Operating the beamline

Setting the photon energy resolution

Photon energy resolution can be set by opening and closing the beamline entrance and exit slits. Typical setting is 100 μm entrance and 200 μm exit slit apertures. (We use the exit slit aperture to be 2 × entrance slit aperture.)

The slit apertures are set by corresponding micrometers using the following tables. The equation to estimate the experimental photon energy resolution is listed for each slit combination. The default setting is bold.

entrance slit aperture entrance slit micrometer 35 μm 16.65 mm 50 μm 16.8 mm 100 μm 17.3 mm 150 μm 17.8 mm 200 μm 18.3 mm 250 μm 18.8 mm 300 μm 19.3 mm

exit slit aperture exit slit micrometer 70 μm 14.1 mm 100 μm 14.4 mm 200 μm 15.4 mm 300 μm 16.4 mm 400 μm 17.4 mm 500 μm 18.4 mm 600 μm 19.4 mm

photon energy resolution 0.000010 × (hν)1.5 0.000015 × (hν)1.5 0.000030 × (hν)1.5 0.000045 × (hν)1.5 0.000060 × (hν)1.5 0.000075 × (hν)1.5 0.000090 × (hν)1.5

Of course the resolution setting is also influencing the photon flux. However, the usual setting 100 μm entrance and 200 μm exit slit seems to be a good compromise, as at low photon energies the flux is usually sufficient and at high photon energies opening the slits would cause too bad resolution.

If for your measurements you decide to change the slit setting do not forget to write it down into the labbook, inform you colleagues about this change and reset everything back afterwards.