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

Abstract

A reflective image rotating periscope has been deployedon the Thomson-scattering system at the Laboratory for Laser Energetics,enabling the capability to make spatially resolved measurements of plasmaconditions using either the 2ω (527-nm) or 4ω (263-nm) probe beam. Thespectral content of ion-acoustic and electron plasma wave Thomson-scatteringfeatures are analyzed along the probe beam's axis of propagation using apair of imaging Czerny-Turner spectrometers. A method for calculating imagerotation was applied to design a translating periscope mirror assembly thatprovides fine adjustment of the image orientation at the spectrometer inputplane. Spectrally dispersed Thomson-scattering signals are recorded usingtime-gated intensified charge-coupled–device cameras. Spectral resolutionof 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 electronplasma wave features. The optical system's 20-μm imaging resolution providesexcellent noise rejection and spatial definition of the Thomson-scatteringvolume.