Free-Neutron Beta-Decay Half-Life

The $\beta$-decay half-life of the free neutron was measured. Greater accuracy was obtained through the development of a special $4\pi \beta$ spectrometer with a well-defined source volume and through the use of a new density calibration method with a ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ proportional counter. A clean thermal-neutron beam was developed especially for the measurement. The final result is a half-life of 10.61 ± 0.16 min. The derived value of $\frac{g_A}{g_V}$ is -1.239 ± 0.011.