The Advanced Photon Source Upgrade project has employed the use of high heat load dual mirror systems in the new feature beamlines being built. Due to the shallow operating angles of the mirrors at a particular beamline, XPCS, the two mirrors needed to be approximately 2.5 m apart to create a distinct offset. Two separate mirror tanks are used for this system. However, it is unclear if the vibrational performance of these tanks would be better if they were both mounted on one large plinth or

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... h mounted on a small plinth. Using accelerometers at the installation location, the floor vibrations were measured. The resulting frequency response function was then imported into a Finite Element Analysis software to generate a harmonic response analysis. The two different plinth schemes were modeled and the floor vibration was introduced as an excitation to the analysis. The relative pitch angle (THETA Y) between the mirrors was evaluated as well as the relative gap between the mirrors (XMAG). Results showed that a single plinth reduces the relative XMAG (RMS) compared to two plinths by approximately 25%. However, the relative THETA Y (RMS), which is arguably more critical, is significantly lower by approximately 99.7% in two plinths when compared to a single plinth. Therefore, it is more effective to use two separate plinths over a longer distance as opposed to a single longer granite plinth.