The dependence of the value of the heat conductivity anomaly of aluminium on heat flux density in the liquid helium temperature range

1971 ◽  
Vol 5 (3) ◽  
pp. 785-791 ◽  
Author(s):  
J. Rafałowicz ◽  
K. Balcerek ◽  
B. Sujak ◽  
E. Pega ◽  
L. Lipiński
Keyword(s):  
Heat Flux ◽  
Liquid Helium ◽  
Flux Density ◽  
Heat Conductivity ◽  
Heat Flux Density ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Conductivity Anomaly ◽  
Temperature Range

Experimental Investigation of Radiative Transfer Between Metallic Surfaces at Cryogenic Temperatures

1970 ◽  
Vol 92 (3) ◽  
pp. 412-416 ◽  
Author(s):  
G. A. Domoto ◽  
R. F. Boehm ◽  
C. L. Tien
Keyword(s):  
Radiative Transfer ◽  
Liquid Helium ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Metallic Surfaces ◽  
Emitter Temperature ◽  
Temperature Range ◽  
Order Of Magnitude ◽  
Temperature Levels ◽  
Lower Temperature

Experimental measurements of the radiative heat flux between two parallel copper disks in the liquid-helium temperature range are presented. The temperature levels investigated were primarily for the higher temperature disk (emitter) at 10.0 deg K and 15.1 deg K and the lower temperature disk (receiver) at approximately 4.5 deg K. For the 15.1 deg K emitter temperature, the spacing was varied from 0.201 cm to 0.001 cm. For the 10 deg K emitter case, the spacing was varied from 0.044 cm to 0.005 cm. Experimental data at small spacings show a definite spacing dependence of radiative transfer which agree qualitatively with the predicted result. Based on the measurements at large spacings, an estimate of the total hemispherical emissivity for the copper surfaces in the liquid-helium temperature range indicates a value of 0.015, which is approximately one order of magnitude higher than predicted. The possible causes for the discrepancies are discussed.

Temperature-dependent phosphorescence spectra of Pd- and Pt-porphins and their applications

2008 ◽  
Vol 12 (11) ◽  
pp. 1201-1210 ◽  
Author(s):  
Mikalai M. Kruk ◽  
Aleksander S. Starukhin ◽  
Rafal Czerwieniec
Keyword(s):  
Liquid Helium ◽  
Metal Ion ◽  
Phosphorescence Spectrum ◽  
Liquid Helium Temperature ◽  
Triplet States ◽  
Helium Temperature ◽  
Temperature Range ◽  
The Matrix ◽  
The Given ◽  
Phosphorescence Spectra

In this paper the temperature dependence of radiative deactivation of Pd - and Pt -porphin triplet states in Shpol'skii matrices has been studied in the temperature range of 4.2-210 K. Dramatic changes in the phosphorescence spectra, with increasing temperature, were observed. It has been proposed that this is due to the inclusion of thermally activated states of the studied molecules in the processes of radiative deactivation of triplet states. For Pd -porphin the T 1 → S 0 emission is merely observed at liquid helium temperature. An increase in temperature leads to the activation of several radiative T i → S 0 transitions, so additional bands appear in the phosphorescence spectrum. In the case of Pt -porphin, temperature activation takes place as early as at liquid helium temperature. The degeneracy lifting of lowest T 1,2 states due to crystal field splitting was observed for both Pd - and Pt -porphins. The splitting value δ = ΔE( T 2 − T 1) has been measured in different matrices and the dependencies on both the metal ion in the given matrix and the matrix type for the given metal ion, have been revealed. The possibility of designing the luminescent molecular thermometers for cryogenic temperatures based on the high temperature sensitivity of the Pd - and Pt -porphin phosphorescence in n-alkane matrices, has been discussed. The workability of the dependence of Pd - and Pt -porphin phosphorescent properties on temperature in the design of the molecular thermometer family for the temperature range from a few K up to temperatures close to the melting point of n-alkane matrix (150-200 K) is demonstrated.

scholarly journals Anomalous a.c. resistivity effect in Nb and Sn at high static fields in the liquid helium temperature range

1971 ◽  
Vol 34 (6) ◽  
pp. 321-323 ◽  
Author(s):  
L.J.M. van de Klundert ◽  
A. van Ardenne ◽  
L.C. van der Marel
Keyword(s):  
Liquid Helium ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Temperature Range

Water accumulation as a function of temperature on specimens in an electron microscope cold stage

1986 ◽  
Vol 44 ◽  
pp. 114-115 ◽  
Author(s):  
M.K. Lamvik ◽  
D.A. Kopf ◽  
S.D. Davilla ◽  
J.D. Robertson
Keyword(s):  
Electron Microscope ◽  
Mass Loss ◽  
Liquid Helium ◽  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Liquid Helium Temperature ◽  
Helium Temperature ◽  
Cold Stage ◽  
Water Accumulation ◽  
Better Than

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

THERMAL BEHAVIOR AND IGNITION OF HIGH-ENERGY MATERIALS CONTAINING B, ALB2, AND TIB2

2020 ◽  
Author(s):  
A. G. Korotkikh ◽  
◽  
V. A. Arkhipov ◽  
I. V. Sorokin ◽  
E. A. Selikhova ◽  
...  
Keyword(s):  
Heat Flux ◽  
Thermal Behavior ◽  
Flux Density ◽  
Ignition Delay ◽  
Delay Time ◽  
Heat Flux Density ◽  
Ignition Delay Time ◽  
High Energy ◽  
Energy Materials ◽  
High Energy Materials

The paper presents the results of ignition and thermal behavior for samples of high-energy materials (HEM) based on ammonium perchlorate (AP) and ammonium nitrate (AN), active binder and powders of Al, B, AlB2, and TiB2. A CO2 laser with a heat flux density range of 90-200 W/cm2 was used for studies of ignition. The activation energy and characteristics of ignition for the HEM samples were determined. Also, the ignition delay time and the surface temperature of the reaction layer during the heating and ignition for the HEM samples were determined. It was found that the complete replacement of micron-sized aluminum powder by amorphous boron in a HEM sample leads to a considerable decrease in the ignition delay time by a factor of 2.2-2.8 at the same heat flux density due to high chemical activity and the difference in the oxidation mechanisms of boron particles. The use of aluminum diboride in a HEM sample allows one to reduce the ignition delay time of a HEM sample by a factor of 1.7-2.2. The quasi-stationary ignition temperature is the same for the AlB2-based and AlB12-based HEM samples.

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