Experimental data are presented for the thermal propagation of a normal-superconducting boundary along wires of Nb-25%Zr, Nb-37%Zr, and Nb-51%Zr. The thermal propagation velocity was measured as a function of current at 4.2°K in constant longitudinal and transverse magnetic fields up to the upper critical field Hc2 as well as in a zero magnetic field for temperatures between 2.5° and 11°K. Previous models which describe thermal propagation phenomena neglected the temperature dependences of the specific heat, thermal conductivity, and electrical resistivity. A more exact model is proposed here which takes into account the temperature dependences of these quantities, and all the present experimental data are in good agreement with this model. From a measurement at 4.2°K of the dependence of the thermal velocity on magnetic field, the high-field transition temperatures as a function of magnetic field are calculated for temperatures above 4.2°K. In conjunction with the theory, the linear dependence of the thermal velocity on current implies a weak current dependence for both the transition temperature and superconducting-state specific heat in Nb-Zr alloys up to 3×105 A/cm2. A method is discussed for using thermal propagation techniques to determine the superconducting-state specific heat in the presence of known transport currents and magnetic fields.
The thermal relaxation absorption in the deuterated methanes has been obtained by the tube method for frequencies between 20 and 640 kc/sec·atm. The relaxation time, transition probability, and collision efficiency were determined for each gas. The collision efficiency as a function of molecular weight has been found to follow a simple relation of the form: P,oo::[MJ+.
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