LANL nEDM half scale B₀ prototype design and test of the field gradient inside a MSR at LANL

The measurement of the electric dipole moment of the neutron (nEDM) plays a significant role in finding sources of beyond standard model CP violating physics. The goal of the LANL nEDM experiment is to push the upper limit of the nEDM < 3×10^-27  e·cm (68 % CL). A highly uniform magnetic field is key to achieving this substantially high sensitivity for the nEDM measurement by reducing the systematic uncertainties associated with the magnetic field non uniformity. The B₀ coil provides the required field uniformity of < 0.3 nT·m^-1 at a nominal holding field of 1 µT. This talk will discuss a novel technique employed in the construction of the half scale B₀ prototype and the resulting field maps obtained with a half-scale prototype coil housed in a magnetically shielded room (MSR).

As UCNs move from the source to the cells, those located between the MSR layers experience a large field gradient, which would otherwise cause depolarization. In the LANL nEDM experiment, a double cos theta coil will serve as the basis for spin transport coils, which will minimize the depolarization of the neutrons, thereby increasing the statistical sensitivity. Finally, this talk will discuss the implementation of these spin transport coils, including a design to incorporate them with the B₀ coil which prevents leakage field gradients in the neutron storage cell volumes.