Performance of the solid deuterium ultra-cold neutron source at the pulsed reactor TRIGA Mainz

The performance of the solid deuterium ultra-cold neutron (UCN) source at the pulsed reactor TRIGA Mainz with a maximum peak energy of 10MJ is described. The solid deuterium converter with a volume of $ V=160$ cm3 (8mol), which is exposed to a thermal neutron fluence of $ 4.5\times 10^{13}$ n/cm2, delivers up to 240000 UCN ($v \le 6$ m/s) per pulse outside the biological shield at the experimental area. UCN densities of $ \approx $ 10 cm3 are obtained in stainless-steel bottles of $ V\approx $ 10 L. The measured UCN yields compare well with the predictions from a Monte Carlo simulation developed to model the source and to optimize its performance for the upcoming upgrade of the TRIGA Mainz into a user facility for UCN physics