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Description
The design and simulation of a modified Rayleigh Line Pulse Forming Network (PFN) is presented for active quench protection of superconducting magnets. In this context, the PFN is a network of capacitors and inductors designed to deliver energy to quench heaters over a significantly longer period than a single capacitor or capacitor bank. The PFN is advantageous for protection of coils constructed with REBCO tape, which have a slow normal zone propagation speed and a high critical temperature. PFN’s also have an inherent safety advantage over battery bank energy sources.
The rise time of a typical Rayleigh network for this purpose can be on the order of 10-100 ms which is unacceptably slow compared to the timescale for thermal runaway during the onset of a quench. This is exacerbated by the time required for quench detection and the time it takes for energy to percolate from the heaters, through layers of electrical insulation, and into the superconductor. Thus, as a modification to the Rayleigh Line PFN, an extra stage consisting of a discharging capacitor with no accompanying inductor is added to achieve a nearly instant rise time. The advantages of this strategy are discussed, and the flexibility of the system is investigated when varying resistive loads, charge voltages, and component design.
This work was performed at Florida State University’s National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement Numbers DMR-1644779 and DMR-1839796 and the State of Florida.
