Ivan Puluj in the UK. While Professor Puluj's finding were essentially X-rays, he did not recognise them as such at first, although he demonstrated X-ray pictures of a hand and fingers obtained by using his tube / lamp to his students. This credit later went on to Wilhelm Conrad Röntgen. Once Roentgen visited Professor Puluj's laboratory and the latter presented one of his tubes to Roentgen. Roentgen went home and in his laboratory started to conduct experiments with Puluj's tube. Puluj also continued to do research with his X-ray tubes. On 8 February 1896, just 6 weeks after Röntgen presented his finding
Roentgen (unit) 0.2 roentgen per day in 1934. In 1950, the ICRP reduced their recommended limit to 0.3 roentgen per week for whole-body exposure. The International Commission on Radiation Units and Measurements (ICRU) took over the definition of the roentgen in 1950, defining it as "the quantity of X or γ-radiation such that the associated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying 1 electrostatic unit of quantity of electricity of either sign." The 3 MeV cap was no longer part of the definition, but the degraded usefulness of this unit at high beam energies was mentioned in