The UCNA+ Experiment at the Los Alamos Ultracold Neutron Source

UCNA+ will measure the angular correlation parameter A₀ in neutron beta-decay using ultracold neutrons to a planned sensitivity of ≤ 0.2%. The asymmetry parameter is to leading order a function of λ≡g_A/g_V and when combined with measurements of the neutron lifetime tests of the unitarity of the CKM and searches for beyond the standard model physics can be performed. The upgrade of the UCNA experiment will take advantage improvements to the ultracold neutron source which will increase the statistical precision and a redesign of the electron detectors to mitigate electron scattering systematic effects. Prototype electron detectors, using 128 edge coupled SiPM for energy and position reconstruction, have been developed and bench-tested. These detectors will begin vacuum and magnetic field testing in the Summer of 2025. We will report on the progress toward the UCNA+ experiment and the results of the vacuum tests of the detectors.