Neutron Sciences Directorate

HYSPEC is a versatile spectrometer that allows for ground-breaking investigations of the low-energy, atomic-scale dynamical properties of crystalline solids. Its Bragg focusing optics makes it well suited for measurement of excitations in small single-crystal specimens in a wide range of ancillary sample environments. Full or partial neutron polarization analysis can be deployed to provide unambiguous separation of nuclear and magnetic scattering.

HYSPEC is a high-intensity, time-of-flight, direct-geometry spectrometer (DGS). The incident neutron beam is monochromated using a Fermi chopper with short, straight blades, and is then vertically focused by Bragg scattering onto the sample position by either a highly-oriented pyrolitic graphite (unpolarized) or a Heusler (polarized) crystal array. Neutrons are detected by a bank of ³He tubes that can be positioned over a wide range of scattering angles about the sample vertical axis. Polarization analysis is accomplished by using the Heusler crystal array to polarize the incident beam, and a supermirror wide-angle polarization analyzer, designed and fabricated by the Paul Sherrer Institut, to analyze the scattered beam.

HYSPEC’s niche among the family of DGS’s at the SNS and the triple axis spectrometers at HFIR includes:

• Polarization analysis option 
• Large configurable horizontal angle detector acceptance
• Vertical focusing enables good statistics, for either small single crystals or extreme conditions
• A cold neutron incident energy range optimized for 3.8 meV < Ei < 60 meV unpolarized and  3.8 meV < Ei < 25 meV polarized
• Moderate energy transfer resolution, between that of CNCS andcold neutron triple-axis spectrometers such as CTAX at HFIR