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LoadMuonNexus v2¶
![../_images/LoadMuonNexus-v2_dlg.png](../_images/LoadMuonNexus-v2_dlg.png)
LoadMuonNexus dialog.¶
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 LoadNexus if it is given a NeXus file of this type.
See Also¶
Properties¶
Name |
Direction |
Type |
Default |
Description |
---|---|---|---|---|
Filename |
Input |
string |
Mandatory |
The name of the Nexus file to load. Allowed extensions: [‘.nxs’] |
OutputWorkspace |
Output |
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 |
Index number of the first spectrum to read |
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) |
|
LastGoodData |
Output |
number |
Last good data in the OutputWorkspace’s spectra |
|
TimeZeroList |
Output |
dbl list |
A vector of time zero values |
|
TimeZeroTable |
Output |
TableWorkspace containing time zero values per spectra. |
||
CorrectTime |
Input |
boolean |
True |
Boolean flag controlling whether time should be corrected by timezero. |
DeadTimeTable |
Output |
Table or a group of tables containing detector dead times. Version 1 only. |
||
DetectorGroupingTable |
Output |
Table or a group of tables with information about the detector grouping stored in the file (if any). Version 1 only. |
Description¶
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.
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.
Errors¶
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 |
Workspace instrument as loaded by LoadInstrumentFromNexus |
Spectrum of each workspace index |
[DET]``/spectrum_index`` |
Spectra-Detector mapping of workspace (see below) |
Title (optional) |
|
|
Note orcomment (optional) |
|
|
Time Zero (optional) |
|
TimeZero property |
First good time (optional) |
|
FirstGoodData property |
Run |
various places as shown later on |
Run object of workspace |
Sample name |
|
|
Time series |
|
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 |
---|---|
|
|
(data) |
|
|
|
|
|
|
|
|
|
(start & end times) |
|
(data) indicates that the number is got from the histogram data in an appropriate manner.
Spectra-detector mapping¶
Unlike muon v1 NeXus files, v2 files have the possibility that one spectrum maps to multiple detectors. This mapping is handled as follows:
The spectrum numbers are in run/detector_fb/spectrum_index
.
The spectrum spectrum_index[j]
maps to detector_count[j]
detectors.
Their detector IDs are contained in detector_list
, starting at the index detector_index[j]
.
If the above optional entries detector_count
, detector_list
and detector_index
are not present
in the file, it is assumed that the mapping is one-to-one (spectrum number = detector ID). This is the case
for most ISIS data at the moment.
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.
Usage¶
Note
To run these usage examples please first download the usage data, and add these to your path. In Mantid 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 {} spectra".format(ws[0].getNumberHistograms()))
Output:
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 {} spectra".format(ws[0].getNumberHistograms()))
Output:
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("{} {:.12f}".format(tab.cell(i,0), tab.cell(i,1)))
Output:
5 0.001611122512
6 0.002150168177
7 0.010217159986
8 0.004316862207
9 0.007436056621
10 0.004211476538
Categories: AlgorithmIndex | DataHandling\Nexus | Muon\DataHandling
Source¶
C++ header: LoadMuonNexus2.h
C++ source: LoadMuonNexus2.cpp