Guide hall n°1, cold guide H144
115 m from the vertical cold source
PG (002); d = 3.355 Å
transmission polariser (cavity, guide changer 35m in front of guide end)
2 - 6 Å
> 95 %
20 - 27 (depending on energy)
Double focusing set up
horizontal divergence at sample position: 2-3o;
Gadolinium coated Soller collimators with divergences of 10', 20', 30', 40', 60', 80' can be placed before sample, analyser, and detector
vertically mounted 12 cm high, 5 cm Ø
The monochromator of IN12 is a set of horizontally and vertically focussing pyrolytic graphite (002) crystals, which deliver the following incident wavelengths, energies, and wavevectors:
- 1.26 < λ/Å < 6.3
- 2.1 < Ei/meV < 42
- 1.0 < ki/Å-1 < 5.0
Measurements with a calibrated monitor at the sample position show for a typical wavevector of ki=2Å-1 a flux of about:
- double focusing set up: 1.04 x 108 n cm-2 s-1
- velocity selector in: 8.4 x 107 n cm-2 s-1
- velocity selector, 60' collimation: 5.02 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 2.5 Å. At longer wavelengths a velocity selector placed far upstream in the guide is 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 -10°< 2θM < -140°.
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.
In double focusing set up the resolution results to 150 µeV (FWHM) for an incident wavevector of ki=1.5Å-1.