Bidirectional, Analog Current Source Benchmarked with Gray Molasses-Assisted Stray Magnetic Field Compensation

TL;DR

This paper introduces a modular, analog electronic circuit for three-dimensional magnetic field control in ultracold-atom experiments, enabling smooth current transitions and effective stray field compensation without direct measurement.

Contribution

The work presents a novel, modular circuit design that allows continuous, zero-crossing current control in three axes for ultracold experiments, improving magnetic field stability and compensation techniques.

Findings

Achieved stable current control at 10^{-5} level.

Enabled magnetic field compensation without measuring stray fields.

Demonstrated improved sub-Doppler cooling efficiency.

Abstract

In ultracold-atom and ion experiments, flexible control of the direction and amplitude of a uniform magnetic field is necessary. It is achieved almost exclusively by controlling the current flowing through coils surrounding the experimental chamber. Here, we present the design and characterization of a modular, analog electronic circuit that enables three-dimensional control of a magnetic field via the amplitude and direction of a current flowing through three perpendicular pairs of coils. Each pair is controlled by one module, and we are able to continuously change the current flowing thorough the coils in the $\pm$4 A range using analog waveforms such that smooth crossing through zero as the current's direction changes is possible. With the electrical current stability at the 10$^{-5}$ level, the designed circuit enables state-of-the-art ultracold experiments. As a benchmark, we use the circuit to compensate stray magnetic fields that hinder efficient sub-Doppler cooling of alkali atoms in gray molasses. We demonstrate how such compensation can be achieved without actually measuring the stray fields present, thus speeding up the process of optimization of various laser cooling stages.