The journey of hydrogen to quantized vortex cores

Bewley, Gregory P.; Vollmer, Jörg

doi:10.1088/0031-8949/2013/t155/014055

Cited by 3 publications

(1 citation statement)

References 40 publications

(49 reference statements)

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“…17 For a 100 nm parti- cle at 1.85 K, the binding energy is estimated to be about 5 × 10 −20 J, which is 1.5 × 10 3 times k b T, where k b is Boltzmann's constant. Since the binding energy is many times k b T, we expect particles to remain trapped and not removed due to purely thermal motions.…”

Section: B Comparison To Frozen Particlesmentioning

confidence: 99%

Nanoparticle dispersion in superfluid helium

Meichle

Lathrop

2014

Review of Scientific Instruments

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Cryogenic fluid flows including liquid nitrogen and superfluid helium are a rich environment for novel scientific discovery. Flows can be measured optically and dynamically when faithful tracer particles are dispersed in the liquid. We present a reliable technique for dispersing commercially available fluorescent nanoparticles into cryogenic fluids using ultrasound. Five types of fluorescent nanoparticles ranging in size from 5 nm to 1 μm were imaged in liquid nitrogen and superfluid helium, and were tracked at frame rates up to 100 Hz.

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Section: B Comparison To Frozen Particlesmentioning

confidence: 99%

Nanoparticle dispersion in superfluid helium

Meichle

Lathrop

2014

Review of Scientific Instruments

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Visualization of He II forced flow around a cylinder

Chagovets

Sciver

2015

Physics of Fluids

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We report an experimental investigation of He II forced flow over a cylindrical obstacle by a flow visualization technique that uses micron scale solid hydrogen particles. It was found in the range of Reynolds numbers studied, 1500 < Red < 11 500, that the flow pattern has a tendency to form a wake with a dynamic separation point similar to that in classical fluids. Furthermore, we did not confirm the existence of large-scale turbulent structures both upstream and downstream of the cylinder as have been observed in He II thermal counterflow across the cylinder at the same range of Reynolds numbers.

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

Fonda

Sreenivasan

Lathrop

2016

Review of Scientific Instruments

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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.

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The journey of hydrogen to quantized vortex cores

Cited by 3 publications

References 40 publications

Nanoparticle dispersion in superfluid helium

Nanoparticle dispersion in superfluid helium

Visualization of He II forced flow around a cylinder

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

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