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LoadMuonNexusV2 v1¶

Summary ¶

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 Load if it is given a NeXus file of this type.

Properties ¶

Name	Direction	Type	Default	Description
Filename	Input	string	Mandatory	The name of the Nexus file to load. Allowed extensions: [‘.nxs’, ‘.nxs_v2’]
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	0
SpectrumMax	Input	number	Optional
SpectrumList	Input	int list
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 (default longitudinal). 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)
LastGoodData	Output	number		Last good data in the OutputWorkspace’s spectra
TimeZeroList	Output	dbl list		A vector of time zero values
TimeZeroTable	Output	Workspace		TableWorkspace containing time zero values per spectra.
CorrectTime	Input	boolean	True	Boolean flag controlling whether time should be corrected by timezero.
DeadTimeTable	Output	Workspace		Table or a group of tables containing detector dead times.
DetectorGroupingTable	Output	Workspace		Table or a group of tables with information about the detector grouping.

Description ¶

The algorithm LoadMuonNexusV2 will read a Muon Nexus data file 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 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.

Note: Currently only single period loading is supported

File Identification ¶

To be identified as a Muon nexus V2 file, the nexus file must have the top level entry /raw_data_1 so it can be loaded using the LoadISISNexus child algorithm, see LoadISISNexus v2. As well as the raw_data_1 entry, the file should also have an IDF_version group with value 2 and a definition group, with string value "muonTD" or "pulsedTD".

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.

Details of data loaded ¶

In the table below details of the information loaded is shown, for more information see LoadISISNexus v2.

Description of Data	Found in Nexus file (within the raw_data_1 entry)	Placed in Workspace (Workspace2D) or output
Detector Data	`/detector_1`	Histogram Data of workspace
Instrument	`/instrument`	Workspace instrument as loaded by LoadInstrumentFromNexus
Spectrum of each workspace index	`/detector_1/spectrum_index`	Spectra-Detector mapping of workspace (assume 1-1 mapping)
Time Zero	`instrument/detector_1/time_zero` if found	TimeZero property
Time Zero Vector	`instrument/detector_1/time_zero` can be a single value or an array. This contains either the the values from the array or the single value expanded into a vector	TimeZeroList property
First good time	`instrument/detector_1/first_good_bin` and `instrument/detector_1/resolution`	FirstGoodData property
Nexus logs	`/runlog` entry	Sample logs, loaded using LoadNexusLogs
Mainfield direction	`instrument/detector_1/orientation` entry if found, else assumed Longitudinal	MainFieldDirection Property
Deadtime table	`instrument/detector_1/dead_time` entry	Deadtime table

Run Object ¶

LoadMuonNexusV2 uses LoadNexusLogs LoadNexusLogs v1.to load the run logs. Information is loaded from the /raw_data_1/runlog entry. Additionally, LoadMuonNexusV2 loads the sample log entries from /raw_data_1/sample entry, which contains the following:

Nexus	Workspace run object
magnetic_field	`sample_magn_field`
temperature	`sample_temp`

Spectra-detector mapping ¶

The spectrum numbers are in run/detector_1/spectrum_index and a one-one correspondence between spectrum number and detector ID is assumed.

Usage ¶

Example - Load ISIS muon MUSR dataset:

# Load MUSR dataset
ws = LoadMuonNexusV2(Filename="EMU00102347.nxs_v2")
print("Workspace has  {}  spectra".format(ws[0].getNumberHistograms()))

Output:

Workspace has  96  spectra

Example - Load event nexus file with time filtering:

# Load some spectra
ws = LoadMuonNexusV2(Filename="EMU00102347.nxs_v2",SpectrumMin=5,SpectrumMax=10)
print("Workspace has  {}  spectra".format(ws[0].getNumberHistograms()))

Output:

Workspace has  6  spectra

Example - Load dead times into table:

# Load some spectra
ws = LoadMuonNexusV2(Filename="EMU00102347.nxs_v2",SpectrumMin=5,SpectrumMax=10,DeadTimeTable="deadTimeTable")
tab = mtd['deadTimeTable']
for i in range(0,tab.rowCount()):
    print("{} {:.12f}".format(tab.cell(i,0), tab.cell(i,1)))

Output:

0.007265590131
0.006881169975
-0.003046069993
0.006345409900
0.007483229972
-0.010110599920

Example -Time zero loading:

# Load some spectra
ws, main_field_direction, time_zero, first_good_data, last_good_data, time_zero_list, time_zero_table, dead_time_table, detector_grouping_table = \
   LoadMuonNexusV2(Filename="EMU00102347.nxs_v2",SpectrumMin=5,SpectrumMax=10,DeadTimeTable="deadTimeTable",TimeZeroTable="timeZeroTable")

print('Single time zero value is {:.2g}'.format(time_zero))
print("TimeZeroList values are:")
for timeZero in time_zero_list:
   print(round(timeZero, 2))

Output:

Single time zero value is 0.16
TimeZeroList values are:
16
16
16
16
16
16

Example - Test loading a multi period file:

# Load a multi period file
load_muon_alg = LoadMuonNexusV2(Filename="EMU00103767.nxs_v2")
# The workspace is the first return value from the Loader.
wsGroup = load_muon_alg[0]
print("Workspace Group has  {}  workspaces".format(wsGroup.getNumberOfEntries()))
for i in range(wsGroup.getNumberOfEntries()):
    print("Workspace has  {}  spectra".format(wsGroup.getItem(i).getNumberHistograms()))

Output:

Workspace Group has  4  workspaces
Workspace has  96  spectra
Workspace has  96  spectra
Workspace has  96  spectra
Workspace has  96  spectra

Categories: AlgorithmIndex | DataHandling\Nexus

Source ¶

C++ header: LoadMuonNexusV2.h

C++ source: LoadMuonNexusV2.cpp