Fast Magnetic Coil Controller for Cold Atom Experiments

Abstract

Cold atoms experiments employ magnetic fields, commonly generated by coils, as an essential tool to control and manipulate atomic samples. In these experiments, it is often necessary to rapidly switch the magnetic field between two values. However, typical power supplies have a limited switching time for the current flowing through the coil. We present a control scheme implemented as an electronic circuit that overcomes this limitation. A faster control is achieved by momentarily applying an on-demand high voltage when the control signal variation surpasses the limits that the conventional power supply can follow, allowing a faster current flow into the magnetic coil. In our specific application, a coil with inductance of 491 ${\mu}H$ and resistance of 0.26 ${\Omega}$, corresponding to a time constant of ~1.9 ms, is driven so that its current faithfully follows the control signals from -1A to +1A. Capable of completing a full-scale transition in just ~31 ${\mu}s$, with an effective bandwidth of 15.2 kHz. This corresponds to an improvement by a factor of more than 20 in both bandwidth and switching speed over a conventional power supply. By appropriately selecting the components of the circuit, both the bandwidth and the switching time can be tuned to match specific needs within a wide range of inductive and power requirements.