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A detailed structural model of the TAB that includes the target positioner, target chamber, turning mirrors, and diagnostics, has been used for stability evaluations. Finite element analysis has been used to evaluate the design of the TAB and optical support structures. Thermal stability will be accomplished by using high thermal-mass concrete structures, conditioned air flow, and a reduction of heat sources. To satisfy the error budget requirements, vibrational stability will be achieved through a combination of facility design, optic support structure design, and passive damping. A positioning error budget has been developed for the NIF project for use in the design and evaluation of structures which support optical elements. Sources that influence optic stability are structural excitations, such as ambient and wind induced vibrations, and thermal transients, such as diurnal and HVAC temperature changes. This paper summarizes the stability analyses that were performed in support of the TAB and optical system design. In order to satisfy the engineering system requirement for optical system positioning (stability on target), the more » TAB must provide a stable platform for optical elements before and during a shot. Within the TAB, the 192 independent laser beams of the NIF laser system are required to be accurately positioned. The reinforced concrete target building houses the target chamber, target positioner, turning mirrors, final optics assemblies, and diagnostics, while the steel switchyard space frames support turning mirrors and diagnostic equipment. The Target Area Building (TAB) of the National Ignition Facility (NIF) is 300 feet long, 100 feet wide, and 100 feet tall and is comprised of a cylindrical target building and two switchyard space frames.