Measurements of nonlinear harmonic generation at the Advanced Photon Source's SASE FEL

Observations of z-dependent microbunching harmonic intensities using COTR in a SASE FEL

“…The harmonic aspects are important not only as a test of our understanding of the process, but also because their existence offers a way to generate FEL radiation at shorter wavelengths without increasing the electron beam acceleration capability. The observed growth of the SASE fundamental and second harmonic has been described previously [6]. In this paper we focus on the complementary information on the microbunching harmonic components as revealed through coherent optical transition radiation (COTR) techniques.…”

“…At the time of these experiments, four of the imaging stations (2,4,6,8) for the second 45° pick off mirror had been upgraded to detect UV radiation down to 200 nm, the others remained as visible-light-only setups until the summer of 2001. The multiple filter wheels before the CCD camera were employed to position two solar blind (SB) bandpass filters that attenuate strongly any radiation longer than 360 nm and shorter than 225 nm.…”

“…The interest in nonlinear generation of harmonics [1][2][3][4] in a self-amplified spontaneous emission (SASE) free-electron laser (FEL) continues to grow as experimental results are reported [5,6]. The harmonic aspects are important not only as a test of our understanding of the process, but also because their existence offers a way to generate FEL radiation at shorter wavelengths without increasing the electron beam acceleration capability.…”

Much Ado about Microbunching: Coherent Bunching in High Brightness Electron Beams

“…However, due to finite electron beam size, betatron motion and radiation angle, second harmonic radiation may exist at non-negligible levels [64,68,69], and has also been observed experimentally [66,67,70].…”

Time-resolved measurement of a self-amplified free-electron laser

“…Recent experiments have demonstrated saturation of such SASE FELs [5][6][7] and their capability of achieving shorter and tunable wavelengths by direct amplification [6] as well as harmonic generations [7,8].…”