3.5

DNSMergeRuns v1

../_images/DNSMergeRuns-v1_dlg.png

DNSMergeRuns dialog.

Summary

Merges runs performed at different detector bank positions into one matrix workspace.

Properties

Name Direction Type Default Description
WorkspaceNames Input str list   List of Workspace names to merge.
OutputWorkspace Output MatrixWorkspace Mandatory A workspace name to save the merged data.
HorizontalAxis Input string 2theta X axis in the merged workspace. Allowed values: [‘2theta’, ‘|Q|‘, ‘d-Spacing’]
Normalize Input boolean False If checked, the merged data will be normalized, otherwise the separate normalization workspace will be created.

Description

Warning

This algorithm is being developed for a specific instrument. It might get changed or even removed without a notification, should instrument scientists decide to do so.

This algorithm merges given matrix workspaces to a Workspace2D. The purpose of this algorithm is to merge the DNS diffraction mode data measured at different detector bank positions. The algorithm is not suitable to merge DNS single crystal diffraction data measured at different sample rotation angles.

Note

The OutputWorkspace will have no connection to the instrument. Part of the sample logs will be lost either. This algorithm can be executed at any step of the data reduction to view the result. However, further data reduction must be performed on the original workspaces.

As a result, following output will be produced:

  • Output workspace with corrected data. Part of sample logs will be copied from the first data workspace. The data will be normalized to monitor or run duration if the Normalize option is checked.
  • If the Normalize option is unchecked, workspace with normalization data (monitor counts or run duration) will be created. The normalization workspace is named same as the data workspace, but has suffix “_NORM”.

Warning

Normalization workspaces are created by the LoadDNSLegacy v1 algorithm. It is responsibility of the user to take care about the same type of normalization (monitor counts or run duration) for all given workspaces.

Absolute value of the momentum transfer |Q| is calculated as

|Q| = \left|\frac{4\pi\sin\theta}{\lambda}\right|

where \theta is the scattering angle and \lambda is the neutron wavelength.

d-Spacing d is calculated as:

d = \left|\frac{\lambda}{2\,\sin\theta}\right|

Valid input workspaces

The input workspaces (WorkspaceNames) have to have the following in order to be valid inputs for this algorithm.

  • The same number of dimensions
  • The same number of spectra
  • The same number of bins
  • The same wavelength in the sample logs
  • Sample log normalized must be set to “yes” for normalized data or “no” for not normalized data. Important: this value must be the same for all given workspaces. The mixture of normalized and not normalized workspaces is not accepted: algorithm will terminate with an error message.
  • If sample log normalized is set to “no”, all workspaces must have the corresponding normalization workspace.

For the physically meaningful merge result, it is also important that these workspaces have the same slits size, polarisation, and flipper status. If some of these parameters are different, algorithm produces warning. If these properties are not specified in the workspace sample logs, no comparison is performed.

Usage

Example - Merge a set of selected runs

from os import listdir
from os.path import isfile, join, splitext
import re
import numpy as np

# path to the directory containing data files
mypath = "/path/to/data/dns/rc36b_standard_dz"

# filter the data files in the given directory
p = re.compile('^dz(\d{8})vana.d_dat$')

# we choose only the runs with 'x' polarisation
filelist = [str(i*6 + 29100501) for i in range(10)]

def is_in_filelist(fname, p, flist):
    m = re.match(p, fname)
    if m:
        num = m.group(1)
        return num in flist
    else:
        return False

datafiles = sorted([f for f in listdir(mypath) if isfile(join(mypath,f)) and is_in_filelist(f, p, filelist)])

# load data to workspaces
wslist = []
for f in datafiles:
    try:
        wname = splitext(f)[0]
        #print "Processing ", wname  # uncomment if needed
        LoadDNSLegacy(Filename=join(mypath, f), OutputWorkspace=wname, Polarisation='x', Normalization='duration')
    except RuntimeError as err:
        print err
    else:
        wslist.append(wname)

# merge the given workspaces
merged = DNSMergeRuns(wslist, HorizontalAxis='2theta', Normalize=True)
mergedQ = DNSMergeRuns(wslist, HorizontalAxis='|Q|')
mergedD = DNSMergeRuns(wslist, HorizontalAxis='d-Spacing')

# print selected values from merged workspaces
two_theta = merged.extractX()[0]
print "First 5 2Theta values: ", two_theta[:5]
q = mergedQ.extractX()[0]
print "First 5 |Q| values: ", np.round(q[:5], 3)
d = mergedD.extractX()[0]
print "First 5 d values: ", np.round(d[:5], 3)

Output:

First 5 2Theta values: [ 7.5 8. 8.5 9. 9.5]

First 5 Q values: [ 0.249 0.266 0.282 0.299 0.315]

First 5 d values: [ 1.844 1.848 1.852 1.856 1.86 ]

Categories: Algorithms | PythonAlgorithms | MLZ | DNS