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Chapter 2: High-Flux Years

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ERNEST WOLLAN: BADGE OF SOLID DISTINCTION

Ernest Wollan, who had studied crystal structures using X-ray diffraction under Arthur Compton at the University of Chicago, came to Oak Ridge in 1943. Known for developing the film badge to monitor personal exposure to radiation, Wollan was present at the University of Chicago's Stagg Field on December 2, 1942, when Enrico Fermi's team achieved the first self-sustaining nuclear chain reaction. He recorded the event on an instrument that measured the intensity of the gamma radiation emitted in the reaction.

Wollan came to Oak Ridge as a health physicist, and the Laboratory hoped to use his expertise on film-badge dosimeters. His interest in and experience with X-ray diffraction, however, prompted him to conduct similar experiments using neutrons.

Ernest Wollan
and Clifford Shull conducted some of the world's first neutron scattering
experiments using this diffractometer built at ORNL and installed at the
Graphite Reactor in 1950.
Ernest Wollan and Clifford Shull conducted some of the world's first neutron scattering experiments using this diffractometer built at ORNL and installed at the Graphite Reactor in 1950.

Installing a modified X-ray diffractrometer at a beam hole of the Graphite Reactor in late 1945, he examined the scattering of neutrons from various materials bombarded by a neutron beam from the reactor. Thermal, or slow, neutrons have ideal wavelengths for studying atomic structure and atomic vibrations, and because they have no more energy than a molecule of room-temperature air, they hardly disturb the materials. These and other properties make neutron scattering a valuable scientific tool.

Joined by Clifford Shull in 1946 and later by Wallace Koehler and Mike Wilkinson, Wollan and his associates devised machines and diffraction techniques for determining the atomic structure and magnetic properties of crystal lattices. This work laid the foundation for a number of programs in solid-state physics and materials science at the Laboratory and, later, throughout the world.

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