Guide hall, thermal beam H25
distance reactor-core to monochromator : 65 m
α0 = 12.λ (Å)
beam size LxH=5 x 4 cm2
vertically fixed and horizontally focusing
IN22 is a three-axis spectrometer equipped for full polarisation analysis. It is installed at the end position of the thermal supermiror guide H25.
Two different vertically focusing monochromators PG (002) and Heusler (111) are mounted on a carrousel (computer controlled), providing a high flux of unpolarised and polarised neutrons respectively together with a low intrinsic α0 divergence.
- The monochromator covers an angular range 16°< 2θM <80°.
- The sample covers an angular range -70°< 2θS <120°.
- The analyser covers an angular range -80°< 2θA <80°.
The sample, analyser and detector units are mounted on nonmagnetic ˝Tanzboden˝ modules with adjustable distances between them. The collimation between monochromator and sample, sample and analyser, analyser and detector can be changed between 10’ and ˝open˝. The sample table can support the mounting of high-field cryomagnets (up to 12T and 15T, respectively in the polarised and unpolarised modes).
IN22 can be operated alternately in the unpolarised or polarised mode. Vertical guide fields are permanently installed. The incident/final polarisation can be continuously selected in the three spatial directions by a system of three horizontal coils and a vertical Helmholtz pair, all computer controlled with respect to the scattering vector Q.
IN22 has been equipped with a new spherical polarisation analysis option, optimized for the inelastic neutron scattering of thermal neutrons. The use of large area vertically focusing monochromators (L(mm) x H(mm) = 140 x 120) and large size horizontally focusing Heusler analysers (L(mm) x H(mm) = 150 x 100) has allowed a substantial improvement of the polarised neutron intensity in the detector. A typical value for the intensity ratio at 2.662 Å-1 with PG (002) monochromator and analyser versus Heusler-Heusler configuration is 6 (open collimation). Typical flipping ratios in real experimental conditions are 20 at 2.662 Å-1 and 18 at 4.1 Å-1.