Thermal contact between cerium magnesium nitrate and liquid3He at very low temperatures

1973 ◽  
Vol 10 (3-4) ◽  
pp. 379-395 ◽  
Author(s):  
J. H. Bishop ◽  
D. W. Cutter ◽  
A. C. Mota ◽  
J. C. Wheatley
Keyword(s):  
Low Temperatures ◽  
Thermal Contact ◽  
Magnesium Nitrate

Thermal Equilibrium Between LiquidHe3and Powdered Cerium Magnesium Nitrate at Very Low Temperatures

1966 ◽  
Vol 16 (7) ◽  
pp. 273-275 ◽  
Author(s):  
W. R. Abel ◽  
A. C. Anderson ◽  
W. C. Black ◽  
J. C. Wheatley
Keyword(s):  
Low Temperatures ◽  
Thermal Equilibrium ◽  
Magnesium Nitrate

A new method of correlating the magnetic temperature scales of paramagnetic salts below 1° K

1956 ◽  
Vol 233 (1195) ◽  
pp. 536-555 ◽  
Keyword(s):  
Thermal Contact ◽  
Solid Sphere ◽  
Magnesium Nitrate ◽  
Temperature Relation ◽  
Temperature Scales ◽  
Ammonium Alum ◽  
Ferric Ammonium ◽  
Cerium Salt ◽  
Good Agreement ◽  
Crystal Sphere

By making use of the extremely anisotropic susceptibility of cerium magnesium nitrate to provide a magnetic thermometer, the susceptibilities of several paramagnetic salts have been determined at temperatures below 1° K. The measurements have been made on specimens in the form of a spherical shell of the substance to be examined enclosing a single crystal sphere of cerium magnesium nitrate. By measurements on the compound specimen in directions parallel and perpendicular to the magnetic axis of the cerium crystal, the susceptibilities of the two components can be separately determined. Since that of the cerium salt obeys Curie's law accurately, the temperature is readily found, and hence the susceptibility-temperature relation for the material of the shell. The problem of thermal contact between the components has been investigated, and it is shown that reliable results can be obtained at temperatures down to 0.05° K. The demagnetizing effects in a concentric spherical specimen have been calculated, and all the results are expressed in terms of the magnetic temperature defined from the inverse of the susceptibility of a specimen in the form of a solid sphere. Measurements have been made on neodymium magnesium nitrate, three cupric Tutton salts, ferric ammonium alum, and manganous ammonium sulphate. The results obtained with neodymium magnesium nitrate are compared with the behaviour predicted theoretically, and good agreement is found.

A Low Frequency Remote Plasma Rapid Thermal CVD System with Face Down Electrostatic Clamp Wafer Holder

1993 ◽  
Vol 303 ◽  
Author(s):  
Marlio J. C. Bonfim ◽  
Jacobus W. Swart ◽  
Cristian E. M. Velasco ◽  
Juscelino H. Okura ◽  
Patrick B. Verdonck
Keyword(s):  
Low Temperatures ◽  
Thermal Contact ◽  
Low Frequency ◽  
Activation Energies ◽  
Temperature Uniformity ◽  
Remote Plasma ◽  
Thermal Cvd ◽  
Good Thermal Contact ◽  
Small Chamber ◽  
Si Wafer

ABSTRACTA multiprocess CVD system with the following main features is designed and constructed: the wafer holder is made of a Si wafer with diameter larger than the process wafers. This larger holder produces a better temperature uniformity on the process wafer. A good thermal contact between holder and process wafer is obtained by an electrostatic clamp. The holder supports the process wafer facing down. A remote plasma is produced in a small chamber inside the process chamber. The 100 KHz RF frequency keeps the system very simple and cheap while still reasonable ionization is achieved. SiO2 films were deposited using SiH4 and O2 with and without remote plasma of O2. At low temperatures and 1.5 Torr, process activation energies of about 0.9 and 0.3 eV were obtained respectively.

scholarly journals Experiments at very low temperatures obtained by the magnetic method II—New supraconductors

1935 ◽  
Vol 151 (874) ◽  
pp. 610-623 ◽  
Keyword(s):  
Liquid Helium ◽  
Experimental Technique ◽  
Low Temperatures ◽  
Thermal Contact ◽  
Entropy Change ◽  
The Other ◽  
Magnetic Method ◽  
Mechanical Contact ◽  
Ammonium Alum ◽  
Theoretical Considerations

In a previous paper (which we shall refer to as I) we discussed the experimental technique of obtaining very low temperatures by the magnetic method and gave some theoretical considerations connected with it. We showed also that the entropy changes involved in demagnetizing the paramagnetic salts used for this method are of such an order that it should be easily possible to cool appreciable amounts of additional sub­stances together with them. This paper deals with experiments of this kind. The chief point in such experiments is the thermal contact between the cooling salt and the substance to be cooled. The ordinary way of making such a contact would be by means of a gas (which has the advantage that the contact can easily be broken again); but that is, of course, out of the question in this temperature region. A very effective way of making the heat contact would be to use liquid helium, letting the liquid make contact between the salt and the additional substance, and this contact could be broken by moving one or both of the substances with respect to the surface of the liquid. Having done this there would be no contact at all, as the vapour pressures at the temperatures concerned are so small that no heat can be transmitted through the gaseous phase of the helium. The cooling down of the helium would not appreciably reduce the efficiency of the cooling, as can be seen from the following data. The entropy change involved in bringing 1 cu cm of iron ammonium alum into a field of 10,000 gauss at 1° is 5·10 -3 cal/degree. The total entropy of 1 cu cm of liquid helium at 1°, on the other hand, amounts to 1·10 -3 cal/degree. Thus it would easily be possible to use even equal volumes of salt and liquid helium. This way of making heat contact seems very promising; but of course it complicates the apparatus to a certain extent, and so, in the present stage of experimental technique, we made use of a simpler arrangement which had not all the advantages of the other but was sufficient for our present purposes. We used direct mechanical contact.

Thermal Contact at Low Temperatures

Nature ◽  
1958 ◽  
Vol 182 (4650) ◽  
pp. 1661-1663 ◽  
Author(s):  
R. BERMAN ◽  
C. F. MATE
Keyword(s):  
Low Temperatures ◽  
Thermal Contact
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