Development of a Position Sensitive Beta and Recoil Ion Detectors for the $^6$He $\beta-\nu$ Angular Correlation Measurement

In order to measure the $\beta-\nu$ angular correlation coefficient {\em a} and put more stringent limits on exotic tensor type weak currents, we constructed a system which detects $\beta$ particles in coincidence with recoil ions from the $\beta$-decay of laser trapped $^6$He atoms. The $\beta$ particles are detected by a scintillator and a multi-wire proportional chamber (MWPC) with a capacitive charge division anode. The recoil ions are detected by a microchannel plate (MCP) with delay-line anodes. The coefficient {\em a} is extracted by fitting the coincidence data to GEANT4 based Monte Carlo simulations, which are also used to study systematic uncertainties related to the detector system. A new method of calibrating the MWPC using a cathode focusing effect will be presented. This work is supported by DOE, Office of Nuclear Physics, under contract nos. DE-AC02-06CH11357 and DE-FG02-97ER41020.