COMPARISON OF THE CALCULATED AND MEASURED STABILITY OF A NBTI CABLE-IN-CONDUIT CONDUCTOR

Calculated curves of cable-in-conduit conductor (CICC) energy stabilit y margins vs. current are compared to experimental curves obtained at Oak Ridge National Laboratory for NbTi single tripler conductors, The conductors ranged in length from 1.8 m to 4.8 m, and had no imposed he lium now, The initiating heat pulse was applied for 16.7 ms over the e ntire conductor length. The calculated stability curves display the la rge decrease in energy margin from the low current and high energy mar gin ''well-cooled'' stability region, to the high current and low ener gy margin ''ill-cooled'' region that was determined experimentally. Th e calculated ''limiting current'' of 250 A (boundary between the ill-c ooled and well-cooled regions) also agrees with experiment, The multi- valued stability margins measured for lengths of 3.1 and 3.8 m could n ot be obtained by the computer model. Excluding the multiple stabiliti es, the calculated margins are generally 30% lower than the experiment al values. The decrease in energy margin in the ill-cooled region was found to be due to the low critical to operating temperature differenc e (2.2 K at 250 A). This prevents an initiating pulse in the ill-coole d region from being able to generate significant Joule heating without quenching, limiting the energy margin.