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PDLoadCharacterizations v1¶

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Summary ¶

Load a characterization file used in Powder Diffraction Reduction.

Properties ¶

Name	Direction	Type	Default	Description
Filename	Input	list of str lists	Mandatory	Characterizations file. Allowed extensions: [‘.txt’]
ExpIniFilename	Input	string		(Optional) exp.ini file used at NOMAD. Allowed values: [‘ini’]
OutputWorkspace	Output	TableWorkspace	Mandatory	Output for the information of characterizations and runs
IParmFilename	Output	string		Name of the gsas instrument parameter file.
PrimaryFlightPath	Output	number		Primary flight path L1 of the powder diffractomer.
SpectrumIDs	Output	int list		Spectrum Nos (note that it is not detector ID or workspace indices). The list must be either empty or have a size equal to input workspace’s histogram number.
L2	Output	dbl list		Secondary flight (L2) paths for each detector. Number of L2 given must be same as number of histogram.
Polar	Output	dbl list		Polar angles (two thetas) for detectors. Number of 2theta given must be same as number of histogram.
Azimuthal	Output	dbl list		Azimuthal angles (out-of-plane) for detectors. Number of azimuthal angles given must be same as number of histogram.

This algorithm loads information into a TableWorkspace for the characterization information and a collection of output parameters for the focus positions to be used in EditInstrumentGeometry v1. If a section is missing then those parameters will be empty. This includes an empty table (zero rows) if that information is missing. The resulting TableWorkspace is intended to be used by PDDetermineCharacterizations v1

This algorithm is one of the workflow algorithms that helps SNSPowderReduction v1.

Characterization File ¶

An example from POWGEN shows both of the available portions of a characterization file:

Instrument parameter file:
1 3.18 90.0000
L1 60.0
#S 1 characterization runs
#L frequency(Hz) center_wavelength(angstrom) bank_num vanadium_run empty_run vanadium_back d_min(angstrom) d_max(angstrom)
60 0.533  1 17533 0 0 0.05  2.20  0000.00  16666.67
60 1.066  2 17534 0 0 0.30  4.60  8333.33  25000.00
60 1.333  3 17535 19770 0 0.43  5.40 12500.00  29166.67
60 2.665  4 17536 0 0 1.15  9.20 33333.33  50000.00
60 4.797  5 17537 0 0 2.25 15.35 66666.67  83333.67
60 3.731  6 18280 0 0 1.70 12.50 50000.00  66666.67
10 3.198  1 17538 0 0 0.05 15.40 00000.00 100000.00

The first line Instrument parameter file: must be present to mark the beginning of the first section. Whatever string appears after the semicolon is copied into the IParmFilename output property. The following lines are of the form “bank l2 polar” with the last line being the keyword L1 followed by the effective primary flight path. This information is saved in the IParmFilename, SpectrumIDs, L2, Polar, Azimuthal and PrimaryFlightPath properties. The Azimuthal values are optional and will be set to zero if not specified. No example for specifying azimuthal angles for the focus positions is being supplied as it uncommon except for preferred orientation studies.

The second section of the characterizations file is read into the output TableWorkspace as described below.

A second example from NOMAD demonstrates how to specify different ranges for each focused spectrum as well as the optional wavelength ranges:

Instrument parameter file: NOMAD_11_22_11.prm
1 2 15
2 2 31
3 2 67
4 2 122
5 2 154
6 2 7
L1 19.5
#S 1 characterization runs
#L frequency(Hz) center_wavelength(angstrom) bank_num vanadium_run empty_run vanadium_back d_min(angstrom) d_max(angstrom) wl_min wl_max
60 1.4  1 0 0 0 .31,.25,.13,.13,.13,.42 13.66,5.83,3.93,2.09,1.57,31.42 300.00 16666.67 .1 2.9

The exp.ini file is specific to the NOMAD instrument at SNS and is optional. It will update the vanadium, container, and empty instrument value in all rows of the table. This file is generally discouraged. An example version of this file is:

required *******************
Dia 49262
DiaBg 49257
Vana 49258
VanaBg 49086
MTc 49257
optional ******************
recali yes
renorm yes
autotemp yes
scan1 49464
scanl 80000
Hz    60
# IPTS 14821

After realizing that the much of the information in the characterizations file is independent of sample environment, a second characterization file was designed to add to the information of the first. The first line is to indicate the format of the file, and the rest is whitespace delimited. There are 6 required columns, everything past that is a SampleContainer identifier which will be used to override the value that is in the original characterization file. The frequency and wavelength columns are still used as keys to determine which row contains the run identifiers:

version=1
freq wl     van   van_back mt_env mt_instr PAC06 PAC08 PAC10
0.533   27056   27050     0      0      27044 27032 27038
1.066   27057   27051     0      0      27045 27033 27039
1.333   27058   27052     0      0      27046 27034 27040
2.665   27059   27053     0      0      27047 27035 27041
3.731   27060   27054     0      0      27048 27036 27042
4.797   27061   27055     0      0      27049 27037 27043
3.198   27062       0     0      0          0     0     0

Characterization TableWorkspace ¶

The columns names and types are described in the following table. Any missing values are replaced with a zero which will generally skip that bit of information.

Name	Type
frequency	double
wavelength	double
bank	int
vanadium	str
container	str
empty	str
d_min	str
d_max	str
tof_min	double
tof_max	double
wavelength_min	double
wavelength_max	double

There can be any number of additional columns with the SampleContainer (with spaces removed) for the column name, and type of string.

Usage ¶

While there are many options for how to use this algorithm, the suggestion is to supply the classic and version 1 characterizations in a comma separated list as the Filename property.

filenames = ','.join(['PG3_char_2016_08_01-HR.txt','PG3_char_2016_02_15-PAC-single.txt'])
PDLoadCharacterizations(Filename=filenames, OutputWorkspace='char')