ConvertSpiceDataToRealSpace v1¶

Inputs¶

Outputs¶

Two MDEventWorkspaces will be output from this algorithm.

One MDWorkspaces stores the experimental data. Each MDEvent is a data point measured on one detector. Thus if in the experiment, M detectors moves N times, then there will be total \(M \times N\) MDEvents. It also stores the sample environment logs values in its ExperimentInfo.

The other MDWorkspaces stores the monitor counts of each detector at each measurement.

Format of SPICE data file¶

There are two parts of content in SPICE data file. One is the run information, in which line that starts with #.

In most cases, the run information is give as

# run info name = run info value

The other is the experimental data. The first item is an integer as the index of experimental data point.

How to combine measurements¶

Powder diffractometers rotates its detectors to achieve the coverage and resolution. Hence the output of of a run should include all the measurements.

MDEventWorkspace is the best solution to combine all the measurements to a single workspace and keep all the information for future reduction.

Run¶

In an HFIR powder diffractometer scan, one measurement is made at a certain rotational angle. Such one meaurement constains 44 detectors’ counts, instrument setup (such as rotation angle) and sample environment logs. As it is translated to MDWorkspace, such a measurement constitutes a {it run}.

Essential logs for building MDWorkspace¶

There are a few sample logs that are essential to create the MDWorkspaces for the HFIR powder diffractometers. The algorithm allows the user to specify these logs

• Rotation angle to determine the \(2\theta\) for detector 0. The default is ‘2theta’;
• Prefix of the logs for detectors. The default is ‘anode’. In present HB2A’s SPICE file, the detectors are labelled as ‘anode1’, ‘anode2’, and etc;
• Monitor counts for each measurement. The default is ‘monitor’;
• Duration of each measurement. The default is ‘time’.

Sample Logs¶

Sample logs will be written to the ExperimentInfo for each run. There are N+1 ExperimentInfo in the MDWorkspace that stores the detectors’ counts.

The first N ExperimentInfo are for the N measurements. The sample logs’s value measured of that data point will be recorded in the corresponding ExperimentInfo. Hence each of these N ExperimentInfo will contains a set of sample logs, each of which contains only one log entry.

The last one, i.e., ExperimentInfo[N], contains the combined sample logs from all the runs. Hence for an experiment with N runs.

Temporary MD File¶

In this algorithm, the MDEvnetWorkspaces are created by loading from a temporary MD file, which is generated from a set of MatrixWorkspaces. Each MatrixWorkspace stores the data for one individual measurement.

The format of the MD files are like

DIMENSIONS
x X m 100
y Y m 100
z Z m 100
# Signal, Error, RunId, DetectorId, coord1, coord2, ... to end of coords
MDEVENTS
125 1 1 1 0.209057 0 1.98904
133 1 1 2 0.30052 0 1.97729
114 1 1 3 0.391584 0 1.96129
130 1 1 4 0.485503 0 1.94018
143 1 1 5 0.577963 0 1.91467
135 1 1 6 0.667844 0 1.8852
120 1 1 7 0.753968 0 1.85244
115 1 1 8 0.840013 0 1.81504
145 1 1 9 0.925819 0 1.77281
117 1 1 10 1.00779 0 1.72753
105 1 1 11 1.08951 0 1.67719
102 1 1 12 1.16527 0 1.62547
108 1 1 13 1.24041 0 1.56888
110 1 1 14 1.31159 0 1.50988
... ...

If there are N detectors of the instruments and M measurements in total, then there will be \(M\times N\) MDEvents listed in the MD file.