Experimental measurement of material fatigue properties of x-ray optics by using laser pulses

X. Cheng; J. Janowitz; S. Droste; L. Lee; E. F. Cunningham; J. Robinson; A. R. Fry; L. Zhang

doi:10.1117/12.2500294

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16 November 2018 Experimental measurement of material fatigue properties of x-ray optics by using laser pulses

X. Cheng; J. Janowitz; S. Droste; L. Lee; E. F. Cunningham; J. Robinson; A. R. Fry; L. Zhang

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Proceedings Volume 10805, Laser-Induced Damage in Optical Materials 2018: 50th Anniversary Conference; 108050J (2018) https://doi.org/10.1117/12.2500294
Event: SPIE Laser Damage, 2018, Boulder, Colorado, United States

Abstract

The x-ray free electron laser facility at SLAC National Accelerator Laboratory (named as LCLS) will be upgraded to LCLS-II in the near future. The high repetition rate light source makes the x-ray optics or components exposed to trillions of pulses over years of operation. Material fatigue properties of x-ray optics are essentially important for their lift-time prediction, optics optimization and opto-mechanical design. In this work, the fatigue properties of typical x-ray optics materials such as single-crystal silicon are experimentally measured by using laser pulses. The laser source can have an average power of 50 W at wavelength of 1.03 μm and repetition rate of 0.928 MHz with pulse duration of ~230 fs. The SHG crystal is used to generate 515 nm laser beam for the test to get an equivalent absorption length to soft x-rays. The maximum single-pulse energy is more than 16 μJ. The numbers of pulses that the optics can survive are measured for different pulse energies (fluences). The definition of the damage of x-ray optics is the significant reduction of reflectivity, which is premonitory of damage, and much more stringent than the ablation threshold.

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X. Cheng, J. Janowitz, S. Droste, L. Lee, E. F. Cunningham, J. Robinson, A. R. Fry, and L. Zhang "Experimental measurement of material fatigue properties of x-ray optics by using laser pulses", Proc. SPIE 10805, Laser-Induced Damage in Optical Materials 2018: 50th Anniversary Conference, 108050J (16 November 2018); https://doi.org/10.1117/12.2500294