β Scribed by B.Z. Kanter
No coin nor oath required. For personal study only.
cm s "2 , o is surface tension between liquid and its vapour in dyne cm "1 , and Pv, Pl are vapour and liquid densities in g cm "3 . Using data for liquid helium at 4.2 K, this equation gives 0.575 < qmax < 0.760 W cm "2 . This is comparable with the results shown in Fig. for the vertical heated surface. Otherwise there is no orientation dependence in the Kutateladze prediction.
The electrical properties of OFHC copper at the liquid helium temperature are comparable with those of AI 59. From the point of view of stability of superconductors it is therefore much more attractive to use super-pure aluminium A1 69, 99.9999% purity, the properties of which have been measured by Stevenson. 12 The specific resistance of A1 69 is in the low field range at 4.2 K, as low as l0 "9 ~cm compared to 10 .8 ~2cm for OFHC copper. The magnetoresistance of A1 69 is relatively low and nearly constant for magnetic fields from 3 T up. The ratio R273/R4. 2 for OFHC copper is about 150 at the best but even more than 10 000 for A1 69. It seems that the use of A1 69 as a stabilizer for high-field superconductors has many advantages. The measurements of heat transfer for A1 69 will therefore continue and the results of these investigations will be reported at some later date.
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