Constant by measuring the quotient of the Planck constant and the neutron mass

At the high-flux reactor of the Institut Laue-Langevin in Grenoble the fine-structure constant was measured with a relative uncertainty of 3.9×10^-8. It was the first time that this fundamental constant had been determined by means of neutrons. After the publication of the result, the experiment was continued. The reproducibility of the result was tested after the measurements had been interrupted for four years. Subsequently, a check was made to see if an essential contribution to the uncertainty had been correctly estimated. The reproducibility was very good and the estimation confirmed