For the LCLS-II instruments we are developing laser power meters as compact intensity monitors that can operate at soft and tender X-ray photon energies. There is a need to monitor the relative X-ray intensity at various locations along an X-ray FEL beamline in order to observe a possible decrease in the reflectivity of X-ray mirrors. In addition for experiments, it is valuable to know the absolute intensity at the sample. There are two types of laser power meters based on thermopile and pyroelectric sensors. The thermopile power meters measure an average temperature and are compatible with the high repetition rates of LCLS-II. Pyroelectric power meters provide a pulse-by-pulse response. Ultra-high vacuum compatibility is being tested by residual gas analysis. An in-house development beamtime is being conducted at the LCLS SXR instrument. Measurements using both thermopile and pyroelectric power meters will be conducted at a set of photon energies in the soft X-ray range. The detectors’ response will be compared with the gas monitor detector installed at the SXR instrument.
Philip A. Heimann, Stefan P. Moeller, Sergio Carbajo Garcia, Sanghoon Song, Yiping Feng, James M. Glownia, and David M. Fritz, "Laser power meters as x-ray intensity monitors for LCLS-II (Conference Presentation)," Proc. SPIE 10237, Advances in X-ray Free-Electron Lasers Instrumentation IV, 102370L (Presented at SPIE Optics + Optoelectronics: April 27, 2017; Published: 16 June 2017); https://doi.org/10.1117/12.2265929.5463398576001.
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