guide hall n°1, cold guide H142 (instrument currently being moved to H144)
| 108 m from the source
beam dimensions 12 x 3 cm2 | Monochromator | PG (002); d = 3.355 Å
height x width: 12 x 8 cm2
with variable vertical curvature | Polariser | supermirror bender | aperture | 4.5 x 3.7 cm2 | polarization | > 95 % | transmission (for correct spin state): | 50-60 % (depending on energy) | Analyser | PG (002)
(with variable horizontal curvature; 12.2 x 11.8 cm2)
for polarization analysis: Heusler (111)
(d = 3.44 Å; 7.5 x 7.5 cm2) | |
Collimation | guide: α1 = 52/ki (min Å-1); | Gadolinium coated Soller collimators with divergences of 10', 20', 30', 40', 60' can be placed before sample, analyser, and detector | 3He detector | vertically mounted 12 cm high, 5 cm Ø |
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Warning This page is outdated since the instrument is currently being moved to the end of the cold neutron guide H144. This will provide a significant improvement of the characteristics of the instrument.
The monochromator of IN12 is a set of vertically focussing pyrolytic graphite (002) crystals, which can produce the following incident wavelengths, energies, and wavevectors: 2.3 < λ/Å < 6.0
2.3 < Ei/meV < 14
1.05 < ki/Å-1 < 2.6
The gain in flux over thermal neutron instruments is greatest for wavelengths longer than 3.5 Å : with Be-filter for Ei = 4 meV and
- 30' collimation: 7.4 x 106 n cm-2 s-1;
- 60' collimation: 1.0 x 107 n cm-2 s-1.
Due to the double curvature of the neutron guide there is little λ/2 contamination for wavelengths shorter than 4 Å. At longer wavelengths a liquid nitrogen cooled beryllium filter of 10 cm length may be used as a filter.
The sample is mounted on a motorized, non-magnetic goniometer which may achieve tilts of ± 20°. Two analysers are available: PG (002) for unpolarized work; and a Heusler (111) for polarization analysis.
For use with polarized neutrons a supermirror bender can be mounted after the first collimator to polarize the incident beam. A curved Heusler (111) analyser replaces the normal analyser. A small field (< 15 Oe; magnitude and direction computer controlled) may be imposed at the sample position using a system of coils or a super-conducting magnet can be used to produce larger fields.
The monochromator covers an angular range of 15°< 2θM < 90°.
The sample covers an angular range of -120° < 2θS < 120°.
The analyser covers an angular range of -140° < 2θA < 140°.
The energy resolution with 30' collimation is 22; 75; and 110 µeV (FWHM) for incident energies of 2.3; 4; and 5 meV, respectively.
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