ASTRA (reactor)

Research

One of the most advanced experiments in physics carried out at the ASTRA reactor was an experiment on the decay of free neutrons. In this experiment, the electron-neutrino angular correlation in free neutron decay was measured via the shape of the energy spectrum of the recoil protons; the center of a highly evacuated tangential beam tube of the reactor served as neutron source.

The aim was to determine the ratio of the two coupling constants g_A and g_V of the weak interaction from the shape of the recoil proton spectrum. This spectrum was measured using an electrostatic spectrometer; the protons were counted using an ion electron converter of the coincidence type.

The result was |g_A/g_V| = 1.259 ± 0.017. This is in good agreement with the later (much more accurate) average g_A/g_V = - 1.2695 ± 0.0029; this value was measured using polarised neutrons and hence contains also the sign of the ratio.