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Multipulse Laser-Induced Failure Prediction for Mo Metal Mirrors

出版	ASTM International, 1991
URL	http://books.google.com.hk/books?id=RWZ4zgEACAAJ&hl=&source=gbs_api

註釋In combination with known thermomechanical fatigue data for Mo, we have applied the Transient Photothermal Deflection (TPD) technique to develop a model for the N-on-1 damage of Mo mirrors to predict their multipulse lifetimes. In laser-damage experiments to verify the model, mechanically polished Mo mirrors were irradiated with 10 ns Nd:YAG laser pulses at 1064 nm at a 10 Hz rep rate. In the TPD experiments, the approximately 600 ?m diameter Nd/3YAG laser spot was probed off axis by a smaller HeNe laser beam whose deflection was detected by a fast bicell photodetector and amplifier. Digitized photodetector waveforms indicated that the surface angular deflection could be converted into surface displacement. In addition, thermal modelling of the vertical heat distribution enabled the peak surface-deflection signal to be converted into peak surface temperature. The thermomechanical model was verified by both the experimental and model results.