Abstract: A pressure differential containment structure, including a vacuum chamber and a pressure vessel, for operation in the pressure range of 1 to 2 atmospheres of pressure differential, using relatively thin wall material and incorporating strengthening members by folding or forming the walls of the containment structure itself. The structural configuration of the preferred embodiment is of rectilinear geometry with four lateral walls and two end walls. Each lateral wall component is preferably fabricated from at least one sheet, such as stainless steel, aluminum, or synthetic material including polymers and composites, to comprise reinforcing ribs or corrugations transverse to the longitudinal direction of the wall and include transverse flanges at each end.