BASISReduction v1¶

BASISReduction dialog.

Table of Contents

Summary
Properties
Description
- Reflection Selector
- Vanadium Normalization
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
NoMonitorNorm	Input	boolean	False	Stop monitor normalization
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	silicon111	Analyzer. Documentation lists typical associated property values. Allowed values: [‘silicon111’, ‘silicon311’]
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	/SNS/BSS/shared/autoreduce/new_masks_08_12_2015/BASIS_Mask_ThreeQuartersRemain_SouthTop_NorthTop_NorthBottom_MorePixelsEliminated_08122015.xml	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
NormWavelengthRange	Input	dbl list	6.24,6.3	Wavelength range for normalization

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.

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 two types of reflection are possible, associated with the two analyzers of BASIS. There are typical values for the properties of 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

Also the following mask files are associated to each reflection:

Reflection	Mask file
silicon111	BASIS_Mask_ThreeQuartersRemain_SouthTop_NorthTop_NorthBottom_MorePixelsEliminated_08122015.xml
silicon311	BASIS_Mask_OneQuarterRemains_SouthBottom.xml

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 $S_s$ .