Fixed-Incident-Energy Triple-Axis Spectrometer


Mission Statement

HB-1A is a powerful instrument for diffraction studies of magnetic materials, particularly in cases where the signal is very weak and/or extreme sample environments are required.

Instrument Description

The HB-1A Triple-Axis-Spectrometer (FIE-TAX) at the High Flux Isotope Reactor operates at a fixed incident energy of Ei = 14.5 meV (wavelength λ = 2.37 Å) by employing a double-bounce pyrolytic graphite monochromator system. The first monochromator unit is flat, while the second monochromator unit is vertically focused. A highly-oriented pyrolytic graphite filter is mounted after each monochromator to reduce λ/2 contamination. This setup provides HB-1A with a very clean beam nearly free of higher-order contamination neutrons. This setup, combined with the use of an analyzer for energy discrimination, ensures that HB-1A has an excellent signal-to-noise ratio for magnetic diffraction studies. It can also accommodate a wide variety of sample environments, including high temperature furnaces (≤ 1770 K), ultra-low temperature cryostats (≥ 0.05K), vertical field cryomagnets (≤ 8T), pressure cells (≤ 2GPa), and electric field sticks (≤ 10kV).


HB-1A is used for neutron diffraction experiments in disciplines such as hard condensed matter science, chemistry, materials science, and nanotechnology. This instrument is exceptional for parametric magnetic diffraction studies of powders, single crystals (mm-sized or larger), and thin films (thickness > 50 nm). Most experiments performed on HB-1A focus on quantum materials research, with a particular emphasis on high-temperature superconductors, multiferroics, heavy transition metal magnets, and frustrated magnets. These materials are often used in devices like sensors, magnetic recording (hard drives), filters, smart phones, power transmission lines, and could help enable the creation of a quantum computer.


Beam Spectrum Thermal
Monochromator PG(002) crystal
Monochromator angle 2Θ M = 41.3° Ei = 14.5 meV
Analyzers PG(002) Be(101) Be(002) Si(111)
Sample angles


Scattering angle -5 to 130°
Analyzer angles -60° < 2ΘA < 120°
Collimations Premonochromator: 40′
Monochromator-sample: 10′, 20′, 40′
Sample-analyzer: 10′, 20′, 40′, 60′, 80′ 
Analyzer-detector: 20′, 60′, 80′, 240′
Filters Sapphire pre-monochromator
2 HOPG (λ / 2 ≈ 10-4λ) located between
M-1 and M-2 and after M-2
Flux at sample ~4.2 × 107 n/cm2/s
Momentum range 0.2 to 4.8 Å-1 (elastic configuration)