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• Sample parameters
• Polarization options
• Advanced reduction options

Sample parameters

This dialog box allows setting/ modifying the lattice parameters and sample orientation (the UB matrix). There are two ways to specify these:

• The a, b, c, alpha, beta, gamma are the lattice parameters. When the goniometer angles are all zero, the orientation vector u = (ux, uy, uz) points along the beam, and the v = (vx, vy, vz) vector is in the horizontal plane, not necessarily perpendicular to u, in a way that the cross product points upward.
• The UB matrix. A good explanation can be found in the Mantid concepts page

One can also load these parameters from the raw file, a processed nexus file, or an ISAW UB matrix file.

Polarization options

For polarized neutron experiments, it is useful to label the data with the polarization state:

The state it used as a suggestion when selecting data.

If both polarization states are selected in the main window, the Flipping ratio and Flipping ratio sample log parameters are passed to the FlippingRatioCorrectionMD algorithm, so in the end one ends up with flipping ratio corrected histograms.

For the HYSPEC instrument, when using the supermirror polarization analyser, the neutron will be deflected by a small amount, the PSDA (polarization supermirror deflection angle). This needs to be taken in consideration when generating the MD event data. By default, this value is taken from the file, so leave this field empty. If you want to override, 0.0 is unpolarized, and -1.3 is for the polarized state.

Advanced reduction options

When generating multi-dimensional event data sets, there are some advanced options available:

• In addition to the mask file in the Generate tab, one can mask additional detectors. Each line in the Mask Bank, Tube, Pixel is used independently. So in the example in the figure, tubes 1, 2, and 3 in the first bank are masked, followed by masking pixels 1 to 8 and 121 to 128 in every bank, in every tube.
• The Emin and Emax define the energy transfer range, in meV. The default values are -0.95 and +0.95 times the incident energy
• The pulses with low proton charge can be filtered out using the Apply filter bad pulses flag, where neutrons coming from pulses with charge less than Lower cutoff (%) of the median pulse charge will be ignored
• One can subtract a time independent background. If Instrument default option is used, there is no such subtraction for ARCS or SEQUOIA instruments. For CNCS and HYSPEC, a range is calculated based on incident energy. One can override this behavior by selecting Yes, in which case one must specify the range manually, or No.
• By default, the sample rotation angle is obtained from the phi, chi, and omega logs in the file. If not present, or incorrect, one can specify a different sample log name that contains the rotation around the vertical axis, using the Goniometer field.
• The Additional dimensions is not currently used in the main histogramming part, but it can be in a script. This field specifies the name of an additional dimension in the dataset, such as sample temperature. The value associated with each event is the average value in the original file (no filtering is taking place)