[ Identification | Description | Input parameters | Links ]

The `RITA_II` Instrument

RITA type triple-axis spectrometer (TAS)

Identification

Site: PSI
Author: Linda Udby and Peter Willendrup
Origin: Risø (Denmark)
Date: 2012

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

Parameters in boldface are required; the others are optional.

Name	Unit	Description	Default
ITAR	mA	Relative neutron yield from the spallation target. Value relative to 2009	1.0
L0	Angs	Centre of generated wavelength distribution from source	4.045
BPL		Band Pass Low factor, multiplied on source wavelength L0 to allow neutrons with wavelengths with lambda {BPLL0,BPHL0} to be traced from the source.	0.97
BPH		Band Pass High factor, multiplied on source wavelength L0 to allow neutrons with wavelengths with lambda {BPLL0,BPHL0} to be traced from the source.	1.03
MONO_N	1	Order of reflection used on mono	1
MONOFORCE	1	If set, monochromator is flat	0
MONO_MOS_H	min	Monochromator, horizontal mosaicity	37
MONO_MOS_V	min	Monochromator, vertical mosaicity	37
EI	meV	Incoming neutron energy. Also used to set range of energy monitors	0
EF	meV	Outgoing neutron energy. Also used to set range of energy monitors	0
EN	meV	Energy transferred in crystal	0
SM	1		1
SS	1	Scattering configuration signs. 'W' is SM=1,SS=-1,SA=1	-1
SA	1		1
QH	rlu	Measurement QH position in crystal	0
QK	rlu	Measurement QK position in crystal	0
QL	rlu	Measurement QL position in crystal	0
QM	Angs-1	Wavevector transferred in sample, use QM=0 if (QH,QK,QL) is specified	1.8051
AS	Angs	Sample lattice parameter A	4.95
BS	Angs	Sample lattice parameter B	4.95
CS	Angs	Sample lattice parameter C	4.95
AA	deg	Angle between lattice vectors B,C	90
BB	deg	Angle between lattice vectors C,A	90
CC	deg	Angle between lattice vectors A,B	90
AH	rlu	First reciprocal lattice vector in scattering plane, X	0
AK	rlu	First reciprocal lattice vector in scattering plane, Y	1
AL	rlu	First reciprocal lattice vector in scattering plane, Z	0
BH	rlu	Second reciprocal lattice vector in scattering plane, X	1
BK	rlu	Second reciprocal lattice vector in scattering plane, Y	0
BL	rlu	Second reciprocal lattice vector in scattering plane, Z	0
INFILTER	1	Flag to indicate if mono-block filter is in or out	0
INFILTERFILE	string	An input file of wavevector vs transmission to use with incoming filter	"Be.trm"
COLL_MS	deg	Primary collimator max divergence	80
MST	m	Monochromator TOP slit	40
MSB	m	Monochromator BOTTOM slit	40
MSL	m	Monochromator LEFT slit	40
MSR	m	Monochromator RIGHT slit	40
PTHICK	m	Thickness of perspex attenuator	1e-3
PERSPEX	1	Flag to indicate if perspex attenuator is in or out	0
SAMPLE	1	1 is incoherent scatterer, 2 is powder, 3 is single crystal.	1
SAMPLEFILE	string	Name of samplefile (with reflectionlist etc)	"default"
MOS		Isotropic 'mosaicity' of single crystal	100
DD_D		spead of lattice parameter	1e-3
SAMPLESIZE	m	Length, height and width of single crystal sample, or radius and height of phonon sample	0.01
BARNS	1	If set the flag indicates that reflection list structure factors are in units of barns, otherwise fm^2	1
AAX			-4.95
AAY		Orientation vector of unit cell, single_crystal	0
AAZ			0
BBX			0
BBY		Orientation vector of unit cell, single_crystal	0
BBZ			4.95
CCX			0
CCY		Orientation vector of unit cell, single_crystal	4.95
CCZ			0
A1	deg	Monohromator rotation angle	0
A2	deg	Monohromator take-off angle	0
A3	deg	Sample rotation angle	0
A4	deg	Sample take-off angle	0
A6	deg	Analyzer take-off angle	0
TILT	deg	Tilt angle out of plane of the sample scattering vector out of plane (rotation around z of the A3 arm)	0
SST	m	Sample TOP slit	100
SSB	m	Sample BOTTOM slit	100
SSL	m	Sample LEFT slit	100
SSR	m	Sample RIGHT slit	100
OUTFILTER	1	Flag to indicate if the outbound filter is in or out	1
OUTFILTERFILE	string	An input file of wavevector vs transmission to use with outgoing filter	"Be.trm"
ANAFORCE	1	If set the analyzer is forced flat	0
AA5	deg	Analyzer rack rotation angle	0
C1	deg	Analyzer blade 1 position	0
C2	deg	Analyzer blade 2 position	0
C3	deg	Analyzer blade 3 position	0
C4	deg	Analyzer blade 4 position	0
C5	deg	Analyzer blade 5 position	0
C6	deg	Analyzer blade 6 position	0
C7	deg	Analyzer blade 7 position	0
C8	deg	Analyzer blade 8 position	0
C9	deg	Analyzer blade 9 position	0
COARSE	1	Flag to indicate if Detector collimator is in or out	1
LC	deg	Detector-collimator angle of the leftmost blade	4
RC	deg	Detector-collimator angle of the rightmost blade	3
REP	1	Repetition factor of virtual_input or Monochromator/Sample/Analyzer SPLITs	1
VIRTUALOUT	1	If set, flag indicates that a Virtual source is created after the monochromator collimator	0
VIRTUALIN	1	If set, flag to indicates that Virtual source is used after the monochromator collimator	0
SOURCEFILE	string	Name of file to be used/genereated as virtual input/output	"Vin_default.dat"
verbose	1	print TAS configuration. 0 to be quiet	1

The RITA_II Instrument

Identification

Description

Input parameters

Links

The `RITA_II` Instrument