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

The RITA_II Instrument

Identification

• Site: PSI
• Author: Linda Udby and Peter Willendrup
• Origin: NBI, DTU Physics, Risø, PSI
• Date: 2012
• Version: $June 03 2011 $

Description

This instrument is model of RITA-II at the RNR13 guide at SINQ, PSI as of 2009. The energy and q-resolution as been verified against measured data in 2- and 3-axis modes. See Udby et al., Nuclear Instruments and Methods 634 (2011) s138-.

The model is based on the following components in downstream order

 The SINQ source in 2009 - tested up to Ei=15 meV versus measurements. The spectrum of genereated rays is controlled by the BPL and BPH parameters.
 The RNR13 guide with average m-value based on color-codes on guide pieces and gaps as measured/from technical drawings.
 The Druckal monochromator: 5 slabs of PG(002) with vertically focusing option. The horizontal rotation angle (A1) and  scattering angle (A2) can either be set by user input or calculated automatically from EI/KI. 
 Optional filter after the monochromator, before the sample. 
 Variable linear collimator after the monochromator, before the sample. 
 Optional perspex attenuation. 
 Inbound Diaphagm slit. 
 Sample: Incoherent scatterer, powder or single crystal from reflection list. 
 Outbound Diaphragm slit. 
 Optional filter after the sample, with radial collimator.
 9 - blade analyser: Base-rotation (AA5) and individual blade angles (C1-C9) can either be set by user or calculated automatically from EF/KF. 
 Coarse collimator: Removes cross-talk by allowing only passage of scattered neutrons from specified blade in each channel.
 Detector: PSD detector with 100% efficiency and specified point-spread function from measurements.
 Windows: Monitors the neutrons in each electronically specified window [XWinMin,XWinMax;YWinMin,YWinMax].

EXAMPLES

Generating a virtual source 
mcrun RITA-II.instr -n3e6  BPL=0.97 BPH=1.03 EI=5 EF=5 COLL_MS=40 SAMPLE=1 OUTFILTER=0 REP=10 VIRTUALOUT=1 -d  RITA-II_Vsource40 

Vanadium sample, no filters, seeing 1st-3rd order neutrons 
mcrun RITA-II.instr -n3e6 BPL=0.30 BPH=1.03 EI=5 EF=5 SAMPLE=1 INFILTER=0 OUTFILTER=0  REP=10 -d RITA-II_Vanadium 

Powder sample (default sapphire), simulation 1) through entire instrument or  2)from virtual source 3) in 2-axis mode, with particular slit settings scaling the source yield to 2008 values 
1) mcrun RITA-II.instr -n3e6 EF=5 EN=0 SAMPLE=2 COLL_MS=40 SAMPLEFILE="Al2O3_sapphire.lau" BARNS=0 SOURCEFILE="RITA-II_Vsource40/Vin_default.dat" REP=10 -d RITA-II_40_powder

2) mcrun RITA-II.instr EI=5 EF=5 SAMPLE=2 SAMPLEFILE="Al2O3_sapphire.lau" BARNS=0 SOURCEFILE="RITA-II_Vsource40/Vin_default.dat" VIRTUALIN=1 REP=3 -d RITA-II_VINsource40_powder 

3) mcrun RITA-II.instr -n 1e7 ITAR=0.71 COLL_MS=19.6 BPL=0.97 BPH=1.03 EI=5 EF=5 QH=0 QK=0 QL=0 QM=1 A3=0.001 A4=-71 AA5=-90 A6=1e-3 MST=25 MSB=25 MSL=10 MSR=10 SAMPLE=2 SAMPLEFILE="Al2O3_sapphire.lau" SST=25 SSB=25 SSL=10 SSR=10 OUTFILTER=0 OUTFILTERFILE=Be.trm COARSE=1 REP=5 LC=6 RC=4 REP=1 BARNS=0 ANAFORCE=1 -d RITA-II_Al2O3_2axis

Single crystal sample. Define first lattice vector (a) along -x (to the right) , second lattice vector (b) along z (forward), third lattice vector (c) along y (up). 
 mcrun RITA-II.instr -n1e6 BPL=0.97 BPH=1.03 EI=5 EF=5 SAMPLE=3 REP=10 QH=2 QM=0 AS=4.95 BS=4.95 CS=4.95 AAX=-4.95 BBZ=4.95 CCY=4.95 AH=0 AK=1 AL=0  BH=1 BK=0 BL=0 SAMPLEFILE="Pb.laz" -d RITA-II_SXPb200 

 Phonon sample, inelastic scattering, no Bragg peaks in sample 
mcrun RITA-II.instr -n1e6 L0=3.418 BPL=0.97 BPH=1.03 EI=7 EF=5 SAMPLE=4 REP=10 QH=2 QK=0.16 QM=0 AS=4.95 BS=4.95 CS=4.95 AAX=-4.95 BBZ=4.95 CCY=4.95 AH=0 AK=1 AL=0  BH=1 BK=0 BL=0 SAMPLEFILE="Pb.laz" -d RITA-II_SXPb200_2meV 

Input parameters

Links

• Download Source code for RITA_II.instr. (tar.gz file)
• Rescal for Matlab at http://www.ill.fr/tas/matlab
• Restrax at http://omega.ujf.cas.cz/restrax/

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