Non-intrusive measurement of magnetic field strengths in a low-pressure argon plasma using quantum beat spectroscopy

Accurate measurement of magnetic field strengths is critical in many plasma environments, ranging from astrophysical systems to fusion energy research. In this work, a non-perturbative laser-based optical diagnostic known as quantum beat spectroscopy is demonstrated to be good alternative for measuring the magnetic field strength in low-pressure laboratory plasmas. The technique is investigated using both ns and fs pulsed lasers in an argon plasma. Preliminary results for a helium plasma are also given. Zeeman-split J = 1 electron states with transitions from metastable states were identified and tested for neutral argon ( 2 P 1 / 2 o ) 4 p 2 [ 1 / 2 ] and neutral helium 1 s 3 p 1 P 1 o . Magnetic fields are measured with sub-Gauss precision at near single laser pulse acquisition rates.