A5021989210- Quantum, superfluid, helium dynamics
- Physics of Superconductivity and Magnetism
- Atomic and Subatomic Physics Research
- Spacecraft and Cryogenic Technologies
- Planetary Science and Exploration
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Thermodynamics and Statistical Mechanics
- Superconducting Materials and Applications
- High-pressure geophysics and materials
- Geophysics and Sensor Technology
- Seismic Waves and Analysis
- Quantum and electron transport phenomena
- Advanced Thermodynamic Systems and Engines
- Astro and Planetary Science
- Theoretical and Computational Physics
- Magnetic properties of thin films
- Superconducting and THz Device Technology
- Spacecraft Design and Technology
- Earthquake Detection and Analysis
- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Scientific Research and Discoveries
- Seismology and Earthquake Studies
- Calibration and Measurement Techniques
- Spectroscopy and Quantum Chemical Studies
Jet Propulsion Laboratory
2006-2023
California Institute of Technology
1999-2013
National Aeronautics and Space Administration
2005
Stanford University
1988-2003
Georgia Institute of Technology
2001
Georgia Tech Research Institute
2001
University of Hong Kong
1998
National Tsing Hua University
1993-1994
Rutgers, The State University of New Jersey
1980-1982
We report new high-resolution measurements of the heat capacity liquid helium to within 2 nK from lambda transition, performed with a large sample in earth orbit. The optimum value for critical exponent characterizing divergence below transition was found be $\ensuremath{-}0.01285$, giving improved support renormalization-group theory phase transitions. Some information on temperature dependence thermal conductivity just above also obtained.
We report the details and revised analysis of an experiment to measure specific heat helium with subnanokelvin temperature resolution near lambda point. The measurements were made at vapor pressure spanning region from 22 mK below superfluid transition 4 uK above. was performed in earth orbit reduce rounding caused by gravitationally induced gradients on earth. Specific deep asymptotic within 2 nK transition. No evidence found this resolution. optimum value critical exponent describing...
The electrical resistance has been measured on granular aluminum specimens with room-temperature resistivities between 1.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}3}$ and 1.3 ${10}^{\ensuremath{-}1}$ \ensuremath{\Omega} cm, from 0.3 K to room temperature, in magnetic fields up 9 T. results show the importance of electron correlation effects both sides metal-insulator transition. Mott hopping law is not observed any specimen over whole temperature range. suggest possibility...
We report the first quantitative measurements of spontaneous temperature fluctuations in a physical system well modeled by canonical ensemble. Using superconducting magnetometers and carefully controlled thermal environment, we have measured noise spectra paramagnetic salt thermometers that were coupled to reservoirs at 2 K. The found be very good agreement with predictions fluctuation-dissipation theorem. Our observations are variance some interpretations
New measurements of the heat capacity a sample helium 3 mm high are reported which extend to within 5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ deg lambda transition at vapor pressure. From an analysis results allowing for effect gravity, values -0.0127\ifmmode\pm\else\textpm\fi{} 0.0026 ($2\ensuremath{\sigma}$) exponent $\ensuremath{\alpha} (={\ensuremath{\alpha}}^{\ensuremath{'}})$ and 1.058\ifmmode\pm\else\textpm\fi{}0.004 leading singularity ratio...
Measurements of the magnetoresistance are reported for a series granular aluminum specimens on metal side metal-insulator transition. A clear separation can be made between effects localization and those electron-electron interactions. Sufficiently far dominate. At high fields, interactions account observed dependences resistivity temperature, both which absent in theory.
We report measurements of the specific heat liquid helium confined to 57-&mgr;m planar gaps extending within a few nanokelvin bulk lambda transition. The data are in fair agreement with Monte Carlo estimates for finite-size effects and renormalization-group-theory predictions above Far from transition, we find surface exponents, alpha(s) = 0.64+/-0.05 below, 0.65+/-0.2 above, which compare well prediction 0.658. Comparison other recent on small length scales shows some areas agreement.
Measurements of Cosmic Microwave Background (CMB) anisotropy have served as the best experimental probe early universe to date. The inflationary paradigm, inspired in part by extreme isotropy CMB, is now a cornerstone modern cosmology. Inflation has passed series rigorous tests, but we still do not understand physical mechanism or energy scale behind inflation. A general prediction inflation and one that can provide certain insights into physics background primordial gravitational waves....
The temperature dependence of the electrical resistivity granular aluminum films changes from one regime to another as their superconducting transition temperatures drop towards absolute zero. In nonsuperconducting specimens we observe exponential behavior associated with strong localization. other show a weaker, logarithmic dependence.
The interaction of spins in a spin-polarized test mass and those paramagentic salt, separated by \ensuremath{\mu}-metal shield double-layer superconducting shield, was investigated. Our results set limit on electron spin interactions moments which are not electromagnetic origin. In terms standard dipole-dipole form, the is (2.7\ifmmode\pm\else\textpm\fi{}2.4)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}14}$ strength between magnetic electrons. Compared to previous results,...
Direct imaging of an Earth-like exoplanet requires starlight suppression with a contrast ratio on the order 1 ♦ 10<sup>-10</sup> at small angular separations 100 milliarcseconds or less in visible light more than 50 nm bandwidth. To our knowledge, technology needed to achieve and stability has not been demonstrated as January 2019. The science requirements for near future NASA missions such James Webb Space Telescope's (JWST) Near Infrared Camera (NIRCam) coronagraph Wide Field...
Measurements have been made of the critical magnetic field superconducting granular aluminum ($d\ensuremath{\sim}30$ \AA{}) down to temperatures well below ${T}_{c}$ (${t}^{2}<0.1$). The results show that it is possible coupling between grains weak enough and temperature low so isolated grain while at same time large fluctuations expected in this size are suppressed. for ${T}_{c}$, together with those from other sources, indicate maximum a function only.
We report measurements of the thermal conductivity helium in region from 6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}8}$ to 6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ K above lambda point at vapor pressure. Primarily because uncertainties Kapitza boundary resistance, reliable results were obtained only 6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ transition. Within...
Superfluid hydrodynamics for second sound, expanded to first order in \ensuremath{\nabla}${\mathrm{\ensuremath{\rho}}}_{\mathit{s}}$ and including second-sound damping finite-amplitude effects, are cast into a boundary-value-problem format, suitable calculating the resonant frequency cavity operating near \ensuremath{\lambda} point. This model is applied data of Marek, Lipa, Philips, which showed deviations from simpler region close transition. We find that our by itself cannot explain...
The Experimental Probe of Inflationary Cosmology - Intermediate Mission (EPIC-IM) is a concept for the NASA Einstein Inflation satellite. EPIC-IM designed to characterize polarization properties Cosmic Microwave Background search B-mode signal characteristic gravitational waves generated during epoch in early universe. employs large focal plane with 11,000 detectors operating 9 wavelength bands provide 30 times higher sensitivity than currently Planck optical design based on wide-field 1.4 m...
We present the first experimental evidence that heat capacity of superfluid 4He, at temperatures very close to lambda point T(lambda), is enhanced by a constant flux Q. The Q, C(Q), predicted diverge temperature T(c)(Q)<T(lambda) which superflow becomes unstable. In agreement with previous measurements, we find dissipation enters our cell temperature, T(DAS)(Q), below theoretical value, T(c)(Q). argue T(DAS)(Q) can be accounted for instability wall, and therefore distinct from excess measure...
We report the preliminary results of high resolution measurements thermal conductivity 4 He in a cell with nominal 1mm gap, and compare them previous obtained 2mm gap. The temperature dependence was found to be similar for both cells, indicating that size boundary effects are well controlled. also detailed behavior Kapitza resistance just below T λ .
Broadband seismometers and gravitational wave detectors make use of mechanical resonators with a high quality factor to reduce Brownian noise. At low frequency, noise is ultimately dominated by internal friction in the suspension, which has 1/f compared white arising from viscous dissipation. Internal typically modeled as frequency-dependent loss can be challenging measure reliably through experiment. In this work, we present physics experimental implementation electrostatic frequency...
We present a formal thermodynamic treatment of superfluid flow in Josephson junction. show that the current i(s) and phase difference phi are conjugate variables. derive quantitative expressions for rms fluctuations phi. Also, we discuss stability thermal activation to phase-slip region. apply developed formalism why an array apertures 4He can exhibit effect near lambda transition despite strong fluctuations.