Relaxation Time of the Cooper-Pair Density in Tin

The relaxation time τR for the density of superconducting electrons to achieve equilibrium with a change in current density has been measured near Tc, using a large, chopped dc and a small continuous rf current. The changeover from ωτR1 to ωτR1 has been observed in the frequency range 30 MHz<~f<~900 MHz. In the temperature range 0.95<~TTc<~0.995, the relaxation time was found to be τR=2.6×10^-10(1-TTc)^-1/2 sec.