LIGO Document G1801310-v1

Experimental Search for Avalanches of Entangled Dislocations as a Source of Dissipation and Mechanical Noise

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Recent measurements using highly sensitive instruments have shown increased dissipation and the appearance of random low-frequency noise in metal flexures. These effects have been attributed to avalanches of entangled dislocations, a phenomenon believed to be controlled by self-organized criticality (SOC) statistics. This experiment is attempting to detect these subtle effects using a variation on the Kimball-Lovell 1927 rotating beam experiment that was used to measure the loss angle of materials above 1 Hz. A frequency range of 1 Hz and below was chosen to study the effects of dislocation entanglement. The loss angle of a piano wire has been measured with milli-radian precision and the feasibility of making future measurements of loss angle with micro-radian precision has been demonstrated at arbitrarily low rotation speeds. If dislocation avalanches are a source of the 1/f noise in these flexures (where f is the event frequency), it is expected that this experiment will be capable of detecting the expected deviations in loss angle.
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