DEVELOPMENT OF GALLIUM-INDIUM ALLOYS AS NONMAGNETIC TEST MASSES FOR SPIN-DEPENDENT SHORT-RANGE FORCE EXPERIMENTS

Abstract

Various studies have been done on exotic spin-dependent short-range forces in the mm to μm range. We are using an ensemble of optically polarized $^3$He gas and an unpolarized test mass to search for such forces. The presence or absence of a Nuclear Magnetic Resonance (NMR) frequency shift when an unpolarized mass is moved away and towards the $^3$He is our experimental signal [1]. It is very important to have no influence from the magnetism of the mass itself on the NMR frequency measurement. This research explicitly deals with preparation and characterization of unpolarized non-magnetic test masses using Gallium/Indium alloys that have very low magnetic susceptibility. We believe the current limit on the NMR frequency shift ceramic (2.6 ± 1.7 10$^{-5}$ Hz), salt water (-0.8 ± 2.6 10$^{-5}$ Hz) due to such spin-dependent forces from a previous experiment using Macor ceramic and 1.02% MnCl$_2$ solution can be improved with the use of these lower magnetic susceptibility test masses.