Theoretical Methods for Creep and Stress Relaxation Studies of SSC Coil

Abstract

Extrapolation of laboratory measurements of SSC coil properties to the actual construction of SSC magnets requires mathematical models of the experimental data. A variety of models were used to approximate the data collected from creep and stress relaxation experiments performed on Kapton film and SSC coil samples. The coefficients for these mathematical models were found by performing a least-squares fit via the program MINUIT.

Once the semiempirical expressions for the creep data were found, they were converted to expressions for stress relaxation using an approximation of the Laplace integral relating the two processes. The data sets from creep experiments were also converted directly to stress relaxation data by numeric integration. Both of these methods allow comparison of data from two different methods of measuring viscoelastic properties.

Three compariion papers presented at this conference will present:

• 1) Stress relaxation in sse 50mm dipole coil.

• 2) Measurement of the elastic modulus of Kapton perpendicular to the plane of the filrn at room and cryogenic temperatures.

• 3) Temperature dependence of the viscoelastic properties of sse coil insulation (Kapton).