Quenches of formvar - coated NbTi/Cu caused by step input in power

We have investigated the stability of the composite Nb48Ti/Cu coated with a formvar layer (30 μm thick). Starting from thermal equilibrium in the superfluid liquid He II range below the lambda temperature (T = T
λ
), the composite temperature is found to rise first monotonically with time t, upon onset of energy dissipation. However, restricted stability is visible as a relative temperature maximum (T
max
) of the composite at the time t
max
, followed by a relative minimum in T at t
min
. These coated composite phenomena are similar to stability conditions of bare composites in the same "conductor-in-box " geometry employed. However at a specified power the times t
max
and t
min
are shifted in comparison to the bare composite. Diagnosis is based on power-time functions whose tangents are characterized by power law exponents (m) . The m-values found are re - presentative of strong, localized solid - coolant interaction, of a caloric condition, or of locally turbulent fluid motion. In the range covered by the present transients, stability is available by creation of entropy - rich buffer domains of fluid, below the superconducting transition temperature, between He II and the heated composite. The latter is quench - protected in an intermediate power range.