X23A2 Beamline Evaluation: Energy Calibration

Calibration over an extended energy range

At X23A2, calibration of our old-fashioned monochromator is done by measuring three absorption edges over some energy range, recording the measured energies, and fitting a two-parameter equation to those results. The parameters are the offset angle of the mono and the Bragg-normal separation of the crystals. We typically refine those two parameters differently above and below 10 keV. The following table shows measured edge energy positions for the mono calibrated in the low-energy range. Specifically, I used the Cr, Fe, and Zn edges to refine parameter values of 0.005138 deg. offset angle and 1.96716 inch separation. (Yes, those are the units we use!)

I then measured each foil from V to Ge without recalibrating the mono. Thus the E₀ values reported in the second column are as found using the initial calibration to the three foils.

Related files

• Athena project file with these data

• Spreadsheet used to generate that table

Scan to scan variation in edge energy

Another useful measure of calibration is the shift in edge energy for a sequence of scans. The following graphic shows the variation over the course of 30 scans in the edge energy position of a vanadium foil. The value for the energy shift was determined using Athena automated alignment algorithm with the first scan as the standard (and thus with a shift of 0). The refill happened during scan #008 -- the beamline software restarted the scan sequence a while after shutter control was restored.

Related files

• Athena project file with these data

• Spreadsheet used to generate that table

I need to add similar pictures for other energies, say Cu and Ag.