ConvertHFIRSCDtoMDE v1#

Summary#

Convert from the detector vs scan index MDHistoWorkspace into a MDEventWorkspace with units in Q_sample.

Properties#

Name	Direction	Type	Default	Description
InputWorkspace	Input	`Workspace`	Mandatory	A detector-space MDHistoWorkspace, or a WorkspaceGroup of them from the same instrument.
Wavelength	Input	dbl list		Fallback incident wavelength, in Angstrom. As in HB3AAdjustSampleNorm, the ‘wavelength’ sample log of each input workspace is used when present, and this value only when the log is missing. Give one value for all inputs, or, for a WorkspaceGroup, one value per member in group order.
LorentzCorrection	Input	boolean	False	Correct the weights of events or signals and errors transformed into reciprocal space by multiplying them by the Lorentz multiplier: \(sin(2\theta)cos(\phi)/\lambda^3\)
MinValues	Input	dbl list	-10,-10,-10	It has to be 3 comma separated values, one for each dimension in q_sample.Values smaller then specified here will not be added to workspace.
MaxValues	Input	dbl list	10,10,10	A list of the same size and the same units as MinValues list. Values higher or equal to the specified by this list will be ignored
SplitInto	Input	int list	5	A comma separated list of into how many sub-grid elements each dimension should split; or just one to split into the same number for all dimensions. Default 5.
SplitThreshold	Input	number	1000	How many events in a box before it should be split. Default 1000.
MaxRecursionDepth	Input	number	20	How many levels of box splitting recursion are allowed. The smallest box will have each side length \(l = (extents) / (SplitInto^{MaxRecursionDepth}).\) Default 20.
ObliquityParallaxCoefficient	Input	number	1	Geometrical correction for shift in vertical beam position due to wide beam.
OutputWorkspace	Output	`Workspace`	Mandatory	An MDEventWorkspace in Q-sample. For a WorkspaceGroup input, a WorkspaceGroup whose members are named <OutputWorkspace>_<input member name>, as in HB3AAdjustSampleNorm, or a single MDEventWorkspace if MergeInputs is set.
MergeInputs	Input	boolean	False	For a WorkspaceGroup input, merge the converted members into one MDEventWorkspace with MergeMD, using the box controller settings given here. Ignored for a single input workspace.

Description#

This algorithm will convert the output of LoadWANDSCD v1 or the autoreduced data from DEMAND (HB3A) into a MDEventWorkspace in Q-sample, where every pixel at every scan point is converted to a MDEvent. This is similar to ConvertWANDSCDtoQ v1 except that it doesn’t histogram the data or do normalization. FindPeaksMD v1 can be run on the output Q sample space, then the UB can be found and used to then convert to HKL using ConvertWANDSCDtoQ v1 . IntegratePeaksMD v2 will also work on the output of this algorithm.

There is an option to apply the LorentzCorrection using the formula \(|\sin(2\theta)\cos(\phi)|/\lambda^3\). This helps lower the sloping background at low \(Q\).

Wavelength#

The incident wavelength of each input workspace is resolved in the same order as in HB3AAdjustSampleNorm v1:

the wavelength sample log of the input workspace, when present. A numeric or string log is accepted, and the mean is used for a time series log;
otherwise, the value given in the Wavelength property;
otherwise, the algorithm stops with an error.

The Wavelength property therefore acts as a fallback. For a single input workspace, give at most one value. For a WorkspaceGroup, give either one value, used for every member that has no wavelength sample log, or one value per member, in group order. When a wavelength sample log is present and differs from the value given in the Wavelength property, the property value is ignored and a warning is logged. The resolved wavelength is stored in the wavelength sample log of the output.

Grouped input#

InputWorkspace can also be a WorkspaceGroup of detector-space MDHistoWorkspaces, such as the output of HB3AAdjustSampleNorm v1 with OutputType="Detector" for several scans. All members must come from the same instrument; they may have different numbers of scan points. Each member is converted independently, with its own goniometer settings and wavelength. Every member is validated before any conversion starts, and an error names the member that caused it.

With MergeInputs=False (the default), the output is a WorkspaceGroup of MDEventWorkspaces in the order of the input group. Each member is named <OutputWorkspace>_<input member name>, following the convention of HB3AAdjustSampleNorm v1. A member of an input group that has no name is identified by its position, starting at 1. These names are given only when the algorithm stores its output in the Analysis Data Service, as when it is run from Python or the GUI. When it is run as a child algorithm, the members are not named; if the output group is later added to the Analysis Data Service, its members get the default names of a WorkspaceGroup, such as <group name>_1.
With MergeInputs=True, the converted members are merged with MergeMD v1 into a single MDEventWorkspace, and no intermediate workspaces are kept. The SplitInto, SplitThreshold and MaxRecursionDepth properties of this algorithm are passed to MergeMD v1. Because HB3AAdjustSampleNorm v1 merges with the MergeMD v1 defaults, its merged output contains the same events but a different box structure.

MergeInputs is ignored for a single input workspace.

Usage#

Example - ConvertHFIRSCDtoMDE

LoadWANDSCD(IPTS=7776, RunNumbers='26640-27944', OutputWorkspace='data',Grouping='4x4')
ConvertHFIRSCDtoMDE(InputWorkspace='data',
                    Wavelength=1.488,
                    OutputWorkspace='Q')

Output:

Example - ConvertHFIRSCDtoMDE with a group of HB3A scans

This example converts 68 scans of HB3A (DEMAND). It requires access to the data of IPTS-24855.

IPTS = 24855
exp = 755
scans = range(28, 96)
filename = "/HFIR/HB3A/IPTS-{}/shared/autoreduce/HB3A_exp{:04}_scan{:04}.nxs"
files = ",".join(filename.format(IPTS, exp, scan) for scan in scans)

# WorkspaceGroup with one detector-space MDHistoWorkspace per scan
HB3AAdjustSampleNorm(Filename=files,
                     OutputType="Detector",
                     NormaliseBy="None",
                     NormalizeData=False,
                     Grouping="4x4",
                     OutputWorkspace="detector")

# One Q-sample MDEventWorkspace per scan, named Q_<input member name>.
# Each scan has a "wavelength" sample log, so the Wavelength property is not needed.
ConvertHFIRSCDtoMDE(InputWorkspace="detector",
                    OutputWorkspace="Q")

# All scans converted with their own goniometer settings, then merged into one MDEventWorkspace
ConvertHFIRSCDtoMDE(InputWorkspace="detector",
                    MergeInputs=True,
                    OutputWorkspace="Q_merged")

HB3AAdjustSampleNorm v1 loads each scan at the full detector resolution of 512 x 1536 pixels before grouping. Building the input group for these 68 scans with Grouping="4x4" used about 28 GB of memory. The two calls to ConvertHFIRSCDtoMDE use little additional memory.