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A reflective image-rotating periscope for spatially resolved Thomson-scattering experiments on OMEGA

A reflective image rotating periscope has been deployed on the Thomson-scattering system at the Laboratory for Laser Energetics, enabling the capability to make spatially resolved measurements of plasma conditions using either the 2ω (527-nm) or 4ω (263-nm) probe beam. The spectral content of ion-acoustic and electron plasma wave Thomson-scattering features are analyzed along the probe beam's axis of propagation using a pair of imaging Czerny-Turner spectrometers. A method for calculating image rotation was applied to design a translating periscope mirror assembly that provides fine adjustment of the image orientation at the spectrometer input plane. Spectrally dispersed Thomson-scattering signals are recorded using time-gated intensified charge-coupled–device cameras. Spectral resolution of up to 0.03 nm (0.2 nm) is achieved using a 1-m (0.3-m) spectrometer, allowing for simultaneous measurements of the ion-acoustic and electron plasma wave features. The optical system's 20-μm imaging resolution provides excellent noise rejection and spatial definition of the Thomson-scattering volume.