Mission Statement

Probing the dynamic response of solids with tailorable resolution and high neutron flux.

Instrument Description

Using Bragg’s Law, a triple-axis spectrometer selects the wavelengths of neutrons before and after they hit the sample, which directly probes the energy and momentum response of various materials. HB3 provides a very high neutron flux thanks to its location directly at the end of the beam tube that is situated slightly away from the tangential path toward the reactor core. The beam diameter of the effective source that illuminates the monochromator is 4.625 inches. A sapphire filter is placed before the monochromator to reduce epithermal neutrons. Inside the drum there are 3 monochromators mounted on a unit. They are pyrolytic graphite (PG), silicon, and beryllium each of which is equipped with vertical focusing device that keeps the beam height at 1 inch over a wide range of incident energies at the sample position.

PG (002) provides the highest neutron intensity because it has a high neutron reflectivity. The unique high-quality Be (002) monochromator extends the energy range and provides good energy resolution at high energy transfers. Si(111) crystals have the advantage that there is no second-order reflection, thus providing a clean beam. The availability of these three monochromator crystal choices makes this spectrometer extremely versatile for a wide range of studies.

The momentum and energy resolution can be further defined by changing the horizontal divergence of the beam through Söller collimators. The in-pile collimation can be reduced from its intrinsic value of 48' to a user-selectable value of 30' at the push of a button via the shutter control panel. Collimators from the monochromator-sample, the sample-analyzer, and the analyzer-detector can be changed manually. The PG analyzer has a fixed vertical focusing optimized for the final energy of 14.7 meV. The single 3He detector is tall enough for the choice of various other final energies too.


The availability of three monochromator crystals makes HB-3 a versatile instrument for studies of excitations in materials with energies ranging from 1 to 120 meV. Typical applications include lattice dynamics such as phonon anharmonicity and electron-phonon coupling; spin dynamics such as spin waves in magnetically ordered systems, crystal field excitations, magnetic excitations in low-dimensional magnetic model systems; spin fluctuations in unconventional superconductors and other novel quantum materials. The high incident neutron flux makes HB-3 well suited to studying samples with a small volume or weak scattering characteristics. Recent mreasureements on HB3 have included high-temperature superconductors, multiferroics,  thermoelectics, low-dimensional magnetic model systems and potential quantum spin liquid materials.


Beam Spectrum: Thermal
Monochromators: Variable vertical focusing PG(002), Be(101), Si(111)
Analyzer: Fixed veritcally focused PG(002), Si(111), Be(101)
Monochromator angle: 12 – 88°
Sample angle: +/- 180°
Scattering angle -90° – 120°
Analyzer angle: -40 – 90°
Collimations (FWHM): Premonochromator: 30', 48'
Monochromator-sample: 20', 40', 60', 80'
Sample-analyzer: 20', 40', 60', 80'
Analyzer-detector: 30', 70', 90', 120', 210', 240'