In the 50 years since Brockhouse's invention, neutron spectroscopy has become a standard tool of physics. The neutron, an electrically neutral particle, is able to penetrate deep in the interior of matter; it possesses a magnetic moment and has, at room temperature, a wavelength that nicely matches the distance between atoms in solids and liquids. Dozens of reactors, and more recently accelerators, have been built for neutron spectroscopy: the new Spallation Neutron Source in Oak Ridge, Tennessee, will provide the most intense pulsed neutron beams ever used in research, and, at a total cost of US$1.4 billion, is one of the largest scientific projects in the world.
Brockhouse was raised on a farm in Alberta but showed an early interest in electronics, running a small radio repair business before joining the Canadian Navy at the start of the Second World War. After physics degrees from the Universities of British Columbia and Toronto, in 1950 Brockhouse joined the Chalk River Nuclear Laboratory in Toronto. Encouraged by Don Hurst there, who had already built a prototype neutron spectrometer, he started building a series of increasingly sophisticated neutron spectrometers to study excitations in solids. Unlike Shull, who worked on the static positions of atoms and spins, Brockhouse focused on their movements. For this, he needed to measure the neutrons' energy change as they scattered from his sample, tying down the incoming and outgoing neutron energies, as well as the momentum transfer ('Q') from the neutron to an excitation in the sample.
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