Abstract
The linac coherent light source (LCLS) is a self-amplified spontaneous emission (SASE) free-electron laser (FEL) operating at fundamental photon energies from 0.5 to 10 keV. Characterization of the higher harmonics present in the FEL beam is important to users, for whom harder x rays can either extend the useful operating wavelength range or increase experimental backgrounds. We present measurements of the power in both the second and third harmonics, and compare the results to expectations from simulations. We also present studies of the transport of harmonics to the users, and the harmonic power as a function of electron beam quality.
Highlights
The linac coherent light source (LCLS) started user commissioning in October of 2009, producing fundamental free-electron laser (FEL) radiation with photon energies ranging from 550 to 10 keV [1]
Radiation at the fundamental wavelength of the FEL dominates in the experimental beam lines, but non-negligible levels of radiation at higher harmonics are present
We present second and third harmonic measurements for LCLS (Table IV)
Summary
The linac coherent light source (LCLS) started user commissioning in October of 2009, producing fundamental free-electron laser (FEL) radiation with photon energies ranging from 550 to 10 keV [1]. Radiation at the fundamental wavelength of the FEL dominates in the experimental beam lines, but non-negligible levels of radiation at higher harmonics are present. These harmonics may be desirable as a source of harder x rays, but may contribute backgrounds to user experiments at the fundamental wavelength. Due to finite electron beam size, betatron motion, and radiation angle, second harmonic radiation may exist at non-negligible levels [3,7,8], and has been observed experimentally at LEUTL, VISA, and FLASH [5,6,9]. We compare the results to simulations and study the effect of electron beam quality on the harmonic power
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