UCNA+: An improved measurement of the beta assymetry parameter with ultracold neutrons.

Beta-decay angular correlation coefficients can be written in terms of λ, the ratio of the axial-vector and vector coupling constants.  Combining measurements of the neutron lifetime and the correlation coefficients allows for precision tests of the standard model and a complementary cross-check of Superallowed Fermi decays. The UCNA experiment at the Los Alamos ultracold neutron source measured the beta-asymmetry coefficient A to a precision of 0.55% using a 2x2π magnetic spectrometer.  It was limited by electron scattering systematics due to inactive material and low UCN density.  UCNA+ will replace the multiwire proportional count and plastic scintillator detection system with a 16 sided plastic scintillator with edge coupled SiPM readout to minimize scattering systematics and take advantage of upgrades to LANL UCN source to increase the UCN density by a factor roughly 6.  We will present details of detector upgrades and the path towards  a 0.2% determination of A.