LoadMuonNexus dialog.
Table of Contents
The LoadMuonNexus algorithm will read the given NeXus Muon data file Version 1 and use the results to populate the named workspace. LoadMuonNexus may be invoked by LoadNexus if it is given a NeXus file of this type.
| Name | Direction | Type | Default | Description |
|---|---|---|---|---|
| Filename | Input | string | Mandatory | The name of the Nexus file to load. Allowed extensions: [‘.nxs’] |
| OutputWorkspace | Output | Workspace | Mandatory | The name of the workspace to be created as the output of the algorithm. For multiperiod files, one workspace will be generated for each period |
| SpectrumMin | Input | number | Optional | Index number of the first spectrum to read (default 1) |
| SpectrumMax | Input | number | Optional | Index of last spectrum to read (default the last spectrum) |
| SpectrumList | Input | int list | Array, or comma separated list, of indexes of spectra to load. If a range and a list of spectra are both supplied, all the specified spectra will be loaded. | |
| AutoGroup | Input | boolean | False | Determines whether the spectra are automatically grouped together based on the groupings in the NeXus file, only for single period data (default no). Version 1 only. |
| EntryNumber | Input | number | 0 | 0 indicates that every entry is loaded, into a separate workspace within a group. A positive number identifies one entry to be loaded, into one workspace |
| MainFieldDirection | Output | string | Output the main field direction if specified in Nexus file (run/instrument/detector/orientation, default longitudinal). Version 1 only. Allowed values: [‘Transverse’, ‘Longitudinal’] | |
| TimeZero | Output | number | Time zero in units of micro-seconds (default to 0.0) | |
| FirstGoodData | Output | number | First good data in units of micro-seconds (default to 0.0) | |
| DeadTimeTable | Output | Workspace | Table or a group of tables containing detector dead times. Version 1 only. | |
| DetectorGroupingTable | Output | Workspace | Table or a group of tables with information about the detector grouping stored in the file (if any). Version 1 only. |
The algorithm LoadMuonNexus will read a Muon Nexus data file (original format) and place the data into the named workspace. The file name can be an absolute or relative path and should have the extension .nxs or .NXS. If the file contains data for more than one period, a separate workspace will be generated for each. After the first period the workspace names will have “_2”, “_3”, and so on, appended to the given workspace name. The optional parameters can be used to control which spectra are loaded into the workspace. If SpectrumMin and SpectrumMax are given, then only that range of data will be loaded. If a SpectrumList is given, then those values will be loaded. If a range and a list are supplied, the algorithm will load all the specified spectra.
For all v1 muon Nexus files, there is a one-to-one mapping between spectrum number and detector ID.
The log data in the Nexus file (NX_LOG sections) will be loaded as TimeSeriesProperty data within the workspace. Time (stored as seconds from the Unix epoch in the Nexus file) is corrected relative to the start time found in run/start_time.
This time series data comprises various values logged by SECI and includes magnetic fields, temperatures, status codes, count rate and beam logs.
See LoadMuonLog v1 for more details.
The corrected_times field of the Nexus file is used to provide time bin data and the bin edge values are calculated from these bin centre times.
To determine if a file contains data from more than one period the field
switching_states is read from the Nexus file. If this value is
greater than one it is taken to be the number of periods, 
of
the data. In this case the 
spectra in the histogram_data
field are split with 
assigned to each period.
Muon Nexus v1 files might contain dead time and detector grouping information. These are loaded as TableWorkspaces of the format accepted by ApplyDeadTimeCorr v1 and MuonGroupDetectors v1 accordingly. These are returned if and only if names are specified for the properties. For multi-period data workspace groups might be returned, if information in the Nexus files contains this information for each period.
If the file contains no grouping entry (or the entry is full of zeros), the grouping will be loaded from the IDF instead. If this also fails, a dummy grouping will be created. In either case, a message will be displayed in the log to explain this.
Here are more details of data loaded from the Nexus file. Conventionally, the first NX_ENTRY is called run and the first NX_DATA under this is called histogram_data_1, and these names are used below.
| Description of Data | Found in Nexus file | Placed in Workspace (Workspace2D) or output |
|---|---|---|
| Detector data |
|
Histogram data of workspace |
| Instrument | Name from run/instrument/name Uses child algorithm LoadInstrument to load the instrument of that name |
Workspace instrument (as loaded by LoadInstrument from IDF) |
| Title (optional) | run/title | Workspace title |
| Comment (optional) | run/notes | Workspace comment |
| Time zero (optional) | run/histogram_data_1/time_zero | TimeZero property |
| First good data (optional) | Calculated from first good bin and bin size.
|
FirstGoodData property (First good data - time zero) also goes in run object under the name FirstGoodData |
| Detector grouping table (optional) | run/histogram_data_1/grouping If not present, or invalid, loads from IDF. If that also fails, creates dummy grouping (all detectors in one group). |
DetectorGroupingTable property |
| Dead time table (optional) | run/instrument/detector/deadtimes | DeadTimeTable property |
| Main field direction (optional) | run/instrument/detector/orientation Assumed to be longitudinal if not present |
MainFieldDirection property Also in run object as main_field_direction |
| Sample name | run/sample/name | Name of sample object |
| Run | See below | Run object (see below) |
Log values are loaded into the workspace run object as follows:
| Nexus | Workspace run object |
|---|---|
| run/title | run_title |
| (data) | nspectra |
| run/start_time | run_start |
| run/stop_time | run_end |
| run/duration | dur, dur_secs (same), durunits = 1 (seconds) |
| run/number | run_number |
| run/sample/temperature | sample_temp |
| run/sample/magnetic_field | sample_magn_field |
run/instrument/beam/frames_good (for single-period data) (If frames_good not present, use frames instead.) |
goodfrm (number of good frames) |
| run/instrument/beam/frames_period_daq (for multi-period data) | |
| Other NX_LOG entries under run | time series (via LoadMuonLog) |
The ChildAlgorithms used by LoadMuonNexus are:
Categories: Algorithms | DataHandling\Nexus | Muon\DataHandling