Quench propagation and detection in the superconducting bus-bars of the ATLAS magnets

The ATLAS superconducting magnet system comprising Barrel (BT) and End-Cap Toroids (ECT) and also Central Solenoid (CS) will store more than 1.5 GJ of magnetic energy. The magnet system will have many superconducting busbars, a few meters long each, running from the current leads to Central Solenoid and Toroids as well as between the coils of each Toroid. Quench developmen t in the busbars, i.e., the normal zone propagation process along the; busb ar superconductors, is slow and exhibits very low voltages. Therefore, its timely and appropriate detection represents a real challenge. The temperatu re evolution in the busbars under quench is of primary importance. Conserva tive calculations of the temperature were performed for all the magnets. Al so, a simple and effective method to detect a normal zone in a busbar is pr esented. A thin superconducting wire, which normal resistance can be easily detected,is placed in a good thermal contact to busbar, Thus, the wire can operate as a straightforward and low-noise quench-detector.