A hard X-ray transmissive single-shot spectrometer for FEL sources

We report the design of a single-shot transmissive spectrometer for spectral measurements of the Linac Coherent Light Source (LCLS) operating in the mode of Self-Amplified Spontaneous Emission (SASE). The spectrometer was constructed using an ultra-thin and bent silicon single-crystal operating in the symmetric Bragg geometry. It was shown to be capable of recording the single-shot LCLS spectra while transmitting the majority of the incident flux to downstream experimental stations. The spectrometer used the Si (111) reflection for capturing the full SASE spectrum, and was then configured the high resolution mode using the Si (333) for resolving single spikes in the power spectral density.