Particle trajectories in thermal counterflow of superfluid helium in a wide channel of square cross section

2016 ◽  
Vol 28 (2) ◽  
pp. 024102 ◽  
Author(s):  
Marco La Mantia
Keyword(s):  
Cross Section ◽  
Superfluid Helium ◽  
Thermal Counterflow ◽  
Particle Trajectories ◽  
Wide Channel

Absolute optical absorption cross-section measurement of Rb atoms injected into superfluid helium using energetic ion beams

2018 ◽  
Vol 12 (1) ◽  
pp. 016502
Author(s):  
Kei Imamura ◽  
Yukari Matsuo ◽  
Wataru Kobayashi ◽  
Tsuyoshi Egami ◽  
Makoto Sanjo ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Cross Section ◽  
Superfluid Helium ◽  
Absorption Cross Section ◽  
Ion Beams ◽  
Absorption Cross ◽  
Cross Section Measurement ◽  
Section Measurement

Thermal counterflow experiments on superfluid helium at temperatures close toTλ

1985 ◽  
Vol 31 (9) ◽  
pp. 5722-5727 ◽  
Author(s):  
A. G. F. Dorscheidt ◽  
H. van Kempen ◽  
P. Wyder ◽  
T. H. K. Frederking
Keyword(s):  
Superfluid Helium ◽  
Thermal Counterflow

scholarly journals Нейтроноводная система ультрахолодных и холодных нейтронов на реакторе ВВР-М

2019 ◽  
Vol 89 (5) ◽  
pp. 788
Author(s):  
А.П. Серебров ◽  
В.А. Лямкин ◽  
В.М. Пусенков ◽  
М.С. Онегин ◽  
А.К. Фомин ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Flux Density ◽  
Cross Section ◽  
Superfluid Helium ◽  
Electric Dipole ◽  
Source Parameters ◽  
Neutron Guide ◽  
Cold Neutrons ◽  
Extensive Program ◽  
Neutron Guides

AbstractThe results of calculation of fluxes of ultracold (UCNs), very cold, and cold neutrons at the output of neutron guides of the UCN source with superfluid helium at the WWR-M reactor are presented. UCN density ρ_35L = 1.3 × 10^4 n/cm^3 in the trap of the electric dipole moment (EDM) spectrometer was obtained by optimizing source parameters. This UCN density in the EDM spectrometer is two orders of magnitude higher than the UCN density at the output of the available UCN sources. The flux density of cold neutrons with a wavelength of 2–20 Å at the output of a neutron guide with a cross section of 30 × 200 mm^2 should be as high as 1.1 × 10^8 n/(cm^2 s), while the flux density of very cold neutrons (50–100 Å) at the output of the same neutron guide should be 2.3 × 10^5 n/(cm^2 s). An extensive program of fundamental and applied physical research was mapped out for this source.

scholarly journals Three-Dimensionality of Thermal Counterflow in Superfluid Helium Based on PTV Method

2019 ◽  
Vol 2019 (0) ◽  
pp. OS8-08
Author(s):  
Takumi MARUYAMA ◽  
Shinichiro WAKI ◽  
Tatsuya TSUNEYOSHI ◽  
Yoshiyuki TSUJI
Keyword(s):  
Superfluid Helium ◽  
Thermal Counterflow

Vorticity enhancement in thermal counterflow of superfluid helium

2018 ◽  
Vol 97 (6) ◽  
Author(s):  
P. Hrubcová ◽  
P. Švančara ◽  
M. La Mantia
Keyword(s):  
Superfluid Helium ◽  
Thermal Counterflow

The efficiency of an array of tidal turbines partially blocking a wide channel

2012 ◽  
Vol 708 ◽  
pp. 596-606 ◽  
Author(s):  
Takafumi Nishino ◽  
Richard H. J. Willden
Keyword(s):  
Cross Section ◽  
Local Area ◽  
Channel Cross Section ◽  
Channel Height ◽  
Power Extraction ◽  
Wide Channel ◽  
Tidal Turbines ◽  
Optimal Value ◽  
Horizontal Expansion ◽  
Entire Array

AbstractA new theoretical model is proposed to explore the efficiency of a long array of tidal turbines partially blocking a wide channel cross-section. An idea of scale separation is introduced between the flow around each device (or turbine) and that around the entire array to assume that all device-scale flow events, including ‘far-wake’ mixing behind each device, take place much faster than the horizontal expansion of the flow around the entire array. This assumption makes it possible to model the flow as a combination of two quasi-inviscid problems of different scales, in both of which the conservation of mass, momentum and energy is considered. The new model suggests the following: when turbines block only a small portion of the span of a shallow channel cross-section, there is an optimal intra-turbine spacing to maximize the efficiency (limit of power extraction) for a given channel height and width. The efficiency increases as the spacing is reduced to the optimal value due to the effect of local blockage, but then decreases as the spacing is further reduced due to the effect of array-scale choking, i.e. reduced flow through the entire array. Also, when the channel is infinitely wide, the efficiency depends solely on the local area blockage rather than on the combination of the intra-turbine spacing and the channel height. As the local blockage is increased, the efficiency increases from the Lanchester–Betz limit of 0.593 to another limiting value of 0.798, but then decreases as the local blockage is further increased.

scholarly journals Development of a powerful UCN source at PNPI's WWR-M reactor

2019 ◽  
Vol 219 ◽  
pp. 10002 ◽  
Author(s):  
Anatolii Serebrov ◽  
Vitalii Liamkin ◽  
Aleksey Fomin ◽  
Valeriy Pusenkov ◽  
Konstantin Keshishev ◽  
...  
Keyword(s):  
Cross Section ◽  
Superfluid Helium ◽  
Thermal Load ◽  
Heat Load ◽  
Source Parameters ◽  
Neutron Guide ◽  
Neutron Electric Dipole Moment ◽  
Quantum Liquid ◽  
Neutron Lifetime ◽  
Cold Neutrons

The WWR-M reactor at PNPI is planned to be equipped with a high-flux source for ultracold neutrons (UCNs). The method of UCN production is based on neutron conversion in superfluid helium, exploiting the particular qualities of that quantum liquid. As a result of optimizing the source parameters, we expect a temperature of superfluid helium of 1.2 K and a UCN density of 1.3 × 104 cm−3 in a neutron electric dipole moment (EDM) spectrometer. The expected flux densities of cold neutrons (with wavelengths in the range 2–20 Å) and very cold neutrons (50–100 Å) at the output of a neutron guide with a cross section of 30 × 200 mm2 are 9.7 × 107 cm−2s−1 and 8.3 × 105 cm−2s−1, respectively. The capability of maintaining a temperature of 1.37 K at a thermal load of 60 W was shown experimentally, while the theoretical load is expected to be 37 W. Calculations show that it is possible to decrease the helium temperature down to 1.2 K at similar heat load. The project includes the development of experimental stations at UCN beams, such as for a neutron EDM search, measurements of the neutron lifetime, and for a search for neutron-to-mirror-neutron transitions. In addition, three beams of cold and very cold neutrons are foreseen. At present, the vacuum container of the UCN source has been manufactured and the production of the low-temperature deuterium and helium parts of the source has been started.

scholarly journals Energy spectrum of thermal counterflow turbulence in superfluid helium-4

2017 ◽  
Vol 96 (9) ◽  
Author(s):  
J. Gao ◽  
E. Varga ◽  
W. Guo ◽  
W. F. Vinen
Keyword(s):  
Energy Spectrum ◽  
Superfluid Helium ◽  
Thermal Counterflow ◽  
Helium 4
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