Polarized Direct-Geometry Chopper Spectrometer (Under Design)

CHESS |  ST-17 | STS

Instrument Description

CHESS will be a direct-geometry neutron spectrometer designed to detect and analyze weak signals intrinsic to small cross-sections, such as small mass, small magnetic moments or neutron absorbing materials. The instrument will be optimized to enable studies on quantum materials, spin liquids, thermoelectrics, battery materials, superconductors, and liquids.

CHESS will be the spectrometer of choice for initial exploration of new materials. Its broad dynamic range will also be well suited for measuring relaxation processes and excitations in soft and biological matter.

15 Hz repetition rate of the Second Target Station (STS) will allow using the Repetition Rate Multiplication technique (RRM), which greatly expands the information that can be gained in a single measurement. CHESS will also be designed to employ XYZ polarization analysis.

Applications

  • Collective excitations in single crystals and powder materials such as spin waves, phonons, and unconventional responses
  • Exotic ground states in quantum, frustrated, itinerant, and disordered magnets
  • Unconventional superconductors, non-Fermi liquids, and quantum criticality
  • Molecular magnetism and molecular spin
  • Liquids and complex fluids, such as dilute protein solutions, biological gels, and selective absorption of molecules on surfaces
  • Dynamics in confined geometries

Specifications

Beam spectrum Cold neutrons
Moderator Tubular Coupled Para-Hydrogen (20 K)
Beam size at sample Round, variable: Ø = 0.1-2 cm
Detector solid angle coverage Ω~2π sr
Incident energy range (ΔE)

0.2 ≤ Ei/meV ≤ 80 (1 ≤ l/Å ≤ 20)

(RRM capable)
Incident energies per pulse 1 - 8 using RRM mode
Energy transfer resolution at the elastic line (δE/E) 2%-5% Ei flexible
Total bandwidth  (Δλ) 7-8 Å
Q-range (ΔQ) 0.025 ≤ Q-1 ≤ 10
Q-resolution (δQ/Q) 2% – 5%
Polarization Polarized beam and XYZ polarization analysis
Beam divergence at sample Wavelength independent: FWHM=2.0°
Moderator to M-chopper (L1) 30 m
M-chopper to sample (L2) 1.5 m
Sample to detector (L3) 2.5 m
Detector type 3He tubes, 8-pack

Publications

Conceptual design of CHESS, a new direct-geometry inelastic neutron spectrometer dedicated to studying small samples”. J. Appl. Cryst. (2018). 51, 282–293. 

CHESS: The future direct geometry spectrometer at Second Target StationReview of Scientific Instruments 93, 065109 (2022)