The upper limit of the branching ratio for radiative beta-decay of free neutron

We conducted the experiment on radiative neutron beta-decay on a intensive cold neutron beam at ILL during April and May of 2002. This work is dedicated to the analysis of the methodology and the results of the study. The main outcome of this experiment is the branching ratio (BR) for the rare neutron decay mode in the gamma-quanta energy region from 35 to 100 KeV. The limit obtained is BR $< 6.9 \cdot 10^{-3}$ (90% C.L.), which is only a few permilles greater than the theoretical BR value, calculated within the standard weak interactions model.