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McStas: SNS_BASIS Instrument at SNS

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

The SNS_BASIS Instrument


  • Site: SNS
  • Author: N.Tsapatsaris ( and Peter K. Wilendrup (
  • Origin: NBI
  • Date: 2013-2015
  • Version:(Unknown)


The approximative, analytic SNS Source description of this instrument is realised 
by use of the ESS_moderator_short model, but weighted due to the opposite moderator
arrangement at the SNS and at the once-planned ESS short pluse facility. The correct
SNS Source File to use with SNS_Source is source_sct091_tu_02_1.dat.

The instrument serves as a test instrument for the components
Spherical_Backscattering_Analyser, also written by by Niko Tsapatsaris with help from
Peter Willendrup and Guide_m by Niko Tsapatsaris.

The instrument is based on models initially written by 
A) REL ( and HNB ( with contributions 
  from Johan Jacobsen (
B) G. Granroth

A virtual experiment on BASIS i.e. a comparison with real and simulation results were
published in AIP conference,DOI: 10.1051/epjconf/20158303015 and RSI, DOI: 10.1063/1.4961569

Instrument geometry parameters etc. were taken from the publication: 
"A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS" by
Mamontov, E.;   Herwig, K. W.; Neutron Scattering Science Division, Oak Ridge National Laboratory, 
Oak Ridge, Tennessee 37831, USA, in Review of Scientific Instruments,82(8),085109 - 085109-10, 2011

This simulation uses the sample component Isotropic_Sqw. We are using the description for a Vanadium 
hollow cylindrical sample. One Arm Component is used to place the Analyser Component at an angle 
defined as ROT1.

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
Lam AA Wavelength selected by the chopper system 6.4
Lambda_min AA Minimum wavelength produced at the source 5
Lambda_max AA Maximum wavelength produced at the source 7
RadCurv m Radius of Curvature of the guide system 1000
omega1 Hz Frequency of the first DiskChopper 60
omega2 Hz Frequency of the second DiskChopper 60
omega3 Hz Frequency of the third DiskChopper 60
ch1_open deg Angular opening of the first Diskchopper 51.4
ch2_open deg Angular opening of the second Diskchopper 57.6
ch3_open deg Angular opening of the third Diskchopper 171.1
ROT1 deg Positioning of central analyser wrt. the incoming beam, in the scattering plane 90
AN_ROT deg Out-of-plane rotation of analysers wrt. scattering plane 2
TOTAL_LENGTH m Total length of the guide system 84
dROT deg Positioning of neighbouring analysers wrt. central analyser 11


  • Source code for SNS_BASIS.instr.
  • A reference/HTML link for more information

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

Generated automatically by McDoc, Peter Willendrup <> / Wed Jan 12 15:13:21 2022

Last Modified: Wednesday, 12-Jan-2022 16:13:21 CET
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