LoadMuonNexus v2


LoadMuonNexus dialog.


The LoadMuonNexus algorithm will read the given NeXus Muon data file Version 2 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
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. For single period data, the optional parameters can be used to control which spectra are loaded into the workspace. If spectrum_min and spectrum_max are given, then only that range to data will be loaded. If a spectrum_list is given than those values will be loaded.

  • TODO get XML descriptions of Muon instruments. This data is not in existing Muon Nexus files.
  • TODO load the spectra detector mapping. This may be very simple for Muon instruments.

Version Identification

To be identified as a version 2 muon nexus file, the nexus file must have a IDF_version or idf_version item in its main group with an integer value of 2 and also a definition item with string value "muonTD" or "pulsedTD", else it will be identified as version 1.

The following properties apply only to Version 1:

  • AutoGroup
  • MainFieldDirection
  • DeadTimeTable
  • DetectorGroupingTable

Time series data

The log data in the Nexus file (NX_LOG sections) will be loaded as TimeSeriesProperty data within the workspace. Time is stored as seconds from the Unix epoch.


The error for each histogram count is set as the square root of the number of counts.

Details of data loaded

Here are more details of data loaded from the Nexus file:

Description of Data Found in Nexus file (within the main entry) Placed in Workspace (Workspace2D) or output
Detector Data First group of class NXData (henceforth referred as [DET]) Histogram Data of workspace
Instrument group Instrument Workspace instrument as loaded by LoadInstrumentFromNexus
Spectrum of each workspace index [DET]``/spectrum_index`` Spectra-Detector mapping of workspace
Title (optional) title title in workspace
Note orcomment (optional) note comment in workspace
Time Zero (optional) instrument/detector_fb/time_zero if found TimeZero property
First good time (optional) instrument/detector_fb/first_good_time if found FirstGoodData property
Run various places as shown later on Run object of workspace
Sample name sample/name name in Sample Object of workspace
Time series sample/ groups of class NXLog time series log in run object

Run Object

LoadMuonNexus does not run LoadNexuslogs to load run logs. Information is loaded as follows:

Nexus Workspace run object
title run_title
(data) nspectra
start_time run_start
end_time run_end
run/good_total_frames goodfrm
run/number_periods nperiods
(start & end times) dur_secs

(data) indicates that the number is got from the histogram data in an appropiate manner.

Child Algorithms used

The ChildAlgorithms used by LoadMuonNexus are:

  • LoadMuonNexus v1 - this loads the muon nexus file if not identified as version 2. It in turn uses the following child algorithm: - LoadMuonLog v1 - this reads log information from the Nexus file and uses

    it to create TimeSeriesProperty entries in the workspace.

  • LoadInstrument v1 - this algorithm looks for an XML description of the instrument and if found reads it.

  • LoadInstrumentFromNexus v1 - this is called if the normal LoadInstrument fails. As the Nexus file has limited instrument data, this only populates a few fields.

Previous Versions

Version 1

Version 1 supports the loading version 1.0 of the muon nexus format. This is still in active use, if the current version of LoadMuonNexus detects that it has been asked to load a previous version muon nexus file it will call the previous version of the algorithm to perform the task.

See LoadMuonNexus v1 for more details about version 1.

Some algorithm properties apply to Version 1 only.



To run these usage examples please first download the usage data, and add these to your path. In MantidPlot this is done using Manage User Directories.

Example - Load ISIS muon MUSR dataset:

# Load MUSR dataset
ws = LoadMuonNexus(Filename="MUSR00015189.nxs",EntryNumber=1)
print "Workspace has ",  ws[0].getNumberHistograms(), " spectra"


Workspace has  64  spectra

Example - Load event nexus file with time filtering:

# Load some spectra
ws = LoadMuonNexus(Filename="MUSR00015189.nxs",SpectrumMin=5,SpectrumMax=10,EntryNumber=1)
print "Workspace has ",  ws[0].getNumberHistograms(), " spectra"


Workspace has  6  spectra

Example - Load dead times into table:

# Load some spectra
ws = LoadMuonNexus(Filename="emu00006473.nxs",SpectrumMin=5,SpectrumMax=10,DeadTimeTable="deadTimeTable")
tab = mtd['deadTimeTable']
for i in range(0,tab.rowCount()):
    print tab.cell(i,0), tab.cell(i,1)


5 0.00161112251226
6 0.00215016817674
7 0.0102171599865
8 0.00431686220691
9 0.00743605662137
10 0.00421147653833

Example - Load detector grouping into table:

# Load some spectra
ws = LoadMuonNexus(Filename="emu00006473.nxs",SpectrumList="1,16,17,32",DetectorGroupingTable="detectorTable")
tab = mtd['detectorTable']
for i in range(0,tab.rowCount()):
    print tab.cell(i,0)


[ 1 16]
[17 32]

Categories: Algorithms | DataHandling\Nexus | Muon\DataHandling


C++ source: LoadMuonNexus2.cpp

C++ header: LoadMuonNexus2.h