Estimated Temperature Dependence of the Non-Magnetic, Blade-spring Damper (NMBD) for the Quad UIM

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Abstract:: The purpose of the Non-Magnetic, Blade-spring Damper (NMBD), D1400298, is to damp the first internal mode of the blade-spring of the Upper Intermediate Mass (UIM) of the quadruple pendulum suspension. The assembly, tuning (for damping) and testing of the NMBDs is performed in a lab room at higher temperature (65 - 75F) than the operational temperature of ~65F. The NMBD design review committee asked if the difference in temperature might make a significant change to the damping of the first blade-spring resonance (i.e. would it still meet requirements).
The NMBD employs a UHV-compatible formulation for Flourel (a 3M product). We don't have temperature dependence data for the complex modulus of Flourel. Flourel is similar to Viton (a Dupont product). In order to estimate the temperature sensitivity of the effective damping of this dynamic vibration absorber, we use the complex modulus fit to Viton reported in T1600097. Using the experimental results reported in T1600046, and the dynamic vibration absorber formulation in T080194, this Mathematica notebook estimates the effort of assembling, tuning and testing at 75F and employing operationally at 65F. The end result is a 14% increase in Q. This is considered acceptable relative to the requirements. It is also worth noting that the maximum likely assembly temperature was only 70F, although no record of temperature was kept. So the likely variation in Q is likely only ~7%.

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LIGO Document T1600098-v1