Searching for Tensor Current in $^6$He $\beta$-Decay*

Precision measurement of the $\beta-\bar\nu_e$ angular correlation coefficient {\em a} can be used for searching for the Beyond-Standard-Model tensor-type weak currents. We produce $10^{10}$ $^6$He atoms per second using the Van de Graaff accelerator at CENPA, and deliver them to a magneto-optical trap (MOT) in a low background experiment hall. We measure the time-of-flight spectrum of the recoiling $^{6}{\rm Li}$ ions from $^6$He $\beta$-decay and then extract the $\beta-\bar\nu_e$ angular correlation coefficient {\em a}. The $\beta$-particles are detected by a multi-wire proportional chamber and a plastic scintillator, while the recoil ions are guided by an electric field and detected by a micro-channel plate. We developed a Monte Carlo simulation program to construct the fitting templates of the time-of-flight spectrum and study the systematic effects. We currently acquire coincidence data with the short term goal of reaching a 1\% uncertainty for a.