Brockhouse’s triple-axis spectrometer, mounted at one of the "windows" of the NRU nuclear reactor, allowed him to study crystals or condensed matter fluids in a new way. Experimenters could "select" neutrons of similar energy or "colour" (monochromatic) which then collide with the sample, for example, a "grown" aluminum crystal. By scattering neutrons (sub-atomic particles of high energy) off the nuclei of atoms held in the sample’s crystal structure, the direction of scatter and the speed with which the atoms move after a collision with a neutron can be measured.
This was the first of many such instruments used at research reactors around the world. The techniques developed by Brockhouse are used to study such topics as ceramic superconductors, catalytic exhaust cleaning, elastic properties of polymers and structures of viruses.