Igor experiments

There are two basic types of measured data — USAXS and QRS — which you need to distinguish when browsing an Igor experiment with reduced data from this instrument. Irena also recognizes Irena results as a data type produced by its own analysis tools (Size distribution, Unified fit, etc.).

USAXS data type

Regardless of whether Fly scanning or step scanning was used, data will be of type USAXS. Data are stored in root:USAXS, organized into one folder per data collection run — for example, SampleName_0001. Inside that folder you will find many waves, but two groups are of primary importance:

  1. SMR_Qvec, SMR_Int, SMR_Error — Q vector, intensity, and uncertainty for slit-smeared data. The slit length (typically 0.025–0.035 Å−1) is stored in the wave note. These data are on absolute intensity scale when a proper sample thickness was provided during data reduction. Irena can use these data for modeling, as slit smearing is built into the code and is activated automatically when needed.

  2. DSM_Qvec, DSM_Int, DSM_Error — Q vector, intensity, and uncertainty for pinhole (desmeared) data. These are obtained either by desmearing (during or after data reduction using the dedicated tool) or by using a 2D-collimated USAXS instrument geometry.

SAXS/WAXS data type

SAXS and WAXS data are reduced using Nika, which uses the QRS naming convention. Data are organized in root:SAXS and root:WAXS folders, with one subfolder per data collection run, ideally named to match the associated USAXS dataset: SampleName_0001_xyz. The xyz code identifies the type of data reduction applied:

  1. 270_30 (SAXS) — Sector average in the 270° direction (vertically down), ±30° width. These are pinhole-collimated SAXS data for direct use or for merging with DSM-type USAXS data. Generated by default in all data reduction runs.

  2. u (SAXS) — Nika-generated pseudo-slit-smeared data using the same slit length as the USAXS data. Used exclusively for merging with SMR-type USAXS data. Generated only when the “USAXS data not desmeared” checkbox is selected on the control panel.

  3. C (WAXS) — Circular average around the beam center over the valid data region.

In the QRS naming system, a folder named SampleName_0001_xyz contains q_SampleName_0001_xyz (Q vector), r_SampleName_0001_xyz (intensity), and s_SampleName_0001_xyz (uncertainty).

Merged data types

Data merging is performed using the Data Merge tool. After merging, new folders appear inside the parent folder of the first (left-hand, low-Q) dataset, using that dataset’s type. Naming examples:

  • USAXS + SAXS → root:USAXS:SampleName_0001_mrg — USAXS-type data (SMR or DSM), extended through the SAXS Q range.

  • USAXS + SAXS + WAXS → root:USAXS:SampleName_0001_mrg_mrg — USAXS-type data covering approximately 5 decades in Q. Note that such a wide Q range typically requires separate analysis approaches for different regions.

  • SAXS + WAXS → root:SAXS:SampleName_0001_270_30_mrg — QRS-type data. Ensure SAXS is set to “max number of points” before reduction.

Merged USAXS datasets (_mrg) are recognized as USAXS-type by Irena and can be used directly for modeling in either SMR or DSM form.

Export for other tools

Warning

Do not export slit-smeared (SMR) data for use in other software tools unless you are certain those tools correctly handle the slit-smearing geometry used here. Verify compatibility with beamline staff before doing so.

Use the Export data tool to export ASCII or NeXus/NXcanSAS for SAS analysis tools, or GSAS xye format for WAXS tools such as GSAS-II.