IN8
Thermal neutron three-axis spectrometer
Reactor hall, thermal beam H10 |
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Diameter of the “in-pile” beam tube extremity Ø = 170 mm |
Virtual source |
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Adjustable width: typically used 30 mm wide for PG and Cu monochromators, 25 mm wide for Si monochromators |
Distances | |||
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| Virtual source to monochromator: 2280 mm | |||
| Monochromator to sample: 2480 mm | |||
| Sample to analyser: 1050 mm | |||
| Analyser to Detector: 700 mm |
Monochromator | ||||||
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| Crystal | W x H (mm2) | ki/Å-1 | flux/108 n cm-2s-1 | |||
PG (002) varible double focusing, mosaic 30' | 290x200
| 2,662 4,1 | 6,8 10 | |||
Cu (200) variable double-focusing, anisotropic mosaic (h:25', v:10') | 290x200
| 4,1 7 | 5 3.2 | |||
Si (111) bent perfect crystals, variable double focussing | 230x200
| 2,662 4,1 | 3,3 4,8 | |||
Si (311) bent perfect crystals, variable double focussing | 230x200
| 4,1 7 | 3,3 4,8 | |||
Sample |
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From several cm3 to sub mm3 sizes. Single crystal or mosaics arrangements both used. |
Thermes spectrometer Analysers (interchangeable) | |
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| PG (002) variable double-focusing | active area: 180 mm x 140 mm (W x H) |
| Cu (200) variable double-focusing | active area: 180 mm x 140 mm (W x H) |
Si (111) bent perfect crystals, variable double-focusing | active area: 160 mm x 200 mm (W x H) |
Detector |
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Single 3He detector, vertically mounted. |
Multianalyser Flatcone Analysers | |
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| 31 Si111 bent perfect crystals, fixed curvature for kf=3 A-1 | active area 20 mm (W)x variable up to 60 mm (H) each |
Detector |
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31 Single 3He detectors, horizontally mounted |
Instrument description
IN8 is installed on beamtube H10 (diameter F = 170 mm).
The incident wavelength selection is obtained through a double focusing monochromator, which has four faces equipped with PG002, Cu200 mosaic and elastically bent perfect Si111 and Si311 crystals, respectively. Horizontal and vertical focusing allows increasing the monochromatic flux at the expense of momentum but not energy resolution with the horizontal virtual source (an adjustable entrance slit) is introduced before the monochromator at a distance which matches the monochromator-sample distance.
The aperture of the horizontal virtual source can be varied but is typically kept around or slightly below 30 mm. For high-resolution experiments using a horizontally flat monochromator and/or analyser the Soller slit collimators with enriched 10B isotope coatings are produced. They can be installed before and after the monochromator as well as before and after the analyser. The available openings are 20’, 30’ and 40’ with additional 60’ for the secondary spectrometer.
The primary beam shielding drum allows varying the monochromator take-off angle in the range 11° < 2θM < 90°. The secondary spectrometer Thermes has borated polyethylene shielding installed around the analyzer and detector units limiting the accessible dynamical range. The scattering angle at the sample position can be varied in the range 0° < 2θs < 120° in both positive or negative scattering directions. The detector block can reach angular positions in the 0° < 2θA < 90° range in both positive or negative scattering directions.
The instrument allows using a wide range of sample environment equipment such as high field magnets, high-temperature furnaces, high pressure equipment. For very small samples, a dedicated VacBox system with background slits put at minimal distance to the sample can be used to help increase signal-to-noise ratio.
IN8-Thermes can host two type of special optional setups.
Brillouin neutron scattering setup. For low scattering angle experiments (2θs > 0.5°) the sample to analyzer distance can be increased ( ~5 cm) to host an available vacuum box serving to reduce air scattering.
Incoherent inelastic neutron scattering. For IINS experiments with energy transfer up to 120 meV on hydrogen containing materials a polycrystal Be filter can be installed after the PG analyser with fixed final neutron energy of 4.5 meV.