BASISReduction v1¶

BASISReduction dialog.

Table of Contents

Summary
Properties
Description
Usage
Source
Workflow

Summary ¶

Multiple-file BASIS reduction for its two reflections.

Properties ¶

Name	Direction	Type	Default	Description
RunNumbers	Input	string		Sample run numbers
DoIndividual	Input	boolean	False	Do each run individually
MonitorNorm	Input	boolean	True	Normalization with wavelength-dependent monitor counts
ExcludeTimeSegment	Input	string		Exclude a contigous time segment; Examples: “71546:0-60” filter run 71546 from start to 60 seconds, “71546:300-600”, “71546:120-end” from 120s to the end of the run
GroupDetectors	Input	string	None	Switch for grouping detectors. Allowed values: [‘None’, ‘Low-Resolution’, ‘By-Tube’]
NormalizeToFirst	Input	boolean	False	Normalize spectra to intensity of spectrum with lowest Q?
ReflectionType	Input	string	silicon_111	Analyzer. Documentation lists typical associated property values. Allowed values: [‘silicon_111’, ‘silicon_311’, ‘silicon_333’]
EnergyBins	Input	dbl list	-150,0.4,500	Energy transfer binning scheme (in ueV)
MomentumTransferBins	Input	dbl list	0.3,0.2,1.9	Momentum transfer binning scheme
MaskFile	Input	string		See documentation for latest mask files. Allowed extensions: [‘.xml’]
DivideByVanadium	Input	boolean	False	Do we normalize by the vanadium intensity?
NormalizationType	Input	string	by Q slice	Select a Vanadium normalization. Allowed values: [‘by Q slice’, ‘by detector ID’]
NormRunNumbers	Input	string		Normalization run numbers
SaveNXSPE	Input	boolean	False	Do we save to NXSPE format?
PsiAngleLog	Input	string	SE50Rot	name of entry in the logs storing the psi angle
PsiOffset	Input	number	0	add this quantity to the psi angle stored in the log
OutputSusceptibility	Input	boolean	False	Output dynamic susceptibility (Xqw)

For each property, the algorithm will remember the last value used. If user deletes this value and leaves blank the property field, the default value will be used. Default values are typical of the silicon111 reflection.

Description ¶

Run numbers: The syntax for the run numbers designation allows runs to be segregated into sets. The semicolon symbol ”;” is used to separate the runs into sets. Runs within each set are jointly reduced.

Examples:

2144-2147,2149,2156 is a single set. All runs jointly reduced.
2144-2147,2149;2156 is set 2144-2147,2149 and set 2156. The sets are reduced separately from each other.

If DoIndividual is checked, then each run number is reduced separately from the rest. The semicolon symbol is ignored.

ExcludeTimeSegment: Events happening in a time segment with no proton charge are most likely noise. Those events can be filtered out of the reduction process.

Example:

“71465:0-500;71466:900-2100;71467:4000-end” will filter out events happening between the start of the run and 500 seconds for run 71465, then between 900 and 2100 seconds for run 71466 and between 4000 seconds and the end of the run for 71467. Only one time segment can be excluded per run number.

Momentum transfer binning scheme: Three values are required, the center of the bin with the minimum momentum, the bin width, and the center of the bin with the maximum momentum.

Rescaling to first spectrum: Since the Y-scale has arbitrary units, a rescaling convention is taken whereby the maximum of the first spectrum (lowest Q-value) is rescaled to 1.0. This rescaling may not be employed when the intent is to compare to other runs, like can substraction of comparison between deuterated and hydrogenated samples.

Reflection Selector ¶

Currently three types of reflection are possible, associated with the silicon analyzers of BASIS. These are typical binning values for each reflection:

Reflection	Energy bins (micro-eV)	Momentum transfer bins (inverse Angstroms)
silicon111	-150, 0.4, 500	0.3, 0.2, 1.9
silicon311	-740, 1.6, 740	0.5, 0.2, 3.7
silicon333	-1500, 3.2 1500	0.5, 0.2, 3.7

Also the following default mask files are associated to each reflection:

Reflection	Mask file
silicon111	BASIS_Mask_default_111.xml
silicon311	BASIS_Mask_default_311.xml
silicon333	BASIS_Mask_default_333.xml

Note: masks for reflections 111 and 333 are actually the same since both reflections take place at the same silicon crystal analyzers.

These mask files can be found in the SNS filesystem (/SNS/BSS/shared/autoreduce/new_masks_08_12_2015/)

Vanadium Normalization ¶

The syntax for the vanadium run numbers designation (NormRunNumbers) is the same as in the case of the sample (hyphens and commas are understood) but no semicolons are allowed. As a result, only one set of vanadium run numbers is generated, and all runs are jointly reduced into a single vanadium workspace. Thus, if we had entered three sets of sample run numbers, then three reduced workspaces will be produced and all will be divided by the same vanadium workspace.

Normalization type by Q slice is the default normalization. In this case, the sample is reduced into $S_{s}(Q,E)$ and the vanadium is reduced into $S_{v}(Q,E)$ . Later, $S_{v}(Q,E)$ is integrated along the energy axis in the range [-0.034, 0.034]meV to produce $S_{v}(Q)$ . Finally the sample is divided by the vanadium, $S_{s}(Q,E) / S_{v}(Q)$ .

Normalization type by detector ID carries out the division on each detector of the instrument. If we have for detector $i$ sample $S_s(\lambda, i)$ and vanadium $S_v(\lambda, i)$ , we integrate along the $\lambda$ axis in the range given by NormWavelengthRange to obtain $S_v(i)$ and then divide $S_s(\lambda, i)/S_v(i)=S'_s(\lambda, i)$ . From this point on, the reduction process continues using $S'_s$ in place of $S_s$ .

Saving NXSPE files ¶

NXSPE files are suitable for intensity visualization in $\vec{Q}$ space with [MSLICE](http://mslice.isis.rl.ac.uk/Main_Page). When using this program, make sure you select the inverse geometry.

Also, make sure that the sample rotation angle is stored in the logs of the run, since this is a required property of the algorithm.

Dynamic Susceptibility ¶

If <i>OutputSusceptibility</i> is checked, one additional workspace and one Nexus file will be generated, both containing the dynamic susceptibility as a function of frequency, in units of GHz. The extension denoting this quantity in the workspace and file names is “Xqw” (the extension for the structure factor is “sqw”).

Usage ¶

Perform a reduction:

BASISReduction(RunNumbers="59671",
               EnergyBins=[-120,0.4,120],
               MomentumTransferBins=[0.3, 0.2, 1.9],
               DivideByVanadium=1,
               NormRunNumbers="58183")

Categories: Algorithm Index | Inelastic\Reduction

Source ¶

Python: BASISReduction.py (last modified: 2019-03-12)

Workflow ¶