James Chadwick ran experiments with radioactive toothpaste in a prison camp stable
Trapped in Germany when the First World War broke out, young physicist James Chadwick spent four years in Ruhleben internment camp near Berlin. He set up a laboratory in the stables and kept experimenting with whatever he could scrounge, including radioactive toothpaste. Later he discovered the neutron and won a Nobel Prize.
Chadwick was born in Cheshire on 20 October 1891, the son of a cotton spinner and a domestic servant. His family could not afford the small fees at Manchester Grammar School despite his scholarship offer, so he went to a cheaper school. At the University of Manchester, which he entered in 1908, he intended to study mathematics but enrolled in physics by mistake, walking four miles each way from home. Ernest Rutherford set him a project comparing the radioactivity of two sources; Chadwick saw that Rutherford's suggested method would fail but was too afraid to say so and found another way.
In 1913 a scholarship took him to Berlin to work under Hans Geiger, where the new Geiger counter let him show that beta radiation forms a continuous spectrum rather than discrete lines. Then came internment. Released after the armistice, he followed Rutherford to the Cavendish Laboratory in Cambridge, became his assistant director of research, and helped pick students such as John Cockcroft and Mark Oliphant. Kapitza was best man at his 1925 wedding.
Physicists then thought the nucleus held protons and electrons, which gave nitrogen the right mass and charge but the wrong spin. Hunting for a neutral particle, Chadwick needed a clean alpha source; Lise Meitner sent polonium from Germany. His discovery of the neutron earned the 1935 Nobel Prize in Physics, and he went on to measure its mass.
Frustrated that Rutherford refused to buy a cyclotron, he moved in 1935 to Liverpool, whose lab still ran on direct current. His cyclotron, with a magnet weighing 50 tons, was running by July 1939 and cost £5,184, more than the grants he raised, so he covered the gap from his Nobel money. He completed the 1941 MAUD Report, which spurred serious American atomic bomb research, and he led the British team on the Manhattan Project. He was knighted in 1945 and died on 24 July 1974.
Source: James Chadwick
