Design of single-shot time/energy- resolved XES spectrometer for the LCLS Katherine Spoth Dennis Nordlund, mentor August 11, 2011

Surface Chemistry 2

X-ray Emission Process (XES) 1s 2s 2p 1s 2s 2p 1s 2s 2p Energy Ground StateExcitationDecay 3

Resonant X-ray Emission (RIXS) 1s 2s 2p 1s 2s 2p 1s 2s 2p Energy Ground StateExcitationDecay 4

Basic Spectrometer Design 5

Non-Dispersive Imaging: Time Resolved XES 6

Non-Dispersive Imaging: Variable-Energy RIXS 7

Design Goals Optimize for study of Oxygen at 520 eV Best energy resolution (grating) of 0.25 eV – Also allow high-throughput resolution up to 1 eV for certain applications Imaging resolution (mirror): – Time-resolved XES: 10 um on source, corresponding to 30 fs – Variable-energy RIXS: 200 um on source, corresponding to 0.25 eV 8

Ray tracing - SHADOW Simulated spectrometer’s performance: – Mirror position, shape, incidence angle – Illumination distance of mirror, grating

Final Design 10

Results of Ray-Tracing 1:10 imaging, ideal elliptical shape are best choices for non-dispersive focusing mirror Determine maximum length on grating, mirror that can be illuminated keeping required resolution Large source sizes (sample footprints) are not imaged well 11

Monochromator Dispersion on sample for θ=12° LCLS SXR: 1 eV/mm SSRL BL 13: 10 eV/mm Ideally, want higher eV/mm at smaller angle θ 12

Conclusions This design is capable of: – Time-resolved XES – Variable-energy RIXS SXR at normal incidence (bulk measurements) BL 13 SSRL, grazing incidence (allows surface chemistry experiments) To observe surface reactions using RIXS at LCLS SXR, need modifications to monochromator or new BL at LCLS-II 13

Acknowledgements 14 My mentor, Dennis Nordlund SLAC and the DOE for supporting the SULI program The staff at SLAC which make this program possible My fellow interns!