USJ-TAX  -  US-Japan Triple Axis Spectrometer

Triple Axis Spectrometer

A triple axis spectrometer (TAX) is a Nobel Prize winning class of instruments at reactor-based neutron scattering facilities, developed by B. N. Brockhouse in the 1950’s. The neutron momentum matches to crystal lattice dimensions, and the neutron kinetic energy matches to excitations (phonons, magnons, etc.), enabling simultaneous study of structure and dynamics. At the 3 axes are (1) the monochromator crystal whose angle selects incident energy via Bragg’s law, (2) the sample, which scatters and possibly exchanges energy with the neutrons, and (3) the analyzer crystal which selects final energy.

Compared to neutron time-of-flight spectrometers with comparable ranges and resolution for energy and momentum transfer, TAX’s allow powerful focusing techniques, more flexible manipulation of the resolution function, and an effective reduction of neutron background via neutron transport.

Compared to inelastic x-ray spectrometers, TAX’s allows a better energy resolution with relaxed momentum resolution, a different cross section criteria (electron scattering for x-rays, vs. nuclear and magnetic scattering for neutrons), and a generally larger penetration depth enabling studies of the bulk (a good match to the larger momentum resolution, given the comparable mosaic of typical crystal samples).

For more on triple axis spectrometry, we recommend our references on neutrons scattering page.

Last Modified: Tuesday, 04-Mar-2008 14:52:52 EST
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