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(a) Spectral distribution measured for α = α0/25 and for various bunch currents. The projected version at the bottom shows two thresholds: the appearance of CSR for I bunch = 55μA (threshold 1) and the appearance of strong instabilities for I bunch = 95μA (threshold 2). (b) Evolution of the fluctuation frequencies with the current. The CSR signal at around 1 THz fluctuates at a frequency in the kHz range, resulting in localized artifacts in the spectra. The two thresholds can again be observed in the projected 2D plot: the appearance of the artifacts (threshold 1) and the development of bunch instabilities (threshold 2).
Top: intensity profile of the CSR produced with a momentum compaction factor of α0/25 and 416 bunches (solid line), compared to incoherent synchrotron radiation (ISR) obtained with α0 (dashed line). The intensity was normalized for a current per bunch of 1 mA. Bottom: signal-to-noise measured by dividing two successive spectra through an empty 85 cm gas cell (10 scans, 1 h, 10−3 cm−1 resolution) with the same conditions as described above for ISR and CSR.
Schematic diagram of the high-resolution spectroscopic station of AILES beamline. The first beamsplitter divides the incident beam into a reflected reference beam (detected by bolometer 1) and a transmitted beam (modulated by the interferometer, then detected by bolometer 2) with R/T = 0.25 at 10 cm−1. The interferogram (temporal signal 2) includes an artifact, represented in black, which is also present on the reference signal (temporal signal 1).
Artifact correction on a 45 min absorbance spectrum of N2O at 0.001 cm−1 resolution. Both the reference spectrum and the sample spectrum were acquired with 416 bunches, 64 μA/bunch, and α0/25. Top: effect of the intensity fluctuations on the raw absorbance spectrum. Bottom: same spectrum after post-processing of the data. The gain in S/N reaches at least 25 locally.
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