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LLE Stability Monitoring


  • Linh Vu
  • Owen Wacha
  • Jay Yoo
  • Makarii Yurkiv




Micrometer-scale laser drift in the Omega-60 laser system at the Laboratory for Laser Energetics (LLE) may be hindering their fusion technology research. The prevailing drift hypothesis is that stray thermal sources intermittently heating the steel beams of the transport mirror support structure cause the mirrors to tilt. Two controlled heating experiments were conducted to test the hypothesis, one on a freely damped table and one involving a large steel beam. Experiments and associated finite element analysis (FEA) simulations yielded micrometer-scale drifts when subjected to thermal conditions like those seen at LLE. The experimental drift value was computed to be 6.018 mm while the FEA model displayed 2.002 mm of drift.
Simulation of the transport mirror structure inspired by thermal data shows interesting drift results as well. Analysis of drift data collected by LLE inspired other potential drift sources to be investigated in the future. The thermal structural analysis of the transport mirror structure at LLE demonstrated drifts due to rotations of the mirrors. The drift value computed from the thermal FEA was 16.917μm with 0.98% error compared to the drift value of mirror 30 from the ultraviolet laser stability test results, 17.092μm. However, the drift values of all the other mirrors had over 33% error compared to the LLE’s stability data. This indicates that there are more sources of heat that was not captured or there are other possible sources that can affect the drifting behavior of the laser, which will be discussed later in the document.

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