Speaker
Description
We present the performance characterization of a Magnetically Shielded Room (MSR) designed to meet the stringent magnetic requirements of next-generation $^3$He/$^{129}$Xe co-magnetometer experiments, in particular the search for a permanent electric dipole moment (EDM) of $^{129}$Xe. The Xenon EDM experiment aims to probe new sources of CP violation beyond the Standard Model with unprecedented sensitivity, requiring a magnetically quiet environment with residual fields well below the nanotesla range and ultra-low magnetic field gradients. The MSR features a cubical walk-in volume with an edge length of 2560 mm and comprises three layers of 3 mm thick Mu-metal, complemented by a 8 mm thick copper-coated aluminum layer. An optimized magnetic equilibration (degaussing) procedure is introduced, consisting of a frequency sweep at constant amplitude followed by an exponential amplitude decay. This complete degaussing cycle requires 21 minutes and reliably reduces the residual magnetic field at the center of the MSR to below 1 nT. The choice of this procedure is supported by in-situ hysteresis measurements of the fully assembled MSR and eddy current simulations, both indicating saturation at the center of the Mu-metal layers. Furthermore, shielding factors can be improved by approximately a factor of 4 in all spatial directions through low-frequency (0.2 Hz), low-amplitude (1 A) magnetic shaking applied to the outermost Mu-metal layer. Finally, we present a gradient compensation system installed inside the MSR and report high-precision measurements of magnetic field gradients. These gradients are extracted from transverse relaxation rates of precessing $^{129}$Xe spin samples, achieving a resolution below 1 pT/cm.
