In 1939, through Wertenstein's connections, Rotblat was invited to study in Paris and at the University of Liverpool under James Chadwick, winner of the 1932 Nobel Prize for discovering the neutron. Chadwick was building a particle accelerator called a " cyclotron " to study fundamental nuclear reactions, and Rotblat wanted to build a similar machine in Warsaw, so he decided to join Chadwick in Liverpool. He travelled to England alone because he could not afford to support his wife there.