Stabilization and control of persistent current magnets using variable inductance

Abstract Ultra-stable, tunable magnetic fields are desirable for a wide range of applications in medical imaging, electron microscopy, quantum science, and atomic physics. Superconducting magnets operated persistent current mode, with device flowing closed superconducting loop disconnected from power source, common approach the most stringent requirements on temporal field stability. We present method active control this by means dynamic inductance change within circuit. For first realization general technique, we consider variable inductor placed series main magnet. The acts as flux storage capable transferring to or magnet through change. This allows fine fast adjustments without use thermal switches that limit speed accuracy many present-day methods. With experiments employing demonstrate stabilization 1.95 T Nb–Ti round lens microscopy against decay resulting residual losses circuit, more generally show flexibility precise over magnitude waveform current.