... Activity/Close Support Unit (EFDA/CSU), Garching, in collaboration with the Europeansupercond... more ... Activity/Close Support Unit (EFDA/CSU), Garching, in collaboration with the Europeansuperconductor laboratories and ... coil 3.7.1. Voltage taps 3.7.2. Temperature sensors 3.7.3. Strain gauges, rosettes ... AC tests 9.3.1. Withstand tests 9.3.2. Partial discharge measurement 9.3.3 ...
Experiments were performed to measure directly the current in each strand of a 12-strand Nb3Sn ca... more Experiments were performed to measure directly the current in each strand of a 12-strand Nb3Sn cable-in-conduit superconductor during current and/or external magnetic field ramps. The goal of the experiment was to get straightforward evidence of current maldistribution in a cable-in-conduit conductor (CICC). A heavily instrumented sample coil from Nb3Sn TPX-TF strands was specially prepared. Severe non-uniformity of the strand currents were found during field ramp. Immediately before a quench the individual strand currents within a triplet differed by as much as an order of magnitude. During field ramps with constant transport current, the currents in some strands were observed to drop rapidly and then recover. The data show that quench development in the CICC is a complicated phenomenon involving dynamic redistribution of current among the strands. Non-uniformity of current along the strands during quench was also observed.
IEEE Transactions on Applied Superconductivity, 2000
Large superconducting magnets will play a central role in the success of the International Thermo... more Large superconducting magnets will play a central role in the success of the International Thermonuclear Experimental Reactor (ITER) and for the future of fusion energy. Cable-in-conduit conductors (CICC) will be used for the ITER magnets. As a CICC is energized, electromagnetic forces accumulate across the conductor, pressing strands transversely against one side of the conduit. We have developed a device
A 27 strand hybrid superconducting Cable-In-Conduit Conductor (CICC) sample (so-called TPX-PF mod... more A 27 strand hybrid superconducting Cable-In-Conduit Conductor (CICC) sample (so-called TPX-PF model sample) has been fabricated and tested in quickly ramped background magnetic fields. The voltage spikes that appeared in the sample's terminal voltages during magnetic field sweeps at DC transport current are analyzed using a model that calculates the magnitude of individual strand current drops and the strand to strand/cable inductances associated with each voltage spike. Dependencies of the strand inductances and current variations with consecutive voltage spike numbers, total transport current in the cable and background magnetic field are analyzed and discussed. The analysis confirms previously reported suggestions that voltage spikes and the corresponding rapid variations, or jumps, observed in the conductor's local magnetic field are indications of rapid redistribution of current from one of the cable's strands in which the current reached its critical level. It is shown that rapid current redistributions which are too small to initiate total cable quench lead to more uniform distribution of current among the strands in the CICC. Therefore, it may be possible to apply small disturbances to a CICC to improve its strand to strand current distribution in a cable and to stabilize its Ramp Rate Limitation behavior.
... Activity/Close Support Unit (EFDA/CSU), Garching, in collaboration with the Europeansupercond... more ... Activity/Close Support Unit (EFDA/CSU), Garching, in collaboration with the Europeansuperconductor laboratories and ... coil 3.7.1. Voltage taps 3.7.2. Temperature sensors 3.7.3. Strain gauges, rosettes ... AC tests 9.3.1. Withstand tests 9.3.2. Partial discharge measurement 9.3.3 ...
Experiments were performed to measure directly the current in each strand of a 12-strand Nb3Sn ca... more Experiments were performed to measure directly the current in each strand of a 12-strand Nb3Sn cable-in-conduit superconductor during current and/or external magnetic field ramps. The goal of the experiment was to get straightforward evidence of current maldistribution in a cable-in-conduit conductor (CICC). A heavily instrumented sample coil from Nb3Sn TPX-TF strands was specially prepared. Severe non-uniformity of the strand currents were found during field ramp. Immediately before a quench the individual strand currents within a triplet differed by as much as an order of magnitude. During field ramps with constant transport current, the currents in some strands were observed to drop rapidly and then recover. The data show that quench development in the CICC is a complicated phenomenon involving dynamic redistribution of current among the strands. Non-uniformity of current along the strands during quench was also observed.
IEEE Transactions on Applied Superconductivity, 2000
Large superconducting magnets will play a central role in the success of the International Thermo... more Large superconducting magnets will play a central role in the success of the International Thermonuclear Experimental Reactor (ITER) and for the future of fusion energy. Cable-in-conduit conductors (CICC) will be used for the ITER magnets. As a CICC is energized, electromagnetic forces accumulate across the conductor, pressing strands transversely against one side of the conduit. We have developed a device
A 27 strand hybrid superconducting Cable-In-Conduit Conductor (CICC) sample (so-called TPX-PF mod... more A 27 strand hybrid superconducting Cable-In-Conduit Conductor (CICC) sample (so-called TPX-PF model sample) has been fabricated and tested in quickly ramped background magnetic fields. The voltage spikes that appeared in the sample's terminal voltages during magnetic field sweeps at DC transport current are analyzed using a model that calculates the magnitude of individual strand current drops and the strand to strand/cable inductances associated with each voltage spike. Dependencies of the strand inductances and current variations with consecutive voltage spike numbers, total transport current in the cable and background magnetic field are analyzed and discussed. The analysis confirms previously reported suggestions that voltage spikes and the corresponding rapid variations, or jumps, observed in the conductor's local magnetic field are indications of rapid redistribution of current from one of the cable's strands in which the current reached its critical level. It is shown that rapid current redistributions which are too small to initiate total cable quench lead to more uniform distribution of current among the strands in the CICC. Therefore, it may be possible to apply small disturbances to a CICC to improve its strand to strand current distribution in a cable and to stabilize its Ramp Rate Limitation behavior.
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