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Figure 3
Influence of the collimator/detector alignment. The collimator with an aperture of 2 mm horizontally and 2 mm vertically is placed at a distance of 11 m from the middle of the straight section. With a properly adjusted collimator a sharp peak with quasi-monochromatic γ radiation of 5% bandwidth and a distinct high-energy cut-off is obtained (black spectrum). On the other hand, the broad peak is obtained after displacement of the collimator/detector unit by 2 mm in the vertical direction (gray spectrum). Now only few photons with maximum energy can reach the detector, and the signal at the cut-off energy drops significantly. One can also see that the shape of the signal is a good indicator for proper alignment of the collimator/detector in the forward direction of the electron beam. Nevertheless, the evaluation of the two signals yields electron energies of 796.88 (3) and 796.85 (9) MeV for the properly aligned collimator/detector and shifted collimator/detector, respectively.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 5| Part 3| May 1998| Pages 392-394
https://doi.org/10.1107/S090904959701532X
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