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McStas: ILL_H13_IN20 Instrument at ILL

[ Identification | Description | Input parameters | Output parameters | Links ]

The ILL_H13_IN20 Instrument

Thermal neutron three-axis spectrometer IN20@ILL (unpolarized configuration)

Identification

Description

IN20 is installed at the H13 thermal beam tube (Phi 170 mm) in the reactor hall.

Both the primary and the secondary spectrometer employ a monochromatic
horizontal focusing geometry. A heavy input slit of an adjustable size, placed
in the casemate, serves as a virtual source, providing a large solid angle for
the monochromatic beam, while reducing, together with a sapphire filter window,
the fast neutron background. The neutron energy is selected either by a doubly
focusing polarizing Heusler 111 monochromator (230 x 150 mm2 w x h) or by an
unpolarised Si 111 monochromator (elastically bent crystals, 195 x 200 mm2 w x
h) free of higher-order contamination in the incident beam at wave-numbers ki >
3 Angs-1. The analysis of the energy and polarisation state of the scattered
neutrons is effectuated by a similar horizontally focusing Heusler crystal
analyzer. Further PG 002 and Si 111 analyzers are available for occasional
unpolarised work.

The energy transfer range accessible in the present configuration of IN20
extends to 100 meV with maximum incident neutron energies reaching 150 meV. The
typical energy widths (FWHM) measured with a reference vanadium sample at the
graphite filter wave-numbers ki = 2.66 A-1 and 4.1 A-1 are 0.82(3) meV and 3.05
(15) meV, respectively.

This model uses two Si111 monochromator and analyzers (unpolarized
configuration).


Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
KF Angs-1 Outgoing neutron wavevector 3
KI Angs-1 Incoming neutron wavevector 0
QM Angs-1 Wavevector transfer in crystal 0.5
EN meV Energy transfer in crystal 0
verbose 1 print TAS configuration. 0 to be quiet 1
WM m Width of monochromator 0.20
HM m Height of monochromator 0.19
RMH m Monochromator horizontal curvature, 0 for flat, -1 for automatic setting -1
RMV m Monochromator vertical curvature, 0 for flat, -1 for automatic setting -1
DM Angs Monochromator d-spacing 3.155
NHM 1 Number of horizontal slabs composing the monochromator 15
NVM 1 Number of vertical slabs composing the monochromator 15
WA m Width of analyzer 0.16
HA m Height of analyzer 0.08
RAH m Analyzer horizontal curvature, 0 for flat, -1 for automatic setting -1
RAV m Analyzer vertical curvature, 0 for flat, -1 for automatic setting -1
DA Angs Analyzer d-spacing 3.155
NHA 1 Number of horizontal slabs composing the analyzer 15
NVA 1 Number of vertical slabs composing the analyzer 15
L1 m Source-Monochromator distance. Contains 1st Collimator of length 5.34 2.33
ALF1 arc min Horizontal collimation from Source to Monochromator 60
ALF2 arc min Horizontal collimation from Monochromator to Sample A 60
ALF3 arc min Horizontal collimation from Sample to Analyzer 60
ALF4 arc min Horizontal collimation from Analyzer to Detector 60
BET1 arc min Vertical collimation from Source to Monochromator 120
BET2 arc min Vertical collimation from Monochromator to Sample A 120
BET3 arc min Vertical collimation from Sample to Analyzer 120
BET4 arc min Vertical collimation from Analyzer to Detector 120

Links

  • Source code for ILL_H13_IN20.instr.
  • Rescal for Matlab at http://www.ill.eu/instruments-support/computing-for-science/cs-software/all-software/matlab-ill/
  • Restrax at http://omega.ujf.cas.cz/restrax/

[ Identification | Description | Input parameters | Output parameters | Links ]

Generated automatically by McDoc, Peter Willendrup <peter.willendrup@risoe.dk> / Mon May 29 08:29:50 2017


Last Modified: Monday, 29-May-2017 10:29:50 CEST
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