Magnetic Reconnection Measurements Using Quantum Beat Spectroscopy on Argon Ions

During laboratory experiments, the evolutions of magnetic fields in a plasma undergoing magnetic reconnection is typically measured with perturbative probes. In addition, these probes are sensitive to ambient electromagnetic noise that can make it difficult to obtain accurate velocity field distribution (VDF). Optical techniques such as laser induced fluorescence (LIF) have been used to measure Zeeman splitting of electronic transitions from argon atoms during magnetic reconnection. However, the classical LIF approach in measuring Zeeman splitting requires laser pulses over tens to hundreds of plasma discharges. These plasma discharges are also limited to magnetic fields that are large enough to overcome thermal Doppler Broadening of the split electronic states. An alternative approach for these measurements is using laser-based Doppler-free technique known as quantum beam spectroscopy (QBS). With the use of QBS, we are able to measure weak, localized magnetic fields with single laser pulses during a single flux rope discharge. Here we present measurements of Zeeman-split electron energy states of argon ions in a plasma. From the beat frequency of the fluoresce, we are able to obtain measurements of the local magnetic field strength at specific desired locations.