Frédéric Joliot-Curie
In 1937 Halban was invited to join the team of Frédéric Joliot-Curie at the Collège de France in Paris. The team also included Francis Perrin and Lew Kowarski. In 1939 the group measured the mean number of neutrons emitted during nuclear fission, and established the possibility of nuclear chain reactions and nuclear energy production. In August the group showed that the rate of fission in uranium oxide was increased by immersion in ordinary water.