Direct-drive fusion implosion experiments using the 60-beam OMEGA Laser System require ~1% rms uniformity on target. Measurements from laser diagnostics indicate that beam-to-beam power variation has been sufficiently reduced such that the uniformity nearly meets this requirement; however, experimental results suggest otherwise. To better understand this discrepancy, a full-beam-in-tank diagnostic has been developed to characterize the on-shot, full-energy focal spot of a single beam inside the target chamber using a small sample of the beam from the final optic assembly. In this paper, we describe the diagnostic and present the results of commissioning experiments.

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L. J. Waxer, K. A. Bauer, E. C. Cost, M. Heimbueger, J. H. Kelly, V. Kobilansky, S. F. B. Morse, D. Nelson, R. Peck, R. Rinefierd, S. Sampat, M. J. Shoup III, D. Weiner, G. Weselak, and J. Zou, "In-tank, on-shot characterization of the OMEGA laser system focal spot," Proc. SPIE 10898, High Power Lasers for Fusion Research V, 108980F (Presented at SPIE LASE: February 06, 2019; Published: 4 March 2019); https://doi.org/10.1117/12.2506792.