Stability of supercurrents in cylindrical films of tin

Using current pulses with a rise time of less than 0.5 nsec and a pulse length of 240 nsec, the stability of supercurrents in cylindrical films of tin has been investigated. For current densities J in excess of the instability current density $J_I=J_I\left(0\right)[1-{\left(\frac{T}{T_c}\right)}^4]$, the sample voltage rises with time as $a(J,T)f\left(\frac{t}{t^{{}^{\prime }}}\right)$, where $f\left(\frac{t}{t^{{}^{\prime }}}\right)$ is a universal function of $\frac{t}{t^{{}^{\prime }}}$. The time constants t′ cover a range of 0.5 nsecJI and then join onto the values $a=i{R}_n$, the voltage in the normal state. The time constants t′ depend on current and temperature as $t^{{}^{\prime }}\approx t_0[\frac{J_I}{(J-J_I)}-\frac{ϵJ_I^{{}^2}}{{(J-J_I)}^2}]$, where $J_I\left(0\right)$ has values of the order of 15 × 10⁵ A/cm² and t₀≈14 nsec, while ε∼3×10⁻³.