Improved technique for measuring high pendulum Q-factors

• Published in: Measurement science & technology 2002-02, Vol.13 (2), p.218-221
• Main Authors: Paget, Darren, Winterflood, John, Ju, Li, Blair, David
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Mechanical instruments, equipment and techniques; Physics
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/13/2/312

The measurement of Q-factors of test mass suspensions is important in determining the noise floor of gravitational wave interferometers. In laser interferometer gravity wave detectors, the losses in the pendulum suspension for the test mass mirrors are a significant source of displacement noise. To measure a high pendulum Q-factor it is necessary for the pendulum to be suspended from a very rigid base to reduce recoil losses. Usually, the massive support is directly connected to the ground and is thus affected particularly by seismic motion. By correlating the appropriate component of seismic data with a long-term amplitude ring-down curve, shows that it is possible to remove the variation in amplitude due to seismic excitation. Removal of the seismic signal allows a faster, more accurate determination of pendulum Q-factors. In addition, the technique could allow the Q-factor to be determined without large-amplitude excitation. (Original abstract - amended)