Density functional theory is used to investigate Eu, Er, and Tm rare earth (RE) impurities in GaN, paying particular attention to their structure, energetics, and electronic properties. The most stable site is when the RE is located at a Ga substitutional site but none of the defects possess deep energy levels. RE–VN close pairs are stable at temperatures greater than 1000 °C for 1 at. % RE doping and possess shallow levels possibly exciting intra-f luminescence in the visible. RE–VGa and RE-interstitial defects possess deep levels which exclude them as sources for visible RE-related luminescence.
We have undertaken a measurement campaign to determine the repeatability of the prompt flashlamp-induced wavefront aberration on beamlines at the National Ignition Facility (NIF) and determine the extent to which shot-to-shot variations in this aberration may degrade the performance of a proposed adaptive optics system for the short-pulse Advanced Radiographic Capability beamline on NIF. In this paper we will describe the unique NIF configuration that was required to make this measurement, present the results of the experiment, and discuss the implications of these results for the adaptive optics system design.
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