Robert Vance Duncan

Texas Tech University | TTU · Department of Physics

When transferring small volumes of gas samples between laboratories, cold welded, pinched copper tubes offer an inexpensive and convenient solution. In this paper, we outline the preparation, loading, transfer, and analysis methods used in a multi-campus, collaborative study under the United States Department of Energy. This gas transfer method has...

In this paper we discuss the advantages and challenges of utilizing Fission Fragment Rocket Engines (FFREs) to dramatically reduce transit time in space travel, for example, traveling to Mars. We discuss methods to decrease the size and weight of FFREs. These include utilizing metallic deuterides as moderators, driving the engines with electron bea...

An electron beam may be used to generate bremsstrahlung photons that go on to create photoneutrons within metals. This serves as a low-energy neutron source for irradiation experiments [1-3]. In this article, we present simulation results for optimizing photoneutron yield for a 10-MeV electron beam on tantalum foil and erbium deuteride (ErD$_3$). T...

In this paper we discuss the advantages and challenges of utilizing Fission Fragment Rocket Engines (FFREs) to dramatically reduce transit time in space travel, for example, traveling to Mars. We discuss methods to decrease the size and weight of FFREs. These include utilizing metallic deuterides as moderators, driving the engines with electron bea...

Future advanced nuclear rocket propulsion, and the availability of new nuclear power cycle designs, will benefit substantially from the large current investment in alternative nuclear energy that is underway today. We propose a new nuclear cycle which includes the primary fission of lithium-6, followed by secondary fusion of deuterium and tritium,...

The techniques utilizing the inductor-capacitor (LC) self-oscillators are versatile experimental tool for the investigation of magnetic properties. Consequently, numerous scientific measurements have employed this type of technique. An LC self-oscillator generically offers high sensitivity because of the intrinsic elimination of the large backgroun...

Arthur Molella, on the occasion of the fifth anniversary of the National Academy of Inventors (NAI), authored an excellent historical review of the formation and the early impact of the NAI (1). Now, as we complete the first decade of the NAI, I will emphasize the importance of the intellectual revolution that the NAI has achieved for the bettermen...

We describe the design, operation, and performance of a new instrumental configuration capable of quantitative determinations with sub-picomole accuracy of dilute concentrations of low mass species, such as He4, He3, Ne20, and Ar40, in a balance of stable hydrogen (H2, DH, and D2) gas. This inexpensive system may realize important applications in f...

The Texas Tech University Center for Emerging Energy Sciences Research Group implemented rapid translation and analytics of Chinese COVID-19 medical literature in February 2020, which enabled emerging innovations in patient care. Specifically, techniques to optimize patient care through improved ventilation and oxygenation recognizing newly discove...

This article details the design, modeling, construction, and evaluation of an open system calorimeter that operates in a normal room environment to measure endothermic or exothermic events in a system subjected to a steady heat flux. The calorimeter is unique because it allows the measurement of energy and power from an “open” system, where a heat...

The concept of implementation of environmental health protection and sustainment in aerospace environments by definition implies a One Health systems approach. One Health indicates an inherently complex, contextually interrelated system with consideration of human, animal, plant, systems engineering, and environmental health, their interrelationshi...

We present the principle and implementation of a new type of fast response evaporative calorimeter designed to work at cryogenic temperatures and above-ambient pressures. It is capable of measuring input energy from an electric pulse and the thermal output energy by measuring the evaporation of liquid nitrogen through a mass flow meter. This system...

The three National Academies of the United States, working together, authored a comprehensive report in 1992 titled: Policy Implications of Greenhouse Warming: Mitigation, Adaptation, and the Science Base. The authors discussed various possible methods of geoengineering to mitigate the adverse climate effects of the slow, steady buildup of greenhou...

A flexible multi-tubular cryoprobe, including a housing for receiving an inlet flow of near critical cryogenic fluid from a fluid source and for discharging an outlet flow of the cryogenic fluid. A plurality of fluid transfer tubes are securely attached to the housing. This includes a set of inlet fluid transfer tubes for receiving the inlet flow f...

In the high-precision low-temperature experiments, noise immunity has long been an important issue. We consider the problem of measuring the slowly changing data in the presence of both white noise and sudden, short noise spikes. The Kalman filter is applied to attenuate the white noise and a spike detecting algorithm is applied to remove spikes re...

When a heat flux Q is applied downward through a sample of 4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity-induced gradient in T λ . All the helium in the sample is then at the same reduced temperature and the helium is said to be in the Self-Organized Critical (SOC) state. We h...

If a downward heat flux is imposed on a sample of ^4He near Tλ, the sample can self-organize so that its temperature tracks the variation of Tλ induced by the hydrostatic pressure head. This ``Self-Organized-Critical'' (SOC) state is the only means by which a uniform reduced temperature very close to Tλ can be achieved on Earth in ^4He. We recently...

This review provides an overview of the progress in using the low-gravity environment of space to explore critical phenomena and test modern theoretical predictions. Gravity-induced variations in the hydrostatic pressure and the resulting density gradients adversely affect ground-based measurements near fluid critical points. Performing measurement...

PURPOSE Currently, heat and cold-based ablation technologies lack thorough isotherm characterizations. We compare dynamic isotherms of a new cryotechnology in relation to a clinical cryotherapy unit, including local tissue effects. METHOD AND MATERIALS A clinical cryotherapy unit using rapid expansion of high pressured Argon gas within 2.4 and 1.7...

In 2000 Harter et al. reported the first measurements of the enhancement of the heat capacity DeltaCQ≡C(Q)-C(Q=0) of helium-II transporting a heat flux density Q near Tlambda. Surprisingly, their measured DeltaCQ was ~7-12 times larger than predicted, depending on which theory was assumed. In this report we present a candidate explanation for this...

We describe the first continuous-wave (CW) measurements of the upward-going temperature wave in the self-organized-critical (SOC) state which forms in 4He under conditions of downward heat flow near T λ under gravity. The CW technique permits measurements with extremely low (<1 nK) excitation amplitudes, allows continuous measurement of the wave ve...

When a heat flux Q is applied downward through a sample of liquid 4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity induced gradient in Tlambda. All the helium in the sample is then at the same reduced temperature tSOC = ((T[sub SOC] - T[sub lambda])/T[sub lambda]) and the helium is...

We have previously reported on the temperature and magnetic field dependence of the magnetic susceptibility of thin Pd1−xMnx alloy films. Extensive new measurements on sputtered films show that a commercial quality sputtering process produces a film with the same dependence of Curie temperature on x as previously reported for bulk samples of the s...

In this paper, we describe an adaptive optimal PI controller for high-precision low-temperature experiments. We used a modified LQR algorithm to obtain the optimal parameters for the PI controller. Since the plant is nonlinear, a gain scheduling method is applied to modify the optimal parameters under different operating conditions. The simulation...

Ultrasound imaging is widely used in medicine because of its benign characteristics and real-time capabilities. Physics theory suggests that the application of tomographic techniques may allow ultrasound imaging to reach its full potential as a diagnostic tool allowing it to compete with other tomographic modalities such as x-ray computer tomograph...

We report on a new thermometer design and precision heater controller for use in cryogenic experiments near 2.2 K. The thermometer design reduces the thermal resistance between the thermometer and the liquid 4He sample to the point where the noise is limited by thermally driven electrical current fluctuations in the PdMn. The heater controller uses...

No Heading Advances in low-temperature techniques allow us to measure temperature with a precision approaching one part in 1011. Using an rf-biased Josephson-array voltage source, we can control the power dissipated in electric heaters to the same level. At this level of precision, the algorithm used for thermal control and its sensitivity to the n...

We report on the development of a fully time-dependent computer simulation of the 4He normal fluid/superfluid (He-I/He-II) interface dynamics. Both the diverging thermal conductivity and the rapidly changing heat capacity of 4He near the lamda point present a challenge to traditional numerical methods for integrating the heat diffusion equation. We...

We describe a novel space-based low-temperature radiation detector, the “Particle Heating Detector” (PhD), which was recently selected to be part of the first mission of the Low-Temperature Microgravity Physics Facility, scheduled to fly on the International Space Station in 2008. This massive bolometer will measure total heating induced in an alum...

This is a review of those experiments in the area of Fundamental Physics that are either approved by ESA and NASA, or are currently under development, which are to be performed in the microgravity environment of the International Space Station. These experiments cover the physics of liquid Helium (SUE, BEST, MISTE, DYNAMX, and EXACT), ultrastable a...

We have made heat capacity measurements of superfluid 4He at temperatures very close to the lambda point, T λ, in a constant heat flux, Q, when the helium sample is heated from above. In this configuration the helium enters a self-organized (SOC) heat transport state at a temperature T soc(Q), which for Q≥100 nW/cm2 lies below T λ. At low Q we obse...

We report on new transport phenomena observed within a column of 4He heated from above and close to its transition to superfluidity. In this configuration the helium sample will self-organize to a state where the temperature gradient across the column remains equal to the pressure-induced gradient of T (1.273 µK/cm) even as the heat flux is varied...

New paramagnetic susceptibility thermometers have been developed for use in fundamental physics missions in earth orbit. These devices use a SQUID magnetometer to measure the variation in the dc magnetization of a thermometric element that consists of a dilute concentration of manganese in a palladium matrix. Near 2.2 K these new PdMn thermometer...

The Karmanos Cancer Institute is developing an ultrasound device for measuring and imaging acoustic parameters of human tissue. This paper discusses the experimental results relating to tomographic reconstructions of phantoms and tissue. The specimens were scanned by the prototype scanner at a frequency of 1.5 MHz using 2 microsecond pulses. The re...

We have observed a new temperature-entropy wave that propagates opposite to the direction of a steady heat flux Q when the helium column is heated from above. Counter-intuitively this new mode, which resembles second sound, propagates on the normal fluid side of the transition, but it exists only when the column of helium is heated from above. Such...

We report on new transport phenomena observed within a column of 4He heated from above and close to its transition to superfluidity. In this configuration the helium sample will self-organize to a state where the temperature gradient across the column remains equal to the pressure-induced gradient of T λ (1.273 µK/cm) even as the heat flux is varie...

Paramagnetic susceptibility thermometers used in fundamental physics experiments are capable of measuring temperature changes with a precision of a part in 2 x 10(exp 10). However, heater controllers are only able to control open-loop power dissipation to about a part in 10(exp 5). We used an array of rf-biased Josephson junctions to precisely cont...

The magnetic susceptibility of thin films and microstructures consisting of a Pd1−xMnx alloy have been measured as a function of temperature and magnetic field. Sputtering from a 0.68% manganese target produced films with a concentration of approximately 0.90%, as judged by comparison with results from bulk PdMn sensitivity measurements. The thinne...

CQ will exploit the superfluid transition of pure liquid ⁴He, in a microgravity environment, in order to study a critical point phase transition under non-equilibrium conditions. It will be conducted in conjunction with the DYNAMX experiment (critical dynamics in microgravity) on board the ISS, using the same hardware and electronics, an...

Critical Dynamics in Microgravity (DYNAMX) has been selected to be one of the first two fundamental physics experiments to deploy to the International Space Station (ISS) on board the Low Temperature Microgravity Physics Experiments Facility (LTMPEF) M1 mission in 2005. DYNAMX will make very precise heat flow measurements across a column of liquid...

Heat transport through a column of superfluid 4 He has been observed experimentally to self-organize, resulting in a thermal gradient that exactly matches the gradient in the superfluid transition temperature across the column, leaving the entire sample at a constant distance from the superfluid critical point1. We describe a new experiment that i...

Measurements of the magnetic sensitivity of thin sputtered films of PdMn alloy demonstrate the viability of this material for high resolution thermometry. The thinnest films (thickness 1.0 m) show significant domain scale noise below the Curie Temperature, Tc, while thicker films (thickness 10 m) show reliable non-hysteretic behavior throughout the...

The Critical Dynamics in Microgravity Experiment (DYNAMX) and the Enhanced Heat Capacity of Superfluid Helium in a Heat Flux Experiment (CQ) are preparing for flight as part of the first microgravity fundamental physics mission to the ISS in the year 2005. Both experiments will measure the thermal properties of liquid helium-4 under a heat flux in...

It is expected on very general grounds that superflow will break down along a curve on the superfluid side of the Q (heat flux) - T (temperature) plane, and it has been shown that the heat capacity at constant Q, CQ, should diverge along that same curve, which we refer to as Tc(Q). The fundamental purpose of the CQ experiment is to measure CQ as cl...

Germanium Resistance Thermometers (CRT) are used to measure the temperature in cryogenic systems in the range of a few tenths of a degree kelvin to about 40 kelvin. For the Lambda Point Experiment (LPE) and Confined Helium Experiment (CHeX) missions, which were flown on the Space Shuttle in 1992 and 1997, respectively, the CRT readout was performed...

The Critical Dynamics in Microgravity (DYNAMX) experiment has been selected for the first fundamental physics mission aboard the Low Temperature Microgravity Physics Experiments Facility (LTMPEF) to be deployed to the International Space Station (ISS) in 2005. This paper describes the planned measurements, science objectives, and the engineering of...

A series array of 3,000 Josephson junctions has been biased with millimeter radiation (75 GHz) to produce quantized voltage states. These states are used to precisely control the power dissipation in a cryogenic heater. Once this array of Josephson junctions is connected to the heater with superconducting wire, the 10 ppb uncertainty associated wit...

Measurements of the magnetic sensitivity of thin sputtered films of PdMn alloy suggest that the sputtering technique produces an ordered film with a manganese concentration slightly higher than the nominal value of the sputtering target. Sputtering from a 0.68films with a concentration of approximately 0.90by comparison with results from bulk PdMn...

Measurements of heat transport at the transition from perfect thermal superconductivity to nonlinear heat diffusion in pure 4 He provide a very sensitive probe of matter wave coherence. Superfluid heat transport is proportional to the product of the superfluid density and the superfluid velocity, which are both directly related to the superfluid o...

We report on the design of a new prototype flight instrument that will be used to repeat previous Earth-based measurements of nonlinear heat transport near the superfluid transition in the microgravity laboratory. Since this nonlinear conductivity is associated with dynamic limitations to the divergent correlation length, and since gravitational ac...

Nonlinear heat conduction has recently been measured near the superfluid transition in pure 4He at very low heat flux Q. Since both dynamic effects and gravity limit the divergence of the superfluid correlation length near the transition at low-Q, these measurements must be repeated in the microgravity environment in order to observe the dynamic ef...

When driven away from equilibrium by a heat flux Q, the superfluid transition in ^4He evolves from a simple critical point into a fascinating and complex nonlinear region, where the onset of macroscopic quantum order is masked by Earth's gravity. Prior measurements of heat transport within this nonlinear region on Earth (and scheduled measurements...

The flow of heat in ^4He near T_lambda is expected to change significantly in conditions of free fall. The changes will result from the disappearance of the usual gradient of T_lambda caused by the hydrostatic pressure head in the earth's gravity. We present results from calculations modeling the diffusive heat flow dynamics of the He I in the pres...

The Critical Dynamics in Microgravity Project (DYNAMX), which is in competition for flight aboard the International Space Station in the year 2004, will study heat transport through a column of liquid 4He as the liquid helium transitions from its superfluid to its normal-fluid state. Stray heat will be controlled to within 10 pW, and temperatures w...

Interest in the critical dynamics of superfluid 4 He in microgravity conditions has motivated the development of new high resolution thermometry technology for use in space experiments near 2 K. We have developed a magnetic thermometer using dilute magnetic alloys of Mn or Fe dissolved in a pure Pd matrix, similar to previous thermometers used at u...

Interest in the critical dynamics of superfluid He in microgravity conditions has motivated the development of new high resolution thermometry technology for use in space experiments near 2K. The current material commonly used as the temperature sensing element for high resolution thermometers (HRTs) is copper ammonium bromide (Cu(NH{sub 4}){sub 2}...

A high resolution thermometer (HRT) was developed using a dilute alloy of Mn in Pd as the magnetic sensing element instead of the traditional paramagnetic salt. Use of the alloy material facilitated a significant decrease in the total mass of the device to about 3.5 g. The noise and drift of the device were measured and found to be comparable with...

The DC voltage output from a hysteretic Josephson junction which is locked to an AC frequency source differs from the ideal Josephson relation if the junction drives a current about a closed superconducting circuit. The difference in voltage Delta V from two hysteretic Josephson junctions driven in series opposition is proportional to the differenc...

We have recently observed nonlinear heat transport within 30 nK of the superfluid transition temperature using heat flux, Q, in the range 0.1 < Q < 2 erg/(s cm 2). While Haussmann and Dohm (HD) accurately predict the initial departure of the thermal conductivity, κ, from the linear response region, κ is greater than expected very close to T λ. We a...

The behavior of the superfluid \char21{} normal fluid interface in ${}^{4}\mathrm{He}$ has been studied in the presence of a heat flux, $\stackrel{$\rightarrow${}}{Q}$, in the range $0.1<Q<6\phantom{\rule{0ex}{0ex}}\mathrm{erg}{\mathrm{s}}^{$-${}1}{\mathrm{cm}}^{$-${}2}$. Fourier's Law, $\stackrel{$\rightarrow${}}{Q}\phantom{\rule{0ex}{0ex}}=\phant...

We report measurements of the Seebeck coefficients of boron carbides having compositions B{sub 12+x}C {sub 3-x} , 0.15>x>1.7 , from 6thinsptothinsp900thinspK. These Seebeck coefficients are large, â200 μ V/K at 300thinspK, despite boron carbides having high carrier densities, â10²¹ cm⁻³ . The Seebeck coefficients also have unusual temperature...

Heating due to the high ambient flux of charged particles above the earth's atmosphere is a problem for orbital low-temperature experiments with high energy sensitivity. Calorimetric measurements performed by the Lambda Point Experiment found the charged-particle heating to be complicated, varying with vehicle attitude and orbital position. The ran...

A thermal conductivity cell typically includes a low-conductivity cylindrical sidewall with high conductivity probes protruding through the circumference at various axial positions. The thermal conductivity of the helium in the cell is measured by passing a heat current axially through the helium column and measuring the temperature at each probe....

New thermal conductivity results for ^4He are presented in the temperature range t = 10-6 to t ≈ 10-9, t = |T-T_λ|/T_λ, for heat flux, Q, between 10 and 100nW/cm^2. This study was conducted using a sample cell employing sidewall thermometry with sub-nanokelvin resolution. To lessen the effect of gravity on the measurement, a differential technique...

Thermal conductivity measurements in 4He were performed in an experimental cell which employs a unique side-wall probe geometry. The side-wall probes allowed the boundary effects to be circumvented. The side-wall probes also facilitated a single probe measurement technique that allowed measurements of thermal conductivity to within several nanoKelv...

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 very far away from equilibrium as the transition occurs, Here we propose to measure the thermal gradient across the supertluid (HeII)—normal fluid (HeI i...

Thin-film composite membranes were prepared by coating porous polysulfone membranes with a polyvinyl alcohol layer and further cross-linking its surface. Aldehydes, dialdehydes and malic acids were used as cross-linking agents. The effects of additives to the PVA solution, of solvents used for making PVA solutions, and of alcohols used for the memb...

We will report on the design of an experiment to study the dynamic aspect of thermal conductivity of helium--4 in a heat flux very near the superfluid transition. This apparatus has been used to measure the thermal profile near the normal fluid--superfluid interface with sub-nanokelvin resolution. These measurements are performed by sweeping the in...

We report results of a simple analytical calculation of heat flow in a ^4He thermal conductivity cell. The cell has two isothermal anvils which are coaxial with the gravitational field. A coaxial cylindrical shell, or sidewall, of thermal conductivity 20 mWcm-1K-1, is between the two anvils and is sealed to them. ^4He is confined inside the vessel...

Precision measurements near the superfluid (λ) transition of4He is limited by a gravity induced inhomogeneity inT λ. Critical Dynamics in Microgravity (DYNAMX, a NASA preproject) will study the thermal conductivity in the nonlinear region in Microgravity. Unlike the study of static properties, the thermal conductivity can be derived from the measur...

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 report...

A detailed review of Sandia's work in ultralow power dissipation electronics for space flight applications, including superconductive electronics, new advances in quantum well structures, and ultra-high purity 3-5 materials, and recent advances in micro-electro-optical-mechanical systems (MEMS) is presented. The superconductive electronics and micr...

The Critical Dynamics in Microgravity Experiment, DYNAMX, is under development for space flight at Sandia National Laboratories and the University of New Mexico with Dr. Rob Duncan as the Principal Investigator. This experiment will investigate the effects on the superfluid transition in {sup 4}He of currents generated by heat flow, measuring the t...

The effect of a sidewall thermometry probe on heat transport measurements in liquid 4He very close to the superfluid transition is simulated numerically. The effective thermal position of the probe changes with closeness of approach to the superfluid transition. The radial heat flux induced by the sidewall probe is calculated for specific probe des...

The properties of liquid helium very near the lambda-transition in the presence of a heat current has received recent theoretical and experimental attention. In this regime, gravity induced pressure effects place severe constraints on the types of experiments that can be performed. A new experiment is described which largely overcomes these difficu...

A charged capacitor which is placed with a semiconductor in a closed loop will normally discharge in a characteristic time τ=1/RC. We show, however, that if a semiconductor of high purity is subjected to a rf bias with frequency ω, discharge does not occur if the voltage across the capacitor is proportional to an integer multiple of ħω/e. Thus a rf...

The Josephson relation {ital V}={ital nh}{nu}/2{ital e} has been verified experimentally to 3 parts in 10{sup 19} (A. K. Jain, J. E. Lukens, and J.-S. Tsai, Phys. Rev. Lett. 58, 1165 (1987)). Motivated by this result, we propose a differential-frequency-readout system by two sets of hysteretic Josephson junctions rf biased at millimeter wavelengths...

The dc voltage output from a hysteretic Josephson junction which is locked to an ac frequency source differs from the ideal Josephson relation if the junction drives a current about a closed superconducting circuit. The difference in voltage ΔV from two hysteretic Josephson junctions driven in series opposition is proportional to the difference in...

The superfluid transition in pure {sup 4}He under its saturated vapor pressure provides an ideal fixed-point reference for thermometry near 2 K. In practice, the transition may be located to within a few nanokelvin, and it is virtually immune to drift. Here we first review the properties of {sup 4}He very near the transition which may affect the pe...

The superfluid transition in pure He-4 under its saturated vapor pressure provides an ideal fixed-point reference for thermometry near 2 K. In practice, the transition may be located to within a few nanokelvin, and it is virtually immune to drift. Here we first review the properties of He-4 very near the transition which may affect the performance...

The Josephson series-array voltage standard (JAVS) has dramatically improved the level to which high-accuracy electrical equipment may be monitored and stabilized. For example, a small pressure dependence in the output of some solid-state voltage standards has been measured with the JAVS. The use of two such series-arrays in a superconductive loop...

We report experimental results for the Kapitza resistance {ital R}{sub {ital K}} between gold and superfluid ⁴He, which were obtained by using very-high-resolution thermometry. The data imply that {ital R}{sub {ital K}} is singular at the superfluid transition temperature {ital T}{sub λ}. Comparison with theory suggests that the singularity resu...

A refrigerated dewar has been used successfully with the Josephson array voltage calibration system. It has been used to re-liquify helium with no degradation of the calibration system's performance. The independence of the array voltage from temperature has been confirmed to three parts in 108 per kelvin over the range 1.6 K ≤ T ≤ 4.6 K. No signif...

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A series-array voltage standard containing 2,076 Josephson junctions has been operated in a liquid helium bath maintained within a refrigerated Dewar over the temperature range 1.56K ≤ T ≤ 4.54K. No systematic variation in the array voltage near 1.018V with temperature was detected over this entire range, indicating that any temperature coefficient...

A new generation of digital multimeters was used to compare the ratios of the resistances of wire-wound reference resistors and quantized Hall resistances (QHRs). Specifically, a digital multimeter was used to compare the DC voltage ratio of a QHR sample with that of a reference resistor connected in series with the sample. The accuracies are bette...

We report new high-resolution measurements of the thermal conductivity very near the superfluid-transition temperature T/sub lambda/ on a thicker sample (0.57 cm) than had been used previously (0.22 cm) by Kipa and Chui (LC). Our results deviate less from the conductivity expected for a bulk sample than do the LC data. Our data, the results of LC,...

We report experimental results for the depression of the superfluid transition temperature T/sub lambda/(Q) in /sup 4/He by a heat current Q. The data were obtained by use of thermometry with a resolution of 10 nK, and cover the range 0.4approx. <Qapprox. <10 ..mu..W/cm/sup 2/. They can be represented by 1--T/sub lambda/(Q)/T/sub lambda/(0) = (Q/Q/...

A new type of paramagnetic susceptibility thermometry called toroidal magnetic thermometry (TMT) has been developed. These TMT thermometers have a thermal resolution of five nanoKelvin near the ^4He superfluid transition temperature T_lambda = 2.172K, making TMT roughly a factor of fifty times better in resolution than conventional germanium resist...

We report experimental results for the thermal boundary resistance R/sub K/ between gold and superfluid ⁴He which were obtaiend by the use of thermometry with 3-nK resolution. The data imply that R/sub K/ is singular at the superfluid transition temperature T/sub lambda/. Comparison with theory suggests that the singularity results from a hydrody...

We report experimental results for the thermal boundary resistance RK between gold and superfluid 4He which were obtained by using thermometry with three-nanokelvin resolution. The data imply that RK is singular at the superfluid transition temperature Tλ. For t≡1-T/Tλ\lesssim10-4, RK becomes noticeably dependent on the heat flux Q used to make the...