12 corrections in a row

Close-up of the effect of data correction

Just a couple of housekeeping notes: I’m giving talks in Europe in a month at the following locations:

  1. Unité Matériaux et Transformations (UMET), Lille on May 16, hosted by Grégory Stoclet,
  2. Birmingham University, Birmingham on the 20th of May, hosted by Zoe Schnepp,
  3. Nottingham University, Nottingham, on the 23rd of May, hosted by Philip Moriarty,

Between these dates, I’ll also be joining Zoe and Martin for beamtime at the Diamond synchrotron (beamline I11) between May 21 and May 23. Please feel free to stop me at these locations and say hi!

For today, I’ve got another bit of data correction to show. I thought it might be interesting to put them all together and show you what difference it makes to an integrated scattering pattern. Many of the data corrections implemented are quite straightforward shifts and scalings, but some are more involved and have a greater effect on the scattering pattern. Read more »



Me before starting my Ph. D. project.

I’ve been working on a lot of things of late, but none are yet in a state to show here yet. However, when talking to a colleague last week, I found it hard to explain why I do what I do: why I am so focused on metrology. But maybe I can explain it a little here (warning: rambling ahead! I have been reading books and may come over as slightly lyrical). Read more »


Does it matter part 4: flatfield correction on a Bruker HiStar wire detector

Detector deviation from the azimuthal mean; a first approximation at obtaining a flatfield image. Color scale clipped to -0.5, 0.5 (-50% and 50% deviation, respectively).

See the previous posts in this series here: Part 1, Part 2 and Part 3

Very recently, Bruker upgraded their SAXS instrument in our building. This is a typical 3-pinhole 2D SAXS system that was largely designed by J. S. Pedersen in Aarhus a decade or so ago. This particular version was at NIMS in the Quantum Beam Unit / Neutron Scattering Group, and was using chromium radiation (a very low energy radiation). Now that its source has been upgraded to my favourite molybdenum type (a high energy radiation), it is time to check all of its corrections once more, starting with the flatfield. Read more »


Fancy background subtraction: an initial look

Schematic overview of the considerations of the fancy background subtraction.

As indicated last week, some spare time has been spent trying to re-derive a correction for separating sample container scattering from the sample itself. Normally, a simple background subtraction suffices, but for those who want to go the extra mile (and in particular for those working with strongly absorbing sample containers and samples), you need something a bit more fancy. Read more »


Cutting-room clippings

For today’s post, I had a few things planned, but haven’t been able to work anything out yet. So I’ll talk a little about these bits and pieces: Upcoming conferences and meetings, some future instrumentation plans, and a little about the Fancy Background Subtraction Read more »


Data correction and reduction code functional

Some corrected data

Before I get started, let me just highlight the new small-angle scattering issue of J. Appl. Cryst. which has come out a few days ago. My contribution was unfortunately not accepted (and I haven’t worked much on it since due to rejection depression), but the journal is still very much worth a read!

Now for the main topic of today’s post. Regular readers will know that I have started implementing the “Everything SAXS”-set of data corrections in the Python language. Having worked on it in between other tasks (evident from the commits to the repository), it is now in such a state that it can do enough to do basic correction and reductions, with uncertainty propagation. At the moment, it is not very user-friendly (no GUI, for example), but it is modular and flexible, with an easy syntax. The correction modules are straightforward and easy to read and write, and Pythonistas will be able to dig right in and use it to do the necessary corrections. Here’s the details: Read more »


Trouble in Paradise? Internal diffraction in PILATUS-like detectors

Internal detection surface diffraction effects leading to a reduction of detected counts (black lines on the real image, over which about 10% fewer counts were detected than the surrounding pixels). Image on the right shows the calculated pattern for the chosen energy. Energy used: 8285 eV, Reflection indices detected: (117). Image courtesy of Christian Gollwitzer at PTB.

A great many of the data correction issues in small-angle scattering can be resolved by trading a kidney for a PILATUS detector [1] (or similar [2]). These are detectors using a single crystal sensor as detection surface, and have extremely low noise, low distortion, high dynamic range and single photon sensing capabilities. However, as investigated by Gollwitzer and Krumrey (arXiv version here), this type of detector we so adore for its good detection characteristics may need a bit more data adjustment than expected. Read more »