Abstract-The normal zone propagation inside the 0 model coil of ATLAS Toroidal magnet has been measured over a large range of applied currents. Typical values for the longitudinal propagation vary from 0.3 to 15 m/s at 8 and 24 kA, respectively. A new analytical expression for the longitudinal quench propagation inside superconducting cables is presented. It describes the propagation inside superconducting wires as well as the propagation inside large stabilized superconductors. It is found that in the limit case of high currents, the stabilizer functions only as a heat-sink. The model is compared to the experimental data and a good correlation is found.
Abstract-Three pairs of 20.5 kA current leads for the ATLAS Toroid Magnets have been designed, manufactured and tested at Kurchatov Institute. The current leads have a high mechanical reliability and the vacuum tightness under 30 bars of internal pressure. The insulation between the current carrying parts and the mounting flange, the hydraulic connections and the temperature gauges withstand the overvoltage of at least 2 kV. The current leads are fully equipped with diagnostics needed for safety and control. The current leads were tested up to 24 kA. According to CERN's specification they were also tested in the absence of any cooling at very slow current discharge rate (5 A/s) from 20.5 kA to zero without any excessive overheating. Nowadays the current leads are successfully used at the ATLAS Magnet Test Facility at CERN.
During ramping up-and down of the current in large-scale magnets the ramp losses are an important factor affecting the thermal and electromagnetic stability of the system. The calculation of the losses is not straightforward due to the large dimensions of the conductor (~ 600 mm 2) implying that diffusion effects have to be taken into account. The AClosses of the Al stabilized NbTi cable conductors used in the ATLAS magnet system were measured in 0.5 m long samples, using an inductive method with pickup coils as well as the calorimetric method. External varying magnetic fields up to 2 tesla amplitude were applied parallel and perpendicular to the conductor wide surface. The results are compared to theory. It is found that hysteresis loss, eddy current loss in the Aluminum cladding and cable-to-cladding coupling loss contribute most to the AC loss.
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