4.2

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 Mandatory 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’]

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, a workspace containing a single spectrum will be produced. Values on X-axis depend on user’s choice.

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
  • The same value of normalized sample log. Algorithm cannot merge data with different normalizations.

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"
coilcurrents = join(mypath, 'currents.txt')

# 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 {}".format(wname))  # uncomment if needed
        LoadDNSLegacy(Filename=join(mypath, f), OutputWorkspace=wname, CoilCurrentsTable=coilcurrents, Normalization='duration')
    except RuntimeError as err:
        print(err)
    else:
        wslist.append(wname)

# merge the given workspaces
merged = DNSMergeRuns(wslist, HorizontalAxis='2theta')
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: {}".format(two_theta[:5]))
q = mergedQ.extractX()[0]
print("First 5 |Q| values: {}".format(np.round(q[:5], 3)))
d = mergedD.extractX()[0]
print("First 5 d values: {}".format(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: AlgorithmIndex | Workflow\MLZ\DNS

Source

Python: DNSMergeRuns.py (last modified: 2019-05-28)