusive motion of the carriers in hops from one localized state to another.

  5. Dynamic polarization of liquid helium three confined in fine powders

    SciTech Connect

    Engel, L.W.

    1987-01-01

    Dynamic nuclear polarization (DNP) of liquid /sup 3/He confined in fine powders can be produced by pumping the electron spin resonance (ESR) or paramagnetic centers in the powders. This dissertation describes measurements of the DNP of /sup 3/He in five powders, including two sucrose chars and three samples of MgO containing paramagnetic impurities. The experiments were performed with temperatures between 1.3 and 1.8 K, and fields of around 180 Oe. The largest factor by which DNP was observe to enhance the /sup 3/He polarization from its value in thermal equilibrium was 1.7. In each powder, the time constant for DNP of the /sup 3/He was slightly longer than, or similar to, the /sup 3/He longitudinal relaxation time. Double nuclear resonance experiments involving /sup 1/H in one of the char samples, and the confined /sup 3/He were also performed, with an without simultaneous pumping of the ESR of the char. The dissertation includes a description of how observations of DNP of /sup 3/He by paramagnetic centers in powders might depend on the atomic motion and spin dynamics of the nuclei in the liquid near the powders surfaces. Mechanisms that might explain the observed DNP are discussed in detail, and qualitative predictions based on those mechanisms are compared with the experimental data.

  6. Influence of the liquid helium meniscus on neutron reflectometry data

    NASA Astrophysics Data System (ADS)

    Kinane, C. J.; Kirichek, O.; Charlton, T. R.; McClintock, P. V. E.

    2016-02-01

    Neutron reflectometry offers a unique opportunity for the direct observation of nanostratification in 3He-4He mixtures in the ultra-low temperature limit. Unfortunately the results of recent experiments could not be well-modelled on account of a seemingly anomalous variation of reflectivity with momentum transfer. We now hypothesize that this effect is attributable to an optical distortion caused by the liquid's meniscus near the container wall. The validity of this idea is tested and confirmed through a subsidiary experiment on a D2O sample, showing that the meniscus can significantly distort results if the beam size in the horizontal plane is comparable with, or bigger than, the diameter of the container. The meniscus problem can be eliminated if the beam size is substantially smaller than the diameter of the container, such that reflection takes place only from the flat region of the liquid surface thus excluding the meniscus tails. Practical measures for minimizing the meniscus distortion effect are discussed.

  7. Vortices in rotating superfluid 3He.

    PubMed

    Lounasmaa, O V; Thuneberg, E

    1999-07-01

    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

  8. 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

  9. Stick-Slip Motion of the Wigner Solid on Liquid Helium.

    PubMed

    Rees, David G; Beysengulov, Niyaz R; Lin, Juhn-Jong; Kono, Kimitoshi

    2016-05-20

    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. PMID:27258879

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. Experimental Study of a Bose Superfluid ``Battery'' for Atomtronics

    NASA Astrophysics Data System (ADS)

    Anderson, Dana; Caliga, Seth; Straatsma, Cameron

    2013-05-01

    The two component model of superfluids describes a thermo-mechanical force in which a thermal gradient across the fluid causes a counter-propagating flow of the normal and superfluid components, with the superfluid current propagating toward the ``hot'' portion of the container and the normal component towards the ``cold.'' We observe the energy and flux of a Bose-condensed gas flowing over a barrier in a hybrid magnetic and optical trap using a high-resolution atom chip projection and in-trap imaging system. We introduce a thermal gradient using asymmetric cooling of the condensed gas and the resulting thermo-mechanical force induces a supercurrent flow over the barrier. We observe, as expected, that the energy of the atoms emerging from the barrier is determined by the barrier height. We show that, like the ``fountain effect'' seen in liquid helium-4, the energy of the emerging atoms can be many times higher than the chemical potential as well as the thermal energy of the condensate. Through these experiments we establish that a reservoir of Bose-condensed atoms combined with a cooling mechanism can serve as a ``battery'' to drive the current in an atomtronic circuit.

  17. Electron-driven self-assembly of salt nanocrystals in liquid helium.

    PubMed

    Daxner, Matthias; Denifl, Stephan; Scheier, Paul; Ellis, Andrew M

    2014-12-01

    The self-assembly of salt nanocrystals from chemical reactions inside liquid helium is reported for the first time. Reaction is initiated by an electron impacting a helium nanodroplet containing sodium atoms and SF6 molecules, leading to preferential production of energetically favorable structures based on the unit cell of crystalline NaF. These favorable structures are observed as magic number ions (anomalously intense peaks) in mass spectra and are seen in both cationic and anionic channels in mass spectra, for example, (NaF)n Na(+) and (NaF)n F(-) . In the case of anions the self-assembly is not directly initiated by electrons: the dominant process involves resonant electron-induced production of metastable electronically excited He(-) anions, which then initiate anionic chemistry by electron transfer. PMID:25378098

  18. Possible Visualization of a Superfluid Vortex Loop Attached to an Oscillating Beam

    NASA Astrophysics Data System (ADS)

    Zemma, E.; Tsubota, M.; Luzuriaga, J.

    2015-06-01

    Visualization using tracer particles is a relatively new tool available for the study of superfluid turbulence and flow, which is applied here to oscillating objects submerged in the liquid. We report observations of a structure seen in videos taken from outside a cryostat filled with superfluid helium at 2 K, which is possibly a vortex loop attached to an oscillator. The feature, which has the shape of an incomplete arch, is visualized due to the presence of solid tracer particles and is attached to a beam oscillating at 38 Hz in the liquid. It has been recorded in videos taken at 240 frames per second, fast enough to take images per period. This makes it possible to follow the structure, and to see that it is not rigid. It moves with respect to the oscillator, and its displacement is in phase with the velocity of the moving beam. Analyzing the motion, we come to the conclusion that we may be observing a superfluid vortex attached to the beam and decorated by the hydrogen particles. An alternative model, considering a solid hydrogen filament, has also been analyzed, but the observed phase between the movement of the beam and the filamentary structure is better explained by the superfluid vortex hypothesis.

  19. Studies of Nonconventional Superfluids: Ultrasound Propagation in HELIUM-3-BORON and the Microwave Surface Impedance of the Heavy-Fermion Superconductor Uranium PLATINUM(3)

    NASA Astrophysics Data System (ADS)

    Zhao, Zuyu

    1990-06-01

    Two nonconventional superfluids, superfluid ^3He-B and the heavy fermion superconductor UPt_3 have been studied using different techniques: (1) A study of ^3He -B was performed in an acoustic sound cell with a path length of 381mum using the single-ended, c.w., acoustic impedance technique. The fundamental frequency of the x-cut quartz transducer employed in the experiments was 12.80 MHz. The following studies were performed: (a) A systematic measurement was made on the pair-breaking edge in zero magnetic field with ultrasonic frequencies of 64.3 MHz, 90.1 MHz, 141.6 MHz and 167.4 MHz, in the pressure range from 3 bar to 28 bar. The results of our measurements indirectly support the temperature scale of Greywall and the weak coupling plus (WCP) model of Rainer and Serene for the gap function. The pair-breaking edge was also measured in magnetic fields up to 1.36 kG perpendicular to the sound propagation direction and the predicted shift of the effective pair-breaking threshold (from 2 Delta(T) in zero field) by Omega = {gamma Hover 1+{1 over3}F_sp{o}{a}(2+Y) }(the renormalized Larmor frequency) has been observed. (b) The (imaginary) squashing mode was excited with sound frequencies of 141.6 MHz and 115.8 MHz. A doublet splitting (of about 0.3 MHz) of this mode was observed. This doublet splitting was found to be strongly pressure and frequency dependent, but independent of the magnetic field (at the low fields studied). Possible causes of this splitting include superfluid flow induced texture effects and finite wavevector (dispersion) effects. (c) Structure was observed with a sound frequency of 64.3 MHz in the vicinity of 2Delta(T) in a magnetic field of about 580 Gauss which is thought to be J_{z} = -1 component of the J = 1^- collective mode. (2) A surface impedance study of heavy Fermion superconductor UPt_3 was performed with an X-band microwave spectrometer (f ~eq 11.42 GHz) integrated with an Oxford 400 TLE dilution refrigerator so as to have top

  20. 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

    2014-11-01

    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. PMID:26278769

  1. Producing and imaging a thin line of He2 ∗ molecular tracers in helium-4

    NASA Astrophysics Data System (ADS)

    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 He2 ∗ 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.

  2. 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. PMID:26429454

  3. Small-angle Neutron Scattering Measurements of Liquid Helium Mixtures Confined in MCM-41

    NASA Astrophysics Data System (ADS)

    Kaiser, Helmut; Prisk, Timothy; Sokol, Paul; Steward, Ian; Pantalei, Claudia

    2011-03-01

    Small-angle neutron scattering (SANS) was used to study the isotopic distribution of liquid helium mixtures confined in MCM- 41, a silica glass with a 2D hexagonal net of monodisperse cylindrical pores, as a function of filling and He 3 concentration. The ordered pore array of MCM-41 gives rise to Bragg reflections with intensities determined by both how the liquid fills the pores and how the isotopes are distributed within the pores. The modulation in peak intensity can be modeled by writing down a form factors for cylindrical objects with varying scattering length density. Comparison will be made with small-angle X-ray (SAXS) scattering measurements performed with synchrotron light on liquid helium mixtures confined in aerogel. This work was supported by award 70NANB5H1163 from NIST, U.S. DOC. This Research at Oak Ridge National Laboratory's High Flux Isotope was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy.

  4. Localization of carriers in a one-dimensional electron system over liquid helium

    NASA Astrophysics Data System (ADS)

    Gladchenko, S. P.; Kovdrya, Yu. Z.; Nikolaenko, V. A.

    2000-07-01

    The mobility of carriers in a one-dimensional electron system over liquid helium has been measured at the temperature 0.5-1.7 K and for different values of linear electron density. Profiled nylon substrates with some quantity of charge deposited were used for the realization of a one-dimensional electron system. It is shown that electron mobility is dependent on the quantity of the charge on a substrate. Effects observed are explained by the localization of electrons moving in the random potential created by the substrates charge. It is supposed that at low temperatures the movement of carriers is determined by quantum effects.

  5. A liquid helium cooled mid-infrared imaging Fabry-Perot spectrometer

    NASA Astrophysics Data System (ADS)

    Watarai, H.; Chaen, K.; Matsuhara, H.; Matsumoto, T.; Takahashi, H.

    1994-03-01

    A liquid helium cooled mid-infrared imaging Fabry-Perot spectrometer has been under development. A Si:P 5x5 detector array is used for this instrument. Although the array system has small format, but combination with junction field effect transistor (JFET) array will provide noise equivalent line flux of 1.0 x 10-21 w/sq cm(1000 sec, 10 sigma). This sensitivity is comparable with the short wavelength spectrometer (SWS) of the Infrared Space Observatory (ISO).

  6. 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.

  7. 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.

  8. Ir Spectroscopy on Peptides and Proteins after Ion Mobility Selection and in Liquid Helium Droplets

    NASA Astrophysics Data System (ADS)

    von Helden, Gert

    2015-06-01

    IR spectroscopy has become a frequently used tool to characterize gas-phase peptides and proteins. In many experiments, ions are m/z selected, irradiated by intense and tunable IR light and fragmentation is monitored as a function of IR wavelength. The presence of different conformers can, however, complicate the interpretation, as the resulting spectra represent the sum of the spectra of the individual components. We constructed a setup, in which ion mobility methods are used to obtain m/z selected ions of defined shape on which are then further investigated by IR spectroscopy. First results on peptide aggregates are presented and for some of those, the IR spectra show a transition from helical or random coil to beta sheet structures. In a different experiment, peptide or protein ions are captures in liquid helium droplets prior to IR spectroscopic investigation. The conditions inside a helium droplet are isothermal at 0.38 K and the interaction between the helium matrix and the molecules are weak so that only small perturbations on the molecule are expected. IR spectra for m/z selected peptides with up to 10 aminoacids and proteins containing more than 100 aminoacids have been measured. The spectra of the smaller species show resolved bands of individual oscillators, which can be used for structure assignment. For the larger species, band envelopes are obtained and for the case of highly charged proteins, a transition form helical to extended structures is observed.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. Critical flow and dissipation in a quasi-one-dimensional superfluid.

    PubMed

    Duc, Pierre-François; Savard, Michel; Petrescu, Matei; Rosenow, Bernd; Del Maestro, Adrian; Gervais, Guillaume

    2015-05-01

    In one of the most celebrated examples of the theory of universal critical phenomena, the phase transition to the superfluid state of (4)He 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 v s 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 v s 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

  16. 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

  17. 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/.

  18. Observing the drop of resistance in the flow of a superfluid Fermi gas.

    PubMed

    Stadler, David; Krinner, Sebastian; Meineke, Jakob; Brantut, Jean-Philippe; Esslinger, Tilman

    2012-11-29

    The ability of particles to flow with very low resistance is characteristic of superfluid and superconducting states, leading to their discovery in the past century. Although measuring the particle flow in liquid helium or superconducting materials is essential to identify superfluidity or superconductivity, no analogous measurement has been performed for superfluids based on ultracold Fermi gases. Here we report direct measurements of the conduction properties of strongly interacting fermions, observing the well-known drop in resistance that is associated with the onset of superfluidity. By varying the depth of the trapping potential in a narrow channel connecting two atomic reservoirs, we observed variations of the atomic current over several orders of magnitude. We related the intrinsic conduction properties to the thermodynamic functions in a model-independent way, by making use of high-resolution in situ imaging in combination with current measurements. Our results show that, as in solid-state systems, current and resistance measurements in quantum gases provide a sensitive probe with which to explore many-body physics. Our method is closely analogous to the operation of a solid-state field-effect transistor and could be applied as a probe for optical lattices and disordered systems, paving the way for modelling complex superconducting devices. PMID:23192151

  19. Development of low temperature solid state detectors for ultra-cold neutrons within superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baker, C. A.; Balashov, S. N.; Green, K.; van der Grinten, M. G. D.; Iaydjiev, P. S.; Ivanov, S. N.; Pendlebury, J. M.; Shiers, D. B.; Tucker, M. A. H.; Yoshiki, H.; Geltenbort, P.

    2003-04-01

    As part of an R&D programme for the development of a next-generation experiment to measure the neutron electric dipole moment, in which ultra-cold neutrons (UCN) are produced and stored in superfluid 4He (superthermal source), we have developed cryogenic detectors of UCN that can operate in situ within the superfluid. Surface barrier detectors and PIN diode detectors have been tested and proven to work well at temperatures as low as 80 mK. When combined with a layer of 6LiF which converts neutrons to charged particles, these detectors form a reliable UCN detection system which has been tested in liquid helium down to 430 mK. The detectors have operated within superfluid helium for periods of up to 30 days with no signs of degradation. The development of this detection system has enabled us to measure the flux of UCN from a superthermal UCN source with no intervening transmission windows which can attenuate the flux. The addition of thin films of magnetically aligned iron also enables these detectors to be used in situ for neutron spin-polarisation analysis.

  20. 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.

  1. Spectroscopy of the copper dimer in normal fluid, superfluid, and solid {sup 4}He

    SciTech Connect

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

    2010-10-21

    Copper atoms and molecules are laser ablated into bulk liquid and solid helium, and the emission spectra of the laser excited D{yields}X, B{yields}X, and a{yields}X transitions of Cu{sub 2} are observed to exhibit clearly resolved vibrational bands. Surprisingly, for the D{yields}X and the B{yields}X transitions, no differences were observed for superfluid He at 1.5 K, for the normal liquid at 2.65 K, or for the 1.5 K solid at higher pressures of about 30 bars. An interpretation based on the bubble model indicates that the interaction with the He matrix is much weaker than in the case of the alkali atoms. Compared to other solid rare gas matrices, the line shifts and line widths in condensed helium are much smaller by nearly an order of magnitude.

  2. 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

  3. 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.

  4. Two phase liquid helium flow testing to simulate the operation of a cryocondensation pump in the D3-D tokamak

    NASA Astrophysics Data System (ADS)

    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 D3-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.

  5. Two phase liquid helium flow testing to simulate the operation of a cryocondensation pump in the DIII-D tokamak

    NASA Astrophysics Data System (ADS)

    Laughon, G. J.; Baxi, C. B.; Campbell, G. L.; Mahdavi, M. A.; Makariou, C. C.; Menon, M. M.; Smith, J. P.; Schaffer, M. J.; Schaubel, K. M.

    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 beat transfer and constant temperature characteristics of boiling liquid helium. The pump is designed for a pumping speed of 32,0001/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.

  6. Characterisation and optimisation of flexible transfer lines for liquid helium. Part I: Experimental results

    NASA Astrophysics Data System (ADS)

    Dittmar, N.; Haberstroh, Ch.; Hesse, U.; Krzyzowski, M.

    2016-04-01

    The transfer of liquid helium (LHe) into mobile dewars or transport vessels is a common and unavoidable process at LHe decant stations. During this transfer reasonable amounts of LHe evaporate due to heat leak and pressure drop. Thus generated helium gas needs to be collected and reliquefied which requires a huge amount of electrical energy. Therefore, the design of transfer lines used at LHe decant stations has been optimised to establish a LHe transfer with minor evaporation losses which increases the overall efficiency and capacity of LHe decant stations. This paper presents the experimental results achieved during the thermohydraulic optimisation of a flexible LHe transfer line. An extensive measurement campaign with a set of dedicated transfer lines equipped with pressure and temperature sensors led to unique experimental data of this specific transfer process. The experimental results cover the heat leak, the pressure drop, the transfer rate, the outlet quality, and the cool-down and warm-up behaviour of the examined transfer lines. Based on the obtained results the design of the considered flexible transfer line has been optimised, featuring reduced heat leak and pressure drop.

  7. Anomalous charge transport in a quasi-one-dimensional electron system over liquid helium

    NASA Astrophysics Data System (ADS)

    Gladchenko, S. P.; Kovdrya, Yu. Z.; Nikolaenko, V. A.

    2003-11-01

    The conductivity σ in a quasi-one-dimensional electron system over liquid helium is measured in the temperature interval 0.5-1.7 K over a wide range of electron densities n. It is shown that the quantity σ/ne (e is the charge of the electron) initially increases with decreasing temperature and then, after passing through a maximum, begins to decline for T≈1 K. In this temperature region the value of σ/ne, above a certain value of the drift potential Vd, decreases with increasing Vd. It is conjectured that the anomalous charge transport observed in this study is due either to spatial ordering of the electrons in the quasi-one-dimensional channels or to the formation of many-electron polarons in the nonuniform potential along the channels.

  8. Transient Electromagnetic and Heat Transfer Characteristics of the MgB2 Superconductor in Liquid Helium

    NASA Astrophysics Data System (ADS)

    Jaim, H. M. Iftekhar; Bärner, K.

    2013-07-01

    A transient current density analysis is carried out for the type II superconductor (SC) material MgB2 in liquid Helium. Variable magnetic fields are used as the unknown in solving the curl-curl relations of the electromagnetic fields applying the finite element method (FEM) for 2D axis symmetric cylindrical wires. Assuming an exponential current rise, the magnetic flux, current density and temperature distribution in the SC and He are calculated. This study gives the limiting current values to avoid the normal state, the temperature distribution profile with time as well as the changes in the magnitude of the current and time constant. Oscillations and non-uniform temperature distributions are observed in He and in the SC respectively if one varies the parameters which are related to the different heat transfer mechanisms. A slight instability in the current distribution is also observed which might transfer to a thermal instability, i.e. could signal He boiling.

  9. Inhomogeneous broadening of electronic transitions in a liquid helium bubble: The role of shape fluctuations

    NASA Astrophysics Data System (ADS)

    Lerner, P. B.; Chadwick, M. B.; Sokolov, I. M.

    1993-02-01

    Recent experiments of Grimes et al. [ Phys. Rev. B 41, 6366 (1990)] and Parshin et al. [ JETP, 74, 68 (1992)] demonstrate a substatial broadening in the 1 s-1 p transition of a single electron trapped in a liquid helium bubble (“bubblonium”) compared to theoretical predictions based on natural radiative linewidth. We show that the larger observed linewidth can be explained by inhomogeneus broadening due to quantum quadrupole fluctuations in the bubble shape. A simple adiabaticity rule for the bubblonium transitions similar to the Franck-Condon principle for molecular transitions is established. Quantitative estimates of the additional inhomogeneous linewidth at T=0 and 2.2 K are provided. The full theoretical linewidth, due to inhomogeneous and homogeneous broadening, has a Voigt-profile shape, and accounts for the data reasonably well.

  10. Logarithmic Singularity of Specific Heat in Liquid Helium II at the λ Point

    NASA Astrophysics Data System (ADS)

    Sasaki, Shosuke

    2007-08-01

    The experimental width of the second sound peak in Brillouin scattering is less than the instrumental width. It is also less than the width of the first sound peak near the λ point. The theoretical width of the second sound peak becomes infinitely large at the λ point in the traditional viewpoint. This discrepancy suggests that the second sound peak detected in Brillouin scattering is an elementary excitation. We calculate the specific heat of liquid helium near the λ point by considering the second sound peak. The calculated temperature-dependence of the specific heat has a logarithmic divergence at the λ point. Furthermore, the calculated values of the specific heat agree well with data derived from experiments.

  11. D0 Solenoid Upgrade Project: Rectangular Liquid Helium Tube, Miscellaneous Information

    SciTech Connect

    Rucinski, R.; /Fermilab

    1993-05-26

    This engineering note contains miscellaneous information about the rectangular liquid helium supply tube for the D-Zero solenoid. The information is fairly superficial, but could be used as a starting point for a future engineer who is going to specify and puchase the tubing. The chimney contains 4 conductors attached to an aluminum liquid helium supply tube. Because good thermal contact is desired, the tube will have flat sides. Aluminum is chosen to match the thermal contraction coefficient of the superconductor's aluminum stabilizer. The type of aluminum is chosen as 6061-T6 because it's allowable stress in ANSI/ASME B31.3 is higher than for other alloys. A different alloy could be chosen for extrusion reasons. The highest pressures this tubing should see will be during a quench. Current calculations predict the peak pressure during a quench to be 520 psi a for one-way relieving and 250 psia for two way relieving. Whatever the final alloy selection, the tubing needs to have a high enough allowable working pressure. There is very little room in the obround section of the chimney. In that portion the shape is rectangular, 12.7 mm (0.50-inch) x 31.8 mm (1.25-inch). A drawing shows the flow path cross section. This also could be changed for extrusion reasons if necessary. The important thing here is to estimate the pressure drop and make sure it is acceptable. Pressure drop estimates for this cross section are acceptable since it only about 10 feet in length.

  12. 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.

  13. Perturbation Theory for Superfluid in Nonuniform Potential

    NASA Astrophysics Data System (ADS)

    Koshida, Shinji; Kato, Yusuke

    2016-05-01

    Perturbation theory of superfluid fraction in terms of nonuniform potential is constructed. We find that the coefficient of the leading term is determined by the dynamical structure factor or density fluctuation of the system. The results for the ideal Bose gas and the interacting Bose system with linear dispersion are consistent to implications from Landau's criterion. We also find that the superfluidity of Tomonaga-Luttinger liquid with K>2 is shown to be stable against nonuniform potential.

  14. 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

  15. Effect of Specimen Diameter on Tensile Properties of Austenitic Stainless Steels in Liquid Hydrogen and Gaseous Helium at 20K

    NASA Astrophysics Data System (ADS)

    Fujii, H.; Ohmiya, S.; Shibata, K.; Ogata, T.

    2006-03-01

    Tensile tests using round bar type specimens of 3, 5 and 7 mm in diameter were conducted at 20K in liquid hydrogen and also in gaseous helium at the same temperature for three major austenitic stainless steels, JIS SUS304L, 316L and 316LN, extensively used for cryogenic applications including liquid hydrogen transportation and storage vessels. Stress-strain curves were considerably different between circumstances and also specimen diameter, resulting in differences of strength and ductility. In liquid hydrogen, serrated deformation appeared after considerable work hardening and more active in specimens with larger diameter. Meanwhile serrated deformation was observed from the early stage of plastic deformation in gaseous helium at 20 K and serration was more frequent in specimens with smaller diameter. The serrated deformation behaviors were numerically simulated for 304L steel with taking thermal properties such as thermal conductivity, specific heat, heat transfer from specimens to cryogenic media into account, and some agreement with the experiments was obtained.

  16. Effect of Specimen Diameter on Tensile Properties of Austenitic Stainless Steels in Liquid Hydrogen and Gaseous Helium at 20K

    SciTech Connect

    Fujii, H.; Ohmiya, S.; Shibata, K.; Ogata, T.

    2006-03-31

    Tensile tests using round bar type specimens of 3, 5 and 7 mm in diameter were conducted at 20K in liquid hydrogen and also in gaseous helium at the same temperature for three major austenitic stainless steels, JIS SUS304L, 316L and 316LN, extensively used for cryogenic applications including liquid hydrogen transportation and storage vessels. Stress-strain curves were considerably different between circumstances and also specimen diameter, resulting in differences of strength and ductility. In liquid hydrogen, serrated deformation appeared after considerable work hardening and more active in specimens with larger diameter. Meanwhile serrated deformation was observed from the early stage of plastic deformation in gaseous helium at 20 K and serration was more frequent in specimens with smaller diameter. The serrated deformation behaviors were numerically simulated for 304L steel with taking thermal properties such as thermal conductivity, specific heat, heat transfer from specimens to cryogenic media into account, and some agreement with the experiments was obtained.

  17. 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.

  18. Photo-excited states in germanium at liquid-helium temperatures

    SciTech Connect

    Culbertson, J.C.

    1982-12-01

    A wide variety of experimental work dealing with the basic properties of photoexcited states in Ge at liquid helium temperatures is presented. The primary emphasis is on the electron-hole liquid (EHL) and the free exciton (FE). The EHL is composed of two interpenetrating Fermi liquids, one of electrons and one of holes, each with its own Fermi level. The FE dealt with here is a mobile, loosely bound state of an electron and a hole. We report the first absolute measurement of the density dependence of the enhancement factor g/sub eh/(0) for the EHL in Ge. This factor g/sub eh/(0) is a measure of the electron-hole spatial correlation function, and provides a valuable and sensitive test for the predictions of various many-body-theory approximations. An EHL droplet - FE gas system confined to a strain induced potential well was used. The measurement approach relied on only a few simple and verifiable assumptions. A byproduct of this work was the measurement as a function of stress of: the electron and hole Fermi levels E/sub F//sup e/ and E/sub F//sup h/, the EHL density n/sub l/, the condensation energy phi of a FE relative to the EHL, and the binding energy of a FE (E/sub x/) relative to free carriers (FC). The decay of a FE-FC system confined to a strain induced potential well is studied. The first direct measurement of the FE diffusivity D/sub x/ is reported. The evolution in time of spatial profiles of FE luminescence were measured. From these FE density profiles, D/sub x/(4.2K) approx. = to 300 cm/sup 2/ s/sup -1/, the surface recombination velocity S approx. = 3000 cm s/sup -1/, and the FE lifetime tau/sub x/ = 27 ..mu..s with surface effects excluded were determined. (WHK)

  19. 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.

  20. Electron mobility in liquid and supercritical helium measured using corona discharges: a new semi-empirical model for cavity formation.

    PubMed

    Aitken, F; Li, Z-L; Bonifaci, N; Denat, A; von Haeften, K

    2011-01-14

    Electron mobilities in supercritical and liquid helium were investigated as a function of the density. The mobilities were derived from I(V) curves measured in a high-pressure cryogenic cell using a corona discharge in point-plane electrode geometry for charge generation. The presented data spans a wide pressure and temperature range due to the versatility of our experimental set-up. Where data from previous investigations is available for comparison, very good agreement is found. We present a semi-empirical model to calculate electron mobilities both in the liquid and supercritical phase. This model requires the electron-helium scattering length and thermodynamic state equations as the only input and circumvents any need to consider surface tension. Our semi-empirical model reproduces experimental data very well, in particular towards lower densities where transitions from localised to delocalised electron states were observed. PMID:21052578

  1. Two new vortex liquids

    NASA Astrophysics Data System (ADS)

    Anderson, Philip W.

    2007-03-01

    In 1967, Reatto and Chester proposed that solid helium-4 might exhibit superfluidity, and in 1970, Leggett suggested what was thought to be a definitive experimental test: to find non-classical rotational inertia in a toroidal sample. More than three decades later, the observation by Kim and Chan of exactly that effect generated great interest and has been repeated and confirmed by a number of groups. However, many attempts to find actual superflow in truly solid samples have failed. Here, I draw an analogy with a second example of anomalous response to vorticity in a dissipative fluid, the vortex liquid phase in the pseudogap region of high-temperature superconductors, and propose that the solid helium experiments have been mischaracterized: what is observed is not supersolidity but an incompressible vortex liquid. This state is distinct from a conventional liquid in that its properties are dominated by conserved supercurrents flowing around a thermally fluctuating tangle of vortices.

  2. 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.

  3. 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.

  4. Thermal analysis of the cryocooled superconducting magnet for the liquid helium-free hybrid magnet

    NASA Astrophysics Data System (ADS)

    Ishizuka, Masayuki; Hamajima, Takataro; Itou, Tomoyuki; Sakuraba, Junji; Nishijima, Gen; Awaji, Satoshi; Watanabe, Kazuo

    2010-12-01

    The liquid helium-free hybrid magnet, which consists of an outer large bore cryocooled superconducting magnet and an inner water-cooled resistive magnet, was developed for magneto-science in high fields. The characteristic features of the cryogen-free outsert superconducting magnet are described in detail in this paper. The superconducting magnet cooled by Gifford-McMahon cryocoolers, which has a 360 mm room temperature bore in diameter, was designed to generate high magnetic fields up to 10 T. The hybrid magnet has generated the magnetic field of 27.5 T by combining 8.5 T generation of the cryogen-free superconducting magnet with 19 T generation of the water-cooled resistive magnet. The superconducting magnet was composed of inner NbSn coils and outer NbTi coils. In particular, inner NbSn coils were wound using high-strength CuNi-NbTi/NbSn wires in consideration of large hoop stress. Although the cryocooled outsert superconducting magnet achieved 9.5 T, we found that the outsert magnet has a thermal problem to generate the designed maximum field of 10 T in the hybrid magnet operation. This problem is associated with unexpected AC losses in NbSn wires.

  5. 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.

  6. 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.

  7. Operating parameters of liquid helium transfer lines used with continuous flow cryostats at low sample temperatures

    NASA Astrophysics Data System (ADS)

    Dittmar, N.; Welker, D.; Haberstroh, Ch; Hesse, U.; Krzyzowski, M.

    2015-12-01

    Continuous flow cryostats are used to cool samples to a variable temperature level by evaporating a cryogen, e.g. liquid helium (LHe). For this purpose LHe is usually stored outside the cryostat in a mobile dewar and supplied through a transfer line. In general, the complete setup has to be characterised by the lowest possible consumption of LHe. Additionally, a minimum sample temperature can be favourable from an experimental point of view. The achievement of both requirements is determined by the respective cryostat design as well as by the transfer line. In the presented work operating data, e.g. the LHe consumption during cooldown and steady state, the minimum sample temperature, and the outlet quality are analysed to characterise the performance of a reference transfer line. In addition, an experimental transfer line with built-in pressure sensors has been commissioned to examine the pressure drop along the transfer line, too. During the tests LHe impurities occurred which restricted a steady operation.

  8. Heat Capacity of Superfluid (sup 4)He in the Presence of a Heat Current Near T

    NASA Technical Reports Server (NTRS)

    Chui, Talso C. P.; Goodstein, David L.; Harter, Alexa W.; Mukhopadhyay, Ranjan

    1996-01-01

    The thermodynamic theory of superfluid helium in the presence of a heat current is presented. We show that there is a thermodynamic relation between the heat capacity and the expression ps(W), which describes the depression of the superfluid density with the counterflow velocity W. Using this relation we show that the heat capacity of superfluid super4He in the presence of a heat current diverges at a depressed lambda transition temperature, suggesting the possibility of a new second order phase transition where the superfluid wave function is not the order parameter.

  9. Formation of a Mesa Shaped Phonon Pulse in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Adamenko, I. N.; Nemchenko, K. E.; Slipko, V. A.

    2010-05-01

    We present a theory for the formation of a mesa shaped phonon pulse in superfluid 4He. Starting from the hydrodynamic equations of superfluid helium, we obtain the system of equations which describe the evolution of strongly anisotropic phonon systems. Such systems can be created experimentally. The solution of the equations are simple waves, which correspond to second sound in the moving phonon pulse. Using these exact solutions, we describe the expansion of phonon pulses in superfluid helium at zero temperature. This theory gives an explanation for the mesa shape observed in the measured phonon angular distributions. Almost all dependencies of the mesa shape on the system parameters can be qualitatively understood.

  10. Anisotropic System of Quasiparticles in Superfluid Helium

    SciTech Connect

    Adamenko, I.N.; Nemchenko, K.E.; Slipko, V.A.; Wyatt, A.F.G.

    2006-02-17

    The thermodynamic properties of anisotropic quasiparticle systems of He II are considered for all degrees of anisotropy. It is shown that the thermodynamic functions of a strongly anisotropic phonon-roton system are mainly determined by rotons at all temperatures. Analytical expressions for the roton thermodynamic functions are obtained for all degrees of anisotropy. The maximum anisotropy is limited by the criterion for thermodynamic stability, which is here derived for the whole temperature range.

  11. Liquid-helium temperature long-path infrared spectroscopy of molecular clusters and supercooled molecules

    NASA Astrophysics Data System (ADS)

    Bauerecker, Sigurd; Taraschewski, Michael; Weitkamp, Claus; Cammenga, Heiko K.

    2001-10-01

    Collisional cooling and supersonic jet expansion both allow us to perform infrared spectroscopy of supercooled molecules and atomic and molecular clusters. Collisional cooling has the advantage of higher sensitivity per molecule and enables working in thermal equilibrium. A new powerful method of collisional cooling is presented in this article. It is based on a cooling cell with integrated temperature-invariant White optics and pulsed or continuous sample-gas inlet. The system can be cooled with liquid nitrogen or liquid helium and operated at gas pressures between <10-5 and 13 bar. Temperatures range from 4.2 to 400 K and can be adjusted to an accuracy of ±0.2 K over most of the useable range. A three-zone heating design allows homogeneous or inhomogeneous temperature distributions. Optical path lengths can be selected up to values of 20 m for Fourier transform infrared (FTIR) and 40 m for laser operation. The cell axis is vertical, so optical windows are at room temperature. Diffusive trapping shields and low-power electric heating keep the mirrors free from perturbing deposits. The cell can be operated in a dynamic buffer-gas flow-cooling mode. A comprehensive review of existing collisional cooling cells is given. The formation of CO clusters from the gas phase was investigated using FTIR spectroscopy. For the isotope mixture consisting of 13C16O,13C18O, and 12C16O, a conspicuous change in the main spectroscopic structure of the clusters was observed between 20 and 5 K. The cluster bandwidth of the main isotope 13C16O triples. This behavior could be interpreted as a change from the crystalline to the amorphous state or as a decrease in size to smaller clusters with relatively larger surfaces. To our knowledge, this is the first IR investigation of molecular clusters obtained by collisional cooling in this temperature range. For CO2 the change from the monomer to crystalline clusters was investigated. The observed spectra vary considerably with temperature

  12. Experimental study of nanofluidics and phase transitions of normal and superfluid 4He

    NASA Astrophysics Data System (ADS)

    Velasco, Angel Enriques

    This thesis addresses the experimental results of two different research topics. The first is the experimental work of pressure driven flows in the smallest, single nanotubes ever investigated. The nanotube boundary conditions and slip lengths from argon, nitrogen, water, and helium experiments were analyzed and compared to macroscopic boundary conditions. The second research topic discusses the work on ellipsometric and quartz microbalance measurements of the 2D superfluid phase diagram of 4He on alkali substrates. Ellipsometric results of sodium on HOPG provide the first evidence of the existence of the 2D critical point on an intermediate strength substrate. Pressure driven flows through single nanopores and microtubes were measured with a calibrated mass spectrometer with pressure drops up to 30 Atm. The nanopores were between 30 nm to 600 nm in diameter and etched in mica and PET membranes of several microns thickness. Microtubes several inches long of fused quartz and nickel material were tested with diameters between 1.8 micron and 25 micron. For 4He and argon gas we observed the flow transition between the free molecular and continuum regimes at 293 K and 77 K. No discrepancy between the macroscopic theory and the 30 nm nanopore data was found. Because of the exceptionally low viscosity of gaseous helium the laminar-turbulent transition could also be observed within these submicron channels. The small viscosity of 4He was too small to dampen inertial effects at a Reynolds number of 2000. In addition to single phase gas flows, our experimental technique also allows us to investigate flows in which the nano or micro scale pipe is either partially or completely filled with liquids. The position of the intrinsic liquid/vapor interface was important for understanding this type of flow. Strong evaporation and cooling at the liquid-vapor interface can lead to freezing for conventional fluids such as nitrogen and water, which in turn leads to complex intermittent

  13. Test program, helium II orbital resupply coupling

    NASA Technical Reports Server (NTRS)

    Hyatt, William S.

    1991-01-01

    The full scope of this program was to have included development tests, design and production of custom test equipment and acceptance and qualification testing of prototype and protoflight coupling hardware. This program was performed by Ball Aerospace Systems Division, Boulder, Colorado until its premature termination in May 1991. Development tests were performed on cryogenic face seals and flow control devices at superfluid helium (He II) conditions. Special equipment was developed to allow quantified leak detection at large leak rates up to 8.4 x 10(exp -4) SCCS. Two major fixtures were developed and characterized: The Cryogenic Test Fixture (CTF) and the Thermal Mismatch Fixture (Glovebox). The CTF allows the coupling hardware to be filled with liquid nitrogen (LN2), liquid helium (LHe) or sub-cooled liquid helium when hardware flow control valves are either open or closed. Heat leak measurements, internal and external helium leakage measurements, cryogenic proof pressure tests and external load applications are performed in this fixture. Special reusable MLI closures were developed to provide repeatable installations in the CTF. The Thermal Mismatch Fixture allows all design configurations of coupling hardware to be engaged and disengaged while measuring applied forces and torques. Any two hardware components may be individually thermally preconditioned within the range of 117 deg K to 350 deg K prior to engage/disengage cycling. This verifies dimensional compatibility and operation when thermally mismatched. A clean, dry GN2 atmosphere is maintained in the fixture at all times. The first shipset of hardware was received, inspected and cycled at room temperature just prior to program termination.

  14. Small Multielectron Bubbles in Bulk Superfluid 4He

    SciTech Connect

    Lehtovaara, Lauri; Eloranta, Jussi

    2006-09-07

    A computational method for describing multielectron bubbles in bulk superfluid helium (4He) is described. The developed method can be used to study their stability and spectroscopic properties in both singlet and triplet manifolds. Our initial results indicate meta-stability of the spherical two-electron bubble in its singlet ground state.

  15. Superfluid Reynolds number and the transition from potential flow to turbulence in superfluid 4He at millikelvin temperatures

    NASA Astrophysics Data System (ADS)

    Schoepe, W.

    2015-07-01

    This comment is on Phys. Rev. Lett. 144, 155302 (2015) by M.T. Reeves, T.P. Billam, B.P. Anderson, and A.S. Bradley "Identifying a superfluid Reynolds number via dynamical similarity" where a new superfluid Reynolds number is introduced. This definition is shown to be useful in the data analysis of the finite lifetime of turbulence observed with an oscillating sphere in superfluid helium at mK temperatures in a small velocity interval Δ v = ( v-v c ) just above the critical velocity v c . The very rapid increase in the lifetime with increasing superfluid Reynolds number is compared with the "supertransient" turbulence observed in classical pipe flow.

  16. Superfluid 3He—the Early Days

    NASA Astrophysics Data System (ADS)

    Lee, D. M.; Leggett, A. J.

    2011-08-01

    A history is given of liquid 3He research from the time when 3He first became available following World War II through 1972 when the discovery of the superfluid phases was made. The Fermi liquid nature was established early on, and the Landau Fermi liquid theory provided a framework for understanding the interactions between the Fermions (quasiparticles). The theory's main triumph was to predict zero sound, which was soon discovered experimentally. Experimental techniques are treated, including adiabatic demagnetization, dilution refrigerator technology, and Pomeranchuk cooling. A description of the superfluid 3He discovery experiments using the latter two of these techniques is given. While existing theories provided a basis for understanding the newly discovered superfluid phases in terms of ℓ>0 Cooper pairs, the unexpected stability of the A phase in the high- P, high- T region of the phase diagram needed for its explanation a creative leap beyond the BCS paradigm. The use of sum rules to interpret some of the unusual magnetic resonance in liquid 3He is discussed. Eventually a complete theory of the spin dynamics of superfluid 3He was developed, which predicted many of the exciting phenomena subsequently discovered.

  17. Helicity in superfluids

    NASA Astrophysics Data System (ADS)

    Kedia, Hridesh; Kleckner, Dustin; Proment, Davide; Irvine, William T. M.

    Ideal fluid flow conserves a special quantity known as helicity, in addition to energy, momentum and angular momentum. Helicity can be understood as a measure of the knottedness of vortex lines of the flow, providing an important geometric tool to study diverse physical systems such as turbulent fluids and plasmas. Since superfluids flow without resistance just like ideal (Euler) fluids, a natural question arises: Is there an extra conserved quantity akin to helicity in superfluids? We address the question of a ''superfluid helicity'' theoretically and examine its consequences in numerical simulations.

  18. Superfluidity of grain boundaries and supersolid behavior.

    PubMed

    Sasaki, S; Ishiguro, R; Caupin, F; Maris, H J; Balibar, S

    2006-08-25

    When two communicating vessels are filled to a different height with liquid, the two levels equilibrate because the liquid can flow. We have looked for such equilibration with solid (4)He. For crystals with no grain boundaries, we see no flow of mass, whereas for crystals containing several grain boundaries, we detect a mass flow. Our results suggest that the transport of mass is due to the superfluidity of grain boundaries. PMID:16873608

  19. Holographic p -wave superfluid

    NASA Astrophysics Data System (ADS)

    Wu, Ya-Bo; Lu, Jun-Wang; Zhang, Wen-Xin; Zhang, Cheng-Yuan; Lu, Jian-Bo; Yu, Fang

    2014-12-01

    In the probe limit, we numerically construct a holographic p -wave superfluid model in the four-dimensional (4D) and five-dimensional (5D) anti-de Sitter black holes coupled to a Maxwell-complex vector field. We find that, for the condensate with the fixed superfluid velocity, the results are similar to the s -wave cases in both 4D and 5D spacetimes. In particular, the Cave of Winds and the phase transition, always being of second order, take place in the 5D case. Moreover, we find that the translating superfluid velocity from second order to first order S/yμ increases with the mass squared. Furthermore, for the supercurrent with fixed temperature, the results agree with the Ginzburg-Landau prediction near the critical temperature. In addition, this complex vector superfluid model is still a generalization of the SU(2) superfluid model, and it also provides a holographic realization of the H e3 superfluid system.

  20. Strain-cycling fatigue behavior of ten structural metals tested in liquid helium (4 K), in liquid nitrogen (78 K), and in ambient air (300 K)

    NASA Technical Reports Server (NTRS)

    Nachtigall, A. J.

    1974-01-01

    Strain-cycling fatigue behavior of 10 different structural alloys and metals was investigated in liquid helium (4 K), in liquid nitrogen (78 K), and in ambient air (300 K). At high cyclic lives, fatigue resistance increased with decreasing temperature for all the materials investigated. At low cyclic lives, fatigue resistance generally decreased with decreasing temperature for the materials investigated. Only for Inconel 718 did fatigue resistance increase with decreasing temperature over the entire life range investigated. Comparison of the experimental fatigue behavior with that predicted by the Manson method of universal slopes showed that the fatigue behavior of these materials can be predicted for cryogenic temperatures by using material tensile properties obtained at those same temperatures.

  1. Precise Measurements of the Density and Critical Phenomena Near Phase Transitions in Liquid Helium

    NASA Technical Reports Server (NTRS)

    Yeh, Nai-Chang

    1997-01-01

    The first-year progress for the project of precise measurements of the density and critical phenomena of helium near phase transitions is summarized below: (1) completion of a cryogenic sample probe for the proposed measurements, and the rehabilitation of a designated laboratory at Caltech for this project; (2) construction and testing of a superconducting niobium cavity; (3) acquisition of one phase-locked-loop system for high-resolution frequency control and read- out; (4) setting up high-resolution thermometry (HRT) for temperature readout and control; (5) developing new approaches for calibrating the coefficient between the resonant frequency shift (delta f) and the helium density (rho), as well as for measuring the effect of gravity on T(sub lambda) to a much better precision; (6) programming of the interface control of all instruments for automatic data acquisition; and (7) improving data analyses and fitting procedures.

  2. Calculation of the pressure rise in the CHL 5000-gallon liquid-helium dewar

    SciTech Connect

    Walker, R.

    1983-01-04

    The writing of a computer program to calculate the pressure rise in the CHL 5000-gallon dewar was motivated by the writing of a Fermilab engineering note on the safety of the dewar which is presently being installed at the Fermilab Central Helium Liquefier. The calculation is intended to verify that the pressure in the inner vessel will not rise above a safe level in a catastrophic venting situation.

  3. Polarization of He II films upon the relative motion of the superfluid component and the quantized vortices

    NASA Astrophysics Data System (ADS)

    Adamenko, I. N.; Nemchenko, E. K.

    2016-04-01

    Theoretical study of the electrical activity of the saturated superfluid helium (He II) film upon the relative motion of the normal and superfluid components in the film was performed. The polarization vector due to the dipole moments of the quantized vortex rings in He II in the field of van der Waals forces was calculated taking into account the relative motion of the normal and superfluid components. An explicit analytical expression for the electric potential difference arising upon the relative motion of the normal and superfluid components in a torsional oscillator was derived. The obtained time, temperature and relative velocity dependences of the potential difference were in agreement with the experimental data.

  4. A cryogenic test stand for full length SSC magnets with superfluid capability

    SciTech Connect

    Peterson, T.J.; Mazur, P.O.

    1989-02-01

    The Fermilab Magnet Test Facility performs testing of the full scale SSC magnets on test stands capable of simulating the cryogenic environment of the SSC main ring. One of these test stands, Stand 5, also has the ability to operate the magnet under test at temperatures from 1.8K to 4.5K with either supercritical helium or subcooled liquid, providing at least 25 Watts of refrigeration. At least 50 g/s flow is available from 2.3K to 4.5K, whereas superfluid operation occurs with zero flow. Cooldown time from 4.5K to 1.8K is 1.5 hours. A maximum current capability of 10,000 amps is provided, as is instrumentation to monitor and control the cryogenic conditions. This paper describes the cryogenic design of this test stand. 8 refs., 6 figs.

  5. Laser-Assisted Detection of Metal Nanoparticles in Liquid He-II.

    PubMed

    Fernandez, Victor; Garcia, Allan; Vossoughian, Kaveh; Popov, Evgeny; Garrett, Simon; Eloranta, Jussi

    2015-11-01

    The formation of gas bubbles surrounding laser heated copper nanoparticles in superfluid helium at 1.7 K is observed. Because of the effective light capture by these plasmonic particles and the subsequent heat transfer into the liquid, such bubbles grow within 3 μs to tens of micrometers in size. The Schlieren imaging technique is used to determine the spatial distribution of the nanoparticles in the liquid, and the gas bubble radii are related to the parent nanoparticle size. The presented liquid-phase particle size analysis is validated against atomic force microscopy measurements of nanoparticles deposited from the liquid onto a solid substrate. PMID:26474093

  6. Ultrabaric relativistic superfluids

    NASA Astrophysics Data System (ADS)

    Papini, G.; Weiss, M.

    1985-09-01

    Ultrabaric superfluid solutions are obtained for Einstein's equations to examine the possibility of the existence of superluminal sound speeds. The discussion is restricted only by requiring the energy-momentum tensor and the equation of state of matter to be represented by full relativistic equations. Only a few universes are known to satisfy the conditions, and those exhibit tension and are inflationary. Superluminal sound velocities are shown, therefore, to be possible for the interior Schwarzchild metric, which has been used to explain the red shift of quasars, and the Stephiani solution (1967). The latter indicates repeated transitions between superluminal and subliminal sound velocities in the hyperbaric superfluid of the early universe.

  7. Vortex knottiness in superfluids

    NASA Astrophysics Data System (ADS)

    Kedia, Hridesh; Kleckner, Dustin; Proment, Davide; Irvine, William

    2015-11-01

    Recent work has demonstrated that linked and knotted vortices will spontaneously unknot or untie in both classical fluids and superfluids. This effect would appear to jeopardize any notion of conservation of fluid topology (helicity), but this need not be the case: vortices can transfer their knottedness to helical coils, preserving some measure of the original topology. We ask how this notion of topology preservation behaves in the context of collections of vortices with topology. We address this question by numerical simulations of superfluid vortices in the Gross-Pitaevskii equation.

  8. Excitations of Superfluid He4 Beyond the Roton

    NASA Astrophysics Data System (ADS)

    Sakhel, Asaad; Glyde, Henry

    2001-03-01

    Excitations of Superfluid ^4He Beyond the Roton. A. R. SAKHEL and H. R. GLYDE, University of Delaware - We present a Quantum Field Theoretical Model that reproduces the basic features of the temperature dependence of the dynamic structure factor S(Q,ω) as observed in the inelastic-neutron scattering results at IRIS, (J.V. Pierce, R.T. Azuah, B.Fåk, A.R. Sakhel, H.R. Glyde, and W.G. Stirling, to be published.) UK. The range of the wavevector Q beyond the roton (Q > 2.0Åis considered. The model is able to simulate the decay of the excitations into two rotons when the excitation energy exceeds 2Δ, where Δ is the roton energy. The model is based on the formulation of S(Q,ω) of Gavoret and Nozières.(J. Gavoret and Nozières, Ann. Phys.), 28, 349-399 (1964). The component of dynamic susceptibility involving the condensate is modelled by an equation of the form: \\chis = n n_0(T) Λ G Λ where Λ is a vertex, G the renormalized single particle Green's function, n the density of ^4He at SVP and n_0(T) the condensate fraction as a function of temperature. The dynamic susceptibility involving states above the condensate is modelled by a damped harmonic oscillator function.(H. R. Glyde, Excitation in Liquid and Solid Helium), Oxford, Clarendron Press (1994).

  9. Contribution to the study of heat transfer mechanisms in He. Application to the stabilization of superconductors by superfluid He

    NASA Astrophysics Data System (ADS)

    Gentile, D.

    1980-04-01

    Models were developed of the mechanics of heat transfer between a solid and liquid or superfluid helium in the case where the thermal perturbation applied to the solid is of sufficiently long duration to be able to speak of continuous evacuation and where the perturbation is of short duration to speak of a transient state. The mechanics of heat transfer were studied in the steady state in the case of a channel locally heated in vertical and horizontal position by saturated helium and at one atmosphere. Heat transfer curves were obtained by measuring the temperature of the solid and the thermal gradients in the fluid. Numerical values are given for the maximum propagation flows and minimum recovery flows, heat transfer coefficients, thermal oscillation phenomena and hysteresis phenomena according to the geometrical parameters of the pipe, the surface state of the solid, the relative dimensions of the solid and the liquid volume, the state and nature of the fluid. The thermal fluctuations found experimentally in certain temperature and pressure conditions are interpreted in terms of the formation of gas bubbles on the surface of the solid and in terms of acoustic wave phenomena in the channel and the cavity created by the helium bath.

  10. Detecting continuous gravitational waves with a jug of superfluid

    NASA Astrophysics Data System (ADS)

    Singh, Swati; Delorenzo, Laura; Pearlman, Adam; Pikovski, Igor; Blencowe, Miles; Schwab, Keith

    We investigate the sensitivity to narrow band, continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of superfluid helium-4 parametrically coupled to a super-conducting microwave cavity. This narrowband detection scheme is tunable through pressurization of the helium, thereby making both doppler tracking of astrophysical sources and tuning the detector on/off from the source possible. For reasonable experimental parameters, we find that gravitational metric strain fields from nearby pulsars could be detected with a few weeks of integration time.

  11. Detecting continuous gravitational waves with a jug of superfluid

    NASA Astrophysics Data System (ADS)

    Singh, Swati; de Lorenzo, Laura; Pearlman, Adam; Pikovski, Igor; Schwab, Keith

    2016-05-01

    We investigate the sensitivity to narrow band, continuous-wave strain fields of a kg-scale optomechanical system formed by the acoustic motion of superfluid helium-4 parametrically coupled to a super-conducting microwave cavity. This narrowband detection scheme is tunable through pressurization of the helium, thereby making both doppler tracking of astrophysical sources and tuning the detector on/off from the source possible. For reasonable experimental parameters, we find that gravitational metric strain fields from nearby pulsars could be detected with a few weeks of integration time.

  12. Anisotropic superfluidity in a dipolar Bose gas

    SciTech Connect

    Ticknor, Christopher; Wilson, Ryan M; Bohn, John L

    2010-11-04

    A quintessential feature of superfluidity is the ability to support dissipationless flow, for example, when an object moves through a superfluid and experiences no drag. This, however, only occurs when the object is moving below a certain critical velocity; when it exceeds this critical velocity it dissipates energy into excitations of the superfluid, resulting in a net drag force on the object and the breakdown of superfluid flow. In many superfluids, such as dilute Bose-Einstein condensates (BECs) of atoms with contact interactions, this critical velocity is simply the speed of sound in the system, where the speed of sound is set by the density and the s-wave scattering length of the atoms. However, for other superfluids, such as liquid {sup 4}He, this is not the case. In {sup 4}He, the critical velocity is set by a roton mode, corresponding to a peak in the static structure factor of the system at some finite, non-zero momentum, with a characteristic velocity that is considerably less than the speed of sound in the liquid. This feature has been verified experimentally via measurements of ion-drift velocity in the fluid, thereby providing insight into the detailed structure of the system. Interestingly, a roton-like feature was predicted to exist in the dispersion relation of a quasi-two-dimensional (q2D) dipolar BEC (DBEC) [16], or a BEC with dipole-dipole interactions. However, unlike the dispersion of {sup 4}He, the disperSion of a DBEC is highly tunable as a function of the condensate density or dipole-dipole interaction (ddi) strength. Additionally, the DBEC is set apart from liquid {sup 4}He in that its interactions depend on how the dipoles are oriented in space. Thus, the DBEC provides an ideal system to study the effects that anisotropies have on the bulk properties of a superfluid, such as the critical velocity. Here we consider a DBEC in a quasi-two-dimensional (q2D) geometry and allow for the dipoles to be polarized at a nonzero angle into the plane

  13. A novel coupled VM-PT cryocooler operating at liquid helium temperature

    NASA Astrophysics Data System (ADS)

    Pan, Changzhao; Zhang, Tong; Zhou, Yuan; Wang, Junjie

    2016-07-01

    This paper presents experimental results on a novel two-stage gas-coupled VM-PT cryocooler, which is a one-stage VM cooler coupled a pulse tube cooler. In order to reach temperatures below the critical point of helium-4, a one-stage coaxial pulse tube cryocooler was gas-coupled on the cold end of the former VM cryocooler. The low temperature inertance tube and room temperature gas reservoir were used as phase shifters. The influence of room temperature double-inlet was first investigated, and the results showed that it added excessive heat loss. Then the inertance tube, regenerator and the length of the pulse tube were researched experimentally. Especially, the DC flow, whose function is similar to the double-orifice, was experimentally studied, and shown to contribute about 0.2 K for the no-load temperature. The minimum no-load temperature of 4.4 K was obtained with a pressure ratio near 1.5, working frequency of 2.2 Hz, and average pressure of 1.73 MPa.

  14. Momentum density of hcp and liquid helium-4 by inelastic neutron scattering

    SciTech Connect

    Hilleke, Russell Otto

    1983-01-01

    A measurement of the momentum density in hcp and liquid /sup 4/He by inelastic neutron scattering is reported. Using the Low Resolution Medium Energy Chopper Spectrometer at the Intense Pulsed Neutron Source at Argonne National Laboratory, momentum transfers in the range 12 to 22.5 A/sup -1/ were attained. At these momentum transfers, the momentum density of the sample is related to the dynamic structure factor by the impulse approximation. The measured momentum distribution is Gaussian and the kinetic energy is larger than proposed by existing theories. Data were taken on two solid samples, the first was a 19.45 cm/sup 3//mole hcp solid, the second was 18.20 cm/sup 3// mole; both solid samples were maintained at 1.70 K during data collection. Data were also taken on a liquid sample with a molar volume of 18.20 cm/sup 3//mole at 4.00 K. At 1.70 K the two solid samples are essentially in their ground states so that the measurement is of the ground state momentum density. The liquid sample was included to see if the difference between the liquid and solid momentum density at the same molar volume was observable.

  15. Superfluidity in Millisecond Pulsars (Review)

    NASA Astrophysics Data System (ADS)

    Pines, D.; Alpar, A.

    The authors review the evidence for superfluidity in the Vela pulsar, the Crab pulsar and PSR 0525+21, and examine the prospects for observing similar consequences of superfluidity in the already-discovered millisec pulsars. They consider, inter alia, the likelihood of observing glitches, the expected post-glitch behavior, and pulsar heating by energy dissipation due to the creep of neutron vortex lines in pinned superfluid regions of the crust.

  16. Sound modes in holographic superfluids

    SciTech Connect

    Herzog, Christopher P.; Yarom, Amos

    2009-11-15

    Superfluids support many different types of sound waves. We investigate the relation between the sound waves in a relativistic and a nonrelativistic superfluid by using hydrodynamics to calculate the various sound speeds. Then, using a particular holographic scalar gravity realization of a strongly interacting superfluid, we compute first, second, and fourth sound speeds as a function of the temperature. The relativistic low temperature results for second sound differ from Landau's well known prediction for the nonrelativistic, incompressible case.

  17. Untangling Superfluid Vortices

    NASA Astrophysics Data System (ADS)

    Kleckner, Dustin; Scheeler, Martin W.; Proment, Davide; Irvine, William T. M.

    2015-03-01

    What is the role of topology, or knottedness, in superfluid phase defects (quantum vortices)? In ideal classical fluids, vortex knots may never untie, and so there is an associated conserved quantity - helicity - which measures how tangled a flow is. One might expect a similar robustness for superfluid defects, however, simulations of the Gross-Pitevskii equation demonstrate that vortex knots and links spontaneously untie and unlink. Nonetheless, the topology dramatically affects the vortex evolution, and a component of the initial helicity is transferred to helical coils as the knots unravel. These effects are remarkably similar to the behavior of tangled vortices in viscous fluids, suggesting they are universal features of non-ideal fluids.

  18. When superfluids are a drag

    SciTech Connect

    Roberts, David C

    2008-01-01

    The article considers the dramatic phenomenon of seemingly frictionless flow of slow-moving superfluids. Specifically the question of whether an object in a superfluid flow experiences any drag force is addressed. A brief account is given of the history of this problem and it is argued that recent advances in ultracold atomic physics can shed much new light on this problem. The article presents the commonly held notion that sufficiently slow-moving superfluids can flow without drag and also discusses research suggesting that scattering quantum fluctuations might cause drag in a superfluid moving at any speed.

  19. Helium-4 Experiments near T-lambda in a Low-Gravity Simulator

    NASA Technical Reports Server (NTRS)

    Liu, Yuanming; Larson, Melora; Israelsson, Ulf

    2000-01-01

    We report our studies of gravity cancellation in a liquid helium sample cell along the lambda-line using a low-gravity simulator facility. The simulator consists of a superconducting magnet capable of producing B(delta-B/delta-z) = 22squareT)/cm. We have verified experimentally that the simulator can cancel gravity to about 0.01g in a cylindrical sample volume of 0.5 cm in diameter and 0.5 cm in height. This allows us to approach more closely the superfluid transition without entering the normal-superfluid two phase region induced by gravity. We also present the measurements of T-c(Q,P): depression of the superfluid transition temperature by a heat current(Q) along the lambda-line (P). The results are consistent with the Renormalization-group theory calculation. Measurements of thermal expansion coefficient in a heat current will also be discussed. The work has been carried out by JPL, California Institute of Technology under contract to NASA.

  20. Sloshing dynamics on rotating helium dewar tank

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1993-01-01

    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 to perform scientific observation during the normal spacecraft operation are 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 were 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 were derived. Results were widely published in the open journals.

  1. Liquid nitrogen historical and current usage of the central helium liquefier at SNS

    NASA Astrophysics Data System (ADS)

    DeGraff, B.; Howell, M.; Kim, S.; Neustadt, T.

    2015-12-01

    The main cryogenic system for the Spallation Neutron Source (SNS) is comprised of a 4-K cold box, a 2-K cold box, six warm compressors, and ancillary support equipment. This system has been cold and operating with little disruption since 2005. Design and operation of liquid nitrogen (LN2) supplied from a single 20,000-gallon supply Dewar will be discussed. LN2 used to precool the 4-K cold box heat exchanger started to increase around 2011. LN2 Consumption during 2012 and 2013 was almost double the nominal usage rate. Studies of this data, plant parameter changes to respond to this information, and current interpretations are detailed in this paper. The usage rate of LN2 returned to normal in late 2013 and remained there until recent additional changes. Future study plans to understand potential causes of this including contamination migration within the 4-K cold box will also be addressed.

  2. Liquid helium inertial jet for comparative study of classical and quantum turbulence

    SciTech Connect

    Duri, D.; Charvin, P.; Rousset, B.; Poncet, J.-M.; Diribarne, P.

    2011-11-15

    We present a new cryogenic wind tunnel facility developed to study the high Reynolds number developed classical or quantum turbulence in liquid {sup 4}He. A stable inertial round jet flow with a Reynolds number of 4 x 10{sup 6} can be sustained in both He I and He II down to a minimum temperature of 1.7 K. The circuit can be pressurized up to 3.5 x 10{sup 5} Pa. The system has been designed to exploit the self-similar properties of the jet far field in order to adapt to the spatial resolution of the existing probes. Multiple and complementary sensors can be simultaneously installed to obtain spatial and time resolved measurements. The technical difficulties and design details are described and the system performance is presented.

  3. Massless surface waves between two different superfluid phases of 3He

    NASA Astrophysics Data System (ADS)

    Todoshchenko, I.

    2016-04-01

    An interface between two media is a topologically stable two-dimensional object where 3D-symmetry breaks which allows for the existence of many exotic excitations. A direct way to explore surface excitations is to investigate their interaction with the surface waves, such as very well known capillary-gravity waves and crystallization waves. Helium remains liquid down to absolute zero where bulk excitations are frozen out and do not mask the interaction of the waves with the surface states. Here we show the possibility of the massless wave which can propagate along the surface between two different superfluids phases of 3He . The displacement of the surface in this wave occurs due to the transition of helium atoms from one phase to another, so that there is no flow of particles as densities of phases are equal. We calculate the dispersion of the wave in which the inertia is provided by spin supercurrents, and the restoring force is magnetic field gradient. We calculate the dissipation of the wave and show the preferable conditions to observe it.

  4. Bose Einstein condensation: Its role in the excitations of liquid helium and in trapped Bose gases

    NASA Astrophysics Data System (ADS)

    Sakhel, Asaad R.

    The role of Bose-Einstein condensation (BEC) in determining the properties of Bose systems at ultracold temperatures is investigated. First, we present a model of the dynamic structure factor S(Q,o) of liquid 4He as observed in inelastic neutron scattering measurements beyond the roton (Q ≳ 2.0 A-1). We separate the dynamic susceptibility into chi = chiS + chi'R. chi S involves states in the condensate and chi' R states above the condensate only. We find that the weight of chiS scales with the condensate fraction n0(T) and vanishes at Tlambda. chi' R is broad and largely temperature independent and a low energy intensity broadening arises from the thermal broadening of the phonon-roton (p-r) modes. Secondly, we investigate ultracold Bose gases with repulsive and attractive interactions confined in a spherical harmonic trap over a broad range of densities using model potentials and variational Monte Carlo (VMC) at T = 0 K. In the case of repulsive interactions, the Bosons are represented by hard spheres (HS)s interacting by a HS potential. We change the densities of the Bosons by increasing the s-wave scattering length a. We find that the VMC total and VMC condensate density distributions are similar in shape, they are flat nearly at the higher densities. Further the Thomas-Fermi approximation becomes invalid and the condensate is substantially depleted at the higher densities. In the case of attractive interactions, we model the interactions by a hard core square well (HCSW). We change the densities of these systems by keeping the hard core diameter, a c, fixed and increasing the potential depth V 0 or by increasing both of them simultaneously while keeping a fixed. We find that a Bose gas with attractive interactions undergoes a first order phase transition from the gas to the liquid state at a value of N|a| ≈ 0.574 in agreement with the value predicted by Gross-Pitaevskii (GP) theory. The condensate depletion is mainly driven by the HC diameter in the

  5. Reducing the Liquid Helium Consumption of Superconducting Rock Magnetometers (SRMs) used in Paleomagnetic and Rock Magnetic studies: Gallium Lubrication of Gifford-McMahon Cryocoolers Leads to a Dramatic Increase in Cool-down Efficiency, and a Drop in Liquid Helium Consumption

    NASA Astrophysics Data System (ADS)

    Kirschvink, J. L.

    2015-12-01

    Two-stage Gifford-McMahon helium-gas cryocoolers have been used for the past 40+ years in a wide variety of cryogenic applications, including reducing the liquid helium consumption of SRMs. However, the cooling efficiency depends greatly on the friction of the displacement pistons, which need to be replaced every few years. This and the rising cost of liquid helium are major headaches in the operation of modern paleomagnetic laboratories. Although the development of efficient pulse-tube cryocoolers has eliminated the need for liquid helium in new superconducting magnetometers, there are still nearly 100 older SRMs around the globe that use liquid helium. In a failed attempt to replace the Gifford-McMahon unit on one of Caltech's SRMs with a pulse-tube, we irreversibly contaminated the cylindrical surfaces of the stainless-steel heat exchanger with a thin film of gallium, a non-toxic metal that has a melting temperature of ~ 30˚C. Liquid gallium will diffuse into other metals, altering their surface properties. We noticed that the next cryocooler-assisted cool down of the SRM went nearly twice as fast as in previous cycles, and the helium boiloff rate for the past 2 years has stabilized at less than half of its average over the past 30 years. It seems that the thin layer of gallium may be reducing the sliding friction of the Gifford-McMahon cryocoolers. We recently tested this on a second SRM, with similar results. We found that the inner cryocooler surface reached its equilibrium temperature in about 1/3 of the time that it took in previous cool-down cycles. WSGI also confirmed that this cool-down was unusually efficient compared to other instruments they have built. Subsequent records of the helium gas boiloff show that this system is also running at about half of its former loss rate. Based on these two results, we tentatively recommend this simple procedure any time cold-head swaps are performed on these cryocoolers.

  6. Vibration modes of a two-dimensional Wigner lattice coupled to ripplons on a liquid-helium surface

    NASA Astrophysics Data System (ADS)

    Eguiluz, A. G.; Maradudin, A. A.; Elliott, R. J.

    1981-07-01

    We present a theory of the vibration modes of a two-dimensional Wigner lattice coupled to ripplons on a liquid-helium surface based on the use of thermodynamic Green's functions. Starting from the phonon-ripplon Hamiltonian proposed by Fisher, Halperin, and Platzman, the effects of the electron-ripplon interaction (and hence the effects of the temperature and pressing electric field) on the frequencies of the coupled phonon-ripplon modes are obtained from the poles of the Green's function for the phonons of the Wigner lattice. The nature of these poles is determined by the phonon self-energy, which clearly displays the resonant coupling between the phonons and the ripplons. Our theory gives a first-principles derivation of the weights of the ripplon-induced resonances. We present approximate analytical results for the frequencies of the coupled modes. Our results are in qualitative agreement with the experiments of Grimes and Adams and the theory of Fisher et al. However, we do not find justification for the quantitative agreement with experiment that has been reported by Fisher et al. This discrepancy has to do with the fact that we show that the aforementioned weights are not given in terms of an effective Debye-Waller factor for the 2D Wigner lattice, but rather in terms of an exponential whose argument originates from the difference in electron displacement correlation functions given by .u-->(l1t1)q-->.u-->(l2t2)>-<(q-->.u-->)2>. This being the case, the normal modes of the phonon-ripplon Hamiltonian have frequencies whose values are somewhat smaller than the frequencies of the resonances measured by Grimes and Adams.

  7. Theory of dark matter superfluidity

    NASA Astrophysics Data System (ADS)

    Berezhiani, Lasha; Khoury, Justin

    2015-11-01

    We propose a novel theory of dark matter (DM) superfluidity that matches the successes of the Λ cold dark matter (Λ CDM ) model on cosmological scales while simultaneously reproducing the modified Newtonian dynamics (MOND) phenomenology on galactic scales. The DM and MOND components have a common origin, representing different phases of a single underlying substance. DM consists of axionlike particles with mass of order eV and strong self-interactions. The condensate has a polytropic equation of state P ˜ρ3 giving rise to a superfluid core within galaxies. Instead of behaving as individual collisionless particles, the DM superfluid is more aptly described as collective excitations. Superfluid phonons, in particular, are assumed to be governed by a MOND-like effective action and mediate a MONDian acceleration between baryonic matter particles. Our framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not); due to the higher velocity dispersion in clusters, and correspondingly higher temperature, the DM in clusters is either in a mixture of superfluid and the normal phase or fully in the normal phase. The rich and well-studied physics of superfluidity leads to a number of observational signatures: an array of low-density vortices in galaxies; merger dynamics that depend on the infall velocity vs phonon sound speed; distinct mass peaks in bulletlike cluster mergers, corresponding to superfluid and normal components; and interference patters in supercritical mergers. Remarkably, the superfluid phonon effective theory is strikingly similar to that of the unitary Fermi gas, which has attracted much excitement in the cold atom community in recent years. The critical temperature for DM superfluidity is of order mK, comparable to known cold atom Bose-Einstein condensates. Identifying a precise cold atom analog would give important insights on the microphysical interactions underlying DM superfluidity

  8. A liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source

    SciTech Connect

    Yoshida, Ken-ichi Nara, Takayuki; Saitoh, Yuichi; Yokota, Watalu

    2014-02-15

    A flat distribution of the minimum magnetic field (flat-B{sub min}) of an electron cyclotron resonance ion source (ECRIS) is expected to perform better in highly charged ion production than classical B{sub min}. To form a flat-B{sub min} structure with a liquid helium-free superconducting device, a coil system of seven coils with four current leads has been designed. The lead number was reduced by connecting the plural coils in series to maintain the flat-B{sub min} structure even when the coil currents are changed for adjustment. This coil system can be operated with a helium-free cryostat, since the estimation of heat from the leads to the coils is nearly equivalent to the existing superconducting ECRIS of a similar type.

  9. A cosmic superfluid phase

    NASA Technical Reports Server (NTRS)

    Gradwohl, Ben-Ami

    1991-01-01

    The universe may have undergone a superfluid-like phase during its evolution, resulting from the injection of nontopological charge into the spontaneously broken vacuum. In the presence of vortices this charge is identified with angular momentum. This leads to turbulent domains on the scale of the correlation length. By restoring the symmetry at low temperatures, the vortices dissociate and push the charges to the boundaries of these domains. The model can be scaled (phenomenologically) to very low energies, it can be incorporated in a late time phase transition and form large scale structure in the boundary layers of the correlation volumes. The novel feature of the model lies in the fact that the dark matter is endowed with coherent motion. The possibilities of identifying this flow around superfluid vortices with the observed large scale bulk motion is discussed. If this identification is possible, then the definite prediction can be made that a more extended map of peculiar velocities would have to reveal large scale circulations in the flow pattern.

  10. Dissipative superfluid dynamics from gravity

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Jyotirmoy; Bhattacharyya, Sayantani; Minwalla, Shiraz

    2011-04-01

    Charged asymptotically AdS 5 black branes are sometimes unstable to the condensation of charged scalar fields. For fields of infinite charge and squared mass -4 Herzog was able to analytically determine the phase transition temperature and compute the endpoint of this instability in the neighborhood of the phase transition. We generalize Herzog's construction by perturbing away from infinite charge in an expansion in inverse charge and use the solutions so obtained as input for the fluid gravity map. Our tube wise construction of patched up locally hairy black brane solutions yields a one to one map from the space of solutions of superfluid dynamics to the long wavelength solutions of the Einstein Maxwell system. We obtain explicit expressions for the metric, gauge field and scalar field dual to an arbitrary superfluid flow at first order in the derivative expansion. Our construction allows us to read off the the leading dissipative corrections to the perfect superfluid stress tensor, current and Josephson equations. A general framework for dissipative superfluid dynamics was worked out by Landau and Lifshitz for zero superfluid velocity and generalized to nonzero fluid velocity by Clark and Putterman. Our gravitational results do not fit into the 13 parameter Clark-Putterman framework. Purely within fluid dynamics we present a consistent new generalization of Clark and Putterman's equations to a set of superfluid equations parameterized by 14 dissipative parameters. The results of our gravitational calculation fit perfectly into this enlarged framework. In particular we compute all the dissipative constants for the gravitational superfluid.

  11. Vortex Loops at the Superfluid Lambda Transition: An Exact Theory?

    NASA Technical Reports Server (NTRS)

    Williams, Gary A.

    2003-01-01

    A vortex-loop theory of the superfluid lambda transition has been developed over the last decade, with many results in agreement with experiments. It is a very simple theory, consisting of just three basic equations. When it was first proposed the main uncertainty in the theory was the use Flory scaling to find the fractal dimension of the random-walking vortex loops. Recent developments in high-resolution Monte Carlo simulations have now made it possible to verify the accuracy of this Flory-scaling assumption. Although the loop theory is not yet rigorously proven to be exact, the Monte Carlo results show at the least that it is an extremely good approximation. Recent loop calculations of the critical Casimir effect in helium films in the superfluid phase T < Tc will be compared with similar perturbative RG calculations in the normal phase T > Tc; the two calculations are found to match very nicely right at Tc.

  12. Far-Infrared Photometry with an 0.4-Meter Liquid Helium Cooled Balloon-Borne Telescope. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Jacobson, M. R.

    1977-01-01

    A 0.4-meter aperture, liquid helium cooled multichannel far-infrared balloon-borne telescope was constructed to survey the galactic plane. Nine new sources, above a 3-sigma confidence level of 1300 Jy, were identified. Although two-thirds of the scanned area was more than 10 degrees from the galactic plane, no sources were detected in that region; all nine fell within 10 degrees and eight of those within 4 degrees of the galactic equator. Correlations with visible, compact H lines associated with radio continuum and with sources displaying spectra steeply rising between 11 and 20 microns were noted, while stellar objects were not detected.

  13. Superfluidity in asymmetric nuclear matter

    SciTech Connect

    Sedrakian, A.; Alm, T.; Lombardo, U.

    1997-02-01

    The onset of superfluidity in isospin-asymmetric nuclear matter is investigated within the BCS theory. A neutron-proton superfluid state in the channel {sup 3}S{sub 1}-{sup 3}D{sub 1} comes about from the interplay between thermal excitations and separation {delta}{mu} of the two Fermi surfaces. The superfluid state disappears above the threshold value of the density-asymmetry parameter {alpha}=(n{sub n}{minus}n{sub p})/n{approx_equal}0.35. For large enough shift between the two Fermi surfaces {delta}{mu}=(1)/(2)({mu}{sub n}{minus}{mu}{sub p}) the transition to the normal state becomes a first-order transition and a second gap solution develops. This solution, however, corresponds to a metastable superfluid state which is unstable with respect to the transition to the normal state. {copyright} {ital 1997} {ital The American Physical Society}

  14. Superfluid Interfaces in Quantum Solids

    NASA Astrophysics Data System (ADS)

    Burovski, Evgeni; Kozik, Evgeni; Kuklov, Anatoly; Prokof'ev, Nikolay; Svistunov, Boris

    2005-04-01

    One scenario for the nonclassical moment of inertia of solid 4He discovered by Kim and Chan [Nature (London), NATUAS, 0028-0836 427, 225 (2004), 10.1038/nature02220] is the superfluidity of microcrystallite interfaces. On the basis of the most simple model of a quantum crystal—the checkerboard lattice solid—we show that the superfluidity of interfaces between solid domains can exist in a wide range of parameters. At strong enough interparticle interaction, a superfluid interface becomes an insulator via a quantum phase transition. Under the conditions of particle-hole symmetry, the transition is of the standard U(1) universality class in 3D, while in 2D the onset of superfluidity is accompanied by the interface roughening, driven by fractionally charged topological excitations.

  15. Conservation of helicity in superfluids

    NASA Astrophysics Data System (ADS)

    Kedia, Hridesh; Kleckner, Dustin; Proment, Davide; Irvine, William T. M.

    2015-03-01

    Helicity arises as a special conserved quantity in ideal fluids, in addition to energy, momentum and angular momentum. As a measure of the knottedness of vortex lines, Helicity provides an important tool for studying a wide variety of physical systems such as plasmas and turbulent fluids. Superfluids flow without resistance just like ideal (Euler) fluids, making it natural to ask whether their knottedness is similarly preserved. We address the conservation of helicity in superfluids theoretically and examine its consequences in numerical simulations.

  16. Unconventional Superfluidity in Yttrium Iron Garnet Films.

    PubMed

    Sun, Chen; Nattermann, Thomas; Pokrovsky, Valery L

    2016-06-24

    We argue that the magnon condensate in yttrium iron garnet may display experimentally observable superfluidity at room temperature despite the 100 times dominance of the normal density over superfluid ones. The superfluidity has a more complicated nature than in known superfluids since the U(1) symmetry of the global phase shift is violated by the dipolar interaction leading to the exchange of spin moment between the condensate and the crystal lattice. It produces periodic inhomogeneity in the stationary superfluid flow. We discuss the manner of observation and possible applications of magnon superfluidity. It may strongly enhance the spin-torque effects and reduce the energy consumption of the magnonic devices. PMID:27391750

  17. Unconventional Superfluidity in Yttrium Iron Garnet Films

    NASA Astrophysics Data System (ADS)

    Sun, Chen; Nattermann, Thomas; Pokrovsky, Valery L.

    2016-06-01

    We argue that the magnon condensate in yttrium iron garnet may display experimentally observable superfluidity at room temperature despite the 100 times dominance of the normal density over superfluid ones. The superfluidity has a more complicated nature than in known superfluids since the U(1) symmetry of the global phase shift is violated by the dipolar interaction leading to the exchange of spin moment between the condensate and the crystal lattice. It produces periodic inhomogeneity in the stationary superfluid flow. We discuss the manner of observation and possible applications of magnon superfluidity. It may strongly enhance the spin-torque effects and reduce the energy consumption of the magnonic devices.

  18. Infrared transmission at the 3.39 micron helium-neon laser wavelength in liquid-core quartz fibers

    NASA Technical Reports Server (NTRS)

    Majumdar, A. K.; Hinkley, E. D.; Menzies, R. T.

    1979-01-01

    Infrared transmission at the 3.39 micron helium-neon laser wavelength has been measured in a tetrachloroethylene-filled fused-quartz fiber. The loss measurements were taken for three different settings of laser light intensity using a series of neutral density filters. The average value of transmission loss at this wavelength was found to be 56 dB/km.

  19. Effect of spray cooling on heat transfer in a two-phase helium flow

    NASA Astrophysics Data System (ADS)

    Perraud, S.; Puech, L.; Thibault, P.; Rousset, B.; Wolf, P. E.

    2013-10-01

    We describe an experimental study of the phenomenon of spray cooling in the case of liquid helium, either normal or superfluid, and its relationship to the heat transfer between an atomized two-phase flow contained in a long pipe, and the pipe walls. This situation is discussed in the context of the cooling of the superconducting magnets of the Large Hadron Collider (LHC). Experiments were conducted in a test loop reproducing the LHC cooling system, in which the vapor velocity and temperature could be varied in a large range. Shear induced atomization results in the generation of a droplet mist which was characterized by optical means. The thickness of the thin liquid film deposited on the walls by the mist was measured using interdigitated capacitors. The cooling power of the mist was measured using thermal probes, and correlated to the local mist density. Analysis of the results shows that superfluidity has only a limited influence on both the film thickness and the mist cooling power. Using a simple model, we show that the phenomenon of spray cooling accounts for the measured non-linearity of the global heat transfer. Finally, we discuss the relevance of our results for cooling the final focus magnets in an upgraded version of the LHC.

  20. Measurement of wall relaxation times of polarized Helium-3 in bulk liquid Helium-4 for the neutron electric dipole moment experiment

    NASA Astrophysics Data System (ADS)

    Yoder, Jacob

    The Neutron Electric Dipole Moment (nEDM) experiment that will take place at the Spallation Neutron Source (SNS) in Oak Ridge, Tennessee will measure the electric dipole moment (EDM) of the neutron with a precision of order 10-28 e-cm, utilizing spin-polarized 3He in bulk liquid 4He to detect neutron precession in a 10 mG magnetic field and 50 kV/cm electric field. Since depolarized 3He will produce a background, relaxation of the polarized 3He, characterized by the probability of depolarization per bounce, Pd, was measured for materials that will be in contact with polarized 3He. Depolarization probabilities were determined from measurements of the longitudinal relaxation time of polarized 3He in bulk liquid 4He inside an acrylic cell coated with the wavelength shifter deuterated tetraphenyl butadiene (d-TPB), which will be used to coat the nEDM measurement cell. Relaxation measurements were also performed while rods, made from plumbing material Torlon and valve bellows material BeCu, were present in the cell. The BeCu was coated with Pyralin resin prior to relaxation measurements, while relaxation measurements were performed both before and after the Torlon rod was coated with Pyralin resin. The depolarization probabilities were found to be Pd-TPBd <1.32x10-7 PBareTorlon d=1.01+/-0.08 x10-6 PCoatedTorlon d=2.5+/-0.1 x10-7 PCoatedBeCu d=7.9+/-0.3 x10-7 The relaxation rates extrapolated from the observed values of Pd for d-TPB, coated Torlon, and coated BeCu in the nEDM apparatus were found to be consistent with design goals.

  1. Helium jet dispersion to atmosphere

    NASA Astrophysics Data System (ADS)

    Khan, Hasna J.

    On the event of loss of vacuum guard of superinsulated helium dewar, high rate of heat transfer into the tank occurs. The rapid boiling of liquid helium causes the burst disk to rupture at four atmospheres and consequently the helium passes to the atmosphere through vent lines. The gaseous helium forms a vertical buoyant jet as it exits the vent line into a stagnant environment. Characterization of the gaseous jet is achieved by detailed analysis of the axial and radial dependence of the flow parameters.

  2. Specific Heat of Helium in 2 μm3 Boxes, Coupled or Uncoupled?

    NASA Astrophysics Data System (ADS)

    Mooney, K. P.; Kimball, M. O.; Gasparini, F. M.

    2006-09-01

    We report on recent measurements of the specific heat of helium confined in pill-boxes 2 μm across and 2 μm deep made lithographically on a silicon wafer. The experimental cells distribute liquid from a bulk reservoir to ˜ 108 boxes by an array of very shallow fill-channels (0.019 μm and 0.010 μm) which represent a negligible volume compared to that of the boxes. Since the channels are so shallow, the helium in them becomes superfluid at a much lower temperature than the liquid in the boxes. Therefore, during the course of the heat capacity measurements, the liquid in the channels in always normal, and the cell would be expected to behave as a system of uncoupled boxes. We compare these measurements with one previously made of a cell where the confinement was to 1 μm boxes with an equivalent fill arrangement. While the shift in the position of the specific heat maximum relative to the 1 μm cell is what one would expect on the basis of finite-size scaling, there are discrepancies in the specific heat amplitude between the 2 μm cell utilizing different depth fill-channels, and with the 1 μm cell. It is possible that the channels, even though normal and of negligible volume, provide a weak coupling between the boxes leading to a collective rather than single-box behavior.

  3. Specific Heat of Helium in 2 {mu}m3 Boxes, Coupled or Uncoupled?

    SciTech Connect

    Mooney, K. P.; Kimball, M. O.; Gasparini, F. M.

    2006-09-07

    We report on recent measurements of the specific heat of helium confined in pill-boxes 2 {mu}m across and 2 {mu}m deep made lithographically on a silicon wafer. The experimental cells distribute liquid from a bulk reservoir to {approx} 108 boxes by an array of very shallow fill-channels (0.019 {mu}m and 0.010 {mu}m) which represent a negligible volume compared to that of the boxes. Since the channels are so shallow, the helium in them becomes superfluid at a much lower temperature than the liquid in the boxes. Therefore, during the course of the heat capacity measurements, the liquid in the channels in always normal, and the cell would be expected to behave as a system of uncoupled boxes. We compare these measurements with one previously made of a cell where the confinement was to 1 {mu}m boxes with an equivalent fill arrangement. While the shift in the position of the specific heat maximum relative to the 1 {mu}m cell is what one would expect on the basis of finite-size scaling, there are discrepancies in the specific heat amplitude between the 2 {mu}m cell utilizing different depth fill-channels, and with the 1 {mu}m cell. It is possible that the channels, even though normal and of negligible volume, provide a weak coupling between the boxes leading to a collective rather than single-box behavior.

  4. Study of Flow of Superfluid He-II Very Near Tau(sub lambda)

    NASA Technical Reports Server (NTRS)

    Mukharsky, Yury; Sukhatme, Kalyani; Pearson, David; Chui, Talso

    1999-01-01

    We report here, preliminary data from an experiment studying flow of superfluid helium through a slit orifice (of sub-micron width) very close to T(sub lambda). Critical supercurrent (I(sub c)) data is obtained from a step function drive to the diaphragm in a Helmholtz resonator cell. The superfluid density (rho(sub s)) data can be obtained from the resonant frequency of the Helmholtz oscillator, as determined by transfer function of the resonator or from the free ringing after the step function excitation. Preliminary data shows that I(sub c) is proportional to (rho(sub s))(exp 1.27) and rho(sub s)) is proportional to tau(exp 0.73), where tau is the reduced temperature. However, the magnitude of I(sub c) is much larger than expected, indicating a possible parallel flow path. Further investigations are in progress. Keywords: superfluid; hydrodynamics; critical exponent

  5. High-performance MgB2 superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

    NASA Astrophysics Data System (ADS)

    Ye, ShuJun; Song, Minghui; Matsumoto, Akiyoshi; Togano, Kazumasa; Takeguchi, Masaki; Ohmura, Takahito; Kumakura, Hiroaki

    2013-12-01

    MgB2 has a superconducting transition temperature (Tc) of 39 K, which is much higher than that for practical metallic superconductors. Thus, it is hoped that MgB2 can not only replace metallic superconductors, but can be used under liquid-helium-free conditions, for example, at temperatures of 10-20 K that can easily be achieved using cryocooling systems. However, to date, the reported critical current density (Jc) for MgB2 wires is not high enough for large-scale applications in liquid-helium-free conditions. In the present study, successful fabrication of high-performance MgB2 superconducting wires was carried out using an internal Mg diffusion (IMD) process, involving a p-dimethylbenzene (C8H10) pre-treatment of carbon-coated B powder with nanometer-sized particles. The resulting wires exhibited the highest ever Jc of 1.2 × 105 A cm-2 at 4.2 K and 10 T, and an engineering critical current density (Je) of about 1 × 104 A cm-2. Not only in 4.2 K, but also in 10 K, the Jc values for the wires fabricated in the present study are in fact higher than that for Nb-Ti wires at 4.2 K for the magnetic fields at which the measurements were carried out. At 20 K and 5 T, the Jc and Je were about 7.6 × 105 A cm-2 and 5.3 × 103 A cm-2, respectively, which are the highest values reported for MgB2 wires to date. The results of a detailed microstructural analysis suggested that the main reason for the superior electrical performance was the high density of the MgB2 layer rather than just the small grain size, and that the critical current could be further increased by suitable control of the microstructure. These high-performance IMD-processed MgB2 wires are thus promising superconductors for applications such as magnetic resonance imaging and maglev trains that can operate under liquid-helium-free conditions.

  6. Coherence length of neutron superfluids

    SciTech Connect

    De Blasio, F.V.; Hjorth-Jensen, M.; Lazzari, G.; Baldo, M.; Schulze, H.

    1997-10-01

    The coherence length of superfluid neutron matter is calculated from the microscopic BCS wave function of a Cooper pair in momentum space making use of recent nucleon-nucleon potential models and including polarization (RPA) effects. We find as our main result that the coherence length is proportional to the Fermi momentum to pairing gap ratio, in good agreement with simple estimates used in the literature, with a nearly interaction independent constant of proportionality. Our calculations can be applied to the problem of inhomogeneous superfluidity of hadronic matter in the crust of a neutron star. {copyright} {ital 1997} {ital The American Physical Society}

  7. Helium-refrigeration system

    SciTech Connect

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

    1995-08-01

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

  8. Effect of Helium Elasticity on Torsional Oscillator Measurements

    NASA Astrophysics Data System (ADS)

    Maris, Humphrey J.; Balibar, Sebastien

    2011-01-01

    In 2004 Kim and Chan performed a torsional oscillator measurement of the rotational inertia of solid helium-4. They found frequency changes which were interpreted in terms of a non-classical rotational inertia, that is a partial superfluidity or "supersolidity" of solid helium-4. Since then there have been many further studies using various versions of this technique. One important question that arises in these experiments is the possible effect on the oscillator frequency of changes in the elasticity of the solid helium; this can produce a change in frequency that adds to any effect due to superfluidity. In this paper we give a general discussion of the effect of changes in elasticity on the oscillator frequency and consider how the magnitude of the effect is influenced by the oscillator design. Our results should help make it possible to discriminate between frequency changes due to changes in elasticity and changes due to supersolidity.

  9. Liquid helium cryostat with internal fluorescence detection for x-ray absorption studies in the 2-6 keV energy region

    NASA Astrophysics Data System (ADS)

    McFarlane Holman, Karen L.; Latimer, Matthew J.; Yachandra, Vittal K.

    2004-06-01

    X-ray absorption spectroscopy (XAS) in the intermediate x-ray region (2-6 keV) for dilute biological samples has been limited because of detector/flux limitations and inadequate cryogenic instrumentation. We have designed and constructed a new tailpiece/sample chamber for a commercially available liquid helium cooled cryostat which overcomes difficulties related to low fluorescence signals by using thin window materials and incorporating an internal photodiode detector. With the apparatus, XAS data at the Cl, S, and Ca K edges have been collected on frozen solutions and biological samples at temperatures down to 60 K. A separate chamber has been incorporated for collecting room-temperature spectra of standard compounds (for energy calibration purposes) which prevents contamination of the cryostat chamber and allows the sample to remain undisturbed, both important concerns for studying dilute and radiation-sensitive samples.

  10. Superfluid Turbulence in a Nonuniform Circular Channel

    NASA Astrophysics Data System (ADS)

    Murphy, Paul Joseph

    The excess dissipation due to the presence of quantized vorticity in flowing helium has been studied extensively. The success of the microscopic theory proposed by Schwarz in describing many properties of this dissipation led to a belief that the major aspects of the problem had been understood at the microscopic level. The experiment of Kafkalidis and Tough demonstrated that a weak one dimensional nonuniformity in the flow field led to a dramatic departure between the observed behavior and the predictions of the Schwarz theory using the local uniformity approximation (LUA). The research presented in this thesis was undertaken to measure the dissipative states for thermal counterflow with a weak two dimensional nonuniformity. The experiment of Kafkalidis and Tough used a flow channel with a high aspect ratio. Such channels are known to exhibit only one state of superfluid turbulence. In this research the channel is circular in cross section and shows two distinct turbulent states (T-I and T-II). This experiment demonstrates that there is no difference in the excess dissipation for flows that are either converging or diverging. The T-I state is described by the same parameters as the T-I state in uniform channels. The turbulence exhibits front behavior at the transition between states. These conclusions are consistent with the LUA. The T-II state is at variance with the LUA, but is consistant with the results found in the Kafkalidis and Tough experiment.

  11. Critical velocity of superfluid helium flow in fine pore filters

    NASA Astrophysics Data System (ADS)

    Hofmann, A.

    1990-03-01

    Membrane filters with porosities of more than 70 pct have been proven to be useful for the fabrication of thermomechanical pumps (fountain effect pumps) with mass fluxes up to 1.7 g/sq cm at about 0.25 bar head of pressure. Different pumps made of 14 mm thick stacks of commercially available Sartorius cellulose nitrate membranes with filtration grades of 200, 50 and 10 nm have been investigated at various temperatures between 1.6 K at the inlet and 2.1 K at the outlet. By analysis of pressure and temperature measurements, it is shown that the chemical potential difference between inlet and outlet is zero up to critical flow rates very close to the peak flow and that it increases steeply when the critical flow is exceeded.

  12. Turbulence in pure superfluid flow

    SciTech Connect

    Ashton, R.A.; Opatowsky, L.B.; Tough, J.T.

    1981-03-09

    A series of experiments is described which provide an unambiguous description of the steady-state properties of turbulence in pure superfluid flow. The turbulence is qualitatively different from that observed in counterflow but comparable to the homogeneous turbulence described by theory.

  13. A recuperative superfluid stirling refrigerator

    SciTech Connect

    Brisson, J.G.; Swift, G.W.

    1993-07-01

    A superfluid Stirling refrigerator has been built with a counterflow heat exchanger serving as a recuperative regenerator. It has achieved temperatures of 296 mK with a 4% {sup 3}He-{sup 4}He mixture. Cooling power versus temperature and speed is presented for a 6.6% mixture.

  14. A Study on the Heat Transfer Properties of Pressurized Helium II through Fine Channels

    SciTech Connect

    Kimura, N.; Nakai, H.; Yamamoto, A.; Murakami, M.; Shintomi, T.

    2006-04-27

    An experimental study was carried out on the heat transfer properties of pressurized superfluid helium in the Gorter-Mellink heat transfer region. By using channels of hydraulic diameter from 5.6 x 10- through 4.81 x 10-3 m, the heat transfer properties of pressurized superfluid helium were measured in the experiment. The temperature dependence of Gorter-Mellink parameter, AGM, is revealed from the experimental results. It is also proven that AGM depend only on temperature, and not on the channel size and shape. The effect of quantized vortices on heat transfer of pressurized superfluid helium is discussed in comparison of the channel diameter with the mean vortex line spacing.

  15. Exchange Frequencies in Helium-4 Crystals with Defects

    NASA Astrophysics Data System (ADS)

    Militzer, Burkhard

    2005-03-01

    The torsional oscillator experiments by Kim and Chan indicate the presence of a superfluid flow in solid helium-4 [Science 305 (2004) 1941], which cannot be explained with the properties of a perfect h.c.p. lattice [Ceperley, Bernu, PRL 93 (2004) 155303]. Using path integral Monte Carlohttp://militzer.gl.ciw.edu simulations, we study different types of defects and stacking faults in the crystal by analyzing the frequency of ring-exchanges along the defect lines. This focus lies on identifying a mechanism that could explain the observed 1% superfluid fraction.

  16. Helium dilution refrigeration system

    DOEpatents

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  17. Helium dilution refrigeration system

    DOEpatents

    Roach, Patrick R.; Gray, Kenneth E.

    1988-01-01

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

  18. Pumping speed offered by activated carbon at liquid helium temperatures by sorbents adhered to indigenously developed hydroformed cryopanel

    NASA Astrophysics Data System (ADS)

    Gangradey, Ranjana; Shanti Mukherjee, Samiran; Panchal, Paresh; Nayak, Pratik; Agarwal, Jyoti; Rana, Chirag; Kasthurirengan, S.; Shankar Mishra, Jyoti; Patel, Haresh; Bairagi, Pawan; Lambade, Vrushabh; Sayani, Reena

    2015-12-01

    Towards the aim of developing a pump with large pumping speed of the order of 1 L/(s-cm2) or above for gases like hydrogen and helium through physical adsorption, development of activated carbon based sorbents like granules, spheres, flocked fibres, knitted and non -knitted cloth was carried out. To investigate the pumping speed offered, a test facility SSCF (Small Scale Cryopump Facility) which can take samples of hydroformed cryopanel (a technology developed in India) of size ∼500 mm × 100 mm was set up as per international standards comprising a dome mounted with gauges, calibrated leak valve, gas analyser, sorbent adhered to cryopanel etc. The cryopanel was shielded by chevron baffles. Pumping speed measurements were carried out for gases like hydrogen, helium and argon at a constant panel temperature in the pressure range of 1×10-7 to 1×10-4 mbar, and pumping speed was found to be in the range of 2000 L/s for a pressure range 1×10-6 to 1×10-4 mbar, and 4000 L/s for pressure range 1×10-7mbar and below for a pumping surface area of ∼1000 cm2 thus giving an average pumping speed of about 2 L/(s-cm2). Using the Monte Carlo codes SSCF was modelled and simulation studies performed. Parameters like sticking coefficient, capture coefficients affecting the pumping speed were studied. This paper describes the experimental setup of SSCF, experimental results and its correlation with Monte-Carlo simulation.

  19. Multicomponent polariton superfluidity in the optical parametric oscillator regime

    NASA Astrophysics Data System (ADS)

    Berceanu, A. C.; Dominici, L.; Carusotto, I.; Ballarini, D.; Cancellieri, E.; Gigli, G.; Szymańska, M. H.; Sanvitto, D.; Marchetti, F. M.

    2015-07-01

    Superfluidity, which is the ability of a liquid or gas to flow with zero viscosity, is one of the most remarkable implications of collective quantum coherence. In equilibrium systems such as liquid 4He and ultracold atomic gases, superfluid behavior conjugates diverse yet related phenomena, such as a persistent metastable flow in multiply connected geometries and the existence of a critical velocity for frictionless flow when hitting a static defect. The link between these different aspects of superfluid behavior is far less clear in driven-dissipative systems displaying collective coherence, such as microcavity polaritons, which raises important questions about their concurrency. With a joint theoretical and experimental study, we show that the scenario is particularly rich for polaritons driven in a three-fluid collective coherent regime, i.e., a so-called optical parametric oscillator. On the one hand, the spontaneous macroscopic coherence following the phase locking of the signal and idler fluids has been shown to be responsible for their simultaneous quantized flow metastability. On the other hand, we show here that the pump, signal, and idler have distinct responses when hitting a static defect; while the signal displays modulations that are barely perceptible, the ones appearing in the pump and idler are determined by their mutual coupling due to nonlinear and parametric processes.

  20. REVIEWS OF TOPICAL PROBLEMS: Superfluid properties of 3He-A

    NASA Astrophysics Data System (ADS)

    Volovik, Grigorii E.

    1984-05-01

    The unique superfluid properties which distinguish the A phase of 3He from other superfluids (He II, the B phase of 3He, and electrons in superconductors) are described. These properties result from the specific breaking of the invariance of the state under gauge transformations and rotations in orbital space, so that all the superfluid properties are related in a fundamental way to the dynamics of textures of the liquid-crystal-anisotropy vector. The flow of the superfluid component of the liquid, for example, is not a potential flow; its vortical part is related to textures. The relationship between the structure of the superfluid velocity and the nature of the symmetry breaking is analyzed in detail. Simple phenomenological considerations are used to derive an expression for the current and to explain the strange term in the current which is not present in the model of a Bose gas of molecules having a Cooper-pair structure in the A phase. The existence of a normal density at T="0" and the nonlocal properties of the density of the intrinsic orbital angular momentum of the liquid are discussed. The coexistence of superfluid properties with a nonpotential superfluid flow and also with the vanishing of the critical Landau velocity for the creation of excitations is discussed. Conditions for the global and local stability of the superfluid flow are described. The changes in stability upon changes caused in the topological structure of the order parameter by external conditions are discussed. The relaxation dynamics of a superfluid flow is analyzed. An instanton mechanism for phase slippage is analyzed; this mechanism leads to observable oscillations analogous to the ac Josephson effect in superconductors. Principles for constructing a generalized two-fluid Landau hydrodynamics taking an orbital variable into account are outlined. Continuous and singular vortex structures which arise upon rotation are discussed, as are their topology, phase transitions between them

  1. Twisted complex superfluids in optical lattices

    NASA Astrophysics Data System (ADS)

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-09-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid.

  2. Twisted complex superfluids in optical lattices.

    PubMed

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-01-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose-Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721

  3. Twisted complex superfluids in optical lattices

    PubMed Central

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2015-01-01

    We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721

  4. Intrinsic topological superfluidity - fluctuations and response

    NASA Astrophysics Data System (ADS)

    Levin, K.; Wu, Chien-Te; Anderson, Brandon; Boyack, Rufus

    Recent interest in topological superconductivity is based primarily on exploiting proximity effects to obtain this important phase. However, in cold gases it is possible to contemplate ``intrinsic'' topological superfluidity produced with a synthetic spin-orbit coupling and Zeeman field. It is important for such future experiments to establish how low in temperature one needs to go to reach the ordered phase. Similarly, it will be helpful to have a probe of the normal (pseudogap) phase to determine if the ultimate superfluid order will be topological or trivial. In this talk, we address these issues by considering fluctuation effects in such a superfluid, and calculate the critical transition temperature and response functions. We see qualitative signatures of topological superfluidity in spin and charge response functions. We also explore the suppression of superfluidity due to fluctuations, and importantly find that the temperature scales necessary to reach topological superfluidity are reasonably accessible

  5. Squeezing Superfluid from a Stone: Coupling Superfluidity and Elasticity in a Supersolid

    NASA Astrophysics Data System (ADS)

    Toner, John

    2007-05-01

    Superfluidity - the ability of liquid 4He, when cooled below 2.176 K, to flow without resistance through narrow pores - is one of the most amazing phenomena in physics. Supersolidity - the coexistence of superfluid behavior with the crystalline order of a solid---was proposed theoretically long ago as an even more exotic phase of solid 4He, but it has eluded detection until recently. In 2004, Kim and Chan( E. Kim and M. H. W. Chan, Nature (London) 427, 225 (2004); E. Kim and M. H. W. Chan, Science 305, 1941 (2004).) reported the onset of "nonclassical rotational inertia" in a torsional oscillator experiment with solid 4He, and they interpret their results as indicating the onset of supersolidity. In this talk, I'll describe what a supersolid is, discuss the Chan et al experiments (in the process revealing how to tell a raw from a hard boiled egg), and present the theory I've recently developed (with Paul Goldbart of University of Illinois at Urbana-Champaign, and Alan Dorsey of University of Florida) of the normal solid to supersolid (NS-SS) phase transition.

  6. Microphotonic Forces from Superfluid Flow

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    In cavity optomechanics, radiation pressure and photothermal forces are widely utilized to cool and control micromechanical motion, with applications ranging from precision sensing and quantum information to fundamental science. Here, we realize an alternative approach to optical forcing based on superfluid flow and evaporation in response to optical heating. We demonstrate optical forcing of the motion of a cryogenic microtoroidal resonator at a level of 1.46 nN, roughly 1 order of magnitude larger than the radiation pressure force. We use this force to feedback cool the motion of a microtoroid mechanical mode to 137 mK. The photoconvective forces we demonstrate here provide a new tool for high bandwidth control of mechanical motion in cryogenic conditions, while the ability to apply forces remotely, combined with the persistence of flow in superfluids, offers the prospect for new applications.

  7. Electron-Induced Chemistry of Cobalt Tricarbonyl Nitrosyl (Co(CO)3NO) in Liquid Helium Nanodroplets

    PubMed Central

    2015-01-01

    Electron addition to cobalt tricarbonyl nitrosyl (Co(CO3NO) and its clusters has been explored in helium nanodroplets. Anions were formed by adding electrons with controlled energies, and reaction products were identified by mass spectrometry. Dissociative electron attachment (DEA) to the Co(CO)3NO monomer gave reaction products similar to those reported in earlier gas phase experiments. However, loss of NO was more prevalent than loss of CO, in marked contrast to the gas phase. Since the Co–N bond is significantly stronger than the Co–C bond, this preference for NO loss must be driven by selective reaction dynamics at low temperature. For [Co(CO)3NO]N clusters, the DEA chemistry is similar to that of the monomer, but the anion yields as a function of electron energy show large differences, with the relatively sharp resonances of the monomer being replaced by broad profiles peaking at much higher electron energies. A third experiment involved DEA of Co(CO)3NO on a C60 molecule in an attempt to simulate the effect of a surface. Once again, broad ion yield curves are seen, but CO loss now becomes the most probable reaction channel. The implication of these findings for understanding focused electron beam induced deposition of cobalt is described. PMID:26401190

  8. Reconnection of superfluid vortex bundles.

    PubMed

    Alamri, Sultan Z; Youd, Anthony J; Barenghi, Carlo F

    2008-11-21

    Using the vortex filament model and the Gross-Pitaevskii nonlinear Schroedinger equation, we show that bundles of quantized vortex lines in He II are structurally robust and can reconnect with each other maintaining their identity. We discuss vortex stretching in superfluid turbulence and show that, during the bundle reconnection process, kelvin waves of large amplitude are generated, in agreement with the finding that helicity is produced by nearly singular vortex interactions in classical Euler flows. PMID:19113421

  9. Evidence for a Common Physical Origin of the Landau and BEC Theories of Superfluidity

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.; Azuah, R. T.; Abernathy, D. L.; Taniguchi, Junko; Suzuki, Masaru; Bossy, Jacques; Mulders, N.; Glyde, H. R.

    2014-11-01

    There are two renowned theories of superfluidity in liquid He 4 , quite different and each with specific domains of application. In the first, the Landau theory, superflow follows from the existence of a well-defined collective mode supported by dense liquid He 4 , the phonon-roton mode. In the second, superflow is a manifestation of Bose-Einstein condensation (BEC) and phase coherence in the liquid. We present combined measurements of superfluidity, BEC and phonon-roton (P-R) modes in liquid He 4 confined in the porous medium MCM-41. The results integrate the two theories by showing that well-defined P-R modes exist where there is BEC. The two are common properties of a Bose condensed liquid and either can be used as a basis of a theory of superfluidity. In addition, the confinement and disorder suppresses the critical temperature for superfluidity, Tc, below that for BEC creating a localized BEC "phase" consisting of islands of BEC and P-R modes. This phase is much like the pseudogap phase in the cuprate superconductors.

  10. Evidence for a Common Physical Origin of the Landau and BEC Theories of Superfluidity

    DOE PAGESBeta

    Diallo, Souleymane Omar; Azuah, R. T.; Abernathy, D. L.; Taniguchi, Junko; Suzuki, Masaru; Bossy, Jacques; Mulders, N.; Glyde, H. R.

    2014-11-20

    There are two renowned theories of superfluidity in liquid 4He, quite different and each with specific domains of application. In the first, the Landau theory, superflow follows from the existence of a well-defined collective mode supported by dense liquid 4He, the phonon-roton mode. In the second, superflow is a manifestation of Bose-Einstein condensation (BEC) and phase coherence in the liquid. We present combined measurements of superfluidity, BEC and phonon-roton (P-R) modes in liquid 4He confined in the porous medium MCM-41. The results integrate the two theories by showing that well-defined P-R modes exist where there is BEC. The two aremore » common properties of a Bose condensed liquid and either can be used as a basis of a theory of superfluidity. In addition, the confinement and disorder suppresses the critical temperature for superfluidity, Tc, below that for BEC creating a localized BEC phase consisting of islands of BEC and P-R modes. This phase is much like the pseudogap phase in the cuprate superconductors.« less

  11. Evidence for a common physical origin of the Landau and BEC theories of superfluidity.

    PubMed

    Diallo, S O; Azuah, R T; Abernathy, D L; Taniguchi, Junko; Suzuki, Masaru; Bossy, Jacques; Mulders, N; Glyde, H R

    2014-11-21

    There are two renowned theories of superfluidity in liquid (4)He, quite different and each with specific domains of application. In the first, the Landau theory, superflow follows from the existence of a well-defined collective mode supported by dense liquid (4)He, the phonon-roton mode. In the second, superflow is a manifestation of Bose-Einstein condensation (BEC) and phase coherence in the liquid. We present combined measurements of superfluidity, BEC and phonon-roton (P-R) modes in liquid (4)He confined in the porous medium MCM-41. The results integrate the two theories by showing that well-defined P-R modes exist where there is BEC. The two are common properties of a Bose condensed liquid and either can be used as a basis of a theory of superfluidity. In addition, the confinement and disorder suppresses the critical temperature for superfluidity, Tc, below that for BEC creating a localized BEC "phase" consisting of islands of BEC and P-R modes. This phase is much like the pseudogap phase in the cuprate superconductors. PMID:25479500

  12. Evidence for a Common Physical Origin of the Landau and BEC Theories of Superfluidity

    SciTech Connect

    Diallo, Souleymane Omar; Azuah, R. T.; Abernathy, D. L.; Taniguchi, Junko; Suzuki, Masaru; Bossy, Jacques; Mulders, N.; Glyde, H. R.

    2014-11-20

    There are two renowned theories of superfluidity in liquid 4He, quite different and each with specific domains of application. In the first, the Landau theory, superflow follows from the existence of a well-defined collective mode supported by dense liquid 4He, the phonon-roton mode. In the second, superflow is a manifestation of Bose-Einstein condensation (BEC) and phase coherence in the liquid. We present combined measurements of superfluidity, BEC and phonon-roton (P-R) modes in liquid 4He confined in the porous medium MCM-41. The results integrate the two theories by showing that well-defined P-R modes exist where there is BEC. The two are common properties of a Bose condensed liquid and either can be used as a basis of a theory of superfluidity. In addition, the confinement and disorder suppresses the critical temperature for superfluidity, Tc, below that for BEC creating a localized BEC phase consisting of islands of BEC and P-R modes. This phase is much like the pseudogap phase in the cuprate superconductors.

  13. Slow dynamics at Re =108 in turbulent Helium flows

    NASA Astrophysics Data System (ADS)

    Burguete, Javier; Roche, Philippe; Rousset, Bernard

    2014-11-01

    The presence of slow dynamics is a recurrent feature of many turbulent flows. This behaviour can be created by instabilities of the mean flow or by other mechanisms. In this work we analyze the behavior of a highly turbulent flow (maximum Reynolds number Re =108 , with a Reynolds based on the Taylor microscale Reλ = 2000). The experimental cell consists on a closed cavity filled with liquid Helium (330 liters) close to the lambda point (between 1.8 and 2.5 K) where two inhomogeneous and strongly turbulent flows collide in a thin region. The cylindrical cavity has a diameter of 78cm and two impellers rotate in opposite directions with rotation frequencies up to 2 Hz. The distance between the propellers is 70 cm. Different experimental runs have been performed, both in the normal and superfluid phases. We have performed velocity measurements using home-made Pitot tubes. Here we would like to present preliminary results on this configuration. The analysis of the data series reveals that below the injection frequencies there are different dynamical regimes with time scales two orders of magnitude below the injection scale. We acknowledge support from the EuHIT network and the SHREK Collaboration.

  14. Maximum Expected Wall Heat Flux and Maximum Pressure After Sudden Loss of Vacuum Insulation on the Stratospheric Observatory for Infrared Astronomy (SOFIA) Liquid Helium (LHe) Dewars

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.

    2014-01-01

    The aircraft-based Stratospheric Observatory for Infrared Astronomy (SOFIA) is a platform for multiple infrared observation experiments. The experiments carry sensors cooled to liquid helium (LHe) temperatures. A question arose regarding the heat input and peak pressure that would result from a sudden loss of the dewar vacuum insulation. Owing to concerns about the adequacy of dewar pressure relief in the event of a sudden loss of the dewar vacuum insulation, the SOFIA Program engaged the NASA Engineering and Safety Center (NESC). This report summarizes and assesses the experiments that have been performed to measure the heat flux into LHe dewars following a sudden vacuum insulation failure, describes the physical limits of heat input to the dewar, and provides an NESC recommendation for the wall heat flux that should be used to assess the sudden loss of vacuum insulation case. This report also assesses the methodology used by the SOFIA Program to predict the maximum pressure that would occur following a loss of vacuum event.

  15. Optical Fiber Distributed Sensing Structural Health Monitoring (SHM) Strain Measurements Taken During Cryotank Y-Joint Test Article Load Cycling at Liquid Helium Temperatures

    NASA Technical Reports Server (NTRS)

    Allison, Sidney G.; Prosser, William H.; Hare, David A.; Moore, Thomas C.; Kenner, Winfred S.

    2007-01-01

    This paper outlines cryogenic Y-joint testing at Langley Research Center (LaRC) to validate the performance of optical fiber Bragg grating strain sensors for measuring strain at liquid helium temperature (-240 C). This testing also verified survivability of fiber sensors after experiencing 10 thermal cool-down, warm-up cycles and 400 limit load cycles. Graphite composite skins bonded to a honeycomb substrate in a sandwich configuration comprised the Y-joint specimens. To enable SHM of composite cryotanks for consideration to future spacecraft, a light-weight, durable monitoring technology is needed. The fiber optic distributed Bragg grating strain sensing system developed at LaRC is a viable substitute for conventional strain gauges which are not practical for SHM. This distributed sensing technology uses an Optical Frequency Domain Reflectometer (OFDR). This measurement approach has the advantage that it can measure hundreds of Bragg grating sensors per fiber and the sensors are all written at one frequency, greatly simplifying fiber manufacturing. Fiber optic strain measurements compared well to conventional strain gauge measurements obtained during these tests. These results demonstrated a high potential for a successful implementation of a SHM system incorporating LaRC's fiber optic sensing system on the composite cryotank and other future cryogenic applications.

  16. Optical fiber distributed sensing structural health monitoring (SHM) strain measurements taken during cryotank Y-joint test article load cycling at liquid helium temperatures

    NASA Astrophysics Data System (ADS)

    Allison, Sidney G.; Prosser, William H.; Hare, David A.; Moore, Thomas C.; Kenner, W. S.

    2007-09-01

    This paper outlines cryogenic Y-joint testing at Langley Research Center (LaRC) to validate the performance of optical fiber Bragg grating strain sensors for measuring strain at liquid helium temperature (-240°C). This testing also verified survivability of fiber sensors after experiencing 10 thermal cool-down, warm-up cycles and 400 limit load cycles. Graphite composite skins bonded to a honeycomb substrate in a sandwich configuration comprised the Y-joint specimens. To enable SHM of composite cryotanks for consideration to future spacecraft, a light-weight, durable monitoring technology is needed. The fiber optic distributed Bragg grating strain sensing system developed at LaRC is a viable substitute for conventional strain gauges which are not practical for SHM. This distributed sensing technology uses an Optical Frequency Domain Reflectometer (OFDR). This measurement approach has the advantage that it can measure hundreds of Bragg grating sensors per fiber and the sensors are all written at one frequency, greatly simplifying fiber manufacturing. Fiber optic strain measurements compared well to conventional strain gauge measurements obtained during these tests. These results demonstrated a high potential for a successful implementation of a SHM system incorporating LaRC's fiber optic sensing system on the composite cryotank and other future cryogenic applications.

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

    SciTech Connect

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

    1990-12-01

    We report on work accomplished in the first 30 months of a research and development program to investigate the feasibility of a new technique to detect solar neutrinos in superfluid helium. Accomplishments include the successful completion of design, construction and operation of the entire cryogenic, mechanical and electronic apparatus. During the last several months we have begun a series of experiments in superfluid helium to test the method. Experimental results include the first observation of the combined physical processes essential to the detection technique: ballistic roton generation by energetic charged particles, quantum evaporation of helium at a free surface and bolometric detection of the evaporated helium by physisorption on a cold silicon wafer. Additional results are also presented.

  18. The Importance of Nonlocal Terms in Superfluid Turbulence

    NASA Astrophysics Data System (ADS)

    Zieve, Rena; Dix, Owen

    2015-03-01

    Simulations of vortex motion in superfluid helium based on the Biot-Savart law plus vortex reconnections can model homogeneous superfluid turbulence. However, the quantitative properties of the turbulent tangle are disturbingly sensitive to details of how the computations are carried out, and in some cases the tangle degenerates unphysically into an arrangement of parallel straight vortices. These problems have been attributed to the reconnection procedure, to the periodic boundary conditions used for most calculations, and to the localized induction approximation (LIA) which often replaces the (non-local) Biot-Savart integral. Previous work using numerical calculation of the complete Biot-Savart integral does not show the same issues as the LIA calculations, but these are time-consuming calculations. We show here that numerical integration over a relatively small region can suffice, as long as the size of the region exceeds the typical intervortex spacing. This result explains why the non-local contribution has a strong effect. It contributes an attraction between nearby vortices that ultimately leads to reconnections, which prevent the vortices from settling into an array of parallel lines.

  19. A Superfluid Film Burner for the nEDM Experiment

    NASA Astrophysics Data System (ADS)

    Maxwell, James; nEDM Collaboration

    2013-10-01

    A planned measurement of the neutron electric dipole moment (nEDM) to 10-28 e .cm using the Golub-Lamoreaux method presents complex cryogenic challenges. One such hurdle is the injection of 3He from a polarized atomic beam source into a liquid 4He bath while maintaining the temperature gradient from the cold bath to the warm beam source and minimizing the vapor above the bath. The feasible temperature range for the experiment falls around 400 mK and is constrained from below by the achievable magnetic field gradients, and above by the spin relaxation time of 3He and rate of ultracold neutron up-scattering. The superfluid behavior of 4He below 2.1 K means superfluid film will tend to climb, or ``creep,'' up the sides of the beam tube to reach the warmer space above, creating vapor, resulting in convection and scattering of incident 3He. To stop the superfluid film creep and contain the vapor, a ``film burner'' is under development by the nEDM collaboration. We will describe the effort toward developing a suitable film burner for nEDM, and show preliminary results of a prototype film burner in operation.

  20. He II Liquid/Vapor Phase Separator for Large Dynamic Range Operation

    NASA Technical Reports Server (NTRS)

    Nakano, A.; Petrac, D.

    1995-01-01

    A phase separator, which separates helium vapor from liquid superfluid helium (He II), is an indispensable device for space cryogenics. The most recent approach to the Space Infrared Telescope Facility (SIRTF) uses a new design concept in which only the detector package is cold at launch, the remainder of the telescope being subsequently cooled to operating temperature on orbit. Therefore, a large dynamic operational range is required of the cryogen system. This is a report of initial laboratory test results with candidate porous plugs as phase separators. Mass flow rates and pressure and temperature differences across a porous plug were measured in this experiment. Relatively large mass flow rates were observed even at small pressure differences. In the high mass flow rate region, a hysteresis was observed with increases and decreases of the pressure difference. A linear theory is proposed and compared with experimental data to explain several phenomena observed in this system.

  1. The development of high cooling power and low ultimate temperature superfluid Stirling refrigerators

    NASA Astrophysics Data System (ADS)

    Patel, Ashok B.

    The superfluid Stirling refrigerator (SSR) is a recuperative Stirling cycle refrigerator which provides cooling to below 2 K by using a liquid 3He-4He mixture as the working fluid. In 1990, Kotsubo and Swift demonstrated the first SSR, and by 1995, Brisson and Swift had developed an experimental prototype capable of reaching a low temperature of 296 mK. The goal of this thesis was to improve these capabilities by developing a better understanding of the SSR and building SSR's with higher cooling powers and lower ultimate temperatures. This thesis contains four main parts. In the first part, a numerical analysis demonstrates that the optimal design and ultimate performance of a recuperative Stirling refrigerator is fundamentally different from that of a standard regenerative Stirling refrigerator due to a mass flow imbalance within the recuperator. The analysis also shows that high efficiency recuperators remain a key to SSR performance. Due to a quantum effect called Kapitza resistance, the only realistic and economical method of creating higher efficiency recuperators for use with an SSR is to construct the heat exchangers from very thin (12 μm - 25 μm thick) plastic films. The second part of this thesis involves the design and construction of these recuperators. This research resulted in Kapton heat exchangers which are leaktight to superfluid helium and capable of surviving repeated thermal cycling. In the third part of this thesis, two different single stage SSR's are operated to test whether the plastic recuperators would actually improve SSR performance. Operating from a high temperature of 1.0 K and with 1.5% and 3.0% 3He-4He mixtures, these SSR's achieved a low temperature of 291 mK and delivered net cooling powers of 3705 μW at 750 mK, 977 μW at 500 mK, and 409 μW at 400 mK. Finally, this thesis describes the operation of three versions of a two stage SSR. Unfortunately, due to experimental difficulties, the merits of a two stage SSR were not

  2. Cryogen free scanning probe microscope: the solution for atomic scale surface science below 10 Kelvin without liquid helium

    NASA Astrophysics Data System (ADS)

    Choi, Byoung; Venegas, Miguel; RHK Team

    We present a cryogen free low temperature scanning probe microscope (LT-SPM) working at 9K on both tip and sample. The performance of the microscope was validated in various conditions such as noisy environment and modulated temperature as well as the long time elapsed measurements. Building on the stability and consistency of the closed cycle refrigerator, time extended measurements are available with this state-of-the-art LT-SPM. Studies can now be performed without interrupting the critical moment of the tip on the surface while refilling the conventional liquid cryogen tank. We will present the time evolution of the dopant induced topographic and spectroscopic properties of some topological insulators such as Bi2Se3 and Bi2Te3. The compact and rigid design of the microscope also allows this instrument to work as a practical variable temperature microscope without the hassle of liquid cryogen consumption. We will present temperature dependent STM/STS results on a TiSe2 surface at the temperature between 10K and 350K. Finally, we will discuss how the cryogen free LT-SPM will make the study of the atomic scale phenomenon at low temperature both economical and easy, opening promising new capabilities to surface scientists and researchers in nanotechnology.

  3. Dark matter superfluidity and galactic dynamics

    NASA Astrophysics Data System (ADS)

    Berezhiani, Lasha; Khoury, Justin

    2016-02-01

    We propose a unified framework that reconciles the stunning success of MOND on galactic scales with the triumph of the ΛCDM model on cosmological scales. This is achieved through the physics of superfluidity. Dark matter consists of self-interacting axion-like particles that thermalize and condense to form a superfluid in galaxies, with ∼mK critical temperature. The superfluid phonons mediate a MOND acceleration on baryonic matter. Our framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): dark matter has a higher temperature in clusters, and hence is in a mixture of superfluid and normal phase. The rich and well-studied physics of superfluidity leads to a number of striking observational signatures.

  4. Thermal Performance of the XRS Helium Insert

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  5. Absence of supersolidity in solid helium in porous Vycor glass.

    PubMed

    Kim, Duk Y; Chan, Moses H W

    2012-10-12

    In 2004, Kim and Chan carried out torsional oscillator measurements of solid helium confined in porous Vycor glass and found an abrupt drop in the resonant period below 200 mK. The period drop was interpreted as probable experimental evidence of nonclassical rotational inertia. This experiment sparked considerable activities in the studies of superfluidity in solid helium. More recent ultrasound and torsional oscillator studies, however, found evidence that shear modulus stiffening is responsible for at least a fraction of the period drop found in bulk solid helium samples. The experimental configuration of Kim and Chan makes it unavoidable to have a small amount of bulk solid inside the torsion cell containing the Vycor disk. We report here the results of a new helium in Vycor experiment with a design that is completely free from any bulk solid shear modulus stiffening effect. We found no measurable period drop that can be attributed to nonclassical rotational inertia. PMID:23102323

  6. Instability on the Free Surface of Superfluid He-II Induced by a Steady Heat Flow in Bulk

    NASA Astrophysics Data System (ADS)

    Remizov, I. A.; Levchenko, A. A.; Mezhov-Deglin, L. P.

    2016-06-01

    We report observations of the onset of irregular motion on a free surface of superfluid He-II induced by a quasi-stationary heat flow in a rectangular container. The container open from the top is mounted inside an optical cell partly filled with superfluid He-II. Three holes in the container walls provide free circulation of the normal and superfluid components inside and outside the container. The results of measurements are discussed in terms of the Korshunov theory (Eurphys Lett 16:673, 1991; JETP Lett 75:423, 2002) of the Kelvin-Helmholtz instability on an initially flat He-II surface induced by a relative motion of superfluid and normal components of the liquid along the surface when the counterflow velocity exceeds the threshold value. The experimental data are qualitatively consistent with the theoretical predictions (Korshunov in JETP Lett 75:423, 2002) taking into account the finite viscosity of He-II.

  7. Breathers on quantized superfluid vortices.

    PubMed

    Salman, Hayder

    2013-10-18

    We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings. PMID:24182275

  8. Breathers on Quantized Superfluid Vortices

    NASA Astrophysics Data System (ADS)

    Salman, Hayder

    2013-10-01

    We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings.

  9. Microscopic theory of sound propagation in the superfluid 3He aerogel system

    NASA Astrophysics Data System (ADS)

    Higashitani, S.; Miura, M.; Yamamoto, M.; Nagai, K.

    2005-04-01

    We present a theory of sound propagation in superfluid He3 confined in aerogel, taking dragged aerogel motion into account. The superfluid dynamics coupled with the aerogel motion is formulated by use of the Keldysh Green’s function for weak-coupling superfluid Fermi liquid. We apply the theory to the hydrodynamic regime and calculate the attenuation of a hydrodynamic longitudinal sound mode, the so-called fast mode. The result is compared to the acoustic experiment reported by the Northwestern University group [R. Nomura, G. Gervais, T. M. Haard, Y. Lee, N. Mulders, and W. P. Halperin, Phys. Rev. Lett. 85, 4325 (2000); G. Gervais, R. Nomura, T. M. Haard, Y. Lee, N. Mulders, and W. P. Halperin, J. Low Temp. Phys. 122, 1 (2001)]. We find reasonable agreement between the theory and the experiment.

  10. Superfluid state of repulsively interacting three-component fermionic atoms in optical lattices

    NASA Astrophysics Data System (ADS)

    Suga, Sei-Ichiro; Inaba, Kensuke

    2013-03-01

    We investigate the superfluid state of repulsively interacting three-component (color) fermionic atoms in optical lattices using Feynman diagrammatic approaches and the dynamical mean field theory. When the anisotropy of the three repulsive interactions is strong, atoms of two of the three colors form Cooper pairs and atoms of the third color remain a Fermi liquid. This superfluid emerges close to half filling at which the Mott insulating state characteristic of the three-component repulsive fermions appears. An effective attractive interaction is induced by density fluctuations of the third-color atoms. The superfluid state is stable against the phase separation that occurs in the strongly repulsive region. We determine the phase diagrams in terms of temperature, filling, and the anisotropy of the repulsive interactions. This work was supported by Grant-in-Aid for Scientific Research (C) (No. 23540467) from the Japan Society for the Promotion of Science.

  11. Dissipative processes in superfluid quark matter

    NASA Astrophysics Data System (ADS)

    Mannarelli, Massimo; Colucci, Giuseppe; Manuel, Cristina

    2010-12-01

    We present some results about dissipative processes in fermionic superfluids that are relevant for compact stars. At sufficiently low temperatures the transport properties of a superfluid are dominated by phonons. We report the values of the bulk viscosity, shear viscosity and thermal conductivity of phonons in quark matter at extremely high density and low temperature. Then, we present a new dissipative mechanism that can operate in compact stars and that is named "rocket term". The effect of this dissipative mechanism on superfluid r-mode oscillations is sketched.

  12. Dissipative processes in superfluid quark matter

    SciTech Connect

    Mannarelli, Massimo; Colucci, Giuseppe; Manuel, Cristina

    2010-12-22

    We present some results about dissipative processes in fermionic superfluids that are relevant for compact stars. At sufficiently low temperatures the transport properties of a superfluid are dominated by phonons. We report the values of the bulk viscosity, shear viscosity and thermal conductivity of phonons in quark matter at extremely high density and low temperature. Then, we present a new dissipative mechanism that can operate in compact stars and that is named 'rocket term'. The effect of this dissipative mechanism on superfluid r-mode oscillations is sketched.

  13. Graphene bilayer structures with superfluid magnetoexcitons

    PubMed Central

    2012-01-01

    In this article, we study superfluid behavior of a gas of spatially indirect magnetoexcitons with reference to a system of two graphene layers embedded in a multilayer dielectric structure. The system is considered as an alternative of a double quantum well in a GaAs heterostructure. We determine a range of parameters (interlayer distance, dielectric constant, magnetic field, and gate voltage) where magnetoexciton superfluidity can be achieved. Temperature of superfluid transition is computed. A reduction of critical parameters caused by impurities is evaluated and critical impurity concentration is determined. PMID:22353230

  14. Test of a cryogenic helium pump

    SciTech Connect

    Lue, J.W.; Miller, J.R.; Walstrom, P.L.; Herz, W.

    1981-01-01

    The design of a cryogenic helium pump for circulating liquid helium in a magnet and the design of a test loop for measuring the pump performance in terms of mass flow vs pump head at various pump speeds are described. A commercial cryogenic helium pump was tested successfully. Despite flaws in the demountable connections, the piston pump itself has performed satisfactorily. A helium pump of this type is suitable for the use of flowing supercritical helium through Internally Cooled Superconductor (ICS) magnets. It has pumped supercritical helium up to 7.5 atm with a pump head up to 2.8 atm. The maximum mass flow rate obtained was about 16 g/s. Performance of the pump was degraded at lower pumping speeds. (LCL)

  15. Test of a cryogenic helium pump

    NASA Astrophysics Data System (ADS)

    Lue, J. W.; Miller, J. R.; Walstrom, P. L.; Herz, W.

    1981-02-01

    The design of a cryogenic helium pump for circulating liquid helium in a magnet and the design of a test loop for measuring the pump performance in terms of mass flow vs pump head at various pump speeds are described. A commercial cryogenic helium pump was tested successfully. Despite flaws in the demountable connections, the piston pump itself has performed satisfactorily. A helium pump of this type is suitable for the use of flowing supercritical helium through internally cooled superconductor magnets. It has pumped supercritical helium up to 7.5 atm with a pump head up to 2.8 atm. The maximum mass flow rate obtained was about 16 g/s. Performance of the pump was degraded at lower pumping speeds.

  16. Attainable superheating of the oxygen-nitrogen-helium solutions

    NASA Astrophysics Data System (ADS)

    Kaverin, A. M.; Andbaeva, V. N.; Baidakov, V. G.

    2015-01-01

    Method of measuring the lifetime of the superheated liquid was used to determine temperatures of the limit superheating of the solution of oxygen-nitrogen-helium. The method of calculating the properties of this solution (temperature of limit superheating, saturated vapor pressure, and density) based on the data on the properties of solutions of oxygen-helium and nitrogen-helium was proposed. The surface tension of the solution of oxygen-nitrogen-helium was determined in a special experiment.

  17. Observation of the Q(3/2) Λ-doublet transitions for X2Π3/2 OD in helium nanodroplets

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Liang, Tao; Douberly, Gary E.

    2014-01-01

    The deuteroxyl radical (OD) has been isolated in superfluid helium nanodroplets and characterised by infrared depletion spectroscopy. Two resolved Q(3/2) lines are observed, with a separation that is 4.88 (10) times larger than in the gas phase. This is similar to that previously reported for He-solvated OH (5.30 (2)), for which it was shown that the splitting could be reproduced by a model that assumes a small parity dependence of the rotor's effective moment of inertia [P.L. Raston, T. Liang, and G.E. Douberly, J. Phys. Chem. A (2013). DOI:10.1021/jp312335q]. With this model, the OD Λ-doublet splitting in liquid He is reproduced with Be and Bf rotational constants that differ by ≈0.24%.

  18. Counterflow-induced decoupling in superfluid turbulence

    NASA Astrophysics Data System (ADS)

    Khomenko, Dmytro; L'vov, Victor S.; Pomyalov, Anna; Procaccia, Itamar

    2016-01-01

    In mechanically driven superfluid turbulence, the mean velocities of the normal- and superfluid components are known to coincide: Un=Us . Numerous laboratory, numerical, and analytical studies showed that under these conditions, the mutual friction between the normal- and superfluid velocity components also couples their fluctuations: un'(r,t) ≈ us'(r,t), almost at all scales. We show that this is not the case in thermally driven superfluid turbulence; here the counterflow velocity Uns≡Un-Us≠0 . We suggest a simple analytic model for the cross-correlation function and its dependence on Uns. We demonstrate that un'(r,t ) and us'(r,t) are decoupled almost in the entire range of separations |r - r'| between the energy-containing scale and intervortex distance.

  19. Pulsar timing noise from superfluid turbulence

    NASA Astrophysics Data System (ADS)

    Melatos, Andrew; Link, Bennett

    2014-01-01

    Shear-driven turbulence in the superfluid interior of a neutron star exerts a fluctuating torque on the rigid crust, causing the rotational phase to walk randomly. The phase fluctuation spectrum is calculated analytically for incompressible Kolmogorov turbulence and is found to be red; the half-power point is set by the observed spin-down rate, the crust-superfluid lag and the dynamical response time of the superfluid. Preliminary limits are placed on the latter quantities using selected time- and frequency-domain data. It is found that measurements of the normalization and slope of the power spectrum are reproduced for reasonable choices of the turbulence parameters. The results point preferentially to the neutron star interior containing a turbulent superfluid rather than a turbulent Navier-Stokes fluid. The implications for gravitational wave detection by pulsar timing arrays are discussed briefly.

  20. Quantum Coherence in a Superfluid Josephson Junction

    SciTech Connect

    Narayana, Supradeep; Sato, Yuki

    2011-02-04

    We report a new kind of experiment in which we take an array of nanoscale apertures that form a superfluid {sup 4}He Josephson junction and apply quantum phase gradients directly along the array. We observe collective coherent behaviors from aperture elements, leading to quantum interference. Connections to superconducting and Bose-Einstein condensate Josephson junctions as well as phase coherence among the superfluid aperture array are discussed.