Time-of-Flight Broadband Spectrometer (Under Design)



Instrument Description

BWAVES (Broadband Wide-Angle VElocity Selector spectrometer), is a neutron spectrometer that can select the velocity (that is, the wavelength) of detected neutrons after they are scattered by a sample. It is the first inverted geometry spectrometer where the energy of detected neutrons can be chosen mechanically by a wide-angle velocity selector, irrespective of limitations imposed by crystal analyzers or filters.

BWAVES will serve as a gateway (and often as the one-stop) spectrometer for neutron scattering studies of dynamics in a broad range of materials, in the same manner as the SANS and neutron diffraction instruments serve as gateways for structural studies.

BWAVES features and capabilities will include:

  • A dynamic range spanning 4.5 decades and covering energy transfers from ~0.010 meV to above 500 meV.
  • The capability to characterize relaxational excitations gradually emerging as a function of temperature, or other thermodynamic variables, to efficiently decipher complex dynamic landscapes.
  • A small beam size to study very small samples (a few microliters in volume) and facilitate the use of small, advanced sample environment equipment.
  • A unique open-tabletop sample geometry to provide easy access to the sample when applying multimodal external stimuli, including default optical access to the sample.
  • A novel WAVES rotor and capability to integrate different sets of STS source characteristics, such as frequency, cold neutrons, high brightness, compact moderators.


BWAVES will be optimized for bioscience and chemical science, as well as for studying novel materials such as for energy applications, novel soft matter such as recyclable polymers, and for better understanding the biological processes in emerging biotechnologies and medical technologies. It will also enable measurements of both vibrational and relaxational excitations within the same continuous scattering spectra.


Table of standard operation parameters.

Energy resolution at the elastic line 0.020 meV, FWHM
Maximum energy transfer ~ 1000 meV
Inelastic energy resolution, ΔE/E 2.0-2.5% up to 60 meV; 3.0-4.5% up to 250 meV
Momentum transfer at the elastic line 0.2 Å-1 - 0.8 Å-1
Maximum momentum transfer ~ 20 Å-1
Momentum transfer resolution at the elastic line ~ 0.1 Å-1


“A concept of a broadband inverted geometry spectrometer for the Second Target Station at the Spallation Neutron Source”. E. Mamontov, C. Boone, M. J. Frost, K. W. Herwig, T. Huegle, J. Y. Y. Lin, B. McCormick, W. McHargue, A. D. Stoica, P. Torres, and W. Turner, Review of Scientific Instruments 93, 045101 (2022), doi: 10.1063/5.0086451