Flash spectrographs for FEL diagnostics and XANES measurements at LCLS

This proposal aims to continue the preliminary experiments using SPPS, which demonstrated the feasibility of preforming XANES experiments on the femtosecond time scale. It also has the potential to provide a shot-by-shot measurement of the beam spectral profile. The instrument consists of a simple dispersive spectrometer coupled to an integrating position-sensitive detector. Experiments at NSLS and SPPS verified the operation of the spectrometer using imaging plates and a commercial CCD detector respectively. With the low intensities available from SPPS, several hundred pulses needed to be accumulated for a useable spectrum. With LCLS, a single shot should be sufficient. At 100Hz operation, 1 second should give excellent spectra, even for rather dilute systems, and would allow subtle spectral modifications to be recorded. To fully realize the instrument's potential, several enhancements need to be made, described below.