For many years it has been known that the properties and operating margins of superconducting magnets are influenced by the distribution of transport and induced currents among the strands in the cables with which the magnet is wound. In FRESCA, CERN’s test station for measuring electrical cable properties at 1.9 and 4.3 K, the voltage–current curve of Rutherford type cables and the homogeneity of the current distribution can be measured simultaneously. The longitudinal variation of the cable self-field is measured along one twist pitch, and taken as a measure for the variation of the strand currents. A change in the background field, which is applied non-uniformly along the length of the cable, will induce boundary induced coupling currents. These coupling currents decay very slowly and cause a variation in the strand currents, resulting in a different electro-magnetic behaviour of the cable, even long after the field sweep has finished. In this paper the experimental results on about 40 cables for large hadron collider magnets are presented in terms of quench current and apparent critical current and n-value. The measurements will be sustained by calculations.
|Number of pages||5|
|Publication status||Published - 2003|
|Event||Topical Conference ICMC 2003: The Voltage Current Relation In Technical Superconductors: Fundamentals And Implications - University of Twente , Enschede, Netherlands|
Duration: 25 May 2003 → 28 May 2003
- UI characteristic
- Current distribution
- Superconducting cables