Tight focusing with very small f-numbers is necessary to achieve the highest at-focus ***,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We des...
Tight focusing with very small f-numbers is necessary to achieve the highest at-focus ***,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~1022W/cm2laser±plasma *** used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel *** discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy (i.e.,around half of the short Rayleigh length)and show that several diagnostics (in particular,3ωreflection and on-axis hard X-rays) can ensure this *** demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity *** approach is relatively fast (it requires 10±20 laser shots) and does not rely on the coincidence of low-power and high-power focal planes.
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