Unbalanced Quenching in a Long Solenoid With Separately Powered Coils

Quenches were simulated for a long solenoid composed of five separately powered coils. Two coils, at one end of the magnet, are separately powered by 300-A power supplies, so that the uniform field section of the magnet is matched to the rest of a physics experiment. The three coils in the uniform field end are connected in series and are powered by a single 300-A power supply. The two end coils of the three-coil set use separate 60-A power supplies to trim the uniform field. Quench back from the 6061-Al mandrel is an important part of the quench protection for the three-coil section. Quench propagation from one separately powered coil to the next was simulated by using the Opera3D program of the Vector Fields. Low current quench simulations showed that some coils carry currents for a long time before quenching. Since the magnet does not quench all at once, there can be unbalanced forces developed in the coils and the thermal shield.