Binning a Reduced Workspace in QuickNXS

Overview

Binning is an essential process in reflectivity reduction within QuickNXS, organizing raw data into manageable intervals for accurate analysis. Several binning options are available at various steps of the data reduction process. An initial time-of-flight binning options is available to process the raw data, which is later converted into Q bins. A final Q rebinning is optionally available for user who want their reflectivity output in specific Q binning. This guide explains the available binning options in QuickNXS and how to configure them for the best results.

Note

All binning options are ultimately passed to the MagnetismReflectometryReduction algorithm in Mantid.

Binning Options

The following options allow users to fine-tune binning behavior:

Bin Width (Numeric Input, Applied Globally)

• Constraints: Must be an integer value between 5 and 10000 microseconds.

• What It Does: Defines the width, in microseconds, of bins used to rebin the input workspace in time-of-flight (TOF).

• How It Works:

  • This step always occurs and cannot be skipped.

  • If the minimum TOF (Time-of-Flight) value is ≤ 0, Bin Width is also used as the TOF minimum.

  • The direct beam workspace is rebinned to match the binning of the input workspace before reflectivity is calculated.

• How to Use It: Enter a numeric value to specify the desired bin width.

Entering the Bin Width

Final Rebin (Checkbox, Per-Run or Global)

• What It Does: Controls whether the final reduced workspace (converted to Q-space) undergoes additional rebinning.

• How It Works:

  • When enabled, rebinning is performed using Q Steps, in units of 1/Å, as the bin width.

  • This option is only available if Constant-Q Binning is disabled.

  • If Constant-Q Binning is enabled, it takes priority over Final Rebin.

  • If Final Rebin is enabled per-run, the Q Steps values can be viewed and updated in the reduction data table under the Q-Steps column. If it is enabled globally, it takes priority over any per-run Q Steps values.

• How to Use It: Check this box if you want to apply final rebinning.

Enabling Final Rebin Globally

Enabling Final Rebin Per-Run

Constant-Q Binning (Checkbox, Applied Globally)

• What It Does: uses the position of each pixel and the specified TOF binning to sum counts directly in Q bins. This differs from the traditional reflectivity calculation, which assumes that all counts in a TOF bin has the same Q value regardless of where they landed on the detector.

• How It Works:

  • When enabled, Final Rebin is not performed.

  • Enabling Constant-Q binning changes the way R(q) is calculated.

  • Q Steps is used to determine binning:

    • If positive, bins are evenly spaced.

    • If negative, bins are spaced logarithmically using a geometric progression.

  • This setting is global and cannot be adjusted per-run.

• How to Use It: Check this box if you want to maintain constant-Q binning. Ensure Q Steps is set appropriately for either linear or logarithmic binning.

Enabling Constant-Q Binning

Q Steps (Numeric Input, Per-Run or Global)

• Constraints: Must be a floating point value between -0.1 and 0.1 units of 1/Å.

• What It Does: Defines the bin width for the final rebinning in Q-space.

• How It Works:

  • Q Steps is used in both Final Rebin and Constant-Q Binning.

  • When Final Rebin is enabled, Q Steps sets the bin width for the final rebinning.

  • When Constant-Q Binning is enabled, Q Steps determines whether binning follows a linear or logarithmic scale.

    • It controls the resolution of the final reduced workspace.

    • If Q Steps is positive, linear binning is applied with evenly spaced bins.

    • If Q Steps is negative, logarithmic binning is applied, where bin edges follow a geometric progression.

• How to Use It: Enter a numeric value to specify the bin width for Q-space rebinning. Use negative values for logarithmic binning.

Setting Q Steps Globally disables the Q-Steps column in the reduction table

Setting Q Steps Per-Run adds the value to the Q-Steps column in the reduction table

Binning Workflow

To apply binning settings effectively, follow these steps:

1. Set the Input Workspace Binning:

• Enter a Bin Width value to define the initial binning.

• If TOF min is ≤ 0, Bin Width will also be used as the TOF minimum.

• The direct beam workspace is automatically rebinned to match this setting.

1. Apply Final Binning (Optional):

• If Constant-Q Binning is enabled, it takes priority over Final Rebin.

• If Constant-Q Binning is disabled and additional Q-space binning is required, check Final Rebin and specify a Q Steps value.

• If Final Rebin is enabled per-run, the Q Steps values can be viewed and updated in the reduction data table under the Q-Steps column.

• If using Constant-Q Binning, ensure Q Steps is appropriately set for linear or logarithmic binning.

By adjusting these options, users can customize their reflectivity reduction workflow to achieve the desired data resolution and accuracy.