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> Figures In Radiation History
In 1907, while enrolling at the University of Manchester, James
Chadwick accidentally found himself in the line for those hoping
to major in physics. Chadwick, who had intended to be a mathematician,
was too shy to admit he was mistaken and stayed in line. Thus began
the career of one of this century's most distinguished physicists.
In 1913 he received his master's degree and left for Germany to
work with Hans Geiger. There, Chadwick was the first to show that
beta particles possess a range of energies up to some maximum value.
Trapped in Germany when WW I broke out, Chadwick was imprisoned
in a horse stall at a racetrack that served as an internment camp.
As soon as the war ended and he gained his freedom, Chadwick returned
to England and joined forces with Ernest Rutherford. Intrigued by
Rutherford's speculation about a subatomic particle with no charge,
Chadwick began a series of experiments to demonstrate the existence
of such a particle. Initially, none of the experiments succeeded.
Then, in 1930, Walther Bothe and Herbert Becker described an unusual
type of gamma ray produced by bombarding the metal beryllium with
alpha particles. Chadwick recognized that the properties of this
radiation were more consistent with what would be expected from
Rutherford's neutral particle. When Frédéric and Irène
Joliot-Curie subsequently claimed that Bothe and Becker's "gamma
rays" could eject high energy protons from paraffin, Chadwick knew
these were not gamma rays. The subsequent experiments by which Chadwick
proved the existence of the neutron earned him the 1935 Nobel Prize
in physics. Not only did this singular particle provide physicists
with a superlative tool for investigating the atom, it was also
used to produce a wide variety of new radioisotopes and permitted
the initiation of nuclear chain reactions. Hans Bethe has referred
to Chadwick's discovery as the historical beginning of nuclear physics.
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