A method for controlling the magnetic field near a superconducting boundary in the ARIADNE axion experiment

Abstract The QCD axion is a particle postulated to exist since the 1970s explain strong-CP problem in physics. It could also account for all of observed dark matter Universe. resonant interaction detection experiment (ARIADNE) intends detect by sensing fictitious ‘magnetic field’ created its coupling spin. Short-range axion-mediated interactions can occur between sample laser-polarized 3 He nuclear spins and an unpolarized source-mass sprocket. must be sensitive magnetic fields below 10 −19 T level achieve design sensitivity, necessitating tight control experiment’s environment. We describe method controlling three aspects that environment which would otherwise limit experimental sensitivity. Firstly, system superconducting shielding described screen ordinary noise from volume at 8 level, should sufficient reduce contribution Johnson sprocket-shaped source mass, expected −12 / H mathvariant="normal">z threshold signal detection. Secondly, reducing field gradients within up 2 times described, using simple cost-effective geometry. Thirdly, novel coil introduced allows generation similar those produced Helmholtz coils regions directly abutting boundaries. This Larmor frequency tuned match modulation set sprocket rotation. Finally, we experimentally investigate factor sputtered thin-film niobium on quartz substrates various geometries film thicknesses relevant ARIADNE SQUID magnetometry. methods may generally useful near boundaries other experiments where considerations apply.