Classical and holographic interferometry systems combined to document inertial fusion experiments

Inertial fusion (IF) employs laser beams to implode spherical shells containing deuterium and tritium. Freezing the DTfuel in a uniform layer within the container aids in achieving the densities required for fusion. A documentation system has been developed which is used to record both classical interferograms of solid IF fuel layers within the container and then holographic interferograms of plasma as the container implodes. This optical system has the advantages of visible and UV utility, 2–4-µm resolution, and a low space requirement. Both systems share a catadioptric objective lens and a refractive relay lens. The visible classical interferometric beam and the UV pulsed holographic probe follow different off-axis paths within the object cone of the lenses. While the solid layer is being formed, the beam is diverted to a shearing cube interferometer using a lens-mirror assembly on a sliding stage. This assembly then slides out of the way before the implosion to admit the UV probe to the holographic camera, which records four holographic interferograms of the imploding plasma separated in time by 40–400 ps. The two operational modes, shearing interferometer and holographic, are serial; switching from one to the other requires only seconds.