Search results for "liquid helium"

showing 4 items of 54 documents

Second sound, superfluid turbulence, and intermittent effects in liquid helium II

2002

SuperfluidityQuantum fluidPhysicsHelium-4Condensed matter physicsLiquid heliumlawTurbulenceSecond soundMechanicsIsotopes of heliumVortexlaw.inventionPhysical Review B
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Refrigeration of an array of cylindrical nanosystems by superfluid helium counterflow

2017

Abstract Motivated by the challenge of computer refrigeration, we study the limits set by the transition to quantum turbulence on the cooling of an array of heat-producing cylindrical nanosystems by means of superfluid-helium counterflow. The effective thermal conductivity in laminar counterflow superfluid helium is obtained in channels with rectangular cross section, through arrays of mutually parallel cylinders and in the combined situation of arrays of orthogonal cylinders inside the rectangular channel. The maximum cooling capacity is analyzed on the condition that turbulence is avoided and that the highest temperature does not exceed the lambda temperature.

Thermal conductivity Liquid helium Quantum turbulence Micropores Quantized vortices Computer refrigerationQuantum turbulenceCooling capacity01 natural sciences010305 fluids & plasmaslaw.inventionPhysics::Fluid DynamicsThermal conductivitylaw0103 physical sciencesthermal conductivity010306 general physicsSettore MAT/07 - Fisica Matematicathermal conductivity; liquid helium; quantum turbulence; micropores; quantized vortices; computer refrigerationquantized vorticesCondensed Matter::Quantum GasesFluid Flow and Transfer ProcessesPhysicsCondensed matter physicsliquid heliumTurbulenceLiquid heliumMechanical Engineeringcomputer refrigerationRefrigerationquantum turbulenceLaminar flowMechanicsCondensed Matter PhysicsmicroporesSuperfluid helium-4
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Chapter 2 Single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures

2004

Publisher Summary This chapter discusses the single molecule spectroscopy of multichromophoric dendrimers at room and liquid helium temperatures. Single molecule spectroscopy has become an important tool for the optical study of the electronic interactions of proximate chromophores as the electronic interactions can be studied without averaging over the properties of an intrinsically heterogeneous ensemble. Single perylenemonoimide (PMI) chromophores are selectively addressed in the frequency domain within spatially isolated multichromophoric dendrimers, which are dispersed in a polymer film. Although the chromophores are interacting, they still can be addressed separately. This feature in …

chemistry.chemical_classificationLiquid heliumNanotechnologyPolymerChromophoreSingle Molecule Spectroscopylaw.inventionchemistrylawChemical physicsDendrimerMoleculeSpectral resolutionSpectroscopy
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Transport and extraction of radioactive ions stopped in superfluid helium

2003

A new approach to convert a high energy beam to a low energy one, which is essential for the next generation radioactive ion beam facilities, has been proposed and tested at Jyvaskyla, Finland. An open Ra-223 alpha-decay-recoil source has been used to produce radioactive ions in superfluid helium. The alpha spectra demonstrate that the recoiling Rn-219 ions have been extracted out of liquid helium. This first observation of the extraction of heavy positive ions across the superfluid helium surface was possible thanks to the high sensitivity of radioactivity detection. An efficiency of 36% was obtained for the ion extraction out of liquid helium. (C) 2003 Elsevier Science B.V. All rights res…

radioactive ion beamNuclear and High Energy PhysicssnowballIon beamChemistryLiquid heliumExtraction (chemistry)superfluid heliumIGISOL TECHNIQUENUCLEAR-SPIN POLARIZATIONSpectral linelaw.inventionIonHelium-4lawPhysics::Accelerator PhysicsPhysics::Atomic PhysicsAtomic physicsNuclear ExperimentInstrumentationBeam (structure)Superfluid helium-4
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