High-Resolution Effective K Measurements Using Spontaneous Undulator Radiation. Bingxin Yang Advanced Photon Source Argonne National Lab. Two Essential Elements for Far-Field Measurements. (Adapted from x-ray diagnostics planning meeting, Feb. 2004, SLAC) Roll away undulators
High-Resolution Effective K MeasurementsUsing Spontaneous Undulator Radiation
Advanced Photon Source
Argonne National Lab
(Adapted from x-ray diagnostics planning meeting, Feb. 2004, SLAC)
Spontaneous radiation is most useful when background is clean, with each undulator rolled in individually.
Relative measurements of undulator effective K using far-field spontaneous radiation (8 keV, 40 m to 60 m from undulator exit). Bonus: Wide bandwidth monochromator for z-dependent x-ray intensity measurement (DE/E ~ 0.1%).
Small effect on 70-eV wide edge!
Impact of Electron Bunch Charge Fluctuation
Most damaging instrument effect!
Intensity distribution depends strongly on photon energy!
An acceptable spectrum needs integration of 256 – 1024
shots, resulting scan time = 7 – 18 minutes @ 120 Hz.
Use one mono to pick the same x-ray energy
Use two detectors to detect the x-ray flux separately
Use differential electronics to get the difference in flux
DK/K = 1.5 10-4
Example: Average improves resolution for DK/K = 10-5
The signal is statistically significant in resolving undulators with
DK/K = 3 10-6
Is it still meaningful?
Can we detect minor radiation damage?