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LoadMuonNexusV2 v1

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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’, ‘.nxs_v1’]

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:

5 0.007265590131
6 0.006881169975
7 -0.003046069993
8 0.006345409900
9 0.007483229972
10 -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:
0.16
0.16
0.16
0.16
0.16
0.16

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