Alignment of diffraction features in the Optical Thomson Scattering Laser at the National ignition Facility

Abdul A. S. Awwal

doi:10.1117/12.2588507

5 March 2021 Alignment of diffraction features in the Optical Thomson Scattering Laser at the National ignition Facility

Abdul A. S. Awwal

Author Affiliations +

Proceedings Volume 11666, High Power Lasers for Fusion Research VI; 116660D (2021) https://doi.org/10.1117/12.2588507
Event: SPIE LASE, 2021, Online Only

Abstract

The world’s largest and most energetic laser facility, the National Ignition Facility (NIF) is dedicated to understanding inertial confinement fusion by irradiating a mm scale fusion target using 192 precisely aligned laser beams. The optical Thompson scattering (OTS) laser is being commissioned to understand the target implosion physics, especially for under-dense plasma conditions. The OTS will enable the diagnosis of the plasma performance leading to better control of the symmetry and efficiency of target implosion. Both 3w and 5w probe beams can be selectively chosen for diagnosing various plasma densities. Just as the NIF laser, the OTS system is aligned using several closed loop controls. CCD images of the laser beams are analyzed using automatic alignment image processing algorithm to provide beam position and motorized mirrors are mobilized to steer those beams to the desired path and location. One such control loop of the OTS uses a pair of far field diffraction pattern generated by a spherical object connected to a shaft. During the control loop alignment movements, the diffraction rings may be partially missing due to obstruction by the aperture. This paper describes the systematic process of algorithm development for detection of the diffraction rings and the necessary modifications as the requirements change. It describes the template design and algorithm for position detection from such images under challenging illumination and obstructive conditions. Among other novelties of this work is the use of a single computational neuron, inspired by a bipolar binary associative memory, employed to evaluate the quality and uncertainty of the location measurement, and avoid false detection.

Conference Presentation

Citation Download Citation

Abdul A. S. Awwal "Alignment of diffraction features in the Optical Thomson Scattering Laser at the National ignition Facility", Proc. SPIE 11666, High Power Lasers for Fusion Research VI, 116660D (5 March 2021); https://doi.org/10.1117/12.2588507

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