UWB radiation from superconductor undergoing fast superconducting to normal transition

Radiation from superconducting current loops undergoing fast superconducting to normal (S-N) transitions is investigated. We consider 2 geometries: 1) a double loop configuration where current initially circulates in one loop and redirects /shunts to an adjacent loop and 2) A single loop that suddenly becomes resistive globally. For both geometries, we derive delayed integro-differential equations that fully take into account radiation and near field effects. Using a perturbation approach, we tie theory to experiment involving Ultra Wide Band (UWB) radiation from superconducting switches. Next we extrapolate parameters from this model, such as an effective inductance, that make the radiation more efficient. Focusing on the single loop geometry, we move away from the perturbation approach and explore regimes that fully incorporate radiation and the near field. We observe oscillatory behavior that departs from the classic RL circuit. These current oscillations are a result of a two way energy transfer between the circuit and the near field region. Practical applications of this type of a radiation source are also discussed.