Vibration stability of Orion laser facility

Abstract

In 2005 the UK Ministry of Defence awarded a contract for construction of the Orion laser facility at the Atomic Weapons Establishment (AWE). Orion delivers a power density of 1021 W/cm2 on a 5 μm target, making it a world-class facility for the study of high energy density physics. The ability to target to such high precision depends on the ‘stability’ of the building and internal structures with respect to thermal expansion and vibration. This paper concerns experimental activities supporting the prediction and evaluation of the minute vibrations against a ‘budget’ comprising the effects of all vibration sources, internal and external, and the sequence of experimental campaigns and signal evaluation that fed into this process. This involved a sequence of dynamics-based measurements of foundation pile stiffness, vibration propagation from both controlled and uncontrolled sources at stages during the construction and, finally, evaluation of vibration levels in the as-built facility due to internal machinery and the few external vibration sources passing through the sophisticated vibration barrier. The approach focused on time series of vibrations in the design phase and on the evaluation of statistical properties of displacement power spectral density functions.