Investigation of mechanical properties of cryogenically treated music wire
It has been reported that treating music wire (high carbon steel wire) by cooling to cryogenic temperatures can enhance its mechanical properties with particular reference to those properties important for musical performance. We use such wire for suspending many of the optics in Advanced LIGO, the upgrade to LIGO—the Laser Interferometric Gravitational-Wave Observatory. Two properties that particularly interest us are mechanical loss and breaking strength. A decrease in mechanical loss would directly reduce the thermal noise associated with the suspension, thus enhancing the noise performance of mirror suspensions within the detector. An increase in strength could allow thinner wire to be safely used, which would enhance the dilution factor of the suspension, again leading to lower suspension thermal noise. In this article, we describe the results of an investigation into some of the mechanical properties of music wire, comparing untreated wire with the same wire which has been cryogenically treated. For the samples we studied, we conclude that there is no significant difference in the properties of interest for application in gravitational wave detectors.
© 2015 AIP Publishing LLC. Received 11 June 2015; accepted 4 August 2015; published online 21 August 2015. The authors would like to thank Andrew Hoff for his assistance in using the Instron strength testing machine in the Keck Laboratories at Caltech, and Ben Abbott for his assistance in straightening samples of wire and his general advice on metallurgy. We would like to thank Jeff Lewis for his assistance in procuring the cryogenically treated wire samples. We would like to thank Peter Saulson and James Hough for their helpful discussions on aspects of this work. We would also like to thank our colleagues in the LIGO Scientific Collaboration for their interest in this work. We are grateful for the financial support provided by the National Science Foundation. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation and operated under Cooperative Agreement No. PHY-0757058. Advanced LIGO was built under Award No. PHY-0823459.
Published - 1.4928610.pdf
Submitted - 1506.03778.pdf