SaveSESANS v1#

Summary#

Save a file using the SESANS format

Properties#

Name	Direction	Type	Default	Description
InputWorkspace	Input	`MatrixWorkspace`	Mandatory	The name of the workspace to save
Filename	Input	string	Mandatory	The name to use when saving the file. Allowed extensions: [‘.ses’, ‘.sesans’]
ThetaZMax	Input	number	Optional	The angular acceptance in the encoding direction
ThetaZMaxUnit	Input	string	radians
ThetaYMax	Input	number	Optional	The angular acceptance in the non-encoding direction
ThetaYMaxUnit	Input	string	radians
EchoConstant	Input	number	Optional	The spin echo length, in nanometers, probed by a 1A neutron
Sample	Input	string		Sample name
Orientation	Input	string	Z	Orientation of the instrument. Allowed values: [‘X’, ‘Y’, ‘Z’]
OverrideSampleThickness	Input	number	Optional	The sample thickness in mm. If set, this value will be used instead of the thickness from the input workspace sample
Facility	Input	string		The facility where the data was measured. If not set, the facility is determined from the instrument
Instrument	Input	string		The instrument used to measure the data. If not set, the instrument name is taken from the input workspace
RunNumber	Input	string		The run number of the sample measurement. If not set, the run_number log of the input workspace is used
SamplePosition	Input	string		The name of the sample changer position, e.g. AT or 1CT. If not set, the positions recorded in the SamplePos log of the input workspace during the selected time range are used
BlankRunNumber	Input	string		The run number of the blank measurement. Optional.
SampleTransmissionRunNumber	Input	string		The run number of the sample transmission measurement. Optional.
BlankTransmissionRunNumber	Input	string		The run number of the blank transmission measurement. Optional.

Description#

Saves the given workspace to a file which will be formatted in the SESANS data format. A workspace with a single spectrum is expected, where the X values are wavelength and the Y values are polarisation.

The sample thickness from the run metadata is used to normalise the polarisation data. The OverrideSampleThickness parameter can be used to specify a different value for this if needed.

Measurement metadata#

To help identify the measurement, the following entries are added to the file header after the mandatory SESANS headers:

Header	Value
Facility	The `Facility` property if set, otherwise the facility that the instrument belongs to, as defined in the Mantid facilities configuration
Instrument	The `Instrument` property if set, otherwise the instrument name of the input workspace
Run_number	The `RunNumber` property if set, otherwise the `run_number` sample log of the input workspace
Sample_position	The `SamplePosition` property if set, otherwise the sample changer positions (e.g. `AT` or `1CT`) recorded in the `SamplePos` sample log during the selected time range, in order and separated by commas
Blank_run_number	The `BlankRunNumber` property
Sample_transmission_run_number	The `SampleTransmissionRunNumber` property
Blank_transmission_run_number	The `BlankTransmissionRunNumber` property
Reduction_software	Always `Mantid`
Software_version	The version of Mantid used to save the file
Reduction_date	The date and time (UTC, ISO 8601) at which the file was saved

The Facility, Instrument, Run_number, Sample_position and blank and transmission run number entries are omitted if no value can be determined.

The time range used for Sample_position is from the start to the end of the run, unless the workspace has been filtered by time, for example using FilterByTime. The position at the start of the time range is included, but positions logged earlier are not. Repeated positions are only listed once, so a sample that stayed in one position gives a single value. For older data, the SamplePos log may contain a number rather than the name of the position.

Usage#

Example - Loading a file

import os

# Create dummy workspace with sample thickness metadata
dataX = [1,2,3,4,5]
dataY = [6,1,9,14]
dataE = [1,1,4,5]
out_ws = CreateWorkspace(dataX, dataY, dataE)
out_ws.setTitle("Dummy workspace")
out_ws.sample().setThickness(10)

file_path = os.path.join(config["defaultsave.directory"], "example.ses")

# Do a 'roundtrip' of the data
SaveSESANS(InputWorkspace=out_ws, Filename=file_path, ThetaZMax=1,ThetaYMax=1, EchoConstant=1, Sample="Sample")
LoadSESANS(Filename=file_path, OutputWorkspace="in_ws")

# Retrieve loaded workspace from ADS
in_ws = mtd["in_ws"]
print("Y values of loaded workspace = " + str(in_ws.y(0)))

Output:

Y values of loaded workspace = [0.796338 0.       0.179365 0.130324]

Categories: AlgorithmIndex | DataHandling\Text

Source#

C++ header: SaveSESANS.h

C++ source: SaveSESANS.cpp