F. Khan, D. Crivelli, J.H. Kelly, A. Male
DLS, Oxfordshire, United Kingdom
Vibration in beamline optics can degrade the quality of experiments: the resulting movement of a mirror increases the x-ray beam position uncertainty, and introduces flux variations at the sample. This is normally dealt with by averaging data collection over longer periods of time, by slowing down the data acquisition rates, or by accepting lower quality / blurred images. With the development of faster camera technology and smaller beam sizes in next generation synchrotron upgrades, older optics designs can become less suitable, but still very expensive to redesign. Mechanically, mirror actuation systems need to be a balance between repeatability of motion and stability. This normally leads to designs that are ’soft’ and have resonant modes at a relatively low frequency, which can be easily excited by external disturbances such as ground vibration and local noise. In ultra-high vacuum applications the damping is naturally very low, and the amplification of vibration at resonance tends to be very high. At Diamond we designed a process for passively damping beamline mirror optics. First, we analyse the mirror’s vibration modes using experimental modal analysis; we then determine the tuned mass damper parameters using mathematical and dynamic models. Finally, we design a flexure-based metal tuned mass damper which relies on eddy current damping through magnets and a conductor plate. The tuned mass damper can be retrofitted to existing optics using a clamping system that requires no modification to the existing system. In this conference paper we show a case study on a mirror optic on Diamond Light Source’s small molecule single crystal diffraction beamline, I19.
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