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

The SNS_BASIS Instrument

Written by: N.Tsapatsaris (nikolaos.tsapatsaris@esss.se) and Peter K. Wilendrup (pkwi@fysik.dtu.dk)

Identification

• Site: SNS
• Author: N.Tsapatsaris (nikolaos.tsapatsaris@esss.se) and Peter K. Wilendrup (pkwi@fysik.dtu.dk)
• Origin: NBI
• Date: 2013-2015

Description

ESCRIPTION
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 (ruep.lechner@gmail.com) and HNB (bordallo@nbi.ku.dk) with contributions
from Johan Jacobsen (johan.fett@gmail.com)
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.

Examples

(Test cases in bold)

• Test: mcrun BASIS_guide.instr Lam=6.4 Detector: Guide_end_PSD_I=8.1e+09

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

Links

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

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

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Last Modified: Friday, 11-Sep-2026 15:00:09 CEST