[ Identification | Description | Input parameters | Links ]

# The `SNS_BASIS` Instrument

## 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.

## 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

[ Identification | Description | Input parameters | Links ]