Minimum quench power dissipation and current non-uniformity in ITER type NbTi cable-in-conduit conductor samples under DC conditions

摘要

The level of current non-uniformity in NbTi CICCs sections near the joints incombination with the magnet field profile needs attention in view of properjoint design. The strand Joule power and current distribution at quench underDC conditions of two samples of ITER Poloidal Field Coil conductors, as testedin the SULTAN facility and of the so called PFCI Model Coil Insert, have beenanalyzed with the numerical cable model JackPot. The precise trajectories ofall individual strands, joint design, cabling configuration, spatialdistribution of the magnetic field, sample geometry and using experimentallydetermined interstrand resistance distributions have been taken into account.Although unable to predict the quench point due to the lack of athermal-hydraulic routine, the model allows to assess the instantaneous strandpower at quench and its local distribution in the cable, showing the hot spots,once the quench conditions in terms of current and temperature areexperimentally known., The analysis points out the relation of the abovementioned factors with the DC quench stability of both short samples and coils.The possible small scale and local electrical-thermal interactions were ignoredin order to examine the relevance of such effects in the overall prediction ofthe CICC performance The electromagnetic code shows an excellent quantitativepredictive potential for CICC transport properties, excluding any freedom formatching the results. The influence of the local thermal effects in themodeling is identified as being marginal and far less than the generallyaccepted temperature margin for safe operation.