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in subjects: "Quantum Fluids"

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Liquid helium dump concept for a large scale superconducting magnetic energy storage plant

Superconducting Magnetic Energy Storage (SMES) is a potentially cost effective technology for electric utility load leveling. Design concepts and cost estimates of SMES plants capable of delivering 5000 MWh daily have been previously identified. An important feature of a large commercial plant is a system that will reliably shut down the magnet by thermally dissipating the stored energy in the event of an imminent or actual loss of superconductivity. To prevent damage to the coil during such a … more

Date: January 1, 1985

Creator: Schoenung, S. M.; Loyd, R. J.; Nakamura, T.; Rogers, J. D. & Purcell, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Radiation-induced electrical breakdown of helium in fusion reactor superconducting magnet systems

A comprehensive theoretical study has been performed on the reduction of the electrical breakdown potential of liquid and gaseous helium under neutron and gamma radiation. Extension of the conventional Townsend breakdown theory indicates that radiation fields at the superconducting magnets of a typical fusion reactor are potentially capable of significantly reducing currently established (i.e., unirradiated) helium breakdown voltages. Emphasis is given to the implications of these results inclu… more

Date: December 2, 1983

Creator: Perkins, L.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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A rapid, semiempirical method of calculating the stability margins of superconductors cooled with subcooled He-II: (Final report)

A rapid, semiempirical method is presented for calculating the stability margins of superconductors cooled with subcooled He-II. Based on a model of Seyfert, the method takes into account both time-dependent Gorter-Mellink heat transport and the effects of interfacial Kapitza resistance. The method has been compared favorably with heat transfer data of Seyfert, stability data of Meuris, and stability data of Pfotenhauer and van Sciver. 4 refs., 7 figs., 1 tab.

Date: January 1, 1986

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Pressurized helium II-cooled magnet test facility

A facility for testing superconducting magnets in a pressurized bath of helium II has been constructed and operated. The cryostat accepts magnets up to 0.32 m diameter and 1.32 m length with current to 3000 A. In initial tests, the volume of helium II surrounding the superconducting magnet was 90 liters. Minimum temperature reached was 1.7 K at which point the pumping system was throttled to maintain steady temperature. Helium II reservoir temperatures were easily controlled as long as the temp… more

Date: June 1, 1980

Creator: Warren, R.P.; Lambertson, G.R.; Gilbert, W.S.; Meuser, R.B.; Caspi, S. & Schafer, R.V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Gorter-Mellink pulsed-source problem in cylindrical and spherical geometry

An exact solution to the Gorter-Mellink pulsed-source problem is known in plane geometry. According to this solution, the central temperature falls as t{sup {minus}3/2}, where t is the elapsed time after an instantaneous, plane pulse. No such exact solutions are known to the pulsed-source problem in cylindrical and spherical geometry. But in cylindrical geometry, it can be shown that if the initial condition is an instantaneous temperature rise {Delta}T inside a cylinder of radius R, the centra… more

Date: January 1, 1991

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Gravitational convection of subcooled He I and the transition into superfluid He II at atmospheric pressure

The propagation velocity of the He II-He I interface at 1 atm was measured in a large experimental cryostat. During cooldown, He II at the lambda temperature propagates up and down in a gravitational field with an interface velocity V/sub b/ which depends on the He I temperature T/sub infinity/. For T/sub infinity/ = 4 K, V/sub b/ = 0.1 mm/sec and for T/sub infinity/ = 2.2 K, V/sub b/ = 2 mm/sec. During warm up, He I propagated with an interface velocity V/sub b/ > 30 mm/sec that was measured a… more

Date: June 1, 1980

Creator: Caspi, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Studies of heat transport to forced-flow He II

Analytical and experimental studies of heat transport to forced-flow He II are reported. The work is pertinent to the transfer of He II in space. An analytical model has been developed that establishes a condition for two-phase flow to occur in the transfer line. This condition sets an allowable limit to the heat leak into the transfer line. Experimental measurements of pressure drop and flow meter performances indicate that turbulent He II can be analyzed in terms of classical pressure drop co… more

Date: January 1, 1985

Creator: Dresner, L.; Kashani, A. & Van Sciver, S.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Similarity solutions of nonlinear partial differential equations invariant to a family of affine groups

Problems of technological interest can very often be described by partial differential equations (PDEs) with one dependent and two independent variables (call them c, z, and t, respectively). Many such PDEs are invariant to one-parameter families of one-parameter affine groups. Similarity solutions are solutions of the PDE that are invariant to one group of the family. The great utility of similarity solutions is that they may be calculated by solving an ODE rather than a PDE and are thus much … more

Date: August 1, 1987

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Calorimetry in superfluid He II to measure losses in superconducting magnets

A method using calorimetry to measure magnet losses in pressurized Helium II is described. The isothermal nature of He II is used in measuring the overall heat capacity of the system and the net refrigeration power. During the measurements, the refrigeration power is held fixed, and the system (400 liters) temperature is near 1.92 K. The calorimetric measurement was calibrated against known power inputs between 1 and 20 W. This technique can even measure heat loads higher than the available ref… more

Date: April 1, 1982

Creator: Caspi, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Application of He-II technology to the production of ultrahigh-field superconducting magnets

Data and operating experience acquired during the last three years on the heat-transfer properties of pressurized superfluid He II indicate that the fluid can be successfully used as a coil coolant for high-field superconducting magnets. Indeed, the fluid seems to offer triple benefits over that of ordinary normal life: (1) coil conductors can be driven to wetted perimeter heat fluxes exceeding 1 W.cm/sup -2/; (2) the reduced low-temperature operation (from 4.2) at 1.8 K enhances the critical c… more

Date: November 1, 1983

Creator: Hoard, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Observation of quantized circulation in rotating superfluid /sup 4/He

The quantized circulation of rotating superfluid helium 4 was measured by monitoring the time rate of precession of the plane of vibration of a vibrating wire lying along the cylindrical axis of the container. (GHT)

Date: April 1, 1979

Creator: Karn, P.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Understanding experimentally the transition to chaos in a convecting dilute solution of /sup 3/He in superfluid /sup 4/He

After a brief review of Benard convection experiments at low temperatures, experiments with dilute solutions of /sup 3/He in superfluid /sup 4/He in small-aspect-ratio cells are described. In both rectangular and cylindrical geometries, two states with distinctively different thermal conductances are observed. The square of the frequency of the oscillation found in the state with higher conductance is observed to vary linearly with epsilon = (..delta..T/..delta..T/sub c/)-1. The transition to c… more

Date: January 1, 1983

Creator: Maeno, Y.; Haucke, H. & Wheatley, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Thermal performance of the MFTF magnets

A yin-yang pair of liquid-helium (LHe) cooled, superconducting magnets were tested last year at the Lawrence Livermore National Laboratory (LLNL) as part of a series of tests with the Mirror Fusion Test Facility (MFTF). These tests were performed to determine the success of engineering design used in major systems of the MFTF and to provide a technical base for rescoping from a single-mirror facility to the large tandem-mirror configuration (MFTF-B) now under construction. The magnets were cool… more

Date: August 3, 1983

Creator: VanSant, J.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Status of the Large Coil Test Facility

The Large Coil Test Facility (LCTF) is serving as the focus for international collaboration in the development of superconducting toroidal field coils. The United States is providing the test facility and three test coils. EURATOM, Japan, and Switzerland are each providing one coil, to be tested in a six-coil compact torus. Construction of the LCTF was completed in November 1983 within the $35.75 million budget established in December 1980. Concurrently with the later stages of construction, th… more

Date: January 1, 1983

Creator: Haubenreich, P.N.; Bohanan, R.E.; May, J.R. & Miller, H.E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Steady-state heat transfer to boiling liquid helium in simulated coil windings

The present data show that the worst case steady-state stability in the GE/LCT magnet windings is at a horizontal conductor orientation. The heat transfer improves with inclination of the conductor from horizontal. Calculations show that for these small regions normal zones will recover by cold-end conduction from the inclined conductor on either end.

Date: January 1, 1981

Creator: Walstrom, P.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Measurements of heat transfer to helium II at atmospheric pressure in a confined geometry

Recently the enhanced heat removal capability of unsaturated superfluid helium II has been exploited in fusion and accelerator dipole magnets. In superfluid the internal convection mechanism dominates the heat removal process and orientation with respect to gravity becomes of secondary importance. Heat transfer, however, can be influenced by the thermodynamic state of the liquid, especially with regard to possible phase transformations. The transformation from non-saturated He II must involve a… more

Date: August 1, 1981

Creator: Warren, R.P. & Caspi, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Transient heat transfer in superfluid helium. Part II

Three classical problems associated with the ordinary diffusion equation concern the temperature in: (1) a half-space with clamped heat flux at the free face, (2) a half-space with clamped temperature at the free face, and (3) an infinite medium with a pulsed plane heat source. These problems are also important for the nonlinear diffusion equation based on the Gorter-Mellink relation, which describes heat transport in superfluid helium. A similarity solution to problem (1), the clamped-flux pro… more

Date: January 1, 1983

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Theory of neutron scattering experiments on momentum distributions in quantum fluids

In this paper, the first perturbative derivation of the final state corrections to the impulse approximation for deep inelastic neutron scattering experiments was presented. The final state broadening is found to depend on g(r) and the He-He phase shifts. The theory satisfies the f-sum rule, the ..omega../sup 2/ sum rule (''kinetic energy'') valid at high Q, and the ..omega../sup 3/ sum rule. In the structure of the theory, the self-energy terms alone would lead to quasi-Lorentzian broadening. … more

Date: January 1, 1987

Creator: Silver, R.N.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Heating-induced flows in cable-in-conduit conductors

Hoenig et al and Miller et al have both reported high stability margins for cable-in-conduit conductors cooled by stationary supercritical helium. Miller et al proposed that strong flows induced in the helium in the early stages of recovery enhanced heat transfer and greatly increased the stability margin over what had been expected for stationary helium. In this memorandum, the flow and pressure transients induced in initially stationary helium by energy transfers typical of those associated w… more

Date: January 1, 1979

Creator: Dresner, L

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Using the surface tension to estimate the condensate density of superfluid /sup 4/He

Distortion of the condensate wavefunction at the free surface of superfluid /sup 4/He contributes to the surface tension in proportion to the condensate fraction n/sub 0/(T). Using this to resolve the present discrepancy between the measured and predicted temperature dependencies of the surface tension gives n/sub 0/(T) in good agreement with results from neutron and x-ray scattering measurements. This picture is also consistent with the measured /sup 3/He-/sup 4/He interfacial tension.

Date: January 1, 1983

Creator: Campbell, L.J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Utilizing subcooled, superfluid He-II in the design of a 12-tesla tandem-mirror experiment

A design study of 12-T yin-yang coils for a conceptual Tandem Mirror Next Step (TMNS) facility has been recently performed by Lawrence Livermore National Laboratory in conjunction with the Convair Division of General Dynamics. The large magnets have major and minor radii of 3.7 and 1.5 m, 0.70 x 3.75 m/sup 2/ cross section, 46.3 MA turns, and an overall current density of 1765 A/cm/sup 2/, obtained by the use of Nb/sub 3/Sn and Nb-Ti superconductors. Each coil is composed of several subcoils se… more

Date: November 11, 1981

Creator: Hoard, R. W.; Cornish, D. N.; Baldi, R. W. & Taylor, W. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Cryogenic analytical tools for LHe distribution system design

The two computer programs presented in this paper are both fundamentally general in that they could be applied to other magnet systems. In addition to MFTF-B analyses, these programs will be used on current and future GDC superconducting magnet projects. Future extended capabilities will include transient heating and flow conditions for THERMOSIPHON and multiple magnet quench features for MAGPRS.

Date: July 29, 1983

Creator: Johnson, R.R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Thermal expulsion of helium from a quenching cable-in-conduit conductor

Three problems are solved in this paper, all by similarity solutions. The first is thermal expulsion from an entire hydraulic circuit initially unpressurized but uniformly heated by the Joule power of the normal conductor. The second problem is expulsion from an unheated but initially pressurized conductor. In both of these problems, the ends of the conductor are imagined to intrude into constant-pressure chambers. The second problem has less practical importance in applied superconductivity th… more

Date: 1981~

Creator: Dresner, L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulation of liquid helium

The author discusses simulation methods for quantum mechanical systems at finite temperatures. Recently it has been shown that static properties of some quantum systems can be obtained by simulation in a straightforward manner using path integrals, albeit with an order of magnitude more computing effort needed than for the corresponding classical systems. Some dynamical information can be gleaned from these simulations as will be discussed below. But this is very limited - there is no quantum v… more

Date: July 1, 1985

Creator: Ceperley, D.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department