Discussion Group B1
Nomadic utopia: towards a better understanding of all instrumental artifacts
- Charles Dewhurst (ILL)
- Brian Pauw (NIMS)
- Presentation by leader: Nomadic utopia: towards a better understanding of all instrumental artifacts - Charles Dewhurst
Discussion on Data Corrections (N=neutrons, X=X-rays)
There are a lot of stories on what not to do. I would be nice to put some of these stories online. Some advice:
N Don’t stagger detector tubes, the partial shielding is nontrivial to correct for (Ken Littrell) N recalibrate position every so often to compensate for stretch and offset caused by charge division electronics instability. N Coincidence detectors are difficult to correct for (with the compensation dome on top) N Boron technology detectors will have their own issues, corrections and complications.
X Not able to measure direct beam on the same detector. Can be resolved by: - partially transparent beamstop, - attennuator as beamstop - pin-diodes (should be placed close to sample to determine transmission according to Richard Heenan’s definiton). X Difficult to measure flat field, can be done by: - Glassy carbon, - moving detector across the beam - Careful when measuring: only flat field should be determined, not the other corrections!
- Add resolution in SAXS and SANS, both lab and facility - Minimise air in all techniques! - how to deal with resolution? - traceability of corrections are needed (provenance) - calibration sample should be available at facilities - much more information needs to be available everywhere (make a list?) - Desmear on lab-sources - How far can you correct with background correction? N TOF choppers can be a big source of background. N Shield around active elements (and put holes in the right place) N Cover aigrets with absorbing tubes N Recommended slit design: use B4C with sintered edge.