Stability dependence on flow in a CICC P. Bellucci a , M. Ciotti b, * , P. Gislon b , L. Muzzi c,d , M. Spadoni b a INFM––Physics Department, University of Salerno, 84081 Baronissi, Italy b Superconductivity Division, Associazione EURATOM-ENEA sulla Fusione, C.E. Frascati, Via Enrico Fermi, 45, 00044 Frascati (Rome), Italy c INFM––Physics Department, University of Salerno, 84081 Baronissi, Italy d Physics Department, University of Tor Vergata, 00133 Rome, Italy Abstract Stability versus all foreseen disturbances is a crucial issue for a superconducting coil in order to be safely used in the magnetic system of a fusion reactor. Whether stability in a cable-in-conduit conductor (CICC) may depend on the cooling helium flow is at the moment a controversial point. This paper deals with experimental results on an instru- mented CICC NbTi solenoid and their comparison with the predictions of the thermal-hydraulic simulation code Gandalf. No flow dependence of the stability margin has been evidenced experimentally, a result not in agreement with the simulations. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Cable-in-conduit conductor; Stability; Numerical code 1. Introduction Whether stability dependence on coolant flow in a cable-in-conduit conductor (CICC) can be considered as a relevant issue has been debated since a long time. The topic was first discussed by Dresner [1], who found multi-valued stability for specific com- binations of transport current, ambient helium pressure and externally imposed helium flow. He also showed that there is a limiting transport current below which the stability margin is single valued and equal to the upper stability margin. The thermo-hydraulic codes presently available describe in details the CICC behaviour, and the predictions of the consequence of induced distur- bances are becoming more and more accurate. Experiments on this topic can be divided into two different categories: the first one concerns induced helium flow speed, which is negligible as compared to the stationary flow. This may happen under specific conditions of current, disturbance energy/ power and conductor geometrical parameters. This mix of parameters can be typically reached for ‘‘long-length’’ conductors when the transition starts far away from one of the extremities; or, for very short conductor lengths, where no significant change in flow conditions takes place, due to the predominance of the external hydraulic circuit. These are respectively the cases where helium heat Physica C 372–376 (2002) 1419–1422 www.elsevier.com/locate/physc * Corresponding author. Tel.: +39-06-9400-5767; fax: +39- 06-9400-5393. E-mail address: ciotti@frascati.enea.it (M. Ciotti). 0921-4534/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S0921-4534(02)01044-4