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Fixed-Incident-Energy Triple-Axis Spectrometer
(HB-1A)
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HB-1A Fact sheet (pdf) |
| Beam
Spectrum: |
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Thermal |
| Monochromator: |
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PG(002)
double crystal |
| Monochromator
angle: |
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2Θ M = 41.3° Ei = 14.64 meV |
| Analyzers: |
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PG(002)
Be(101) Be(002) Si(111) Ge(111) |
| Sample angles: |
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0°
< Ψ < 360° |
| Scattering angle: |
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-15°
< Φ < 140° |
| Analyzer
angles: |
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-60°
< 2ΘA < 120° |
| Collimations
(FWHM): |
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C1:
open (48' effective) |
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C2:
open (40' effective) (30', 20', 10') |
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C3: 40',
30', 20',10' (sample-analyzer) |
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C4: 34',
68', 136' (analyzer-detector) |
| Beam
Size: |
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40
X 150 mm max |
| Filters: |
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Sapphire
pre-Monochromator-1
HOPG ( /2
 10-4
) located
between
M-1 and M-2 and after M-2 |
| Flux
at sample: |
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~2
X 107 n/cm2/s (est.) |
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HB1A is a fixed incident energy (14.6 meV) triple-axis spectrometer, using a double pyrolitic graphite monochromator system. The first monochromator is vertically focused and the second can be either a vertically or a double focused unit. Two HOPG filters, one after each monochromator, are used to reduce λ/2 contamination. These filters, together with the double monochromator system, provide HB1A with an exceptionally clean beam in terms of higher order contamination neutrons; Iλ/2 ≈ 10-4 x Iλ/2.
HB1A also has one of the most intense
beams at this energy at the HFIR, as
well as a very low γ and fast neutron
background. Typical energy resolution
is ~1 meV but by using the Be analyzer
the energy resolution width can be
reduced to ~0.5 meV.
HB1A development and operation is a collaborative effort of the ORNL and Ames Laboratory neutron scattering groups.
Applications
- Excitation spectra to ~35 meV using neutron energy gain, and low-lying excitations, 1-9 meV, using neutron energy loss.
- Elastic studies on crystallographic and magnetic structures and transitions in a q range of 0.2 to 4.9 Å-1.
- Elastic studies and excitations in thin films and other small volume samples where high flux and very low higher-order contamination of the beam are critical.
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Recent experiments on HB1A include measurement of phonon dispersion curves in martensitic, shape-memory and magnetostrictive alloys, crystallographic and magnetic structure determinations in giant magnetocaloric, magnetoresistive and intermetallic alloys, magnetic structures and spin-density waves in thin films, magnetism in low-dimensional systems and spin waves and magnetic structures in magnetoelectric materials. |
HB-1A Triple-Axis Spectrometer. Click image for a larger view.
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