Speaker
Description
Thermal noise from suspension systems is one of the fundamental noise sources limiting the sensitivity of gravitational-wave detectors. The mechanical loss of suspension fibers supporting the test masses can contribute significantly to suspension thermal noise, particularly in cryogenic detectors such as KAGRA, where the mirrors are cooled through the suspension fibers. Accurate measurements of the mechanical quality factor (Q) of suspension fibers are therefore important for evaluating and improving detector performance.
Conventional Q measurement systems often use parallel suspensions where rotational motion is not fully isolated, while two-point suspensions isolate rotation only for a single rotational degree of freedom.
In this work, we investigate a method for high-precision measurements of fiber Q using a non-parallel trifilar suspension. The suspension geometry can be tuned so that the vibration modes of the suspended body align with the rotational degrees of freedom in both orthogonal directions. This configuration suppresses dissipation originating from the support structure and enables more accurate measurements of the intrinsic mechanical loss of the fiber.
The suspension geometry has been designed based on theoretical analysis, and an experimental apparatus has been constructed to perform ringdown measurements. Experimental studies are currently underway. The design of the system and the measurement strategy will be presented, and preliminary experimental results will be discussed if available.